The authors have fabricated a novel MgB2 superconducting wire using the in-situ powder-in-tube method with fine boron powder (0.25 μm) and coarse magnesium powder (150 μm). The core of the wire has a fibrous structure consisting of numerous discontinuous MgB2 filaments. The critical current density Jc increases as wire size decreases, and the Jc of a 1.00 mm wire is 1.4×104 A/cm2 at a temperature of 20 K in a magnetic field of 4 T.
Dense MgB2 bulk superconductors were prepared by a diffusion method in sealed stainless tubes, into which magnesium and boron powders were separately packed. After diffusion reaction at a temperature above 780°C for a long time, dense MgB2 bulks with densities of 2.35˜2.60 g cm-3 formed at the initially boron packed part. The critical current properties of the dense bulks were high, and the highest Jc was more than 0.8 MA cm-2 at 20 K in low magnetic fields. This value is almost threefold higher than that of conventionally processed MgB<