The doping effect of activated carbon on the superconducting properties of MgB2tapes

Activated carbon doped MgB 2 tapes were prepared by the in situ powder-in-tube method. The phase, crystal structure, microstructure, resistance, etc were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM) and a physical properties measurement system (PPMS). It was found that the irreversibility field ( H irr ) and upper critical field ( H c2 ) were enhanced when MgB 2 samples were doped with activated carbon, and the magnetic field dependence of the critical current density ( J c ) was improved significantly. For the 5% activated carbon doped MgB 2 tapes, the J c value was nearly eight times higher than that of undoped tapes at 13 T (4.2 K). On the other hand, the activated carbon doping level has a significant effect on the J c values of MgB 2 tapes. When the doping level is higher than 5%, the J c values decrease with increasing activated carbon doping level.