Caracterização das propriedades espectroscópicas e termo-ópticas de vidros teluretos TeO2-Li2O-ZnO dopados com Er2O3

Abstract

Tellurite glass samples in the composition 65TeO2-15Li2O-20ZnO were doped with different concentrations of Er2O3 and investigated in this work. Samples were synthesized using the method of melting quenching in air atmosphere. The characterization of its thermal, optical, spectroscopic, and thermo-optical properties was carried out using the techniques of optical absorption, luminescence, lifetime, thermal lens spectroscopy, thermal mirror spectroscopy, and other complementary techniques. The optical absorption measurements in the UV-Vis-NIR regions showed the incorporation of Er3+ ions in the glasses obtained. Under 488 nm excitation samples showed emission in the green and red regions, with the band referring to the 4S3=2 ! 4I15=2 (552 nm) transition being the most intense. Samples with concentrations greater than 0,5 mol% of Er2O3 showed luminescence quenching. In the near-infrared region, the most intense emission bands were those referring to the transitions from levels 4I11=2 (992 nm) and 4I13=2 (1550 nm) to the fundamental level, which showed a relative increase in intensity as a function of the dopant concentration and slightly higher lifetime values than those found in the literature for tellurite glasses. Under 975 nm excitation, upconversion emission was observed, with bands also in the regions of green and red and a relative increase in red emission with the doping increase. The quadratic dependence on the excitation power was assessed, indicating that two photons are contributing to the process. The emission band at 1550 nm showed an increase in width at half height with a smaller amount of dopant when compared to other vitreous systems. This opens the possibility of using the host matrix as a band amplifier in the infrared region. Judd-Ofelt parameters ( t) were also determined, which indicated the formation of TeO3 units, which cause changes in polarizability and symmetry around the Er3+ ions with the increase of dopant in the matrix. From the JO parameters, the luminescence quantum efficiency values were also determined, the maximum efficiency being 89,2% for the transition from level 4I13=2 and 15,8% for level 4S3=2 The thermal diffusivity of the samples was determined by both thermal lens and thermal mirror measurements. The values obtained showed good agreement between the techniques and also with the literature. Another data obtained from these techniques was the fraction of absorbed energy that is converted into heat ( ). These showed close values and the same behavior for both techniques, being an indication that the results obtained are consistent. The behavior of for the doped samples is also in agreement with the luminescence results, showing a relevant increase in values for concentrations greater than 0,5 mol% of Er2O3.