High-transport critical current density above 30 K in pure Fe-clad MgB2 tape

Fe-clad MgB2 long tapes have been fabricated using a powder-in-tube techniq ue. An Mg + 2B mixture was used as the central conductor core and reacted i n situ to form MgB2. The tapes were sintered in pure Ar at 800 degreesC for 1 h at ambient pressure. SEM shows a highly dense core with a large grain size of 100 mum. The Fe-clad tape shows a sharp transition with transition width of DeltaT(c) of 0.2 K and a T-c0 of 37.5 K. We have achieved the high est transport critical current reported so far at 1.7 x 10(4) A/cm(2) for b oth 29.5 K in 1 T and 33 K in zero applied field. Resistivity temperature d ependence and transport critical current were also measured in magnetic fie lds applied perpendicular and parallel to the tape plane. Not only is the u se of an Fe sheath necessary for the successful processing of in situ react ed powder-in-tube MgB2, it confers on the finished wire the additional bene fit of magnetic screening. (C) 2001 Elsevier Science B.V. All rights reserv ed.