Structural and optical properties of ZnO/TiO2 composites

Abstract

This work investigates the structural and optical properties of mixed ZnO/TiO2 ceramics synthesized at 900 °C by the conventional solid state sintering method. We doped different weights of TiO2 powder (x = 1–7 wt%) to prepare the ceramic pellets. Then we studied the effect of TiO2 content on crystalline properties, grain size and residual stress using X-ray diffraction. XRD patterns revealed the alloying of hexagonal ZnTiO3 and spinel Zn2TiO4 phases as the doping rate x (wt%) increased. The growth of ZnO grains in wurtzite structure was favored along the (100) direction with coefficient texture 2.27 for a TiO2 amount x = 1wt%. Grain sizes were obtained in the range 33–73 nm. We used Williamson-Hall (W–H) analysis and size–strain plot (SSP) method to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the ZnO/TiO2 composites. Strain, stress and energy density values were calculated by assuming a uniform deformation model (UDM). We investigated the optical properties of the ceramics by Absorbance and Reflectance measurements at room temperature in the wavelength range 200–1000 nm. The results suggested that the addition of TiO2 to ZnO powder led to a high transparency in the visible range and two absorption edges in the UV region. Interestingly, it was seen slight enhancement of the band gap from 3.1 eV to 3.18 eV for the first edge while the second one was enhanced from 4.8 eV to 5.05 eV as the TiO2 doping concentration increased from 1 wt% to 7 wt% respectively.