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Contenido archivado el 2022-12-23

Experimental and theoretical investigations on phase transitions in new ceramic oxides

CORDIS proporciona enlaces a los documentos públicos y las publicaciones de los proyectos de los programas marco HORIZONTE.

Los enlaces a los documentos y las publicaciones de los proyectos del Séptimo Programa Marco, así como los enlaces a algunos tipos de resultados específicos, como conjuntos de datos y «software», se obtienen dinámicamente de OpenAIRE .

Resultados aprovechables

This research project centres mainly on the general theme of structural, electronic and magnetic phase transitions in the new superconducting oxides of Y-Ba-Cu-O systems (123 systems). Results: -It is settled up the topotactic-like technology for the low-temperature processing of the oxygen-equalized and order-stabilized pair samples of YBCO (k-pairs) where the key variable is the oxygen ordering in the Cu(1)Ox chain. The structural, electronic, optical and NMR properties of k-pairs, have been investigated in a comparative way. The k-pair technology can be extended principally to the field of off-stoichiometry oxides where the physical properties being crucially dependent on the oxygen content are difficult to investigate in a comparative way using the conventional single-sample strategy. -The synthesis of 12zCu3O7-x samples and the investigation of the barium nonstoichiometry by structural analysis, measurements of resistivity and diamagnetic properties, the reflectivity spectra in them, have proved the idea of a superstructure generation and the formation of two-three and four-fold coordinated Cu(1) atoms with O(1) and O(4) oxygen positions. - The phase-transition-induced reconstruction of the vibrational spectra in 123 systems is investigated theoretically in the transferable shell model. The new infrared Raman optically active phonon modes are predicted. The low-frequency dielectric dispersion in the highordered phases is calculated. The Raman and infrared reflectivity experiments in k-pairs ceramic samples are performed and the influence of oxygen content and ordering on the fhonon spactra are studied.The evidences of 0II and 0III superstructures in k-pairs are established. We believe that this results open a new prospects for the superstructure characterization and for the monitoring of the oxigen ation-deoxi ge nation kinetics in YBCO. -The results are reported in 16 scientific publications and at 19 international conferences.

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