The Mechanical Deformation Processing of High-Temperature Superconducting Composite Tape

Abstract

Since the discovery of ceramic high temperature superconductors, HTS [1–3], great efforts have been made in order to exploit the new superconductors in commercial applications. The HTS/metal composites, especially the BiSrCaCuO(BSCCO)/Ag composite, have been demonstrated to be a very promising candidate for large-scale applications. Values of the critical current density, J_c, over 60000 A/cm² have been reached at 77 K for short composite tapes [4, 5]. J_c values over 20000A/cm² have been reported for long length tapes over 1000 meter [6]. Most of the BSCCO/Ag composites are now made by the powder-intube, PIT, method. In brief: when the PIT method is applied, HTC precursor powder is filled into a pure Ag or Ag alloy tube, which is then mechanically deformed into thin composite wires or tapes. A thin tape is usually chosen as the final shape. The mechanical deformation process most often includes one or more of the following: extrusion, drawing, rolling and pressing. The as-deformed tapes need further annealing (sintering) in order to form the superconducting phase and texturise the material. A second mechanical deformation may be needed between several annealing steps to improve the superconducting properties of the composite further.