Development of Doped ${\rm MgB}_{2}$ Wires and Tapes for Practical Applications

A review of current developments in the study of chemical doping effect on the superconducting properties of MgB
₂
wires and tapes is presented, based on the known literature data and our own results. The critical current density of MgB
₂
can 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 J
_c
performance. 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 J
_c
-B characteristics of MgB
₂
was discussed in detail. The C can be incorporated into the MgB
₂
crystal lattice by replacing boron, and thus Bc
₂
is significantly enhanced due to selective tuning of impurity scattering of the ¿ and ¿ bands in the two-band MgB
₂
. Besides the efforts of increasing Bc
₂
by carbon doping, the fine grain size and nano-size inclusions caused by doping would create many flux pinning centers improving the J
_c
-B property of MgB
₂
. Based on these considerations, we suggested some principles for the selection of dopants.