Effect of B2O3 and Li2O on vibrational, thermal and optical properties of 50Bi2O3-15PbO-(35-x)B2O3-xLi2O (0 ≤ x ≤ 25 mol%) glasses

Bi2O3 based glasses have been proven as promising optical materials with regard to their 6 s2 lone pair electrons. By melt quenching, the highly thermal stable glasses 50Bi2O3-15PbO-(35-x)B2O3-xLi2O (where 0 ≤ x ≤ 25 mol%) were prepared. The short range order of the glasses was verified with XRD and DSC measurements. DSC analysis showed that thermal parameters varied non-linearly with increase of Li2O. Density (ρ), molar volume (Vm), oxygen packing density (OPD) and oxygen molar volume (Vo) were calculated and their compositional dependency was discussed in detail. Energy dispersive X-Ray (EDX) spectrometry analysis validated the stoichiometry of sample composition. FTIR analysis illustrated that the glass network comprise of BiO3, BiO6, BO3 and BO4 structural units together with non-bridging oxygens. The computed optical properties like optical band gap (Eopt), refractive index (n), Urbach energy (∆E), molar refraction (RM), metallization criterion (M) and oxide ion polarizability (αO2-) were observed to be non-linearly varied with the addition of Li2O. The interplay between the structural roles of Li2O and Bi2O3 was instrumental for the observed variations in all the properties. BiPBL4 glass showed the highest thermal stability (175 °C) and the high kgl value among the glass series. The incorporation of Li2O in presence of low mol% of B2O3 with Bi2O3-PbO endowed these glasses to have the low phonon energy. The analysis carried out in this work showed that these glasses might useful for optoelectronic devices and optical fiber drawing applications. •FTIR studies showed that the glasses consist of BO3, BO4, BiO3, BiO6 units.•The glasses exhibited the lower phonon energies in comparison with B2O3 based glasses.•Thermal and optical properties are nonlinearly varied with increase in Li2O content.•BiPBL4 glass exhibited the high thermal stability (175 °C) and is useful in optical fibers.