Phase Equilibria, Crystal Structure, and Properties of Intermediate Oxides in the Sm2O3–SrO–CoO System

Abstract

The phase equilibria in the 1/2Sm2O3–SrO–CoO system were systematically studied at 1100 °C in air. Single‐phase Sr1–xSmxCoO3–δ and Sr2–ySmyCoO4+δ solid solutions were obtained within the ranges of 0.05 ≤ x ≤ 0.50 and 0.9 ≤ y ≤ 1.3, respectively. XRD patterns of the single‐phase samples were refined by the Rietveld method within the tetragonal structure (space group I4/mmm). Gradual substitution of strontium by samarium leads to a decrease of the unit‐cell parameters and the unit‐cell volume that can be explained by the size factor. An introduction of samarium into strontium cobaltite increases the oxygen content in Sr1–xSmxCoO3–δ. The variation of the electrical conductivity, Seebeck coefficient, and thermal expansion of Sr1–xSmxCoO3–δ and Sr2–ySmyCoO4+δ oxides vs. temperature were measured in air. The chemical reactivity of Sr1–xSmxCoO3–δ and Sr2–ySmyCoO4+δ, in contact with the solid electrolyte materials Ce0.8Sm0.2O2 and Zr0.85Y0.15O2, was examined. The projection of the isothermal–isobaric phase diagram (1100 °C, air) to the compositional triangle 1/2Sm2O3–SrO–CoO has been constructed.