8º Encuentro Franco-Español de Química y Física del Estado Sólido

8º Encuentro Franco-Español de Química y Física del Estado Sólido

8º Encuentro
Franco-Español de
Química y Física
del Estado Sólido
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CONFERENCIAS INVITADAS
CONFERÉNCES INVITÉES
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FROM IMPLANTS TO REGENERATIVE MEDICINE
María Vallet Regí
Dpto. Química Inorgánica y Bioinorgánica. Universidad Complutense de Madrid. Instituto de
Investigación Sanitaria Hospital 12 de Octubre i+12. Madrid, Spain
Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina (CIBERBBN), Madrid, Spain
[email protected]
The use of biomaterials in patients requiring repair or regenerate parts of their body is a subject
of great interest because of the solutions that can provide for a better quality of life.
However, technical issues and biological materials or cells are remarkable and, before applying
those biomaterials to patients, preclinical models should be analyzed to solve the limitations of cell
viability, mechanical strength (from the moment they are introduced into the body until they are
replaced by new tissue), and also the biological adaptation in the organism.
The manufacture of spare parts for the human body, by traditional methods or using tissue
engineering or cell therapy, are currently challenges are of great importance in biomedical
research. In this talk those ideas will be properly addressed.
Bioceramics with clinical applications.Edited by M.Vallet-Regí John Wiley and Sons Ltd. United Kingdon. 2014
Biomedical applications of mesoporous ceramics: drug delivery, smart materials and bone tissue engineering.Edited by
M.Vallet-Regí, M. Manzano, M. Colilla. CRC Press. 2013.
I. Izquierdo, A.J. Salinas, M. Vallet-Regí. Int. J. Appl. Glass Sci.. 4, 149-161 2013
S. Sánchez-Salcedo, M. Colilla, I. Izquierdo and M. Vallet-Regí J. Mater. Chem. B, 1, 1595-1606 2013.
M. Colilla, B. González, M. Vallet-Regí. Biomater. Sci. 1, 114–134 2013
A. Salinas, P. Esbrit, M. Vallet-Regí. Biomater. Sci. 1, 40-51 2013.
D. Arcos, M. Vallet-Regí. Acta Materialia. 61, 890-911 2013.
J. Simchenn, A. Baeza, D. Ruiz, M. Esplandiu, M. Vallet-Regí.. Small. 8(13), 2053-2059 2012.
M. Vallet-Regí, International Scholarly Research Network ISRN Materials Science, Volume 2012, Article ID 608548, 20
pages, doi:10.5402/2012/608548
A. Baeza, E. Guisasola, E. Ruiz-Hernández and M. Vallet-Regí. Chem. Mater. 24, 517-524 2012.
M. Manzano, M. Vallet-Regí. Prog. Solid State Ch. 40, 17-30 2012.
A. Baeza, E. Guisasola, E. Ruiz-Hernández and M. Vallet-Regí. Chem. Mater. 24, 517-524 2012.
M Vallet-Regí and E. Ruiz-Hernández. Adv. Mater. 23, 5177–5218. 2011
M. Vallet-Regí, M. Colilla and B. González. Chem. Soc. Rev. 70, 596-607 2011
E. Ruiz-Hernández, A. Baeza, M. Vallet-Regí. ACS Nano. 5 (2), 1259–1266 2011.
M. Vallet-Regí, E. Ruiz-Hernández, B. González, A. Baeza J. Biomater. Tissue. Eng. 1, 6-29 2011.
Materials Science and the development of
industrial applications, latest examples related to Rare Earths
P. MAESTRO1,* T. LE-MERCIER2,*, V. BUISSETTE2,*
1
2
SOLVAY, Scientific Director, 178 Ave Albert Schweitzer, 33600, Pessac, France
SOLVAY, Centre de Recherches, 52 Rue de la Haie-Coq, 93308, Aubervilliers, France
* Corresponding author: [email protected]
Rare earths industry is strongly dependent on its capacity to develop innovative applications
based on the very specific physical properties these elements exhibit, but also on the
differentiation that synthesis can bring, through the control of morphology, or reactivity of the
products.
As a matter of fact, solid state chemistry has played a key role in inventing new phases
capable of delivering specific physical and chemical properties, like in luminescent materials
catalysts systems, magnets, etc..
But in addition to the relationship between structure and property, real applications often
depend on the capacity of the product to deliver performance through the mastering, through
the synthesis capabilities, and the control of particle size, phases distribution, surface
reactivity, …
Examples will be given on how we have taken into account the importance of coupling
structural aspects to materials science and inorganic synthesis, for the development of, for
example, new phosphors with low terbium content, or new powders for fine polishing, by
combining benchmark synthesis capabilities and thorough understanding of the mechanisms
relating the composition of the products and its performance
Investigation of thermopower
in transition metal oxides
and related sulfides and selenides
Sylvie Hébert
Laboratoire CRISMAT, UMR6508 CNRS et ENSICAEN, 6 Bd du Maréchal Juin
14050 CAEN Cedex, France
*[email protected]
The Seebeck coefficient is a powerful probe of the electronic properties of a material as it is very
sensitive to the nature of carriers, to the band structure of the materials and to the different diffusion
processes and transport mechanisms. It can also be very sensitive to the presence of electronic
correlations, as for example in oxides [1]. Moreover, the Seebeck effect can be used to generate
electricity from waste heat, and has been more and more investigated in the recent years with the aim
of finding new efficient thermoelectric materials.
In this talk, I will show results we have obtained in oxides with different crystallographic structures,
with corner shared octahedra (perovskites) or edge shared octahedra (misfits and hollandites), to
show the peculiarities of Seebeck coefficient observed for each structure, and emphasize the role of
spin and orbital degeneracies associated to the transition metal cation (Co, Ru…) on thermopower [2].
For thermoelectric applications, the three important quantities to optimize are the Seebeck coefficient
2
S, the electrical resistivity ρ and the thermal conductivity κ, and the ZT value (ZT = S T/(ρκ)) shoud be
close to 1. Even if some ZT close to 1 have already been reported, the best ZT are close to 0.4 – 0.5
at ~ 1000K for oxides, and the major limiting factor is the too large electrical resistivity. By increasing
covalency, better conductivities are obtained in sulfides and selenides [3] and we will show that for
similar structures with edge shared octahedra, sulfides and selenides can also present interesting
thermoelectric properties [4].
Referencias
[1]
[2]
[3]
[4]
J. Merino et al., PRB61, 7996 (2000) ; K. Behnia et al., JPMC16, 5187 (2004).
S. Hébert et al., PSSA210, 69 (2013).
K. Koumoto et al., J. American Ceramic Soc. 96, 1 (2013).
H. Takahashi et al., Chem. Mater. 25, 1809 (2013).
Cartography of the Van der Waals Territory Santiago Alvarez Departament de Química Inorgànica and Institut de Química Teòrica i Computacional Universitat de Barcelona, Martí i Franquès 1-­‐11, 08028 Barcelona A cartography of the intermolecular distance region between two elements provides a perspective view of the bonding – non bonding duality, and allowed to extract a new consistent set of van der Waals radii for most naturally occuring elements. For the case of transition metal centers with loosely bound ligands and ill-­‐defined coordination spheres that populate the lawless frontiers between bonds and van der Waals contacts, a contiuous shape measures approach allows us to tackle the problem of precisely defining the stereochemistry of the coordination sphere. Finally, coordination ability indices for solvents and anions towards transition metals or lanthanides have been deduced based on the frequency with which they appear as coordinated, semicoordinated or uncoordinated species in crystal structures. References S. Alvarez. "A Cartography of the Van der Waals Territory", Dalton Trans. 2013, 42, 8617. A. Ruiz-­‐Martínez et al. "Ligand Association/Dissociation Paths and Ill Defined Coordination Numbers", Chem. Eur. J. 2010, 16, 6567. R. Díaz-­‐Torres, S. Alvarez. "Coordinating Ability of Anions and Solvents Towards Transition Metals and Lanthanides", Dalton Trans. 2011, 40, 10742. Persistent luminescence of the ZnGa2O4:Cr
nanophosphors for in-vivo bio-imaging
Bruno Viana
Institut de Recherche de Chimie Paris, CNRS
Chimie ParisTech, 11 rue Pierre et Marie Curie, 75005 Paris, France
Abstract :
ZnGa2O4 (ZGO) is a normal spinel. When doped with Cr3+ ions, ZGO:Cr becomes a high
brightness persistent luminescence material with an emission spectrum perfectly matching the
transparency window of living tissues. It allows in vivo mouse imaging with a better signal to
background ratio than classical fluorescent near infrared probes. One of the most interesting
characteristic of ZGO:Cr lies in the fact that its persistent luminescence can be excited with
orange/red light, well below its band gap energy and well in the transparency window of
living tissues. A mechanism based on the trapping of carriers localized around a special type
of Cr3+ ions can explain this singularity. Optical imaging of vascularization, tumors and
grafted cells can therefore be realized.
Mª Pilar Alonso Abad Universidad de Burgos VIII Encuentro franco-­‐español de Qca. y Fca. del estado sólido 2-­‐4-­‐Abril-­‐2014 El Patrimonio vidriero del Real Monasterio de Las Huelgas de Burgos: Patrimonio, Conservación y Caracterización EL PATRIMONIO VIDRIERO DEL REAL MONASTERIO DE LAS
HUELGAS DE BURGOS:
PATRIMONIO, CONSERVACIÒN Y CARACTERIZACIÓN
Mª Pilar Alonso Abad
Universidad de Burgos
Resumen
La vidriera es un arte del fuego muy versátil, simbólico y doctrinal. En la Historia ha
disfrutado de momentos de mayor y menor desarrollo en los que se ha podido descubrir la
riqueza productiva y la constante experimentación en sus materiales y composición.
Fue precisamente durante la Edad Media cuando alcanzó su mayor apogeo,
particularmente en Europa. Las catedrales asumieron el protagonismo de importantes programas
vidrieros que complementaron la iconografía presentada en el edificio pero, junto a ellas, fueron
determinantes algunos monasterios –más bien algunas órdenes religiosas-, particularmente los
vinculados de algún modo a la monarquía y/o la nobleza, porque bajo su amparo, protección y
promoción llevaron a cabo notables representaciones de este arte. De este modo, los reyes,
obispos y abades, fueron los grandes impulsores de los programas vidrieros.
El Real Monasterio de Santa María la Real de Las Huelgas de Burgos atesora un
importante exponente de vidrieras, las más antiguas conservadas de la Península. Gracias al
patrocinio regio, esta institución, real y religiosa, recibió este arte del fuego en un momento en
que se debatía su utilización en el seno de la Orden cisterciense, y en la Península se desconocía
la técnica y el procedimiento de elaboración de la vidriera, cuya historia había abierto una de
sus páginas más importantes a finales del siglo XII y que perduraría durante siglos.
Hábiles y diestros artesanos franceses realizaron un ciclo del apostolado para la iglesia
monástica. Retirado de este lugar, se ha conservado parcialmente y disperso –en la Sala
Capitular, en la Hospedería y en el Nuevo Oratorio de la comunidad-.
En el año 2008 culminó el proceso de restauración integral de las tres vidrieras que
cierran los ventanales del Capítulo del Claustro de San Fernando de esta abadía burgalesa. Un
vidrio rojo, de características peculiares, extraído durante el proceso de conservaciónrestauración de una de las vidrieras, fue analizado en el Instituto de Cerámica y Vidrio del CSIC
para conocer su composición química y su estructura, pudiendo reconocer una composición
multicapa característica de la Edad Media.
1 Mª Pilar Alonso Abad Universidad de Burgos VIII Encuentro franco-­‐español de Qca. y Fca. del estado sólido 2-­‐4-­‐Abril-­‐2014 El Patrimonio vidriero del Real Monasterio de Las Huelgas de Burgos: Patrimonio, Conservación y Caracterización Bibliografía
ALONSO ABAD, Mª Pilar, “Las vidrieras del Real Monasterio de Las Huelgas de Burgos.
Pasado y Presente”, Estudios de Historia y Arte. Homenaje al Profesor D. Alberto C. Ibáñez
Pérez, Universidad de Burgos, 2005, pp.253-257.
ALONSO ABAD, Mª Pilar, CAPEL DEL ÁGUILA, Francisco, et alii, Las vidrieras del
Rosetón del Sarmental de la Catedral de Burgos: Caracterización físico-química de algunos
vidrios, XLVIII Congreso Nacional de la Sociedad Española de Cerámica y Vidrio. SECV,
Oviedo, 29-31-Octubre-2008.
ALONSO ABAD, Mª Pilar, CAPEL DEL ÁGUILA, Francisco, et alii, “Caracterización de un
vidrio rojo medieval procedente de las vidrieras del Monasterio de Las Huelgas de Burgos”,
Boletín de la Sociedad Estatal de Cerámica y Vidrio, vol.48, nº4 (2009/Julio-Agosto), p.179186.
LA IGLESIA, A.; LÓPEZ DE AZCONA, M.C., “El Tratado del secreto de pintar a fuego las
vidrieras de colores de F. Sánchez Martínez, 1718”, Boletín de la Sociedad Española de
Cerámica y Vidrio, vol.33 (1994), p.327-331.
L’ESCALOPIER, Charles,Comte, Théophile prètre et moine, Essai sur divers arts=Theophili
presbyteri et monachi Libri III seu Diversarum artium schedula, Paris, 1873.
NIETO ALCAIDE, Víctor, La vidriera y su evolución, Madrid, 1974.
NIETO ALCAIDE, Víctor., La vidriera española. Ocho siglos de luz, Madrid, 1998.
2 VIII Encuentro Franco-Español de Química y Física de Estado Sólido
2-4 Abril 2014, Vila-real
Laser synthesis of coatings under extreme conditions
I. de Franciscoa, V. V. Lennikova, F. Rey-Garcíaa,b , C. Baob, L. A Angurela, G. F. de la
Fuentea*
a
ICMA (CSIC-Universidad de Zaragoza), c/María de Luna, 3 50018 Zaragoza
b
UA de Microóptica & Óptica GRIN (USC-CSIC), Facultade de Óptica e Optometría,
Campus Sur, Universidade de Santiago de Compostela, Campus Vida s/n 15782.
Lasers have become useful tools in a large number of industrial processes during the
last decades and offer unprecedented potential to advance materials processing under
conditions never before available in the laboratory. This is particularly attractive when
considering high melting solids and their interaction at extremely high temperatures.
Since laser beams may be easily steered within complex geometrical arrangements, they
are ideal sources to achieve high temperatures in any type of environment. For example,
they enable high temperature treatments in open air, within vacuum, under various gas
streams and, as recently demonstrated, within high temperature kilns [1, 2]. In essence,
their potential to develop new, high temperature chemistry, is only limited by our
imagination.
A new “Laser Furnace” tool that enables processing of inorganic solids under
continuous displacement, within an externally heated volume, will be presented along
with its main features. One of the main advantages of this recently patented method is
that it allows reaching extremely high temperatures on coated surfaces, without causing
appreciable thermal-stress derived damage on the substrates.
Examples of its application to structural and functional materials will be presented and
discussed.
1. L. C. Estepa & G. F. de la Fuente, Patent No. 200600560 (2006). 2. I. de Francisco et al., Solid State Sciences 13 (2011) 1813-1819.
Acknowledgements: MAT2010-­‐18519,EU: LIFE11/ES/560 & UV-­‐MARKING (FP7), DGA-­‐T87. Advanced Applications using an annular four-channel Silicon Drift Detector
R. Terborg, A. Kaeppel, T. Salge
Bruker Nano GmbH, Schwarzschildstr. 12, 12489 Berlin, Germany
Silicon Drift Detectors (SDDs) have become the standard detectors for energy dispersive x-ray
detection in the last few years. High resolution type SDDs have an energy resolution down to
121eV or better at Mn-Ka. They also have a good low-energy performance down to energies
about 69 eV (Al-Ll/Ln) and show undistorted Gaussian peak shapes in the low-energy range.
Optimized electronics maintain the energy resolution even for count rates up to 100 kcps input
count rate.
A special configuration has recently been developed for certain applications in order to improve
certain limitations: Multiple element SDDs with four separate detectors integrated onto one chip
but with separate electronics, provide even higher count rates through increased active area
without increasing pile-up or dead time [1,2].
A special multi element concept is the XFlash® 5060FQ (Fig. 1), an annular detector which can
be placed between the pole piece and the sample in a standard SEM using a BSE detector like
setup. The four SDD elements have an active area of 15mm² each resulting in a total of 60mm².
This large active area and the annular geometry, where the detector elements are very close to the
x-ray source, lead to an extremely large solid angle of more than 1 sr. This is a value which is
typically 100 times larger than a 10mm² detectors in a conventional setup. Therefore extremely
high count rates can be achieved easily even with low probe currents, and can be processed with
four separate electronic channels in parallel, leading to maximum output count rate of more than
1,100,000 cps. The energy resolution is 133eV or better at Mn-Ka.
These properties make the detector an ideal device for high speed mapping applications. Fig. 2
shows a high speed x-ray mapping of a micro crator in an aluminium foil, produced by a small
projectile consisting of magnesium, calcium and iron. The distribution of these elements was
analysed in a mapping acquired at 12kV accelerating voltage with a probe current of 2nA. The
element mapping with a resolution of 4096x3072 pixels was taken in only 210s total acquisition
time. The count rate was 1.4cps resulting an average number of counts of 11 per pixel. The ability
of this detector to acquire X-rays from four different directions due to the four channels and a
relatively high take-off angle lead to a significant reduction of shadowing effects. Therefore also
the element distribution at the bottom of the crater can be seen which would not be possible with
a conventional detector setup.
References
[1] H. Soltau et al., Microsc. Microanal. 15 (Suppl.2) (2009), 204
[2] R. Terborg, M. Rohde, Microsc. Microanal. 17 (Suppl.2) (2011), 892
Fig. 1. Flat Quad detector (XFlash® 5060FQ), which is placed between the pole piece and
the sample.
Fig. 2. Ultra high speed mapping of a micro crater in an aluminium foil. HV=12kV, I=2nA,
resolution: 4096x3072 pixel, acquisition time 210s, average count rate 1.4 Mcps. Note the
reduced shadow effects.
Electrodeposition of oxide thin films and
nanostructures for optoelectronics
Daniel LINCOT, Jean ROUSSET, Fabien TSIN, Aurelien DUCHATELET, Tarik SIDALI,
Elisabeth CHASSAING
Institut Photovoltaïque Ile de France (IPVF), Institut de Recherche et Dèveloppement sur l'Energie Photovoltaïque,,UMR CNRSEDF-Chimie Paristech, 6 Quai Watier, 78401 Chatou
1. Introduction
The electrodeposition of oxide thin films and nanostrucures is an emerging field with great
interest both for the fundamental aspects at the frontier between electrodeposition and
materials and for optoelectronic applications. This presentation will recall the grounds of the
electrodeposition of oxides and move to specific cases which are under study in our
laboratory. The first one concerns zinc oxide, with three areas, the deposition of thin films,
that of nanocolumns and that of nanoporous films by templated growth. The specificity of
electrodeposition of zinc oxide is that it possesses already after fabication, semiconductor
properties with excellent structural quality. It is also possible to control its conductivity thanks
to the introduction of extrinsic dopants like chlorine. This approach is emerging as a potential
candidate to produce transparent conducting oxides in photovoltaics, with exemples for CIGS
thin film solar cells. In the case of nanostructures, we will present some applications in the
field of dye sensitized solar cells (DSSC) and highly specific topics as electrical properties of
nanoporous networks. An other exemple of remarkable as grown properties will be given by
results obtained on the electrodeposition of copper oxide. The last topic which will be
presented concerns the electrodeposition of multinary Cu-In-Ga oxides/hydroxides. These
films of controlled composition can serve as intermediates for the formation of copper
indium gallium diselenide layers for efficient solar cells.
Chemistry and applications of perovskite oxynitrides
Amparo Fuertes
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra (Spain)
E-mail: [email protected]
Oxynitrides represent a vast group of compounds to explore new materials with properties analogous
to oxides. [1] The similarities in electronegativity, polarizability, ionic radii and coordination numbers of
nitrogen and oxygen allow the formation of the same structural types when combined with cations, as
well as the mutual substitution of both anions at the same crystallographic sites. This may result in the
formation of solid solutions where the formal oxidation state of one or more cations changes according
to the O/N ratio.
Oxynitride perovskites have been recently reported as non-toxic inorganic pigments, dielectric
materials, visible light-active photocatalysts and colossal magnetoresistance materials among other
applications. [2] Perovskites of alkaline earth and early transition metals with formula AMO2N (A= Sr,
Ba) have been reported as dielectric materials (M=Ta) and visible light-active photocatalysts for water
splitting (M=Nb, Ta). Perovskites of europium and Nb, Ta or W show a variety of electrical and
magnetic properties that are tuned by the valence states of the cations and adjusted by the N/O ratio.
They are prepared by treating precursor oxides under NH3(g) and the nitrogen stoichiometry is
controlled by changing the temperature, flow rate and treatment time in the ammonolysis reaction.
Depending on the electronic configurations of europium and the transition metal these compounds
may show electronic conductivity and ferromagnetism that if coupled result in giant to colossal
magnetoresistance. [3,4] Moreover microstructural inhomogeneities lead to non-intrinsic
magnetocapacitance and non-ohmic conductivity. [5]
The differences in electrical charge and electronegativity between nitrogen and oxygen direct the
ordering of both anions in many oxynitrides. [6] In the above perovskites the ordering is driven by
covalency and this lead to a preferred cis configuration of nitride anions in the octahedra MO4N2 and
the formation of disordered zig-zag M-N chains. [7] The anion order remains at high temperature in the
pseudocubic phase and directs the rotations of the octahedra in the room-temperature superstructure.
This lecture will present recent results on perovskite oxynitrides of europium, strontium and the early
transition metals Ta, Nb, W and V, [8] focussing on the relationships between the synthesis conditions,
the oxidation states of the cations, the crystal symmetries and tilt transitions, the anion ordering and
the physical properties.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
A.Fuertes, Dalton Trans. 2010, 39, 5942.
A.Fuertes, J. Mat. Chem. 2012, 22, 3293.
A.B.Jorge, J.Oró-Solé, A.M.Bea, N.Mufti, T.T.Palstra, J.A.Rodgers, J.P.Attfield and A.Fuertes, J. Am.
Chem. Soc. 2008, 130, 12572.
M. Yang, J.Oró-Solé, A. Kusmartseva, A.Fuertes, and J. P.Attfield, J. Am. Chem. Soc. 2010, 132, 4822.
A. Kusmartseva, M. Yang, J. Oró-Solé, A. M. Bea , A. Fuertes and J. P. Attfield , Appl. Phys. Lett., 2009, 95,
022110.
A.Fuertes, Inorg. Chem., 2006, 45, 9640-9642.
M.Yang, J.Oró-Solé, J.A. Rodgers, A. B. Jorge, A.Fuertes, and J. P.Attfield, Nature Chem. 2011, 3, 47-52.
J. Oró Solé, L. Clark, N. Kumar, W Bonin, A. Sundaresan, J.P. Attfield, CNR Rao and A. Fuertes, J. Mat.
Chem. C, 2014, DOI:10.1039/C3TC32362E.
Comunicación Oral
Sólidos mullíticos preparados a partir de geles y
vidrios
Noemí Montoya, Pablo Pardo, José Miguel Calatayud, Hadiseh Tabaie y Javier Alarcón
Universidad de Valencia, Departamento de Química Inorgánica, Calle Doctor Moliner 50, 46100-Burjasot (Valencia) España
[email protected]
1. Introducción
La mullita es un componente esencial de muchos materiales cerámicos tradicionales de amplio uso
doméstico e industrial, incluyendo desde los productos de la denominada Cerámica Blanca hasta
productos de porcelana eléctrica con alta resistencia mecánica, y también de cerámicos técnicas,
tales como los productos monofásicos de mullita con alta resistencia mecánica a temperaturas muy
elevadas.
La mullita es el único compuesto binario dentro del sistema SiO2-Al2O3. Estructuralmente es una
disolución sólida con estequiometría Al4+2xSi2-2xO10-x, siendo estables termodinámicamente en el
intervalo composicional 0,25 ≤ x ≤ 0,4 [1, 2]. No obstante, se han detectado mullitas metaestables, de
diferentes procedencias, hasta con contenidos de 85 % en peso de Al2O3 (x>0,64).
En esta comunicación vamos a mostrar como mediante la utilización de un método no convencional
simple de preparación de sólidos inorgánicos no metálicos (cerámicos), tal como el sol-gel, se pueden
obtener mullitas en todo el intervalo de composiciones incluyendo las composiciones metaestables
muy aluminosas [3]. Estas mullitas se han caracterizado por diferentes técnicas, incluyendo difracción
de rayos X, espectroscopias IR, Raman y resonancia magnetica nuclear y por microscopia electrónica
de barrido y transmisión. Los resultados confirman que mediante esta técnica se pueden preparar
mullitas con relaciones Al2O3:SiO2 mayores de 7,3:2, es decir con contenidos mayores de alumina de
85 % (en peso).
Con el objetivo de mostrar nuevas aplicaciones de solidos basados en la fase mullita, en la segunda
parte de la comunicación comentaremos algunos pasos en el desarrollo de productos cerámicos por
excelencia, concretamente de esmaltes vitrocerámicos basados en fase cristalina mullita [4]. Estos se
desarrollaron a partir de vidrios en el sistema cuaternario CaO-MgO-Al2O3-SiO2 adicionando los
aditivos requeridos para permitir la cristalización controlada en el intervalo de temperaturas entre
1100 y 1200 ºC [5]. La cantidad de mullita desarrollada en estos esmaltes vitrocerámicos tratados en
proceso rápido a 1160 ºC es de 19,5 % en peso y su microestructura muestra cristales de mullita
aciculares bien formados dispersos en la fase vítrea residual. Los resultados de las propiedades
mecánicas de estos esmaltes vitrocerámicos desarrollados industrialmente fueron prometedores. No
obstante todavía deben realizarse esfuerzos dirigidos a optimizar el tamaño de la fase cristalina
desarrollada en el esmalte, en cuanto a conseguir esmaltes vitrocerámicos nanofásicos.
Agradecimientos
Se agradece la financiación del Ministerio de Ciencia y Tecnologia por la financiación al proyecto
Consolider Ingenio (CSD2010-00065) y al proyecto Prometeo (2011/008) de la Generalitat
Valenciana. Asimismo, agradecemos a los investigadores F. J. Torres y a E. Ruiz de Sola su
contribución a los resultados presentados.
Referencias
[1] W. E. Cameron, “Compositions and cell dimensions of mullite”, Am. Ceram. Soc. Bull. 56, 11, (1977), 10031011.
[2] H. Schneider, R. X. Fischer, D. Voll, “Mullite with lattice constants a>b”, J. Am. Ceram. Soc., 76, 7, (1993),
1879-1881.
[3] E. Ruiz de Sola, F. Estevan, F. J. Torres, J. Alarcón, “Effect of termal treatment on the structural evolution of
3:2 and 2:1 mullite monophasic gels”, J. Non-Cryst. Solids., 351,(2005), 1202-1209.
[4] R. Casasola, J. Ma. Rincón, M. Romero “Glass-ceramic glazes for ceramic tiles: a review”, J. Mater. Sci., 47,
2, (2012), 553-582.
[5] F. J. Torres, E. Ruiz de Sola, J. Alarcón, “Effect of boron oxide on the microstructure of mullite-based glassceramic glazes for floor-tiles in the CaO-MgO-Al2O3-SiO2 system”, J. Eur. Ceram. Soc., 26, (2006), 22852292.
Solid State Chemistry of some Chromium Oxides
Miguel Ángel Alario y Franco
Laboratorio Complutense de Altas Presiones. Facultad de
Química. Universidad Complutense. 28040 Madrid. SPAIN (EU).
e-mail: [email protected];
http://www.ucm.es/info/labcoap/index.htm
As most transition metals, chromium exhibits several oxidation states, which, in the
case of oxide materials, are limited to Cr (II to VI). This, combined with their comparative
stability implies the relative scarcity of binary, single-valent oxides, which essentially are Cr2O3
and CrO3. Using HP & HT in the synthesis, one can obtain the, also important, CrO2.
Nevertheless, considering mixed–valent oxides the list increases to Cr2O5 (which is, in fact,
3+
6+
III
VI
Cr 2Cr 4O15), Cr5O12 (that is formulated as Cr 2Cr 3O12) and Cr3O8 which is, in fact Cr8O21
III
VI
VI
(formulated as Cr 2(Cr O4)2(Cr 4O13) and to the short list of CS phases (CrnO2n-p) observed
between CrO2 and Cr2O3.
However, one can largely extend the checklist by making ternary or higher oxides by
the combination of the above species with different oxides of both transition and non-transition
metals.
In the present lecture, we will describe a series of multinary oxides of Chromium that we
have obtained by solid state reactions at High Temperature and, often, with the concourse of
High Pressure. By this means, and starting with CrO2, we have prepared a number of
perovskite, rutile and hollandite based multinary oxides such as: Sr1-xCaxCrO3 (0 < x < 1),
“PbCrO3”, Sr3Cr2O7, MSr2RECu2O7 (M <> Ru, Cr, Ir, Mo; RE <> Rare Earth) and some misfit
layer compounds around the [SrO2][CrO2]1.85 composition; we will also briefly mention K1.2Cr8O16
and the Cr1-xVxO2 solid solution.
All these materials show remarkable microstructures (as observed by HREM & ED)
and very interesting transport and magnetic properties.
We have also used EEL-Spectroscopy, performed in situ in the electron microscope, to
establish the oxidation states of chromium in the different oxides.
After a brief general description of the ensemble, we will discuss, in order of complexity,
some of them. This will show inter alia the change in the microstructure with composition in the
solid solutions, the remarkable structural complexity of “PbCrO3” as well as some intriguing and
unusual dependence of the synthesis conditions for the MSr2RECu2O7 (M <> Ru, Cr, Ir, Mo)
family on the Rare Earth element.
Acknowledgements:
I would like to thank my past and present doctoral students: A. Dos Santos, E. Castillo ,
Á. Arévalo, R. Ruiz. I. Pirrotta & Sourav Marik, for his important contributions to this work and
Dr. J.M. Gallardo for technical assistance. I would also like to thank Dr. A. Durán (UNAMMexico) and Professors E. Morán and R. Sáez (both at UCM-Madrid. Spain) for valuable
comments.
References:
M.Á. Alario & K. S.W. Sing: J. Thermal Analysis (1972)
E. Castillo-Martínez, A. M. Arévalo-López, R. Ruiz-Bustos, and M. A. Alario-Franco: Inorganic
Chemistry, Vol. 47, No. 19, 2008.
Ángel M. Arévalo-López, Miguel Á . Alario-Franco: Journal of Solid State Chemistry 180 (2007)
3271–3279.
Ángel M. Arévalo-López, Miguel Á . Alario-Franco:Inorg. Chem. 2009, 48, 11843–11846.
Pirrotta, J. Fernández-Sanjulián, E. Morán, M. A. Alario-Franco, E. Gonzalo, A. Kuhn and F.
García-Alvarado: Dalton Trans., 2012, 41, 1840.
Sourav Marik, A J Dos santos-Garcia, Emilio Morán, O Toulemonde and M A Alario-Franco: J.
Phys.: Condens. Matter 25 (2013) 165704.
ABSTRACT BOOK
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Direct atomic observation of Sr-Mn-O nanoparticles
1,
1, 2
1
Irma N. González-Jiménez *, Almudena Torres-Pardo , Ana E. Sánchez-Peláez , Ángel
3
4
1
3
Gutiérrez , David Portehault , Clément Sanchez , Mar García-Hernández , José M. González1, 5
1
1
Calbet , Marina Parras and Áurea Varela .
1.
3.
Departamento de Química Inorgánica, Facultad de CC. Químicas, Universidad Complutense de Madrid, 28040
Madrid (SPAIN).
2. CEI Campus Moncloa, UCM-UPM, Madrid, (SPAIN).
Chimie de la Matière Condensée de Paris, Collège de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05
(FRANCE).
4. Instituto de Ciencia de Materiales, CSIC, Cantoblanco, 28049 Madrid (SPAIN).
5. Centro Nacional de Microscopía Electrónica CNME, 28040 Madrid (SPAIN).
*[email protected]
The current demand of technological devices requires the continuous preparation of new compounds
at the nanometer scale in such a way that their chemical and physical properties enable the
development of novel applications. Mn-related mixed nanooxides constitute a promising system in the
field of nanoscience and nanotechnology as a result of the structural variety, due to the number of
oxidation states in which Mn can be stabilized, and outstanding properties found in their bulk
counterparts [1]. Particularly, in the Sr-Mn system there are several well-known phases as SrMnO3,
Sr2Mn2O5, Sr4Mn3O10, etc. However, none of them has been prepared in the form of nanoparticles up
to now. The electrical and magnetic properties manifested in these materials, gain much more
relevance in those structural types which can accept anion deficiency.
We report for the first time the stabilization and structural and magnetic characterization of single
crystalline 4H-SrMnO3- δ (δ=0, 0.18) nanoparticles and Sr4Mn3O10 nanoplatelets.
SrMnO3. Stoichiometric 4H-SrMnO3.0 nanoparticles have been successfully synthesized from thermal
decomposition, at 850 ºC under oxygen gas flowing atmosphere, of a new heterometallic precursor
3
[SrMn(edta)(H2O)5]· /2H2O which crystal structure has been solved by single crystal X-ray diffraction.
From this precursor, highly homogeneous 4H-SrMnO3.0 nanoparticles
with average particle size 70 nm are obtained (figure 1). Local structural
information, provided by atomically-resolved microscopy techniques,
shows that 4H-SrMnO3.0 nanoparticles exhibit the same general
structural features than the bulk material, although structural disorder,
due to edge-dislocations, is observed. The nanosize of particles enables
a topotactic reduction process at 220 ºC stabilizing a metastable 4HSrMnO2.82 phase while a cubic related phase is always stabilized for
anionic compositions below SrMnO2.98 in bulk material [2].
This anionic deficiency is accommodated via insertion of cubic layers in
hexagonal perovskites. In our case and as a result of breaking the 4Hsequence (…hchc…), extended defects are generated. These can be
Figure 1. SEM of
SrMnO3.0 particles The
observed and assessed providing the most refined spatial resolution
inset shows the particle
imaging and spectroscopic techniques. With these techniques the
size distribution.
topotactic reduction pathway can be followed step by step at an atomic
level (figure 2).
Magnetic characterization of nano-SrMnO3.0 shows significant variations with respect to the bulk
material. Besides the dominant AFM interactions, a weak FM contribution as well as exchange bias
3+
and a glassy-like component are present. After the reduction process, the stabilization of Mn in the
4H-structure gives rise to magnetic anomalies in the 40-60 K temperature range.
Sr4Mn3O10. Sr4Mn3O10 nanoplatelets have been prepared by molten salts method at 600 ºC under
argon gas flowing atmosphere. Sr(OH)2 is used in high excess as both solvent and reactant. The
reactant excess is removed by adding HNO 3 (cc). This washing step affects the particles in such a
way that amorphous areas appear in all nanoplatelets (figure 3a, b).
The growth mechanism for Sr4Mn3O10 particles was followed by recording low magnification HRTEM
images of particles obtained at different synthesis time. Hexagonal-shaped flat morphology was
observed for smallest size particles formed after short reaction time. These particles seem to
aggregate each other along the [1 1 0] crystallographic direction to form bigger particles (figure 3c, d)
and additionally, these medium size particles also seem to stack on top of each other (figure 3e) giving
rise to the thicker and biggest particles similar to those observed after longer reaction time. Magnetic
properties of Sr4Mn3O10 platelets will be discussed.
Figure 2. (a) Atomically-resolved HAADF image corresponding to a defect area of a SrMnO2.82 nanoparticle
along [010]. Extended structural defects (yellow box) are involved on the rearrangement of the stacking
sequence of hexagonal and cubic layers along a-axis (marked as A and B areas). Red and green dots indicate
Sr and Mn atomic columns, respectively. (b) Schematic drawing of the cationic rearrangement along a-axis
(color code: Sr in red; Mn in green; O positions in blue). (c,d) Simultaneously recorded high magnification [010]
HAADF and ABF images, respectively, showing the detailed structure in the defect area. A cubic layer is
schematically represented: red, green and blue dots indicate Sr, Mn and O positions, respectively. Yellow arrow
indicates Mn-O-Mn rows.
Figure 3. Low magnification HRTEM image of (a) a representative Sr4Mn3O10 particle obtained after 1 h
synthesis-time and (b) after HNO3 (cc) washing step. (c) Coalescence of small hexagonal particles seems to
occur along [110] crystallographic direction as observed in the enlarged regions showed in (d). (e) High
magnification HRTEM image of a coalescence area unambiguously confirms the crystallographic order
becoming visible along the (110) direction. (f) Low magnification TEM image of a Sr4Mn3O10 particles stack on
top of each other.
Referencias
[1]
[2]
D. Neagu, G. Tsekouras, D. N. Miller, H. Ménard, J. T. S. Irvine, “In situ growth of nanoparticles through
control of non-stoichiometry ”. Nature Chem., 5, (2013), 916-923.
V. F. Balakirev and Yu. V. Golikov, “Phase Relations in Alkaline Earth–Manganese–Oxygen Systems:
Equilibrium and Metastable States”. Inorg. Mater., 42, 1, (2006), S49-S69.
Characterization and fabrication of LSCF tapes
R. Fernández-González1,2,*, T. Molina3, S. Savvin1, R. Moreno3, A. Makradi2, P. Núñez1
1. Departamento de Química Inorgánica, Universidad de La Laguna, 38200 La Laguna, Tenerife, Spain
2. Centre de Recherche Public Henri Tudor, 29, avenue John F. Kennedy, L-1855 Luxembourg-Kirchberg, Luxembourg
3. Instituto de Cerámica y Vidrio, ICV-CSIC, Calle Kelsen 5, 28049 Madrid, Spain
*[email protected]
1. Introduction
Mixed oxides of lanthanum, strontium, iron and cobalt (La1-xSrxCoyFe1-yO3-) with perovskite structure
are good candidates for many devices such as solid oxide fuel cell (SOFC) due to their high mixed
electronic-ionic conductivity and electrocatalytic activity [1], gas separation membranes [2] or catalysts
for oxidation of hydrocarbons [3].This kind of perovskite membranes exhibits high oxygen permeability
at elevated temperatures [4].
In this work the manufacture of commercial La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) by aqueous colloidal
processing is presented. The surface behavior of LSCF as a function of pH and the effect of a
polyelectrolyte (Duramax D3005) on the stability are studied using measurements of zeta potential.
Concentrated suspensions were prepared to solid content as high as 35 vol.%. The best dispersing
conditions were determined by means of rheological measurements for obtaining stable and fluid
slurry for tape casting technique. Different relative densities of the tapes were obtained at different
temperatures. The LSCF tapes are good candidates for using as gas separation membrane or
cathode for SOFC.
2. Figures
Fig. 1. Zeta potential vs pH of LSCF commercial powder.
Fig. 2. Evolution of Zeta potential versus % of polyacrylic based deflocculant,measured as-prepared and 24 h
later.
Fig. 3. Rheological behavior of 35 vol.% solid suspensions of LSCF prepared at different sonication minutes.
3. Conclusions
The surface behavior study of LSCF commercial powder permits to determine that the isoelectric point
of the material occurs at pH around 6 (Fig. 1). When suspensions are prepared to extreme pH values,
they tend to stabilize by moving toward more neutral values. In general, suspensions cannot be
prepared at acidic pH values because there is a significant dissolution of the cations that could change
not only the surface behavior but also the composition and final properties of the material. The acidic
suspensions are more stable than basic ones, but the largest solubility is obtained at pH 2; this is in
opposition to the maximum zeta potential value measured at this pH and the relatively good stability of
pH with time. The only possibility to explain the stability of these suspensions is that they contain
significant concentrations of multivalent cations, that they could form complexes and do not remain
free in the dispersing medium. So, to control the solubility and the stability it is necessary to avoid pH
variations. Addition of a polyacrylic based deflocculant allows stable aqueous suspension, 0.3 wt% is
enough for stabilize the slurry (Fig. 2). The ultrasounds study permits to control the thixotropy and
obtain fluid suspensions for manufacturing LSCF tapes (Fig. 3). The temperature study allows
knowing that the relative density is high, more than 99% at temperatures ranging from 1300ºC to
1400ºC, at lower temperatures the tapes are porous (less than 85% RD). As it was expected, at high
temperature the LSCF reacts and form secondary phases that can reduce the ionic conductivity.
Taking into account all the exposed on this work: the knowledge of LSCF rheological behavior, the
manufacture of tapes and how the relative density evolves; allow us to propose this LSCF tapes as a
good ion transport membrane or cathode material for future devices.
4. Acknowledgements
We wish to thank financial support from Luxembourgish Government via FNR (project OMIDEF Grant
FNR/786 643). We also thank to the Spanish Research Program through grant MAT2010-16007 and
grant MAT2009-14369-C02-01.
References
[1] W.G. Wang, M. Mogensen, “High-performance lanthanum-ferrite-based cathode for SOFC”. Solid State Ionics,
176, (2005), 457–462.
[2] H. Ullmann, N. Trofimenko, “Composition, structure and transport properties of pervoskite-type oxides”. Solid
State Ionics, 119, (1999), 1–8.
[3] U.B. Balachandran, B. Ma, “Mixed-conducting dense ceramic membranes for air separation and natural gas
conversión”. Journal of Solid State Electrochemistry, 10, (2006), 617–624.
[4] H.J.M. Bouwmeester, H. Kruidhof , A.J. Burggraaf, “Importance of the surface exchange kinetics as rate
limiting step in oxygen permeation through mixed-conduction oxides”, Solid State Ionics 72, (1994), 185-194..
[Comunicación Oral]
Eu(III)-doped (Ca0.7Sr0.3)CO3 phosphor as
shock/temperature detector
1,*
1,2
1
V. Blanco-Gutiérrez , V. Jubera , A. Demourgues , M. Gaudon
1,2,*
1. CNRS, ICMCB, UPR 9048, F-33600 Pessac, France
2 Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac, France
*[email protected]
Calcium carbonate (CaCO3) is one of the most abundant compounds in nature. It can be found in
2+
three allotropic forms with a different sphere coordination for the Ca cation. Vaterite (S. G. P63/mmc)
is the most kinetically favored phase, calcite (S. G. R-3c) the most stable at ambient conditions and
aragonite (S. G. Pmcn) is obtained at high-pressure values and is metastable at ambient conditions
with very slow kinetic of transformation into calcite phase. The transformation into the aragonite phase
1
only occurs at very high pressure values . However, it is possible to decrease this transformation
2+
2
pressure by doping the compound with Sr . In this case, the aragonite phase is stabilized due to the
2+
2+
higher ionic radii and lower electronegativity of Sr in comparison with Ca cation. On the other hand,
europium cation is one of the most employed luminescence activator due to its great optical
3
propeties. The incorporation of Eu(III) into a (Ca,Sr)CO3 structure may be faisible taking into account
3+
2+
2+
the proximity of the Eu ionic radii (0.95 Å, in octahedral site) in comparison to that of Ca or Sr
4
(1.00 and 1.16 Å respectively, in octahedral site), . In this work, metastable Eu(III)-doped
(Ca0.7Sr0.3)CO3 vaterite has been easily prepared by the precipitation method. The metastable phase
evolves to calcite when heating, and both vaterite and calcite phases transform into aragonite
structure with pressure. The structural and microstructural characterizations of the samples have been
performed by X-ray diffraction and transmission electron microscopy, respectively. Cell parameters
are coherent with literature data of the extreme compositions CaCO3 and SrCO3 considering a Vegard
law. Different luminescent properties have been found depending on the crystal structure due to the
different geometrical site where is located the Eu(III). The microstructure seems to affect the
luminescent properties as well. A scheme of phase transformation is represented in the Figure
together with the photoluminescence emission spectra of the corresponding samples.
Fig.: Raw photoluminescence emission spectra for Eu(III)-doped (Ca,Sr)CO3 vaterite, calcite and aragonite
samples. It is shown as well an image of the three samples after being irradiated at 250 nm. By the employment
of heat (T) or pressure (P) it is possible to obtain the different crystal structures.
The results lead to believe the obtained solid, as suitable material for temperature/shock detection. In
addition, the three crystal structures containing the europium cation were treated under reducing
conditions by the employment of CaH2. The major part of Eu(III) was reduced into Eu(II) and the used
soft conditions allowed preserving the crystal structure for each case. Different luminescent spectra
were also found for these samples.
References
[1]
[2]
[3]
[4]
Carlson W.D., American Mineralogist., 65, (1980), 1252-1262.
Pan Y., Wu M., Su Q., Mat. Res. Bull. 38, (2003), 1537-1544.
Jubera V., Chaminade J., Garcia A., Guillen F., Fouassier C., J. Lumin. 101, (2003), 1-10.
Shannon, R.D. Acta Cryst., A32, (1976), 751–767.
Pressure effect on Mn2FeSbO6:
Crystal structure-magnetic properties relationship
1,*
2
3
Elena Solana-Madruga , Antonio J. Dos Santos-García , Clemens Ritter and Regino Sáez-Puche
1. Dpto. de Química inorgánica, Universidad Complutense de Madrid, Ciudad Universitaria, 28040.
2. Dpto. de Química Industrial y Polímeros, Universidad Politécnica de Madrid, C/ Ronda de Valencia, 3. 28012-Madrid.
3. Institut Laue-Langevin, 38042 Grenoble Cedex, France.
1
*[email protected]
Compounds crystallizing with perovskite structure show a wide variety of properties, including
superconductivity, magnetorresistance or thermoelectricity [1]. The ideal perovskite structure is accepted
to have a tolerance factor t = 1, according to the Goldschmidt relation [2]. When t decreases, this ideal
cubic structure gets distorted perovskites down to the limit value of t = 0.8. However, ABO3 compounds
with t < 0.75 crystallize with corundum derivative structures, such as ilmenite (FeTiO 3) or LiNbO3. [3]
On the other hand, it is well known that pressure can induce irreversible phase transformations, e.g. from
ilmenite to perovskite structure, but also allows access to metastable phases at ambient pressure. [4]
High pressure is needed to stabilize A2MSbO6 (M = transition metal) double perovskites containing small
2+
2+
A site cations (e. g. Mn ). This work aims study the polymorphism induced under high pressure and
temperature conditions in Mn2FeSbO6 oxide. Perovskite and ilmenite polymorphs have been isolated and
characterized by means of X-ray and high resolution neutron diffraction measurements. The study of the
magnetic properties, through magnetization and magnetic susceptibility measurements at different
temperatures and magnetic field strengths, reveal quite different magnetic behavior according to their
different crystal structures.
The ilmenite polymorph has been synthesized at 5 GPa and 1473 K. X ray diffraction data show a
rombohedral R-3 nuclear structure with a = 5.23 Å and c = 14.37 Å. Magnetic susceptibility
measurements indicate a ferrimagnetic behavior with TN = 260 K, in agreement with the magnetic
structure determined from neutron diffraction data taken at 150 K (Figure 1a, 1b). This structure can be
2+
3+
described with a propagation vector k = [0 0 0], where the magnetic moments of 2Mn and Fe are
antiparallel aligned giving, as result, a ferrimagnetic behavior with an experimental ordered moment of
4.2 μB, as it can be observed in Figure 1b. However, it is worth noting that a second magnetic transition
has been observed for this compound below T = 50 K. Below this temperature, the magnetic structure
adopts an incommensurate helical spin ordering ruled by a propagation vector k = [0 0 0.07] with the
spins confined to the ab plane.
Increasing pressure up to 5.5 GPa during the synthesis process allowed the stabilization of the perovskite
polymorph.[5] This compound crystallizes with a monoclinic P21/n structure with cell parameters a = 5.23
Å, b = 5.39 Å, c = 7.64 Å and β = 90.37º. The complex magnetic behavior studied from dc and ac
magnetic susceptibility measurements has also been confirmed by neutron diffraction data. This
polymorph develops, at a first sight, antiferromagnetic interactions below TN = 60 K. However the ac
susceptibility data present a rounded maximum centered at 160 K, which cannot be attributed to longrange magnetic interactions, since there are not any noticeable changes in the PND data up and just
below this temperature. Then, it can be associated to an energy dissipation process that can be explained
as the result of the existence of short- range magnetic correlations which arise from ferromagnetic
inhomogeneities in the solid. The magnetic structure at 2 K can be described in terms of an elliptical spiral
with an incommensurate propagation vector k = [0 0.426 0], where spins are confined to the ac plane
(Figure 1c).
Figure 1. a) Rietveld refinement of PND data taken at 150K for ilmenite polymorph. Bragg intensities correspond to the nuclear and
magnetic structures (first and second rows) and Mn2Sb2O7 impurity phase. b) Magnetic structure of ilmenite polymorph at 150K. c)
Magnetic structure of perovskite polymorph at 2K.
Throughout this work, a comparative study on the magnetic properties of different polymorphs of
Mn2FeSbO6 oxide has been done. It is clear from the results that their magnetic properties strongly
depend on their crystal structure. This affinity can be explained in terms of the different magnetic
interaction paths induced by the change in the crystal structure: direct interactions can occur in the
ilmenite polymorph while spins must couple via superexchange interaction through oxygen in the
perovskite polymorph.
Acknowledgements:
The authors acknowledge funding from Comunidad de Madrid under the research project S-2009/PPQ1626 and MICINN through MAT2010-19460. Authors are also indebted to Institut Laue-Langevin for
beamtime allocation at D20, D1B and D2B instruments.
References:
[1] E. Climent-Pascual, N. Ni, S. Jia, Q. Huang and R. J. Cava. Phys. Rev. B, 83, (2011), 174512.
[2] V. M. Goldschmidt, T. Barth, G.Lunde and W. Zachariasen. Mat.-Nat. Kl, 2, (1926), 117.
[3] R. H. Mitchell, “Perovskites. Modern and Ancient”. Almaz Press, Ontario (2002).
[4] S. V. Ovsyannikov, A. M. Abakumov, A. A. Tsirlin, W. Schnelle, R. Egoavil, J. Verbeeck, G. Van Tendeloo, K. V.
Glazyrin, M. Hanfland and L. Dubrovinsky. Angew. Chem. Int. Ed., 52, (2013), 1494.
[5] A. J. Dos Santos-García, C. Ritter, E. Solana-Madruga and R. Sáez-Puche. J. Phys.: Condens. Matter, 25,
(2013), 206004.
Reactive Ion Etching on
(Yb,Nb):RbTiOPO4/RbTiOPO4 epitaxial layers for the
fabrication of Y-splitters and Mach-Zehnder
Interferometers
1
1
1
1
2
3
3
M.A. Butt , R. Solé , M.C. Pujol , A. Ródenas , G. Lifante , A. Choudhary , G.S. Murugan , D.
3
3
1
1
Sheperd , J.S. Wilkinson , M. Aguiló and F. Díaz
1. Física i Cristal·lografia de Materials i Nanomaterials (FiCMA-FiCNA) and EMaS, Universitat Rovira i Virgili (URV), Marcel·lí
Domingo s/n, E-43007 Tarragona, Spain
2 Departamento de Física de Materiales, Universidad Autónoma de Madrid 28049 Madrid, Spain
3 Optoelectronics Research Centre, University of Southampton, Southampton,SO171BJ, United Kingdom
* [email protected], [email protected]
1. Introduction
Rubidium titanyl phosphate RbTiOPO4 (RTP) belongs to a highly diverse and versatile structural family
and because of its large non-linear optical coefficients, wide transparency, high laser damage
threshold, high chemical stability and low dielectric constants, this material is highly attractive for
electro-optic applications such as modulators and Q-switches [1]. RTP has a similar non-linear optical
3+
coefficient to KTP but, unlike KTP, it can be doped with Yb ions to obtain a high enough
concentration to allow efficient laser action [2]. Because of all these interesting properties, RTP is a
strong candidate as a platform material for integrated photonics. Reactive ion etching (RIE) is a
commonly used method in etching of semiconductors, but there is little literature available on the
plasma-based etching of RTP. Moreover, single-mode rib waveguides have been successfully
fabricated in (Yb,Nb):RTP by RIE [3]. In this work, (Yb,Nb):RbTiOPO4/RbTiOPO4 (001) epitaxial layers
have been structured by RIE by using a combination of Ar and SF6 gases. The refractive index
contrasts between the (Yb,Nb):RbTiOPO4 layer and the RbTiOPO4 substrate at 1.55 microns have
been measured.
2. Experimental details
RTP single crystals were grown by the top seeded solution growth-slow cooling (TSSG) technique to
obtain thin plates of (001) oriented substrates. These substrates are well polished in order to have a
smooth interface when epitaxial layers are grown over them. Liquid Phase Epitaxy (LPE) was used to
obtain (Yb,Nb):RTP/RTP(001) in a well-isolated cylindrical vertical furnace with practically zero
thermal gradient. Refractive indexes of the epitaxial layer and the substrate have been measured at
1550 nm with prism coupler method. After obtaining 6-7microns of epitaxial layer, a metal layer was
deposited on it which acts as a hard mask during reactive ion etching. Different metal layers, for
instance Al, Ti, Cr, Ni were tried to test their adhesion on the RTP and their performance as a metal
mask. Channels designs were transferred by the help of conventional photolithography and the
sample was etched with metal etchant to remove the unwanted parts of the metal mask. Finally, the
samples with hard metal mask were put in a RIE Plasmalab 80Plus to etch. The process used was
250 W, 40 mTorr pressure and a gas combination of Ar (10 sccm) and SF6 (10 sccm), which was
optimized in a previous work [3]. The dimensions of the designed structures were channels with widths
from 6 to 9 microns and 5 microns depth. These dimensions were chosen in order to support a
fundamental mode at wavelengths near 1520 nm. A thin layer of RTP was grown using the LPE
technique at the end of fabrication process to act as a cladding for better light confinement, and also
serves to lower the propagation losses.
3. Results and discussion
3
Using the TSSG technique, we have obtained very high quality crystals with approx. 17x18x18 mm
dimensions without any cracks and inclusions. The same is applicable for epitaxial layers grown with
the LPE technique. Figures 1a) and 1b) show the RTP crystal and as grown (Yb,Nb):RTP/RTP
epitaxial layer. The refractive index contrasts between the epitaxy and the substrate ( Δni=ni,epi-ni,sub
being i=x,y and z) are: Δnx=-0.004, Δny=0.0003 and Δnz=0.005 allowing only monomode propagation
in the TM polarization by choosing the appropriate channel waveguide dimensions. We have
evaluated the Ti, Ni, Al and Cr elements as possible candidates for the metal mask by checking the
adhesion of these metals to the RTP surface. The topography of the metal layer, analysed by AFM
technique, showed average rms roughness of: 2.8 nm, 2.6 nm and 14 nm for Ti, Ni and Al layers,
respectively. The adhesion and durability of the metal layer on RTP surface, was checked by several
tape test, and Aluminium shows the better adhesion. With RIE, a maximum etch rate of 8.5 nm/min for
the epitaxial layer was obtained, and the deepest etch achieved was 2.8 m. Figure 2a) shows an
ESEM image of a part of the MZI design etched on an epitaxial layer. The Liquid phase epitaxial
growth of cladding shows a clear interface of growth, as shown in figure 2b).Optical waveguiding in the
fundamental mode at a wavelength of 1520 nm was observed in the above mentioned MZI and Ysplitter rib waveguides with an etch depth of 2.8 m.
Fig.1: a) RTP single crystal, b) as grown (Yb,Nb):RTP/RTP epitaxial layer.
Fig. 2: a) ESEM image of the input section of MZI fabricated on (Yb, Nb): RTP/RTP; b) cross sectional view of MZI.
4. Conclusions
Reactive ion etching was used to fabricate Y-splitters and MZIs on (Yb,Nb):RTP/RTP(001) samples.
The maximum etch rate that we achieved with epitaxial layer was 8.5 nm/min and the maximum
channel depth obtained was 2.8 microns. A thin cladding layer was grown over the channels for better
confinement. These devices were designed to support fundamental mode of 1520 nm and the MZIs
are expected to operate as modulators by using the E-O coefficient of RTP. Further investigation on
this is in progress.
5. Acknowledgments
This work was supported by the Spanish Government under Projects MAT2011-29255-C02-02,
TEC2010-21574-C02-01, TEC2010-21574-C02-02, by the Catalan Authority under Project
2009SGR235 and by the European Union under Project No. FP7-SPA-2010-263044. M. Ali Butt
thanks the Catalan Government for the FI-DGR fellowship 2012FI-B 00192.
References
[1].M.N. Satyanarayan, A. Deepthy, and H.L Bhat, ‘Potassium titanyl phosphate and its isomorphs: Growth,
properties, and application,’ Crit. Rev.Solid State Matter. Sci., vol. 24, no. 2, (1999) 103-191.
[2].X. Mateos, V. Petrov, A. Peña, J.J. Carvajal, M. Aguiló, F. Díaz, P. Segonds and B. Boulanger,’’Laser
3+
5+
operation of Yb in the acentric RbTiOPO4 codoped with Nb ’’, Opt.Lett.32(13),(2007), 1929-1931.
[3]. A. Choudary, J. Cugat, K. Pradesh, R. Solé, F. Díaz, M. Aguiló, H.M.H. Chong and D.P. Shepherd, ‘’Singlemode rib waveguides in (Yb,Nb):RbTiOPO4 by reactive ion etching’’, J. Phys. D: Appl. Phys. 46 (2013), 145108
(6pp).
Ni-doped karrooite yellow-orange ceramic pigments
prepared by ceramic and citrate gel routes
*
M. Llusar , E. García, M.T. García, C. Gargori, J. A. Badenes y G. Monrós
Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, 12071, Castellón, Spain
*[email protected]
1. Introduction and objectives
3+
2+
3+
2+
M1
2+
3+ M2
Titanium pseudobrookites (M 2(1-x)M xTi1+xO5 or [M ,M ,Ti] [Ti,M ,M ] 2O5, i.e. FeTi2O5,
MgTi2O5, Fe2TiO5, Al2TiO5, Cr2TiO5, Ti3O5, etc.) are isostructural phases with orthorhombic symmetry
(Cmcm spatial group) and a high structure flexibility to accommodate different chromophore metals in
their two different and distorted octahedral cationic sites, M1 or A (4c) and M2 or B (8f) [1]. Indeed,
some patents about yellow pigments based on Ti pseudobrookites have been already developed in
the last decades (Rademachers, Hund, Katamoto, Suzuki; 1977-2003) [2], although they were
basically prescribed for low-temperature applications (paints, plastics, resins, etc).
This extraordinary structural versatility of Ti pseudobrookites, along with their high refractoryness
(1650ºC) and refractive indexes (2.35-2.42), has also driven some investigations on their possible
application as host structures for ceramic pigments. For instance, Matteucci et al [3] studied recently
the crystal structure and optical properties of ceramic pigments based on Mg-Ti pseudobrookite
(karrooite) Mg1-xM2xTi2-xO5 solid solutions prepared by the conventional ceramic route (1200-1400ºC;
IV
IV
2+
3+
3+
2+
2+
M = V , Cr , Mn -Mn , Fe , Co or Ni ), and found that they were mostly stable in lowtemperature (≤1050°C) ceramic glazes and glassy coatings. In the case of Ni doping, quite intense
yellow colorations with a certain orange cast were obtained (L*/a*/b* values of 73.7/8.1/39.8 for
powders with 10 mol-% Ni). However, only two compositions were analyzed (x = 0.02 and 0.05) and
neither the solid solution limit of Ni in MgTi2O5 karrooite nor the possible tuning of the yellow-orange
color shade and intensity by Ni-doping were investigated.
With all the above precedents, solids solutions of Ni in MgTi2O5 pseudobrookite (karrooite) prepared
by the ceramic method have been herein investigated in depth for the first time aiming to develop new
yellowish-orange ceramic pigments. In addition, it has been also analyzed the effect of using a more
homogeneous and reactive metalorganic decomposition route (MOD or citrate gel) [4] on the
crystallization, microstructure, stability and coloring performance of Ni-MgTi2O5 solid solutions. To this
respect, the decomposition (combustion) of citrate-based coprecipitates or polymeric xerogels leads to
the formation at lower temperatures of more homogeneous multicomponent powders (mixed oxides),
which often exhibit nanostructured (submicronic) morphologies [4a-b], which are demanded to fulfill
the requirements of ceramic inks used in the new (ink-jet) decoration technologies of ceramic tiles [5].
2. Experimental and Results
Ni-Karrooite solid solutions (Mg1-xNixTi2O5, 0≤x≤1) were prepared by the conventional ceramic method
and also by a citrates gel metalorganic route [4], using rapid firing conditions (5ºC/min-heating and 3hsoaking) up to a maximum temperature between 800-1500ºC. Fired pigments were characterized by
XRD, SEM/EDX, UV-vis-NIR and color measurement (CIE-L*a*b*) techniques.
According to XRD results, the solid solubility of Ni in karrooite was only partial and strongly
temperature-dependent: around 40 mol-% of Ni at 1200ºC and 60-65 mol-% at 1400ºC, irrespective of
2+
IV
the preparation route. Thus, it seems that Ni doping reduces to some extend Mg /Ti cation disorder
and the entropy-stabilization of MgTi2O5 pseudobrookite with respect to the most stable ilmenite
2+
(MgTiO3) and rutile (TiO2) phases. Optical absorptions of Ni ions in distorted octahedral sites of
karrooite produced intense yellowish-orange colors, increasing saturation (lower L*) and chroma
(higher red –a*- and yellow –b*- hues) with temperature and Ni doping (Fig. 1a-b). These pigments
developed nice yellow colorations once enameled (5 wt-%) within low temperature (1000-1050ºC)
ceramic glazes (Fig. 1c-d), being much less stable in a Ca- and Zn-enriched glaze (glaze A).
Noteworthy, the citrate MOD route enabled the stabilization of Ni-karrooite solid solutions at lower
temperatures (1000ºC, 20 mol-% of Ni) and produced finer-grained powders with slightly more intense
orange hues (L*/a*b* color parameters of 1400ºC-fired powders for x=0.6 were 61.4/24.7/45.9 and
62.3/23.9/51.3 for ceramic and MOD-citrate samples, respectively). However, the yellow color of
enameled samples was very similar in both routes (L*/a*/b* values for 1400ºC-fired powders with
x=0.6 were 60.0/10.8/51.6 and 59.2/9.9/49.7 for ceramic and MOD-citrate samples, respectively).
3. Acknowledgments
The authors would like to acknowledge the financial support provided by the Spanish “Ministerio the
Economía y Competividad” (MAT2012-36988-C02-01 project).
x=0
x = 0.1
x = 0.2
x = 0.4
x = 0.5
x = 0.6
x = 0.7
x = 0.1
x = 1.0
1000ºC/3h
(direct)
x = 0.2
x = 0.4
x = 0.7
x = 1.0
1200ºC
(Glaze A)
1200ºC/3h
(direct)
1200ºC
(Glaze B)
1400ºC/3h
(refired)
x=0
x = 0.1
x = 0.2
x = 0.4
1400ºC/3h
(direct)
x = 0.5
x = 0.6
x = 0.8
x = 1.0
x = 0.1
x = 0.2
x = 0.4
x = 0.5
x = 0.6
x = 0.7
x = 1.0
x = 0.7 x = 0.8(d) x = 1.0
1400ºC
(Glaze B)
1500ºC/3h
(direct)
x = 0.6
x=0
x = 0.6
x = 0.8
x = 1.0
(c) Ceramic route
(a) Ceramic route
x= 0
x= 0.1
x= 0.2
x= 0.4
x= 0.6
x=0
x = 0.1
x = 0.2
x = 0.4
x = 0.6
1000ºC
(Glaze B)
800ºC
1000ºC
1200ºC
(Glaze B)
1200ºC
Ni-MgTiO3
+ Ni-TiO2
1400ºC
Ni-MgTi2O5 (Glaze B)
1400ºC
(b) MOD-Citrate route
(d) MOD-Citrate route
Fig. 1: Color evolution of fired powders (a and b) and 5 wt-% enameled samples (c and d) corresponding to
Mg1-xNixTi2O5 karrooite compositions prepared by the ceramic (a and c) and MOD-Citrate routes (b and d).
Referencias
[1]
[2]
[3]
[4]
[5]
a) L. Pauling, “The crystal structure of pseudobrookite”, Z Kristallogr, 73 (1930), 97-112; b) S. Akimoto, T.
Nagata, T. Katsura, “The TiFe2O5-Ti2FeO5 solid solution series”. Nature, 179, (1957), 37-38; c) G. Bayer,
“Thermal expansion characteristics and stability of pseudobrookite-type compounds, Me3O5”. J LessCommon Metals, 24 (1971), 129-138; d) J.F.W. Bowles, “Definition and range of composition of naturally
occurring minerals with the pseudobrookite structure”. Am Mineral, 73, (1988), 377-383.
a) J. Rademachers, H. Erfurth, F. Hund, “Metal additions to pigments of pseudobrookite-titanium dioxide
structure”. US patent 4,036,662, (1977); b) F. Hund, W. Holznagel, H. Erfurth, F. Kindervater, W. Hennings,
“Temperature-stable inorganic yellow pigments”. US patent 4,084,984, (1978); c) T. Katamoto, M. Fujimoto,
“Heat-resistant yellow pigment with pseudobrookite structure of the formula Fe(2-p-q-r-s)Li(p)Mg(q)Al(r)
Ti(s)O5”. European Patent 949, 2022, (1999); d) T. Suzuki, K. Kataoka, “Titanium-iron based composite
oxide pigment and method for production thereof”. US patent 6,540,824, (2003).
F. Matteucci, G. Cruciani, M. Dondi, G. Gasparotto, D.M. Tobaldi, “Crystal structure, optical properties and
colouring performance of karrooite MgTi2O5 ceramic pigments”. J Solid State Chem, 180, (2007), 31963210.
a) C. Gargori, R. Galindo, S. Cerro, M. Llusar, A. García, J. Badenes, G. Monros, “Ceramic pigments based
on chromium and vanadium doped CaTiO3 perovskite obtained by metal organic decomposition (MOD)”. Bol
Soc Esp Ceram Vidr, 51 (2012), 343-352; b) M. Blosi, S. Albonetti, M. Dondi, A.L. Costa, M. Ardit, G.
Cruciani, “Sol-gel combustion synthesis of chromium doped yttrium aluminum perovskites”. J Sol-Gel Sci
Technol, 50 (2009), 449-455; c) R.D. Purohit, S. Saha, “Synthesis of magnesium dititanate by citrate gel
route and its characterization”. Ceram Int, 25 (1999), 475-457.
G. Monrós, J.A. Badenes, A. García, M.A. Tena, en “El color de la cerámica: Nuevos mecanismos en
pigmentos para los nuevos procesados de la industria cerámica”, pp. 146-179, ed. Universitat Jaume I,
Castelló de la Plana, 2003 (ISBN 84-8021-449-X).
Oral communication
About the degradation of Na2SiF6:Mn4+ phosphor for
WLED applications
Anthony Barros
1,2,
1.
2.
2
2
1
, Geneviève Chadeyron , Philippe Boutinaud , Rodolphe Deloncle ,
1
3
Jérôme Deschamps , Rachid Mahiou
RevLum SAS, 8 rue des Frères Lumière, 63100 Clermont-Ferrand, France
Clermont Université, ENSCCF, Institut de Chimie de Clermont-Ferrand, BP 10187, 63174 Aubière Cedex, France
3. CNRS, UMR 6296, Institut de Chimie de Clermont-Ferrand, BP 80026, 63171 Aubière Cedex, France
 [email protected]
4+
It has been shown recently that the red luminescence of Mn ions in fluorides could be of interest for
4+
the WLED technology [1-3]. In compounds like Na2SiF6 or K2SiF6, for instance, the Mn ion
experiences a strong crystal field resulting in a sharp and intense red emission (≈ 620 nm) from the
2
4
Eg state upon blue excitation (≈ 420 – 460 nm) in the T2g multiplet (Fig. 1). However, when these
phosphors are exposed to air atmosphere for a few tens of hours at 200°C, severe degradation of their
optical properties is observed (Fig. 1). This drawback limits significantly their applicability in LED
devices. The purpose of the present work is to investigate the origin of these degradations and finalize
a chemical treatment that could improve the durability of the phosphors in the device. Results in X-ray
diffraction, ESR, NMR (Si, F), FTIR and optical spectroscopy will be presented in this connection.
Fig. 1: Na2SiF6 : Mn4+ before and after aging at 200°C during 2 days in air atmosphere.
References
[1] E. V. Radkov, L. S. Grigorov, A. A. Setlur, A. M. Srivastava, United States Patent Application
US2006/0169998 A1.
[2] M. G. Brik, A. M. Srivastava, Journal of Luminescence, 133, 2013, 69.
[3] Yan Kai Xu, Sadao Adachi, Journal of Applied Physics, 105, 2009, 013525.
Conferencia oral
Synthesis and deposition of CZTS nanoparticles
using a solvothermal method
1,*
1
1
1
1
1
Ivan Calvet , Rafael Martí , Diego Fraga , Aitor Rey , Ester Barrachina , Radostina Dimova ,
1
1
Teodora Stoyanova and Juan B. Carda
1. Departamento de Química Inorgánica y Orgánica, Universitat Jaume I de Castellón
*[email protected]
1. Introduction
Nowadays the development of solar photovoltaic renewable energy has increased rapidly , due to an
higher demand of cleaner energy consumption. Chalcogenides are important semiconductors,
presenting unique optical, electrical and chemical characteristics. Due to this wide range of properties,
in the last years chalcogenides have attracted the attention of the scientific community, particularly in
thin films technology, being heavily promoted by the growing interest in CIGS and CZTS -­‐ based solar
cells. Several chemical routes have been studied for CZTS synthesis like hot injection, sol-gel,
electrodeposition, and so on [1]
The Cu2ZnSnS4 system (CZTS), which crystallizes in the Kesterite structure, is one of the most
promising materials for thin films, because it has a "band gap" of 1.5 eV and a high absorption
4
-1
coefficient (10 cm ). Also, such a system is sustainable and environmental friendly due to the
absence of toxic elements, together with a significant cost savings due to the incorporation of low cost
and abundant raw materials (Zn and Sn). The as-synthetized CZTS nanoparticles could be used in the
form of ink and could be coated on a ceramic substrate in order to obtain a photovoltaic device which
provides added value to the traditional ceramic tile. [2-5].
In this work, it has been studied the synthesis of Cu2ZnSnS4 by a facile solvothermal method. In order
to improve the preparation procedure different precursors and thermal treatments were studied.
Stoichiometric composition, structure, morphology and absorption characteristics of CZTS
nanoparticles were analyzed. Moreover, it has been studied different organic solvents to form a stable
ink of CZTS. The obtained ink was deposited on the ceramic substrate and the heat treatment used
was set in an chalcogenides atmosphere for obtaining the final compound. The materials were
analyzed via X-ray diffraction (XRD), Scanning electron microscopy (SEM) coupled with Energy
dispersive X-ray analysis (EDAX), Surface profiler (SP) and etc. in order to clarify their properties.
References
[1] David B.Mitzi , Oki Gunawan,Teodor K.Todorov,Kejia Wang,Supratik Guha, The path towards a
high-performance solution-processed kesterite solar cell, Solar Energy Materials & Solar Cells, 95,
pp.1421–1436 (2011)
[2] S.Delbos, Kesterite thin films for photovoltaics: a review, EPJ Photovoltaics 3, pp.35004 (2012)
[3] C.P. Chan, H. Lam, C. Surya, Preparation of Cu2ZnSnS4 films by electrodeposition using ionic
liquids, Solar Energy Materials Solar Cells, 94, pp.207-211 (2010)
[4] W. Xinkun, L. Wei, C. Shuying, L. Yunfeng, J. Hongjie, Photoelectric properties of Cu2ZnSnS4 thin
films deposited by thermal evaporation, Journal of Semiconductors, 33, 022002 (2012)
[5] T.K Todorov, J.Tang,S.Bag, O.Gunawan, Y.Zhu, D.B.Mitzi, Beyond 11% Efficiency: Characteristics
of State-of-the-Art Cu2ZnSn(S,Se)4 Solar Cells, Advanced Energy Materials 3 pp.34-38 (2012)
oral
Eco-energy lighting based on the combination of
LEDs withOrganic Phosphors
1
1,*
1
1
Rachod Boonsin , Genevière Chadeyron , Jean-Philippe Roblin , Damien Boyer et
1,2
Rachid Mahiou
1. Clermont Université, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 CLERMONT-FERRAND
2. CNRS, UMR 6296, Institut de Chimie de Clermont-Ferrand, BP80026, F-63171 AUBIERE
*[email protected]
Introduction
Nowadays, the lighting market has a main concern about the effect of products toward the
environment. The present technology has become obsolete: high energy consumption (incandescent
bulbs) and high toxic substances (compact fluorescent light bulbs). Therefore, several strategies have
been investigated to overcome these drawbacks [1-4]. One of the most promising approaches is the
system based on white light-emitting diodes (WLEDs) obtained by combining a blue and/or UV LED
with some phosphors in order to achieve the specifications of public lighting (low energy consumption,
long lifetime, etc.). However, the phosphors used in LEDs involve rare-earth elements with very
inconstant fares since China is the leader of the production of these latters (97%). Hence, the rareearth-free organic phosphors become an alternative solution because of their high luminous efficiency,
low cost of production, and several ways to tune the colors by playing with their functional groups.
In this work, we have synthesized three rare-earth-free organic phosphors based on 2,6diméthyl-4-pyrone [5] and Schiff base ligand [6]. Herein we describe the synthesis procedures and we
present the morphological and optical characterizations. The optical performances of these organic
phosphors upon ultraviolet and blue excitations will be discussed.
Acknowledgement
This work is financially supported by the Regional Council Auvergne (FRANCE).
References
[1] S.-Y. Kwak, S. Yang, N.R. Kim, J.H. Kim, B.-S. Bae, “High color rendering White light-emitting diodes base
don a Green silicate phosphor mixed with a red dye-bridged hybrid”. The Royal Society of Chemistry
Advances, 2, (2012), 12371-12377.
[2] T. Jüstel, H. Nikol, C. Ronda, “Periodic table of the lighting elements”. Angewandte Chemie International
Edition, 37, (1998), 3084-3103.
[3] D.-H. Hwang, J.-D. Lee, H.J. Cho, N.S. Cho, S. K. Lee, M.-J. Park, H.-K. Shin, C. Lee, “Organic white lightemitting diodes using a new DCM derivative as an orange-red doping molecule”. Synthetic Metals, 158,
(2008), 802-809.
[4] S.-T. Lim, M.H. Chun, K.W. Lee, D.-M. Shin, “Organic light emitting diodes with red emission using (2,6dimethyl-4H-pyran-4’ylidene)malononitrile moiety”. Optical Materials, 21, (2002), 217-220.
[5] L.L. Woods, “Some further reactions of 2,6-dimethyl-4-pyrone”. Journal of the American Chemical Society,
80, (1958), 1440-1442.
[6] Z.-C. Chuan, Z.-Y. Yang, Y. Li, B.-D. Wang, Q.-X. Zhou, “A simple structure fluorescent chemosensor for
high selectivity and sensitivity of aluminium ions”. Dyes and Pigments, 97, (2013), 124-128.
Estudio de nano-pigmentos basados en TiO2
dopado con Cr y Sb para su aplicación en
tecnología inkjet
Marc Jovani, Maria Domingo, Thales Machado, Héctor Beltrán Mir, Eloísa Cordoncillo*
1
Departamento de Química Inorgánica y Orgánica, Universitat Jaume I de Castellón, Campus del Riu Sec, E-12071,
Castellón de la Plana, Spain
* [email protected]
El dióxido de titanio es un material multifuncional con un gran número de aplicaciones (pinturas,
cremas, pastas de dientes, pigmentos etc). Actualmente el campo de la nanotecnología ha
despertando un gran interés debido a las nuevas aplicaciones que puede generar. En este
sentido, y más estrechamente en el sector de los nano-pigmentos, el TiO2 tiene un gran
número de aplicaciones. El uso de nanopartículas para incorporarlas como pigmentos en
impresoras inkjet va a resolver algunos problemas surgidos actualmente.
La denominada “química suave” en la síntesis de nanopartículas, es usada en gran medida no
solo por su sencillez, sino también por la posibilidad de control de las características de las
nanopartículas, modulando los parámetros de reacción.
En este estudio, se han obtenido nanopartículas del pigmento basado en TiO2 dopado con
Cr(III) y Sb(III,V) mediante métodos solvotermales a partir de microemulsiones. Se ha obtenido
fase única de rutilo y anatasa a bajas temperaturas, así como partículas esféricas, controlando
los parámetros de reacción tales como el pH, temperatura, tiempo de reacción, cantidad de
cromóforo etc. Las coloraciones obtenidas de estas nanopartículas obtenidas a temperaturas
inferiores a 200ºC fueron semejantes a las de los pigmentos industriales obtenidos a altas
temperaturas (>1100ºC) obtenidas por el método cerámico.
Los nano-pigmentos obtenidos, tanto por su coloración
como por su morfología, son
potencialmente utilizables en la industria inkjet, pudiendo eliminar actuales problemas del
método utilizado en la industria cerámica (aglomeración, inestabilidad etc.), así como
reduciendo costes con la eliminación de algunas etapas como la de molturación para la
obtención de tamaños pequeños de partícula.
A novel series of [(CH3CH2CH2)4N][M(N(CN)2)3]
(M: Mn2+, Fe2+, Co2+, Ni2+, Cd2+) perovskite-like
coordination polymers with dielectric properties
Juan Manuel Bermúdez-García1,*, Manuel Sánchez-Andújar1, Susana Yáñez-Vilar2,
Jorge Mira2, Alfonso Fondado2, Jorge López-Beceiro3, Ramón Artiaga3,
Socorro Castro-García1 and María Antonia Señarís-Rodríguez1
1. Dpt. Fundamental Chemistry, University of A Coruña, Campus A Coruña, 15071 A Coruña, Spain
2. Dpt. Applied Physics, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
3. Dpt. Industrial Engineering II, University of A Coruña, Campus Ferrol, 15403 Ferrol, Spain
*[email protected]
1. Introduction
Perovskite materials exhibit a general formula ABX3, where A are lanthanides, alkaline earth
metals or similar cations, B are transition metals cations and X can be different types of anions
as O2-, S2-, halides or, even, polyatomic ligands. As it is well-knwon the perovskite structure can
be defined as a tridimensional network of [BX6] octahedra sharing corners, with the A cations
situated in the resulting cubooctahedral cavities.
Traditionally, the studies about perovskite compounds have focused on inorganic materials,
mainly transition metal oxides of general formula ABO3, which constitute a wide class of
compounds that display an amazing variety of interesting properties. This perovskite family
encompasses insulators, piezoelectrics, ferroelectrics, semiconductors, magnetics,
superconductors, multiferroic and magnetoresistive materials.
Much less effort has been devoted to the study of hybrid inorganic-organic compounds and
coordination polymers with perovskite-like structure that contain organic or inorganic polyatomic
ligands in the X position. Nevertheless, these compounds are attracting increased attention in
view of the interesting functional properties they can display. In this context, a new series of
perovskite-like materials with general formula [G][M(HCOO)3] have been mainly studied due to
their interesting magnetic, dielectric and even multiferroic properties.1,2 From the structural point
of view, all these compounds have 3D-structures consisting on [M(HCOO)3]- frameworks (where
M2+ is typically a 3d transition metal cation) counter-balanced by alkylammonium cations [G]
located in the pseudocubooctahedral cavities and hydrogen-bonded to the framework. The size,
shape and charge of the alkylammonium cations, acting as templates, determine the topology of
the framework.
Such [G][M(HCOO)3] compounds are very adequate to study important functional properties,
just as for example magnetic and dielectric properties. In this context, the 3D-structure of their
framework is adequate to get long-range magnetic coupling of the metal cations, while the
presence of disordered alkylammonium cations inside the pseudocubooctahedral cavities allow
the appearance of dielectric properties.3
Figure 1.-Perovskite-like structure of [G][M(N(CN)2)3] (G: tetrapropylammonium, M: Mn2+, Ni2+, Fe2+, Co2+, Cd2+).
Recently, we have focused on the coordination polymer perovskites of general formula
[G][M(N(CN)2)3] with dicyanamide N(CN)2- as ligand which bridged M2+ (transition metal cations)
forming a [M(N(CN)2)3]- framework and alkylammonium cations [G] located in the cavities
(see figure 1). In the literature, the crystal structure and the magnetic properties of several
dicyanamide perovskites have been reported but to our knowledge the dielectric behavior of
these compounds has not been reported.
It is the case of [(CH3CH2CH2)4N][M(N(CN)2)3] (M= Mn2+(1) and Ni2+(2)) compounds, whose
synthesis, crystal structure and magnetic properties were reported by Schlueter et al. 4 These
authors reported that the Ni2+(2) compound shown two structural transitions at 160 K and 210 K,
which are due to a transformation from a centrosymmetric (Pnna) to a non centrosymmetric
space group (P-421c). The Ni2+(2) compound shows an orthorhombic symmetry (space group
Pnna) at T> 210 K and T<160 K and a tetragonal symmetry (space group P-421c) in the
temperature range of 160<T(K)<210.
In the present work, and for the first time, we report the dielectric response of the series
[(CH3CH2CH2)4N][M(N(CN)2)3] with M= Mn2+(1) Ni2+(2), Fe2+(3), Co2+(3), and Cd2+(5) containing
tetrapropylammonium cations. Also, we deep in the structural and dielectric characterization of
this novel series of perovskite-like compounds. It should be remarked that Fe2+(3), Co2+(4) and
Cd2+(5) compounds have been synthesized for the first time in this work and that we also have
found a new phase for the Mn2+(1) compound at 368 K, and two new phases for the described
Ni2+(2) compound at 323 K and 368 K, respectively.
In addition, we have observed that the structural transitions induce dielectric anomalies in all of
these compounds. We suggest that a displacement of the tetrapropylammonium cations inside
the pseudocubooctahedral cavities and a disorder in the dicyanamide anions are involved in the
dielectric and structural transitions.
2. Conclusions
In summary, we have synthesized and characterized a novel series of
[(CH3CH2CH2)4N][M(N(CN)2)3] (M: Mn2+, Ni2+ Fe2+, Co2+, Cd2+) compounds which have several
structural transitions. These structural changes are due to the tetrapropylammonium cations
displacement inside the pseudocubooctahedral cavities and the disorder of the dicyanamide
anions, that induce dielectric transitions in these materials.
3. Acknowledgments
The authors are grateful for financial support from Ministerio de Economía y Competitividad
(MINECO) (Spain) and EU under project FEDER MAT2010-21342-C02-01
4. References
[1]
[2]
[3]
[4]
P.Jain, V, Ramachandran, R.J. Clark, H. D. Zhou, B.H. Toby, N.S. Dalal, H.W. Kroto, A.K. Cheetham,
“Multiferroic Behavior Associated with an Order−Disorder Hydrogen Bonding Transition in
Metal−Organic Frameworks (MOFs) with the Perovskite ABX3 Architecture”. Journal of the American
Chemical Society, 131, (2009), 13625-13627
W. Li, Z. Zhang, E.G. Bithell, A.S. Batsanov, S. Andrei, P.T. Barton, P.J. Saines, J. Paul, P. Jain,
C.J. Howard, M.A. Carpenter, A.K. Cheetham, “Ferroelasticity in a metal–organic framework
perovskite; towards a new class of multiferroics”. Acta Materialia, 61, 13, (2013), 4928-4938.
M. Sánchez-Andújar, S. Presedo, S. Yáñez-Vilar, S. Castro-García, J. Shamir,
M.A. Señarís-Rodríguez, “Characterization of the Order−Disorder Dielectric Transition in the Hybrid
Organic−Inorganic Perovskite-Like Formate Mn(HCOO)3[(CH3)2NH2]”.Inorganic Chemistry, 49,
(2010), 1510-1516.
J.A. Schlueter, J.L. Manson, U.Geiser, “Structural and Magnetic Diversity in Tetraalkylammonium
Salts of Anionic M[N(CN)2]3- (M = Mn and Ni) Three-Dimensional Coordination Polymers”. Inorganic
Chemistry, 44, (2005), 3194-3202.
Comunicación Oral
Lead halide perovskites as light harvesters materials
for solar cells
Emilio J. Juárez-Pérez, Victoria Gonzalez-Pedro, Iván Mora-Sero, Juan Bisquert
Photovoltaics and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain
Email: bisquert@uji.
1. Introduction
Recently, a new type of
photovoltaic cells with lead
halide perovskites as light
harvester materials have
rised onto the scene
receiving great attention in
the scientific community. It
is due mainly because a
fast succession of record
devices in a short time
period, which it is now
reaching above of 16 %
power conversion efficiency
(PCE).[1]
The
lightabsorbing
semiconductor
material is based on a
hybrid (organic/inorganic)
halide
perovskite
polycrystalline
structure
with formula AMX3, where A
is a small organic cation
Figure 1
(methylammonium,
2+
2+
formamidinium), B is a metal cation (Pb , Sn ) and X is a halide element (I, Cl, Br, or a combination
of some of them). Lead halide perovskites have been used as light harversters since 2008 when
Miyasaka et al.[2] reported that these materials could be an alternative to binary chalcogenide based
quantum dots sensitized cells. However, the liquid electrolyte used as hole transport layer rapidly
degraded the active material of sensitized cell. The breakthrough in efficiency (9.7%) and stability (>
500 hours) was done by Park and collaborators in 2012 by replacing the liquid electrolyte by a solid
one, the spiro-OMeTAD,[3] see Figure 1.a for a general schema of the device. At the same time,
Snaith et al. assembled devices whose active layer was deposited inside an insulator scaffold material
as Al2O3 reached PCE profiles of 10.9%[4] meaning that the harvesting material itself conduct the
generated photocurrent. Later, the same group reported planar heterojunction devices without
mesoporous layer reaching even higher PCE. Therefore, the proficient operation of the APbX3
perovskite solar has been accomplished by many different approaches pointing out for an underlying
robust photovoltaic operation mechanism.
2. Easy manufacture of solid state photovoltaic devices using wet methods
An interesting aspect of the manufacture of these photovoltaic devices is that the active material is
solution processable using common lab solvents and the active layer can be deposited using spin
and/or dip coating procedures at room conditions without employ vacuum techniques. Scheme 1
summarizes the current main methods used for perovskite deposition and Figure 1.b depict the stepby-step process to assemble a lab prototype device. It is important to note that from the point of view
of the manufacturing the sequential method offers a more efficient use of the reagents and
economically feasible techniques to produce cells at industrial scale. It consists of a first stage of spincoating a concentrated PbI2 solution in a mesoporous layer of TiO2 followed by a second stage of dipcoating the substrate in the organic salt solution or atmospheric vapour deposition (VASP process) to
synthesize in situ the hybrid halide perovskite. The configuration stacks currently reported include the
normal and the inverted configurations using glass or plastic substrates which reflect versatility of this
solar harvesting material for photovoltaic applications. Furthermore, different halide elements have
Comunicación Oral
been combinated in different proportions to tailor the Voc of the device. Also, different organic cation
counterpart and first attempts to replace Pb by Sn are being reported.[5]
Scheme 1: Main active layer deposition methods for hybrid halide lead perovskites.
3. Impedance Spectroscopy: characterization to improve perovskite photovoltaic devices.
An understanding of the mechanisms of transport and accumulation of charges and working principles
is highly mandatory to assess the possibilities and properties of these materials.[6] Therefore, for
further development of these photovoltaic devices it is required to determine the fundamental
operational mechanism of the different layers constituting the device. For example, to obtain a deeper
insight of the role of selective contact in the performance of perovskite solar cells, impedance
spectroscopy (IS) is a technique capable to discriminate between the different components of the
device and consequently it is able to provide abundant and useful information on the device working
mechanism. IS determined recently that both electron- and hole- selective contacts significantly affect
the solar cell performance playing three major roles: transport resistance at the selector layer, chargetransfer rate at the interface and control the recombination resistance in the perovskite layer.[7] The
most important parameter characterizing the active layer of a solar cell is the diffusion length, it plays a
key role in the photovoltaic performance of perovskite solar limiting the useful active layer thickness.
Because IS spectra of perovskite based full devices show the transmission line feature, diffusion
length, carrier conductivity and recombination resistance can be straightforwardly extracted.[8]
4. Conclusions
Over a short period of research time there have been scientific teams looking for the highest
efficencies, novel cell architectures or diving in the mechanisms of transport and accumulation of
charges for the halide perovskite based solar cells. A fast, cheap, unsupervised batch-wise operation
and non-invasive technique to characterize full devices is mandatory to overcome in the next years
the plethora of promising active materials and configurations paralleling the properties of the hybrid
halide perovskites for photovoltaics applications. Impedance spectroscopy meets these requeriments
and will help to reach the efficiency limits of these light harvesting materials.
5. Acknowledgments
This work was supported by Generalitat Valenciana (ISIC/329 2012/008) and Universitat Jaume I
project 12I361.01/1.
Referencias
[1] NREL best cell efficiencies. http://www.nrel.gov/ncpv/images/efficiency_chart.jpg visited on 13/03/2014
[2] A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, J. Am. Chem. Soc. 2009, 131, 6050-6051.
[3] H.-S. Kim, C.-R. Lee, J.-H. Im, K.-B. Lee, T. Moehl, A. Marchioro, S.-J. Moon, R. Humphry-Baker, J.-H. Yum,
J. E. Moser, M. Gratzel, N.-G. Park Nat. Sci. Rep. 2012, 2, 591-7.
[4] M. M. Lee, J. Teuscher, T. Miyasaka, T. N. Murakami, H. J. Snaith, Science 2012, 338, 643-647.
[5] H.-S. Kim, S. H. Im, N.-G. Park, J. Phys. Chem. C DOI: 10.1021/jp409025w
[6] H.-S. Kim, I. Mora-Sero, V. Gonzalez-Pedro, F. Fabregat-Santiago, E. J. Juarez-Perez, N.-G. Park, J.
Bisquert, Nature Communications 2013, 4, 2242.
[7] E. J. Juárez-Pérez, M. Wussler, F. Fabregat-Santiago, K. Lakus-Wollny, E. Mankel, T. Mayer, W.
Jaegermann, I. Mora-Sero J. Phys. Chem. Lett. 2014, 5, 680-685.
[8] V. Gonzalez-Pedro, E. J. Juarez-Perez, W.-S. Arsyad, E. M. Barea, F. Fabregat-Santiago, I. Mora-Sero, J.
Bisquert Nano Lett. 2014, 14, 888-893.
Comunicación Oral
Recubrimientos Nanométricos Funcionales
mediante Spray Pyrolysis
Mª Dolores Palacios*, J.Luis Amorós, Encarna Blasco y Sergio Mestre
Instituto de Tecnología Cerámica.
Asociación de Investigación de las Industrias Cerámicas.
Universitat Jaume I. Avda. Vicent Sos Baynat. s/n, 12006 Castellón. España.
*[email protected]
Se ha estudiado la formación de capas nanométricas sobre un sustrato cerámico partiendo de una
disolución o suspensión acuosa. La aplicación mediante aerografía de una disolución acuosa de una
sal de un metal sobre un sustrato caliente, en determinadas condiciones da lugar a una nanocapa,
que puede modificar las propiedades funcionales y/o estéticas la superficie cerámica. Este método de
deposición, convenientemente escalado, puede resultar más económico y más polivalente frente a
técnicas como la Deposición Química en fase Vapor (CVD) y la Deposición Física en fase Vapor
(PVD), que requieren un equipamiento más sofisticado.
Figura 1. Esquema básico de un sistema de spray pyrolysis.
Las disoluciones acuosas se formulan a partir de sales metálicas muy solubles en agua, como son los
nitratos de aluminio, cobre, cobalto, manganeso, hierro o plata entre otros. Para elementos, como el
titanio, del que no existe este tipo de sales fácilmente manipulables, se han tenido que sintetizar
complejos solubles en agua para tal efecto. El resultado son capas de óxidos de los elementos
precursores que modifican el aspecto y la microestructura de las superficies.
Se han estudiado las variables que influyen sobre el proceso de formacion de la nanocapa con el
objetivo de poder predecir los materiales que pueden depositarse sobre un determinado vidriado
cerámico, y en su caso las condiciones de operación necesarias para conseguir la nanocapa. En este
sentido, variables como la naturaleza del precursor líquido, la temperatura, naturaleza del vidriado, la
temperatura de aplicación o el volumen de precursor depositado, pueden resultar decisivas para
obtener la nanocapa, y a su vez influir sobre las propiedades estéticas y/o funcionales de la misma.
Este estudio ha permitido determinar los parámetros de los que depende la compatibilidad entre el
precursor y el sustrato, la formación de la nanocapa, así como generalizar la aplicación del proceso
gracias al conocimiento de las variables implicadas. Las ventajas serían la obtención de productos
cerámicos con un alto valor añadido a partir de productos económicos, ya que sólo se actuaría sobre
la superficie del vidriado, sin necesidad de que intervenga todo el espesor del mismo en los efectos
decorativos o propiedades funcionales adquiridas. Cabe considerar desde efectos decorativos, como
es el caso de los metalizados, lustres, etc, a nuevas propiedades funcionales: bactericida (basados
en capas que contengan Ag) o fungicidas (capas de CuO).
Comunicación Oral
Figura 2
Figura 3. Micrografía de un vidriado con una capa nanométrica de CuO.
Agradecimientos
Los autores agradecen al Ministerio de Economía y Competitividad el apoyo recibido al desarrollo de
la investigación (Plan Nacional de I+D, CTQ2011-28231)
Referencias
[1] J. M. Albella, “Láminas Delgadas y Recubrimiento. Preparación, propiedades y aplicaciones”. Madrid.
Edit. CSIC. 2003.
[2] S.M. Pawar, B.S. Pawar, J.H. Kim, O.-S. Joo, C.D. Lokhande, “Recent status of chemical bath
deposited metal chalcogenide and metal oxide thin films”. Current Applied Physics 11 (2011) 117-161.
[3] P. S. Patil, “Versatility of chemical spray pyrolysis technique” Materials Chemistry and Physics 59
(1999) 185-198.
[4] C.Luyo, I.Fábregas, L. Reyes, J. L. Solís, J. Rodríguez, W. Estrada, R. J. Candal, “SnO2 thin-films
prepared by a spray–gel pyrolysis: Influence of sol properties on film morphologies”. Thin Solid Films 516
(2007) 25–33.
[5] D.Wang, G. P. Bierwagen, “Sol–gel coatings on metals for corrosion protection”. Progress in Organic
Coatings 64 (2009) 327–338.
[6] G. Korotcenkova, S. D. Han, “Cu, Fe, Co, or Ni)-doped tin dioxide films deposited by spray pyrolysis:
Doping influence on thermal stability of the film structure”. Materials Chemistry and Physics 113 (2009)
756–763.
Variable-temperature IR spectroscopy for ranking
Brønsted acidity
*
Montserrat Rodriguez Delgado , Carlos Otero Arean
Department of Chemistry, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
*[email protected]
1. Introduction
Solid acids having a large specific surface area, such as protonic zeolites and related porous solids,
are often used as catalysts in a wide range of chemical processes, which span the petrochemical
industry, methanol to olefin conversion and the production of fine chemicals, to quote some of the
most common examples. The strength of their catalytically active Brønsted-acid sites is a main factor
determining performance of such porous solids; hence the need of having a reliable method to rank
surface acidity of solid acids.
However, at variance with aqueous acid solutions for which the corresponding pKa provides a
quantitative measure of acid strength, no clear-cut measurement has yet been found for solid acids.
The most common method currently being used relies on adsorption of a weak base (such as CO or
dinitrogen) which forms hydrogen-bonded OH···CO (or OH···NN) adsorption complexes with the
Brønsted-acid hydroxyl groups of the solid. The adsorption complex can easily be monitored by IR
spectroscopy as hydrogen bonding brings about a distinctive bathochromic shift, Δν(OH), of the O−H
stretching mode of the hydroxyl group. The magnitude of Δν (OH) (for any given weak base) is taken to
be an indicator of relative Brønsted acidity when ranking solid acids [1]. The question, however, arises
as to whether Δν(OH) really correlates with acid-base interaction energy or not. We report herein on
recent studies showing that such a correlation cannot be taken for granted.
2. Methods and results
Adsorption of CO and dinitrogen on several protonic zeolites belonging into different structural groups
was studied by means of variable-temperature IR (VTIR) spectroscopy [2] (which affords simultaneous
0
determination of Δν(OH) and standard adsorption enthalpy, ΔH ) and adsorption calorimetry. As an
example, results obtained for CO adsorption on H-FER and H-MCM-22 (MWW structure type) are
given in Figures 1 and 2. Corresponding results for other protonic zeolites (some of them taken from
the published literature) are summarized in Table 1.
-1
(OH) = -297 cm
2
3
4
5
6
7
8
9
0,1
-0,1
-0,2
-0,3
8
7
6
5
4
3
2
1
3605
3600
-1
(OH) = -320 cm
2 1
3
4
5
9
-1
1000/T (K )
4,0
B
0,1
0,0
4,5
5,0
5,5
6,0
4
ln {/[(1-)p]}
Absorbance
0,2
0,2
1
6
7
8
9
10
11
0,0
11
10
9
8
7
6
-0,1
2
0
0
H = -28,4 kJ mol
-2
3400
Wavenumber / cm
3200
-1
-1
3000
1
-0,2
-1
4,5
5
4
3
2
3625
3600
1000/T (K )
5,0
5,5
6,0
0
ln {/[(1-)p]}
A
Absorbance
0,3
3500
3400
-1
-2
-3
0
H = -22,5 kJ mol
-4
3300
3200
Wavenumber / cm
3100
-1
3000
-1
Fig. 1: (A) Representative variable-temperature IR spectra (O−H stretching region) of CO adsorbed on H-FER.
From 1 to 9, temperature goes from 167 to 224 K; and equilibrium pressure from 0.57 to 1.75 mbar. (B)
Representative variable-temperature IR spectra (O−H stretching region) of CO adsorbed on H-MCM-22. From 1
to 11, temperature goes from 154 to 214 K; and equilibrium pressure from 6.52 to 9.24 mbar. The spectra are
shown in the difference mode (zeolite blank subtracted). Insets show the corresponding van’t Hoff plots.
30
Table 1. Experimental data for CO hydrogen bonding in
protonic zeolites.
Structure -Δν(OH)
-ΔH0
Zeolite
Ref.
type
(cm-1)
(kJ mol-1)
H-Y
FAU
275
25.6
[3]
-1
Qdiff (kJ mol )
25
20
15
10
H-FER
H-MCM-22 first run
H-MCM22 second run
5
0
0,00
0,05
0,10
0,15
H-ZSM-5
MFI
303
29.4
[3]
H-FER
FER
297
28.4
[4]
H-MCM-22
MWW
320
22.5
This work
H-MCM-56
MWW
316
20
This work
0,20
Coverage ()
Fig. 2: Adsorption heat of CO on H-FER (squares) and
H-MCM-22 (circles) measured by calorimetry at 303 K, as
a function of coverage.
3. Discussion and Conclusions
Experimental results summarized in Table 1 clearly show that while for some protonic zeolites (H-Y,
0
H-FER and H-ZSM-5) there is a direct correlation between standard adsorption enthalpy (ΔH ) and
bathochromic shift (Δν(OH)) of the O−H stretching mode in the corresponding hydrogen-bonded
(OH···CO) adsorption complex, the same does not hold in the case of other zeolites. Thus, MWW
0
structure-type zeolites show a distinctively lower (absolute) value of ΔH (for CO adsorption) than HFER and H-ZSM-5; and yet the (absolute) value of Δν(OH) (after hydrogen bonding with the probe
molecule) is significantly larger for the protonic zeolites of the MWW group. Measurements performed
by using dinitrogen as the probe molecule confirmed the results obtained with CO, in the sense that a
0
direct correlation between Δν(OH) and ΔH was not always observed. Taken as a whole, the obtained
results clearly show that the usual practice of ranking Brønsted-acid strength of solids by their O−H
frequency shift probed by and adsorbed weak base can be misleading. Determination of the enthalpy
change involved in formation of the corresponding hydrogen-bonded adsorption complex seems to be
a more reliable instrumental method.
References
[1]
[2]
[3]
[4]
E.A. Paukshtis, E.N. Yurchenko. Russ. Chem. Rev., 52, (1983), 242.
E. Garrone, C. Otero Arean. Chem. Soc. Rev., 34, (2005), 846.
C.O. Arean. J. Mol. Struct., 880, (2008), 31.
P. Nachtigall, O. Bludsky, L. Grajciar, D. Nachtigallova, M.R. Delgado, C.O. Arean. Phys. Chem. Chem.
Phys., 11, (2009), 791.
Analysis of the growth conditions of nanoporous
GaN particles by Chemical Vapor Deposition
J. Mena*, J.J. Carvajal, O. Bilousov, F. Díaz, M. Aguiló
Física i Cristal•lografía de Materials i Nanomaterials (FiCMA-FiCNA) and EMaS, Universitat Rovira i Virgili (URV), Marcel•lí
Domingo, s/n, Tarragona, E-43007, Spain.
*[email protected]
1. Introduction
GaN is a promising material for optoelectronics applications but its big refractive index represents an
important disadvantage for the development of LEDs [1]. The classical approach used to solve this
problem has been the coverage of the material with a polymeric capsule with an intermediate
refraction index [2]. An alternative solution to increase the light extraction efficiency of GaN based
unencapsulated LEDs is the use of porous GaN [3]. The induced porosity in the material increases the
reflection probabilities of emitted photons, and provides additional surfaces through which photons can
escape.
Based on the studies developed by ourselves [4] we use a non etching approximation to produce
porous GaN using the direct reaction between metallic Ga and NH3 in a Chemical Vapor Deposition
(CVD) system, in one single step without requiring any post-growth treatment to induce the porosity.
In the present work we analyze morphologically and structurally the nanoporous GaN particles
obtained by the direct reaction between Ga and NH3 in a CVD system by exploring the effect of
different experimental conditions. The control of morphology, nanoporous density, and crystallographic
orientation of the GaN particles are important parameters for advanced light emitting applications.
2. Results and discussion
A set of experiments with three different shape holders for Ga were carried out to analyze how the
shape of the crucible affected the spreading of the Ga droplet, and how this affected to the final shape
and porosity of the particles obtained. The Ga holders used were a flat plate, a half cylindrical tube
and a concave crucible. The GaN particles obtained when using a flat plate or a half cylindrical tube
as Ga holders were similar, with sizes between 2-3 µm, and a similar degree of porosity. The particles
obtained using the concave crucible show bigger sizes (around 4 µm), and the pores seem to be
smaller in diameter and do not form ridges, giving a more rough aspect to the surface of the particles.
Three sets of experiments were carried out with the introduction of different amounts of Ga at the
beginning of the experiment (0.2 g, 0.4 g and 0.6 g), to analyze its effect on the coverage of the
substrate with nanoporous GaN particles, while keeping constant the other reaction parameters. When
0.2 g of Ga were used, a low degree of substrate coverage was observed with a particle size around
5-6 µm. A higher coverage of nanoporous GaN particles could be seen when 0.4 g of Ga were used.
In contrast with the previous case, the particle diameter was lower, of around 2µm. Finally, the GaN
particles grown using 0.6 g of Ga had a similar particle density and size with the experiment using 0.4
g of Ga. This would indicate that it exist a quantity of Ga above which no more GaN particles are
formed, probably related to the Ga/N ratio used.
We performed additional experiments to analyze the influence of the deposition time in the shape and
porosity of the GaN particles. The deposition times selected were 30, 45, 60 and 120 min. The
tendency is to have a higher coverage of the substrate as we increase the time, but above a certain
deposition time not only no more deposition was observed but decomposition of the previously formed
particles was evident due to the high temperature and low vacuum conditions used in the experiments.
To synthesize porous GaN on Si substrates, it is necessary to coat the substrate with a metallic
catalyst [5]. Here, we tested different catalysts with which we coated (100) Si substrates: Ni,
introduced as Ni(NO3)2 dissolved in ethanol, and 20 nm thick films of Ni, Au, Pt, and Ti deposited by
RF sputtering. The bigger particles were obtained using Ni(NO3)2 as catalyst (see Figure 1(a)), while
using Pt and Au we obtain smaller particles very homogenous in size. The highest level of porosity
was obtained, however, in the GaN particles synthesized using Ni(NO3)2. Porous GaN particles grown
on Ti thin films have a totally different morphology, remembering the shape of a sea star with a high
level of porosity (see Figure 1(b)).
We have tested different substrates to ascertain if it might play a role in the crystallographic orientation
of the GaN particles. For this purpose we used amorphous quartz, tungsten wire (W), (111) Silicon,
and pyrolitic boron nitride (p-BN) as substrates. SEM images reveal that the substrate plays also a
role in the coverage and distribution of the GaN particles.
Figure 1. Nanoporous GaN particles grown on (a) (100) Si substrate using Ni(NO3)2 as catalyst, (b) (100) Si
substrate using 20nm of Ti as catalyst and (c) W wire substrate using Ni(NO3)2 as catalyst.
3. Conclusions
We presented how different reaction parameters influence on the nanoporous Ga particles
morphology, size and porosity degree. The Ga holder seems to have an influence on the earlier
stages of evaporation and deposition of Ga on the substrate. The Ga quantity has an influence on
coverage of the substrate with GaN particles. The deposition time also controls the coating of the
substrate with nanoporous GaN particles. The catalyst plays two different roles: (1) it has an influence
on the size of the initial nucleuses that can be formed, and (2) it might induce a texturation of the layer
deposited. Finally, the substrate also plays an important role in the morphology and distribution of the
nanoporous GaN particles on its surface, although the interlayer formed by the catalyst hampers the
replication of the structure of the substrate by the porous GaN growing layer.
4. Acknowledgments
This work was supported by the Spanish Government under projects No. MAT2011-29255-C02-02
and TEC2010-21574-C02-02, the Catalan Government under project No. 2009SGR235, and the
European Commission within the Seventh Framework Program under project No. FP7-SPA-2010263044.
References
[1] Kim,T.; Kim, S. H., Yang, S. S.; Son, J.K.; Lee, K.H.; Hong, Y.G.; Shim, K.H.; Yang, J.W.; Lim, K.Y.; Bae, S.J
and Yang, G. M. “GaN based light-emitting diode with textured In tin oxide transparent layer coated with Al2O3
powder.” Appl. Phys. Lett. 94, (2009), 161107-1 – 161107-3
[2] Bao, K.; Kang, X. N.; Zhang, B; et al. “Improvement of light extraction from patterned polymer encapsulated
GaN-based flip-chip light-emitting diodes by imprinting.“IEEE Photonics Technol. Lett., 19, 22, (2007), 1840-1842
[3] Wierer, J. J.; David, A. & Megens, M. M. “III- nitride photonic-crystal light-emitting diodes with high extraction
efficiency.” Nat. Photonics., 3, 12, (2009),163-169
[4] Carvajal, J.J. and Rojo, J.C. “Morphology control in as-grown GaN nanoporous particles.” Cryst. Growth Des.,
9, 1, (2009), 320-326
[5] Carvajal, J.J.; Bilousov, O. V.; Drouin, D.; Aguiló, M.; Díaz, F. & Rojo, J.C. “Chemical Vapor Deposition of
porous GaN particles on Silicon.” Microsc. Microanal., 18, (2012), 905-911
Oral communication
White up-conversion emission in Er3+/Yb3+/Tm3+
doped YP5O14 ultraphosphate
a
a
c,*
M.A Hassairi , M. Dammak , D. Zambon , G.Chadeyron
b,c
, D. Boyer
b,c
and R.Mahiou
c,d
(a)Faculté des Sciences de Sfax, département de Physique, BP 1171, Université de Sfax,3018 SFAX, Tunisie.
(b) Clermont Université, ENSCCF, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 CLERMONT-FERRAND
(c) Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 CLERMONTFERRAND
(d) CNRS, UMR 6296, ICCF, BP 80026, F-63171 AUBIERE
* [email protected]
3+
Trivalent lanthanides (Ln ) doped materials exhibiting an efficient infrared into visible or ultraviolet
light conversion are already very attractive for applications in up-conversion (UC) lasers, high-density
memories, solid-state color displays, photonic devices and for biological or medical applications. The
most investigated doping systems concerns Yb-Er, Yb-Tm and Yb-Er-Tm associations, mainly
introduced in fluoride or oxide materials [1-5]. Moreover, a white up-conversion luminescence can be
3+
3+
3+
achieved from the association of Tm /Yb /Er rare earth ions in inorganic lattices for peculiar optical
applications e.g. liquid crystal display back light or white light LEDs [4]. In these tri-doped systems, the
3+
2
Yb acts as the sensitizer ion because of its characteristic energy levels and its long F5/2 excited level
3+
lifetime. Er is the optical activator that opens the possibility for simultaneous red and green emission
3+
transitions while Tm is the origin of the blue emission.
-1
Despite their high phonon energy around 1000 cm , phosphates have attracted much attention as
3+
host lattices for Ln ions because of a wide range of applications in optics and their unique physical
and chemical properties. Concerning UC studies, most of the works concern Yb-Er, Yb-Tm or Yb-ErTm doped phosphate glasses or glass ceramics [6,7]. In this purpose, ultraphosphates with REP5O14
formula (RE = rare earth elements) have been raised the interest of the laser community, where REs
elements are used as sensitizer-activator pairs for the up conversion phenomena.
3+
3+
3+
We have investigated the Tm /Yb /Er tri-doped YP5O14 crystalline ultraphosphate in order to
optimize the white emission via a UC mechanism using a 980 nm laser diode as excitation source.
The ultraphosphate polycrystalline samples (monoclinic, S.G. C2/c) were synthesized by the solid
state method. The doped materials were characterized by X-ray powder diffraction and infrared
spectroscopy. In order to estimate the possibility of producing white emission, the IR → visible UC
3+
3+
phenomenon under 980 nm excitation was studied at room temperature as a function of the Yb , Er
3+
and Tm concentrations.
Red, green and blue UC emissions were simultaneously observed, due to the energy transfer from the
3+ 2
3+
3+
Yb
F5/2 excited level to the main emitting levels of Er and Tm . UC spectra revealed
3+
4
4
unambiguously the contribution of Er emission transitions corresponding to F9/2 → I15/2 (red region)
2
4
4
3+
1
3
and H11/2, S3/2 → I15/2 (green region) and Tm emission transition corresponding to G4 → H6 (blue
region), to generate white light.
The influence of both excitation beam power and several doping ions amount on CIE chromaticity
coordinates were analyzed.
[1] Z.Y. Yan, B. Yan and L.P. Jia, Mater. Res. Bull., 48 (2013) 4402-4405.
[2] S. Liu, G. Wang, K. Pan, Y. Li, L. Feng, C. Tian, B. Jiang, N. Fan, Q. Feng and J. Zhang, J. Fluorine Chem.,
153 (2013) 61-67.
[3] J.H. Chung, Y. H. Ryu, S.Y. Lee, S. H. Kang and K. B. Shim, Ceram. Inter., 39 (2013) 1951-1956.
[4] X. Chen, Y. Li, F. Kong, L. Li, Q. Sun and F. Wang, J. Alloys Compds., 541 (2012) 505-509.
[5] M. Marin-Dobrincic, E. Cantelar and F. Cusso, Opt. Mater. Express, 2(11) (2012) 1529-1537.
[6] Y. Yu, F. Song, C. Ming, J. Liu, W. Li, Y. Liu and H. Zhao, Optics Com., 285 (2012) 4739-4744.
[7] C. Ming, F. Song and X. Ren, Current Appl. Phys., 13 (2013) 351-354.
Comunicación Oral
FOTOCATALIZADORES CERÁMICOS DE TITANIA
FOTOSENSIBLIZADOS CON METALES.
S. Cerro*, J. Badenes, C. Gargori, M. Llusar, G. Monrós,
Dpto. Química Inorgànica y Orgànica, Universidad Jaume I, Castellón (España)
*[email protected]
1. Introducción
Los Procesos de Oxidación Avanzada (POA) se basan en procesos fotoquímicos en los que
el radical hidroxilo posee alta efectividad para la oxidación de contaminantes orgánicos, en disolución
en agua o dispersados en el aire, resistentes a la degradación biológica a formas minerales o al
menos a compuestos orgánicos inocuos. El óxido de titanio es la referencia como material
fotocatalizador en la actualidad, dada su alta actividad, relativa estabilidad, bajo coste y baja
toxicidad, sin embargo, hay problemas a resolver como la baja velocidad de fotocatálisis, generación
de intermedios de degradación tóxicos, desactivación del material y necesidad de irradiación UV al no
acoplarse su band gap con la luz solar [1]. La introducción de metales dopantes en el gel binario
híbrido de Ti/Si ha sido estudiada con el fin de mejorar la capacidad fotocatalítica y obtener vidrios de
alto índice de refracción para aplicaciones ópticas. Cerro y col. han aplicado vidriados cerámicos y
composites cerámicos como fotocatalizadores, con interesantes resultados en la fotodegradación de
substratos tales como Naranja II en disolución [2]. S. Satoh et al [3] estudiaron geles SiO2MOn/m (M =
Ga,Gd, Nb, Sb, Sn, Ta, Ti y Zr) por métodos sol-gel, los resultados indican que son vidrios de interés
potencial en aplicaciones ópticas. Asimismo, M. Baba y col [4] estudiaron la fotodegradación de
colorantes orgánicos mediante vidrios de sílice dopados con metales de transición tales como Ti, V,
Cr, Mn, Au y Ag, observando directamente nanopartículas de sílice dopadas con los complejos
metálicos. Concluyen que el dopado con iones Au3+ es más eficiente que con Ag+.
2. EXPERIMENTAL Y RESULTADOS.
En este estudio se han utilizado como metales sensibilizadores los de la primera serie de
transición Mn y Fe. El desarrollo de estos materiales se realiza mediante metodología sol-gel a partir
de alcóxidos de titanio, acetato de hierro (II) y nitrato de manganeso (II) tetrahidrato. Los xerogeles
obtenidos, son sometidos sucesivamente a un tratamiento de carbonización (300ºC/1h) y de
estabilización(500ºC/1h) y caracterizados por diferentes técnicas: difracción de rayos X, indicando
sólo la presencia de un halo amorfo de rutilo más intenso en el caso de Mn, análisis térmico
diferencial y termogravimétrico (ATD-TG), espectroscopia UV-Vis-NIR, medida de la superficie
específica BET, así como mediante el ensayo de fotodegradación de Naranja II [2].
3. CONCLUSIONES.
Los resultados del ensayo de fotodegradación de naranja II indican un buen comportamiento
de los geles de titania con un tiempo de semivida (t 1/2 = 62 min) próximo a la anatasa de referencia.
Las muestras sensibilizadas con hierro presentan valores ligeramente superiores a los xerogeles de
titania y con capacidad fotocatalítica moderada-baja en el caso de manganeso. Ambos geles
presentan alta superficie específica, ligeramente superior en el caso del Ti-Mn, con peores resultados
fotocatalíticos. En el caso de las muestras carbonizadas a 300ºC/1h, ningún composite presenta
actividad fotocatalítica con valores que superan los 200 min. En las muestras estabilizadas se
observa un comportamiento moderado de fotoactividad, obteniéndose los mejores resultados para Ti
y Ti-Mn con valores próximos a 130 min.
Referencias
[1] C. Gargori, R.Galindo, M. Llusar, M.A. Tena, G. Monrós, J. A. Badenes, “Photocatalytic degradation of
Orange II by titania addition to sol-gel glasses”. Journal of Sol-Gel Science and Technology, 50(2009)314-320.
[2 S. Cerro, R.Galindo, A. García, A. Monrós, J. Badenes, C. Gargori, G. Monrós, , “Fotocatilazadores de y en
cerámica”. Libro resúmenes Qualicer 2012.
[3] S. Satoh, K. Susa, I. Matsuyama, “Sol-gel-derived binary silica glasses with high refractive index”. Journal of
Non-Crystalline Solids, 146(1992)121-128.
Comunicación Oral
[4] M. Baba, M. Ichihara, R. A. Ganeev, M. Suzuki, H. Kuroda, M. Morita, D. Rau, T. Ishii, and M. Iwamura,
“Direct observation of metal complex nanoparticles doped in sol-gel silica glasses using transmission electron
microscopy”, Applied Physics Letters 84(2004)2394-2396.
Agradecimientos: los autores agradecen la financiación de MEC (proyecto MAT2012-36988-C02-01)
"Synthesis of ceramic pigments by unconventional methods for novel ceramic
decoration technologies”
T. Stoyanova Lyubenova1, A. Rey1, D. Fraga, R. Martí1, I. Calvet, J. B. Carda1
1
Dept. Inorganic and Organic Chemistry, Jaume I University, Castellón, España
e-mail: [email protected]
Nowadays, the ceramic tiles industry strongly promotes modernization and
implementation of new technologies in the ceramic decoration process. The necessity
to develop ceramic pigments with improved properties causes the search for more
effective and homogeneous synthesis methods than the traditional currently used
solid state route.
The main objective of this study is to describe the benefits of unconventional synthesis
processes like sol-gel, freeze and spray draying and spray pyrolysis for development of
ceramic pigments with properties according to the new trends and modern
decorations. In the same research line the “in –situ” photothermal laser activation is
also applied as thermal treatment alternative to the conventional furnace calcination.
For that purpose, pigments with sphene structure (Cr:CaTiSiO5 and Cr:CaSnSiO5) as a
hosts for Cr(III) cromophore were selected. The incorporation of Cr(III) results in solid
solution formation that develop shades ranging from magenta-pink to brown colors.
Thus, we have discovered a new pigment with Cr:CaTiSiO5 composition that had never
been used before for coloring ceramics.
The obtained materials were characterized structurally and microstructurally. The
chromatic behavior before and after direct application in reference glazes was
evaluated using UV-VIS spectroscopy and CIE Lab colorimetry.
References:
[1] Lyubenova, T.S., Matteucci, F., Costa, A., Dondi, M., Carda, J., Ceramic pigments
with sphene structure obtained by both spray- and freeze-drying techniques, Powder
Technology, 193 (1), pp. 1-5, (2009)
[2] Lyubenova, T.S., Matteucci, F., Costa, A.L., Dondi, M., Ocaña, M., Carda, J. Synthesis
of Cr-doped CaTiSiO5 ceramic pigments by spray drying, Materials Research Bulletin,
44 (4), pp. 918-924, (2009)
[3] Cruciani, G., Dondi, M., Ardit, M., Lyubenova, T.S., Carda, J.B., Matteucci, F., Costa,
A.L., Malayaite ceramic pigments: A combined optical spectroscopy and neutron/X-ray
diffraction study, Materials Research Bulletin, 44 (8), pp. 1778-1785, (2009)
[4] Lyubenova, T.S., Ocaña, M., Carda, J., Brown ceramic pigments based on chromium
(III)-doped titanite obtained by spray pyrolysis, Dyes and Pigments, 79 (3), pp. 265-269,
(2008)
ABSTRACT BOOK
Órden alfabético | Classement par ordre alphabétique
PÓSTERS
AFFICHES
www.efe-es.com
Characterization of light–emitting diodes based on
ordered InGaN nanocolumns
Almudena Torres-Pardo1,2,*, Ana Bengoechea-Encabo3, Steven Albert3, Miguel A. SánchezGarcía3, David López-Romero3, Zarko Gacevic3, Enrique Calleja3 and Jose M. González-Calbet1
1. Dept.Química Inorgánica, Facultad de Químicas, Universidad Complutense de Madrid, 28040, Madrid, Spain
2. CEI Campus Moncloa, UCM-UPM, Madrid, Spain
3. ISOM-Dept. Ingeniería Electrónica, ETSIT, Universida Politécnica, 28040 Madrid, Spain
*[email protected]
Group III-nitride semiconductors are widely used in opto-electronic devices. In particular, InGaN alloys
are the active materials in light emitting diodes (LEDs) working in the whole visible spectrum. LEDs
based on self-assembled nanocolumns (NCs) with InGaN/GaN disks constitute an alternative to
conventional LED planar devices which major limitation is a strong reduction in efficiency at high
current injection [1]. However, the efficiency and reliability of LEDs based on self-assembled NCs are
hindered by a strong dispersion of electrical characteristics among individual nanoLED. Polychromatic
emission derives from an inhomogeneous distribution of indium concentration, changes in the NCs
geometry and the inherent tendency of InGaN alloys to develop composition fluctuations as a function
of the polarity of the growth crystallographic planes [2]. The recent development of selective area
growth of NCs by molecular beam epitaxy has allowed the achieving of highly homogeneous and
controllable GaN/InGaN NCs with improved crystalline quality and higher control over the indium
distribution [3,4].
In this work, we present results on the characterization of blue, green and yellow LEDs based on
ordered NCs with InGaN active layers. The morphology and distribution of the NCs is assessed from
Scanning and Transmission Electron Microscopy images (figure 1a-b) and their optical response is
evaluated from the analysis of electroluminescence spectra. Structural characterization of the
materials is performed by Scanning Transmission Electron Microscopy (STEM) carried out on
aberration-corrected microscope [5]. The indium distribution and concentration of the InGaN disks is
studied by EDS elemental maps confirming homogeneity of the InGaN layers. High crystal quality of
the NCs is set by high-angle annular dark-field (HAADF) imaging, while the polarity determination of
the semiconductor NCs is followed by locating the nitrogen atomic columns in annular bright field
(ABF) images (figure 1c).
Figure 1(a) Cross-sectional SEM images of a representative sample. Inset shows top view SEM picture. (b) Low
magnification TEM image of GaN/InGaN nanocolumn. (c) Atomically resolved Annular Bright Field (ABF) image
revealing the Ga and N atomic columns on the wurzite-type structure.
Acknowledgments
J.M.G.C. and A.T.P. acknowledge financial support by the Spanish Ministerio de Ciencia e Innovación
(MAT2011-23068 and CSD2009-00013) and facilities provided by the National Centre for Electron
Microscopy (CNME, UCM, Spain). Research by A.T.P. has been also supported by a PICATA
postdoctoral fellowship of the Moncloa Campus of International Excellence (UCM). E.C, A.B.E, Z.G.,
M.A.S.G and D.L.R. acknowledge financial support by the EU FP7 Contract GECCO 280694-2, the
EU ITN RAINBOW PITN-GA-2008-213238, and the Spanish projects CAM/P2009/ESP-1503 and
MICINN MAT2011-26703.
References
[1]
E. Kioupakis, P. Rinke, K. T. Delaney, C. G. Van de Walle, Appl. Phys. Lett. 98, (2011), 161107).
[2]
A. L. Bavencove, G. Tourbot, J. Garcia, Y. Desieres, P. Gilet, F. Levy, B. Andre, B. Gayral, B. Daudin, and
L. S. Dang, Nanotechnology,22, (2011), 345705.
[3]
S. Sekiguchi, K. Kishino, A. Kikuchi, Appl. Phys. Lett. 96, (2010), 231104.
[4]
S. Albert, A. Bengoechea-Encabo, M. A. Sanchez-Garcia, X. Kong, A. Trampert, E. Calleja, Nanotechnology
24, (2013), 175303.
[5]
Y. Li, L. Zhang, A. Torres-Pardo, J.M. González-Calbet, Y. Ma, P. Oleynikov, O.Terasaki, S. Asahina, M.
Shima, D. Cha, L. Zhao, K. Takanabe, J. Kubota, K. Domen, Nature Communications, 4, (2013), 2566.
Direct Laser Written Mid-Infrared Waveguides in
Fused Silica and Crystalline Quartz
1
1,
3
Javier Martínez , Airán Ródenas *, Toney Fernandez ,
2
3
1
Javier Rodríguez Vázquez de Aldana , Javier Solis and Francesc Díaz
1. Física i Cristal·lografia de Materials (FiCMA), Universitat Rovira i Virgili (URV), 43007, Tarragona, Spain
2. Grupo de Óptica, Facultad de Ciencias, Universidad de Salamanca, 37008 Salamanca, Spain
3. Laser Processing Group, Instituto de Óptica-CSIC, Madrid 28006 Spain
*[email protected]
1. Introduction
Photonics, the science of light, has allowed a huge progress in a great variety of fields, such as
telecommunications, sensing, laser manufacturing, medicine or information processing, among others.
Most of the photonics devices have been based on visible and near-infrared (NIR) light, whose
wavelength is lower than 2.5 µm. In recent years, however, there is an increasing interest in exploiting
a range of longer wavelengths called the mid-infrared (MIR) range which spans from 2.5 to 20 µm.
The MIR offers exciting advantages for applications in many scientific fields, apart from security and
military areas. The MIR covers the “fingerprint” zone which enables the identification of greenhouse
gases such as CO2 and CH4, or pollutants such as HCN and CF4. It is also the region where the
Earth’s atmosphere exhibits important transmission windows for both Earth and space observation:
the so-called L (3 - 4 µm), M (4.6 - 5 µm) and N (8 - 12 µm) bands. In order to unleash all this potential
science, the development of MIR integrated devices which can be designed to operate as sensors,
high resolution spectrometers or advanced beam combiners, is currently of high interest [1].
Femtosecond (fs) pulse direct laser writing (DLW) is a novel technique which has been demonstrated
to be capable of producing three-dimensional (3D) waveguide designs and configurations which are
required for efficient and low-loss interconnection between different components, such as optical fibers
and waveguide chips [2]. In this work we explore the possibility of fabricating, with this technique, MIR
waveguides in fused silica and crystalline quartz, which are transparent from the ultraviolet to up to the
MIR at around 4 µm.
2. Experimental work
2.1. Femtosecond pulse laser 3D fabrication
Low OH-concentration fused silica glass and standard α-quartz c-cut crystal, are employed as
substrate materials for the waveguides. Fig. 1 shows examples of fabricated waveguides in crystalline
quartz and fused silica. Although they have the same chemical composition (SiO2), their different
molecular structure imposes a different interaction between the fs pulses and the material. Our
presentation will show how we can create lowered refractive index structures in crystalline quartz, and
increased refractive index structures in fused silica glass. In the case of the crystal, we have designed
and fabricated cylindrical cladding structures which can sustain light propagation in the whole
transparency range of the crystal. On the other hand, in fused silica the ultrashort pulses can induce a
local increase of the index, from which we benefit to design step-index core waveguides which can
guide light through bends and also feature low loss butt-coupling to commercial fibers.
(a)
(b)
Figure 1. Transmission microscope images of fabricated waveguides in (a) α-quartz crystal and (b) fused silica glass.
Figure 2. Scheme of the optical setup used for modal characterization of NIR and MIR waveguides
2.2. Optical mid-infrared waveguide characterization
We have built complete setup for NIR and MIR optical characterization of waveguides (see Fig. 2).
Modal and propagation loss measurements of the waveguides are possible up to 5 µm, and
spectroscopic characterization of waveguides transmission up to 12 µm with a fiber coupled FTIR
spectrometer are also being performed. Some examples of modes measured at 3.39 µm wavelength
in the MIR range are shown in Fig. 3. For α-quartz, two different types of cladding waveguides are
shown: the first one is monomode (Fig. 3(a)) whereas the second one is much larger in size and
supports a great number of modes (Fig. 3(b)). In the case of step index waveguides made in fused
silica glass, we show here the observable modes for the waveguides shown in Fig.1b. Three different
modes can be excited almost independently (see Figs. 3(c), 3(d) and 3(e), respectively).
(b)
(a)
(c)
(d)
(e)
Figure 3. Measured near-field intensity mode profiles for selected waveguides at 3.39 µm. (a) Monomode and (b) multimode
waveguides made in α-quartz. (c), (d), (e) First three modes supported by a step-index waveguide made in fused silica.
3. Conclusions
MIR waveguides embedded in glass and crystal are being developed by the femtosecond laser writing
technique. Properties such as size, light confinement, modal behaviour or 3D propagation path can be
easily controlled. An optical setup allows modal characterization of fabricated waveguides and testing
of the performance providing feedback for fabrication optimization. The obtained waveguides will
serve as MIR sensors and first results will be shown.
4. Acknowledgments
This work has been partially supported by the Spanish Government under projects MAT2011-29255C02-O2, by the Catalan Government under Project 2009SGR235 and 2014FI_B 00274 and by the
European Commision under ACP2-GA-2013-314335- JEDI ACE.
References
[1]
[2]
Airán Ródenas, Guillermo Martin, Brahim Arezki, Nickolas Psaila, Gin Jose, Animesh Jha, Lucas Labadie,
Pierre Kern, Ajoy Kar, and Robert Thomson, "Three-dimensional mid-infrared photonic circuits in
chalcogenide glass," Opt. Lett. 37, 392-394 (2012)
K. M. Davis, K. Miura, N. Sugimoto, and K. Hirao, "Writing waveguides in glass with a femtosecond laser,"
Opt. Lett. 21, 1729-1731 (1996)
Efecto del tamaño en nanopartículas monodispersas
de ferrita MFe2O4 (M=Fe, Co y Zn)
1
1
1,
A. Delgado , M. Virumbrales , R. Sáez Puche y M.J. Torralvo
1,*
1. Departamento de Química Inorgánica, Facultad Químicas, Universidad Complutense de Madrid, 28040, Madrid, España.
*[email protected]
Introducción
Las ferritas son óxidos mixtos AB2O4 (siendo A un metal divalente y B uno trivalente) que
2+
3+
cristalizan con estructura tipo espinela, grupo espacial Fd-3m, dónde los cationes A y B ocupan
1/8 y 1/2 de los sitios tetraédricos (Td) y octaédricos [Oh] respectivamente, en un empaquetamiento
2cúbico compacto de O . La ferrita de Zn de tamaño micrométrico cristaliza con estructura de espinela
normal, (Zn)[Fe2]O4, y como consecuencia de esta distribución catiónica es antiferromagnética con
temperatura de orden, TN=10K. Por el contrario, las ferritas MFe2O4 con M= Fe y Co, son espinelas
inversas, (Fe)[FeM]O4, y se comportan como ferromagnéticas con temperaturas de Curie de 848K
and 793K respectivamente. Sin embargo, cuando estas ferritas espinela se preparan en la escala
2+
3+
nanométrica, la distribución catiónica es de espinela mixta, donde los cationes M y Fe están
ocupando simultáneamente los sitios Td y Oh dando como resultado una espinela de fórmula general
(M1-xFex)[Fe2-xMx]O4, donde x es el grado de inversión [1]. Estos materiales presentan comportamiento
superparamagnético por encima de la temperatura de bloqueo (T B) y sus propiedades magnéticas
dependen del tamaño de partícula, del grado de inversión y de las interacciones entre partículas.
En la actualidad se han desarrollado numerosos métodos de preparación de nanopartículas con
tamaño y forma controlados, pero en la mayoría de ellos se obtienen agregados de nanopartículas.
Además del efecto en el comportamiento magnético, la agregación de las partículas constituye un
gran problema para muchas aplicaciones tecnológicas por lo que se han investigado algunas rutas
sintéticas alternativas, como por ejemplo, encapsular las nanopartículas en diferentes matrices
orgánicas o inorgánicas para evitar o minimizar las interacciones entre las partículas. El presente
trabajo se centra en el análisis comparativo de las propiedades morfológicas, estructurales y
magnéticas de nanopartículas de ferrita, Fe3O4, CoFe2O4 y ZnFe2O4 estabilizadas con moléculas de
ácido oleico con el fin de obtener nanopartículas aisladas y poder estudiar el efecto del tamaño en el
comportamiento magnético, minimizando el efecto de las interacciones entre partículas.
Para la preparación de las nanopartículas de ferrita se ha seguido el método de descomposición
térmica de precursores en disolventes de alto punto de ebullición [2]. Como precursores inorgánicos
se han empleado los acetilacetonatos de Fe (III) y M (II), 1,2-hexadecanodiol como agente reductor,
oleilamina y ácido oleico como agentes estabilizantes y feniléter como disolvente (BP: 259°C). Los
reactivos se mezclan mediante agitación magnética bajo atmósfera inerte, se calienta la mezcla hasta
200°C y se mantienen un tiempo determinado y por último se calienta a reflujo. Con el fin de obtener
nanopartículas de diferentes tamaños se han variado los tiempos de reacción.
Conclusiones
Como se puede observar en las micrografías TEM (figura 1) las nanopartículas de ferrita MFe2O4
preparadas presentan, en todos los casos, morfología redondeada y una distribución estrecha de
tamaños. El tamaño medio de las nanopartículas se ha estimado a partir de las micrografías midiendo
entorno a 100 partículas, siendo de 4.7, 2.6 y 3.7 nm para las ferritas Fe3O4, CoFe2O4 y ZnFe2O4
respectivamente.
Los valores de susceptibilidad en todas las muestras son más altos que los que corresponden al
comportamiento paramagnético lo que sugiere que en todos los casos las nanopartículas son
superparamagnéticas por encima de la temperatura de bloqueo. A partir del máximo que se observa
en la representación de las curvas de susceptibilidad ZFC frente a la temperatura, se han estimado
las temperaturas de bloqueo de 6.35K, 53.6 K y 13.3K para las ferritas de Fe, Co y Zn
respectivamente. El alto valor de TB que se observa en el caso de la espinela de cobalto, se debe a la
2+
2+
2+
anisotropía intrínseca del Co en comparación con los cationes Fe y Zn [3]. La forma de las
curvas FC y la gran diferencia entre los valores de susceptibilidad de las curvas ZFC y FC para
temperaturas inferiores a la de bloqueo, sugieren que las partículas no interaccionan o lo hacen
débilmente debido a que están rodeadas de la envolvente orgánica.
Por otro lado, la magnetización es fuertemente dependiente de la interacción entre los cationes
superficiales de la nanopartículas con las moléculas de ácido oleico. Mediante espectroscopía IR se
ha determinado la naturaleza del enlace entre el ácido oleico y la superficie de las nanopartículas de
MFe2O4. En el caso de la magnetita, los grupos carboxilato actúan como ligandos quelato lo que hace
que aumente la anisotropía superficial y por tanto que disminuya la magnetización, y esto justificaría
además que la temperatura de bloqueo sea solo de 6.3 K. Sin embargo, en la ferrita de zinc los
grupos carboxilato, que actúan como ligandos puente, aumentan la magnetización. Esta ferrita
presenta un momento magnético a la saturación anormalmente alto (figura 1c) con un valor de
80emu/g, que corresponde a un grado de inversión de 0.3. Por el contrario, en el caso de las
espinelas de Fe y Co se observa una notable disminución de la magnetización a la saturación en
comparación con sus homólogos de tamaño de partícula micrométrico.
Fig. 1: Micrografías TEM de nanopartículas de espinela a) ZnFe2O4, b) CoFe2O4 y d) Fe3O4; c) Curvas de
magnetización frente al campo aplicado a 5K para las diferentes muestras.
Agradecimientos
Los autores agradecen a la Comunidad de Madrid por el proyecto S-2009/PPQ-1626 y al MINECO
por el proyecto MAT2010-19460.
Referencias
[1]
[2]
[3]
V. Blanco-Gutierrez, F. Jimenez-Villacorta, P. Bonville, Maria J. Torralvo- Fernandez, R. Saez-Puche, J.
Phys. Chem. C, (2011) 115 (5) 1627–1634.
Shouheng Sun, Hao Zeng, David B. Robinson, Simone Raoux, Philip M. Rice, Shan X. Wang, and
Guanxiong Li, J. Am. Chem. Soc., (2004) 126 (1) 273-279
V.Blanco-Gutierrez, J.A. Gallastegui, P. Bonville, M.J. Torralvo-Fernandez, R. Saez-Puche, J.Phys. Chem.
C, (2012) 116 (45) 24331
Poster o comunicación oral
Effect of the synthetic route on the crystal structure
and physical properties of GdBaCo2O5+δ
1*
2
3
Daniel Muñoz-Gil , Domingo Pérez-Coll , Juan Peña-Martínez , Susana Garcia-Martín
1
1. Departamento de Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, España
2 Instituto de Cerámica y Vidrio, CSIC, Cantoblanco, 28049 Madrid, España
3. Departamento de Didáctica de las Ciencias Experimentales, Facultad de Educación, Universidad Complutense, 28040Madrid, España
[email protected]
Perovskite oxides represented by the general formula LnBaCo2O5+δ (Ln = Pr, Nd, Sm, Eu, Gd,
Tb, Dy, and Ho) has drawn tremendous attention as potential cathodes for IT-SOFCs due to their
electrical and electrochemical properties. In particularly, GdBaCo2O5+ shows a wide range of oxygen
non-stoichiometry and its attractive physical and structural properties depend on the oxygen content.
The oxygen content of this oxide varies with the synthesis conditions. In this sense, GdBaCo2O5+ with
δ values close to 0 has been prepared in Ar atmosphere and δ values higher than 0.4 are always
determined for samples prepared in air with a slow cooling or annealed in oxygen flow. The crystal
structure of GdBaCo2O5+ derives from the 112-type structure with ap × ap × 2ap unit cell (ap refers to
the lattice parameter of the cubic perovskite) [1]. In this structure with δ = 0, Gd and Ba are ordered
into layers along the c axis and all the Co atoms are coordinated by O in squared pyramids. The
oxygen non-stoichiometry is accommodated within the (GdO)x planes in such a way that different
supercells have been proposed in the literature depending on the oxygen content and the ordering of
the anion vacancies (or the oxygen anions) in those planes [2-6].
δ
δ
δ
Selected Area Electron Diffraction and High Resolution Transmission Electron Microscopy
have been used to reveal that the crystal structure and microstructure of GdBaCo2O5+ are highly
influenced by the oxygen stoichiometry. The electrical characterization includes total conductivity
measurement by four point method under different atmospheres. The area-specific resistance (ASR)
in air of GBCO as the electrode materials was measured by electrochemical impedance spectroscopy
in a symmetrical two-electrode cell configuration.
δ
We have observed that both oxygen stoichiometry and crystal structure have a high impact on
the physical properties of the material. In particular, significantly better electrochemical properties
(lower ASR values), are observed for the material prepared under Ar gas flow, which shows the lower
oxygen content (compared to the materials prepared at air) and the anion vacancies located at
random.
References
1.
L. Er-Rakho, C. Michel, P. Lacorre and B. Raveau, J. Solid State Chem. 73 (1998) 531-535.
2.
A. Maignan, C. Martin, D. Pelloquin, N. Nguyen and B. Raveau, J. Solid State Chem. 142 (1999)
247-260.
3.
W. S. Kim, E. O. Chi, H. S. Choi, N. H. Hur, S. J. Oh and H. C. Ri, Solid State Comm. 116 (2000)
609-614.
4.
Y. Moritomo, T. Akimoto, M. Takeo, A. Machida, E. Nishibori,, M. Takata, M. Sakata, K. Ohoyama,
and A. Nakamura, Phys. Rev. B. 61 (2000) R13325-R13328.
5.
C. Frontera, J. L. García-Muñoz, A. Llobet, and M. A. G. Aranda, Phys. Rev. B. 65 (2002) 1804054(R).
6.
A. A. Taskin, A. N. Lavrov and Y. Ando, Phys. Rev. B. 71 (2005) 134414
Estudio de las interacciones magnéticas en
nanopartículas de ZnFe2O4
1,*
1
1
M. Virumbrales , A. Delgado , R. Sáez Puche y M.J. Torralvo
1
1. Departamento de Química Inorgánica, Facultad Químicas, Universidad Complutense de Madrid, 28040, Madrid, España.
*[email protected]
Introducción
Los materiales magnéticos nanoestructurados presentan inusuales propiedades químicas y físicas
en comparación con sus análogos de mayor tamaño de partícula, lo que ha generado mucho interés
debido a sus múltiples aplicaciones, tales como la tecnología de ferrofluídos, catálisis o aplicaciones
médicas, como la liberación controlada de fármacos, agentes de contraste en resonancia magnética
de imagen o en hipertermia [1].
En la escala nanométrica, las propiedades de las partículas dependen de los efectos de tamaño y
de los de efectos superficie, que aumentan según el tamaño de partícula disminuye. En
nanopartículas magnéticas los efectos de tamaño están relacionados con el bajo número de
portadores de momento ordenados, y los efectos de superficie se deben a la falta de coordinación,
espines canteados y desorden de los átomos en la superficie. Por lo tanto, el comportamiento
magnético de las nanopartículas es el resultado del núcleo ordenado y de la capa superficial
desordenada. Las interacciones dipolares y de espines superficiales afectan el comportamiento
magnético de las nanopartículas porque modifican la anisotropía del sistema. Por otra parte, las
nanopartículas aisladas pueden interaccionar con el medio circundante [2] y estas interacciones
también modifican la anisotropía de superficie y afectan a los parámetros magnéticos. La contribución
y la fuerza de estas interacciones son diferentes dependiendo de la composición, tamaño de partícula
y condiciones de síntesis y por lo tanto, puede ser difícil separar los efectos de tamaño y de superficie
sobre las propiedades magnéticas. En este contexto, el objetivo de este trabajo es estudiar el
comportamiento magnético de las nanopartículas de ferrita de zinc recubiertas con moléculas
orgánicas y encapsuladas en matrices porosas de sílice con el fin de investigar el efecto de las
interacciones de las nanopartículas sobre las propiedades magnéticas.
Para la preparación de las nanopartículas de ZnFe2O4 se han empleado dos métodos de síntesis.
En el primero de ellos, se ha seguido un método basado en la descomposición térmica de los
precursores de la ferrita en disolventes de alto punto de ebullición [3]. Como precursores de la ferrita
se han empleado Zn(acac)2 y Fe(acac)3 y fenil éter como disolvente. Además, para proteger la
superficie de las nanopartículas y controlar su crecimiento, se han utilizado como agentes
estabilizantes oleilamina, ácido oleico y 1,2-hexadecanodiol como agente reductor (figura 1a, muestra
Zn-3.7). En el segundo método se ha infiltrado por capilaridad una disolución acuosa con cantidades
estequiométricas de nitrato de zinc y nitrato de hierro en matrices porosas previamente preparadas,
con estructura tipo MCM-41 (figura 1b, muestra MH-Zn) y SBA-15 (figura 1c, muestra SB-Zn). Los
materiales infiltrados se mantienen al aire durante 24 horas y posteriormente se someten a 600°C
durante 2 horas. Después de este tratamiento térmico se obtienen nanopartículas de ZnFe2O4
encapsuladas en las matrices.
Conclusiones
En la micrografía TEM correspondiente a las nanopartículas de ferrita de zinc estabilizadas con
ácido oleico (figura 1a), se pueden observar nanopartículas con tamaño y forma homogéneo, que
presentan un distribución estrecha de tamaños centrada en 3.7 nm. En las figuras 1b y 1c se
muestran imágenes de las muestras correspondientes a las nanopartículas de ZnFe2O4 encapsuladas
en las matrices porosas de sílice. Las nanopartículas de ferrita tienen tamaños de partícula de
aproximadamente 2.5 nm en la matriz MCM-41 y 6-9 nm en la matriz SBA-15, de manera que ocupan
prácticamente todo el ancho del canal de la matriz.
A partir del máximo en las curvas de susceptibilidad ZFC (figura 1d) se han estimado los valores
de temperatura de bloqueo (T B), que aumentan al aumentar el tamaño de las partículas. Los altos
valores de susceptibilidad sugieren, en todos los casos, comportamiento superparamagnético por
encima de la temperatura de bloqueo. La forma de la curva de susceptibilidad FC y la gran diferencia
entre las curvas ZFC y FC a bajas temperaturas sugieren que las interacciones entre partículas no
son significativas. En el caso de las nanopartículas de ferrita de zinc estabilizadas con ácido oleico,
se comportan magnéticamente independientes sin interacciones. Aunque puedan existir interacciones
dipolares debido a la envolvente orgánica estas interacciones no son suficientemente intensas como
para impedir el aumento de magnetización por debajo la T B. Las nanopartículas de ZnFe2O4
encapsuladas en las matrices porosas de sílice son fuertemente magnetizadas a baja temperatura
aunque están alineadas en el interior de los poros de la matriz y por lo tanto, deben presentar
interacciones dipolares. Por la geometría de los canales, aunque las partículas interaccionen no
pueden formar estados de espines desordenados magnéticamente congelados que puedan impedir la
magnetización a baja temperatura.
Por otro lado, los valores de campo coercitivo a 5K son mayores en el caso de las nanopartículas
de ferrita de zinc encapsulada en las matrices porosas en comparación con las nanopartículas de
ZnFe2O4 estabilizadas con ácido oleico, lo que se ha atribuido a la tensión mecánica impuesta por la
matriz [4].
Figura 1. Micrografías TEM de: (a) nanopartículas de ZnFe2O4 estabilizadas con ácido oleico (muestra
Zn-3.7) y encapsuladas en matrices tipo (b) MCM-41 (muestra MH-Zn) y (c) SBA-15 (muestra SB-Zn). (d)
Curvas de susceptibilidad magnética ZFC/FC para las distintas muestras.
Agradecimientos
Los autores agradecen a la Comunidad de Madrid por el proyecto S-2009/PPQ-1626 y al MINECO
por el proyecto MAT2010-19460.
Referencias
[1]
[2]
[3]
[4]
Y.W. Jun, J.W. Seo, J. Cheon, Acc. Chem. Res., (2008) 41 (2) 179-189
V. Blanco-Gutierrez, M. Virumbrales, R. Saez-Puche, and Maria J. Torralvo-Fernandez, J. Phys. Chem. C,
(2013), 117 (40), pp 20927–20935
S. Sun, H. Zeng, D. B. Robinson, S. Raoux, P. M. Rice, S. X. Wang, and G. Li, J. Am. Chem. Soc., (2004)
126 (1) 273-279
-Puche, Chem. Mater.,
(2010) 22 (22) 6130–6137
Nanomaterials for cultural heritage: synthesis
and characterization of colloidal systems for
application in conservation of wall paintings and
carbonate materials
Livio Ferrazza1,2, Eloísa Cordoncillo Cordocillo1, Héctor Beltrán Mir1,*
1
Departamento de Química Inorgánica y Orgánica, Universitat Jaume I de Castellón, Campus del Riu Sec, E-12071,
Castellón de la Plana, Spain
2
Laboratorio Materiales, Instituto Valenciano de Conservación y Restauración de Bienes Culturales Culturarts
Generalitat, C/ Pintor Genaro Lahuerta 25 46010, Valencia, Spain
* [email protected]
This work shows a first study about the preparation and characterization of nanostructured BaO
suspensions and their evaluation to the consolidation and protection of wall paintings, plasters
and stones. The study of BaO nanoparticles synthesis is developed to introduce a series of
modified to improve the effectiveness of conservation treatments. These particles appear as an
interesting material to be used in conservation and preservation treatments of carbonate
materials and wall paintings.
BaO was synthesized by coprecipitation method in non-aqueous solutions. The nanoparticles
were characterized by transmission electron microscopy (TEM) showing that all synthesis
carried out with different experimental conditions gave a 20-50 nm particle size. The application
of these BaO nanoparticles on samples of wall paintings was also evaluated. Optical
microscopy (OM), scanning electron microscopy with energy dispersive x-ray analysis (SEMEDX), Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD) and UV-Vis
spectroscopy were the used techniques to characterize the materials, and also to evaluate the
effectiveness of treatments to the consolidation and protection.
Results indicated that the nanostructurated BaO products may have a protection or preconsolidation function on wall paint layers. The superficial application of the product forms a thin
layer, compatible with the chemical nature of the wall painting and produces a consolidating
action on the surface.
New ordered states in the Ca2Mn3O8-δ system
1
1,2
1,2
1
1
1
A. Mazarío-Fernández , A. Torres-Pardo , R. Cortés-Gil , A. Varela , M. Parras , M. Hernando ,
1
J.M. González-Calbet
1. Dpto. Química Inorgánica I, Facultad CC. Químicas, UCM, 28040, Madrid
2. CEI Campus Moncloa, UCM-UPM, Madrid, Spain
Manganese related perovskites (AMnO3, A=alkaline earth) present a wide range of fascinating
functional properties due to the ability of Mn to adopt several oxidation states and different
coordination polyhedra. Regarding their catalytic behaviour, CaMnO 3-δ selectively oxidizes, at least on
[1]
a laboratory scale, propene to benzene and 2-methyl propene . Moreover, the Ca-Mn-O system
presents a great variety of oxides with different Ca/Mn ratio and crystalline structure and a particular
behaviour: their reduction process leads to a rock-salt type structure which, in most cases, can be
[2]
oxidized to the starting material . Actually, the system CaMnO3-δ constitutes a good example of
stabilization of several metastable perovskite-related phases with Mn in different oxidation states (from
4+
2+
Mn to Mn ). When heated under reducing atmosphere, CaMnO3 is topotactically reduced to
CaMnO2.5 through intermediate oxygen-deficient perovskite phases with ordered oxygen vacancies.
In this compositional range, the cationic structural framework of the oxidized precursor CaMnO3 is
preserved. The final product of the CaMnO3 reduction process is CaMnO2, a rock-salt-related phase.
The CaMnO3-CaMnO2 topotactic reduction-oxidation process takes place via oxygen diffusion while
the cationic sublattice remains almost unaltered. Extra superlattice reflections in selected area
electron diffraction patterns indicate doubling of the CaMnO2 rock-salt cell along the cubic directions of
2+
2+
a distorted rhombohedral cell originated by ordering of Ca and Mn ions distributed in nanoclusters
into a NaCl-type matrix, as evidenced by dark field electron microscope images.
The local nature of the information provided by the transmission electron microscopy techniques used
to characterize the rock-salt type Ca1-xMnxO solid solution clearly hints at the existence of subtle extra
ordering in other upper oxides of the Ca-Mn-O system. We use in this paper the combination of
oxygen engineering techniques performed under adequate controlled atmosphere with local
characterization techniques like electron microscopy with spectroscopic ones like energy electron loss
spectroscopy (EELS) to provide a very complete characterization of another member of this system. In
4+
particular, Ca2Mn3O8 crystallizes in a layered structure with all Mn in octahedral coordination. The
2+
reduction process of this material leads to Ca2Mn3O5 with all Mn octahedrally coordinated in a rocksalt type structure (Fig. 1). By means of partial reductions, several oxides with Mn in intermediate
oxidation states and therefore materials with different functional properties have been stabilized. Once
again, the reduction and oxidation process of this system is reversible. The different samples obtained
in the Ca2Mn3O8-δ system have been characterized by using imaging High Angle Annular Dark Field
(HAADF) and Annular Bright Field (ABF) techniques associated to EELS and Energy Dispersive
Spectroscopic (EDS) techniques in an aberration-corrected electron microscope with atomic
resolution. The structural evolution and the local variation of the Mn oxidation state in different phases
with different anionic composition will be discussed (Fig. 2).
Fig.1.- Reduction-oxidation process corresponding to the Ca2Mn3O8-δ system.
Fig. 2.- HREM image along [010] corresponding to Ca2Mn3IVO8.
References
[1] A. Reller, J. M. Thomas, D. A. Jefferson and M. K. Uppal, Proc. R. Soc. Lond. A, 394 (1984), 223-241.
[2] A. Varela, S. de Dios, M. Parras, M. Hernando, M.T. Fernández-Díaz, A.R. Landa-Cánovas and J.M.
González-Calbet, J. Am. Chem. Soc., 131 (2009), 8660-8668.
Obtención de nanopartículas de vanadato de itrio
dopado con erbio y con cromo
1
1,*
Lorena Alcaraz y Josefa Isasi
1. Dpto. de Química Inorgánica I, Universidad Complutense de Madrid, Avda Complutense s/n 28040, Madrid
* e-mail: [email protected]
La mejora de las propiedades luminiscentes de fases de vanadato de itrio dopado con diferentes
tierras raras, para su utilización en ciertos dispositivos ópticos, ha impulsado su estudio a lo largo de
los años. Diferentes métodos de preparación se han empleado para la obtención de estas fases, en el
intento de actuar sobre la morfología de las partículas y conseguir una mejora de su emisión
luminiscente [1]. Entre los métodos de síntesis utilizados se incluyen la coprecipitación, el empleo de
rutas coloidales, los procesos sol-gel o la síntesis hidrotermal.
En general, a diferencia de los métodos convencionales que requieren altas temperaturas y que
conllevan un incremento del tamaño de partícula, los procesos sol-gel, los métodos de química
coloidal o la síntesis hidrotermal permiten la obtención de fases con tamaño de partícula controlado,
lo que puede llegar a incrementar la probabilidad de que se produzcan emisiones espontáneas y, por
tanto, la mejora de las propiedades ópticas de las fases obtenidas [2]. La luminiscencia también
puede verse modificada con el dopaje efectuado. En este sentido, investigaciones previas han
mostrado una diferente emisión luminiscente cuando en el vanadato de itrio dopado se sustituye la
tierra rara o el vanadio por cromo [3].
Se exponen en este trabajo los resultados obtenidos en la preparación y en la caracterización
estructural y morfológica de ortovanadatos Y0.9Er0.1V1-xCrxO4 (con x = 0 y 1) cuando se emplean
diferentes condiciones de reacción.
Agradecimientos
Los autores agradecen a la Fundación Neurociencias y Envejecimiento (189/2012; 14/2013 y
177/2013) la financiación concedida para el desarrollo de este trabajo.
Referencias
[1]
[2]
[3]
S. Ray, A. Banerjee, P. Pramanik, “Shape controlled synthesis, characterization and photoluminescence
3+
3+
properties of YVO4:Dy /Eu phosphors”. Mat. Sci. Eng. B, 156, (2009), 10-17.
R.M. Mohamed, F.A. Harraz, I.A. Mkhalid, “Hydrothermal synthesis of size-controllable Yttrium
Orthovanadate (YVO4) nanoparticles and its application in photocatalytic degradation of direct blue dye”. J.
Alloy. Comp., 532, (2012), 55-60.
L. Alcaraz, J. Isasi, M. Fernández, C. Díaz-Guerra, “Effect of synthesis conditions on the structural
characteristics and luminescence properties of Y0.9Eu0.1V1-xCrxO4 (0 ≤ x ≤ 0.5) nanopowders”. Mater. Chem.
Phys., (2014), In press.
Order-disorder phenomena in both cationic and
anionic sublattices in manganese related
perovskites
1
1,2
1
Daniel González-Merchante , Raquel Cortés-Gil , M. Luisa Ruiz-González , Almudena-Torres1,2
3
4
1,*
Pardo , José M. Alonso , Enrique Iborra and José M. González-Calbet
1. Departamento de Química Inorgánica, Facultad de Químicas, Universidad Complutense (UCM), 28040-Madrid, Spain.
2. CEI Campus Moncloa, UCM-Universidad Politécnica (UPM) de Madrid, 28040-Madrid, Spain
3. Instituto de Ciencia de Materiales, CSIC, C/ Sor Juana Inés de la Cruz, 3, 28049-Madrid, Spain
4. Departamento de Tecnología Electrónica, E.T.S.I.T, UPM, 28040-Madrid, Spain
*[email protected]
Manganese mixed oxides, exhibiting perovskite related structure, have been extensively studied as a
consequence of their catalytic and transport properties linked to the coexistence of several
2+
3+
4+
manganese oxidation states: Mn , Mn and Mn . In this landscape, the La1-xAExMnO3 (AE=Ca, Sr)
system occupies a prominent place due to the appearance of colossal magnetorresistance behaviour
[1] and other interesting compositional dependent physical phenomena. Actually, since the doping
level is modified the occupancy of the 3d band changes as a consequence of the coexistence of
3+
4+
different Mn /Mn ratio, and different electrical and magnetic behaviours are rendered [2]. Even
more, other chemical strategies such as the incorporation of vacancies either at the cationic,
(La1-xAEx)zMnO3, or anionic, La1-xAExMnO3-δ,sublattices can be applied, enhancing the possibilities.
Actually, compositional variations are on the basis of the development of new materials and a precise
characterization is required for understanding the properties of the as prepared solids. Nowadays, the
integration of spherical aberration correctors in transmission electron microscopes has given direct
access to oxide structural defects with atomic resolution [3]. This enhancement in instrumental
performance, in terms of spatial and energy resolution, allow exploring the local properties of
functional oxides at the most refined scale, giving valuable microscopic insight into the local structure
that ultimately determines their functional properties.
Exploiting these advantages has been mainly related to the characterization of well-ordered artificial
heterostructures but is an emerging and attractive tool for solving intricate structural and analytical
problems in complex oxides and related solid state systems in powdered form. In this context, the aim
of this work is to show several examples of how strong correlated manganese oxide systems
exhibiting different heterogeneities at the cationic and anionic sublattices can be precisely
characterized through the ensemble of atomically-resolved Electron Energy Loss Spectroscopy
(EELS), High Angle Annular Dark Field (HAADF) imaging and Annular Bright Field (ABF) imaging
techniques. Local defects in two different systems, La0.5AE0.5MnO3 and (La1-xSrx)zMnO3-δ, will be
discussed.
The motivation of the first system, La0.5 AE0.5MnO3, is related to elucidate if whether or not there is any
compositional difference at atomic level in the La/AE distribution over the A site of the perovskite that
could provide different local interactions, affecting to the bulk behaviour. The polycrystalline samples
were prepared following standard procedures previously reported. The HAADF study reflects the
presence of a heterogeneous distribution of the La and AT cations. For instance, figure 1a is a
representative HAADF image of the La0.5Ca0.5MnO3 sample along [100] zone axis in which contrast
differences at the A site of the perosvskite lattice are evident. Since under the HAADF configuration,
the contrast at the image is highly dependent on the atomic number, the brightest constrast could
correspond to La richer columns of atoms while the less brilliant to richer Ca columns of atoms. This
information is complemented with a compositional analysis by means of EELS at atomic resolution as
depicted in the corresponding maps for each element shown in figure 1b.
In the case of the La0.56Sr0.44MnO2.5 compound [4], conventional TEM indicated the presence of
disorder along b direction. The aberration corrected electron microscopy has clarified this situation.
Actually, the sample exhibits two types of rock-salt (RS) blocks, as evidenced in HAADF image
depicted in figure 2a. The different contrast of the indicated blocks (see figure 2a) suggests
compositional differences. The chemical maps obtained from the Mn-L2,3, La-M4,5, and Sr-M4,5 signals
(figure 2) unambiguously indicate that Mn cations are located at the B position of the perovskite
structure but also in the less brightest rock-salt defect layer (DRS-1) while La/Sr cations occupy the A
perovskite positions as well as those corresponding to the brightest rock-salt defect layer (DRS-2).
Conductivity measurements performed in these materials will be discussed.
.
Figure 1. (a) HAADF image corresponding to La0.5Ca0.5MnO3; (b) EELS spectra sum, acquired over the area marked in (a),
showing the Mn-L2,3, La-M4,5 and Ca-L2,3 signals; (c) HAADF image simultaneously recorded to EELS acquisition; (d) mapping
obtained for the Ca-L2,3 signal (e) mapping obtained for the La-M4,5 signal; (f) mapping obtained for the Mn-L2,3 signal.
(a)
(a)
(b)
(b)
(d)
(d)
(e)
P
(e)
(f)
[100]
DRS-2
NaCl- 2
(c)
DRS-1
NaCl- 1
(c)
(f)
(g)
0.39 nm
0.39 nm
[100]
Figure 2. (a) HAADF image corresponding to La0.56Sr0.44MnO2.5; (b) Area of the HAADF image selected for EELS study; (c) EELS
spectra sum showing the Mn-L2,3, La-M4,5 and Sr-M4,5 signals; (d) HAADF image simultaneously recorded to EELS acquisition;
(e) mapping obtained for the La-M4,5 signal; (f) mapping obtained for the La-M4,5 signal; (f) mapping obtained for the Sr-M4,5
signal.
References
S. Jin, T. H. Tiefel, M. McCormac, R. A. Fastnacht, R. Ramesh and L. H. Chen, Science 264, (1994), 413415 .
[2] P. Schiffer, A. Ramírez, W. Bao and S.-W. Cheong, Phys. Rev. Lett., 75, (1995), 3336-3339.
[3] D. A. Muller, L. Fitting Kourkoutis, M. Murfitt, J. H. Song, H. Y. Hwang, J. Silcox, N. Dellby, and O. L.
Krivaneket. Science 319, (2008), 1073-1076.
[4] M. Luisa Ruiz-González, Raquel Cortés-Gil, Almudena Torres-Pardo, Daniel González-Merchante, José M.
Alonso, and José M. González-Calbet, Chemistry A European Journal19, (2013), 1-6.
[1]
Póster para el VII Encuentro Franco-Español Química-Física del
estado sólido.
TÍTULO: Reciclado del vidrio en el desarrollo de nuevos soportes
cerámicos.
AUTORES: A. Muñoz Galindo, J.J Vázquez Esteller, T. Vivó Muñoz.
AFILIACIÓN: Estudiantes de Grado de Ingeniería Química en la
Universidad Jaume I de Castellón.
TEMA: Materiales cerámicos.
ABSTRACT: Study based on theoretical literature on the introduction
of recycled glass in ceramic substrates, ceramic raw materials and
other recycled materials such as ceramics industry sludge. The
objective is to minimize the consumption of natural resources, reduce
waste, increase efficiency and effectiveness in the process of production
of ceramic tiles.
RESUMEN: Estudio teórico basado en bibliografía sobre la
introducción de vidrio reciclado dentro de soportes cerámicos, con
materias primas cerámicas y otros materiales reciclados como los
fangos de la industria cerámica. El objetivo es minimizar el consumo
de recursos naturales, reducir residuos, aumentar la eficacia y la
eficiencia en el proceso de producción de azulejos cerámicos.
[Póster]
Reducing the nonlinear effect by controlling the
sintering atmosphere
1*
2
3
2
Xavier Vendrell , José E. García , Fernando Rubio-Marcos , Diego A. Ochoa , Jose F.
3
1
Fernandez y Lourdes Mestres
1.
Grup de Química de l’Estat Sòlid, Dept. Química Inorgànica, Universitat de Barcelona, 08028, Barcelona, Spain
2. Department of Applied Physics, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain
3. Electroceramic Department, Instituto de Cerámica y Vidrio, CSIC, Kelsen 5, 28049 Madrid, Spain
*[email protected]
Excellent piezoelectric and electromechanical properties were achieved in a series of lead-based
ferroelectric ceramics, especially Pb(Zr,Ti)O3 (PZT). As the electromechanical properties of PZT are
attributed to the morphotropic phase boundary (MPB) [1], strong emphasis was laid on investigating
systems containing MPBs. Environmental issues, however, may ultimately require the replacement of
these lead-based materials of the electronic components [2]. Therefore, extensive studies on MPB
lead-free materials have been undertaken [3].
Over the last few years, a lot of attention has focused on (K,Na)NbO 3 (KNN) based ceramics
because of their good electromechanical properties and high Curie temperature for compositions close
to MPB [4]. Unfortunately, it is difficult to obtain samples with such characteristics by a technological
and economically available process although good piezoelectric properties have been reported for
samples obtained by conventional ceramic route.
Particularly, the composition (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 (KNL-NTS) exhibits interesting
properties, that make it probably the most workable lead-free piezoelectric system known to date [5].
Nevertheless, some of their properties are not suitable for all purpose. KNL-NTS ceramics show a
noticeable nonlinear behaviour (i.e. properties dependent of the applied electric field and/or
mechanical stress) which is due mainly to extrinsic effects [6]. As a consequence, research fields are
open in order to obtain new KNN-based materials capable to replace hard PZT in power devices.
Thus, it is interesting to explore different ways to improve the nonlinear behaviour in KNN
systems. It is well known that sintering atmosphere could determine the appearance of oxygen
vacancies in perovskite systems. As a consequence, sintering atmosphere could influence KNL-NTS
properties by reducing, for example, nonlinear response [7,8]. Consequently, the effect of sintering
conditions on the structural and nonlinear dielectric properties of KNL-NTS ceramics was studied in
this work.
Dense lead-free (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 piezoelectric ceramics are prepared by
the conventional solid state reaction. The effect of different sintering conditions (synthetic air, O 2 and
Ar) on some structural, dielectric and piezoelectric properties are studied. Long sintering time (16h)
promotes the formation of a secondary phase. High values of longitudinal piezoelectric constant are
obtained when ceramics are sintered under Ar or O 2 for low dwell time (2h). However, nonlinear
response turns out to be significantly dependent of the sintering atmosphere. Results are discussed
taking into account the formation of complex defects, capable to pin domain wall, when sintering
promotes the creation of oxygen vacancies. Sintering in an inert atmosphere seems to be a good via
to reduce nonlinear response in KNN-based piezoceramics.
[Póster]
References
[1]
B. Noheda, "Structure and high-piezoelectricity in lead oxide solid solutions". Curr. Opin. Solid
State Mater. Sci. 6 (2002) 27–34.
[2]
T. Takenaka, H. Nagata, "Current status and prospects of lead-free piezoelectric ceramics". J.
Eur. Ceram. Soc. 25 (2005) 2693–2700.
[3]
M.D. Maeder, D. Damjanovic, N.
Electroceramics. 13 (2004) 385–392.
[4]
Y. Saito, H. Takao, T. Tani, T. Nonoyama, K. Takatori, T. Homma, et al., "Lead-free
piezoceramics". Nature. 432 (2004) 84.
[5]
F. Rubio-Marcos, J.J. Romero, J.F. Fernández, P. Marchet, "Control of the Crystalline
Structure and Piezoelectric Properties of (K,Na,Li)(Nb,Ta,Sb)O3 Ceramics through Transition
Metal Oxide Doping". Appl. Phys. Express. 4 (2011) 101501.
[6]
D.A. Ochoa, J.E. García, R. Pérez, V. Gomis, A. Albareda, F. Rubio-Marcos, et al., "Extrinsic
contribution and non-linear response in lead-free KNN-modified piezoceramics". J. Phys. D.
Appl. Phys. 42 (2009) 025402.
[7]
J.G. Fisher, S.-J.L. Kang, "Microstructural changes in (K0.5Na0.5)NbO3 ceramics sintered in
various atmospheres". J. Eur. Ceram. Soc. 29 (2009) 2581–2588.
[8]
X. Vendrell, L. Mestres, "Optimization of the sintering conditions of the [(K0.5Na0.5)1-xLix]NbO3
system". Phys. Procedia. 8 (2010) 57–62.
Setter,
"Lead
Free
Piezoelectric
Materials".
J.
Silicon Pulsed Laser Ablation in chloroform
1
1
1
1
Kamal Abderrafi , Raúl García-Calzada , Juan F Sanchez-Royo , Vladimir S Chirvony , Saïd
2
3
1,*
1,2
Agouram , Rafael Abargues , Rafael Ibáñez and Juan P Martínez-Pastor
1
Instituto de Ciencias de los Materiales, Universidad de Valencia, PO Box 22085, 46071 Valencia, Spain
2
Dpt. Física Aplicada, Universidad de Valencia, Dr Moliner 50, 46100 Burjassot (Valencia), Spain
3
Intenanomat SL, C/Catedratico José Beltrán 2, 46980 Paterna (Valencia), Spain
*[email protected]
1. Introduction
Pulsed laser ablation of solid targets immersed in liquid (pulsed laser ablation in liquid, PLAL) is a
rapidly growing technology, which enables the production of colloidal nanometre-sized particles. This
method enables not only the formation but the functionalization of nanoparticles (NPs) by different
ligands. [1–4]. On the one hand, the PLAL technique is commonly used to produce Si NPs, given the
[5]
applications envisaged for Si quantum dots in photovoltaics.
The size of Si QDs has a significant impact on their optical properties due to size confinement,
[6]
multiexciton generation being the most important one . On the other hand, the surface chemistry of
semiconductor NPs, can lead to new functionalities (device patterning, catalysis, hydrogen storage,
[7,8]
, other than new ink formulations.
etc.)
Due to the relatively high energy of the laser beam a significant amount of solvent can be affected by
pyrolytic processes, as it has been already reported in the case of Au NPs generation in toluene by
[2]
using 9 ns 1064 nm pulses. It was found more recently that PLAL of a Si target in ethanol with the
[3]
[9]
use of 1064 nm excitation pulses of 10 ns and 35–1000 fs results in the formation of not only Si,
but also of SiC nanocrystals.
2.- Summary
We show, at this work, that a long-time laser ablation (40 ns, 355 nm laser pulses) of a Si target in
chloroform (CHCl3) results in the formation of (i) multi-crystalline NPs composed of small (5–10 nm) Si
and SiC mono-crystallites, (ii) multilayer graphite shells covering the multi-crystalline NPs and (iii) free
carbon multilayer nanostructures (onion-like carbon or carbon nano-onions).
On the basis of a comparison of the efficiency of formation of carbon nanostructures in CHCl3 versus
[1]
[10]
and by ultrasound treatment reported in our previous work , we suggest
CCl4 by laser ablation
that a chemical (solvent decomposition giving rise to highly reactive CH-containing radicals) rather
than a physical (solvent atomization followed by carbon nanostructure formation) mechanism is
responsible for graphitic shell formation.
We have already described that a two-step process developed to produce small (a few nm) Si
nanocrystals in colloidal suspension consisting of (1) a short-time (5 min) PLAL of a Si target in
chloroform and (2) a long-time (60–90 min) ultrasound treatment of the suspension in the presence of
HF that resulted in a disintegration of the initial big polycrystalline Si NPs to a few nm Si
[10]
monocrystallites . No carbon nanostructures were found in these NPs, most likely because the Si
target was irradiated for a relatively short time that prevented secondary ablation of produced Si NPs.
The first step on the chemical path for the formation of graphite nanostructures on Si NPs consists in
[11]
the formation of radicals, . These radicals reacts to form hydrocarbon polymers (as an intermediate
product) and then forms graphite structures. An alternative preliminary hypothesis involves
hydrogenation of the Si NP surface by hydrogen released due to thermal decomposition of
CHCl3 followed by photochemical cleavage of the Si–H bond under illumination by 355 nm light pulses
and an interaction of the formed Si dangling bonds with products of chloroform thermal decomposition.
The process of graphitic shell formation under conditions of laser ablation in chloroform can be
interesting for Si surface passivation, functionalization and protection.
Fig 1.:: Schematic synthetic pathway
Fig. 2: Scheme of the PLAL process in CHCl3.
References
[1]
K. Abderrafi, R. García-Calzada, J. F. Sanchez-Royo, V. S. Chirvony, S. Agouram, R. Abargues, R.
Ibáñez, J. P. Martínez-Pastor, J. Phys. D. Appl. Phys. 2013, 46, 135301.
[2]
V. Amendola, G. A. Rizzi, S. Polizzi, M. Meneghetti, J. Phys. Chem. B 2005, 109, 23125.
[3]
S. Yang, W. Cai, H. Zeng, X. Xu, J. Mater. Chem. 2009, 19, 7119.
[4]
S. Yang, H. Zeng, H. Zhao, H. Zhang, W. Cai, J. Mater. Chem. 2011, 21, 4432.
[5]
P. Löper, D. Stüwe, M. Künle, M. Bivour, C. Reichel, R. Neubauer, M. Schnabel, M. Hermle, O. Eibl, S.
Janz, M. Zacharias, S. W. Glunz, Adv. Mater. 2012, 24, 3124.
[6]
D. Timmerman, J. Valenta, K. Dohnalová, W. D. A. M. de Boer, T. Gregorkiewicz, Nat. Nanotechnol.
2011, 6, 710.
[7]
Y. Li, E. J. Lee, W. Cai, K. Y. Kim, S. O. Cho, ACS Nano 2008, 2, 1108.
[8]
J. Zeng, F. Su, Y.-F. Han, Z. Tian, C. K. Poh, Z. Liu, J. Lin, J. Y. Lee, X. S. Zhao, J. Phys. Chem. C 2008,
112, 15908.
[9]
P. G. Kuzmin, G. A. Shafeev, V. V. Bukin, S. V. Garnov, C. Farcau, R. Carles, B. Warot-Fontrose, V.
Guieu, G. Viau, J. Phys. Chem. C 2010, 114, 15266.
[10]
K. Abderrafi, R. García Calzada, M. B. Gongalsky, I. Suárez, R. Abarques, V. S. Chirvony, V. Y.
Timoshenko, R. Ibáñez, J. P. Martínez-Pastor, J. Phys. Chem. C 2011, 115, 5147.
[11]
M. Weissman, S. W. Benson, J. Phys. Chem. 1983, 87, 243.
[Se debe indicar en el encabezado si se trata de Comunicación Oral o Póster]
Síntesis y caracterización de circonato de bario
dopado con cationes trivalentes
O. A. GERENA R.1, J.B. CARDA C.2 Y J.S. VALENCIA R.3
1. Escuela Colombiana de Carreras Industriales Bogotá, D.C., Colombia
2 Departamento de Química Inorgánica y Orgánica,
Universitat Jaume I de Castellón. España
3. Laboratorio de Catálisis Heterogénea, Departamento de Química,
Universidad Nacional de Colombia–Sede Bogotá, Bogotá, D.C., Colombia
*[email protected]
Introducción
El circonato de bario es un material de gran interés por sus posibles aplicaciones en
electrocerámicas, reactores nucleares, sensores entre otras en atención a su alto punto de fusión,
estructura cristalina, baja reactividad química y estabilidad en ambientes tanto oxidantes como
reductores. Se prepara de manera regular por el método cerámico que produce agregados
heterogéneos y de grandes dimensiones. Como una alternativa de síntesis se usó el método citrato
amorfo[1], que proporciona un medio homogéneo que permite controlar la estequiometría de la
reacción, la pureza de fases, la textura y el tamaño de partícula.
Metodología.
El método de síntesis propuesto incluye la preparación de disoluciones acuosas de los cationes, su
mezcla en una disolución de ácido cítrico, el ajuste del pH y, la eliminación del disolvente y la
posterior calcinación a 800°C de los precursores antes obtenidos. Sel dopaje del circonato de bario se
hizo en tres niveles 0.1, 0.2 y 0.3% con los cationes trivalentes. Lacaraterización se hizo por
difracción de rayos X, microscopía electrónica de barrido, fotoluminiscencia y espectroscopías Raman
y Uv-Vis
Conclusiones.
El análisis por difracción de rayos X (Figura 1) muestra que calcinando los precursores a 800°C se
obtiene circonato de bario, indexado en el grupo espacial Pm-3m(221), Z= 1, sistema cristalino cúbico
con parámetro de celda a=4.193Å y volumen de celda de 73,718 Å3; no se aprecian diferencias
significativas debidas a la adición del catión dopante, debido al bajo porcentaje usado. Se evidencia la
presencia de carbonato de bario y óxido de circonio que permanecen sin reaccionar a esta
temperatura. Lo anterior se confirma por espectroscopía Raman (Figura 2) y por microscopía
electrónica de barrido (Figura 3).
Figura 1 Difractograma de rayos X para el circonato de
bario.
Figura 2Espectro Raman para circonato de bario.
Los análisis por microscopía electrónica de barrido permiten apreciar los cristales de carbonato de
bario que permanecen sin reaccionar (Figura 3). Por medio de espectroscopía Uv-Vis, se
determinaon los valores de band-gap para los sólidos preparados encontrando valores entre 3.8 y 4.4
eV, resultados que concuerdan con reportes de literatura. Los espectros de fotoluminiscencia (Figuras
4, 5 y 6) muestran cambios significativos en el ordenamiento de los cristales en función del contenido
de agente dopante; el comportamiento general sugiere que se obtiene una estructura más ordenada
cuando el porcentaje de dopaje es del 0,3% de lantánido trivalente.
[Se debe indicar en el encabezado si se trata de Comunicación Oral o Póster]
Figura 3 Micrografías BaZrO3 dopado con praseodimio.
Figura 4 Espectro de fotoluminiscencia para circonato de
bario
Figura 5 Espectro fotoluminiscencia, BaZrO 3 dopado con
Lantano al 0.1, 0.2 y 0.3%.
Figura 6 Descomposición del espectro de
fotoluminiscencia de BaZrO3 dopado con holmio
La descomposición del espectro de fotoluminiscencia muestra que ésta está conformada por un
conjunto de tres señales, cuyas máximas intensidades se ubican en los 450nm (zona verde del
espectro visible), 500 y 580nm (zona amarilla), el ajuste de la sumatoria de señales guarda una gran
similitud con los datos obtenidos experimentalmente, tal como se aprecia en la Figura 4.8. Las dos
primeras señales presentan intensidades bajas en comparación con la tercera.
Agradecimientos
Expresamos nuestro agradecimiento al profesor Elson Longo y su grupo de colaboradores, de la
Universidad Federal de San Carlos, Estado San Pablo en Brasil; su ayuda fue fundamental en la
consecución de los análisis para esta investigación.Los agradecimientos serán en el mismo formato
que el texto.
Referencias
[1]
Bhagwat, M. Synthesis of nanocrystalline zirconia by amorphous citrate route: structural and
thermal (HTXRD) studies. Materials Research Bulletin 2004, 39, 1627–1640.
(205) Cavalcante, L.; Anicetesantos, M.; Pontes, F.; Souza, I.; Santos, L.; Rosa, I.; Santos, M.;
Santosjunior, L.; Leite, E.; Longo, E. Effect of annealing time on morphological characteristics of
Ba(Zr,Ti)O3 thin films. Journal of Alloys and Compounds 2007, 437, 269–273.
(226) Khan, Z.; Qureshi, M. Tantalum doped BaZrO3 for efficient photocatalytic hydrogen generation
by water splitting. Catalysis Communications 2012, 28, 82–85.
(227) Borja-Urby, R.; Diaz-Torres, L. a.; Salas, P.; Angeles-Chavez, C.; Meza, O. Strong broad
green UV-excited photoluminescence in rare earth (RE=Ce, Eu, Dy, Er, Yb) doped barium zirconate.
Materials Science and Engineering: B 2011, 176, 1388–1392.
(228) Borja-Urby, R.; Díaz-Torres, L. a.; Salas, P.; Moctezuma, E.; Vega, M.; Ángeles-Chávez, C.
Structural study, photoluminescence, and photocatalytic activity of semiconducting BaZrO3:Bi
nanocrystals. Materials Science and Engineering: B 2011, 176, 1382–1387.
[Se debe indicar en el encabezado si se trata de Comunicación Oral o Póster]
(229) Borja-Urby, R.; Diaz-Torres, L. a.; Salas, P.; Vega-Gonzalez, M.; Angeles-Chavez, C. Blue
and red emission in wide band gap BaZrO3:Yb3+,Tm3+. Materials Science and Engineering: B 2010,
174, 169–173.
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R.; Varela, J. a.;
of very intense visible green photoluminescence in BaZrO3 powders. Journal of Applied Physics 2008,
103, 063527.
(231) Moreira, M. L.; Glaucia, P.; Buzolin, C.; Longo, V. M.; Nicoleti, N. H.; Sambrano, J. R.; Li, M.
S.; Varela, A.; Química, I. De; Paulista, U. E.; Box, P. O. Joint Experimental and Theoretical Analysis
of OrderÀDisorder Effects in Cubic BaZrO 3 Assembled Nanoparticles under Decaoctahedral Shape.
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(233) Moreira, M. L.; Gurgel, M. F. C.; Mambrini, G. P.; Leite, E. R.; Pizani, P. S.; Varela, J. A.;
Longo, E. Photoluminescence of Barium Titanate and Barium Zirconate in Multilayer Disordered Thin
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R
u † J u
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(234) Moreira, L.; Andre, J. Synthesis of Fine Micro-sized BaZrO3 Powders Based on a
Decaoctahedron Shape by the Microwave-Assisted Hydrothermal & DESIGN 2009. 2009.
(235) Yamanaka, S.; Hamaguchi, T.; Oyama, T.; Matsuda, T.; Kobayashi, S.; Kurosaki, K. H eat
capacities and thermal conductivities of perovskite type BaZrO3 and BaCeO3. 2003, 359, 1–4.
(236) Charrier-Cougoulic, I. Pagnier, T.; Lucazeau, G. Raman Spectroscopy of Perovskite-Type
BaCex Zr1-xO3 (0<x>1). Journal of Solid State Chemistry 1999, 227, 220–227.
(237) Yuan, Y.; Zhang, X.; Liu, L.; Jiang, X.; Lv, J.; Li, Z.; Zou, Z. Synthesis and photocatalytic
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(238) Li, M.; Feng, Z.; Xiong, G.; Ying, P.; Xin, Q.; Li, C. Phase Transformation in the Surface
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Amorphous to Crystalline Phase Transition. 2012.
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Síntesis y caracterización de polímeros magnéticos.
Pablo Arévalo1, Josefa Isasi1,* y José Antonio Molina2
1. Dpto. de Química Inorgánica I, Universidad Complutense de Madrid, Avda Complutense s/n 28040, Madrid
2 Fundación Neurociencias y Envejecimiento. Emilio Carrere 7, 28015, Madrid.
* e-mail: [email protected]; tfno: +34 91 3945215
1. Introducción
El interés por el estudio de los materiales híbridos se ha visto incrementado a lo largo de los años y
han sido las enormes posibilidades de empleo ofrecidas por lo que se conoce como polímeros
magnéticos, las que han forzado su demanda. Las investigaciones llevadas a cabo en este sentido se
dirigen, hoy, hacia el desarrollo y la puesta a punto de nuevos métodos de preparación de polímeros
magnéticos – núcleo asociado a un recubrimiento- en busca de su estabilidad, biocompatibilidad y
biodegradabilidad [1].
En relación a la preparación de los núcleos magnéticos, se ha investigado ampliamente la obtención
de espinelas inversas del tipo MFe2O4 constituidas por nanopartículas que muestran altos valores de
la magnetización a la saturación (Ms) y un comportamiento superparamagnético. Son destacables los
estudios realizados en magnetitas, Fe3O4, en los que se informa sobre la oxidación experimentada
por estos óxidos de hierro para dar fases que contienen una mayor proporción de Fe3+, con especial
influencia en el valor de la Ms y en el comportamiento magnético [2]. Estos problemas se evitan
frecuentemente por sustitución en Fe3O4 de parte del Fe2+ por otros cationes divalentes de tamaño
semejante. La oxidación y la agregación de las nanopartículas superparamagneticas también pueden
prevenirse utilizando un recubrimiento que actué al mismo tiempo modificando las propiedades
superficiales [3].
En este trabajo se exponen los resultados obtenidos en el aislamiento de nanocomposites de
composición MFe2O4 (con M = Fe2+, Co2+, Ni2+) recubiertos de polietilenglicol y chitosán. Para su
caracterización estructural se han empleado técnicas de difracción de rayos X (XRD), espectroscopia
IR y microscopía electrónica de barrido y transmisión (SEM y TEM).
7. Agradecimientos
Los autores agradecen a la Fundación Neurociencias y Envejecimiento (189/2012; 14/2013 y
177/2013) la financiación concedida para el desarrollo de este trabajo.
Referencias
[1]
[2]
[3]
Ting-Yu L., Shang-Hsiu H., Dean-Mo L., San-Yuan C., I-Wei C., “Surface oxidation, size and shape of nanosized magnetite obtained by co-precipitation”. Nano Today, 4, (2009), 52-65.
I. Nedkova, T. Merodiiska, L. Slavov, R.E. Vandenberghe, Y. Kusano, J. Takada, “Biomedical nanoparticle
carriers with combined thermal and magnetic responses”. J. Magn. Magn. Mater., 300, (2006), 358-367.
H. Yin, H.P. Too, G.M. Chow, “The effects of particle size and surface coating on the cytotoxicity of nickel
ferrite”. Biomaterials, 26, (2005), 5818–5826.
Structural and magnetic study of new-layered
oxygen deficient manganese oxides

Raquel Cortés-Gil1,2, Daniel González-Merchante1, M. Luisa Ruiz-González1, José M. Alonso3,
José L. Martínez4, and José M. González-Calbet1,*
1. Departamento de Química Inorgánica, Facultad de Químicas, Universidad Complutense, 28040-Madrid, Spain
2. CEI Campus Moncloa, UCM-Universidad Politécnica de Madrid, 28040-Madrid, Spain
3. Instituto de Magnetismo Aplicado, UCM-CSIC-ADIF, Las Rozas, P.O. Box 155, 28230-Madrid, Spain
4. Instituto de Ciencia de Materiales, CSIC, C/ Sor Juana Inés de la Cruz, 3, 28049-Madrid, Spain
*[email protected]
Manganese related layered compounds belonging to the An+1BnO3n+1 Ruddlesden-Popper (RP) family
(Fig. 1) has attracted much attention in the past two decades due to a variety of emerging phenomena
such as magnetoresistance (MR), metal-insulator transition, magnetoelastic and magnetocaloric
effects… involving intimate couplings of charge, orbital, spin and lattice degrees of freedom. These
couplings result in a complex magnetic phase diagram of ferromagnetic (FM) as well as different
antiferromagnetic (AFM) phases as a function of the doping level, x, and transition temperature [1].
Particular attention has been focused on the behaviour of La2-2xSr1+2xMn2O7 for x around 0.5, where
the ground state changes from FM-conductor to AFM-insulator, being associated to a charge ordering
(CO) state, in which Mn4+ holes are locked into a periodic array [2].
AO(ABO3)n
Rock‐salt
AO
Perovskite
ABO3
n=1
n=2
Figure 1. Structural models for RP series
Compositional variations at the anionic sublattice are scarce compared to other manganese related
perovskite systems in which different superlattices have been described as a consequence of the
ordering on non-occupied oxygen positions [3]. The RP structural type can admit oxygen deficiency for
n=1, i.e., K2NiF4, affecting not only the transition metal oxidation states but also the magnetic and
transport properties of these phases [4]. Nevertheless, not many studies have been focused to n= 2
RP [5], probably due to the difficulty to stabilize ordered RP members higher than n=1. In this sense,
our objective has been to stabilize and characterize new perovskite related oxygen deficient phases in
the La2-2xAE1+2xMn2O7- system (AE=Ca, Sr) where Mn in different oxidation states can coexist.
Polycrystalline samples of LaSr2Mn2O7 and La0.5Ca2.5Mn2O7 composition were prepared using a
conventional ceramic method. Reduced samples were synthesized in a Cahn D-200 electrobalance in
order to precisely control the oxygen content. According to X-ray diffraction, selected area electron
diffraction and high resolution transmission electron microscopy studies, the La2-2xAE1+2xMn2O7
topotactic reduction process has led to the stabilization of new La2-2xAE1+2xMn2O7-phases. Atomic
resolution images of these compounds were obtained in a JEOL JEM ARM 200cFEG electron
microscope. The microscope is dotted with an aberration corrector at the condenser lens allowing
obtaining high annular dark field (HAADF) images with atomic resolution. In a HAADF image the
contrast is usually referred to as Z-contrast imaging since the scattered intensity scales with the
atomic number Z of the elements in the sample. Using this technique the presence of La and AE
ordering as well as some order-disorder phenomena at atomic level has been evidenced. For
instance, a characteristic HAADF image corresponding to La0.5Ca2.5Mn2O6.5 composition (figure 2)
suggests, according to the atomic number of Ca (Z=20) and La (Z=57) (see model at the inset), the
major presence of La at the perovskite block whereas Ca is at the rock-salt layers. Atomically resolved
maps obtained by Electron Energy Loss Spectroscopy (EELS) confirm the above situation, as shown
in figure 2 b-f. In addition, contrast difference at the La positions are observed suggesting order
disorder phenomena in this perovskite columns. Furthermore, EELS studies have allow identifying the
presence of Mn in different oxidation states, depending on the oxygen content, in both Sr and Ca
systems.
(c)
(a)
Spectrum Image
(d)
Spatial Drift
0.39 nm
(e)
1.9 nm
(f)
(b)
Ca‐L2,3
5 nm
I (a.u)
La
Ca
Mn
Mn‐L2,3
La‐M4,5
O‐K
300
400
500
600
700
800
900
Energy Loss (eV)
Figure 2. (a) HAADF image corresponding to La0.5Ca2.5Mn2O6.5. An schematic model for the cationic position has been inserted;
(b) EELS spectra sum, acquired over the area marked in (a), showing the Ca-L2,3, Mn-L2,3 and La-M4,5 and signals; (c) HAADF
image simultaneously recorded to EELS acquisition; (d) mapping obtained for the La-M4,5 signal (e) mapping obtained for the
Ca-L2,3 signal; (f) mapping obtained for the Mn-L2,3 signal.
Magnetization and transport measurements in both systems indicate that they are indeed sensitive to
the oxygen deficiency as observed in the corresponding magnetization and MR graphics for the Sr
system (figure 3). Correlation of the observed behaviour with the different Mn oxidation states is in due
course.
a)
b)
0.35
700
0.30
y = 6.02
0.25
T=5K
y = 7.00
y = 6.95
y = 6.80
600
0.20
0.15
0.10
500
0.05
0.00
50
100
150
200
250
y = 6.50
0.100
0.075
0.050
0.025
0.000
50
100
1.75 0
1.50
1.25
1.00
0.75
0.50
0.25
H = 1000 Oe
0.00
0
50
100
400
300
% MR
M (emu/g)
0.125
0
150
200
250
300
200
300
y = 7.00
100
0
-100
150
T (K)
200
250
300
-150000 -100000 -50000
0
50000
100000 150000
H (Oe)
Figure 3. (a) Magnetization vs temperature representation for La2-2xSr1+2xMn2O7- ( = 0, 0.5, 1); (b) MR vs magnetic field
representation corresponding to La2-2xSr1+2xMn2O7- ( = 0, 0.05, 0.2).
[1] C. D. Ling, J. E. Millburn, J. F. Mitchell, D. N. Argyriou, J. Linton, H. N. Bordallo, Phys. Rev. B 62, 15096,
2000.
[2] D. N. Argyriou, H. N. Bordallo, B. J. Campbell, A. K. Cheetham, D. E. Cox, J. S. Gardner, K. Hanif, A. dos
Santos, G. F. Strouse, Phys. Rev. B 61, 15269, 2000.
[3] R. Cortes-Gil, M. Luisa Ruiz-González, J. M. Alonso, M. Vallet-Regí, A. Hernando, J. M. González-Calbet,
Chem. Eur. J. 13, 4246, 2007.
[4] H. J. Kitchen, I. Saratovsky, M. A. Hayward, Dalton Trans. 39, 6098, 2010.
[5] H. El Shinawi, A Bertha, J. Hadermann, T. Herranz, B. Santos, J. F. Marco, F. J. Berry, C. Greaves, J. Sol.
State Chem. 183, 1347, 2010.
Transesterificación de triacetilglicéridos con metanol
sobre un catalizador MO/SiO2 (M= Sr)
1,*
1,2
1,2
Ana Medina , Jesús Valencia
Univeridad Nacional de Colombia, Departamento de Química, Laboratorio de Catálisis Heterogénea, Grupo de Aplicaciones
Fisicoquímicas del Estado Solido (AFES), Ciudad Universitaria, Transversal 38 No. 40-04, Bogotá, Colombia
*[email protected]
1. Introducción
La transesterificación es una reacción que tiene lugar entre un ester de alto peso molecular
(triacilglicerido) y un alcohol liviano (metano, etanol) para producir una mezcla de esteres y
[1]
glicerol. Entre los materiales más promisorios para el desarrollo de esta reacción se hallan los
catalizadores heterogéneos sólidos, ácidos y /o básicos, nuevos materiales que posibilitan la separación
del producto sin uso de disolventes, facilitan la regeneración y reciclaje del catalizador, la regulación del
carácter corrosivo y la disminución de costos. Los óxidos de metales alcalinotérreos se utilizan como
catalizadores heterogéneos sólidos básicos, estos presentan sitios de alta densidad electrónica, lo que
los hace más reactivos en los sitios básicos de Lewis, generando mayor selectividad al ser empleados
como catalizadores en la reacción de transesterificación de triacilgliceridos evitando las reacciones
[2]
colaterales de saponificación y generando la recuperación parcial del catalizador empleado para tal fin.
Tomando en cuenta lo anterior, se preparó un catalizador sólido heterogéneo básico, basado en un óxido
de estroncio soportado sobre una sílica mesoporosa del tipo de MCM 41. Los soportes de sílica
estructurada se prepararon utilizando protocolos de síntesis hidrotérmica en presencia de Bromuro de
hexadeciltrimetilamonio (CTAB) como director de estructura. Para tal efecto se modificaron algunas
variables tales como la naturaleza del precursor de silicio, la temperatura del medio de reacción, el
[3]
tiempo de reacción, y el tratamiento térmico del material . El soporte escogido para la preparación del
catalizador fue la MCM 3a, el cual presente el mejor comportamiento al ser calcinado a 650°C (Fig.1). Los
catalizadores preparados de oxido de estroncio soportados sobre la sílica mesoporosa se trabajaron en
[4]
dos cargas diferentes 9 y 16% . Estos sólidos se caracterizaron con técnicas como DRX, Fisisorción de
Nitrógeno a 77K (Fig. 2), TEM (Fig. 3), SEM y Raman. Los resultados mostraron que el catalizador
SrO/MCM41 al 16% presenta un 93% de conversión de triolina hacia otros productos del biodiesel (Fig.4).
Este comportamiento se atribuye a la carga depositada dentro del soporte lo cual contribuye a la
formación y distribución de los sitios activos básicos dentro del catalizador.
Figuras
Fig. 1: Patrones de DRX de las muestras
(a) SrO/MCM-41 (9%),(b) SrO/MCM-41 (16%) y (c) MCM-3a
Fig. 2: Isotermas de adsorción- desorción de
nitrógeno del catalizador SrO/MCM-41 (16%)
1
Fig. 3: TEM del catalizador SrO/MCM-41 (16%)
Fig. 4: Concentración (mM) de mono-, di- y triglicéridos en relación
con el tiempo de reacción del catalizador SrO/MCM-41 (16%)
Conclusiones
•
•
•
•
El soporte seleccionado para los catalizadores (MCM-3a) presenta estructura hexagonal, grupo P6m,
2 -1
con parámetros de red a0 igual a 4,92 nm, área superficial de 726 m g y volumen de poro de 0,602
3 -1
cm g .
Los catalizadores de óxido de estroncio soportados sobre una sílica del tipo MCM-41 preparados por
el método de impregnación y posterior tratamiento térmico, mostraron un comportamiento estable,
conservando una fuerte interacción entre el SrO y la sílica, lo cual evito la lixiviación de los sitios
activos en la fase metanolica de la reacción de transesterificación.
El efecto del soporte (MCM-3a) sobre los catalizadores de SrO/MCM41 al 9% y 16% de carga de Sr,
provocaron un aumento en el área superficial de cada uno de ellos, generando una mayor
distribución del óxido de estroncio en la superficie y dentro de las cavidades tubulares del soporte,
incrementando de esta forma los sitios activos básicos de los catalizadores, haciéndolos más
eficaces en la reacción de transesterificación.
El catalizador SrO/MCM-41 (16%) mostro las mejores conversiones de triglicéridos hacia otros
productos del biodiesel.Las condiciones de reacción de la trioleína con metanol escogidas para el
análisis de actividad catalítica resultaron ser las más adecuadas para obtener los mejores resultados
en la transformación de triglicéridos a diglicéridos y monoglicéridos.
Agradecimientos
A la Universidad Nacional de Colombia- Sede Bogotá, a través del proyecto “Desarrollo de sistemas
catalíticos basados en materiales cerámicos y biopoliméricos para la transformación de aceites
vegetales” Código QUIPU 20501005406 financiado mediante la Convocatoria Bicentenario 2009 para
proyectos de investigación.
Referencias
[1] M. C. G. Albuquerque, I. Jiménez-Urbistondo, J. Santamaría-González, J. M. Mérida-Robles, R. Moreno-Tost, E. RodríguezCastellón, A. Jiménez-López, D. C. S. Azevedo, C. L. Cavalcante Jr and P. Maireles-Torres, Applied Catalysis A: General 2008, 334,
35-43.
[2] A. Corma and S. Iborra in Optimization of Alkaline Earth Metal Oxide and Hydroxide Catalysts for Base-Catalyzed Reactions,
Vol. Volume 49 Eds.: C. G. Bruce and K. Helmut), Academic Press, 2006, pp. 239-302.
[3] a) D. Kumar, K. Schumacher, C. du Fresne von Hohenesche, M. Grün and K. K. Unger, Colloids and Surfaces A:
Physicochemical and Engineering Aspects 2001, 187-188, 109-116; b) M. Grün, K. K. Unger, A. Matsumoto and K. Tsutsumi,
Microporous and Mesoporous Materials 1999, 27, 207-216.
[4] a) X. Liu, H. He, Y. Wang and S. Zhu, Catalysis Communications 2007, 8, 1107-1111; b) X. Liu, X. Piao, Y. Wang, S. Zhu and H.
He, Fuel 2008, 87, 1076-1082.
2
Er, Yb:NaY2F5O up-conversion nanoparticles: a new
tool for lifetime thermometry in the biological
range
Ol.A. Savchuk,1,* P. Haro-González,2 J.J. Carvajal,1 D. Jaque,2 J. Massons,1 M. Aguiló1, and F.
Díaz1
1.
Física i Cristal·lografia de Materials i Nanomaterials (FiCMA-FiCNA)- EMaS, Universitat Rovira i Virgili (URV),
Campus Sescelades, C/ Marcel.li Domingo s/n, E-43007, Tarragona, Spain
2. Fluorescence Imaging Group, Departamento de Física de Materiales C-04 – Instituto Nicolás Cabrera, Universidad
Autónoma de Madrid, C/ Francisco Tomás y Valiente 7, E-28049, Madrid, Spain
corresponding author: [email protected]
*
Introduction
Luminescent thermometry has attracted special attention in recent years, especially due to it’s
high spatial resolution and significant sensitivity. Moreover, the importance of luminescent
thermometry in biomedical areas is enormous, since a variety of cellular events occured with
temperature changes [1]. Lifetime-based luminescent thermometry offers advantages when compared
to other luminescent approaches, since problems with movement, shading and light distribution of the
sample can be eliminated [2]. Er3+ doped and Yb3+, Er3+ co-doped up-conversion systems have
received a number of attention in bioimaging, displays application and nanothermometry [3-4], since
they present the ability to be pumped in the near infrared and emit in the visible. In 2010 Vetrone et al.
showed that fluorescent Er,Yb:NaYF4 nanoparticles can be successfully used as nanothermometers
measuring temperature changes in individual cancer cells up to their thermally induced death [5], for
instance.
In this work we present the comparison of temperature dependent fluorescent lifetime at the
biological range of Er,Yb:NaYF4 and Er,Yb:NaY2F5O nanoparticles. Er,Yb:NaY2F5O nanocrystals show
great potentiality as thermal sensors at the nanoscale for biomedical applications due to the
incorporation of additional non-radiative relaxation mechanisms that shorten the emission lifetime
generated by the oxygen present in the structure. Here we report ex-vivo temperature determination
by laser induced heating in chicken breast using lifetime-based thermometry in these up-conversion
nanoparticles.
Experimental section
Fluorescence lifetime of Er,Yb:NaYF4 and Er,Yb:NaY2F5O nanoparticles was measured by
exciting the samples with an optical parametric oscillator (Opotek Vibrant HE 355 II+UV) at 980 nm
with a pulse duration of 6 ns and a repetition frequency of 10 Hz. The fluorescent light emitted from
the samples was collected with objectives, transferred to the monochromator for selection of specific
wavelengths, and finally detected using a Hamamatsu R928 photomultiplier. The decay of the signal
was measured as a function of time with a digital oscilloscope. Data was transferred to a computer for
later analysis.
For the lifetime thermal sensing calibration, Er,Yb:NaYF4 and Er,Yb:NaY2F5O nanoparticles
were introduced in to Linkam THMS 600 heating stage. For ex-vivo temperature determination, an
aqueous solution containing luminescent up-conversion nanoparticles was injected into a μ-channel
and placed into a chicken breast. Then, the chicken breast with μ-channel inside was illuminated
simultaneously with two laser beams in a double beam confocal microscope. The heating laser,
emitting at 1090 nm was focused into the channel using objectives. In order to prove the thermal
sensing system based on lifetime measurements, a second laser with emission at 980 nm was
focused on the top of the channel, spatially overlapping with the heating spot. The generated
fluorescence by nanoparticles was collected by the same objective and after passing filter was
focused into a multiplier tube connected to a digital oscilloscope.
Results
We studied the temperature dependent fluorescence lifetime of Er,Yb:NaYF4 and
Er,Yb:NaY2F5O nanoparticles in the biological range of temperatures (25 – 60 ºC). In both cases with
increasing temperature, the lifetime emission decay rate became faster. However, the shortening of
the decay time in Er,Yb:NaY2F5O nanoparticles is more evident (see Fig. 1a). The observed
temperature induced lifetime reduction is a consequence of the activation of phonon-assisted
processes and of multiphonon decays driven by temperature increments. Temperature-dependent
normalized lifetime decreased almost linearly with temperature. In order to have a practical indicator of
temperature using lifetime measurements, it is highly desirable to have a linear dependence with
temperature since it simplifies the calibration of the system. Thus, in this case we have excellent
temperature sensors, especially in the case of Er,Yb:NaY2F5O nanoparticles where the slope of the
linear fit is higher (see Fig. 1b).
In order to demonstrate the potentiality of lifetime thermometry using up-conversion
nanoparticles, we have performed an ex vivo temperature determination experiment in chicken breast
that was heated by an additional laser beam. Er,Yb:NaY2F5O nanoparticles were dispersed in water,
and injected into a fresh chicken breast within a depth of 1 mm. The clear evolution of the lifetime
indicated the progressive heating of the tissue surrounding the nanoparticles by the effect of the
increasing power of the 1090 nm laser. These data were used to determine the temperature inside the
chicken breast, the sub-tissue temperature, as a function of the laser heating power.
Figure 1. (a) Fluorescence decay curves of the 545 nm emission line of Er,Yb:NaY2F5O nanoparticles at 25 and 60 ºC, and (b)
normalized lifetime values as a function of temperature.
Conclusion
In conclusion, we have reported ex-vivo temperature determination based on fluorescence
lifetime using up-conversion nanoparticles. Ex-vivo temperature measurements were in a good
agreement with theoretical predictions showing the potentiallity of Er,Yb:NaY2F5O nanoparticles as
lifetime-based thermometers.
Acknowledgements
This work was supported by the Spanish Government under projects No. MAT2011-29255C02-02 and TEC2010-21574-C02-02, the Catalan Government under project No. 2009SGR235, and
the European Commission within the Seventh Framework Program under project No. FP7-SPA-2010263044. O.A. Savchuk is supported by Catalan Government through the fellowship 2013FI_B 01032.
References
[1]. B. Hildegrandt, P. Wust, O. Ahlers, A. Dieing, G. Sreenivasa, T. Kerner, R. Felix, H. Riess, “The cellular and
molecular basis of hyperthermia”. Crit. Rev. Oncol. Hemat., 43 (2002) 33-56.
[2]. P. Haro-Gonzalez, L. Martinez-Maestro, I. R. Martin, J. Garcia-Sole, and D. Jaque, “High sensitivity
fluorescence lifetime thermal sensing based on CdTe quantum dots”. Small, 8, 17, (2012), 2652-2658.
[3]. Nikifor Rakov, Glauco S. Maciel, “Three photon upconversion and optical thermometry characterization of
3+
3+
Er :Yb co-doped yttrium silicate powders”. Sensors and Actuators B, 164 (2012), 96-100.
[4]. Lorenz H Fischer, Gregory S. Harms, and Otto S. Wolfbeis, “Upconverting nanoparticles for nanoscale
thermometry”. Angew. Chem. Int. Ed. 50, (2011), 4546-4551.
[5]. F. Vetrone, R. Naccache, A. Zamarron, A. Juarranz de la Fuente, F. Sanz-Rodriguez, L. M. Maestro, E. M.
Rodriguez, D. Jaque, J. G. Sole, and J. A. Capobianco, “Temperature sensing using fluorescent
nanothermometers”. ACS Nano 4, 6, (2010), 3254-3258.
Upconversion processes and light color selection
in Yb-sensitized Pr-doped fluoride-based
hydrothermal nanoparticles
Concepción Cascales* and Carlos Zaldo
Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, c/ Sor Juana Inés de la Cruz 3,
E-28049 Madrid, Spain
*[email protected]
c)
a)
40 µm
120 nm
d)
b)
150 nm
120 nm
Fig.1. Images of Yb-sensitized Pr-doped fluoride-based
hydrothermal samples: a) SEM micrograph of micronsized bundles of Y6O5F8, and TEM views of: b) individual
nanotubes that constitute the bundles of Y6O5F8, c)
Nanoparticles of β-NaYF4, d) Nanoparticles of YF3.
UC INTENSITY (arb. u.)
Research on trivalent lanthanide (Ln3+)-based micro/nano upconverting particles (Ln-UCPs) is
nowadays stimulated by their successful exploitation in fields related to security, imaging and sensing,
which include uses as selective biological probes and cellular thermometers, and in lighting
technologies, namely for color displays and in the development of white light sources. The
advancement of such applications is supported by both the availability of inexpensive near-infrared
(NIR) diode lasers (DL) as excitation sources, and by the current development of effective chemical
routes to produce micro/nano Ln-UCPs. Moreover, any of the above practical purposes requires high
luminescence efficiency from Ln-doped UC materials. This need can be satisfied in matrices with low
phonon energies, which minimize multiphonon de-excitation probabilities, and thus non-radiative
relaxations. From this point of view, oxyhalide- and halide-based hosts, whose cut-off phonon
energies are typically lower than oxides, are interesting UC systems.
3+
3+
In this work we study the room-temperature UC luminescence of Yb -sensitized Pr -doped
samples of Y6O5F8, β-NaYF4 and YF3 under NIR DL excitation.
Yb3+ (2 mol %)-sensitized Y6O5F8, β-NaYF4 and YF3 particles doped with Pr3+ (0.2 up to 2 mol %)
have been prepared by hydrothermal syntheses carried out at 185 ºC during 24 h, under autogenous
pressure, see SEM and TEM images in Figure 1. Under ∼978 nm diode laser excitation the
upconverted light emitted by these samples presents different spectral distribution (see Figure 2 for
0.2 mol% Pr3+ doped samples), which has been explained in each case through specific pathways for
populating 3P2, 3P1(+1I6), 3P0 and 1D2 emitting levels. Whereas only green to bluish-green upconversion
emissions are achieved with Pr-doped Yb:β-NaYF4 and Yb:YF3 fluorides, Pr-doped Yb:Y5O6F8
oxyfluoride allows the selection of the color of the upconverted light through the control of the Pr3+
concentration and by the excitation power density.
a)
Pr, Yb:Y6O5F8
b)
Pr, Yb:β-NaYF4
c)
Pr, Yb:YF3
500
600
700
800
WAVELENGHT (nm)
Fig.2. Room temperature upconversion spectra under
-2
diode laser excitation at ∼978 nm with 350 W·cm
power density of Yb-sensitized (2 mol%) Pr-doped
(0.2 mol%) samples: a) Y6O5F8, b) β-NaYF4, c) YF3.
Acknowledgement: This work was supported by the Spanish Ministry of Economy and
Competitiveness under project MAT2011-29255-C02-01.
Variable-temperature IR spectroscopy for ranking
Brønsted acidity
*
Montserrat Rodriguez Delgado , Carlos Otero Arean
Department of Chemistry, University of the Balearic Islands, 07122 Palma de Mallorca, Spain
*[email protected]
1. Introduction
Solid acids having a large specific surface area, such as protonic zeolites and related porous solids,
are often used as catalysts in a wide range of chemical processes, which span the petrochemical
industry, methanol to olefin conversion and the production of fine chemicals, to quote some of the
most common examples. The strength of their catalytically active Brønsted-acid sites is a main factor
determining performance of such porous solids; hence the need of having a reliable method to rank
surface acidity of solid acids.
However, at variance with aqueous acid solutions for which the corresponding pKa provides a
quantitative measure of acid strength, no clear-cut measurement has yet been found for solid acids.
The most common method currently being used relies on adsorption of a weak base (such as CO or
dinitrogen) which forms hydrogen-bonded OH···CO (or OH···NN) adsorption complexes with the
Brønsted-acid hydroxyl groups of the solid. The adsorption complex can easily be monitored by IR
spectroscopy as hydrogen bonding brings about a distinctive bathochromic shift, Δν(OH), of the O−H
stretching mode of the hydroxyl group. The magnitude of Δν (OH) (for any given weak base) is taken to
be an indicator of relative Brønsted acidity when ranking solid acids [1]. The question, however, arises
as to whether Δν(OH) really correlates with acid-base interaction energy or not. We report herein on
recent studies showing that such a correlation cannot be taken for granted.
2. Methods and results
Adsorption of CO and dinitrogen on several protonic zeolites belonging into different structural groups
was studied by means of variable-temperature IR (VTIR) spectroscopy [2] (which affords simultaneous
0
determination of Δν(OH) and standard adsorption enthalpy, ΔH ) and adsorption calorimetry. As an
example, results obtained for CO adsorption on H-FER and H-MCM-22 (MWW structure type) are
given in Figures 1 and 2. Corresponding results for other protonic zeolites (some of them taken from
the published literature) are summarized in Table 1.
-1
(OH) = -297 cm
2
3
4
5
6
7
8
9
0,1
-0,1
-0,2
-0,3
8
7
6
5
4
3
2
1
3605
3600
-1
(OH) = -320 cm
2 1
3
4
5
9
-1
1000/T (K )
4,0
B
0,1
0,0
4,5
5,0
5,5
6,0
4
ln {/[(1-)p]}
Absorbance
0,2
0,2
1
6
7
8
9
10
11
0,0
11
10
9
8
7
6
-0,1
2
0
0
H = -28,4 kJ mol
-2
3400
Wavenumber / cm
3200
-1
-1
3000
1
-0,2
-1
4,5
5
4
3
2
3625
3600
1000/T (K )
5,0
5,5
6,0
0
ln {/[(1-)p]}
A
Absorbance
0,3
3500
3400
-1
-2
-3
0
H = -22,5 kJ mol
-4
3300
3200
Wavenumber / cm
3100
-1
3000
-1
Fig. 1: (A) Representative variable-temperature IR spectra (O−H stretching region) of CO adsorbed on H-FER.
From 1 to 9, temperature goes from 167 to 224 K; and equilibrium pressure from 0.57 to 1.75 mbar. (B)
Representative variable-temperature IR spectra (O−H stretching region) of CO adsorbed on H-MCM-22. From 1
to 11, temperature goes from 154 to 214 K; and equilibrium pressure from 6.52 to 9.24 mbar. The spectra are
shown in the difference mode (zeolite blank subtracted). Insets show the corresponding van’t Hoff plots.
30
Table 1. Experimental data for CO hydrogen bonding in
protonic zeolites.
Structure -Δν(OH)
-ΔH0
Zeolite
Ref.
type
(cm-1)
(kJ mol-1)
H-Y
FAU
275
25.6
[3]
-1
Qdiff (kJ mol )
25
20
15
10
H-FER
H-MCM-22 first run
H-MCM22 second run
5
0
0,00
0,05
0,10
0,15
H-ZSM-5
MFI
303
29.4
[3]
H-FER
FER
297
28.4
[4]
H-MCM-22
MWW
320
22.5
This work
H-MCM-56
MWW
316
20
This work
0,20
Coverage ()
Fig. 2: Adsorption heat of CO on H-FER (squares) and
H-MCM-22 (circles) measured by calorimetry at 303 K, as
a function of coverage.
3. Discussion and Conclusions
Experimental results summarized in Table 1 clearly show that while for some protonic zeolites (H-Y,
0
H-FER and H-ZSM-5) there is a direct correlation between standard adsorption enthalpy (ΔH ) and
bathochromic shift (Δν(OH)) of the O−H stretching mode in the corresponding hydrogen-bonded
(OH···CO) adsorption complex, the same does not hold in the case of other zeolites. Thus, MWW
0
structure-type zeolites show a distinctively lower (absolute) value of ΔH (for CO adsorption) than HFER and H-ZSM-5; and yet the (absolute) value of Δν(OH) (after hydrogen bonding with the probe
molecule) is significantly larger for the protonic zeolites of the MWW group. Measurements performed
by using dinitrogen as the probe molecule confirmed the results obtained with CO, in the sense that a
0
direct correlation between Δν(OH) and ΔH was not always observed. Taken as a whole, the obtained
results clearly show that the usual practice of ranking Brønsted-acid strength of solids by their O−H
frequency shift probed by and adsorbed weak base can be misleading. Determination of the enthalpy
change involved in formation of the corresponding hydrogen-bonded adsorption complex seems to be
a more reliable instrumental method.
References
[1]
[2]
[3]
[4]
E.A. Paukshtis, E.N. Yurchenko. Russ. Chem. Rev., 52, (1983), 242.
E. Garrone, C. Otero Arean. Chem. Soc. Rev., 34, (2005), 846.
C.O. Arean. J. Mol. Struct., 880, (2008), 31.
P. Nachtigall, O. Bludsky, L. Grajciar, D. Nachtigallova, M.R. Delgado, C.O. Arean. Phys. Chem. Chem.
Phys., 11, (2009), 791.