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The effect of the phase assemblage of the precursor powder on the properties of Ag/Bi-2223 tapes was investigated. The phase assemblage of the precursor powder was controlled by changing the calcination temperatures from 800 to or by adding 2223 seed particles to the precursor powder. The phase transformation kinetics, microstructure and transport properties of tapes were strongly dependent on the phase composition of precursor powder. The tapes fabricated from the powder calcined at lower temperatures (800 and ), which contained no 2223 phase and a relatively large amount of secondary phase, resulted in a microstructure with a larger grain size and a higher transport critical current. These tapes also appeared to have an appreciable incubation period in an isothermal annealing experiment with various soaking times. The phase transformation kinetics and microstructural development was pertinent to the nucleation and growth process for the mechanism of 2223 formation.

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The effect of adding fully reacted 2223 particles in the precursor powder on the final properties of Ag/Bi-2223 tapes has been investigated. Different amounts of fully reacted 2223 particles ranging from 0 to 10 wt% were added to the precursor powder consisting of mostly 2212 and calcium plumbate phases. The tapes seeded with 2223 particles showed a relatively high in a short annealing time without a mechanical deformation steps. The existence of 2223 particles in the precursor powder resulted in a smaller grain size and showed no appreciable incubation period and a faster transformation rate in an isothermal annealing experiment 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 for 2223 phase formation. For the tapes containing seed particles, the formation rate of 2223 phase was found to be controlled by the diffusion of material, while the formation of nuclei controlled the 2223 formation for the tape containing no seed particles.