Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 1: Superconductivity - Fabrication, Technical Optimization and Characterization
TT 1.7: Vortrag
Freitag, 4. März 2005, 11:45–12:00, TU H104
Superconductivity in nanocrystalline mechanically alloyed MgB2 bulk samples and Fe sheathed multifilamentary tapes — •Olaf Perner1, Wolfgang Häßler1, Claus Fischer1, Marko Herrmann1, Günter Fuchs1, Konstantin Nenkov1, Bernhard Holzapfel1, Ludwig Schultz1, and Jürgen Eckert2 — 1Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, PF 270116, D-01171 Dresden — 2TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt
The application of the mechanical alloying (MA) technique for MgB2 powder preparation can be regarded as an optimal tool to obtain a nanocrystalline microstructure due to grain refinement as well as to control the exact stoichiometry of the MgB2 compound. Subsequently hot pressed bulk samples as well as by the powder-in-tube technique fabricated tapes show enhanced magnetic flux pinning in the superconducting state resulting in high critical current density Jc values.
In order to investigate the role of grain boundaries and impurities on superconductivity in MgB2 a series of bulk samples with different preparation parameters as well as impurity doping with oxides were characterized by transport and magnetization measurements as well as analytical transmission electron microscopy. The results will be described in detail and compared with the model of vortex dynamics.
The multifilamentary MgB2 tapes exhibit high values of the critical current density Jc of 35 kA/cm2 and 9 kA/cm2 in external magnetic fields of 7.5 T and 10 T, respectively, at 4.2 K due to a homogeneous, nanocrystalline microstructure and small sized impurities.