Synthesis and characteristics of MgB2 bulks with different densities

Pure MgB2 bulks of different densities were synthesized by direct Mg-diffusion method. It is found that the connectivity was significantly improved since the current-carrying effective area was improved by the diffusion method, hence the self-field critical current density, Jc, was significantly improved comparing with conventional porous MgB2 bulks made by in situ method. A sample reacted at 850 °C for 10 h exhibited J c of 1.2 MA/cm2 at 20 K in self-field.