An investigation was made of the effect of starting powder on the microstructure and superconducting properties of tapes prepared by using a powder-in-tube technique. Two kinds of powder mixtures, Mg+B and MgH2+B, were used as precursors. When using the mixture of Mg+B, C-steel sheaths reacted with B, and FexB (x = 1 or 2) was formed. This brought about a decrease in the density of the MgB2 core and, hence, a low JC. On the other hand, it was found that the mixture of MgH2+B was effective in suppressing the formation of FexB and obtaining a high density of the core layer. The JC values of the tapes prepared using the mixture of MgH2+B were about twice as large as those prepared using the mixture of Mg+B and reached 1600A/cm2 at 4.2K and 10T. This was higher than that of the C-steel sheathed MgB2 tapes prepared using MgB2 powder.

Enhancement of Critical Current Densities of Powder-in-Tube Processed MgB2 Tapes by Using MgH2 as a Precursor Powder. H.Fujii, K.Togano, H.Kumakura: Superconductor Science and Technology, 2002, 15, 1571-6