Fabrication and superconducting properties of powder-in-tube processed MgB2 tapes

The powder-in-tube process has been employed to fabricate long nickel-sheathed MgB2 superconducting tapes from reacted commercially available powders. We have found that reacted MgB2 powders reach a high degree of density inside the nickel sheath during the cold working procedure and, thanks to the large superconducting coherence length, a considerable current flow is therefore achievable even without sintering. At 4.2 K and self-field, a transport current density value j(c) of 10(5) A/cm(2) has been indeed reached over long portions of unsintered monofilamentary tapes. The irreversibility lines both for a magnetic field oriented parallel and perpendicular to the MgB2 superconducting tape have been determined by magneto resistance measurements, These data are consistent with a slight texturing process of the MgB2 grains occurring during the cold working procedure. (C) 2002 Elsevier Science B.V. All rights reserved.