Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

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 J_c 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 J_c 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.