Study of variation in structural, vibrational and optical properties of Ba doped TiO2, BaxTi(1-x)Oδ

Abstract

A complete phase transition of pure TiO2 from anatase to rutile phase generally occurs at 700C, which has been delayed by Ba doping and this phase transition temperature increases with an increase in Ba concentration. The study of variation in the structure of crystal lattice, such as lattice parameters, crystallite size has been done. During incorporation of Ba in pure TiO2, Ba atoms intercalate the void of TiO2 octahedra and form some extra phases along with the hindrance of phase transition. It also generates some intrinsic lattice strain, which results in peak broadening of the XRD pattern. This intrinsic strain has been calculated using the Williamson and Hall equation. The crystallite size is estimated using Scherrer’s equation. In general, crystallite size increases with temperature and becomes more than 100 nm for pure TiO2, but it remains within a few nanometers for all Ba doping contents. For vibrational analysis, Raman spectroscopy was performed using the HORIBA Jobin Yvon LabRAM HR Evolution with a Helium-Neon laser (=632.8 nm) as the excitation source. By performing UV-Visible spectroscopy, it was observed that the band gap decreases with an increase in temperature for pure TiO2. But as Ba is incorporated, this gap increases and the reason can be obtained from the Brostein-Moss effect in which electrons cloud generated by dopant near conduction band and it requires more energy to excite the electron from the valence band. The UV Visible spectroscopy has been carried out by software called ‘Research India’ with proper apparatus and instrument.