Grain Growth and Phase Transformation of Titanium Oxide During Calcination

Additions of NiO, CoO, MnO 2 , Fe 2 O 3 , and CuO promote the anatase‐rutile transformation and grain growth of TiO 2 . Additions of Na 2 O and WO 3 retard the transformation and have no effect on the grain growth. The addition of MoO 3 strongly promotes the grain growth but has only a slight effect on the phase transformation. Both the grain growth and transformation are promoted slightly by Cr 2 O 3 . The transformation is significantly affected by the method of preparing TiO 2 . The grain size of TiO 2 heated in H 2 exceeds that of TiO 2 heated in O 2 , in air, in argon, and in vacuum. The rate of transformation decreases with an increase in the partial pressure of oxygen of the atmosphere.