A study on the optical, structural, electrical conductivity and dielectric properties of a lithium bismuth germanium tungsten glasses

Highlights: ► I report, for the first time, the effect of WO3 on Bi2O3, Li2O, GeO2 and WO3 glasses through structural, optical, conductivity and dielectric studies. ► Optical band gap Eop for all types of electronic transitions, Urbach energy (Er), and refractive index determined. ► The WO3 promotes as bitter constituent the reduction of W6+ to W5+ giving the bluish color. ► Infrared spectra reveal characteristic GeO4, GeO6, Bi2O3, BiO6, WO4 and WO6 units. ► Based on ac and dc conductivity the conductivity increased and activation energies decreased with increase of WO3 content at all frequencies. - Abstract: Glasses in the system (65 − x)Bi2O3–15Li2O–20GeO2–xWO3 (where x = 2, 5 and 10 mol%) were prepared by normal melt quenching method. The change in density and molar volume in these glasses indicates the effect of WO3 on the glass structure. Fourier transform infrared (FT-IR) spectra show that these glasses are made up of GeO4, GeO6, BiO6, BiO3, WO4 and WO6 basic structural units. The structural units of BiO6, GeO6 and WO6 increase with the increasing of WO3 content. The optical constants of these glasses are determined over a spectral range, providing the complex dielectric constant to be calculated. Higher values for the refractive index and dispersion are recorded due to the high polarizability of bismuth and tungsten ions. The values of the optical band gap Eg for all types of electronic transitions and refractive index have been determined and discussed. The dc conductivity measured in the temperature range 423–623 K obeys Arrhenius law. The dielectric constant (ε′), dielectric loss (tan δ) and ac conductivity over a wide range of frequency and temperature, of the glasses were investigated.