Single and mixed phase TiO₂ powders prepared by excess hydrolysis of titanium alkoxide

Abstract

To investigate the excess hydrolysis of titanium alkoxides, TiO₂ powders were fabricated from titanium tetraisopropoxide using 6∶1 and 100∶1 H₂O/Ti (r) ratios. The powders were dried and fired at a range of temperatures (⩽800°C). Hydroxylation and organic content in powders were characterised using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR), laser Raman microspectroscopy and elemental microanalysis; surface area and pore size distribution were evaluated using N₂ gas adsorption; phase composition was analysed using X-ray diffraction (XRD) and laser Raman microspectroscopy; and crystallite size was evaluated by XRD, TEM and SEM. Results showed near complete hydrolysis in a predominantly aqueous medium (r = 100), resulting in precipitated crystalline powders exhibiting brookite and anatase, which begin to transform to rutile below 500°C. The powders precipitated in a predominantly organic medium (r = 6) underwent partial hydrolysis, were highly porous and exhibited an amorphous structure, with the crystallisation of anatase occurring at ∼300°C and the transformation to rutile beginning at 500–600°C.

Keywords:

• TiO₂
• Hydrolysis
• Photocatalyst
• Phase transformation