Dresden 2011 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 6: Poster: Crystallography in Materials Science
KR 6.1: Poster
Mittwoch, 16. März 2011, 15:00–17:30, P1
Investigation of the Mosaicity of Real Crystals — •Anne Kathrin Hüsecken, Oleg Schmidt, and Ullrich Pietsch — Fakultät Physik, Universität Siegen, Walter-Flex-Str. 3, 57068 Siegen (Germany)
Extinction is the weakening of the diffracted X-ray intensity due to multiple scattering in the crystal. Perfect crystals scatter according to the dynamical theory, but no real crystal is perfect. Ideal imperfect crystals scatter according to the kinematical theory. In most cases, the measured intensities of real crystals are in between both cases and an extinction correction is needed to fulfil the kinematic approach. Most experimentalists use extinction as black box. Present theories dealing with extinction correction start with a finite perfect crystal, then go to an ideal mosaic crystal and at last generalize the theory to a real crystal. These approaches are based on a lot of approximations which are not verified by the experiment. Our approach is to verify the validity of one of the other present extinction theories by independent diffraction experiments with high resolution. The probe system used in the measurements was Li2SO4· H2O. The shape of each Bragg reflection was measured by ω- and ω-2θ-scans. From the FWHMs of these scans of X-ray reflections measured very precisely one can determine the size and the misorientation of the mosaic blocks and also the lattice strain. With these parameters one can experimentally derive the validity of approaches made by certain extinction theories.