Formation of Monodisperse Spherical TiO 2 Powders by Thermal Hydrolysis of Ti(SO 4 ) 2

Titania powders have been prepared by the thermal hydrolysis of titanium sulfate at 80°C in a mixed solvent of n ‐propyl alcohol ( n ‐PrOH) and water. The morphology of the powders was greatly influenced by the volume ratio in n ‐PrOH to water (RH ratio) of the solvent. An RH ratio of 1.0 was essential for the formation of spherical TiO 2 powders. When hydroxypropyl cellulose (HPC) was used as a steric dispersant, monodisperse spherical powders 0.7 (μm in diameter were produced. As the RH ratio was increased, the zeta potential of the powders was negatively increased and the dielectric constant of the solvent was decreased. However, powders obtained at an RH ratio of 1.0 were observed to have the highest energy barrier. The colloidal stability of the powders in a mixed solvent of n ‐PrOH and water is discussed. As‐precipitated powders were amorphous hydrates of titania and were crystallized by calcination into anatase (>600°C) and rutile (>800°C).