Effect of Bi2O3 on physical, optical and structural studies of ZnO–Bi2O3–B2O3 glasses

Zinc bismuth borate glasses with composition 10ZnO–xBi2O3–(90 − x)B2O3 (where x is in mol%, ranging from 25 to 50 in steps of 5) have been prepared using conventional melt quenching technique. Differential scanning calorimetry (DSC) studies showed that the glass transition temperature (Tg) decreases from 473 °C to 449 °C as the content of Bi2O3 increases. The optical absorption studies revealed that the cutoff wavelength increases while optical band gap energy (Eopt) and Urbach energy (ΔE) decreases with increase of Bi2O3 content. The Eopt values of these glasses are found to be in the range 3.464–3.169 eV where as the values of ΔE lies in the range 0.503–0.178 eV. The DSC and optical absorption studies revealed that the glass network becomes less tightly packed and degree of disorder increases with increase in Bi2O3 concentration in the present glass system. The IR studies indicate that these glasses are made up of [BiO6], [BO3] and [BO4] basic structural units. The values of optical basicity evaluated using oxide ion polarizability αb2−(Eopt)αb2−(Eopt) obtained from optical band gap are in agreement with those values calculated from optical basicity values of the constituent oxides.