Pure and SiC-added MgB2/Fe composite tapes were fabricated by using MgH2 starting powder and applying heat treatment (600 to 900C). For both pure and SiC-added tapes, the critical temperature increased with increasing heat-treatment temperature; due to the improved crystallinity of MgB2. The SiC additions decreased TC but increased the slope of the BC2–T and Birr–T curves, dBC2/dT and dBirr/dT, for all heat-treatment temperatures. The dBC2/dT and dBirr/dT of the pure tape decreased, with increasing heat-treatment temperature, from 600 to 700C; because of the longer coherence length associated with the improved crystallinity. However, the SiC additions significantly decreased the heat-treatment temperature dependences of dBC2/dT and dBirr/dT. At a temperature of ~20K, the Birr was governed by both the TC and dBirr/dT. The Birr of a pure tape at 20K decreased with increasing heat-treatment temperature from 600 to 700C, but the Birr of the 10mol%SiC-added tape increased with temperature. These behaviors could be explained by the heat-treatment temperature dependence of the TC and dBirr/dT. At 20K, the highest Birr of 10T was obtained under the conditions of a 10mol%SiC addition and heat-treatment temperature of 900C. This Birr at 20K was comparable to that of commercial Nb–Ti at 4.2K. The 10mol%SiC-added tape heat treated at 900C and the 5at%SiC-added tape heat treated at 800C exhibited JC (MgB2 core) values higher than 104A/cm2 at 20K in 5T.

Upper Critical Field, Irreversibility Field and Critical Current Density of Powder-in-Tube Processed MgB2/Fe Tapes. H.Kumakura, H.Kitaguchi, A.Matsumoto, H.Yamada: Superconductor Science and Technology, 2005, 18, 1042-6