Synthesis of highJcMgB₂bulks with high reproducibility by a modified powder-in-tube method

Systematic research on the improvement in J c of MgB 2 bulks by the optimization of sintering conditions was performed by applying a highly reproducible fabrication method. Compared with conventional methods, the fabrication method in the present study (powder-in-closed-tube, PICT) has quite a simple procedure: packing powders into the stainless tubes, pressing and sintering. The major merit of the fabrication method is complete suppression of Mg evaporation by uniaxial pressing of both ends of the metal tubes. Furthermore, resulting samples have the tape shape which is regarded as the short conductor with mono-core. Therefore, their critical current properties can be evaluated by the transport method as well as magnetic measurements. The undoped MgB 2 bulk synthesized with optimized sintering conditions, at 850 °C for 3 h, recorded a high J c of 3.9 × 10 5 A cm −2 at 20 K under self-field.