Physical and optical properties of Bi2O3-B2O3 glasses

Bismuth borate glasses with composition xBi2O3-(100-x) B2O3 (where x is in mol %, ranging from 25 to 50 in steps of 5) have been prepared using conventional melt quenching technique. The physical parameters like molar volume, oxygen packing density and optical basicity have been evaluated from the measured values of density. It is found that density, molar volume and optical basicity increases where as oxygen packing density decreases with increase of bismuth content. 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 3.338 to 3.025 eV where as the values of ΔE lies in the range 0.467 to 0.237 eV. Using Eopt values the oxide ion polarizability values have been evaluated. The values of optical basicity evaluated using oxide ion polarizability αo2- (Eopt) obtained from optical band gap are in agreement with those values calculated from optical basicity values of the constituent oxides.