Structural, optical and dielectric studies of KCl modified TeO2–Bi2O3–B2O3 glasses.

The quaternary glass system 60TeO2-(25−x)Bi2O3-15B2O3-xKCl has been prepared by the melt-quenching process with x ranging from 0 to 20 mol%. X-ray diffraction patterns confirmed the amorphous nature of the synthesized glasses, showing no sharp crystalline peaks. The techniques field emission scanning electron microscopy and energy dispersive X-ray spectroscopy provide information about the surface morphology and elemental composition of the synthesized glass system, respectively. Physical parameters such as density, molar volume, ion concentration, interionic distance, polaron radius, and cation field strength were calculated to determine structural stability. Density and molar volume both decrease with an increase in KCl content. Oxygen packing density decreases with increasing KCl concentration, indicating a rise in non-bridging oxygen atoms. Using differential scanning calorimetry, the glass transition temperature (Tg) was calculated. Its value is found to decrease as the KCl content increases. FTIR and Raman spectra indicate the transformation of TeO4 units into TeO3 units and BO4 units into BO3 units with an increase in KCl content. The diffuse reflectance spectra method is used to study optical parameters such as optical band gap, cut-off wavelength, Urbach energy, refractive index, and metallization criteria. The optical indirect band gap energies (Eopt) range from 2.78 to 3.31 eV and are calculated by applying Tauc's relation. On the other hand, the values of the urbach energy (EU) vary from 0.289 to 0.183 eV, indicating disorderliness or defects in the glass samples decrease with increasing KCl content. The synthesized glasses can be considered for non-linear optical applications since their metallization criterion (M) values ranged from 0.373 to 0.407. The dielectric parameters of the glasses were calculated on a frequency scale of 10–1 to 106 Hz by varying the temperature from 453 to 553 K. Dielectric analysis of the as-prepared glasses shows the non-Debye type behavior. [ABSTRACT FROM AUTHOR]