Electron precession microdiffraction as a useful tool for the identification of the space group

Abstract

SummaryThe possible space groups of a crystal can be identified from a few zone axis microdiffraction patterns provided the position (and not the intensity) of the reflections on the patterns is taken into account. The method is based on the observation of the shifts and the periodicity differences between the reflections located in the first-order Laue zone (FOLZ) with respect to the ones located in the zero-order Laue zone (ZOLZ).Electron precession microdiffraction patterns display more reflections in the ZOLZ and in the FOLZ than in the conventional microdiffraction patterns and this number increases with the precession angle. It is shown, from the TiAl example given in the present study, that this interesting feature brings a strong beneficial effect for the identification of the possible space groups since it becomes very easy to identify unambiguously the FOLZ/ZOLZ shifts and periodicity differences. In addition, the diffracted intensity on the precession patterns is the integrated intensity and this intensity can also be used to identify the Laue class.

Phase transformations and mechanical properties in heat treated superaustenitic stainless steels

“…These four identified secondary phases are s-phase, Laves phase, w-phase and the b-Cr 2 N nitride, with the volume fraction of the two former being significantly greater than the volume fraction of either w-phase or b-Cr 2 N nitride, in both steel grades. There are different modes of electron diffraction that can be used for their crystallographic characterization [21], namely Convergent Beam Electron Diffraction (CBED) [22], Large Angle Convergent Beam Electron Diffraction (LACBED) [23], Large Angle Convergent DIFfraction (LACDIF) [24], precession [25] or microdiffraction [26,27]. The microdiffraction, a routine technique, is better suited for the characterization of small precipitates resulting from the decomposition of the matrix.…”

Precession Electron Diffraction – a versatile tool for the characterization of Phase Change Materials

“…Like microdiffraction [7] and convergent beam techniques, intensities from zero order (ZOLZ) and higher order Laue zones (HOLZ) can be superimposed on the whole pattern [8,9]. As a consequence PED gives 3D structural information, e.g.…”

Automated nanocrystal orientation and phase mapping in the transmission electron microscope on the basis of precession electron diffraction

“…Ref. [14][15][16][32][33][34][35][36][37], and also suppresses Kikuchi lines and other crystal thickness related effects. Precession ED spot patterns possess an increased number of observable ED spots with respect to standard (stationary or zero-precession-angle) primary electron beam ED spot patterns.…”