Raman microprobe study of nanophase TiO₂ and oxidation-induced spectral changes

A Raman microprobe study of as-compacted nanophase TiO₂ was carried out to investigate the spatial inhomogeneity of its anatase and rutile phases. Also, changes in the observed Raman spectra (line shifts and broadening) were investigated as a function of annealing at temperatures up to 600°C in argon or air. Microscopic phase inhomogeneity is observed and Raman spectral changes are shown to result from inhomogeneous oxygen deficiency in the nanophase TiO₂. The line positions corresponding to the Raman active E_g modes in both anatase and rutile are found to be sensitive to this oxygen deficiency and are potential quantitative indicators of such deviations from stoichiometry.