Superconducting wires, fabricated by the powder-in-tube method, exhibited a transition temperature TC at 32.4K for the as-rolled wire as shown by dc-resistivity measurements. It was found that the TC was improved (37.3–38.4K) by subsequent Ar annealing treatment under various sintering temperatures and times. Remarkably, the annealed samples showed significant improvement in the overall quality of the samples. The best quality sample, with a JC of 470A/mm2 at 2.0T, was obtained by annealing at 1323K for 0.6ks. In order to find out the irreversible field, Birr, the technique of the Kramer plot was applied. The Birr obtained was 7.6 and 9.6T, for the as-rolled as well as the annealed samples at 1073K for 3.6ks, respectively. The mechanical properties were measured under tensile load. The yield stress was 450MPa for the as-rolled sample and decreased by annealing at 1323K for 0.6ks to 110MPa. After the wires were heat treated at temperatures between 1073 and 1323K and tensile-stressed up to their yield stress at room temperature. The critical current measurements were carried on such samples at 4.2K under applied magnetic fields of 2 and 5T. The stress level for the 95% tolerance of critical current was determined to be 97MPa.

Mechanical and Superconducting Properties of PIT-Processed MgB2 Wire after Heat Treatment. K.Yamamoto, K.Osamura, S.Balamurugan, T.Nakamura, T.Hoshino, I.Muta: Superconductor Science and Technology, 2003, 16, 1052-8