An investigation on the microstructural and electrical properties of La0.85DxSr0.15-xGa0.8Mg0.2O2.825 (D = Ba and Ca) electrolytes in solid oxide fuel cells

La0.85DxSr0.15-xGa0.8Mg0.2O2.825 (D = Ba and Ca, x = 0, 0.01, 0.03, 0.05, and 0.07) electrolytes were synthesized using a solid-state reaction method, calcined at 1400 °C for 5 h, and sintered at 1400 °C for 5 h. The microstructures, electrical properties, and cell performances of the electrolytes and fuel cells were analyzed by X-ray diffraction, scanning electron microscopy, impedance analysis, and electrochemical analysis. La0.85BaxSr0.15-xGa0.8Mg0.2O2.825 (LBSGM) and La0.85CaxSr0.15-xGa0.8Mg0.2O2.825 (LCSGM) exhibit a dense structure and a cubic perovskite phase. Further, they contain small amounts of a secondary phase. The lattice constants of LBSGM and LCSGM are 0.3913-0.3914 nm and 0.3906-0.3909 nm, respectively. The average grain size of the sample increases with increasing Ba2+ or Ca2+ content. The conductivity of LCSGM (0.197-0.174 S/cm) is usually higher than that of LBSGM (0.181-0.162 S/cm) at 800 °C. The cells with La0.85Sr0.15Ga0.8Mg0.2O2.825 and La0.85Ca0.03Sr0.12Ga0.8Mg0.2O2.825 electrolytes exhibit high open-circuit voltages and maximum power densities of 0.96 V and 542 mW/cm2 and 0.94 V and 567 mW/cm2, respectively, at 800 °C.