Synthesis and characterization of SiO2–Nb2O5systems prepared by the sol–gel method: structural stability studies

Maria Suzana P. Francisco, Yoshitaka Gushikem
2002 Journal of Materials Chemistry  
X-Ray diffraction (XRD), N 2 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 SiO 2 -Nb 2 O 5 systems prepared by the sol-gel method containing different amounts of Nb 2 O 5 and calcined at temperatures between 393 and 1473 K. For a small loading of niobia, amorphous niobium species were well dispersed in the silica
more » ... rsed 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-Nb 2 O 5 phase was observed at 1273 K, and the H-Nb 2 O 5 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 SiO 2 -Nb 2 O 5 system. The stability of the SiO 2 -Nb 2 O 5 system is confirmed by obtaining high specific surface areas even after the high temperature of calcination.
doi:10.1039/b200685e fatcat:hkecigvq2nhnvnlenfotxcdwei