Insights into the influence of Bi₂O₃ on the structural and optical characteristics of novel Bi₂O₃–B₂O₃–TeO₂–MgO–PbO glasses

Glass samples comprising Bi₂O₃, B₂O₃, TeO₂, MgO, and PbO were fabricated using melt quenching. Substituting B₂O₃ with Bi₂O₃ resulted in a steady density increase from 2.88 to 7.16 g/cm³ due to the difference in atomic weight between the heavier Bi (208.98 g/mol) and lighter B (10.811 g/mol). As the Bi₂O₃ concentration rose from 0 to 60 mol%, the molar volume (Vm) gradually increased from 31.02 to 45.69 cm³/mol, owing to the discrepancy in the radii of the Bi³⁺ and B³⁺ ions, measuring 0.96 and 0.84 Å, respectively. Increasing the non-bridging oxygens (NBOs) led to a corresponding rise in the molar volume. Incorporating varying concentrations of Bi₂O₃, ranging from 0 mol% (BMTPBi0) to 60 mol% (BMTPBi60), induced alterations in several physical parameters, consequently affecting the structural characteristics of the glass. Raman analysis confirmed that an increase in Bi₂O₃ content within the glass composition led to the conversion of TeO₄ to TeO₃, resulting in the transformation of bridging oxygens into NBOs. As the Bi₂O₃ content increased, there was a 3.080–2.090 eV decrease in the optical band gap energy as a result of the rise in NBOs (and consequently, an increase in disorder), leading to a rise in Urbach energy from 0.390 to 0.740 eV. The optimal sample was determined as BTMPBi30 due to its balanced properties and potential advantages. The BTMPBi30 as modifier with heavy metal has high transmittance. The band gap energy of BTMPBi30 (2.920 eV) is reasonable and falls within the range suitable for many optical applications. The Urbach energy increases with Bi₂O₃ content, and for BTMPBi30 (ΔE = 0.480 eV), it is within an acceptable range, indicating a certain level of disorder. Under 300 nm excitation, the photoluminescence spectra indicate distinct emission bands dependent on the species Bi³⁺ and Pb²⁺, making BTMPBi30 a potential candidate for applications requiring photoluminescent properties.