Synthesis of highly pure nanocrystalline and mesoporous CaTiO₃ by a particulate sol-gel route at the low temperature

The low temperature perovskite-type calcium titanate (CaTiO₃) thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route. The prepared sol had a narrow particle size distribution about 17 nm. X-ray diffraction and Fourier transform infrared spectroscopy revealed that, the synthesized powders had highly pure and crystallized CaTiO₃ structure with preferable orientation growth along (1 2 1) direction at 400-800 °C. The activation energy of crystal growth was calculated 5.73 kJ/mol. Furthermore, transmission electron microscope images showed that the average crystallite size of the powders annealed at 400 °C was around 3.5 nm. Field emission scanning electron microscope analysis and atomic force microscope images revealed that, the deposited thin films had uniform, mesoporous and nanocrystalline structure with the average grain size in the range 33-39 nm depending on annealing temperature. Based on Brunauer-Emmett-Teller (BET) analysis, the synthesized powders showed mesoporous structure with BET surface area in the range 51-21 m²/g at 400-800 °C. One of the smallest crystallite size and one of the highest surface areas reported in the literature is obtained which can be used in many applications, such as photocatalysts.