Preparação e caracterização de vidros e vitrocerâmicas luminescentes no sistema ternário TeO2 - Nb2O5 - PbF2

Abstract

Oxyfluoride glasses and glass-ceramics not yet reported were prepared and characterized according to their thermal, structural and optical properties. The composition defined for these materials was TeO2 - Nb2O5 - PbF2, which vitreous domain was determined. Thermal and structural investigations indicated the network break, as well as distortions of seesaw units of TeO2 to trigonal pyramids. Such effect is more significant as the concentration of lead fluoride increases. Samples of composition (90 – x) TeO2 - 10 Nb2O5 - x PbF2, shown in molar concentrations, where x = 0, 10, 20, 30, and 25 in same cases, were doped with Eu2O3 and codoped with Er2O3/ Yb2O3. Additional structural information were obtained by luminescence studies of Eu3+ ions, which reveal the environment around europium has a tendency to increase according to the increase of PbF2. Quantum efficiency of the Eu3+ ions was estimated in different matrices by the calculations of Judd-Ofelt, and was verified a tendency of increase according to the increase of PbF2 in the glass network. These results point out the ability of lead fluoride to reduce the phonon energy of the glass matrix. Luminescence studies of Er3+ ions showed effective emissions at 1,55 µm, wavelength of interest for applications of this material as optical amplifier. Although quantum efficiency of the Er3+ ions were not calculated, more intense emissions were observed in matrices containing lead fluoride and even higher in the glass-ceramic with same composition. Glass-ceramics were prepared by means of the conventional method of heat treatment of a glass, doped and undoped with rare-earths. Through the glasses doped with europium and codoped with erbium and ytterbium, glass-ceramics containing tetragonal Pb2OF2 as crystalline phase were obtained. These glass-ceramics present high transparency in the visible range, which extend its potential of applications. Therefore, the detailed investigation of this system has allowed the obtaining of materials not yet reported, with relevant properties for application in the optical area.