An investigation was made of the effect of various impurity additions for MgB2 tapes fabricated by the in situ process of the powder-in-tube method. Silicides such as WSi2, ZrSi2, Mg2Si, SiO2 and SiC were essayed as impurities. These silicide powders were added to a powder mixture of MgH2 and B. The content of the additives was changed from 2.5 to 20at%. The powder mixture was stuffed into an Fe tube of 6.2mm outer diameter and cold-worked into a tape with 0.5mm thickness by the combination of grove rolling and flat rolling. Heat treatment was performed at a relatively low temperature (600C, 1h) under an Ar atmosphere. An XRD observation of each tape indicated that Mg2Si was formed, except for the WSi2-added tape. The TC of MgB2 was decreased by all silicide additions. Enhancement of JC was obtained for all of the additives; except SiO2. The addition of SiC increased JC and decreased the field dependence of JC. A JC value of 2.5 x 104A/cm2 at 4.2K and 10T was obtained for the MgH2+B powder mixture and SiC addition. The irreversibility field of the MgB2 tape was enhanced from 17 to 22T by the SiC addition. However, at low fields of about 4T, the JC enhancement by SiC addition seemed to be very small.

Effect of Impurity Additions on the Microstructures and Superconducting Properties of in situ Processed MgB2 Tapes. A.Matsumoto, H.Kumakura, H.Kitaguchi, H.Hatakeyama: Superconductor Science and Technology, 2004, 17, S319-23