Mixed alkali effect in physical and optical properties of Li2O-Na2O-WO3-B2O3 glasses

Glasses with composition xLi(2)O-(30-x)Na2O-10WO(3)-60B(2)O(3) (where x = 0, 5, 10, 15, 20, 25 and 30 mol%) have been prepared using the melt quenching technique. In the present work, the mixed alkali effect (MAE) has been investigated in the above glass system through density and modulated DSC studies. The density and glass transition temperature of the present gasses varies non-linearly, the exhibiting the mixed alkali effect. From the optical absorption studies, the values of direct optical band gap, indirect optical band gap energy (E-o) and Urbach energy(Delta E) have been evaluated. The values of E-o and Delta E vary non-linearly with composition parameter, showing the mixed alkali effect. The electronic polarizability of oxide ions, optical basicity and the Yamashita-Kurosawa's interaction parameter have been examined to check the correlation among them and bond character. Based on good correlation among electronic polarizability of oxide ions, optical basicity and the Yamashita-Kurosawa's interaction parameter, the present Li2O-Na2O-WO3-B2O3 glasses were classified as normal ionic (basic) oxides. (C) 2012 Elsevier B.V. All rights reserved.