Study of elastic moduli of lithium borobismuthate glasses using ultrasonic technique

Ultrasonic studies on x B2O325 Li2O(75 − x) Bi2O3, (0 ≤ x ≤ 75 mol%) glasses have been carried out. The elastic moduli of glasses have been investigated using ultrasonic velocity measurements at 4 MHz. The results revealed an increase of the ultrasonic velocity and Debye temperature with the increase of the B2O3 content which was attributed to the increase in the packing density, the local contraction of the network around the Bi and Li cations and the increase of the number of bonds per unit volume. Also, the increase of the elastic moduli with the increase in the B2O3 content is affected with the increase in the dissociation energy, the average cross-link density, the increase in the number of bridging oxygen atoms, and the substitution of high bond strength BO with low bond strength BiO. The optical properties such as the refractive index, the energy gap and the optical polarizability were evaluated from the values of the elastic moduli. It was observed that as the bulk modulus increases, the optical energy gap increases and both the refractive index and the optical basicity decrease.