Raman studies and some physical properties of selected (PbO) x(Nb 2O 5) y(TeO 2) 1−x−y glasses

Abstract

Selected Nb 2O 5–TeO 2, PbO–Nb 2O 5–TeO 2 and PbO–TeO 2 glasses were prepared from very pure oxides. The glass-transition temperature increased from 281 to 411 °C with an increase in Nb 2O 5 content and, simultaneously, the coefficient of thermal expansion decreased from 21 to 11 ppm/°C. Raman scattering measurements indicated that TeO 4 trigonal bipyramids, TeO 3+1, TeO 3 trigonal unit and NbO 6 octahedra were the basic structural units of Nb 2O 5–TeO 2 and PbO–Nb 2O 5–TeO 2 glasses. The optical band gap was determined in the region 3.39–3.60 eV and the coefficient of the temperature dependence of the optical gap for the temperatures between 30 and 250 °C in the region 4.1 × 10 −4–6.8 × 10 −4 eV/K was found. Non-linear refractive index of the studied glasses was estimated from the optical gap values at around 0.85 × 10 −11 esu.