Processamento, caracterização e estudo de fenômenos críticos do sistema supercondutor (Y - Er)Ba2Cu3O7

Detalhes bibliográficos
Ano de defesa: 2010
Autor(a) principal: Pinheiro, Lincoln Brum Leite Gusmão lattes
Orientador(a): Jurelo, Alcione Roberto lattes
Banca de defesa: Lepienski, Carlos Maurício lattes, Rodrigues Junior, Pedro lattes
Tipo de documento: Dissertação
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:
Palavras-chave em Inglês:
Área do conhecimento CNPq:
Link de acesso: http://tede2.uepg.br/jspui/handle/prefix/883
Resumo: The effect of Er substitution on the mechanical properties of ab and a(b)c planes of melt-textured Y Ba2Cu3O7 is reported in the present work. The samples were characterized by scanning electron microscopy, X-ray diffraction, resistivity measurements and mechanical properties by instrumented indentation and conventional Vickers measurement. The X-ray pattern and EDS analysis revealed the presence of Y-123, Y-211 and BaCeO3. Er substitution did not affect the superconducting properties. No difference in hardness was observed for the ab and a(b)c-plane. Elastic modulus of the a(b)c-plane was 10 % higher than of the ab-plane. Difference in indentation fracture toughness obtained by conventional Vickers indentation of the ab and a(b)c-planes was observed. The 5 % Er addition did not affect significantly the mechanical properties of melt-textured samples when compared with pure melt-textured Y Ba2Cu3O7. We have also studied fluctuations on the electrical conductivity in the samples. Two samples with different disorder states were studied. To identify power-law divergences of the conductivity, the results were analyzed in terms of the temperature derivative of the resistivity (d=dT ) and of the logarithmic temperature derivative of the conductivity (d(ln)=dT ). For sample with extreme granularity, we have observed for J k ab configuration a regime corresponding to the exponent u 1:6 0:1. For homogeneous sample, the fluctuations above the critical temperature are highly anisotropic: Gaussian regimes are observed for J ab configuration and critical regimes for J k ab configuration. Also, the data showed the occurrence of a two-stage transition, but it was not observed power-law behavior in the regime of near-zero resistance state.