The effect of dislocation contrast on X-ray line profiles in untextured polycrystals

Anisotropic strain broadening in X-ray line profile analysis means that the width of diffraction profiles of Bragg reflections is not a monotonous fun ction of the diffraction angle. The lack of a physically sound model makes the interpretation of line broadening and the structure refinement procedur e of Rietveld often difficult or even impossible. A simple and straightforw ard procedure is presented for the rationalisation of anisotropic strain br oadening in terms of the anisotropic contrast effect of dislocations or dis location-like lattice defects. The procedure makes the evaluation of partic le size or coherent domain size, and the density and arrangement of disloca tions rather simple with a high precision, especially in the case of untext ured polycrystals or when dislocation population on the possible slip syste ms is uniform. Three illustrative examples of severely deformed microcrysta lline copper, the Rb3C60 f.c.c. fullerite and a ball-milled iron powder sho w the effectiveness of the procedure.