Effect of Nano-C Doping on the Critical Current Density and Flux Pinning of MgB2 Tapes

Nano-C doped Fe-sheathed MgB₂ tapes with different doping levels were fabricated using a powder-in-tube method and an in situ reaction. The effects of nano-C doping on the transition critical temperature, microstructure, critical current density, and flux pinning of MgB₂ tapes were studied. Compared to the un-doped tapes, critical current density J_c for all the C-doped samples with different doping level was enhanced by more than an order of magnitude in magnetic fields above 10 T. This result indicates that flux pinning was effectively enhanced by the nano-C doping. Highly dispersed nanoparticles and the substitutions of B by C are proposed to be responsible for the improvement of J_c -B properties.