Síntese e caracterização do sistema ZnO - FeO submetido à moagem de alta energia

Detalhes bibliográficos
Ano de defesa: 2008
Autor(a) principal: Reisdoerfer, Eli Carlos
Orientador(a): Não Informado pela instituição
Banca de defesa: Não Informado pela instituição
Tipo de documento: Dissertação
Tipo de acesso: Acesso aberto
Idioma: por
Instituição de defesa: Universidade Estadual de Maringá
Brasil
Programa de Pós-Graduação em Física
UEM
Maringá, PR
Departamento de Física
Programa de Pós-Graduação: Não Informado pela instituição
Departamento: Não Informado pela instituição
País: Não Informado pela instituição
Palavras-chave em Português:
Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/2732
Resumo: The (1-X).ZnO + X.FeO system was ball-milled in a high-energy planetary mill, varying X throughout the concentration range (i.e., for 0 ≤ X ≤ 1). The as-milled powders were characterized by X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometry. Sintered pellets were also prepared for X ≤ 0.07, by further thermal annealing pressed milled samples, during 1h, at 1000 °C, in free atmosphere. These samples were additionally characterized by scanning electron microscopy and respectively to the electric transport properties. The results revealed that the high-energy milling induced, for every starting nominal concentration, an effective particle size reduction. For X ≤ 0.07, the asmilled samples showed the formation of a (Zn1-XFeX)O solid solution only, with a hexagonal compact structure. For 0.09 ≤ X ≤ 0.18, a saturation of the (Zn, Fe)O solid solution took place forming, additionally, the franklinite (ZnFe2O4). Three phases appeared for the X = 0.35 sample: ZnO, a (Fe, Zn)O solid solution and a Zn 1-δFe2-δO4 spinel-like phase. For the rest of the concentration range (i.e., 0.50 ≤ X ≤ 1) only the ZnO and (Fe, Zn)O phases were observed. All the as-milled samples presented magnetic hysteresis, which was attributed to contamination with metallic iron, originally present as impurity in the FeO precursor, or incorporated in the system by abrasion during the milling process; or, in the case of intermediary concentrations, also due to the Zn1-δFe2-δO4 spinel. The sintered samples revealed the segregation of the franklinite in a ZnO matrix, with a highly porous ceramic body and poor varistor behavior.