Effect of Annealing on Optical Properties of ZnO·LiF·B2O3 Glasses

The Melt-quench method is used to synthesize zinc fluoroborate glasses with compositions x Z n O · ( 40 − x ) L i F · 60 B 2 O 3 ( x = 0 , 5, 10, 15, and 20). Optical characterization was carried out to examine the variation of optical bandgap energy ( E g ) and urbach energy ( E U ) with respect to the concentration for the samples annealed at different temperatures (300 ° C ,350 ° C, and400 ° C ). Annealing shows its effect on the samples with the variations in the values ofE gandE U . These variations are explained on the basis of formation of different molecular species likeBO 3-units, boroxol rings, and the change in the number of nonbridging oxygen atoms.