Structural, optical and thermal properties of sodium borate oxide glasses: Effect of bismuth

Sodium borate glasses doped with varying concentrations of Bi 2 O 3 were synthesized using the melt-quenching technique to evaluate the effect of Bi 2 O 3 on their physical, structural, optical and thermal properties. X-ray diffraction confirmed that all the prepared samples were amorphous. The density and molar volume showed an increasing trend with the addition of bismuth oxide. The derived physical parameters revealed higher ion concentration and field strength, along with reduced interionic distance and polaron radius, indicating improved charge carrier confinement and network compaction. FTIR and Raman analyses revealed the presence of borate structural units as well as Bi–O related vibrations, confirming structural modification caused by bismuth incorporation. Optical analysis indicated reduced band gap and enhanced polarizability. Differential scanning calorimetry revealed an increase in thermal stability, indicating greater resistance to crystallization. The combined structural, optical and thermal enhancements suggest that the investigated glasses are promising candidates for optical fiber related applications.