Nonstoichiometry, thermal expansion and oxygen permeability of SmBaCo2 − xCuxO6 − δ

•Phase relations in pseudobinary SmBaCo2-xCuxO6-δ system were studied•At 0 ≤ x ≤ 1.2, layered perovskites with orthorhombic and tetragonal structure form•Thermal expansion and total conductivity decrease on Cu doping•Doping increases oxygen vacancy concentration and oxygen permeability•Copper additions promote chemical interaction with solid oxide electrolytes

Phase relationship analysis in the pseudobinary SmBaCo2 − xCuxO6 − δ system at 1000–1100 °С in air revealed the existence of solid solutions with the layered perovskite and 123-type structures, formed within the ranges of 0 ≤ x ≤ 1.2 and 1.5 ≤ x ≤ 2.0, respectively. The substitution of Cu2 + for Co3 +/4 + was found to induce phase transition from orthorhombic (space group Pmmm) into tetragonal (P4/mmm) polymorph at x > 0.1, and to increase oxygen deficiency studied by thermogravimetry and iodometric titration. The electrical conductivity and thermal expansion of Cu-substituted cobaltites decrease on doping, while the steady-state oxygen permeability exhibits an opposite trend, in correlation with the oxygen content variations. The average thermal expansion coefficient of SmBaCo1.4Cu0.6O6 − δ ceramics, where the level of ionic transport is comparable to that in most permeable cobaltite-based mixed conductors, is 16.9 × 10− 6 K− 1 at 25–1000 °С in air. At the same time, copper additions increase chemical reactivity of the materials with doped ceria electrolytes.