Phase transformation characteristics of BSCCO tapes processed via cryogenic and room temperature pressing

Abstract

The current investigation studies the phase transformation process of Bi-Sr-Ca-Cu-O (BSCCO) tapes processed by cryogenic, 77 K and room temperature pressing. The work specifically examined the effect of deformation on the phase content and transformation kinetics of the BSCCO tapes. The results showed that cryogenic pressing produced tapes with a higher Bi2223 phase content at lower deformation ratios than room temperature pressed tapes. However, the phase transformation profiles for both tapes were similar. A minimum phase content was observed in the profiles that was characteristic to each process. The minimum occurred between 30-40% deformation for the cryogenically pressed tapes and between 50-60% for the room temperature pressed tapes. The peculiar profiles were suggested to be the result of two competing mechanisms that reduced the free energy of the systems. It was suggested that these two mechanisms were either Bi2212 re-crystallization or Bi2223 phase formation. The differences observed between the two processes were attributed to the amount and way in which the deformation energy was transferred to the tape.