FTIR and ultrasonic investigations on modified bismuth borate glasses

Studies on xRO · 30Bi2O3 · (70−x)B2O3 glasses have been carried out (0 ⩽ x ⩽ 30 mol%, R = Zn, Ba). Elastic properties and Debye temperature have been investigated using sound velocity measurements at 4 MHz. The ultrasonic parameters along with the IR spectroscopic studies have been employed to explore the role of divalent cations in the structure of the studied glasses. Analysis of infrared spectra indicates that RO is preferentially incorporated into the borate network, forming BO4 units. It is assumed that Bi2O3 enters the structure in the form of BiO6 only. The change of density and molar volume with RO content reveals that BO4 units linked to R2+ cations are denser than those linked to positive sites in the Bi2O3 network. Predicted values of four co-ordinated boron put forward questions about the reliability of assignment of structural units that Bi2O3 may form.