The performance improvement of MgB2 prepared by the Mg diffusion method with the MgB4 addition

The Mg diffusion method with the MgB4 addition is carried out to improve the MgB2 application performance. The precursor B powders and MgB4 powders are uniformly mixed as the ratio of (1- 4x) : x mol %, (x = 0, 1, 2, 5, 10 and 20). The mixed powders are pressed into bulks and the excess of Mg powders are added into the iron pipe. Then the heat treatment is carried out under the pure argon atmosphere. Finally, the high-quality MgB2 bulks are achieved with high density. The superconducting critical temperature of the MgB2 bulks decreases slightly with the increase of MgB4 addition content. However, the critical current density increases significantly at the high-fields. It is perhaps due to the small-sized MgB4 impurities in MgB2 bulk function as effective pinning centers and generates significant lattice distortion in the MgB2 lattice to yield improved J c performance in the applied field. It suggests that further improvement in the superconducting properties of the MgB2 added with the MgB4 will be possible via a better control of the composition and processing parameters. This also provides a reference for improving the preparation of MgB2 wire.