Abstract: In the X-ray powder diffraction patterns of hematite, formed by the dehydration of goethite, there are two markedly different groups of diffraction lines. One is comparatively sharp, whilst the other is rather diffuse. For the former, the line broadening effect is mainly dependent on the rearrangement of the oxygen Ions during phase change. For the latter, broadening of the line is related to the migration and rearrangement of the ferric ions. The present paper discusses in detail the βcosθ/λ~sinθ/λ curves of these two groups of diffraction lines, the mean crystallite size D, and the lattice deformation|(Δd)/d|.In the data treatment, two formulae are proposed to replace Jones' corrected curves for the facilitation of computerisation.
Furthermore, on the surface of the dehydration product at 250℃, S-shaped fractures are observed by the electron microscope. The origin of this phenomenon is discussed from the structural view of goethite.