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

摘要

We investigated the effect of SiC nano-particle doping on the crystal latticestructure, critical temperature T_c, critical current density J_c, and fluxpinning in MgB_2 superconductor. A series of MgB_{2-x}(SiC)_{x/2} samples withx = 0 to 1.0 were fabricated using in-situ reaction process. The contraction ofthe lattice and depression of T_c with increasing SiC doping level remainedrather small due to the counter-balanced effect of Si and C co-doping. The highlevel Si and C co-doping allowed the creation of intra-grain defects and highlydispersed nano-inclusions within the grains which can act as effective pinningcenters for vortices, improving J_c behavior as a function of the appliedmagnetic field. The enhanced pinning is mainly attributable to thesubstitution-induced defects and a local structure fluctuations within grains.A pinning mechanism is proposed to account for different contributions ofdifferent defects in MgB_{2-x}(SiC)_{x/2} superconductors.