It was noted that ionic conduction and O diffusion in Y2O3-doped zirconia were due to the mobility of O vacancies. Vacancy association reactions with Y cations could be classified by using the activation enthalpies (ΔH), determined by various methods, as a function of the yttria content (3 to 24mol%). The ΔHO value for O tracer diffusion was independent of the yttria content (average value: 0.95eV). The activation enthalpy for electrical conductivity, ΔHDC, rose from 1.05 to 1.5eV with increasing Y2O3 content; indicating growing association effects. Slightly higher activation enthalpies were found in dielectric loss experiments. In internal friction experiments, localized jumps of vacancies bound to Y ions could be observed as Debye loss peaks. Here, the activation enthalpy increased, with increasing Y2O3 content, from 0.9 to 1.6eV. The results were explained in terms of the combined effects of migration, association and interaction of O vacancies and stabilizer cations.

Oxygen Mobility in Yttria-Doped Zirconia Studied by Internal Friction, Electrical Conductivity and Tracer Diffusion Experiments. M.Weller, R.Herzog, M.Kilo, G.Borchardt, S.Weber, S.Scherrer: Solid State Ionics, 2004, 175[1-4], 409-13