Structural characterization and phase transition of cobalt doped titanates

NAPOLITANO, FEDERICO; BAQUÉ, LAURA; SOLDATI, ANALIA L.; ACUÑA, LEANDRO; LAMAS, DIEGO; SERQUIS, ADRIANA C.

Campinas

Congreso; RAU 22 - Reunión Anual Usuarios LNLS/CPEM; 2012

Laboratorio Nacional de Luz Sincrotrón

Lanthanum strontium titanates (LST) based oxides are good candidates to be utilized as symmetrical fuel cells (SFC) electrode materials because their good mixed conductivity (electronic and ionic) and electrocatalytic activity for both oxygen reduction and hydrogen oxidation reactions. However, it has been reported that the structure of this compound is strongly dependent on synthesis conditions leading to an apparent lack of reproducibility. In this work, structural characterization of La0.4Sr0.6Ti1−yCoyO3±d (0.0 < y < 0.5) by powder X-ray diffraction at room temperature is reported. In addition, a first study of these properties (y = 0.3 sample) at 750 C under oxidizing (synthetic air) and reductive (5%H2/95%He) atmospheres is reported. A phase transition was found between room temperature and 750 C in oxidizing atmosphere, changing from rhomboedral to cubic structure. Also, a cubic structure with a strong lattice parameter shift was observed when atmosphere was switched from oxidizing to reductive conditions at 750 C. High temperature structural characterization at these atmospheres is required to understand electrochemical properties of SFC electrodes under working conditions.