The Electrical Conductivity of CaO-Doped Nonstoichiometric Cerium Dioxide from 700° to 1500°C

Abstract

The electrical conductivity of sintered specimens of was measured over the temperature range 700°–1500°C and from 1 to 10⁻²² atm of oxygen. All specimens of exhibited mixed conduction. Two limiting case regions were observed. At low temperatures and high oxygen pressures, the conductivity is predominantly ionic. In this region the conductivity is independent of and between approximately 1 and 8 m/o is proportional to mole per cent . The following equation for ionic conductivity was obtained by fitting the conductivity data in this region to an expression derived on the basis of an oxygen vacancy model. An approximate expression for the diffusion coefficient for oxygen vacancies was calculated from the above expression and the Nernst‐Einstein relation. At high temperatures and low oxygen partial pressures and for lower contents the conductivity is predominantly electronic. In this region the magnitude and dependence of σ is similar to “pure” . A thermodynamic argument is also presented which favors oxygen vacancies as the nonstoichiometric defect in both pure and .