Effect of nanoscale C and SiC doping on the superconducting properties of MgB₂ tapes

Nanoscale C and SiC doped MgB₂ tapes were prepared by the in situ powder-in-tube method. The samples were characterized using X-ray diffraction, scanning electron microscope, superconducting quantum interference device magnetometer etc. Transport J_c and its magnetic field dependence were evaluated by a standard four-probe technique. It is found that J_c for all the C and SiC doped tapes was significantly enhanced in magnetic fields up to 14 T compared to the undoped ones. For the 5 % C and SiC doped samples, at 4.2 K and 10 T, J_c increased by a factor of 32 and 26, respectively. The improvement of 7_c-B properties in C and SiC doped MgB₂ tapes is attributed to good grain linkage and the introduction of effective flux pining centers with the doping. Furthermore, our results clearly prove that the observed positive effects after mixing with SiC are nothing else than the result of the decomposition of this compound and substitution of carbon for B in MgB₂.