Comprehensive study on compositional dependence of optical band gap in zinc soda lime silica glass system for optoelectronic applications

Zinc soda lime silica (ZnO-SLS) glass system with composition x(ZnO)100-x(SLS) (x = 0, 10, 20, 30, 40 and 50 wt.%) were synthesized by the conventional melt-quenching technique. The structural and optical properties of the glasses are measured using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM) and UV-Visible (UV-Vis) absorption spectroscopy. The optical band gaps were determined by analyzing the optical absorption edge using the Mott-Davis model. A differential method based on Mott-Davis model are used to obtain the type of transition and optical band gap (E-opt) which in turn was compared with the value of E-opt obtained using the extinction coefficient. The analysis shows that in ZnO-SLS glasses, the optical band gap arises due to direct forbidden transition. Progression of ZnO content cause the absorption edge shifts toward longer wavelengths and decreases the optical band gap. This behavior can be explained in terms of changes to the Zn-O chemical bonds with glass composition. Furthermore, in the case of glasses containing increasing amounts of ZnO, a change of the role of zinc ions in the glass matrix was confirmed from the modifier to a structure forming component. (C) 2016 Published by Elsevier B.V.