928 resultados para Sol-gel transition
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Ciência e Tecnologia de Materiais - FC
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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We report a systematic study on the influence of the synthesis routes on the structural and magnetic properties of polycrystalline PrxY1-xBa2Cu3O7-delta. We have prepared high-quality samples of this material by following a sol-gel method based on heat treatment in both inert argon and oxygen atmospheres in order to compare their effect on the formation of the superconducting phase using X-ray powder diffraction. Magnetic measurements (DC and AC susceptibility) clearly demonstrate that, for the same concentration of Pr, the superconducting transition temperature markedly increases in all samples prepared in argon atmosphere, including pure Pr-123. (C) 2012 Elsevier B.V. All rights reserved.
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Non-doped as well as titanium and lutetium doped zirconia (ZrO2) materials were synthesized via the sol-gel method and structurally characterized with X-ray powder diffraction. The addition of Ti in the zirconia lattice does not change the crystalline structure whilst the Lu doping introduces a small fraction of the tetragonal phase. The UV excitation results in a bright white-blue luminescence at ca. 500 nm for all the materials which emission could be assigned to the Ti3+ e(g) -> t(2g) transition. The persistent luminescence originates from the same Ti3+ center. The thermoluminescence data shows a well-defined though rather similar defect structures for all the zirconia materials. The kinetics of persistent luminescence was probed with the isothermal decay curve analyses which indicated significant retrapping. The short duration of persistent luminescence was attributed to the quasi-continuum distribution of the traps and to the possibility of shallow traps even below the room temperature. (C) 2012 Optical Society of America
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Thesis (Master's)--University of Washington, 2016-06