Superconducting properties of powder-in-tube MgB2 tapes prepared with fine powders

It is necessary to increase the Jc values to develop useful MgB₂ tape. We investigated superconducting properties of in situ processed Powder-In-Tube (PIT) MgB₂ 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∼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/mm² at 4.2K and 10 T. Furthermore we measured the upper critical field, B_c2, and the irreversibility field, B_irr, of the tapes. At 4.2K, the B_c2 and B_irr of the SiC-doped tape reached 24 T and 21.5 T, respectively. This B_irr was almost equal to the B_c2 of a conventional bronze-processed Nb₃Sn conductor. At 20 K, the extrapolated B_irr was around 9 T, which was comparable to the B_c2 of commercial NbTi at 4.2 K. These results indicate that MgB₂ tape is promising not only for the high-field applications but also for the applications at 20 K with a convenient cryocooler.