Enhanced Magnetic Property of MgB $_{2}$ Wire Using Phenol-Formaldehyde Resin

Abstract-We fabricated carbon (C)-doped MgB₂ 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 MgB₂ and that the actual C content increased with increasing PF content. The doped MgB₂ 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 ?? 10³ A/cm , which is significantly higher than that of the undoped sample (0.29 ?? 10³ A/cm²) at 5 K and 6.4 T.