Coprecipitation Synthesis and Characterization of La_0.8Sr_0.2Ga_0.8−x Mg_0.2Co _x O_2.8 for Intermediate Temperature Solid Oxide Fuel Cell Electrolytes

La_0.8Sr_0.2Ga_0.8−x Mg_0.2Co _x O_2.8 (LSGMC) electrolyte powders containing different amount of Co (0 ≤ x ≤ 0.15) were prepared by ammonium carbonate coprecipitation method. The precursors, the calcined powders, and the sintered pellets were characterized by thermogravimetry/differential thermal analysis, X-ray diffractometry, scanning electron microscopy, and an impedance analyzer. The thermal decomposition of the LSGMC precursors was completed at around 900 °C with the total weight loss of approximately 35%. The LSGMC samples sintered at 1350 °C consisted of the pure perovskite structure. The ionic conductivity was significantly improved by Co doping for the Ga-site of the La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 (LSGM) electrolytes. The ionic conductivity of LSGMC (x = 0.1) exhibited the highest values of 1.6 × 10⁻¹ S cm⁻¹ at 700 °C with an activation energy for the oxide-ion conduction of 0.29 eV. The results of this study indicated that the Co-doped LSGM electrolytes had excellent properties for use as an electrolyte in an IT-SOFC and the ammonium carbonate coprecipitation process could be employed as the efficient method for the preparation of the Co-doped LSGM electrolytes.