Regensburg 2004 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Tiefe Temperaturen
TT 31: Supraleitung: Vortexdynamik, Vortexphasen, Pinning
TT 31.10: Vortrag
Freitag, 12. März 2004, 12:30–12:45, H20
Enhanced Magnetic Flux Pinning of Nanocrystalline Mechanically Alloyed Bulk MgB2 by Stoichiometry Variation and Doping — •Olaf Perner1, Jürgen Eckert2, Günter Fuchs1, Konstantin Nenkov1, Bernhard Holzapfel1, and Ludwig Schultz1 — 1Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, PF 270116, D-01171 Dresden — 2TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt
In order to overcome the poor intrinsic properties of MgB2 concerning the low upper critical field and to obtain an enhancement of the magnetic flux pinning a combination of microstructure optimization as well as chemical variation of the pure MgB2 compound were chosen.
Starting from the elements Mg and B, the phase formation was realized by the mechanical alloying technique receiving a partially reacted MgB2 powder with grain sizes of about 10 nm. Short uniaxial hot pressing under vacuum led to phase pure highly densified nanocrystalline bulk samples with low impurity content. The variation of the stoichiometry by increasing and reducing the Mg content by up to 10 wt.% as well as the doping with various concentrations of SiO2 and MgO leads to increased pinning forces Fp compared to the stoichiometric composition.
The MgB2 bulk sample with a Mg excess of 10 wt.% shows an improved critical temperature Tc of 36.0 K and a critical current density jc of about 106 A/cm2 at 7.5 K in self field whereas Mg deficit of 10 wt.% enhances the upper critical field Hc2 (9 T at 20 K). Doping with SiO2 which improves significantly Hc2 and jc reveals more effective than with MgO. Microstructure investigations will be presented.