Publication: Efectos del orden estructural en las propiedades eléctricas y magnéticas de óxidos multi-catiónicos con estructura derivada de la perovskita
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2019-12-16
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Universidad Complutense de Madrid
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Abstract
Los óxidos mixtos con estructura tipo perovskita, de fórmula general ABO3, forman familias de compuestos de gran interés tanto desde el punto de vista científico como tecnológico. Esta estructura ofrece una gran variedad de posibilidades de sustitución de cationes en las posiciones A y/o B para formar sistemas complejos con dos o más tipos de cationes en ambas posiciones. Esta flexibilidad composicional está asociada a una flexibilidad estructural que permite acomodar la variedad de tamaños y estados de oxidación de los diferentes cationes. En este sentido, el orden de los cationes en posiciones A y B de óxidos con estructura derivada del tipo perovskita ha generado un gran interés en los últimos años debido a su gran impacto sobre las propiedades eléctricas y magnéticas, lo que los convierte en materiales con un gran interés funcional. Entre los diferentes modelos de orden que se pueden establecer, el orden de tipo laminar de los cationes en las posiciones A ha sido poco explorado por su mayor dificultad de estabilización. Un método eficaz para inducir este tipo de orden consiste en la co-existencia de vacantes aniónicas, que también pueden llegar a ordenarse, estableciendo un orden laminar adicional dentro de la subred aniónica con interesantes implicaciones en las propiedades de estos óxidos. El objetivo general de este trabajo ha consistido en preparar óxidos con estructura derivada de la perovskita, con orden laminar en ambas subredes, catiónica y aniónica, y estudiar los efectos del orden estructural en sus propiedades eléctricas y magnéticas...
Mixed oxides with perovskite-type structure, of general formula ABO3, form families of compounds of great interest, not only from the scientific point of view but also from the technological one. This crystal structure offers a great variety of possibilities of cation substitution in the A and/or B sites to form complex systems with two or more different types of cations in both positions. The compositional suppleness of the perovskite is associated with its structural flexibility, which allows to accommodate a variety of sizes and oxidation states of the different cations. In this way, cationic ordering in the A and B sites of perovskite-related-type oxides has generated a great interest in the last few years due to its high impact on the electric and magnetic properties, which makes them promising multifunctional materials. Among the different ordering patterns which can be established, layered-type ordering in the A sites has been less explored because its stabilization is rather challenging. An effective approach to induce this kind of ordering consists of the co-existence of anionic vacancies, which can be located in particular positions of the structure leading to additional layered ordering within the anionic sublattice with tremendous implications in the properties of these oxides. In this work, the preparation of novel perovskite-related-type oxides was carried out with the aim of layered ordering within both cationic and anionic sublattices, and to study the effect of the structural ordering on the electric and magnetic properties...
Mixed oxides with perovskite-type structure, of general formula ABO3, form families of compounds of great interest, not only from the scientific point of view but also from the technological one. This crystal structure offers a great variety of possibilities of cation substitution in the A and/or B sites to form complex systems with two or more different types of cations in both positions. The compositional suppleness of the perovskite is associated with its structural flexibility, which allows to accommodate a variety of sizes and oxidation states of the different cations. In this way, cationic ordering in the A and B sites of perovskite-related-type oxides has generated a great interest in the last few years due to its high impact on the electric and magnetic properties, which makes them promising multifunctional materials. Among the different ordering patterns which can be established, layered-type ordering in the A sites has been less explored because its stabilization is rather challenging. An effective approach to induce this kind of ordering consists of the co-existence of anionic vacancies, which can be located in particular positions of the structure leading to additional layered ordering within the anionic sublattice with tremendous implications in the properties of these oxides. In this work, the preparation of novel perovskite-related-type oxides was carried out with the aim of layered ordering within both cationic and anionic sublattices, and to study the effect of the structural ordering on the electric and magnetic properties...
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Química Inorgánica I, leída el 31/10/2019