Quantitative Characterization of Raman Spectra of Vanadium Oxides Layered on SiO2

Abstract

The Raman spectra of vanadium oxides layered on Aerosil have been quantitatively investigated. First, the number of peaks and three parameters of each peak were estimated in a self-generating initial parameter estimation using the B-spline functions. These parameters were refined by a nonlinear optimization technique using the Simplex method. For a series of V₂O₅/SiO₂, three types of vanadium oxide—such as a small cluster vanadate, surface polyvanadate, and crystalline vanadium oxide—were identified and quantitated by Raman spectroscopy. The small cluster surface species is shown to increase with vanadium loadings up to 6.6 wt % V₂O₅ and to convert into surface polyvanadate species at higher vanadium loadings or heat treatment.