Effect of CdO on the Structural and Spectroscopic Properties of Germanium-Tellurite Glass

New glasses in the xCdO-(90 - x)TeO₂-10GeO₂ system were obtained by the conventional melt-quenching process at 900 °C. The glasses were transparent to the naked eye. The diffraction patterns indicate that the samples were mostly amorphous, except for the CdO-rich glasses, in which the formation of nanocrystals of CdO and Cd₃TeO₆ were identified. Raman spectroscopy analysis of the samples displayed the existence of TeO₃, TeO₃₊₁, TeO₄, and GeO₄, structural units within the glass matrix. The optical band gap of the glass samples was determined by optical absorption spectroscopy using the Tauc method. Depending on the relative content of TeO₂, their values varied in the range of 2.32-2.86 eV. The refractive index was obtained from the band gap values. The XPS measurements showed that Ge 3d, O 1s and Te 3d_3/2, Te 3d_5/2, Cd 3d_5/2, and Cd 3d_3/2 doublets shifted to higher binding energy values as the amount of TeO₂ was increased. The binding energy values of the Te 3d doublet are related to the TeO₄ and TeO₃ groups.