Characterization of brookite and a new corundum-like titania phase synthesized under hydrothermal conditions

摘要

Brookite rich samples were synthesized under hydrothermal conditions by using TiCl3 as precursor. They also contained a new titanium oxide phase that has the same crystalline structure as Ti2O3, and is stable after annealing in air. Samples were characterized with X-ray powder diffraction, transmission electron microscopy and thermogravimetry. Crystalline phases were refined by using the Rietveld method, from which phase concentrations and atomic bond lengths were obtained as a function of sample annealing temperature. Samples contained brookite, anatase, rutile and the new corundum-like phase: Brookite's concentration was larger than 50 wt%, while the one of the corundum-like phase reached 20(6) wt%. The local symmetry and the atomic bond lengths of these two phases depended on the crystallite size; for both, there is a correlation between the evolution of the atomic bond lengths with temperature and their transformation into another phase. The hydrothermal conditions stabilized brookite, anatase, and the corundum-like phase at high temperature: This last phase was stable in air, even at 900degreesC. (C) 2004 Elsevier Inc. All rights reserved.