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Layered-type perovskites have been the focus of research in the last few years due to their outstanding properties as solid oxide fuel cell oxygen electrodes. The synthesis of a new (GdBa)0.8Ca0.4Co0.6Fe1.4O6-d layered perovskite as a single phase as well as the crystal structure determination and catalytic activity for oxygen reduction is reported. Highly advanced methods of transmission electron microscopy have been used for structure determination at atomic resolution. The oxide shows a complex modulation of the crystal structure associated with layered-type ordering of the Gd, Ba and Ca atoms in combination with formation of different coordination polyhedra of the Fe and Co atoms. Location of the anion vacancies within particular highly ion-conducting layers of the crystal structure has been achieved by phase image reconstruction. This material exhibits excellent electrochemical behaviour and thermal stability for use as an air electrode in IT-SOFCs., Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2022) © 2022 The Authors. Published by Elsevier Inc. This work has been supported by the Madrid Government (Comunidad de Madrid- Spain) under the Multiannual Agreement with Complutense University in the line Program to Stimulate Research for Young Doctors in the context of the V PRICIT (Regional Programme of Research and Technological Innovation): Project PR65/19–22459. We thank to Spanish Ministry for Science and Innovation (MCIN/AEI/10.13039/ 501100011033) for granting the projects PID2020-112848RB-C21 and RTI2018-094550-A-I00. We also wish to express our gratitude to the ILL and CNME technical staff for providing the facilities for neutron poder diffraction experiment and SEM, respectively., Perovskite La_0.3Ca_0.7Fe_0.7Cr_0.3O_(3-delta) (LCFCr) is a mixed ionic and electronic conductor (MIEC) that can be employed as an electrode material in reversible solid oxide fuel cells (RSOFCs). In this work, an ultra-fast (15 min) one-step microwave (MW)-assisted combustion synthesis route has been developed to obtain phase pure and highly crystalline LCFCr powder. The synthesized powders exhibited a sponge-like microstructure with increased electrochemical reaction sites. Neutron thermodiffraction analysis revealed a structural transition above 500 degrees C from the room temperature (RT) orthorhombic Pnma to a rhombohedral R3c perovskite phase. The oxygen vacancy concentration was found to increase from delta = 0.272(7) at RT to delta = 0.333(5) at 900 degrees C. Furthermore, a 3-dimensional G-type antiferromagnetic structure was detected at RT. MW-sintering of pressed green ceramic pellets was carried out at 950 degrees C for 1 h, using a MW-transparent quartz fiber crucible or alternatively a SiC crucible acting as a MW-absorber. Impedance spectroscopy data on sintered ceramic pellets revealed electronic inhomogeneity as demonstrated by the occurrence of three dielectric relaxation processes associated with two grain boundary (GB)-like contributions and one bulk. The dielectric inhomogeneity encountered may be restricted to the extrinsic GB areas, which may be rather thin. More homogeneous dielectric properties of the GBs were found in the pellet that was sintered in the SiC crucible., Ministerio de Ciencia e Innovación (MICINN) / FEDER, Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid / Universidad Complutense de Madrid (UCM), Depto. de Física de Materiales, Depto. de Química Inorgánica, Fac. de Ciencias Físicas, Fac. de Ciencias Químicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2021), The antiferromagnetic behavior of Fe3+ oxides of composition RE1.2Ba1.2Ca0.6Fe3O8, RE2.2Ba3.2Ca2.6Fe8O21, and REBa2Ca2Fe5O13 (RE = Gd, Tb) is highly influenced by the type of oxygen polyhedron around the Fe3+ cations and their ordering, which is coupled with the layered RE/Ba/Ca arrangement within the perovskite-related structure. Determination of the magnetic structures reveals different magnetic moments associated with Fe3+ spins in the different oxygen polyhedra (octahedron, tetrahedron, and square pyramid). The structural aspects impact on the strength of the Fe-O-Fe superexchange interactions and, therefore, on the Neel temperature ( ́ TN) of the compounds. The oxides present an interesting transition from three-dimensional (3D) to two-dimensional (2D) magnetic behavior above TN. The 2D magnetic interactions are stronger within the FeO6 octahedra layers than in the FeO4 tetrahedra layers., Ministerio de Ciencia e Innovación (España), Ministerio de Educación, Cultura y Deporte (España), Institute for Chemical Research in Kyoto University, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Ministerio de Economía y Competitividad (España), European Commission, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

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...

The influence of rare earth (RE) elements on superconducting properties of the transition element (TE)-substituted TExCu1−xSr2RECu2Oy cuprates has not been sufficiently emphasized so far. In the case of molibdocuprates with the general formula Mo0.3Cu0.3Sr2RECu2Oy, all the RE element containing compounds except La, Ce, and Lu can be prepared at room pressure. The influence of the crystal structure on the superconducting properties after ozone oxidation of the present system is reported selecting three groups of RE elements attending to their different atom sizes: small (Yb and Tm), medium (Gd), and big (Nd and Pr). Advanced transmission electron microscopy, various diffraction techniques, and spectroscopic analysis have been used to demonstrate that the increase of structural disorder complemented with a decrease in the hole content play a major role in the vanishing of superconductivity within the present system., Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub