Mixed oxide ion and proton conduction and p-type semiconduction in BaTi_(0.98)Ca_(0.02)O_(2.98) ceramics

摘要

Ca-doped BaTiO3, BaTi_(0.98)Ca_(0.02)O_(2.98) is primarily an oxide ion conductor with activation energy 0.77(1) eV when annealed at 700 °C and measured in an atmosphere of dry N2. 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 ~500 °C as water is lost from the sample. When samples are annealed at 700 °C and measured in an atmosphere of dry O2, 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.