Lanthanum–calcium chromites–titanates as possible anode materials for SOFC

The series of perovskite-type compounds La1−xCaxCr1−yTiyO3−δ with x=0–1 and y=0–1 were synthesized by a ceramic technique in air (final heating 1350 °C). Composition existence ranges, crystal structure, oxygen nonstoichiometry, electrical conductivity, reduction stability, and compatibility with yttrium stabilized zirconia (YSZ) were investigated. The crystal structures of the compounds were characterized at room temperature as orthorhombic in space group Pbnm. The compounds with (Ca/Ti)>1 are found as p-type, and with (Ca/Ti)<1 as n-type semiconductors. Compositions with x≈y change their conductivity type from n-type at high reducing atmospheres to p-type in less reducing and oxidizing atmospheres. The type and level of the electrical conductivity are functions of ratios of Cr3+/Cr4+ and Ti4+/Ti3+ cations on B-site of ABO3 perovskite-type compounds. No reactivity to YSZ or decomposition up to 1000 °C in 5% H2+95% Ar gas flow were found. No simple correlations between catalytic activity and composition, electrical conductivity, or crystal structure parameters were found.