Raman spectra and optical properties of selected Bi 2O 3–PbO–B 2O 3–GeO 2 glasses

Abstract

Glasses of the system (Bi 2O 3) 0.2(PbO) x (B 2O 3) 0.8−2 x (GeO 2) x , where x = 0.05, 0.1, 0.2, and 0.3, were prepared and investigated. With increasing x, both the density ( ρ) and molar volume increased from 5.85 g/cm 3 to 7.02 g/cm 3 and from 27.06 cm 3/mol to 29.25 cm 3/mol, respectively, while the dilatometric glass-transition temperature ( T g) decreased from 448 °C to 385 °C. Raman spectra showed that with increasing x, the number of groups based on trigonal boron raised and also increased the amount of various three body linkages which enhanced a structural disorder. From the measurements of the optical transmission on very thin glassy samples, the optical energy gap values ( E g, 300 K) were determined in the range 3.60 ( x = 0.05)–3.46 eV ( x = 0.3). The temperature dependence of the optical energy gap ( E g( T)) in the region 300–600 K was examined and approximated by the linear relation in the form of E g( T) = E g(0) − γT, where γ × 10 −4 (eV/K) varied from 4.43 to 5.6. Non-linear refractive index ( n 2) was estimated at around 8.15 × 10 −12 (esu) from the optical energy gap values.