Elastic and structural properties of vanadium–lithium–borate glasses

Abstract

The ternary xV₂O₅–(40 − x)Li₂O–60B₂O₃ glass system, where x = 1, 2, 3, 4 and 6 mol%, was prepared by normal quenching. Ultrasonic velocities and attenuation were measured at room temperature using a pulse-echo technique. Various parameters, such as elastic moduli, micro-hardness, Poisson's ratio and Debye temperature, were determined from the measured densities and velocities. The composition dependence of these parameters, in addition to the glass-transition temperature, suggested that vanadium ions were incorporated into these glasses as a network modifier, resulting in the reconversion of BO₄ tetrahedra to BO₃ triangles by the breaking of B–O–B linkages and the formation of nonbridging oxygens (NBOs). The outcome was a reduction in network connectivity and rigidity with increasing V₂O₅ content. The results are explained quantitatively in terms of fractal bond connectivity, average atomic volume, network dimensionality, packing density, number of network bonds per unit volume, cross-link density and atomic ring size. The Makishima and Mackenzie model appears to be valid for the studied glasses when the fate of BO₄ tetrahedra and creation of NBOs are taken into account.

Keywords:

• mechanical properties
• ultrasonic attenuation
• glass transition temperature
• structure
• oxide glasses