Elastic properties of Na2O-ZnO-ZnF2-B2O3 oxyfluoride glasses

Abstract

Elastic properties of Na2O-ZnO-ZnF2-B2O3 oxyfluoride glasses with different ZnF2 concentrations have been investigated using ultrasonic velocity measurements at room temperature, at a frequency of 10 MHz. Glasses prepared by melt quenching method were suitably polished for the ultrasonic velocity measurements using pulse-echo superposition method. Various elastic moduli have been calculated and their compositional dependence has been examined. The compositional dependence of elastic moduli with the concentration of ZnF2 shows decrease in the moduli initially, with further increase in ZnF2 the moduli sharply increases and then again tend to decrease when ZnF2 concentration is 20 mol%. The values of Poisson's ratio lie in the range of 0.24-0-30, which is typical to covalent bonded network. The variation of 66 with ZnF2 indicates complex behaviour of the glass network. The results have been analysed in view of the modified borate glass network. Addition of ZnF2 into the pure glass seems to influence the borate network by replacement of B-O-B linkages with B-O-Zn.