The effect of Nb doping upon the formation and diffusion of O vacancies and interstitial Ti in rutile were studied by the use of ab initio density-functional calculations. Calculations showed that the activation energy for the diffusion of O vacancy with Nb doping was higher than that of pure material, due to the suppressive effect of Nb doping upon the formation of O vacancies. In contrast to the effect of Nb doping upon O vacancies, both the formation energy and migration barrier of interstitial Ti increased with Nb doping. The calculated results suggested why Nb doping could improve the oxidation resistance of γ-TiAl.

Ab initio Studies of Nb Doping Effect on the Formation and Diffusion of Oxygen Vacancy and Ti Interstitial in Rutile TiO2. Wang, X., Wang, F.H.: Advanced Materials Research, 2011, 304, 142-7