Influence of vanadium addition on the optical and photoluminescence properties of borate glasses and their glass–ceramic derivatives

Abstract

Nominal B2O3–Na2O–CaO–SrO glasses containing various concentrations of V2O5 ranging from 5 to 40 mol% have been prepared by normal melting and quenching procedure. Data obtained from differential scanning calorimetry (DSC) of the parent glasses were used to prepare glass–ceramic. X-ray diffraction (XRD) patterns of glasses reveal an absence of any identified crystalline phases; while, patterns of the heat-treated glasses showed the crystallization of calcium vanadate (Ca3V2O8), sodium borate (Na2B6O10) and sodium vanadate (NaV3O8) phases. UV–Visible spectra demonstrated characteristic absorption in the UV region centered at ~ 234 and 360 nm that extended to the visible region with increasing V2O5 content. Consequently, the estimated optical parameters such as optical band gap (Eopt), Urbach energy (∆E) and refractive index were dependent on V2O5 content. Photoluminescence spectra were measured before and after crystallization indicating development in the emission spectra after heat treatment. The glasses reveal two sharp emitted peaks at about 466 and 552 nm while the glass–ceramic derivatives depicted an extended emission peak centered at about 700 nm. Based on FTIR data, tetrahedral and trigonal borate groups were identified beside VO4 group when V2O5 was added to the parent glasses. Infrared structural measurements reveal the dual role of V2O5 as glass modifier or former depending on its concentration.