Large transport critical currents in unsintered MgB2 superconducting tapes

The powder-in-tube process has been employed to fabricate tape-like conduct ors with a strong metallic sheath and based on the newly discovered MgB2 su perconducting phase. Long superconducting tapes have been prepared by packi ng reacted MgB2 powders inside pure Ag, Cu, and Ni tubes which are then col d worked by drawing and rolling. Such tapes have shown transport properties as good as bulk MgB2 samples sintered in high pressure and high temperatur e conditions. At 4.2 K, the highest critical current density of 10(5) A/cm( 2) has been achieved on nickel-sheathed single-filament conductors. A direc t correlation between the sheath tensile strength and the critical current of the unsintered tape has been observed. (C) 2001 American Institute of Ph ysics.