Abstract
Glasses in the system Na2-2xB4-4xBixMo0.5xO7-4x, 0 <= x <= 0.4, have been prepared by the melt quenching technique. Elastic properties and IR spectroscopic studies have been employed to study the role of Bi2O3 and MoO3 on the structure of Na2B4O7 glass. Elastic properties and Debye temperature have been investigated using sound velocity measurements at 4 MHz. The results showed that the density and the molar volume increase while both sound velocities and the determined glass transition temperatures decrease with increase in x. Infrared spectra of the glasses reveal that the strong borate network consists of diborate units and is affected by the increase in the concentration of Bi2O3, and MoO3. These results are interpreted in terms of the increase in the number of non-bridging oxygen atoms, substitution of longer bond lengths of Bi-O, and Mo-O in place of shorter B-O bond and the change in Na+ ion concentration. The results indicate that bismuth and molybdenum ions have been substituted for boron ions as network modifier ions. The elastic moduli are observed to increase with the increase in Bi2O3 and MoO3 content. This contradiction in the elastic moduli-molar volume relation is attributed to the role of the respective bonds.