Systematic research on the improvement in JC of bulk MgB2 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) involved quite a simple procedure: packing powders into the stainless tubes, pressing and sintering. The major merit of the fabrication method was complete suppression of Mg evaporation by uniaxial pressing of both ends of the metal tubes. Furthermore, the resultant samples had a tape shape which was regarded as being a short conductor with mono-core. Therefore, their critical current properties could be evaluated by using the transport method as well as magnetic measurements. The undoped MgB2 bulk synthesized with optimized sintering conditions (850C, 3h), recorded a high JC of 3.9 x 105A/cm2 at 20K in self-field.

Synthesis of High JC MgB2 Bulks with High Reproducibility by a Modified Powder-in-Tube Method. A.Yamamoto, J.Shimoyama, S.Ueda, Y.Katsura, S.Horii, K.Kishio: Superconductor Science and Technology, 2004, 17, 921-5