Raman and infrared spectra are reported for silica gel with a specific surface area, S-BET, of 322 m(2) g(-1) and an average pore size diameter of 6 nm and for silica gel chemically modified with niobium(V) oxide by grafting reaction, and thermally treated at 473-1573 K. Silica gel heated at 1273 K exhibits infrared and Raman band characteristics of alpha-quartz bands, while those heated to 1473 or 1573 K show infrared and Raman bands typical of alpha-cristobalite. Raman spectra obtained for Nb2O5-SiO2 samples heated above 1273 K upon excitation with 647.1 nm radiation were distinct from the Raman spectra excited by 488.0 and 1064 nm radiation.73293302