Light carbon doping by oxygen-free paraffin wax to enhance the current density of MgB2 in the entire field regime

An oxygen-free hydrocarbon, paraffin wax, was evenly doped into MgB2 by a new method to enhance the electromagnetic properties. A 5 wt% paraffin addition resulted in significant enhancements of the upper critical field (Hc2), irreversible critical field (Hirr), and critical current density (Jc) properties in the entire field range at both 5 and 20 K. This excellent low-field and high-temperature Jc performance may be ascribed to the small carbon substitution, high critical temperature (Tc) and non-degraded grain coupling in the optimum paraffin-doped MgB2 sample.