Preparation of Ultrafine Crystalline TiO2 Powders from Aqueous TiCl4 Solution by Precipitation

Abstract

Ultrafine crystalline TiO₂ powders were prepared by just heating and stirring aqueous TiOCl₂ solution with a Ti⁺⁴ concentration of 0.5 mol/l at room temperature to 100°C under one atmosphere. The crystallinity, the phase transformation and the particle shape of ultrafine TiO₂ powders obtained by this simple precipitation method were analyzed using an X-ray diffractometer (XRD), transmission electron microscopy (TEM), differential thermal analyzer (DTA), and scanning electron microscopy (SEM). TiO₂ crystalline precipitates with a pure rutile phase were formed below 65°C, then TiO₂ crystalline precipitates with an anatase phase started forming at temperatures higher than 65°C, which ends with the pure anatase phase at 100°C. The direct formation of TiO₂ crystalline precipitates from an aqueous TiOCl₂ solution is due to the existence of the OH^- ions in distilled water which cause the crystallization of TiOCl₂ to TiO₂ without hydrolyzation to Ti(OH)₄. Conventionally, rutile-phase TiO₂ is obtained at much higher temperatures. However, in this study a stable rutile-phase TiO₂ was obtained by a simple method at close to room temperature.