Microstructure of the high Tc phase (Tc∼111 K) in the Sb‐Pb‐Bi‐Sr‐Ca‐Cu‐O system

The microstructure of the high Tc phase (Tc∼111 K) in the Sb‐Pb‐Bi‐Sr‐Ca‐Cu‐O system has been determined using transmission electron microscopy. Its crystal structure belongs to the superspace group NBbmb111, NBb2b111, PBbmb111 or PBb2b111 with subcell lattice parameters a=5.411(1) A, b=5.411(1) A, and c=37.22(6) A. The high Tc phase has a modulated structure with b‐axis wavelengths 26.9 and 36.1 A. Stacking faults along the c axis in the high Tc phase are much less numerous than in the Bi‐Sr‐Ca‐Cu‐O system, but comparable to the Pb‐Bi‐Sr‐Ca‐Cu‐O system. Sb substitution for Ca may affect the internal strain of the crystal.