The synthesis and characterization of (Tl0.6Pb0.2Bi0.2) (Sr1.8Ba0.2)Ca2Cu3O9+x powder and Ag-sheathed tape

We have prepared a single-phase superconducting Tl-1223 powder with Tc above 110 K and used this promising material to produce Ag-sheathed tape. The powder was synthesized by partially substituting Pb and Bi for Tl, and substituting Sr for Ba in a stoichiometry (Tl0.6Pb0.2Bi0.2)(Sr1.8Ba0.2)Ca2Cu3O9+x suggested by Liu et al. The accelerated formation and stabilization of the Tl-1223 phase was observed. The non-agglomerated powder was found to have a homogeneous platelike morphology with average grain size 4.5 mu m and maximum grain size 18 mu m. The intragrain critical current density was determined to be 6.3*107 A cm-2 at 5 K, 1 T, and 6.5*104 A cm-2 at 77 K, 1 T. Ag-sheathed tapes were fabricated with this powder and magnetic and transport critical current densities of as-rolled tapes and heat-treated tapes were measured. A transport critical current density of 5.6*103 A cm-2 was obtained at 77 K, O T. The relationship between processing conditions, microstructure, and superconducting properties of the tape were also investigated.