Enhanced Magnetic Property of MgB Wire Using Phenol-Formaldehyde Resin

Abstract-We fabricated carbon (C)-doped MgB 2 wires using phenol-formaldehyde resin (PF) as a C source to improve their critical current density (J c ) in a magnetic field. In order to induce homogenous C doping, boron (B) powders were mixed with PF via liquid mixing technique and then the PF-treated B and Mg powders were mixed. The wires were fabricated by conventional powder-in-tube (PIT) process, followed by heat treatment through an in-situ reaction route. We observed that C was substituted for the B sites in the PF-doped MgB 2 and that the actual C content increased with increasing PF content. The doped MgB 2 wires exhibited lower critical transition temperature (T c ) and self-field J c , but superior H c2 value and better J c (B) performance than the undoped sample. The 3 wt% PF sample had the highest J c value of 7.77 × 10 3 A/cm , which is significantly higher than that of the undoped sample (0.29 × 10 3 A/cm 2 ) at 5 K and 6.4 T.