Effect of Stepwise Replacement of LiF by Bi2O3 and of Annealing on Optical Properties of LiF⋅B2O3 Glasses

Bismuth fluoroborate glasses with compositions Bi2O3⋅(40−)LiF⋅60B2O3(=0,5,10,15,and20) are synthesized by melt-quench method. Optical characterization was carried out to examine variation of optical band gap energy () and Urbach energy () with respect to the concentration. It reflects the effect of stepwise replacement of non-oxide and less polarizable LiF by an oxide and more polarizable (Bi2O3) group on the optical properties of the samples. The value of decreases with increase in concentration of Bi2O3. The samples were subjected to annealing at different temperatures (300°C, 350°C, and 400°C), and the effect of annealing on the optical properties of various samples was again studied. Annealing affects remarkably the values of and in the samples with =0.