Properties of Multifilamentary MgB2 Wires Fabricated by Internal Magnesium Diffusion Using Amorphous and Crystalline Boron Powders

MgB2/Nb/Monel multifilamentary wires were fabricated using amorphous and crystalline boron powders by an internal Mg diffusion (IMD) process. The microstructure, morphology, and the critical current density (Jc) of the reacted MgB2layers in the multifilamentary wires made using different boron powders were analyzed and compared. The purity of boron powder influences greatly the transport properties of MgB2wires. The Jcas high as 6.1 × 104A cm-2at 4.2 K, 10 T is obtained in the seven-core MgB2wire made using amorphous boron powder. The IMD-processed seven-core MgB2wire fabricated using high-purity crystalline boron powder has also a high Jcof 4.9 × 104A cm-2at 4.2 K and 10 T. However, the seven-core MgB2wire prepared using low-purity crystalline boron powder has a relatively low Jccompared with the others, which is expected to allow the fabrication of large-scale and low-cost superconducting wires for practical application. The further improvement of layer Jc, nonbarrier Jcand engineering critical current density Jeis necessary because of the irregular subfilaments and the inhomogeneous thickness of the reacted MgB2layer in multifilamentary wires.