Optical properties of the Na2O–B2O3–Bi2O3–MoO3 glasses

Glasses with compositions (100 − x)Na2B4O7–0.5Bi2O3–0.5MoO3, with 0 ≤ x ≤ 40 mol% have been prepared using the melt quenching technique. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 300–1100 nm. The values of the optical band gap Egopt for indirect transition and refractive index have been determined for 0 ≤ x ≤ 40 mol%. The average electronic polarizability of the oxide ion αO2−αO2− and the optical basicity have been estimated from the calculated values of the refractive indices. The variations in the different physical parameters such as the optical band gap, the refractive index, the average electronic polarizability of the oxide ion and the optical basicity with Bi2O3 and MoO3 content have been analyzed and discussed in terms of the changes in the glass structure. The results are interpreted in terms of the increase in the number of non-bridging oxygen atoms, substitution of longer bond-lengths of Bi–O, and Mo–O in place of shorter B–O bond and the change in Na+ ion concentration.