By doping the superconductor with SiC nano-particles, pinning sites were successfully introduced directly into the crystal lattice of grains (intra-grain pinning). It became possible due to a combination of counter-balanced Si, and C co-substitution for B; leading to a large number of intra-granular dislocations and dispersed nano-size impurities introduced by the substitution. The magnetic-field dependence of the critical current density was significantly improved over a wide temperature range, whereas the transition temperature in a sample of MgB2(SiC)0.34, the highest doping level prepared, dropped by only 2.6K.

Substitution-Induced Pinning in MgB2 Superconductor Doped with SiC Nano-Particles. S.X.Dou, A.V.Pan, S.Zhou, M.Ionescu, H.K.Liu, P.R.Munroe: Superconductor Science and Technology, 2002, 15, 1587-91