Estudo das propriedades luminescentes dos íons Eu²+ e Eu³+ incorporados em vidros aluminosilicatos de cálcio

• Autor(a) principal: Farias, Aline Milan
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/2620
• topic: Luminescência; Vidros aluminosilicatos de cálcio; Európio; Brasil.; Ciências Exatas e da Terra; Física

In this work we have studied the spectroscopic properties of calcium aluminosilicate glass at different compositions doped with europium and also doped with different concentrations of Eu2O3. We have prepared to sets of samples, in the first one the silica content was varied from 7 to 65 wt%, keeping the ratio CaO/Al2O3 constant and the amount of Eu2O3 at 2.5 wt%. For the second set, four different compositions of the calcium aluminosilicate glass were doped 0.1, 0.5, 1.0 and 2,5 wt% of Eu2O3. The samples were studied using spectroscopic techniques such as transmittance, luminescence, time resolved luminescence, excitation/emission contour plot and lifetime. The results showed that, with increasing of the silica content the absorption band assigned to the Eu2+ eg energy level shifts to lower wavelength, and the intensity of the luminescence band assigned to the Eu2+ increase substantially, suggesting an increment in the Eu2+/ Eu3+ ratio, and also this luminescence band shifts to lower wavelength. These behaviours were attributed to decrement of the glass optical basicity as the silica content increase, which affects the interaction between the glass matrix and the europium ions. The time resolved luminescence showed that the Eu2+ emission disappears after a few microseconds; however the Eu3+ emission disappears after a couple milliseconds. The Eu2+ luminescence lifetime is in the order of 1 us, increasing with the silica content. For the samples doped with different Eu2O3 concentrations, no shifts on the absorption band were observed. It was observed that the Eu3+ luminescence intensity increases monotonically with the increment of the ion concentration, however for the Eu2+ ion the luminescence intensity presents different behaviours for different excitations, for the excitation at 350 nm the luminescence intensity decreases with the increment of the Eu2O3 content and for the excitation at 465 nm first the luminescence intensity increases and then decreases. With the increment of the Eu2O3 content, it was observed a shift of the luminescence band to higher wavelength; this shift was attributed to the increment in the energy transfer process that occurs because of the electric dipole-dipole interaction between the Eu2+ ions. Our results shown that, these glasses are excellent candidates to tunable visible light even also white light generators