A study of oxygen ion conductivity in doped non-stoichiometric oxides

In doped non-stoichiometric oxides that show oxygen ion conductivity, association commonly takes place between the dopant cations and the compensating oxygen vacancies. The activation energy thus comprises two parts, a migration enthalpy and an association enthalpy. We have determined the effects of structure and host cation type on the migration enthalpies, and the effect of dopant cation size on the association enthalpies. This we did by a variety of methods including theoretical calculations and experiment. We have further reviewed the literature in order to verify our calculations and we conclude that size terms in the association enthalpies are the most important factor in the determination of the magnitude of oxygen ion conduction.