Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 15: Superconductivity: Poster Session
TT 15.2: Poster
Dienstag, 26. Februar 2008, 14:00–18:00, Poster B
Carbon doping as an effective way of changing the superconducting properties of MgB2 — •Marko Herrmann1, Wolfgang Häßler1, Margitta Schubert1, Wolfgang Gruner1, Manfred Ritschel1, Bernhard Holzapfel1,2, and Ludwig Schultz1,2 — 1IFW-Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden, Germany — 2Dresden University of Technology, Department of Physics, D-01062 Dresden, Germany
Up to now, carbon doping is the only reliable way to enhance the superconducting properties of MgB2 significantly. Precursor powders of carbon-doped and undoped MgB2 were prepared by mechanical alloying. This very effective preparation method imparts an enormous quantity of energy to the material and produces a partially reacted, nanocrystalline powder with enhanced reactivity. The high reactivity of the milled powders promotes the formation of MgB2 at reduced temperatures around 600∘C to 650∘C. Very high critical current densities of Jc = 1.1 x 106 A/cm2 in self-field at 4.2 K and critical fields Bc2 = 15.5 T at 10 K of undoped bulk samples of mechanically alloyed precursors were measured. In comparison to results of other in-situ preparation techniques this values exceed most of the superconducting properties by far and even keep up with results on optimized carbon doped samples reported so far. Starting from this high performance powders a comparison of promising carbon dopants will be presented. We show the influence of these dopants on the lattice parameter, the superconducting transition, critical field and critical current density of the bulk samples.