Síntese e caracterização de GdOCl:Eu3+ e Gd3O4Br:Eu3+ a partir da decomposição térmica de precursores lamelares para a aplicação como detectores de radiação ionizante
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Data
2023-02-28
Autores
Rodrigues, Eduardo Raphael
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Universidade Estadual Paulista (Unesp)
Resumo
Este trabalho apresenta a síntese, caracterização estrutural e espectroscópica de oxicloreto de gadolínio e tetraoxibrometo de gadolínio nominalmente puros e dopados com európio - GdOCl: Eu3+ (x%) e Gd3O4Br: Eu3+ (x%), onde x = 0, 0,5, 1, 2, 4, 8 em mols. Para obter esses materiais, precursores lamelares do tipo hidróxido de gadolínio, Gd(OH)3: Eu3+, foram preparados via síntese hidrotérmica. Posteriormente, os oxihaletos de gadolínio foram obtidos com sucesso por meio do tratamento térmico desses precursores a 900°C durante 4 horas na presença de sais de haleto de amônio e atmosfera de gás nitrogênio. A difração de raios X foi utilizada para confirmar a natureza lamelar dos precursores e as fases de interesse dos compostos sintetizados. A espectroscopia de fotoluminescência, a espectroscopia no infravermelho e a espectroscopia de reflectância difusa foram utilizadas para avaliar as propriedades ópticas dos compostos. As características estruturais dos compostos corroboram com a avaliação da intensidade das bandas de emissão referentes a transições intraconfiguracionais 5D0 → 7FJ, J = 0, 1, 2, 3, 4, como a presença de um centro de inversão e geometria antiprismática quadrática de Gd(OH)3, dois sítios de simetria em Gd3O4Br e a ausência de um centro de inversão em GdOCl. A banda de transferência de carga Gd3+ → Eu3+ também foi confirmada quando as excitações ocorreram no íon Gd3+. Usando a luminescência de excitação de raios X, observou-se que os materiais apresentaram um perfil espectral semelhante aos espectros dos compostos excitados por UV. A concentração otimizada de íons dopantes também foi determinada em relação ao efeito de supressão da luminescência.
This work presents the synthesis, structural, and spectroscopic characterization of gadolinium oxychloride and gadolinium tetraoxybromide, nominally pure and europium-doped materials - GdOCl:Eu3+ (x%) and Gd3O4Br:Eu3+ (x%), where x = 0, 0.5, 1, 2, 4, 8 in moles. To obtain these materials, lamellar precursors of gadolinium hydroxide type, i.e., Gd(OH)3:Eu3+, were prepared through hydrothermal synthesis. Subsequently, gadolinium oxyhalides were successfully obtained through the heat treatment of these precursors at 900°C for 4 hours in the presence of ammonium halide salts and nitrogen gas atmosphere. X-ray diffraction was used to confirm the lamellar nature of the precursors and the phases of interest of the synthesized compounds. Photoluminescence spectroscopy, infrared spectroscopy, and diffuse reflectance spectroscopy were used to evaluate the optical properties of the compounds. The compound’s structural characteristics corresponded to the evaluation of the emission bands' intensity regarding intraconfigurational transitions 5D0 → 7FJ, J = 0, 1, 2, 3, 4, such as the presence of an inversion center and quadratic antiprism geometry of Gd(OH)3, two symmetry sites on Gd3O4Br, and the absence of an inversion center on GdOCl. The Gd3+ → Eu3+ charge transfer band was also confirmed when excitations occurred on the Gd3+ ion. Using x-ray excited optical luminescence, it was observed that the materials showed a similar spectral profile to UV-excited spectra. The optimal concentration of dopant ions was also determined with regards to the luminescence quenching effect.
This work presents the synthesis, structural, and spectroscopic characterization of gadolinium oxychloride and gadolinium tetraoxybromide, nominally pure and europium-doped materials - GdOCl:Eu3+ (x%) and Gd3O4Br:Eu3+ (x%), where x = 0, 0.5, 1, 2, 4, 8 in moles. To obtain these materials, lamellar precursors of gadolinium hydroxide type, i.e., Gd(OH)3:Eu3+, were prepared through hydrothermal synthesis. Subsequently, gadolinium oxyhalides were successfully obtained through the heat treatment of these precursors at 900°C for 4 hours in the presence of ammonium halide salts and nitrogen gas atmosphere. X-ray diffraction was used to confirm the lamellar nature of the precursors and the phases of interest of the synthesized compounds. Photoluminescence spectroscopy, infrared spectroscopy, and diffuse reflectance spectroscopy were used to evaluate the optical properties of the compounds. The compound’s structural characteristics corresponded to the evaluation of the emission bands' intensity regarding intraconfigurational transitions 5D0 → 7FJ, J = 0, 1, 2, 3, 4, such as the presence of an inversion center and quadratic antiprism geometry of Gd(OH)3, two symmetry sites on Gd3O4Br, and the absence of an inversion center on GdOCl. The Gd3+ → Eu3+ charge transfer band was also confirmed when excitations occurred on the Gd3+ ion. Using x-ray excited optical luminescence, it was observed that the materials showed a similar spectral profile to UV-excited spectra. The optimal concentration of dopant ions was also determined with regards to the luminescence quenching effect.
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Palavras-chave
Luminescência, Cintiladores, Radiação Ionizante, Raio X, Európio