Elastic properties of Na_2O-ZnO-ZnF_2-B_2O_3 oxyfluoride glasses

摘要

Elastic properties of Na_2O-ZnO-ZnF_2-B_2O_3 oxyfluoride glasses with different ZnF_2 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 ZnF_2 shows decrease in the moduli initially, with further increase in ZnF_2 the moduli sharply increases and then again tend to decrease when ZnF_2 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 θ_D> with ZnF_2 indicates complex behaviour of the glass network. The results have been analysed in view of the modified borate glass network. Addition of ZnF_2 into the pure glass seems to influence the borate network by replacement of B-O-B linkages with B-O-Zn.