Characterisation of lower temperature sintered zinc-doped barium calcium niobate proton conducting electrolytes

Abstract

The densification of Ba₃Ca_1.18Nb_1.82O_8.73 (BCN18) at 1325 °C has been improved by the addition of ZnO, resulting in the new proton conducting material, Ba₃(Ca_1.18Nb_1.70Zn_0.12)O_8.55 (BCNZ18). As for Ba₃Ca_1.18Nb_1.82O_8.73, Ba₃(Ca_1.18Nb_1.70Zn_0.12)O_8.55 is found to be a mixed conductor; with both electronic and ionic conductivity under different atmospheres. By increasing the sintered density of Ba₃(Ca_1.18Nb_1.70Zn_0.12)O_8.55, the total conductivity has increased by decreasing the grain boundary contribution. Once the sample is hydrated under wet 5% H₂/Ar, Ba₃(Ca_1.18Nb_1.70Zn_0.12)O_8.55 behaves as a pure ionic conductor below 550 °C, due mainly to proton conduction. At 500 °C the value of conductivity measured for Ba₃(Ca_1.18Nb_1.70Zn_0.12)O_8.55 under 5% H₂/Ar was 7.32 × 10⁻⁴ S cm⁻¹. Overall, this material has shown to be a promising electrolyte material for high temperature electrochemical devices.