The high-temperature performance of monocore MgB2 powder-in-tube composite tapes was investigated. MgB2/stainless steel (SUS316) tapes were prepared by using an ex situ process. In situ processed MgB2/iron tapes were prepared by putting a mixture of MgH2 and amorphous B into Fe tubes and heating at 873K. The critical current and electrical resistance were measured in magnetic fields of 0 to 7T and/or at 4.2 to 40K by using a direct-current 4-probe method. Irreversible fields (Birr) were determined by using R–T curves. The Birr values of in situ processed tapes were higher than those of ex situ processed tapes over the whole temperature range. For example, Birr values of in situ and ex situ processed tapes were 2.5 and 0.5T at 30K, and 5.7 and 2.2T at 25K, respectively. Reflecting the better performance in Birr, the in situ processed tapes exhibited a higher JC performance than did the ex situ processed tapes. For example, the JC of 100A could be obtained for in situ tapes at 32K–0T, 25K–2T, 16K–5T and 6K–7T, while the JC of ex situ processed tape attained 100A at 19K–0T and 7K–2T. The JC of in situ processed tapes was less sensitive to temperature than was that of ex situ processed tapes.

High Temperature Performance of MgB2 Powder-in-Tube Composite Tapes. H.Kitaguchi, A.Matsumoto, H.Hatakeyama, H.Kumakura: Superconductor Science and Technology, 2004, 17, S486-9