Dislocation densities, arrangements and character from X-ray diffraction experiments

X-ray diffraction peak profile analysis has become a powerful tool during the last two decades for the characterisation of microstructure either in the bulk or in loose powder materials. The evaluation and modelling procedures have developed together with the experimental techniques. It will be shown that the different features of diffraction peak profiles such as (i) broadening, (ii) asymmetric peak shape, (iii) peak shifts and (iv) anisotropic broadening provide a variety of microstructural parameters by modelling crystallite size and strain. Modelling strain by assuming dislocations will be more extensive. Two different procedures will be considered: (1) evaluation by using characteristic parameters of individual peak profiles, especially the FWHM, the integral breadths and the Fourier coefficients and (2) multiple whole profile fitting (MWPF) procedure using ab initio size and strain functions scaled by the contrast factors of dislocations. The two procedures will be discussed and illustrated by different case studies. (C) 2001 Elsevier Science B.V. All rights reserved.