Microstrain and lattice disorder in nanocrystalline titanium dioxide prepared by chemical route and its relation with phase transformation

Abstract

The microstructure of nanocrystalline titanium dioxide (TiO2), synthesized by chemical route, is studied from X-ray peak profile analysis and transmission electron microscopy. The broadening of the X-ray diffraction peaks indicates the presence of small crystallites with a significant amount of disorder. The progression of broadening at lower annealing temperatures, suggests the decrease in the strain broadening. The nano-TiO2 was found to transform partially to rutile phase from its nanocrystalline anatase phase when annealed at a temperature of 750 °C. No further appreciable change was observed after annealing at higher temperature. The lattice parameters of the anatase phase change non-linearly with temperature. It was found that there is a discontinuous change in the value of crystallite size, microstrain and thermal parameter values accompanying with the phase transformation. The microstrain associated with the nanocrystalline grain is closely associated with thermal disorder and oxygen z-displacement. The value of thermal parameter reveals a significant deviation of the Ti atom from the regular lattice sites. The present study reveals that nanocrystalline anatase TiO2 prepared by chemical route shows significant static disorder, which decreases with the increase in the annealing temperature along with concomitant phase transformation.