Selected Area Electron Diffraction and its Use in Structure Determination

2010 ◽  
Vol 18 (4) ◽  
pp. 22-28
Author(s):  
William F. Tivol
Keyword(s):  
Structural Analysis ◽  
Electron Diffraction ◽  
Structure Determination ◽  
Limited Region ◽  
Selected Area Electron Diffraction ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Technical Considerations

One of the capabilities of electron microscopes is to obtain diffraction patterns, which can be analyzed to give information about the structure of the specimen. This brief review discusses some of the technical considerations in using electron diffraction patterns for structural analysis. The technique of selected-area electron diffraction uses diffraction obtained from a limited region of the specimen.

scholarly journals Electron diffraction of tilted perovskites

2005 ◽  
Vol 61 (4) ◽  
pp. 387-399 ◽  
Author(s):  
David I. Woodward ◽  
Ian M. Reaney
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
Perovskite Structure ◽  
Selected Area Electron Diffraction ◽  
Diffraction Patterns

Simulations of electron diffraction patterns for each of the known perovskite tilt systems have been performed. The conditions for the appearance of superlattice reflections arising from rotations of the octahedra are modified to take into account the effects of different tilt systems for kinematical diffraction. The use of selected-area electron diffraction as a tool for perovskite structure determination is reviewed and examples are included.

A Structural Model for a Quasi-Crystalline Material Derived from TEM

1990 ◽  
Vol 48 (1) ◽  
pp. 48-49
Author(s):  
Jan-Olov Bovin ◽  
Osamu Terasaki ◽  
Jan-Olle Malm ◽  
Sven Lidin ◽  
Sten Andersson
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Structural Model ◽  
Image Intensifier ◽  
Crystalline Materials ◽  
Icosahedral Phases ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Quasi Crystals

High resolution transmission electron microscopy (HRTEM) is playing an important role in identifying the new icosahedral phases. The selected area diffraction patterns of quasi crystals, recorded with an aperture of the radius of many thousands of Ångströms, consist of dense arrays of well defined sharp spots with five fold dilatation symmetry which makes the interpretation of the diffraction process and the resulting images different from those invoked for usual crystals. The atomic structure of the quasi crystals is not established even if several models are proposed. The correct structure model must of course explain the electron diffraction patterns with 5-, 3- and 2-fold symmetry for the phases but it is also important that the HRTEM images of the alloys match the computer simulated images from the model. We have studied quasi crystals of the alloy Al65Cu20Fe15. The electron microscopes used to obtain high resolution electro micrographs and electron diffraction patterns (EDP) were a (S)TEM JEM-2000FX equipped with EDS and PEELS showing a structural resolution of 2.7 Å and a IVEM JEM-4000EX with a UHP40 high resolution pole piece operated at 400 kV and with a structural resolution of 1.6 Å. This microscope is used with a Gatan 622 TV system with an image intensifier, coupled to a YAG screen. It was found that the crystals of the quasi crystalline materials here investigated were more sensitive to beam damage using 400 kV as electron accelerating voltage than when using 200 kV. Low dose techniques were therefore applied to avoid damage of the structure.

scholarly journals Collecting large datasets of rotational electron diffraction with ParallEM and SerialEM

2020 ◽  
Author(s):  
Kiyofumi Takaba ◽  
Saori Maki-Yonekura ◽  
Koji Yonekura
Keyword(s):  
Electron Diffraction ◽  
Data Collection ◽  
Large Scale ◽  
General Purpose ◽  
Task Specialization ◽  
Camera Control ◽  
Combined Use ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Automated Protocol

AbstractA semi-automated protocol has been developed for rotational data collection of electron diffraction patterns by combined use of SerialEM and ParallEM, where SerialEM is used for positioning of sample crystals and ParallEM for rotational data collection. ParallEM calls standard camera control software through an AutoIt script, which adapts to software operational changes and to new GUI programs guiding other cameras. Development included periodic flashing and pausing of data collection during overnight or day-long recording with a cold field-emission beam. The protocol proved to be efficient and accurate in data collection of large-scale rotational series from two JEOL electron microscopes, a general-purpose JEM-2100 and a high-end CRYO ARM 300. Efficiency resulted from simpler steps and task specialization. It is possible to collect 12–20 rotational series from ∼ −68º to ∼ 68º at a rotation speed of 1º /s in one hour without human supervision.

scholarly journals Nano-Scale Rare Earth Distribution in Fly Ash Derived from the Combustion of the Fire Clay Coal, Kentucky

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 206 ◽  
Author(s):  
James Hower ◽  
Dali Qian ◽  
Nicolas Briot ◽  
Eduardo Santillan-Jimenez ◽  
Madison Hood ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Fly Ash ◽  
Electron Diffraction ◽  
Eastern Kentucky ◽  
Nano Scale ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Fire Clay

Fly ash from the combustion of eastern Kentucky Fire Clay coal in a southeastern United States pulverized-coal power plant was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). TEM combined with elemental analysis via energy dispersive X-ray spectroscopy (EDS) showed that rare earth elements (REE; specifically, La, Ce, Nd, Pr, and Sm) were distributed within glassy particles. In certain cases, the REE were accompanied by phosphorous, suggesting a monazite or similar mineral form. However, the electron diffraction patterns of apparent phosphate minerals were not definitive, and P-lean regions of the glass consisted of amorphous phases. Therefore, the distribution of the REE in the fly ash seemed to be in the form of TEM-visible nano-scale crystalline minerals, with additional distributions corresponding to overlapping ultra-fine minerals and even true atomic dispersion within the fly ash glass.

Electron diffraction from crystal defects: Fraunhofer effects from plane faults

1966 ◽  
Vol 293 (1433) ◽  
pp. 169-180 ◽  
Keyword(s):  
Electron Diffraction ◽  
Intensity Distribution ◽  
Stacking Faults ◽  
Dynamical Theory ◽  
Crystal Defects ◽  
Similar Calculation ◽  
Selected Area Electron Diffraction ◽  
Periodic Intensity ◽  
Diffraction Patterns ◽  
Calculated Intensity

The selected area electron diffraction patterns from a crystal containing a stacking fault have been observed to exhibit a number of unusual features. In some cases a periodic intensity distribution about the Bragg spot, in other cases streaking. By applying Kirchhoff’s theory of diffraction and using the dynamical theory of electron diffraction this intensity distribution around the Bragg spots in the electron diffraction patterns from stacking faults has been calculated. The calculated intensity distributions compare favourably with experiment. A similar calculation has also been carried out to predict the intensity distribution around Bragg spots in the selected area electron diffraction patterns from a crystal containing a grain boundary.

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