Stabilization of the anatase phase in TiO2(Fe3+, PEG) nanostructured coatings

Multilayered TiO2(Fe3+, PEG) films were deposited on glass and SiO2/glass substrates by sol-gel dipping method. The influence of Fe3+ and PEG(polyethylene glycol) concentrations, the number of layers, the thermal treatment time and the temperature on the optical and microstructural properties of the TiO2 films were studied.As-deposited TiO2(Fe3+, PEG) films were very porous, but after the thermal treatment at 500 °C, the PEG decomposed and burned out to porosity decreasing. Homogeneous nanostructured films were obtained, where the amorphous and the anatase phases coexist. XRD analysis showed that no rutile phase is observed in the films deposited on SiO2/glass as compared with those deposited directly on glass and that the presence of the anatase phase in the films without PEG is more evident in the three-layers film. The XRD intensity of the main peak of anatase from 25° decreases with the increase of PEG concentration.The optical gap of the TiO2(Fe3+, PEG) films is found in 2.52-2.56 eV range and does not essentially depend on the PEG content.