Caracterização de vidros fluorofosfatos dopados com íons Eu3+

Abstract

In this dissertation, fluorophosphate glasses of the 25P75F and 75P25F series, having the compositions [80Ba (PO3)2 . 20Al (PO3)3]x [40BaF2 . 40SrF2 . (20-y) AlF3 . yEuF3]1-x (with x = 0.25 and x = 0.75), doped with y = 0.1, 0.5, 1, 2, 3, 4 and 5 wt% EuF3 were studied in order to verify their possible technological applications. Fluorophosphate glasses have been the subject of several spectroscopic investigations because of their potential as a matrix used in laser development. They are promising hosts because they can combine the advantages of fluoride and phosphate glasses, such as lower phonon energy, better moisture resistance, physical and chemical stability, lower nonlinear refractive index, and higher transparency in the spectral range from the ultraviolet to the mid-infrared. Here, characterizations by X-ray diffraction, Raman scattering, UV-Vis absorption spectroscopy and luminescence spectroscopy were performed. As results, we obtained that the integrated area of the absorption band referring to the 7F0→ 5L6 transition did not show an increase with increasing dopant ion concentration. The luminescence intensity in the 25P75F glasses decreased with increasing EuF3 concentration, but reached its maximum in the sample with 4 weight% EuF3, and then the intensity decreased for higher dopant concentrations. The optical and Urbach gap energies were determined for both series, and we obtained that the 25P75F glasses showed an increase in the indirect and direct gap values with the addition of EuF3, while the Urbach energy showed a small variation with a tendency to increase with the addition of EuF3. For the 75P25F glasses the indirect optical gap values increased with addition of EuF3, while the direct gap values showed oscillation without a clear trend of increase or decrease, and the Urbach energy decreased. Phonon sideband analysis for the 2Eu25P75F sample was performed and the values found for the phonon energies were assigned to the vibrational modes of the pyrophosphate (Q1) and orthophosphate (Q0) groups. The Judd-Ofelt parameters (Ω2 and Ω4) were obtained from the emission spectrum of the 25P75F glasses, and it was found that Ω2, Ω4 and the intensity ratio showed higher values for the 0.1Eu25P75F glass among the glasses studied here. When compared to other glasses, the 25P75F showed lower Ω2 values. The 5D0 → 7F4 transition of the 0.1Eu25P75F glass showed high value for branching rate, making it a potential candidate for the development of red-emitting lasers. In addition, the 25P75F glasses showed high values for quantum efficiency. Thus, based on the results obtained, the 25P75F glasses presented themselves as potential candidates to be used as red light emitters for WLEDs and display devices.