Proton conductivity and microstructures of the core-shell type solid electrolytes in the MO2-In2O3-P2O5 (MTi, Sn, Zr) systems

The proton conducting 0.9MO2·0.05In2O3·1.3P2O5 (MTi, Sn, Zr) electrolytes based on a core-shell structure were synthesized by a ball milling method. The core-shell type electrolytes showed the proton conductivities ranging from a higher value than those of Nafion membranes to 10− 5 Scm− 1 at intermediate temperatures of 150–200 °C, depending on the heat-treatment conditions. The samples with high conductivity were proved to adopt a core-shell structure by SEM observation, powder XRD analysis and 31P MAS-NMR measurements.