Superconducting properties of powder-in-tube MgB/sub 2/ tapes prepared with fine powders

It is necessary to increase the Jc values to develop useful MgB/sub 2/ tape. We investigated superconducting properties of in situ processed Powder-In-Tube (PIT) MgB/sub 2/ tapes prepared with fine powders. Fine crystalline Mg powder with the average particle size of about 300 nm was fabricated by applying the thermal plasma method. In addition, 5/spl sim/15 mol% SiC powder doping was tried to enhance the Jc values. The transport Jc value of the 10 mol% SiC-doped tapes reached 250 A/mm/sup 2/ at 4.2K and 10 T. Furthermore we measured the upper critical field, B/sub c2/, and the irreversibility field, B/sub irr/, of the tapes. At 4.2K, the B/sub c2/ and B/sub irr/ of the SiC-doped tape reached 24 T and 21.5 T, respectively. This B/sub irr/ was almost equal to the B/sub c2/ of a conventional bronze-processed Nb/sub 3/Sn conductor. At 20 K, the extrapolated B/sub irr/ was around 9 T, which was comparable to the B/sub c2/ of commercial NbTi at 4.2 K. These results indicate that MgB/sub 2/ tape is promising not only for the high-field applications but also for the applications at 20 K with a convenient cryocooler.