Physical, thermal, structural and optical absorption studies of vanadyl doped magnesium oxy-chloride bismo-borate glasses

• Density decreases and molar volume increases with increase in MgCl2 substitution.
• Octahedral nature of V4+O6 is enhanced by increasing Cl− concentration.
• Tg and Tx have maximum values for sample containing 20% MgCl2.
• FTIR spectra contain peaks due to both borate and bismuthate groups.
• Eopt is maximum for sample containing 20% MgCl2.

Oxy-chloride bismuth-borate glasses with composition xMgCl2·(30 − x)MgO·20Bi2O3·50B2O3 containing 2 mol% doping of V2O5 (x = 12, 15, 20, 25 and 30) are prepared by melt-quenching technique. The structural, thermal and optical behaviors are explained by analyzing the data obtained from density (D), molar volume (Vm), theoretical optical basicity (Λth), differential scanning calorimetry (DSC), FTIR and UV–vis results. A decrease in D and increase in Vm (except for sample MBV3 for which D is maximum) on increasing chloride content suggests the formation of non-bridging oxygen atoms. Maximum glass transition temperature (Tg) and crystallization temperature (Tx) have been observed for sample MBV3. The glass stability (S) and stability ratio (S/Tg) have been calculated from the values of Tg and Tx and both are having maximum values for sample MBV3. Study of the FTIR spectra in the mid-IR range reveals the presence of both triangular and tetrahedral coordinated boron. The optical studies through UV–vis spectral analysis show non-sharp edge. The optical band gap (Eg) is also maximum for sample MBV3.