Mixed oxide ion and proton conduction and p-type semiconduction in BaTi0.98Ca0.02O2.98 ceramics

Ca-doped BaTiO3, BaTi0.98Ca0.02O2.98 is primarily an oxide ion conductor with activation energy 0.77(1) eV when annealed at 700 degrees C and measured in an atmosphere of dry N-2. On exposure of this sample to moisture, proton conduction dominates the conductivity at low temperatures with activation energy 0.42(1) eV but the sample reverts to mainly oxide ion conduction above similar to 500 degrees C as water is lost from the sample. When samples are annealed at 700 degrees C and measured in an atmosphere of dry O-2, p-type semiconduction with activation energy 0.70(2) eV dominates. The nature of the conducting species was determined by a combination of conductivity measurements as a function of oxygen partial pressure and characteristic features in low frequency impedance data.