High J(c)'s in just-rolled Tl-1223/Ag tapes prepared using (Tl,Pb,Bi)-(Sr,Ba)-Ca-Cu-O compositions

The grain morphology, the changes in microstructure and J(c) during the the rmo-mechanical treatment, and the field dependence of J(c) in Tl-1223/Ag ta pes of Tl0.8Pb0.2Bi0.2Sr1.6Ba0.4Ca2Cu3Oz and Tl0.8Pb0.2Bi0.2Sr1.8Ba0.2Ca2.2 Cu3Oz compositions were investigated, and then compared with each other. As a result, high J(c)'s near 25,000 A/cm(2) at 77 K and 0 T were obtained in the latter composition, in which plate-like Tl-1223 grains are directional ly aligned, at least in local regions. The high J(c)'s are attributed to en hanced grain-contact areas resulting from enhanced densification by a repet ition of the TMT and the retarded decomposition of Tl-1223 phase in the lat ter composition. The strong field dependence of J(c) indicates, however, th at there still exist significant weak-links.