Abstract

X-Ray diffraction (XRD), N₂ absorption (BET specific surface area), transmission electron microscopy (TEM), Raman and Fourier infrared (FT-IR) spectroscopic techniques have been applied to characterize the texture, structure and niobia–silica interaction of SiO₂–Nb₂O₅ systems prepared by the sol–gel method containing different amounts of Nb₂O₅ and calcined at temperatures between 393 and 1473 K. For a small loading of niobia, amorphous niobium species were well dispersed in the silica up to 1273 K. Crystallization is observed only after thermal treatment at 1473 K, with the T-phase predominating as observed by XRD and TEM analyses and confirmed by Raman spectra. For samples with a higher amount of niobia, the formation of a T-Nb₂O₅ phase was observed at 1273 K, and the H-Nb₂O₅ phase predominates at 1473 K. FT-IR results indicate the presence of Si–O–Nb linkages at the silica–niobia interface, formed during preparation, which are responsible for the higher structural stability of the SiO₂–Nb₂O₅ system. The stability of the SiO₂–Nb₂O₅ system is confirmed by obtaining high specific surface areas even after the high temperature of calcination.