Speciation of Ti and Co in nanostructured titanates of composition (La,Sr)Ti1-yCoyO3-d used as electrodes in symmetric SOFCs

SOLDATI, ANALIA L.; NAPOLITANO, FEDERICO; GECK, JOCHEN; LAMAS, DIEGO; SERQUIS, ADRIANA C.

Campinas

Encuentro; RAU23_Reunión Anual de Usuarios de LNLS; 2013

Laboratorio Nacional de Luz Sincrotrón

ABO3 perovskites with Ti in the B site are promising materials for new solid ox-ide fuel cells (SOFC) with symetric designs. These compounds, widely recognizedas good anodes, enhance their ionic conductivity by replacing small amounts of Tiwith other transition metals. Thus, enabling their use as SOFC cathodes. However,substitution of polyvalent atoms in the ABO3 structure might induce oxidation andreduction processes in the components or even creation of vacancies of oxygen orA atoms to compensate for charge and size changes. We investigated here the per-ovskite family La0:4Sr0:6Ti1¡yCoyO3¡± with (0:1 · y · 0:5 (LSTC) prepared by achemical route of citrates and sintered at 750 ±C and 1100 ±C. XANES and EXAFSanalysis at the transition metals K-edges supported by Density Functional Theorycalculations reveled that Co dramaticaly changes its oxidation state, while Tita-nium stays as Ti4+, as the dopant fraction increases. This seems to be independentof synthesis parameters as the sinterization temperature or grain size. These resultsare of signi¯cant importance to understand the charge compensation mechanismsin this system and will allow to ¯nd the optimal LSTC composition for symetricfuel cell designs.