Correlation between subgrains and coherently scattering domains

Abstract

Crystallite size determined by X-ray line profile analysis is often smaller than the grain or subgrain size obtained by transmission electron microscopy, especially when the material has been produced by plastic deformation. It is shown that besides differences in orientation between grains or subgrains, dipolar dislocation walls without differences in orientation also break down coherency of X-rays scattering. This means that the coherently scattering domain size provided by X-ray line profile analysis provides subgrain or cell size bounded by dislocation boundaries or dipolar walls.

Nanocrystalline materials studied by powder diffraction line profile analysis

“…The median and the variance of the crystallite size-distribution were obtained as: m ¼ 39 nm and s ¼ 0.14, respectively, providing the area weighted average crystallite size: hxi area ¼ (41 AE 3) nm. The average subgrain size determined by TEM was about (45 AE 5) nm, indicating that the X-ray size is equal to the subgrain size, as shown also by theoretical considerations in [83]. The average dislocation density was obtained to be 3 Á 10 15 m À2 by XLPA.…”

“…Crystallite size determined by XLPA is usually, either equal or smaller than determined by TEM [83]. In those cases when the crystallites or particles are delineated by well defined boundaries, as in the case of metallic samples produced by the method of inert gas condensation [57] or in the case of loose particles of ceramic materials [26,109,122,127] the X-ray and TEM data are in good correlation.…”

“…[69,80,81,128]. The arrangement of dislocations into small angle grain boundaries provide a simple and straightforward model for subgrain/cell structure where the TEM grain size is obviously larger than the X-ray subgrain/cell size, as shown schematically in [129] and [83]. The thorough Fig.…”

Enhanced energy product in Y-Co-Fe magnets intermediate between Nd-Fe-B and ferrite

“…The average grain size obtained from TEM is always greater than that deduced from XRD, which can be attributed to the plastic deformation of bulk metallic particles. 21,22 EDX analysis shows that the ratio of (Co þ Fe) to Y was 5.7, in fair agreement with the nominal composition of 5.0.…”

Influence of sintering temperature and pressure on crystallite size and lattice defect structure in nanocrystalline SiC

“…Moreover, dipolar dislocation walls may also cause the breakdown of coherency of x-ray scattering without misorientations inside a grain; i.e., in this case no contrast difference can be observed in a TEM image taken from that grain. 19 Unfortunately, although the TEM images confirm temperature and pressure dependence of crystallites sizes, they cannot identify the growth mechanism.…”