Obtenção de matrizes de óxido de nióbio contendo íons Ln3+ (Ln3+= La, Tb e Eu) pelo processo sol gel

• Autor(a) principal: Sverzut, Lacyr João
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório do Centro Universitário Braz Cubas
• Texto Completo: https://repositorio.cruzeirodosul.edu.br/handle/123456789/392
• topic: Luminescência; Nióbia; Sol gel; Cromaticidade; CNPQ::CIENCIAS EXATAS E DA TERRA

The developed thesis aimed to obtain luminescent matrices based on niobium oxide doped with Ln3+ ions (La, Tb and Eu) by the adaptation of the non-hydrolytic Sol Gel process for the development of luminophores with applications in lighting or displays. The dual incorporation of ions (Tb3+ and Eu3+) into the Nb2O5:La3+ matrix had the purpose of developing efficient luminophores in the red, green and blue regions, providing thus emissions in the region of white. This work considered to analysis the structural and luminescent properties of the matrix containing different concentrations of Tb3+ and Eu3+ ions and treated at different temperatures. From the results obtained by the X-ray diffractometry, it could be noticed that the samples treated at 900 °C presented different structural phases indicating a greater crystallinity in relation to the samples treated at 550 °C. The photoluminescent properties were also influenced by the heat treatment and the different concentrations of the Ln3+ ions, being that the samples treated at higher temperatures presented a lower matrix emission band and narrowed bands attributed to the Tb3+ and Eu3+ ions. The addition of the Tb3+ ion in the Nb2O5:La3+ matrix provided the reduction of the matrix emission band (blue region) by the energy transfer from the matrix to the Tb3+ ion. This fact displaced the coordinates in the chromaticity diagram for the region of the green color, due to the intense band at 545 nm assigned to the 5D4→7F5 transition. These changes were also observed when the Eu3+ ion was added in the matrix, once the samples excited at the charge transfer band (265 nm) had a wide band in the blue region from the electronic transition from the 5b orbital of Nb5+ to the 2p orbital of O2-, and narrowed bands in the green region (545 nm, Tb3+ = 5D4→7F5 transition) and red region (613 nm, Eu3+ = 5D0→7F2 transition). In addition, the intensities of these transitions were directly influenced by the excitation wavelength, once the direct excitation in the Tb3+ (377 and 485 nm) and Eu3+ (394 and 465 nm) allowed obtain different emission's spectra and consequently different coordinates in the chromaticity diagram, resulting in blue, green, red and white colors.