We report an effective carbon-containing additive, coronene (C 24 H 12 ), for MgB 2 superconducting wires. We used B powder coated with C 24 H 12 to fabricate MgB 2 wires using the powder-in-tube (PIT) and internal Mg diffusion (IMD) processes. The in-field critical current properties are strongly enhanced for both PIT-and IMD-processed MgB 2 wires. For PIT MgB 2 wires, a critical current density (J c ) value of 1.8 × 10 4 A cm −2 is obtained at 4.2 K and 10 T. For IMD MgB 2 wires, we obtained a J c of 1.07 × 10 5 A cm −2 and an engineering J c (J e ) of 1.12 × 10 4 A cm −2 at 4.2 K and 10 T. These J c and J e values are similar to the highest values reported for MgB 2 wires thus far. Furthermore, the irreversibility field, B irr , determined with a current density criterion of 100 A cm −2 , is strongly enhanced to 25 T at 4.2 K, which is also the highest value reported for MgB 2 superconducting wires thus far. Coronene is an active carbon source for MgB 2 superconducting wires because (1) coronene has a high carbon content (96 wt%) with a small amount of hydrogen (impurity), (2) the decomposition temperature for coronene is near the reaction temperature between Mg and B, and (3) uniform dispersion of coronene on the B surface can be obtained due to the melting point of coronene being lower than the decomposition temperature. Carbon substitution for B caused by the coronene active carbon source is mainly responsible for the high field critical current properties and the high B irr obtained in this work.
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