Phase equilibria and crystal structures of solid solutions in the system LaCoO3−δ-SrCoO2.5±δ-SrFeO3−δ-LaFeO3−δ

The composition region and structure of La1−xSrxCo1−yFeyO3−δ solid solutions are determined by x-ray powder diffraction using the Rietveld profile analysis method. The solid solutions based on lanthanum cobaltite, LaCoO3−δ, have a rhombohedrally distorted perovskite-like structure (sp. gr. R\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\bar 3$$ \end{document}c), and those based on lanthanum ferrite, LaFeO3−δ, have an orthorhombically distorted structure (sp. gr. Pbnm). The rhombohedral distortion decreases with increasing strontium 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−xSrxCo1−yFeyO3−δ solid solutions are presented, and the 1100°C isotherm of the LaCoO3−δ-SrCoO2.5±δ-SrFeO3−δ-LaFeO3−δ system in air is constructed.