Structure of cation interstitial defects in nonstoichiometric rutile

Abstract

New cation interstitial defect models are derived for substoichiometric rutile TiO2-x. These consist of linear arrangements, along [100] or [010], containing two face-shared octahedral pairs of trivalent cations. Diffusion mechanisms are described whereby these may readily aggregate to form pairs of crystallographic shear planes, as observed recently by high-resolution electron microscopy, when TiO2-x specimens are cooled relatively slowly from 1 050 °C. Electrostatic arguments explain why these defects have very much lower formation and migration energies than the traditional « point defect » interstitial model