Sol-gel nanocrystalline brookite-rich titania films

Brookite-rich titanium dioxide films have been prepared for the first time by a sol–gel method by using together diethanolamine (DEA) and polyethylene glycol (PEG) as modulators. The brookite phase was found preponderant only in films heated slowly to 600 °C when some of the crystals grow large enough to form and stabilize this phase. The weight fraction of brookite in the crystalline phase was found by the analysis of XRD data to be around 70%. The presence of an important amount of brookite in the annealed TiO2 coating was also confirmed by the strong feature at 150 cm-1 in the Raman spectrum. The results obtained in this work confirm the strong dependence of the phase stability on the size of the crystallites