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

Abstract

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.

The effect of nanoscale Fe doping on the superconducting properties of MgB2

“…This is a typical characteristic for HTS in which weak links are the dominating factor for current flow. We do not have this weak link characteristics even at higher doping levels for non-magnetic dopants [16]. 20%SiC addition to MgB 2 not only showed no such weak link feature but had a strong enhancement effect on J c (H) [17].…”

“…Kuzmann et al [3] and Guo et al [16] suggested possible Fe substitution in the Mg site in the MgB 2 lattice [3]. Because these techniques were applied to an entire sample the claim of Fe substitution for Mg was inconclusive.…”

The effect of doping level and sintering temperature on Jc(H) performance in nano-SiC doped and pure MgB2 wires

“…The authors' group found that doping of MgB 2 with nanoparticle SiC can significantly enhance J c in high fields, with only slight reductions in T c up to a doping level as high as 30% of B. 10 Compared to the undoped sample, the J c for the 10 wt % SiC doped sample increased by more than an order of magnitude at all temperatures and in the high field region. The exceptional properties of SiC as a dopant have been verified by a number of groups over the past few years.…”

Transport and magnetic Jc of MgB2 strands and small helical coils

“…This might be expected since the primary role of SiC is to increase the H irr and H c2 . Nevertheless some increases in pinning have also been seen [14][15][16][17] , but not in the present case at higher temperatures and lower fields.. …”

“…An anisotropy factor of about 1. 4 12,13,14 have studied the effects of nano-Si doping 14 , nano-carbon doping 15 , and carbon nanotube doping 16,17 on the properties of MgB 2 strands. Glowacki 18,19 has also been pursuing PIT MgB 2 , with useful demonstrations particularly with regard to cables and shielding.…”