Elastic properties and spectroscopic studies of Li2O-B2O3-V2O5 glasses

Elastic properties of Li2O-B2O3-V2O5 glasses have been investigated over a wide range of composition. Sound velocities (both longitudinal and transverse) have been measured using a pulse echo superposition method at a frequency of 10 MHz at room temperature. Compositional dependence of various elastic moduli, Poisson's ratio and Debye temperature has been studied as a function of Li2O and V2O5 concentrations. In general the moduli increase with the inter-substitution of Li2O/V2O5. However, glasses with high Li2O (> 45 mol%) the moduli tend to decrease. The variation in Poisson's ratio and Debye temperature shows that these glasses are mainly made up of covalently bonded network and are insensitive to shear stress. The results have been analyzed based on the structure of boro-vanadate glasses. An increase in the elastic moduli is mainly due to the presence of groups like diboro-vanadate and tetrahedral and trigonal borons. Glasses with high lithium content indicate reconversion of boron from tetrahedral to trigonal with non-bridging oxygens. IR and MAS-NMR spectra show the characteristic features consistent with structural analysis based on elastic property. (c) 2008 Elsevier B.V. All rights reserved.