Possible phase separation in Pb-doped Bi-2223 superconductors

Upon annealing in N-2 at 730 degreesC, the resistivity of the Pb-doped Bi-2223 superconductors was initially increased, then slowly decreased. There exists a resistivity peak during the subsequent heat cycling. The relaxation process below and above the peak temperature is much different. In addition, many transition steps were observed in the ac susceptibility. Phase separation and phase transition can explain our results.