Electrical Conductivity, Defect Equilibrium and Oxygen Vacancy Diffusion Coefficient of La1 − x Ca x AlO3 − δ Single Crystals

Abstract

In order to make clear the ionic and electronic conductivities of the perovskite‐type , single‐crystalline samples with were prepared by a floating zone technique. The conductivity and the oxygen nonstoichiometry were measured by a dc four probe method and by a high temperature gravimetry, respectively, both as a function of oxygen partial pressure, , between 1 and 10−20 atm and temperatures up to 1100°C. It was found that the nonstoichiometric change in the oxygen content with and temperature was smaller than the experimental errors of . The results were analyzed by a simple defect model assuming and as predominant defects and electron holes as minor defects. The conductivity due to electron holes, , and due to oxygen vacancy, , at temperatures between 700 and 1000°C are found to be expressed by the equations: and . The oxygen vacancy diffusion coefficient, , was calculated as .