Effect of Hydrothermal Treatment of Amorphous Titania on the Phase Change from Anatase to Rutile during Calcination

Hydrothermal treatment of amorphous titania has been used to crystallize and stabilize the anatase phase of titania. The hydrothermal treatment conditions can be used to control the physical properties of the crystallized anatase powder, which in turn control the subsequent phase-change properties of the anatase/rutile phase change. The synthesis history of the amorphous starting material is crucial in determining the final phase-change characteristics. The presence of a small amount of brookite phase contamination in the anatase, results in rapid conversion to rutile. Crystallite size also plays an important role in determining the anatase stability, with increasing crystallite size resulting in higher stability, but the phase-change temperature was shown to have only a weak dependence on surface area.