Physicochemical properties of proton-conductive Ba(Zr_0.1Ce_0.7Y_0.1Yb_0.1)O_3−δ solid electrolyte in terms of electrochemical performance of solid oxide fuel cells

Previously, most studies of proton-conductive electrolytes for SOFCs were conducted to achieve lower-temperature operation. In this study, we investigate a proton-conductive electrolyte to realize high-efficiency SOFCs. To this end, the dependencies of the total conductivity of Ba(Zr_0.1Ce_0.7Y_0.1Yb_0.1)O_3−δ on the oxygen partial pressure and temperature under wet and dry conditions were measured. Based on the measurement data, we analyzed the ratio of ionic current density to electronic current density in the temperature range of 550–900 °C. Assuming that the area-specific resistance of the electrolyte and the external current density were 0.383 Ω cm² and 0.25 A cm⁻², respectively, the leakage current densities caused by the minority carriers were calculated to be 5.4% and 9.7% of the external current density at 550 °C and 600 °C, respectively. This study developed a method to evaluate proton-conductive electrolyte materials and established guidelines for the development of new materials for high-efficiency SOFCs.