Structural, Physical, Thermal, and Optical Analysis of Lead Modified Bismo–Borovanadate Glassy System: V2O5–B2O3–Bi2O3–PbO.

In the present study, lead-modified bismuth borovanadate glasses were synthesized using the conventional melt-quench technique, maintaining a fixed composition of (50 − x)V2O5–40B2O3–10Bi2O3–xPbO, where x ranged from 5 to 25 mol% in 5 mol% increments. To confirm the amorphous nature of the samples, X-ray diffraction was utilized. Several physical properties, including density (ρg) (3.55 to 4.41 g/cm3), molar volume (Vm) (47.21 to 39.83 cm3/mol), crystalline volume (Vc) (42.09 to 35.94 cm3/mol), and oxygen packing density (OPD) (80.49 to 75.32 g-atom/l), were examined and found to exhibit composition-dependent variations. Additionally, various other parameters were determined, including interionic distance (Ri) (1.16 to 0.65 cm−1), lead yield field (F) (0.38 to 1.21 cm−2), concentrations of Pb2+ ions (N) (ranging from 0.64 to 3.78 ions/cm3), and Polaron radius (Rp) (ranging from 4.68 to 2.60 cm−1). The analysis of DSC thermograms revealed a positive correlation between the concentration of lead oxide and the glass transition temperature (Tg), which varied from 254 to 295 ºC. This suggests an improvement in the thermal stability of the glass system with increasing lead oxide content. Structural investigations using infrared and Raman spectroscopy indicated that V2O5 served a dual role as a network former (with VO5 units) and as a modifier (with VO4 units). The presence of PbO and Bi2O3 as modifiers facilitated the transformation of BO3 units into BO4 units and the formation of diborovanadate ([B2V2O9]2−) groups and strong B–O–V linkages. The optical energy band gap (Eopt), determined through UV–visible spectroscopy, showed a consistent increase with the progressive incorporation of PbO. Both direct allowed (1.986 to 2.392 eV) and indirect allowed (1.582 to 2.087 eV) band gaps exhibited this rising trend. Furthermore, the prepared glasses demonstrated a high level of optical basicity (1.182 to 1.168), electronic polarizability (3.419 to 3.327) of oxide ions, third-order non-linear optical susceptibility (0.141 to 0.063 × 10–10 esu), and metallization criterion (0.281 to 0.323). These results suggest that the glasses prepared in this study have the potential for use in non-linear optical applications. [ABSTRACT FROM AUTHOR]