Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 20: SC: Fabrication and Characterization of Iron-Based and Other Superconductors
TT 20.7: Talk
Wednesday, March 24, 2010, 11:00–11:15, H19
How Can We Raise Tc in RO1−xFxFeAs Superconductors? — •Anke Köhler1,2, Günter Behr1, Marko Herrmann1, and Wolfgang Häßler1 — 1IFW Dresden, PF 270116, 01171 Dresden — 2Goethe-Universität Frankfurt am Main, Max-von-Laue-Str. 1, 60438 Frankfurt
By the discovery of RO1−xFxFeAs (R = lanthanide) superconductors in the beginning of 2008, it was shown for the first time that a non-cuprate superconductor can reach a superconducting transition temperature Tc above 50 K. This offers new opportunities for the development of new high temperature superconductors. However, the superconductors with the highest Tc show the most difficulties in formation of the right phase. Problems are the incorporation of fluorine and the homogeneity of the samples. A further challenge is the structural instability for rare earth elements with small ion radius (64≤Z≤71). In our studies, several opportunities to overcome these difficulties are evaluated:
1. variation of the grain size of the initial powder
2. use of slightly non-stoichiometric initial composition
3. high-pressure synthesis
As a result, we raise the Tc of the material with a nominal composition GdO1−xFxFeAs from 20 up to 40 K. In a SmO0.9F0.1FeAs-compound could be observed superconductivity above 50 K after a small As-reduction at the surface of the sample. Measurements of the final composition and structure will animate the discussion about the requirements for realization of the superconducting state.