Quantitative studies on the size induced anatase to rutile phase transformation in TiO2–SiO2 binary oxides during heat treatments

Abstract

The effect of SiO₂ content on the phase behavior of TiO₂ during heat treatment was investigated in the present study. Sol–gel synthesis was employed to form five different TiO₂–SiO₂ binary oxides. The characterization results confirmed the vital role of SiO₂ in reducing the crystallite growth of TiO₂, which was instrumental in restricting the anatase (a-TiO₂) to rutile (r-TiO₂) phase transformation. It was revealed from the characterization techniques that crystallite size exceeding ∼50 nm induced a-TiO₂ to r-TiO₂ phase transition. Heat treatment beyond 1100 °C resulted in the gradual conversion from a-TiO₂ to r-TiO₂ and moreover the crystallization of cristobalite (c-SiO₂) could not be avoided at 1300 °C. The results from the photoemission spectra ensured a blue shift for the a-TiO₂ stabilized by SiO₂ from the characteristic emissions of pure r-TiO₂. Antibacterial tests also indicated a good response for TiO₂–SiO₂ binary oxides in encountering the microbes.