Jp. Morniroli et al., STUDY OF THE IRON-NITROGEN PHASES BY ELECTRON MICRODIFFRACTION AND CONVERGENT-BEAM ELECTRON-DIFFRACTION, Microscopy microanalysis microstructures, 4(6), 1993, pp. 575-594
It is shown how electron microdiffraction connected with convergent be
am electron diffraction can be used to identify unambiguously the spac
e group of the gamma, gamma' and epsilon iron nitrides. The method inv
olves the identification, from microdiffraction patterns, of a partial
extinction symbol in agreement with a few possible space groups. The
actual space group is then identified by means of the Tanaka ''multibe
am'' method or from observation of the intensity of the diffracted bea
ms on microdiffraction patterns. It is explained how to overcome the e
xperimental difficulties connected with the small crystal size, the te
xture of the specimen and the absence of HOLZ reflections on most diff
raction patterns.