Ab initio studies of Nb doping effect on the formation of oxygen vacancy in rutile TiO2 Original Research Article

In this paper, the effect of Nb doping on the formation of O vacancies in rutile TiO2 is studied by the use of ab initio density-functional calculations. The formation energies are calculated at different doping concentrations (C Nb) and the corresponding electronic structures are analyzed. It is shown that the formation energy is mainly determined by the structural relaxation. As C Nb increases, the formation energy first increases and then decreases with the maximum in vicinity of C Nb=11.1 at%. The investigation of electronic structures shows that the distribution of excess electrons, which is affected by the doping concentration and the types of oxygen vacancy, determines the relaxation and formation energy of oxygen vacancy. Our calculated results indicate that the formation of oxygen vacancy in rutile TiO2 can be most effectively suppressed by Nb doping in a large range of Nb doping concentration. This may be one of the reasons why the proper amount of Nb doping can improve the oxidation resistance of γ-TiAl