Development of Polycrystalline Bulk MgB2 Superconducting Magnet by Hot-pressing

We have studied packing factor, microstructure, mechanical strength and trapped field of disk-shaped, polycrystalline bulk MgB2 samples with 20 mm in diameter prepared by hot-pressing with different applied pressures. The hot-pressed MgB2 bulk samples showed improved packing factor owing to shrinkage of the thickness by the uniaxial pressing. With an increase in packing factor, Vickers hardness increased from 470HV to 950HV and trapped field improved from 2.23 T to 3.39 T by the hot-pressing. Our results show that hot-pressing is one of the most effective techniques to extract superior trapped field performance of polycrystalline bulk MgB2 magnets through enhancing circulating supercurrent density and mechanical properties.