Condensed-Matter Physics & Materials Science Seminar
"Development of Iron-chalcogenide Superconducting wires"
Presented by Toshinori Ozaki, National Institute for Materials Science, Japan
Thursday, May 31, 2012, 11:00 am — Bldg. 480 conference room
Since the discovery of superconductivity in iron-based superconductors, great efforts have been devoted to the preparation of films and wires for practical applications. Among these iron-based superconductors FeSe has several practical advantages over pnictides. FeSe has the simplest structure and less toxicity compared to the other As-based compounds. They also possess a high upper critical field Hc2 and extremely low Hc2 anisotropy. Furthermore, FeSe with Tczero ~8 K and Tconset ~10 K shows that the application of pressure leads to a significant enhancement of Tc up to 37 K under high pressure. These aspects make FeSe to be a more promising material for applications in high Jc superconducting wires. We succeeded in fabricating mono- and multi-core wires of FeSe using the Fe-diffusion powder-in-tube (PIT) method. The seven-core superconducting wires showed a transport Jc as high as 1027 A/cm2.1 What is more interesting is that the transition temperature Tczero was observed at 10.5 K, which is about 2 K higher than that of the bulk.1,2 These results indicate that the Fe-diffusion PIT method is highly suitable for fabricating FeSe superconducting wires.
Recently, a KxFe2-ySe2 superconductor with Tc 30 K was discovered. KxFe2-ySe2 could be a potential material for practical applications under high magnetic fields because of the high Hc2 and small anisotropy. However, the procedure for producing KxFe2-ySe2 single crystals is complicated and time-consuming. The simplification of the synthesis is crucial to fabricate superconducting wires. We have established a simple process that allows for the one-step synthesis of KxFe2-ySe2 single crystals, which exhibit high critical current density Jc.3 We will also report the details of the synthesis, transport properties and microstructures of the samples.
 T. Ozaki, et al, arXiv: 1103.3602, J. Appl. Phys (to be published)
 T. Ozaki, et al, J. Appl. Phys. 111, 013912 (2012)
 T. Ozaki, et al, Europhys. Lett
Hosted by: Qiang Li
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