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 |
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Autor(a) principal: | |
Orientador(a): | |
Banca de defesa: | |
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 |
Programa de Pós-Graduação: |
Não Informado pela instituição
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Departamento: |
Não Informado pela instituição
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País: |
Não Informado pela instituição
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Palavras-chave em Português: | |
Link de acesso: | http://repositorio.uem.br:8080/jspui/handle/1/2632 |
Resumo: | 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. |