Electrical conduction of dense Ga3+-doped SnP2O7–SnO2 composite ceramic at intermediate temperatures

A dense Ga3+-doped SnP2O7–SnO2 composite ceramic (9 mol% Ga3+) was prepared by reacting a porous 9 mol% Ga3+-doped SnO2 substrate with an 85% H3PO4 solution at 600 °C. The XRD result confirmed that an SnP2O7 phase grows on the internal surface of the SnO2 substrate. The highest conductivity was observed in dry air atmosphere at 350 °C to be 2.26×10−2 S cm−1 and in wet air atmosphere at 275 °C to be 3.79×10−2 S cm−1,. The lg σ ~lg (pO2pO2) plot result indicated that the composite ceramic was almost a pure ionic conductor under high oxygen partial pressure and a mixed conductor of ion and electron under low oxygen partial pressure.