Low temperature nanostructured zinc titanate by an aqueous particulate sol-gel route: Optimisation of heat treatment condition based on Zn:Ti molar ratio

Nanocrystalline zinc titanate (ZnTiO₃) thin films and powders with purity of 94% were produced at the low sintering temperature of 500 °C and the short sintering time of 1 h by a straightforward aqueous particulate sol-gel route. The effect of Zn:Ti molar ratio was studied on the crystallisation behaviour of zinc titanates. The prepared sols showed a narrow particle size distribution in the range 17-19 nm. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders contained mixtures of the rhombohedral-ZnTiO₃, cubic-ZnO, cubic-Zn₂TiO₄ phases, as well as the anatase-TiO₂ and the rutile-TiO₂ depending on the sintering temperature and Zn:Ti molar ratio. Moreover, it was found that Zn:Ti molar ratio and sintering temperature influence the preferable orientation growth of the zinc titanate, being on (2 1 1) planes for molar ratios of Zn:Ti = 25:75 and 50:50 and on (1 over(1, ̄) 0) planes for molar ratio of Zn:Ti = 75:25 at sintering temperature of 600 °C. Transmission electron microscope (TEM) images showed that the average crystallite size of the powders annealed at 400 °C was around 2 nm and a gradual increase occurred up to 8 nm by heat treatment at 1000 °C. The activation energy for crystal growth of nanocrystalline ZnTiO₃ calculated in the range 07.86-14.79 kJ/mol. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had mesoporous and nanocrystalline structure with the average grain size of 19-23 nm at 600 °C and 34-39 nm at 800 °C depending upon the Zn:Ti molar ratio.