Graphite-doped MgB2-xCx (x = 0.00, 0.05, 0.10) wires were fabricated via the in situ powder-in-tube method in flowing Ar by using low C-steel tubes as sheath materials. With increasing graphite concentration, the amount of unreacted graphite in the core area increased, and the average grain size of MgB2 decreased. It was found that the critical current density could be significantly improved by graphite doping. The MgB2 wire with x = 0.05 exhibited the best JC value of 16710A/cm2 at 6K, 4.5T, but MgB1.9C0.1 wire had the highest JC value of 2060A/cm2 at 6K, 8T. It was suggested that the enhancement of JC was due not only to improvement of the microstructure, but also to the introduction of pinning centers.

Enhancement of Critical Current Density in Graphite Doped MgB2 Wires. H.L.Xu, Y.Feng, Z.Xu, G.Yan, L.Z.Cao, X.G.Li: Chinese Physics Letters, 2004, 21, 2511-3