Remark on the optical gap in ZnO–Bi2O3–TeO2 glasses

Four ZnO–Bi2O3–TeO2 glasses were prepared from high purity (4N5) oxides. From measurements of the optical transmission on very thin bulk samples the optical gap was determined at around 3.55 eV for the glasses studied. The temperature dependence of the optical gap was also determined from the room temperature close up to 500 K. Preliminary Raman scattering measurements indicate that with a decrease in TeO2 content, TeO4 trigonal bipyramid transformation proceeds into TeO3 trigonal pyramids.