3.1. Defect Chemistry. Nonstoichiometric oxides, such as
TiO2, may be oxidized or reduced within a single phase leading
to the formation or removal of point defects in the crystal lattice,
such as15,16
1. Oxygen Vacancies: oxygen ion is missing from its lattice
site.
2. Metal Vacancies: metal ion is missing from its lattice site.
3. Metal Interstitials: metal ion is located in an interstitial
site.
4. Electrons: the Ti3+ ions in their lattice sites.
5. Electron Holes: the O- ions in their lattice sites.