Detalhes bibliográficos
Ano de defesa: |
2013 |
Autor(a) principal: |
Macambira, Francisco José |
Orientador(a): |
Souza, Dulcina Maria Pinatti Ferreira de
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Banca de defesa: |
Não Informado pela instituição |
Tipo de documento: |
Tese
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Tipo de acesso: |
Acesso aberto |
Idioma: |
por |
Instituição de defesa: |
Universidade Federal de São Carlos
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Programa de Pós-Graduação: |
Programa de Pós-Graduação em Ciência e Engenharia de Materiais - PPGCEM
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Departamento: |
Não Informado pela instituição
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País: |
BR
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Palavras-chave em Português: |
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Área do conhecimento CNPq: |
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Link de acesso: |
https://repositorio.ufscar.br/handle/20.500.14289/717
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Resumo: |
Yttrium-doped barium cerate perovskites are promising electrolyte for solid oxide fuel cell (SOFC) due to high proton conductivity at intermediate temperature, 400-600°C. However, the proton conductivity is not an intrinsic characteristic but appears after proton insertion on the crystalline structure during heat treatment in rich hydrogen atmosphere. The relationship between proton insertion efficiency and the type of microstructure is still unclear. Another limiting factors in obtaining these perovskites is the high sintering temperature which modifies the stoichiometry generating secondary phases. In this work, the influence of ZnO as sintering aid on the microstructure development and also the influence of microstructure on the protonation process was systematically investigated. Pure and doped with 10% to 20 at% yttrium BaCeO3, with and without ZnO as sintering aid were prepared through oxide mixture, isostatically pressed and sintered at 1300-1600°C temperature range. The sintered samples were characterized by density measurement using Archimedes principle, X-ray diffraction (XRD), scanning electron microscopy (SEM) equiped with energy-dispersive X-ray detector (EDS) and impedance spectroscopy. The sintered samples microstructures were multiphase and the volumetric relation between the phases was dependent on yttrium content, ZnO addition, and sintering conditions. ZnO acts on the microstructure development through the binary BaO-CeO2 eutectic point but it is only effective as sintering aid in the presence of yttrium. Eutectics microstructures were obtained due the ZnO addition. The protonation efficiency and, in consequence, the electrical conductivity were microstructure dependent. The highest protonic conductivity, 1,44 x 10-2S/cm at 500 °C, was obtaining by 10 at.% yttrium-doped sample with 1.0 wt% of ZnO and sintered at 1600°C-8h. |