Dynamical X-Ray Diffraction at Decagonal Quasicrystals Observed by the Kossel Technique

Kossel experiments are carried out at decagonal phases of Al70Co15Ni15, Al72.5Co16.5Ni11, and Al62Co15Cu20Si3. In all cases the dynamical[light-dark]Kossel line contrast is observed. Moreover a characteristical change of the line profile, which depends on the emission depth as well as on the diffraction geometry, occurs. The fine structure of the Kossel lines is used for an estimation of the centric character of the decagonal phases. Furthermore it is shown that perpendicular to the directions of the Kossel cones puckered atomic layers exist, whose mean distances agree well with the measured d-values.