Superconductivity, critical current density, and flux pinning in MgB2-x(SiC)x/2 superconductor after SiC nanoparticle doping

We investigated the effect of SiC nanoparticle doping on the crystal lattice structure, critical temperature T-c, critical current density J(c), and flux pinning in MgB2 superconductor. A series of MgB2-x(SiC)(x/2) samples with x = 0-1.0 were fabricated using an in situ reaction process. The contraction of the lattice and depression of T-c with increasing SiC doping level remained rather small most likely due to the counterbalancing effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intragrain defects and highly dispersed nanoinclusions within the grains which can act as effective pinning centers for vortices, improving J(c) behavior as a function of the applied magnetic field. The enhanced pinning is mainly attributable to the substitution-induced defects and local structure fluctuations within grains. A pinning mechanism is proposed to account for different contributions of different defects in MgB2-x(SiC)(x/2) superconductors. (C) 2003 American Institute of Physics.