Studies on ionic conductivity of dense 6 mol% Sc3+-doped SnP2O7–SnO2 composite ceramic at intermediate temperatures

A dense 6 mol% Sc3+-doped SnP2O7–SnO2 composite ceramic was prepared by low-temperature sintering (at 600 °C). The XRD result confirmed that an SnP2O7 phase grows on the internal surface of the SnO2 substrate. The SEM result showed that the composite ceramic was sufficiently dense. The highest conductivities were observed to be 2.9×10−2 S cm−1 in wet air atmosphere and 5.0×10−2 S cm−1 in wet H2 atmosphere at 325 °C. The lg σ–lg(pO2) plot result indicated that the composite ceramic was almost a pure ionic conductor under high oxygen partial pressure and the protonic conduction became dominant under low oxygen partial pressure.