The mixed ionic and electronic conductivity of CaZrO3 with cation nonstoichiometry and oxygen partial pressure

The electrical conductivities of Ca1 − xZrO3 − δ (0 ≤ x ≤ 0.10) ceramics were measured as a function of nonstoichiometry (x) and oxygen partial pressure (Po2) using impedance spectroscopy between 700 °C and 1100 °C. The stoichiometric CaZrO3 was a mixed ionic and electronic (hole) conductor in a high Po2 region. It was an ionic conductor in a low Po2 region. The analysis of impedance spectra revealed that the contributions of the grain and the grain boundary to the total conductivity were nearly constant independent of Po2 at 700 °C. In addition, the grain boundary mainly determined the electrical conductivity at 700 °C. When the Ca deficiency (x) increased up to 0.02, the electrical conductivity rapidly decreased with x due mostly to the decrease in the grain boundary conductivity.