The microstructures and superconducting properties of MgB2 bulks prepared by a high-energy milling method

We succeeded in the synthesis of high-Jc MgB2 bulks via high energy ball-milling of elemental Mg and B powder at ambient temperatures. The mixed powder was ball-milled for 1-10 h and the completed reaction was achieved by subsequent annealing. The correlations among synthesis parameters, microstructures and superconducting properties in MgB2 bulks were investigated. Samples were characterized by X-ray diffraction and scanning electron microscope, and the magnetization properties were examined by a superconducting quantum interfere device magnetometer. The highest Jc, approximately 2.3 x 105 A/cm2 (15 K, 3 T), was obtained for samples milled for 5 h and sintered at 750 oC for 1 h. It is even comparable with SiC-doped MgB2 bulks made by Dou's group, which had exhibited the strongest reported flux pinning and the highest Jc in high field to date