The microscopic mechanism leading to stabilization of cubic and tetragonal
forms of zirconia (ZrO2β) is analyzed by means of a self-consistent
tight-binding model. Using this model, energies and structures of zirconia
containing different vacancy concentrations are calculated, equivalent in
concentration to the charge compensating vacancies associated with dissolved
yttria (Y2βO3β) in the tetragonal and cubic phase fields (3.2 and 14.4% mol
respectively). The model is shown to predict the large relaxations around an
oxygen vacancy, and the clustering of vacancies along the directions,
in good agreement with experiments and first principles calculations. The
vacancies alone are shown to explain the stabilization of cubic zirconia, and
the mechanism is analyzed.Comment: 19 pages, 6 figures. To be published in J. Am. Ceram. So