Microstructure of the high T c phase (T c∼111 K) in the Sb-Pb-Bi-Sr-Ca-Cu-O system

Abstract
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 NBbmb11̄1, NBb2b111, PBbmb11̄1 or PBb2b111 with subcell lattice parameters a=5.411(1) Å, b=5.411(1) Å, and c=37.22(6) Å. The high Tc phase has a modulated structure with b-axis wavelengths 26.9 and 36.1 Å. 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.