Effect of solution composition on anatase to rutile transformation of sprayed TiO2 thin films

• The grain sizes of TiO2 thin films could be varied over the range of 20 to 210 nm.
• TTIP and AcacH ratio affects the transformation process from anatase to rutile.
• TiO2 bandgap decreased from 3.45 to 3.02 eV with an increase in annealing temperature.

Acetylacetone is used as a chelating agent for titanium(IV) isopropoxide to inhibit hydrolysis and stabilize the precursor solution. The effect of the molar ratio between titanium(IV) isopropoxide and acetylacetone of 1:1, 1:2, 1:3 and 1:4 in the precursor solution on the morphological, structural and optical properties of TiO2 thin film was investigated. These properties were studied using Fourier transformed infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction and UV–vis spectroscopy as a function of the molar ratios for the as-deposited thin films and films annealed at temperatures of 700, 800 and 950 °C. Mixed anatase and rutile phases were detected after annealing at 800 °C for 1:1 and 1:2 molar ratios and at 700 °C for 1:3 and 1:4 molar ratios. The optical band gap decreased from 3.45 to 3.02 eV with an increase in the annealing temperature in agreement with corresponding structural changes.