Study of the superconductivity of the 132 K Sb-doped Bi-system oxide superconductor

According to powder X-ray diffraction analyses and electron diffraction for the 132 K Sb-doped Bi-system oxide superconductor it can be found that a new phase exists in this system; the new phase belongs to the monoclinic system with cell dimensions a=22.10 AA, b=5.90 AA, c=19.91 AA and beta =99.6 degrees and is not superconducting itself. Furthermore, there exists intergrowth between the monoclinic phase and 2:2:2:3 (=Bi:Sr:Ca:Cu) phase, and for this reason crystals of the 2:2:2:3 phase are distorted. The superconductivity at 132 K may be caused by the distorted 2:2:2:3 phase. After thermal cycles, this kind of intergrowth phenomenon disappears so that only superconductivity at 110 K occurs as usual. All this can explain why the 132 K phase is not stable. In addition, how and why the measurement current influences T_c is also discussed.