Improvement of critical current density and microstructure of Tl-1223 tapes by a two-powder method

Superconducting tapes of (Tl,R)(Ba,Sr)/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ (R=Bi or Pb) were prepared using a mixture of pre-reacted single phase powder and unreacted precursor of identical or different stoichiometry. The effects of mechanical densification and sintering conditions on critical current (I/sub c/) and microstructure of the tapes were investigated. Compared to the tapes made with entirety unreacted powder or pre-reacted powder, the tapes made with a mixture of the two showed a much improved microstructure, an improved self-field I/sub c/ at 77K, as well as a smaller dependence on sintering conditions and better reproducibility of I/sub c/.