Investigations of optical, structural and thermal properties of newly borotellurite glass system for possible photonic applications

Borotellurite glasses of composition (0.4Li2O 0.4MgO)0.2TMO(1.4B2O3 0.6TeO2) with TMO: MoO3, WO3 or Bi2O3 were synthesized by standard melt quenching technique. The X-ray diffraction (XRD) technique confirmed the amorphous nature of the prepared samples. FTIR studies have explored the presence of structural units and bending vibrations. It was confirmed that the glassy matrix of these systems was based mostly on BO3/BO4 units, and TeO3/TeO4 units in less proportion. UV-vis spectroscopy was employed to examine some optical properties. Changes induced by the three transition metal oxides on the glassy matrix produce modifications in the optical band gap, Urbach's energy, refractive index and permittivity values, related to their different sizes regarding to their different ionic radius. A double analysis following the Tauc and the DASF methods confirms allowed direct inter-band electronic transitions in the studied glasses. In this work, we can observe that high values of density, high refractive index and high polarizability suggest that LMBT: Bi glass is suitable for activating with Dy3+ ions.