Investigation on the Effect of Preparation Techniques of Anatase on its Structural and Optical Properties

The structural transformations of anatase-TiO2 (a-TiO2) nanopowders have been explored upon its synthesis via different routes. Mechanically-induced synthesis was conducting by subjecting vibratory ball milling on microscale... [ view full abstract ]

The structural transformations of anatase-TiO₂ (a-TiO₂) nanopowders have been explored upon its synthesis via different routes. Mechanically-induced synthesis was conducting by subjecting vibratory ball milling on microscale a-TiO₂ for different time intervals at ambient temperature. On the other hand, nano-scale a-TiO₂ was prepared by sol-gel method via the hydrolysis of titanium tetrachloride (TiCl₄) followed by ball milling.   

The synthesized nano-powders were characterized by XRD, SEM, HR-TEM and UV-vis reflectance spectroscopy. Band gap was calculated by applying Kubelka-Munk equation on the UV-visible diffuse reflectance spectra.

This study showed that the mechanical ball milling stimulates TiO₂ (Fig. 1) to undergo phase transformations from a-TiO₂ (tetragonal) to srilankite (s-TiO₂-orthorhombic) then to rutile (r-TiO₂-tetragonal). Within 0.5 hrs of milling, s-TiO₂ peak evolved in the bulk powder then completely transformed to rutile after 6 hrs. On the other hand, TiO₂ nanoparticles (Fig. 2), which were prepared via sol-gel method followed by mechanical treatment, had shown to be more resistance towards phase transformation. The phase transformation was slower. It took 9 hrs of milling to completely transform into rutile phase. Both synthesized nano powders experienced a shift in band gap towards visible region by 0.28 and 0.23 eV, respectively after 9 hrs of milling.