The effect of cation nonstoichiometry on the electrical conductivity of CaZrO3

The electrical conductivities of Ca1−xZrO3−δ systems were measured by using impedance spectroscopy as a function of Ca/Zr ratio (0 ≤ x ≤ 0.1) and temperature (550–1100 °C). Stoichiometric CaZrO3 revealed poor sinterability due possibly to the free CaO observed at grain junctions. With decreasing Ca/Zr ratio, the free CaO disappeared and the sintered density increased. The total electrical conductivity rapidly decreased, ∼100 times at 1100 °C, when the Ca content decreased below 0.98. The impedance measurement revealed that the decrease is due mostly to the increase in the grain boundary resistivity. The activation energy of grain boundary resistivity also rapidly increased with decreasing Ca/Zr ratio. In other words, the grain boundary resistivity was very sensitive to Ca/Zr ratio.