Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SIC doping

Doping of MgB2 by nano-SiC and its potential for the improvement of flux pinning were studied for MgB2-x(SiC)(x/2) with x=0, 0.2, and 0.3 and for 10 wt% nano-SiC-doped MgB2 samples. Cosubstitution of B by Si and C counterbalanced the effects of single-element doping, decreasing T-c by only 1.5 K, introducing intragrain pinning centers effective at high fields and temperatures, and significantly enhancing J(c) and H-irr. Compared to the undoped sample, J(c) for the 10 wt% doped sample increased by a factor of 32 at 5 K and 8 T, 42 at 20 K and 5 T, and 14 at 30 K and 2 T. At 20 K and 2 T, the J(c) for the doped sample was 2.4x10(5) A/cm(2), which is comparable to J(c) values for the best Ag/Bi-2223 tapes. At 20 K and 4 T, J(c) was twice as high as for the best MgB2 thin films and an order of magnitude higher than for the best Fe/MgB2 tapes. The magnetic J(c) is consistent. with the transport J(c) which remains at 20000 A/cm(2) even at 10 T and 5 K for the doped sample, an order of magnitude higher than the undoped one. Because of such high performance, it is anticipated that the future MgB2 conductors will be made using a formula of MgBxSiyCz instead of pure MgB2. (C) 2002 American Institute of Physics.