Effect of the Bi2O3 on the thermal, structural and chemical durability of some bismuth niobium phosphate glasses

Abstract

Abstract New Bismuth niobium phosphate glasses having the compositions xBi2O3-(95-x)P2O5-5Nb2O5 with x ranging from 10 to 17.5 mol% were prepared by melting quenching method. The absence of crystalline structure in the prepared phosphate glasses was confined by both X-ray diffraction and Differential Scattering Calorimetry studies. In the other hand, the effect of Bi2O3 on the chemical durability has been investigated and correlated to the structure using Raman spectral investigation. The relation between the structural changes and composition has been studied by the measurement of the density and glass transition temperature Tg. The obtained results show that the glass transition temperature and chemical properties (water-resistant qualities) increase with increasing compositions of bismuth oxide in all the studied glasses. The structure chains is broken into pyrophosphate groups (P2O7)4- and the P-O-P bonds are depolymerised by the incorporation of distorted Bi(6) units through P-O-Bi bonds. These experimental results agree with a closer structure and act in a manner that Bi2O3 enter the glassy matrix as a network former character