Significantly enhanced critical current densities in MgB ₂ tapes made by a scaleable nanocarbon addition route

Nanocarbon-doped Fe-sheathed Mg B2 tapes with different doping levels were prepared by the in situ powder-in-tube method. Compared to the undoped tapes, Jc for all the C-doped samples was enhanced by more than an order of magnitude in magnetic fields above 9 T. At 4.2 K, the transport Jc for the 5 at. % doped tapes reached 1.85× 104 A cm2 at 10 T and 2.8× 103 A cm2 at 14 T, respectively. Moreover, the critical temperature for the doped tapes decreased slightly. Transmission electron microscopy showed a number of intragranular dislocations and the dispersed nanoparticles embedded within Mg B2 grains induced by the C doping. The mechanism for the enhancement of flux pinning is also discussed. These results indicate that powder-in-tube-processed Mg B2 tape is very promising for high-field applications.