Sol–gel alumina coating on quartz substrate for environmental protection

Transparent γ-Al 2 O 3 thin film can be utilized as an absorbent or protective layer in environmental protection. The aim of the present research work is to improve the structural and optical properties of γ-Al 2 O 3 thin film. Al 2 O 3 thin films were synthesized by various newly developed routes based on colloidal technique and sol–gel chemistry. Many types of starting materials (Al acetate, nitrate, isopropoxide, boehmite, and Al 2 O 3 powders) and additives (acetic acid, HCl, HNO 3 , citric acid) were used in the experiments. Suspension and gel-like precursor systems were compared for layer creation. The layers were characterized by their morphology (GIXRD), surface and thickness (SEM), as well as transparency (UV–visible spectroscopy). The best quality of layer (∼90% transmittance, 50–60 nm thickness, perfect covering) has been obtained by sol–gel technique starting from Al nitrate or Al acetate.