Structural Studies During Gelation of WO3 Investigated by In-situ Raman Spectroscopy

In the course of the preparation of WO3 by sol-gel technique we have studied kinetics of its synthesis and the structural changes during gelation. In-situ Raman scattering spectra were obtained for a series of samples during the transition from aqueous solution to gel. The changes in the Raman features were monitored as a function of time during gelation. The removal of water molecules affects the symmetric W=O stretching mode. The Raman spectrum of a gelified sample shows peaks attributed to the O–W–O bending mode and the disappearance of the high-frequency mode attributed to polyanionic species. After two days the gelified sample became a precipitated material, which exhibited the Raman spectrum of a crystalline tungsten oxide hydrate.