Phase transformation and particle growth in nanocrystalline anatase TiO2 films analyzed by X-ray diffraction and Raman spectroscopy

Nanocrystalline anatase TiO2 films were prepared from colloidal suspensions using particles with a nominal size of 12 nm. Their structure was examined by Raman spectroscopy and X-ray diffraction (XRD). The as-prepared specimens exhibit exclusively features due to the anatase phase of TiO2 (e.g., the E-g, B-1g and A(1g) vibration modes in Raman spectroscopy and the characteristic diffraction peaks in XRD). Isochronal annealing of the films in air at temperatures of up to 1320 K effected clear structural changes, observed both in Raman and XRD: the crystallite size increases from similar to 13 nm to similar to 125 nm between 470 K and 1220 K, with the crystallites remaining in the anatase phase. A phase transition to the rutile phase of TiO2 occurs gradually in the temperature range 1220-1320 K and the average crystallite size increases to similar to 160 nm. (C) 2007 Published by Elsevier B.V.