Effect of Li2O on structure and optical properties of lithium bismosilicate glasses

Bismuth–silicate glasses containing lithium oxide having composition xLi2O·(85 − x)Bi2O3·15SiO2 (5 ≤ x ≤ 45 mol%) were prepared by melt quench technique. Density, molar volume and glass transition temperature for all the glass samples were measured. IR spectroscopy was used for structural studies of these glasses in the range from 400 to 1400 cm−1. The increase of Li2O content in glass matrix results in the decrease of the Si–O–Si bond angle and increase in the covalence nature of Bi–O bond. IR spectra suggest the presence of distorted [BiO6] octahedral units and the degree of distortion increases with the addition of Li2O in these glasses. The optical transmission spectra in the wavelength range from 200 to 3300 nm were recorded and optical band gap (Eg) was calculated. The values of Eg lie in between 2.81 and 2.98 eV. The values of average electronic oxide polarizability as well as optical basicity in these glasses were found to be dependent directly on Bi2O3/Li2O ratio.