Abstract
Glasses in the system (1-x) [29Na(2)O - 4Al(2)O(3) - 67B(2)O(3)]-xZnO (0 <= x<<= 5 mol%), have been prepared by the melt quenching technique. Elastic properties, X-ray and FT-IR spectroscopic studies have been employed to study the role of ZnO on the structure of the investigated glass system. Elastic properties and Debye temperature have been investigated using sound wave velocity measurements at 4 MHz at room temperature. The results showed that the density increases and the molar volume decreases while both sound velocities and the determined glass transition temperatures decrease with increase in x. X-ray and infrared spectra of the glasses reveal that the borate network consists of diborate units and is affected by the increase in the concentration of ZnO content. These results are interpreted in terms of the decrease in the N-4 values (fraction of tetrahedral coordinated boron atoms), and substitution of longer bond lengths of Zn-O in place of shorter B-O bond. The results indicate that Zinc ions have been substituted for boron ions as tetrahedral network former ions. The elastic moduli are observed to increase with the increase of ZnO content. (C) 2008 Elsevier B.V. All rights reserved.