Preparation of TiO2 thin films from autoclaved sol containing needle-like anatase crystals

A new inorganic sol-gel method was introduced in this paper to prepare TiO2 thin films. The autoclaved sol with needle-like anatase crystals was synthesized using titanyl sulfate (TiOSO4) and peroxide (H2O2) as starting materials. The transparent anatase TiO2 thin films were prepared on glass slides from the autoclaved sol by sol-gel dip-coating method. A wide range of techniques such as Fourier transform infrared transmission spectra (FT-IR), X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), scanning electron microscopes, X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrum were applied to characterize the autoclaved sol and TiO2 thin films. The results indicate that the autoclaved sol is flavescent, semitransparent and stable at room temperature. The anatase crystals of TiO2 films connect together to form net-like structure after calcined and the films become uniform with increasing heating temperature. The surface of the TiO2 films contain not only Ti and O elements, but also a small amount of N and Na elements diffused from substrates during heat treatment. The TiO2 films are transparent and their maximal light transmittances exceed 80% under visible light region.