Effect of stepwise replacement of LiF by ZnO on structural and optical properties of LiF.B2O3 glasses

Zinc fluoroborate glasses with compositions xZnO.(40 – x)LiF.60B 2O3(x = 0, 5, 10, 15, and 20) weresynthesized by the melt-quench method. The amorphous nature of the glassy samples was confirmed by XRD analysis. The nature of the bonds formed and the role of various species in the composition of the glasses were examined using FTIR spectroscopy. FTIR analysis showed shifting of an absorption band with the addition of ZnO. A UV-visible study was carried out to calculate the optical band gap energy, Eg . It was found that Eg decreased with increase in concentration of ZnO up to x = 15 and increased slightly for x = 20 with the stepwise replacement of a nonoxide group (LiF) by an oxide group (ZnO). Urbach tail energy, EU , was found to increase from x = 0 to x = 15 and then decreased slightly for x = 20. Theoretical optical basicity, Λth , decreased with decrease in concentration of LiF.