A simple method for determining orientation and misorientation of the cubic crystal specimen

1994 ◽  
Vol 27 (5) ◽  
pp. 755-761 ◽  
Author(s):  
Q. Liu
Keyword(s):  
Zone Axis ◽  
Beam Direction ◽  
Simple Method ◽  
Axis Orientation ◽  
Cubic Crystal ◽  
Kikuchi Pattern ◽  
Rotation Axes ◽  
Transmission Electron ◽  
Fluorescent Screen

With the aid of a double-tilt holder, a simple method for determining orientation and misorientation of a cubic crystal specimen in a transmission electron microscope is developed. To use this method, a recognizable zone axis from one grain needs to be aligned along the beam direction, the corresponding tilt positions (α 0, β 0) of the two rotation axes must be obtained from the meter reading of the holder and the rotation position of the Kikuchi pattern around the beam direction must be measured on the fluorescent screen with the aid of apparatus for the direct measurement of a diffraction-pattern position on screen. After the input of (α 0, β 0) and the rotation positions, the orientation of the grain can be calculated using a computer program. The misorientation matrix R, rotation angle Θm , axis I m and sense can then be calculated for any selected set of two grains. The accuracy of determination of the orientation of any particular grain is about 1° and, in the case of the determination of misorientation angles between two grains within a sample, the precision is within 0.1°. This method is considered to be much simpler and more rapid than previous methods because no photographs of Kikuchi patterns need to be taken and only one zone-axis orientation needs to be adjusted along the beam direction.

Variation of the ELNES Under Channeling Conditions

2001 ◽  
Vol 7 (S2) ◽  
pp. 342-343
Author(s):  
S. Köstlmeier ◽  
S. Nufer ◽  
T. Gemming ◽  
M. Rühle
Keyword(s):  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Orientation Dependence ◽  
Beam Direction ◽  
Rotation Axes ◽  
Transmission Electron ◽  
Anisotropic Solid ◽  
Scanning Transmission ◽  
Electron Energy Loss ◽  
Acceleration Voltage

The orientation dependence of the fine structure of the Al L1 and L2,3 electron energy loss (EELS) edges in (α-Al2O3 has been investigated by measurements with a dedicated scanning transmission electron microscope (VG HB501 STEM, 100 keV acceleration voltage). α-Al2O3 is an anisotropic solid with a complicated alternating stacking sequence of fee Al and hcp O planes along the [0001] direction [1]. This distingiushes the [0001] direction crystallographically, as the highest-order three-fold rotation axes (C3) of the trigonal crystal structure are parallel to [0001], whereas all other symmetry elements are of lower order. Group theory predicts, that more stringent symmetry selection rules apply when electronic transitions are excited by irradiation parallel to the low-index [0001] zone axis than by irradiation along any other arbitrary direction.Yet, even for a low-energy EELS edge (θE = 0.4 mrad) both scattering parallel and perpendicular to the incident beam direction are likely.

Determination of crystal polarity in the Electron Microscope

1994 ◽  
Vol 52 ◽  
pp. 560-561
Author(s):  
W. Mader ◽  
A. Recnik
Keyword(s):  
Electron Microscope ◽  
Zone Axis ◽  
Mirror Plane ◽  
Polar Crystal ◽  
Transmission Electron ◽  
Polarity Determination ◽  
Extinction Length ◽  
Zero Layer ◽  
Convergent Beam

A few methods were proposed for the determination of crystal polarity using electron diffraction. The method by Taftø and Spence is based on the coupling between ZOLZ and FOLZ reflections, requiring exact tilting to excite weak high- and odd-indexed reflections. The method by Spellward and James relies on the comparison of experimentally observed and calculated CBED patterns of fairly thick crystals, where the features in the CBED discs are compared. In this paper we present a method for polarity determination readily evident from ZOLZ reflections in zone-axis microdiffraction patterns. The method is based on zero-layer interactions from thin crystals with thickness t smaller than the extinction length of the primary beam. Then the diffraction discs appear homogeneous, and the breakdown of Friedel's law is noticable in a difference of the intensities of the reflections g and -g which are not related to a mirror plane (Bijvoet-related reflections).The method can be applied using any transmission electron microscope which is designed for obtaining convergent-beam microdiffraction patterns and in principle, specimen-cooling is not necessary. The crystals have to be oriented to a low-indexed zone axis, where the diffraction plane contains a polar crystal axis.

Characterization of the parameters relating adjacent grains using transmission electron microscopy

2010 ◽  
Vol 43 (6) ◽  
pp. 1495-1501 ◽  
Author(s):  
H. W. Jeong ◽  
S. M. Seo ◽  
H. U. Hong ◽  
Y. S. Yoo
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Coincident Site Lattice ◽  
Cubic Crystal ◽  
Kikuchi Pattern ◽  
Orthogonal Relationship ◽  
Transmission Electron ◽  
Angle Of Deviation ◽  
The Relationship

A simple technique is presented for characterizing parameters such as the misorientation angle and the axis of rotation between two adjacent grains using transmission electron microscopy (TEM), without the need for an image of the Kikuchi pattern. The technique described makes use of the orthogonal relationship between the tilt axes used in TEM and the axes of the cubic crystal. The relationship was established using the well known triangulation method, in which the direction of the crystal parallel to the beam direction is determined from the measured tilt angles of the three zone axes. The error in measuring the tilt angles of the three zone axes can be evaluated by comparing the measured and crystallographic angles. The angle of deviation from the coincident site lattice (CSL) that results from the measurement error could be reduced by establishing the modified orthogonal relationship between the tilt and crystal axes. The use of this method could provide accurate measurement in real time for indexing a CSL boundary using TEM.

Determination of crystal orientation by a zone axis method application to grain boundaries

1978 ◽  
Vol 36 (1) ◽  
pp. 426-427 ◽  
Author(s):  
A. Rocher ◽  
C. Fontaine
Keyword(s):  
Crystal Orientation ◽  
Zone Axis ◽  
Coordinate Frame ◽  
In Situ Method ◽  
Transmission Electron ◽  
Kikuchi Lines ◽  
Diffraction Patterns ◽  
Better Than

Several methods (1 → 3) have been proposed in order to determine by transmission electron microscopy (TEM) the orientation relationship between the crystal and the electron beam. The same type of method (4) has been used to find the orientation of a bicrystal. The most accurate ones (better than 0.1°) are based on the measurement of the relative position of Kikuchi lines with respect to diffraction spots. Such analysis are performed on diffraction pattern micrographs. The aim of the present work is to develop for TEM an in situ method for determination of the crystal orientation with respect to the goniometer coordinate frame, avoiding any analysis of the diffraction micrographs. The diffraction patterns used for this characterization are associated to the zone axis of the crystal. The method consists in plotting on the same stereographic projection the coordinate frame of the goniometer stage and the <100> axis of the crystal. These axis are determined from experimental indexation of three zone axis.

Modeling and simulation of octahedral Pb inclusions in Al

1995 ◽  
Vol 53 ◽  
pp. 646-647
Author(s):  
S.Q. Xiao ◽  
S. Paciornik ◽  
R. Kilaas ◽  
E. Johnson ◽  
U. Dahmen
Keyword(s):  
Total Sample ◽  
Inclusion Size ◽  
Zone Axis ◽  
Sample Thickness ◽  
Solidification Behavior ◽  
Axis Orientation ◽  
Resolution Electron ◽  
The Matrix ◽  
High Resolution Electron Micrographs

Pb inclusions in Al have been extensively studied for their unusual melting/solidification behavior. Pb inclusions have a cube on cube parallel orientation relationship with the Al matrix and assume cuboctahedral shapes faceted on {111} and {100}. Al and Pb are both fcc structures but with very different lattice parameters: aAl = 0.405 nm, apb = 0.495 nm. Thus 5 Al spacings match approximately 4 Pb spacings giving rise to a moire pattern visible in HREM images.High resolution electron micrographs in the <110> zone axis orientation were recorded on the Berkeley ARM at an accelerating voltage of 800 kV. In this orientation the cuboctahedra project as truncated parallelograms as shown in Fig. 1. Although the four (111) interfaces revealed in Fig. 1 are imaged edge-on, the Al lattice overlaps the Pb lattice above and below, because the other four (111) interfaces are inclined. Therefore, even though the (111)Al lattice is clearly resolved, the determination of inclusion size is not straightforward because the contrast depends on defocus (Δf), particle size (s), depth of the inclusion in the matrix (z) and total sample thickness (t).

Accurate Determination of Foil Surface Normal in a Material with Stacking Faults

1980 ◽  
Vol 38 ◽  
pp. 378-379
Author(s):  
Samuel M. Allen
Keyword(s):  
Dihedral Angle ◽  
Accurate Determination ◽  
Stacking Faults ◽  
Optical Metallography ◽  
Dihedral Angles ◽  
Foil Surface ◽  
Beam Direction ◽  
Surface Normal ◽  
Transmission Electron

This paper describes a method for determining the foil surface normal in a transmission electron microscopy (TEM) sample containing stacking faults. The method makes use of observed dihedral angles at stacking fault intersections to compute the foil normal, when the beam direction is known. Dihedral angles are angles formed at the intersections of surfaces. The true dihedral angle is observed when viewed parallel to the line of intersection of the surfaces. For optical metallography, where observations are made by viewing normal to a plane of polish, the observed dihedral angle is the angle formed by thetraces of the intersecting surfaces on the plane of polish. The geometry of this problem was considered by Harker and Parker, who demonstrated that the observed angle could be either greater or less than the true angle.

Nanosized Gadoliniumorthoferrite-based Electrochemical Sensor for the Determination of Dopamine

Nano LIFE ◽  
2021 ◽  
pp. 2150002
Author(s):  
Susmita Pramanik ◽  
Yogendra Kumar ◽  
Parimal Karmakar ◽  
Dipak Kumar Das
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Sensor ◽  
Graphite Powder ◽  
Differential Pulse ◽  
Ferrite Nanoparticles ◽  
Ferric Nitrate ◽  
Cubic Crystal ◽  
Transmission Electron

This work deals with the synthesis, characterization of gadolinium ferrite nanoparticles, and its use as an electrochemical sensor for detection of dopamine. For the synthesis of gadolinium ferrite nanoparticles (GdFeO3 NPs), the combustion technique was employed using gadolinium oxide and ferric nitrate as precursor materials with sugar and ethanolamine as fuel. The size, shape and morphology of nanomaterials were determined by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The crystallite size of synthesized nanoparticles was found to be in the range of 40–45[Formula: see text]nm with a cubic crystal system. The electrochemical sensor, GdFeO3 NPs@graphite paste (GdFeO3/GP), was prepared by using synthesized nanomaterials and graphite powder by mixing in mortar in 1:4 ratio. cyclic voltammetry (CV) and Differential pulse voltammetry (DPV) techniques were employed to assess the electrochemical properties of the developed sensor. The result indicated that the developed sensor possessed better sensing ability, where minimum detection limit of dopamine at GdFeO3/GP electrode was 700[Formula: see text]nM with linearity range from 5[Formula: see text][Formula: see text]M to 160[Formula: see text][Formula: see text]M.

Transmission Electron Microscopy of Protein Macromolecules

1971 ◽  
Vol 29 ◽  
pp. 424-425
Author(s):  
Henry S. Slayter
Keyword(s):  
Biological Systems ◽  
Metal Vapor ◽  
Resolving Power ◽  
Electron Microscopic ◽  
Chemical Methods ◽  
Molecular Weights ◽  
The Past ◽  
Physical Chemical ◽  
Transmission Electron

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.

Determination of the phase structure of polymerblends by electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 492-493
Author(s):  
Dr. G. Kaemof
Keyword(s):  
Screw Extruder ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Single Screw Extruder ◽  
Transmission Electron ◽  
The Matrix ◽  
Twin Screw ◽  
Special Case ◽  
Microscopic Investigations

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.

Prospects for convergent beam electron diffraction with a 200kV cold field-emission transmission electron microscope

1991 ◽  
Vol 49 ◽  
pp. 466-467
Author(s):  
J W Steeds ◽  
R Vincent
Keyword(s):  
Field Emission ◽  
High Performance ◽  
Small Diameter ◽  
Convergent Beam Electron Diffraction ◽  
Zone Axis ◽  
Medium Voltage ◽  
Transmission Electron ◽  
Good Crystallinity ◽  
Special Modification ◽  
Convergent Beam

We review the analytical powers which will become more widely available as medium voltage (200-300kV) TEMs with facilities for CBED on a nanometre scale come onto the market. Of course, high performance cold field emission STEMs have now been in operation for about twenty years, but it is only in relatively few laboratories that special modification has permitted the performance of CBED experiments. Most notable amongst these pioneering projects is the work in Arizona by Cowley and Spence and, more recently, that in Cambridge by Rodenburg and McMullan.There are a large number of potential advantages of a high intensity, small diameter, focussed probe. We discuss first the advantages for probes larger than the projected unit cell of the crystal under investigation. In this situation we are able to perform CBED on local regions of good crystallinity. Zone axis patterns often contain information which is very sensitive to thickness changes as small as 5nm. In conventional CBED, with a lOnm source, it is very likely that the information will be degraded by thickness averaging within the illuminated area.

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