Ultrasonic studies on alkali borate tungstate glasses

Longitudinal and shear ultrasonic wave velocities have been measured in different compositions of the glass system 20Li2O–(80−x)B2O3–xWO3 (0⩽x⩽12.5 mol%), at room temperature and at 4 MHz frequency. Elastic moduli, Debye temperature and Poisson's ratio have been obtained as a function of WO3 content. Based on FTIR spectroscopy and theoretical bond compression model, quantitative analysis has been carried out in order to obtain more information about the structure of these glasses. The longitudinal ultrasonic wave velocity measurements showed a bend at about 2.5 mol% WO3 content while shear ultrasonic wave velocity decreased monotonously with an increase of WO3 content. Elastic moduli values decreased as WO3 content increased from 0 to 2.5 mol%. Further increase of WO3 beyond 2.5 mol% increased the elastic moduli values. It is suggested that these behaviours are mainly due to the presence of WO3 in the network structure of these glasses as a network modifier when WO3 content is between 0 and 2.5 mol%, and acts as a network former above 2.5 mol%.