Synthesis and characterization of vanadium oxide-silicon oxide composite coatings by sol-gel techniqe

Vanadium oxide has been widely studied due to its ability to undergo a reversible semiconductor to metal transition which gives the material its unique chromic and photocatalytic properties. Vanadium oxide is also known for its various applications in glass coating technologies, semiconductor industry, in batteries and as supercapacitors, catalysis, and optical switching devices. On the other hand, SiO2 coatings have unique properties such as adjustable refractive index, controllable microstructure, and good transmittance in the visible region; therefore they are used in many application areas such as microelectronics, optoelectronics, sensors, photo-catalysis, self-cleaning and solar energy technologies. In this study, a composite sol of vanadium oxide-silicon dioxide was prepared by using metal alkoxides as precursor, namely vanadium (V) oxytriisopropoxide for vanadium oxide and TEOS (tetraethyl orthosilicate) for silicon dioxide and V2O5-SiO2 coatings were successfully deposited on glass substrates by sol-gel dip coating technique. Microstructural analyses by SEM demonstrated the nanostructure of V2O5-SiO2 coatings deposited. XRD analyses revealed that the coating is amorphous at 300 °C and V2O5 phase obtained at 400 and 500 °C demonstrating that coatings are nanocomposites with crystalline V2O5 phase in the amorphous SiO2 matrix. Optical analyses showed that the transparency of the coatings increased with the increase in the annealing temperatures and the highest transparency of about 70% was obtained from the coating annealed at 500 °C.