Synthesis and characterization of Ga-doped Ba3MoNbO8.5 electrolytes for intermediate temperature-solid oxide fuel cells

Abstract Ba3MoNb1-xGaxO8.5-δ (BMNG, 0 ≤ x ≤ 0.2) powders are successfully prepared by sol-gel autoignition method. The effects of acceptor-type Ga3+ doping on Ba3MoNbO8.5 (BMN) are characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscope, Raman spectroscopy, and electrochemical impedance spectroscopy. All BMNG samples crystallize as a single phase in the R-3m space group and show great phase stability at various environments. Doping a small amount of gallium can effectively improve bulk conductivity and sintering density of BMN. The ionic conductivity of Ba3MoNb0.9Ga0.1O8.5-δ (BMNG10) is the highest, which can reach 2.05 × 10−2 S cm−1 at 800 °C. The enhanced ionic conductivity is primarily related to the increase of oxygen vacancy concentration and the number of tetrahedral units within the structure. In addition, through successfully assembling and evaluating a single cell supported by the BMNG10 electrolyte, it is proved that the practical utilization of BMNG10 in intermediate temperature-solid oxide fuel cells (IT-SOFCs) is feasible. In short, hexagonal perovskite derivative BMNG10 is a promising oxide ion conductor for IT-SOFCs.