Phase change and crystal growth of TiO2 in metatitanic acid

Abstract

The transformation of anatase titanium dioxide (TiO2) to its rutile form generally occurs above 600 °C. The anatase to rutile transformation is influenced by the factors such as heating temperature, heating time and the states of particles of anatase TiO2. In the calcination of metatitanic acid, the phase transformation of anatase is a key step to form rutile TiO2 particles with desirable morphological and pigmentary characteristics. However, the precise roles of temperature and time are not clear in the construction of so called calcination intensity for promoting the anatase-rutile transformation to form pigmentary TiO2 from metatitanic acid. Here we show how the temperature and time have affected the anatase to rutile transformation and the crystal growth of metatitanic acid during the calcination. Through thermal analysis, XRD and SEM measurements, we found that the rutilization in metatitanic acid shows a similar growing trend in the most of phase transformation process. However, the trend of the transformation undergoes an abrupt change when rutilization is approaching to its completion. The changes of the morphology of metatitanic acid are related to the coarsening of the particles in the metatitanic acid during the calcination. Our results demonstrate that anatase to rutile transformation and coarsening of particles are affected by the heating temperature and heating time and the growth of TiO2 particles can be controlled through calcination intensity.