Fabrication of MgB/sub 2/ tapes sheathed with carbon steels by ex situ and in situ methods

MgB/sub 2/ tapes sheathed with carbon steel (CS) were fabricated by a powder-in-tube technique with ex situ and in situ methods. The critical current density (J/sub c/) value of the former tape was about 2 kA/cm/sup 2/ at 4.2 K and 10 T by heat treatment at 900/spl deg/C, whereas the J/sub c/ value of the latter tape reached about 3 kA/cm/sup 2/ by heat treatment at temperature as low as 600/spl deg/C. The J/sub c/ anisotropy with respect to field direction of the tapes fabricated by the ex situ method was much larger than that of the tapes fabricated by the in situ method.