Titanium vacancies in nonstoichiometric TiO₂ single crystal

Abstract

The semiconducting properties of single‐crystal TiO2 and their changes during prolonged oxidation at elevated temperatures and under controlled oxygen activity were monitored using measurements of electrical conductivity and thermo‐electric power. Two kinetic regimes were revealed: Regime I – rapid oxidation, associated with the transport of oxygen vacancies, and Regime II – prolonged oxidation, which corresponds to the transport of titanium vacancies. The present data represent the first documented evidence for the formation and transport of titanium vacancies in TiO2. This finding allows the processing of p‐type TiO2 without the incorporation of aliovalent foreign ions. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Chemical diffusion in metal oxides. Example of TiO2

“…One should note that, in the temperature range usually used for the characterization of electrical properties (1,000-1,500 K), the concentration of Ti vacancies does not reach equilibrium because the mobility of these defects is too low [5]. The Ti vacancies may reach the equilibrium concentrations at substantially higher temperatures (>2,000 K) [5].…”

“…TiO 2 is a nonstoichiometric compound [4]. It includes defects in both oxygen and cation sublattices, such as oxygen vacancies and Ti interstitials and, recently observed, Ti vacancies [5]. Therefore, the transport mechanism in TiO 2 is rather complicated.…”

Recent developments in TiO2 as n- and p-type transparent semiconductors: synthesis, modification, properties, and energy-related applications

“…The properties of TiO 2 include light absorption, charge transport, and surface adsorption, which are closely related to defect disorder. These properties play a significant role in the utilization of solar energy, the photocatalytic performance, and the electrochemical performance [255][256][257]. The defect disorder of TiO 2 has been considered in terms of oxygen vacancies, titanium interstitials, and titanium vacancies [254].…”

Thermodynamics of oxygen defective Magnéli phases in rutile: A first-principles study

“…[9][10][11][12] Although very rare, titanium vacancies 13 have also been studied. Several experimental [13][14][15][16][17] and theoretical [4][5][6]12 investigations have been performed in order to understand the role that point defects play in determining the physical and chemical properties of TiO 2−x . Results of particular relevance to the current study will be discussed in Secs.…”