Properties characterization of tungsten doped strontium ferrites as cathode materials for intermediate temperature solid oxide fuel cells

Cobalt-free SrFe1-xWxO3-δ (SFW, x = 0, 0.1, 0.2, 0.3) perovskite cathode materials were synthesized by the citrate-EDTA-nitrate combustion method and systematically characterized in terms of their phase structure, thermal sintering and expansion behavior, conductivity and catalytic activity on oxygen reduction reaction (ORR). All SFW powders exhibit cubic perovskite structure and the good chemical compatibility between SFW cathode and Ce0.8Sm0.2O2-δ (SDC) electrolyte is found. Introduction of W clearly inhibits the loss of lattice oxygen in temperature range of 400-900 °C and decreases the thermal expansion coefficients. As the W-doping concentration increases, the thermal sinterabilty weakens with decreasing grain size, and the conductivity decreases from 118.2 to 6.1 S cm−1 at 600 °C. Among of SrFe1-xWxO3-δ-SDC composite cathodes, the SrFe0.8W0.2O3-δ-SDC cathode shows the smallest area specific resistance (ASR) value and the best ORR catalytic activity in range of 500-800 °C. The anode-supported single cell based on SDC electrolyte and SrFe0.8W0.2O3-δ-SDC composite cathode generates high power density and low polarization resistance. At 700 °C, the peak density and polarization resistance are 694 mW cm−2 and 0.036 Ω cm2, respectively.