Showing papers by "Zhifeng Ren published in 1993"

Enhanced formation of 1223 phase by partial replacement of Bi for Tl in in-situ synthesized silver-sheathed superconducting tape of Tl1−xBixSr2−yCa2Cu3O9−δ

Abstract: The in-situ synthesis method has been used in fabricating silver-sheathed superconducting tape of Tl 1− x Bi x Sr 2− y Ba y Ca 2 Cu 3 O 9−δ . It was surprisingly found that the partial replacement of Bi for Tl greatly enhanced the formation of superconducting 1223 phase, as compared to the partially Pb replaced superconductor Tl 0.5 Pb 0.5 Sr 1.6 Ba 0.4 Ca 2 Cu 3 O 9−δ . The critical current densities of tapes with composition in the range of x=0.0-0.4 and y=0.0-2.0 have been determined by transport measurements. We found that the partial substitutions of both Tl by Bi and Sr by Ba can vary over a wide range without drastic reduction of the J c values, with the highest J c values obtained reproducibly at x =0.22 and y =0.4. A pellet of composition Tl 0.78 Bi 0.22 Sr 1.6 Ba 0.4 Ca 2 Cu 3 O 9−δ was found to consist of a single 1223 phase according to the XRD patterns. At 77 K and in the absence of an external magnetic field, the observed J c is 1.33×10 4 A/cm 2 for the rolled tapes and 2.1×10 4 A/cm 2 for the rolled and pressed tapes. In the presence of the external magnetic field, the transport J c was limited by weak links.