The superconducting properties of MgB2/(stainless steel) tapes fabricated by the PIT process

We have investigated the superconducting properties of monofilament MgB2 tapes and wires with a stainless steel (SUS316) sheath. MgB2 powder was put into a SUS316 tube with a 6.5 min diameter; the tube was cold-rolled into a wire with a 1.4 mm-1.0 mm diameter using groove-rolling and cassette roller dies and then cold-rolled into tapes. The stainless steel sheath is effective to increase the density of the MgB2 core. The transport critical current density depends on the wire diameter and tape thickness. The J(C) values increase with increasing the total cross-sectional area reduction of tapes. However, the J(C) value of the tape with a thickness of less than 0.3 min deteriorated because of cracks introduced by rolling. Post-annealing increased the J(C) properties of these tapes. The low annealing temperature of similar to600 degreesC was effective to increase the J(C) values for MgB2/(stainless steel) tapes. This temperature was much lower than the optimum annealing temperature of MgB2 tapes with other sheath materials, such as MgB2/Fe tapes. The post-annealing improved the linkage of grains and enhanced the J(C) values.