Oxygen mobility in yttria-doped zirconia studied by internal friction, electrical conductivity and tracer diffusion experiments

Ionic conduction and oxygen diffusion in Y2O3-doped zirconia are due to the mobility of oxygen vacancies. Vacancy association reactions with Y cations can be classified using the activation enthalpies ΔH determined by various methods in dependence of the yttria content (3–24 mol%). ΔHO for oxygen tracer diffusion is independent of the yttria content (average value ΔHO=0.95 eV). The activation enthalpy of electrical conductivity, ΔHDC, rises from 1.05 to 1.5 eV, with increasing Y2O3 content, pointing to growing association effects. In dielectric loss experiments, slightly higher activation enthalpies were found. In internal friction experiments, localized jumps of vacancies bound to yttrium ions can be observed as Debye loss peaks. Here, the activation enthalpy ΔHML rises with increasing Y2O3 content from 0.9 to 1.6 eV. The results are discussed with respect to the combined effect of migration, association and interaction of oxygen vacancies and stabilizer cations.