Development of Doped MgB₂ Wires and Tapes for Practical Applications

A review of current developments in the study of chemical doping effect on the superconducting properties of MgB2wires and tapes is presented, based on the known literature data and our own results. The critical current density of MgB2can be improved through various kinds of dopants. Among these dopants, doping with carbon-containing materials seems to be the most effective way to improve the Jcperformance. The doping effect of carbon in different forms and carbon-based compounds such as SiC, nano-C, metal carbides, as well as aromatic hydrocarbon and carbohydrate on the Jc-B characteristics of MgB2was discussed in detail. The C can be incorporated into the MgB2crystal lattice by replacing boron, and thus Bc2is significantly enhanced due to selective tuning of impurity scattering of the ¿ and ¿ bands in the two-band MgB2. Besides the efforts of increasing Bc2by carbon doping, the fine grain size and nano-size inclusions caused by doping would create many flux pinning centers improving the Jc-B property of MgB2. Based on these considerations, we suggested some principles for the selection of dopants.