The Temperature and Oxygen Pressure Dependence of the Ionic Transference Number of Nonstoichiometric CeO2 − x

Abstract

An electrochemical cell technique was used to measure the ionic transference number of sintered specimens of nonstoichiometric as a function of temperature (590°–1000°C) and oxygen partial pressure (1–10−22 atm). The results were described in terms of a high and low oxygen pressure region. The ionic transference number is controlled by impurities in the high oxygen pressure region. In this region the electronic conductivity was p‐type at lower temperature and n‐type at higher temperatures. In the low oxygen pressure region the ionic transference number is small (e.g., ). The electrical conduction in this region is controlled by the nonstoichiometric defects and is predominantly electronic. Using the value of , an estimate of the diffusion coefficient for doubly ionized oxygen vacancies, was calculated by combining recently obtained thermodynamic and conductivity data with the Nernst‐Einstein relation.