Estudo das propriedades estruturais e luminescentes dos compostos Gd3Al5O12 e (Y3–xGdx)Al5O12 dopados com európio produzidos pelo sol-gel modificado

• Ano de defesa: 2021
• Autor(a) principal: Carvalho, Iure da Silva
• Orientador(a): Rezende, Marcos Vinícius dos Santos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Programa de Pós-Graduação: Pós-Graduação em Física
• Palavras-chave em Português: Física; Aluminatos de terra rara garnet; Gadolínio; Agente quelante; Európio; Luminescência
• Palavras-chave em Inglês: Rare earth aluminate garnets; Gadolinium; Chelating agent; Europium; Luminescence
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://ri.ufs.br/jspui/handle/riufs/14720

The present work describes in detail the structural and luminescent properties of the compounds Gd3Al5O12 and (Y3-xGdx)Al5O12 doped with europium, which were synthesized by the modified sol gel method. To study the samples of Gd3Al5O12, the influence of different chelating agents (glucose, lactose and maltodextrin) on the formation of the phase under analysis was investigated, as well as on the emission of the dopant Eu3+. Structural characterization with XRD and Reitveld refinement showed that the composition of the crystal structure is strongly influenced by chelating agents and maltodextrin was the most suitable for obtaining the phase, both for the pure compound and for the doped one. The photoluminescence results complemented the structural data. Through the analysis of the excitation spectra, the existence of two symmetry sites for Eu3+ was verified, due to the presence of the GAP secondary phase. The emission spectra indicated typical emission lines for Eu3+ and for excitation at 230 nm (CTB: Eu1-GAG) and 395 nm (7F0->5L6) presenting the emission profile of the garnet phase. The XEOL emission results showed that at this excitation energy the spectra also adopt the characteristic Eu3+ emission in the GAG phase. In the study of samples of (Y3-xGdx)Al5O12 doped with Eu3+, structural changes and luminescent properties were determined as a function of the variation in the Gd3+ content in the compound. The samples were prepared by the sol-gel route, using polyvinyl alcohol (PVA) as a complexing agent. The prepared phosphors were characterized by X-ray diffraction (XRD) and Rietveld refinement was used to quantify the phases obtained. It was found that the higher concentration of Gd caused the appearance of the GAP secondary phase. However, for the Y1Gd2Al5O12 composition, the stable GAG phase was obtained. The effects of Gd concentration on luminescent properties under VUV and UV excitation were also studied, using synchrotron radiation as a light source. It was demonstrated that the increase in Gd content in relation to Y caused slight changes in the position of the Eu3+ emission lines, as well as an increase in luminescent intensity.