Estudo do composto supercondutor Hg, Re-1223 por difratometria de raios-X, com a aplicação do método de Rietveld / STUDY OF THE SUPERCONDUCTING COMPOUND Hg,Re-1223 BY X-RAY DIFFRACTION WITH APLICATION OF RIETVELD METHOD

AUTOR(ES)

Rodrigo Putvinskis

DATA DE PUBLICAÇÃO

2008

RESUMO

The objective of this work was to study the crystal structure of the superconductor compound of nominal composition Hg0,82Re0,18Ba2Ca2Cu3O8+ and general formula Hg,Re- 1223 and different oxygen contents, by the X-ray diffraction technique, by using the Rietveld method. The studied samples present different oxygen stoichiometry because during the synthesis process, had been heat treated under different oxygen/argon gas mixtures in the ratios: 5:95, 10:90 and 15:85. The results of structural refinement for the samples show that different oxygen contents imply in different cell parameters, atomic positions and distances for the main phase of each sample. The segregation of two superconducting phases with the same crystal structure, but slightly different cell parameters was confirmed for the studied samples both by Rietveld analysis and anomalous X-ray diffraction experiments. It was also confirmed that one of the segregated phases does not incorporate Re cations its composition. The main phase, who incorporates the Re cations, is here called Hg,Re-1223 and the Re-free secondary phase is called Hg- 1223. It was found that the superconducting phases present different crystallite sizes and the sample treated under gas flow composed of 10% oxygen and 90% argon presents the highest fraction of superconducting phases. From these results it was possible to conclude that the sample produced from the precursor compound treated under flow of O2/Ar gas at the ratio 10/90 presents the better results for the synthesis of this superconducting compound.

ASSUNTO(S)

difração de raios x método de rietveld supercondutores de alta tc supercondutores cerâmicos da alta tc difração de raios x métodos de rietveld

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