Interaction and ordering of lattice defects in oxygen-deficient rutileTiO2−x

Abstract

The atomic and electronic structures of lattice defects in oxygen-deficient rutile ${\mathrm{TiO}}_{2\mathrm{-}\mathit{x}}$ (1×${10}^{\mathrm{-}4}$≲x≲3×${10}^{\mathrm{-}3}$) are discussed on the basis of electron-paramagnetic-resonance measurements. Titanium interstitials with a single paramagnetic electron (S=1/2), which are the main lattice defects for small x (≲3×${10}^{\mathrm{-}4}$), strongly interact with each other for large x (≳4×${10}^{\mathrm{-}4}$) resulting in Ti interstitial pairs with two paramagnetic electrons (S=1) whose Ti-Ti distance and orientation are 3.25 Å and 〈110〉, respectively. At the same time, a considerable fraction of the Ti interstitials are ordered in cooperation with an oxygen deficit, resulting in {121} plane defects. The (121) plane defect contains Ti-ion pairs whose Ti-Ti orientation is 〈100〉, and the Ti-ion pair has two covalent-bond electrons and an additional paramagnetic electron (S=1/2).