Crystal structure, oxygen nonstoichiometry and thermal expansion of the layered NdBaCo2−xМxO5+δ (M = Ni, Cu)

Abstract

The homogeneity range and crystal structure of the NdBaCo2−xMxO5+δ (0.0⩽x⩽0.5 for M=Ni and 0.0⩽x⩽1.1 for M=Cu) solid solutions were determined by X-ray diffraction. The crystal structure of the NdBaCo2−xMxO5+δ was described as tetragonal (sp. gr. P4/mmm). The structural parameters were refined using Rietveld full-profile analysis. It was shown that parameter a remains practically constant while parameter c gradually increases with the increase of nickel or copper content. The changes of oxygen content in NdBaCo2−xMxO5+δ versus temperature were determined by thermogravimetric analysis. Gradual substitution of cobalt by copper or nickel leads to the decrease of oxygen content. The average thermal expansion coefficients for the NdBaCo2−xMxO5+δ (M=Ni, Cu) samples were calculated within the temperature range 298–1273K in air. The chemical stability of complex oxides NdBaCo2−xMxO5+δ (M=Ni, Cu) in contact with the electrolyte materials Ce0.8Sm0.2O2−δ and Zr0.85Y0.15O2−δ were investigated within the temperature range 1173–1373K in air.