XPS and SEM studies of Ca‐ and Ni‐substituted LaCrO 3 after quenching from reducing and oxidizing atmospheres at 800 °C

Sintered and polished samples of La 1− x Ca x CrO 3 ( x = 0.0, 0.1, 0,3, 0.5) and La 1− x Ca x Cr 1− y Ni y O 3 ( x = 0.3, y = 0.05) were annealed and quenched under reducing or oxidizing conditions at 800 °C and analysed with XPS and SEM. After annealing in H 2 + H 2 O the surfaces of the samples with x = 0.3 and x = 0.5 were enriched in Ca in a 5 nm deep zone. Cr was not enriched and was present in the +3 state. Annealing in O 2 + H 2 O gave Ca enrichment and crystalline outgrowths, increasing with increasing Ca contents. The Cr in the surface was in the +3 and +6 states, and the amount of Cr 6+ increased with increasing Ca contents. These observations are assigned to precipitation of CaCrO 4 and possibly other phases. The Ni‐doped sample exhibited less grain growth during sintering and less surface recrystallization in oxidizing atmospheres than the corresponding sample without Ni.