X-ray diffraction analysis of twin walls in ferroelastic YBA2CU3O7

The thickness and wall profiles of twin boundaries are analysed using a novel 7-circle diffractometer. The diffractometer allows the rapid measurement of rocking curves with angular resolution of 0.001° for two orthogonal rocking angles and for the detector position. Position sensitive detectors can be rotated independently around two orthogonal axes, the sample can be rotated around 3 orthogonal axes and translated in two perpendicular directions. Measurements on twinned crystals of YBa2Cu3O7 showed that the thickness of twin walls is ca 7Å. Routine investigations on magnetically aligned ceramics allow a full characterization of the angular spread within some 30 minutes. Quantitative diffraction profiles were obtained for ferroelastic materials with tweed microstructures.