Structural, physical and optical study of calcium modified bismuth borovanadate glasses: V2O5-B2O3-Bi2O3-CaO

Abstract

Comprehensive research into quaternary glass systems' structural, physical, and optical characteristics was conducted, specifically for glass series 60V2O5-20B2O3-(20-x)Bi2O3-xCaO, where x = 0-20 mol%. Using X-ray diffraction (XRD), their non-crystalline character was confirmed. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) were used for morphological study to confirm glass formation. Several techniques were employed to investigate the effects of incorporating CaO on the physical, optical, and structural characteristics of glasses composed of bismuth boro-vanadate. As-prepared glass samples have been analysed to determine how density (ρg), crystalline volume (Vcryst), molar volume (Vm), and oxygen packing density (OPD) changes with composition. Additional determined physical parameters include interionic distance (Ri), Calcium yields field (F), ion concentration of Ca2+ (N), and polaron radius (Rp). DSC thermograms reveal that glass transition temperature (Tg) rises in tandem with the concentration of calcium oxide, demonstrating an improvement in the glass system's thermal stability. FTIR and Raman spectroscopy examination of all glass samples confirmed that V2O5 forms a network with VO5 units. After x = 10 mol%, the proportion of non-bridging oxygens in the glass matrix rises as VO5 units are converted into VO4 units along with the transformation of BO3 units into BO4 units. Bi2O3 is found in glass matrix in BiO6 and BiO3 units. As concentrations of calcium oxide were increased, UV–Visible spectroscopy revealed nonlinear trends in various optical parameters such as optical energy (Eopt), Urbach energy (EU), cut-off wavelength (λC), molar refractivity (RM), metallization criterion, and refractive index (n). The glasses prepared in this study exhibit high-level optical basicity (ranging from 1.164 to 1.238), electronic oxide ion polarizability (3.304–3.869), and metallization criterion (0.249–0.304). These findings point to the possibility that the glasses can be suitable for non-linear optical applications.