Ultrasonic study and physical properties of some borate glasses

The structure of the glass system (75-x)B2O3-xBi2O3-25Li2O, where x=5, 10, 15, and 20 mol% was investigated by using pulse-echo technique. Elastic properties of the glass system have been calculated together with Poisson's ratio and Debye temperature from the measured densities as well as longitudinal and shear ultrasonic velocities at room temperature. Ultrasonic velocity measurements were taken at 4 MHz. Estimated parameters based on Makishima-Mackenzie theory and bond compression model were calculated in order to analyse the experimental elastic moduli. Addition effect of Bi2O3 on the elastic moduli was investigated in terms of the number of network bonds and the mean cross-link density of the glass systems. The average atomic ring size of the network was also calculated and it was found that it depends on the concentration of the modifiers. Composition dependence of the elastic moduli and Poisson's ratio from one hand and the trend of both the ring diameter and the packing density from the other hand showed structural change at x=15 mol%