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Some structure parameters of niobium borate glasses have been determined with the analytical data of X-ray diffraction and IR spectra. On the basis of experimental results, the model of the Nb 2 O 5 B 2 O 3 K 2 O (NBK) glass network was inferred to be framed by circular structural units which are composed of six-membered and four-membered groups of NbO 6 , BO 4 and BO 3 polyhedra in the glasses.

On the basis of extended X-ray absorption fine structure (EXAFS) results, Raman spectra and glass properties, this paper discusses the structure and properties of alkali niobosilicate glasses and their interrelationship. The experimental results indicate that these glasses have non-linear properties with increasing Nb2O5 concentration. The Raman spectra show that the peak due to the NbO stretching vibration at 650 cm−1 is strengthened, broadened and shifted to higher frequency as the Nb2O5 content is increased. At the same time, with the introduction of Nb2O5 the peaks due to the SiOSi asymmetric stretching vibration (1100 cm−1) and the SiO symmetric stretching vibration (560 cm−1) for the [SiO4] tetrahedra are gradually weakened. The characteristic peak due to the SiO bond disappears and a new peak (720 cm−1) emerges when the Nb2O5 concentration is 10 mol%.