The optical band gap and the tailing states determination in glasses of TeO2-V2O5-K2O system

Ternary amorphous samples of 50TeO₂-(50 ? x)V₂O₅-xK₂O compositions with 0 ≤ x ≤ 20 (in mol %) have been prepared using the press-melt quenching method. The optical absorption spectra of glass have been recorded in the wavelength range 300–900 nm by UV-visible spectrophotometer. According to The Tauc and Urbach theories, the optical band gap and width of the tail of localized states have been evaluated. In addition the temperature glass transition (T _g ) of glasses have been determined by differential scanning calorimetry, confirming the amorphous nature of samples. The density and molar volume have been studied, indicating act of K₂O as network modifier.