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

Abstract

Zinc bismuth borate glasses with composition 10ZnO– x Bi 2 O 3 –(90 − x )B 2 O 3 (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 ( T g ) decreases from 473 °C to 449 °C as the content of Bi 2 O 3 increases. The optical absorption studies revealed that the cutoff wavelength increases while optical band gap energy ( E opt ) and Urbach energy (Δ E ) decreases with increase of Bi 2 O 3 content. The E opt values of these glasses are found to be in the range 3.464–3.169 eV where as the values of Δ E 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 Bi 2 O 3 concentration in the present glass system. The IR studies indicate that these glasses are made up of [BiO 6 ], [BO 3 ] and [BO 4 ] basic structural units. The values of optical basicity evaluated using oxide ion polarizability α b 2 − ( E opt ) obtained from optical band gap are in agreement with those values calculated from optical basicity values of the constituent oxides.