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

• (Y,Ca)(Fe,Co)O3−δ was prepared via citrate-based route with annealing at 1150–1200 °C.
• Y0.9Са0.1Fe0.8Co0.2O3−δ demonstrates low thermal expansion coefficient of 11.9 ppm K−1.
• Oxides do not react with YSZ and GDC up to 1000 °C and 1100 °С, respectively.
• Compounds demonstrate higher electrical conductivity in comparison with Y0.9Ca0.1FeO3.
• Pr-doped (Y,Ca)(Fe,Co)O3−δ demonstrate both higher electrical conductivity and TEC.

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 11.9 ppm K−1. High-temperature electrical conductivity measurements revealed almost composition independent conductivity values of 22–27 S/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 50 S/cm (z = 0.3) at 900 °C and dilatometry measured TEC up to 15.1 ppm K−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).

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