scholarly journals New Features in Crystal Orientation and Phase Mapping for Transmission Electron Microscopy

Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1675
Author(s):  
Edgar F. Rauch ◽  
Patrick Harrison ◽  
Muriel Véron
Keyword(s):  
Electron Diffraction ◽  
Angular Resolution ◽  
X Ray ◽  
Amorphous Phases ◽  
Transmission Electron ◽  
Tremendous Amount ◽  
Processing Algorithms ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Scanning Electron Microscopes

ACOM/TEM is an automated electron diffraction pattern indexing tool that enables the structure, phase and crystallographic orientation of materials to be routinely determined. The software package, which is part of ACOM/TEM, has substantially evolved over the last fifteen years and has pioneered numerous additional functions with the constant objective of improving its capabilities to make the tremendous amount of information contained in the diffraction patterns easily available to the user. Initially devoted to the analysis of local crystallographic texture, and as an alternative to both X-ray pole figure measurement and EBSD accessories for scanning electron microscopes, it has rapidly proven itself effective to distinguish multiple different phases contained within a given sample, including amorphous phases. Different strategies were developed to bypass the inherent limitations of transmission electron diffraction patterns, such as 180° ambiguities or the complexity of patterns produced from overlapping grains. Post processing algorithms have also been developed to improve the angular resolution and to increase the computing rate. The present paper aims to review some of these facilities. On-going works on 3D reconstruction are also introduced.

Characterization of small inclusions: SEM vs TEM, or is it even worth considering Sem?

1996 ◽  
Vol 54 ◽  
pp. 498-499
Author(s):  
Carl Blais ◽  
Gilles L’Espérance ◽  
Éric Baril ◽  
Clément Forget
Keyword(s):  
Chemical Composition ◽  
X Rays ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Micro Alloyed Steel ◽  
Steel Welds ◽  
Scanning Electron Microscopes

Inclusions of technological importance are often in the size range from 0.1 to 1 μm, These inclusions are generally too thick for EEL-spectrometry and require the use of EDS to characterize their chemical composition. Recent Monte Carlo simulations indicated that scanning electron microscopes (SEM’s) equiped with a field emission gun (FEG) might challenge transmission electron microscopes (TEM’s) for the charaterization of small inclusions, In the light of these results, we investigated the possibility of using a FEGSEM to characterize inclusions found in micro-alloyed steel welds used for arctic applications. The main setbacks of using EDS for such a task are due to the presence of small phases of unknown thicknesses, non-homogeneity of the X-ray generation volumes, variation in absorption along the path length of the X-rays, etc., Even though these problems are encoutered in both the SEM and the TEM, the relative ease of imaging the very small inclusions in TEM confers a definite advantage to this technique. Furthermore, TEM allows to obtain convergent-bearn electron diffraction patterns (CBED) which complement the chemical composition characterization, thereby allowing the unambiguous identification of the phases present (chemistry and crystal structure).

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 Precession Electron Diffraction Assisted Orientation Mapping in the Transmission Electron Microscope

2010 ◽  
Vol 644 ◽  
pp. 1-7 ◽  
Author(s):  
Joaquim Portillo ◽  
Edgar F. Rauch ◽  
Stavros Nicolopoulos ◽  
Mauro Gemmi ◽  
Daniel Bultreys
Keyword(s):  
Electron Diffraction ◽  
X Ray Diffraction ◽  
Promising Technique ◽  
Electron Backscattered Diffraction ◽  
Transmission Electron ◽  
Orientation Mapping ◽  
Precession Electron Diffraction ◽  
Electron Microscopes ◽  
Ebsd Technique ◽  
Scanning Electron Microscopes

Precession electron diffraction (PED) is a new promising technique for electron diffraction pattern collection under quasi-kinematical conditions (as in X-ray Diffraction), which enables “ab-initio” solving of crystalline structures of nanocrystals. The PED technique may be used in TEM instruments of voltages 100 to 400 kV and is an effective upgrade of the TEM instrument to a true electron diffractometer. The PED technique, when combined with fast electron diffraction acquisition and pattern matching software techniques, may also be used for the high magnification ultra-fast mapping of variable crystal orientations and phases, similarly to what is achieved with the Electron Backscattered Diffraction (EBSD) technique in Scanning Electron Microscopes (SEM) at lower magnifications and longer acquisition times.

Energy Filtered Imaging and Convergent Beam Electron Diffraction (CBED) in the Transmission Electron Microscope (TEM)

1997 ◽  
Vol 3 (S2) ◽  
pp. 973-974
Author(s):  
A.G. Fox ◽  
E.S.K. Menon ◽  
M. Saunders
Keyword(s):  
Electron Diffraction ◽  
Form Factors ◽  
Zone Axis ◽  
X Ray ◽  
Elemental Imaging ◽  
Energy Filtering ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Single Objective

Over the last ten years TEMs have been developed that are capable of HREM, EDX, PEELS and diffraction using a single objective pole piece. More recently these TEMs have been equipped with the capability of energy filtering the electron beam after it has passed through the sample so that energy filtered images and electron diffraction patterns can be obtained. In this work the use of a Topcon 002B TEM equipped with a GATAN PEELS imaging filter (GIF) to generate zero-loss energy filtered zone axis CBED patterns and elemental images from inelastically scattered electrons will be described. An analysis of this energy filtered data indicates that elemental imaging using the GIF is an informative, but semiquantitative technique, whereas zero-loss energy filtered zone axis CBED patterns can be accurately quantified so that the two lowest-angle x-ray form factors of cubic elements can be measured with errors of the order of 0.1% or less.

New Applications of Electron Diffraction in the Pharmaceutical Industry: Polymorph Determination by Using a Combination of Electron Diffraction and Synchrotron X-ray Powder Diffraction Techniques

2002 ◽  
Vol 8 (2) ◽  
pp. 134-138 ◽  
Author(s):  
Z.G. Li ◽  
R.L. Harlow ◽  
C.M. Foris ◽  
H. Li ◽  
P. Ma ◽  
...  
Keyword(s):  
Pharmaceutical Industry ◽  
Electron Diffraction ◽  
Powder Diffraction ◽  
Unit Cell ◽  
X Ray ◽  
Cell Parameters ◽  
Synchrotron Powder Diffraction ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
New Applications

Electron diffraction has been recently used in the pharmaceutical industry to study the polymorphism in crystalline drug substances. While conventional X-ray diffraction patterns could not be used to determine the cell parameters of two forms of the microcrystalline GP IIb/IIIa receptor antagonist roxifiban, a combination of electron single-crystal and synchrotron powder diffraction techniques were able to clearly distinguish the two polymorphs. The unit-cell parameters of the two polymorphs were ultimately determined using new software routines designed to take advantage of each technique's unique capabilities. The combined use of transmission electron microscopy (TEM) and synchrotron patterns appears to be a good general approach for characterizing complex (low-symmetry, large-unit-cell, micron-sized) polymorphic pharmaceutical compounds.

Enhanced Solubility of Cu in Ag Nanoparticles Synthesized by Inert Gas Condensation

2004 ◽  
Vol 854 ◽  
Author(s):  
Abdullah Ceylan ◽  
C. Ni ◽  
S. Ismat Shah
Keyword(s):  
Electron Diffraction ◽  
Systematic Change ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Vegard’S Law ◽  
Enhanced Solubility ◽  
Diffraction Patterns ◽  
Metal Flux

ABSTRACTAg-Cu alloy nanoparticles were prepared by rapid condensation of metal flux obtained by the simultaneous evaporation of high purity Cu and Ag wires on a tungsten boat in the presence of circulating He gas. Structural properties of the samples prepared at different conditions were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area diffraction (SAD) patterns. X-ray diffraction patterns showed that particles were phase separated. The particle size obtained either from Scherer's formula or the TEM images show no systematic change on the size of either Cu or Ag particles in the evaporation temperature range between 800 and 1400 °C. By using lattice constant values and Vegard's law, the composition of the particles was calculated to be 6.6 vol% Cu in Ag. Electron diffraction images revealed that particles were softly agglomerated; these electron diffraction results were also consistent with XRD results regarding phase separation. Individual diffraction rings of the Cu and Ag were observed in the SAD patterns.

scholarly journals Automated Crystal Orientation Mapping by Precession Electron Diffraction-Assisted Four-Dimensional Scanning Transmission Electron Microscopy Using a Scintillator-Based CMOS Detector

2021 ◽  
Vol 27 (5) ◽  
pp. 1102-1112
Author(s):  
Jiwon Jeong ◽  
Niels Cautaerts ◽  
Gerhard Dehm ◽  
Christian H. Liebscher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Scanning Transmission Electron Microscopy ◽  
Angular Resolution ◽  
Transmission Electron ◽  
Orientation Mapping ◽  
Scanning Transmission ◽  
Precession Electron Diffraction ◽  
Diffraction Patterns

The recent development of electron-sensitive and pixelated detectors has attracted the use of four-dimensional scanning transmission electron microscopy (4D-STEM). Here, we present a precession electron diffraction-assisted 4D-STEM technique for automated orientation mapping using diffraction spot patterns directly captured by an in-column scintillator-based complementary metal-oxide-semiconductor (CMOS) detector. We compare the results to a conventional approach, which utilizes a fluorescent screen filmed by an external charge charge-coupled device camera. The high-dynamic range and signal-to-noise characteristics of the detector greatly improve the image quality of the diffraction patterns, especially the visibility of diffraction spots at high scattering angles. In the orientation maps reconstructed via the template matching process, the CMOS data yield a significant reduction of false indexing and higher reliability compared to the conventional approach. The angular resolution of misorientation measurement could also be improved by masking reflections close to the direct beam. This is because the orientation sensitive, weak, and small diffraction spots at high scattering angles are more significant. The results show that fine details, such as nanograins, nanotwins, and sub-grain boundaries, can be resolved with a sub-degree angular resolution which is comparable to orientation mapping using Kikuchi diffraction patterns.

An Ultra High Vacuum Modular Electron Beam System

1971 ◽  
Vol 29 ◽  
pp. 20-21
Author(s):  
F. Christiansen
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Modular Construction ◽  
X Ray ◽  
Beam System ◽  
Transmission Electron ◽  
Common Foundation ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Traditionally, x-ray microprobes, scanning electron microscopes and similar electron microbeam instruments have been designed and built in much the same manner as transmission electron microscopes; that is, as single purpose instruments with provisions for a miltiplicity of attachments to increase their scope. Electron optically these instruments are nearly identical, the only differences being in mechanical restrictions necessary to accommodate spectrometers, specimen stages, light optics, etc. Hence, it appears desirable to modularize an electron microbeam system to provide a variety of instruments, each sharing a common foundation. This then allows the user to convert an instrument from one configuration to another at minimum expense without sacrificing performance and also to readily construct specialized instruments from standard parts. Other advantages of modular construction, both from the builders' and users' standpoint have been discussed previously.

scholarly journals Phase Identification by Rotation Electron Diffraction from Multiphasic Samples

2014 ◽  
Vol 70 (a1) ◽  
pp. C1080-C1080
Author(s):  
Yifeng Yun ◽  
Wei Wan ◽  
Faiz Rabbani ◽  
Jie Su ◽  
Sven Hovmöller ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Three Dimensional ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Five Phases ◽  
Oxide Sample

Electron Crystallography is an important technique for studying micro- and nano-sized crystals[1]. Crystals considered as powder by X-ray diffraction behave as single crystals by electron diffraction. Recently we developed a new method, Rotation Electron Diffraction (RED) for three-dimensional diffraction data collection by combining electron beam tilt with goniometer tilt on a transmission electron microscope (TEM)[2]. Here we apply the RED method on an unknown oxide sample in a Ni-Se-Cl-O system, which may show special physical properties, for example magnetic properties. The crystals in the sample were less than a few micrometers in sizes. Powder X-ray diffraction patterns of the sample could not be indexed by existing known phases. The sample was thus studied by TEM. Five 3D RED datasets were collected from five crystals with different morphologies using the software package RED. The data processing was also performed using the software RED-processing. The unit cell and space groups of all the five phases were obtained using RED and the structures of four of five phases were solved. Nearly all peaks in the powder X-ray diffraction pattern could be indexed using these five phases. To conclude, five phases from a powder sample have been identified using RED. RED is a powerful method for phase identification of multiphasic samples with nano-sized crystals.

scholarly journals Online Microscopy Lab Training Modules in an Academic Environment

2008 ◽  
Vol 16 (5) ◽  
pp. 44-47
Author(s):  
K. Schierbeek ◽  
A. Mikel ◽  
S. E. Hill ◽  
O. P. Mills
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
X Ray ◽  
Transmission Electron ◽  
Analysis Laboratory ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Fluorescence Spectrometer ◽  
Training Modules ◽  
Operation Cost

The Applied Chemical and Morphological Analysis Laboratory (ACMAL) is a multi-user, multi-disciplinary characterization laboratory. ACMAL houses two scanning electron microscopes (SEM and FE-SEM), a transmission electron microscope (TEM), focused ion beam milling system (FIB), four X-ray diffractometers, and an X-ray fluorescence spectrometer. ACMAL operates as a recharge center where users absorb facility operation cost through an hourly use fee. As such, we are keenly interested in encouraging broad access to the facility by lowering obstacles to users. Facility training enhancements provide the best pathway to productive and responsible facility usage.

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