Phase equilibria at 1100�C in air and crystal structure of solid solutions in the system LaCoO3?SrCoO2.5??SrNiO3???LaNiO3?

Abstract

Phase equilibria in the LaCoO3—SrCoO2.5—“SrNiO3”—“LaNiO3” system are studied at 1100°C in air using samples prepared by standard solid-state reactions and by the citrate route. The composition region and structure of La1 − xSr x Co1 − yNi y O3 − δ solid solutions are determined by x-ray powder diffraction. The structure is refined by the Rietveld profile analysis method with Fullprof 2002. The solid solutions with 0< x ≤0.5 have a rhombohedrally distorted perovskite structure (sp. gr.R $$ \bar 3 $$ c). The rhombohedral distortion decreases with increasing Sr content, and the solid solutions with x > 0.5 have an ideal cubic structure (sp. gr. Pm3m). The composition dependences of lattice parameters for the La1 − xSr x Co1 − yNi y O3 − δ solid solutions are presented.