par Duvigneaud, Paul-Henri 
;Derie, René
Référence Journal of solid state chemistry, 34, 3, page (323-333)
Publication Publié, 1980
;Derie, René Référence Journal of solid state chemistry, 34, 3, page (323-333)
Publication Publié, 1980
Article révisé par les pairs
| Résumé : | Synthetic acicular hematite shows a nonuniform broadening of the X-ray lines in a wide temperature range. The factors affecting the peak broadening were studied by recording the powder line profiles of the (012), (104), (110), (024), and (116) reflections. The orientation relationships of these planes vs the main particle axes were previously checked by electron microdiffraction. On the other hand, various hematites having different particle sizes and shapes (spheres, slabs, needles) were investigated as well. The mean crystallite sizes were determined from a classical Fourier transform analysis whereas the size distributions were computed by a smoothing procedure described by A. Le Bail and D. Louër (J. Appl. Crystallogr.11, 50–55, 1978). The results show that the nonuniform broadening is ascribed to the shape anisotropy of the particles rather than to strains and faults broadening since (i) this last phenomenon is negligible in spherical-shaped particles, (ii) nonuniform broadening remains in acicular particles after further heating at 600°C, and (iii) a good estimate of the ratio of the particle width and thickness has been found. © 1980, All rights reserved. |
