Single-Crystal X-Ray and Magnetization Study of the 106 K Bi-Sr-Ca-Cu-O Superconductor

Single crystals of Bi2(Sr, Ca)4Cu3O x were studied by an X-ray precession camera together with the 232 and 221 phases. The 243 crystals were selected from two types of the specimens: (1) quenched from 810°C (T c=80 K) and (2) annealed subsequently at 500°C for 4 hours (T c=106 K). X-ray photographs revealed that the 243 phase has basically a 37 Å stacking unit along the c-axis with a remarkable stacking disorder. The direction of the modulation is not parallel to the b *-axis but inclined 35.7° from the b *-axis for the 243 phase. SQUID study revealed that the volume fraction of the 106 K phase at 50 K was about 57%.