1990 Volume 25 Issue 3 Pages 184-190
Metal-sheathed tapes with Tl-(Ba/Sr)-Ca-Cu-O (TBSCCO) system were fabricated using the drawing-rolling method combined with a pressing process in order to improve the weak link properties. The Tc's of the tapes were measured to be 115±2K. The Jc was measured at various temperatures and in the presence of external magnetic fields. At 77K the Jc was 15, 900A/cm2 in the absence of magnetic field and slightly above 1, 000A/cm2 at 1T. The effect of magnetic field becomes much smaller at the lower temperature, for example at 20K the Jc was 8, 000A/cm2 at 1T. A tape fabricated by the drawing-rolling method without the post-pressing process gave the Jc of about 2, 000A/cm2 at 20K and 1T. An effect of the pressing is thought to be the densification of TBSCCO core. Another effect which could be thought is the orientation of TBSCCO crystals through the pressing process, although the orientation is not clear in the SEM observation. The relatively higher Jc is thought to be caused by an improved junction between grain boundaries and by an introduction of pinning center from various defects and unknown crystal phases. We believe that there exists flux pinning center in the TBSCCO system which is not yet identified.
