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

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We investigated the effect of SiC nano-particle doping on the crystal lattice structure, critical temperature Tc, critical current density Jc, and flux pinning in MgB₂ superconductor. A series of MgB₂₋ₓ(SiC)ₓ/₂ samples with x = 0 to 1.0 were fabricated using in-situ reaction process. The contraction of the lattice and depression of Tc with increasing SiC doping level remained rather small due to the counter-balanced effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intra-grain defects and highly dispersed nano-inclusions within the grains which can act as effective pinning centers for vortices, improving Jc behavior as a function of the applied magnetic field. The enhanced pinning is mainly attributable to the substitution-induced defects and a 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.