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Publications: Articles

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Toutes :: 2007, 2008
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References

2008

Articles:

Morniroli, J. P., Houdellier, F., Roucau, C., Puiggali, J., Gesti, S. and Redjaïmia, A.
Ultramicroscopy, 108 (2)(2):100-115
2008
ISSN: 0304-3991

Resume: By combining the large-angle convergent-beam electron diffraction (LACBED) configuration together with a microscope equipped with a C., corrector it is possible to obtain good quality spot patterns in image mode and not in diffraction mode as it is usually the case. These patterns have two main advantages with respect to the conventional selected-area electron diffraction (SAED) or microdiffraction patterns. They display a much larger number of reflections and the diffracted intensity is the integrated intensity. These patterns have strong similarities with the electron precession patterns and they can be used for various applications like the identification of the possible space groups of a crystal from observations of the Lane zones or the ab-initio structure identifications. Since this is a defocused method, another important application concerns the analysis of electron beam-sensitive materials. Successful applications to polymers are given in the present paper to prove the validity of this method with regards to these materials. (c) 2007 Elsevier B.V. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

2007

Articles:

Morniroli, J. P., Redjaïmia, A. and Nicolopoulos, S.
Ultramicroscopy, 107(6-7):514-522
2007
ISSN: 0304-3991

Resume: In a previous study, it was reported that the possible space groups of a crystal can be identified at a microscopic or nanoscopic scale, thanks to microdiffraction patterns obtained with a nearly parallel electron incident beam focused on a very small area of the specimen. A systematic method was proposed, which consists of the observation of a few microdiffraction patterns displaying at least two Laue zones. These microdiffraction patterns can also be obtained by using an electron precession equipment. In this case, the patterns display a very large number of reflections in the Laue zones whose intensity is the integrated intensity. These original features greatly facilitate the space group identification method and are particularly useful when the high-order Laue zones (HOLZ) are not visible on microdiffraction patterns or when very thin specimens are not available. (c) 2006 Elsevier B.V. All rights reserved.

Equipe: Département SI2M : Microstructures et Contraintes

Morniroli, J.-P. and Redjaïmia, A.
Journal of microscopy, 227(2):157-171
2007
ISSN: 0022-2720

Resume: The 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 Lane 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 intensitv and this intensity can also be used to identify the Laue class.

Equipe: Département SI2M : Microstructures et Contraintes

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