Phase evolution and critical current density during post-annealing in Bi-2223/AgAu tapes

37-filamentary Bi2Sr2Ca2Cu3O10+delta (Bi-2223) superconducting tapes were prepared by powder-in-tube (PIT) technique. During the second heat treatment process (HT2), tapes were sintered at 826 degrees C for different time and then cooled to 780 degrees C with different rate. The changes of sintering time and cooling rate obviously influenced liquid phase content after HT2. Therefore, (Pb, Bi)3Sr2Ca2CuOx (3221) phase content changed accordingly after post-annealing (PA). After PA, Jc of 50Q-PA (sintered at 826 degrees C for 50 h, quenched in air, then post-annealed at 780 degrees C for 36 h), 50SC-PA (sintered at 826 degrees C for 50 h, then cooled to 780 degrees C with cooling rate of 1 degrees C/h, post-annealed at 780 degrees C for 36 h) and 78SC-PA (sintered at 826 degrees C for 78 h, then cooled to 780 degrees C with cooling rate of 1 degrees C/h, post-annealed at 780 degrees C for 36 h) samples increased to 12.9 kA/cm2, 17.9 kA/cm2, and 18.5 kA/cm2, which were 1.81, 1.12, and 1.04 times of Ic of HT2 samples, respectively. Meanwhile, the change of intergrain connections and the flux pinning properties were investigated based on the in-field critical current, Jc-B measurement.