Phase relationships and physical properties of Pb-doped and undoped 2212 superconductors

In the system Bi2O3-SrO-CaO-CuO the phase relations were determined to elucidate the solid solution range of the Bi2Sr2CaCu2O8 phase. For the 2212 phase two separate single-phase fields exist: (a) N phase: deficient in (Sr+Ca), orthorhombic, superconducting and (b) B phase: (Sr+Ca)~ stoichiometric, orthorhombic, not superconducting. Both phases occur in the same space group, Amaa or A2aa, but with different wave vector modulations: (a) N: a=5.393A, b=5.404A, c=30.781A, q=0.21b*. The solubility limit of Pb2+ for Bi3+ in the solid solution Bi2-mPbmSr2CaCu2O8+& with 0£ m£ 1 is reached at x=0.35± 0.03.