Synthesis, thermal expansion and high-temperature electrical conductivity of Co-doped (Y,Са)FeO3−δ with orthorhombic perovskite structure

Abstract

Orthorhombic perovskites Y1−xСаxFe1−yCoyO3−δ (0.1≤х≤0.2, 0.1≤y≤0.2 and х=0.1, y=0.3) were synthesized in air by the citrate route at 1150–1300°C. High-temperature X-ray powder diffraction (HT XRPD) data for Y0.9Са0.1Fe0.8Co0.2O3−δ at 25–800°C showed no phase transition with calculated thermal expansion coefficient (TEC) of 11.9ppmK−1. High-temperature electrical conductivity measurements revealed almost composition independent conductivity values of 22–27S/cm at 900°C. No chemical interaction of Y0.8Са0.2Fe0.9Co0.1O3−δ with (Zr,Y)O2−x (YSZ) or (Ce,Gd)O2−x (GDC) was observed up to 1000°C and 1100°С, respectively. Partial replacement of Y by Pr according to formula Y0.8−zPrzCa0.2Fe0.7Co0.3O3−δ, 0.1≤z≤0.35, leads to an increase of both electrical conductivity up to 50S/cm (z=0.3) at 900°C and dilatometry measured TEC up to 15.1ppmK−1. Moderate values of electrical conductivity in combination with low TEC and stability towards chemical interaction with typical SOFC electrolytes make Co-doped Y1−xCaxFeO3−δ promissing cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC).