Mixed alkali tungsten borate glasses – Optical and structural properties

Glasses with composition xLi2O-(30-x)Na2O-10WO3-60B2O3 (where x = 0, 5, 10, 15, 20, 25, and 30 mol%) were prepared by the melt quenching technique. Density, refractive index and glass transition temperature varies non-linearly with glass composition indicting the presence of mixed alkali effect. Optical energy band gap for various indirect and direct (allowed and forbidden) transitions were determined using Tauc plots. IR spectral study reveals the existence of BO3 and BO4 groups with W–O–W vibrations in the present glasses. Based on good correlation among refractive index based electronic polarizability of oxide ions, optical basicity and the Yamashita–Kurosawa’s interaction parameter, the present Li2O–Na2O–WO3–B2O3 glasses were classified as semi covalent oxides.

► The MAE in the Li2O–Na2O–WO3–B2O3 glasses was studied through density, optical and MDSC.
► Optical band gap (Eopt) and Urbach energy (ΔE) have been evaluated.
► The FTIR studies on the present glasses indicates the presence of BO3, BO4, WO3, WO6 and Li units.
► The values of Eopt and ΔE show non-linear behavior with compositional parameter showing the MAE.
► The glass basicity and interaction parameter were observed to be less.