CRITICAL-CURRENT ANISOTROPY OF TL-1223 SUPERCONDUCTORS

A comparative study of the critical current anisotropy of Tl-1223 cond uctors manufactured by different techniques, prepared from different c ompositions and originating from different research laboratories is pr esented and discussed. For highly oriented layers, with the magnetic f ield (B) parallel to the ab plane, the normalised critical current den sity (j) versus magnetic field characteristic shows very little drop o f j value due to the intrinsic properties of the Tl-1223 phase, while all powder-in-tube conductors show a rapid drop of j value in fields a s low as 10 mT. For all powder-in-tube conductors the anisotropy coeff icient k shows a very pronounced minima at fields up to 30 mT followed by a monotonic decrease of anisotropy with increase of the magnetic f ield. This is due to poor grain alignment and a demagnetising effect i n the powder-in-tube Tl-1223 tapes.