CRITICAL-CURRENT ANISOTROPY OF TL-1223 SUPERCONDUCTORS

A comparative study of the critical current anisotropy in low magnetic fields of Tl-1223 conductors manufactured by different techniques, pr epared from different compositions and originating from different rese arch laboratories is presented and discussed. For highly oriented laye rs, with the magnetic field (B) parallel to the ab-plane, the normaliz ed critical current density (j) versus magnetic field characteristic s hows very little drop of j value due to the intrinsic properties of th e Tl-1223 phase, while all powder-in-tube conductors show a rapid drop of j value in fields as low as 10 mT. For all powder-in-tube conducto rs, the anisotropy coefficient shows a very pronounced minimum at fiel ds up to 30 mT, followed by a monotonic decrease of anisotropy with in crease of the magnetic field. This is due to poor grain alignment and a demagnetizing effect in the powder-in-tube Tl-1223 tapes. (C) 1997 P ublished by Elsevier Science Ltd.