Structure and transport in non-stoichiometric β Al2O3

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Abstract
Presents results of a detailed theoretical survey of the defect structure and transport properties of non-stoichiometric beta Al2O3. The authors methods are based on a generalised mott-Littleton approach which includes a full explicit treatment of lattice relaxation around defect species. Their calculations show that the anti-Beevers-Ross site is the stable configuration for excess Na+ ions. These migrate by an interstitialcy mechanism. In grossly nonstoichiometric beta Al2O3, however, the migration mechanism may more closely resemble the vacancy mechanism operative in beta "Al2O3. The authors' results account for the observed differences between the conductivities of the stoichiometric and non-stoichiometric phases. They differ considerably from those of earlier theoretical studies of Wang et al. (1975); this is attributed to improvements in the interatomic potentials and the inclusion of lattice relaxation in the authors study.