Sr1-xBaxSnO3 avaliação fotocatalítica de pós e filmes finos obtidos por PLD

• Ano de defesa: 2014
• Autor(a) principal: Sales, Herbet Bezerra
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal da Paraí­ba; BR; Química; Programa de Pós-Graduação em Química; UFPB
• Palavras-chave em Português: Estanato de bário; Estanato de estrôncio; Remazol amarelo ouro; Fotocatálise; Fotoluminescência; Barium stannate; Strontium stannate; Photocatalysis; Photoluminescence; Remazol yellow gold; Thin films; Descoloração; Filmes finos; Descoloration; CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: https://repositorio.ufpb.br/jspui/handle/tede/7161

Barium stannate (BaSnO3) and strontium stannate (SrSnO3) are perovskites type oxyde that have cubic (Pm3m) and orthorhombic (Pbnm) structures, respectively. These materials have received much attention due to their interesting physical and chemical characteristics, leading to a variety of technological applications. In this sense, these two materials were combined to each other in order to obtain powders and thin films of a solid solution, Sr1-xBaxSnO3, with (x = 0, 0.25, 0.50. 0.75 e 1). The solid solution in the of powder presented successive phase transitions ranging from orthorhombic and tetragonal structures to a cubic one with increasing of Ba2+ amount in the composition. These transitions were observed by X-ray diffraction and Rietveld refinement, and confirmed by raman vibrational spectroscopy. Moreover, the crystal structures were also characterized by infrared vibrational spectroscopy (FT-IR), scanning electron microscopy (SEM) and, vibrational spectroscopy. The different types of crystalline structures compositions of the solid solution had different percentage values against the photodiscoloration of the azo dye Remazol yellow gold -RNL. The results indicated that the direct mechanism is probably the most suitable for the cubic structure (BaSnO3), while the indirect gift for this orthorhombic structure (SrSnO3). Moreover, the thin films obtained from cubic system (BaSnO3) showed different growth associated with crystal structure of the substrate, the film composition and the deposition method used (deposition method by a pulsed laser ablation - PLD). The films deposited on amorphous silica and R-sapphire (Al2O3-012) showed polycrystalline growth while the films deposited on LAO (LaAlO3-100) showed an epitaxial growth (h00). In addition, morphological and photoluminescent properties also had suffered strong influence of the above parameters. Regarding the photoluminescent properties, these seem to be specifically related to the type of growth of the films, ie films deposited on LAO showed photoluminescent emission in the visible region a unlike the films occur due to deposited on silica and sapphire-R where a structural short-range order in the film / substrate interface has not led to photoluminescent emissions. Regarding the photocatalytic properties, the films obtained by PLD and with richer compositions Ba2+ were the most active in discoloration yellow gold remazol dye, reaching a maximum photocatalytic efficiency with polycrystalline film BaSnO3 deposited on R-sapphire 84.4 %. The polycrystalline films Sr1-xBaxSnO3 deposited on substrates amorphous silica and LAO also showed strong activity in discoloration of the dye, being more efficient than the polycrystalline epitaxial films. Keywords: Barium stannate, strontium stannate, PLD, photocatalysis, photoluminescence, remazol yellow gold, thin films, descoloration.