Dilute Ga Dopant in TiO2 by X-ray Absorption Near-Edge Structure

As a model of aliovalent impurity in functional ceramic, the local environment of dilute Ga in rutile-structured TiO2 is investigated by Ga K-edge X-ray absorption near-edge structure (XANES) spectroscopy. In conjunction with the experiments, first-principles calculations by two methods are systematically made. The projector augmented wave method is used to optimize the local structure and obtain the solution energy. The augmented plane wave plus local orbitals method is adopted to obtain theoretical XANES spectra. A comparison between experimental and theoretical XANES spectra shows that Ga dopants are located at the Ti4+ sites forming Ga3+. Oxygen vacancies are present to maintain the charge balance of the solid solution. Ga atoms and oxygen vacancies are not present at the nearest neighbor sites but stay apart.