Influence of the initial Bi2223 phase content on microstructure development in Bi2223/Ag tapes

(Bi,Pb)2Sr2Ca2Cu3O10 (Bi2223) Ag-sheathed tapes were produced from precursors containing various amounts of pre-reacted Bi2223 phase obtained by means of controlled calcinations of the starting powder mixture. The evolution of the critical current density during the first 20h of the first heat treatment follows closely that of the Bi2223 phase content. A maximum rate of increase is observed for precursor powders initially containing a small amount of Bi2223. The crystallinity of the Bi2223 phase along its c-axis improves with sintering time and is better in the tapes manufactured with precursor powders containing the largest amount of prereacted Bi2223. While the degree of preferential orientation of the Bi2223 phase at the Ag/ceramic core interface is not influenced by the initial Bi2223 phase content, the average texture in the ceramic core worsens with the increase of initial Bi2223 phase content. This effect is likely to play a role in the limited performance of Bi2223-rich precursors.