Raman Study on Sol-Gel Derived Tungsten Oxides from Tungsten Ethoxide

Tungsten oxide gels were prepared by a sol-gel process from a tungsten ethoxide/ethanol/water solution (sol). Tungstic hydrates were observed in high-viscosity sol by Raman spectroscopy. As the sol is reduced to the gel, Raman bands ascribed to amorphous tungsten oxide appeared. The result of the Raman measurement shows that the structure of the gel changes progressively during heat treatment and that the amorphous tungsten oxide becomes a crystalline solid at 410°C.