Formation of gels and gel-glasses in the VO2(V2O5)-SiO2 systems

Blue-coloured gels have been prepared in the VO₂-SiO₂ system up to 80 mol% VO₂ by sol-gel technology using TEOS and aqueous solutions of VOSO₄·5H₂O. It is established by means of VIS and ESR spectra that at low temperatures VO²⁺ complexes are formed. An oxidation of V⁴⁺ has taken place with increasing temperature, and V₂O₅ and cristobalite have been separated. Silica gel glasses stable up to 800°C have been obtained from gels containing 1–3 mol% VO₂.