STUDY OF DEFECTS IN TiO2 POLYMORPHS USING POSITRON ANNIHILATION

Abstract

This work presents a comparative study of point defects in three TiO2 polymorphs: anatase, rutile, and brookite. Open volume point defects were characterized using the positron annihilation spectroscopy combined with ab initio calculations of positron lifetimes. The TiO2 polymorphs have been investigated in the form of polycrystalline powders and nanopowders. Polycrystalline and nanocrystalline TiO2 powders contain vacancies, vacancy clusters, and nanoscopic pores in which positronium forms. Anatase has the most open structure and exhibits the longest positron lifetimes. In contrast, the shortest positron lifetimes were observed for rutile.