MIXED ALKALI EFFECT IN (40-x)K2O–xLi2O-10Na2O–50B2O3 GLASSES—PHYSICAL AND OPTICAL ABSORPTION STUDIES

Abstract

So far only a handful of publications have been concerned with the study of the mixed alkali effect in borate glasses containing three types of alkali ions. In the present work, the mixed alkali effect (MAE) has been investigated in the glass system (40–x) K2O–x Li2O –10Na2O–50B2O3. (0≤x≤40 mol%) through density and modulated DSC studies. The density and glass transition temperature of the present glasses varies non-linearly exhibiting mixed alkali effect. We report the mixed alkali effect in the present glasses through optical properties. From the absorption edge studies, the various values of optical band gap (Eo) and Urbach energy (ΔE) have been evaluated. The values of Eo and ΔE show non-linear behavior with compositional parameter showing the mixed alkali effect. The band gap energy based average electronic polarizability of oxide ions αO2–(Eo) , optical basicity A(Eo) , and Yamashita–Kurosawa’s interaction parameter A(Eo) have been examined to check the correlations among them and bonding character. Based on good correlation among electronic polarizability of oxide ions, optical basicity and interaction parameter, the present K2O– Li2O–Na2O–B2O3 glasses are classified as normal ionic (basic) oxides.