The effect of different nanoscale material doping on the critical current properties of in situ processed MgB₂ tapes

Fe-sheathed MgB₂ tapes were prepared by the in situ powder-in-tube technique using nanometre Si/N/C, SiC whiskers and SiC as doping materials, respectively. The doping effect on phase composition, microstructure and critical current properties was investigated. Heat treatment was performed at 650 °C for 1 h under an argon gas atmosphere. All the doped tapes were found to have significantly enhanced critical current density J_C at 4.2 K in magnetic fields up to 14 T compared with their undoped counterparts. Moreover, the tapes doped with nano-SiC had the best pinning performance, while the SiC whiskers and Si/N/C powders showed a similar improved field dependence of J_C compared to undoped samples. At 4.2 K and 10 T, J_C for the nano-SiC doped samples increased by a factor of 32. Even for Si/N/C doped tapes, a 16-fold improvement in the magnetic field J_C was observed. It is inferred that the different chemical properties of the Si and C elements in SiC, SiC whiskers and Si/N/C led to the J_C-B difference.