Análise da transição de fase normal-supercondutora dos compósitos [{Y,Gd}Ba2Cu3O7-]1-y-[PrBa2Cu3O7-]y e {[YBa2Cu3O7-]0,95-[PrBa2Cu3O7-]0,05}1-x-{Ag}x

• Ano de defesa: 2015
• Autor(a) principal: Monteiro, João Frederico Haas Leandro
• Orientador(a): Cruz, Gerson Kniphoff da
• Banca de defesa: Dias, Fábio Teixeira , Gomez, Rozane de Fátima Turchiello , Pereira, Luiz Américo Alves , Flemming Neto, Julio
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: UNIVERSIDADE ESTADUAL DE PONTA GROSSA
• Programa de Pós-Graduação: Programa de Pós-Graduação em Ciências
• Departamento: Fisica
• País: BR
• Palavras-chave em Português: compósito; YBCO; PBCO; expoente crítico
• Palavras-chave em Inglês: composite; YBCO; PBCO; critical exponent
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: http://tede2.uepg.br/jspui/handle/prefix/850

In this work we analyzed the superconductor-normal transition of the composites [YBa2Cu3O7-]1-y-[PrBa2Cu3O7-]y with 0<y<0,1, {[YBa2Cu3O7-]0,95-[PrBa2Cu3O7-]0,05}1-x-{Ag}x with 0<x<0,2 and [GdBa2Cu3O7-]0,95-[PrBa2Cu3O7-]0,05. All samples were prepared for solid state reaction method. The X-ray analysis demonstrated that the diffraction patterns are identical to that to YBa2Cu3O7-superconductor. The electrical resistivity measurements as a function of temperature demonstrated that praseodymium causes two major effects: splitting in 1 and 2 of the pairing transition and increasing of separation between them mainly affecting the peak in 2. The analysis of thermodynamic fluctuations have enabled critical and Gaussians exponents demonstrating that transitions at 1 and 2 are genuinely superconducting and not only the effect of granularity of the samples. However, the doping 20% of Ag in the composite [YBa2Cu3O7-0,95-[PrBa2Cu3O7-0,05 quenched the second transition, indicating that its appearance should be possibly related to a third phase given by Y1-yPryBa2Cu3O7- in nanometric scale in the region intergrain. Magnetic measurements confirm the temperature values for the superconductor-normal transitions obtained by electrical resistivity measurements. Furthermore, it was found that the praseodymium increases electric current density. The composite [GdBa2Cu3O7-]0,95-[PrBa2Cu3O7-]0,05 presented double transition differently of sample Gd1-yPryBa2Cu3O7- reported in other studies, showing that the preparation of samples in the form of composite may exhibit different properties.