Influence of Sol-Gel pH and Soaking Time on the Morphology, Phases and Grain Size of TiO_2 Coating

摘要

Titanium oxide, (TiO_2), can exist in three distinct crystallographic phases known as anatase, rutile, and brookite. Brookite, however, is the least known TiO_2 phases and usually exists as byproduct during synthesising rutile or anatase. Therefore, in this study, the influence of sol-gel pH and soaking time on surface morphology, phases and grain size of TiO_2 coating were investigated in an attempt to develop brookite thin film. Titanium (IV) isopropoxide (TTiP) is used as precursor for preparing TiO_2 sols. Prior to heating, TiO_2 layers were deposited on a glass slide by dipping it five times into TiO_2 sols. The TiO_2 layers were then heated at 450℃ and soaked for 1 and 3 hours to form TiO_2 coating. Analysis on the phases and grain size were carried out using X-ray diffraction (XRD). The TiO_2 surface morphology was investigated using Scanning Electron Microscope (SEM). Results showed that brookite phase with grain size of 27.40 nm were successfully deposited on glass slide from sols with pH12. Conversely, the TiO_2 coatings deposited from sols of pH~1 and pH~7 are amorphous. The effect of soaking time on phases and grain size is insignificant but enhances coatings uniformity as the soaking time increased. Thus, it can be concluded that sol-gel pH affects TiO_2 crystallinity and phases. Brookite film is develop only when the TiO_2 sols is in bases condition or at higher pH value.