X-RAY AND ELECTRON-DIFFRACTION STUDY OF SINGLE-CRYSTAL BI2SR2CACU2OX

Using both x-ray and electron diffraction, we have studied the incommensurate modulation structure in single crystal Bi2Sr2Cacu2Ox. Electron diffraction clearly indicates a small a*-axis component of the modulation wave vector k, along with the more familiar b*-axis component (0.004a* + 0.212b*). This tilt of the k-vector breaks the mirror symmetry perpendicular to a- and b-axes as well as the twofold symmetry about a- and b-axes. The modulated structure thereby has only a mirror plane normal to the c-axis. Intense x-ray streaking along the c-axis at several satellite reflections was considerably more pronounced than at the fundamental reflections, indicating a stacking disorder along the c-axis predominantly in the modulated structure. © 1990, Materials Research Society. All rights reserved.