Abstract

Crystallographic structures of TiO2 (brookite, anatase and rutile) are obtained by the Sol-Gel Method. The polymorphic transition of thermodynamically unstable tetragonal anatase to stable tetragonal rutile phase is monotropic, although the degree of transformation depends on time and temperature of calcination, method of material preparation, particle size distribution, presence of impurities, etc. In this work were synthesized TiO2 nanocrystals by the Sol-Gel method, these materials were annealed at 200 and 500°C and characterized by XRD (X-Ray diffraction)-Rietveld refinements, nitrogen adsorption (BET) and Transmission Electron Microscopy (TEM). Important differences were observed as a function of the annealing treatments of the samples. As for the low- temperature-treated samples (200 °C), nanocrystal with small particle sizes (7 nm) and high abundance of anatase, coexisting with the anatase and brookite phase, were obtained. Meanwhile, the sample annealed at 500°C, showed one particle size increased (22 nm) and an important polymorphic increased. According to the results, the sample that showed high activity in the photocatalytic decomposition of acetaldehyde was annealed at 200ºC (TiO2-P-200).