NSTI Nanotech 2009

Automated Crystal Orientation and Phase Mapping of Iron Oxide Nano-Crystals in a Transmission Electron Microscope

S. Rouvimov, E.F. Rauch, P. Moeck, S. Nicolopoulos
Portland State University, US

Keywords: nanocrystals, structure, automated mapping, precession, electron diffraction, TEM


An automated technique for the crystal phase and orientation mapping of polycrystalline materials in a TEM has recently beam developed. This technique is based on template matching of experimental electron diffraction spot patterns to their pre-calculated theoretical counterparts. Very promising results have so far been obtained with this technique for precipitates in heavily deformed austenitic stainless steels [1]. It has also been demonstrated that precession of the primary electron beam around the optical axis of the microscope during the recording of the diffraction patterns improves the reliability of this technique significantly. This is because more reflections are exited in precession electron diffraction spot patterns. For nanocrystal sizes of below about 50 nm, the intensities of these reflections are nearly kinematical [2]. Such precession electron diffraction patterns are, therefore, very useful for structural fingerprinting of nanocrystals in a TEM [3]. This paper illustrates the application of this technique to a mixture of iron oxide nano-crystals of magnetite and maghemite. [1] E. Rauch et al. Microscopy and Microanalysis, November 2008, (European Edition) [2] P. Moeck and S. Rouvimov, in: Nano Particle Drug Delivery Systems: II Formulation and Characterization, Informa Health Care, New York, 2009, in press [3] P. Moeck and P. Fraundorf, Zeit. Krist, 222, 634-645 (2007)
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