Influência da composição e condições de preparo de vidros aluminosilicato de cálcio na formação de diferentes valências do európio e na transferência de energia entre érbio e itérbio

• Ano de defesa: 2015
• Autor(a) principal: Viana, José Renato Marques
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual de Maringá; Brasil; UEM; Maringá, PR; Programa de Pós-Graduação em Física
• Palavras-chave em Português: Vidro aluminosilicato de cálcio; Terras-raras; Európio; Érbio; Terras-raras-Itérbio; Materiais luminescentes; Luminescência; Ressonância paramagnética eletrônica; Raios X; Absorção de raios X; Brasil.; Calcium aluminosilicate glasses; Rare earth; Luminescent materials; Electron paramagnect ressonance; X-ray absorption; Brazil.; Ciências Exatas e da Terra; Física
• Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/2632

In this paper we investigated the influence of the manufacturing conditions and composition on the valence change of europium (Eu) and energy transfer in Erbium - Ytterbium (Er-Yb) co-doped calcium aluminosilicate glasses. Two series of samples with 2.5wt% of europium and different silica concentrations were prepared, in air and vacuum respectively. One co-doped 0,5wt%Er-5wt%Yb aluminosilicate samples serie was prepared in vacuum with different silica concentration. Luminescence, X-ray absorption (XANES) and Electron Paramagnetic Resonance (EPR) techniques were used to investigate europium doped samples. Besides, optical absorption spectroscopy, luminescence and fluorescence lifetime were carried out on Er-Yb co-doped system. The emission spectra of the europium doped samples prepared in vacuoum showed the coexistence of Eu2+ and Eu3+. We found an increase of the emission intensity attributed to Eu2+ and the displacement of the emission peak to shorter wavelengths with silica increasing. XANES and EPR results indicated that the ratio Eu2+/Eu3+ increase as silica is added to sample composition, which has been attributed to reduction of the non-bridging oxygens (NBO) in the glass. The EPR spectrum curves indicate change in Eu2+ symmetry and crystal field interaction intensity with amount of silica. The emission spectra of air europium prepared samples showed Eu3+ emissions. A broad absorption band around 350 nm assigned to Yb2+ was observed in the samples with higher amount of silica. The energy transfer efficiency process ytterbium to erbium increased about 20% as the amount of silica increase. The Luminescence and fluorescence lifetime results indicated that higher silica concentrations, above 35 wt%, there is a decrease of non-radiative multi-phonon relaxations suggesting energy trasnsfer back to Yb.