Raman spectra and optical band gap in some PbO-ZnO-TeO2 glasses

The glasses PbO–ZnO–TeO2 were prepared with a classic melting method. The substitution of ZnO by PbO results in an increase in the density from 5.83 to 6.52 g/cm3 and in the refractive index from 2.19 to 2.25. In addition, the optical band gap and the glass-transition temperature decrease from 3.79 to 3.5 eV and from 314 to 281 °C, respectively. The estimated values of the non-linear refractive index from the optical band gap are comparable with the values typical for TeO2 based glasses. The Raman spectra indicate that the substitution of ZnO with PbO leads to a decrease in the density of Te–O–Te linkages while increasing both the density of Pb–O–Te linkages and also the number of non-bridging oxygen. •Substitution of ZnO with PbO decreases the optical band gap from 3.79 to 3.5 eV.•Raman spectra indicate the following transformation: [Te3O8]4– .→ 2 [TeO3]2– + TeO2•The estimated values of the non-linear refractive index are around 7 × 10−12 esu.