CRITICAL-CURRENT AND DEFECTS IN HIGH T(C) SUPERCONDUCTING MATERIALS

Several years after the discovery of superconductivity at high tempera ture in cuprates, the challenge remains to increase the critical curre nt density Jc of these materials, for industrial applications. The cre ation of columnar defects using heavy ions irradiation is presented; i t allows an important enhancement of the flux pinning especially chara cterized by the displacement of the irreversibility line (I.L.) toward s high temperature. The processing of textured ''YBCO'' ceramic, using a melt texture growth (MTG) method is also emphasized; one observes a spectacular increase of the transport critical current of such cerami cs to 71 000 A/cm2 at 77 K and zero field, with an excellent behaviour in a high field, i.e. 11 000 A/cm2 at 77 K under 20 Tesla.