The effects of adding fully reacted Bi-2223 seed particles on the phase transformation and microstructure of Ag/Bi-2223 tapes

The effect of adding fully reacted (Bi,Pb)(2)Sr2Ca2, Cu3Oy (Bi-2223) partic les to the precursor powder on the final property of Ag/Bi-2223 tapes has b een investigated. Different amounts of fully reacted Bi-2223 particles rang ing from 0 to 10 wt% were added to the precursor powder consisting of mostl y Bi-2212 and calcium plumbate phases. The tapes seeded with Bi-2223 partic les showed a relatively high J(c) in a short annealing time without mechani cal deformation steps. The existence of Bi-2223 particles in the precursor powder resulted in a smaller grain size, showed no appreciable incubation p eriod and a faster transformation rate in an isothermal annealing experimen t compared to the tape containing no seed particles. A detailed analysis of the microstructure and phase transformation kinetics indicates that a two dimensional nucleation and growth process is the most plausible mechanism f or Bi-2223 phase formation. For the tapes containing seed particles, the fo rmation rate of Bi-2223 phase was found to be controlled by the diffusion o f material, while the formation of nuclei controlled the Bi-2223 formation for the tape containing no seed particles.