On the Characterisatiopn of Order-Disorder in Ion-Irradiated Pyrochlore Compounds by Electron Scattering Methods

2008 ◽  
Vol 1122 ◽  
Author(s):  
Gregory R. Lumpkin ◽  
Karl R. Whittle ◽  
Mark G. Blackford ◽  
Katherine L. Smith ◽  
Nestor J. Zaluzec
Keyword(s):  
Electron Scattering ◽  
Diffuse Scattering ◽  
Zone Axis ◽  
Irradiation Damage ◽  
Nuclear Materials ◽  
Crystalline Fraction ◽  
Selected Area Electron Diffraction ◽  
Pyrochlore Compounds ◽  
Diffraction Patterns

AbstractSelected area electron diffraction patterns are routinely used to determine the effects of irradiation damage in nuclear materials. Using zone axis orientations, the intensities of Bragg beams change from a dynamical to kinematic-like state due to the presence of amorphous domains in the material. Such changes in beam intensities, together with the increased diffuse scattering from the increasing amorphous fraction, present a major obstacle to the determination of cation or anion disorder in the crystalline fraction.

Inelastic Electron Scattering from Valence Electrons in Aluminum

1976 ◽  
Vol 34 ◽  
pp. 462-463
Author(s):  
P. E. Batson ◽  
C. H. Chen ◽  
J. Silcox
Keyword(s):  
Electron Scattering ◽  
Single Scattering ◽  
Three Dimensions ◽  
Inelastic Electron ◽  
Weak Beam ◽  
Scattering Spectrum ◽  
Valence Electrons ◽  
Diffraction Patterns ◽  
Electronic Scattering

We wish to report in this paper measurements of the inelastic scattering component due to the collective excitations (plasmons) and single particlehole excitations of the valence electrons in Al. Such scattering contributes to the diffuse electronic scattering seen in electron diffraction patterns and has recently been considered of significance in weak-beam images (see Gai and Howie) . A major problem in the determination of such scattering is the proper correction for multiple scattering. We outline here a procedure which we believe suitably deals with such problems and report the observed single scattering spectrum.In principle, one can use the procedure of Misell and Jones—suitably generalized to three dimensions (qx, qy and #x2206;E)--to derive single scattering profiles. However, such a computation becomes prohibitively large if applied in a brute force fashion since the quasi-elastic scattering (and associated multiple electronic scattering) extends to much larger angles than the multiple electronic scattering on its own.

A study of the high-Cu Al–Cu–Co decagonal phase

1993 ◽  
Vol 8 (7) ◽  
pp. 1473-1476 ◽  
Author(s):  
B. Grushko
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Diffraction ◽  
Diffuse Scattering ◽  
Nonequilibrium State ◽  
Zone Axis ◽  
Decagonal Phase ◽  
Diffraction Patterns ◽  
Scanning Electron

The decagonal phase was studied by transmission and scanning electron microscopy in an Al62Cu24Co14 alloy annealed at 550–850 °C. The electron diffraction patterns of the decagonal phase exhibited weak quasiperiodic odd-n reflections in the [1-2100] zone axis corresponding to the equilibrated structure. The relative intensities of these reflections were significantly lower in the Al62Cu24Co14 than in the Al68Cu11Co21 decagonal phase. Diffuse scattering observed previously at the same positions can be related to a nonequilibrium state of the decagonal phase.

Space group determination by CBED: G-M lines and holz interactions

1992 ◽  
Vol 50 (2) ◽  
pp. 1186-1187
Author(s):  
Vinayak P. Dravid
Keyword(s):  
Diffuse Scattering ◽  
Zone Axis ◽  
Translational Symmetry ◽  
Screw Axis ◽  
Careful Choice ◽  
Space Group ◽  
Exact Location ◽  
Unambiguous Determination ◽  
Crystal Space

Symmetry determination remains as a powerful and fascinating application of CBED techniques. As pointed out by Gjønnes & Moodie and later developed by Steeds & Vincent, the appearance of lines of missing intensity (G-M lines) in certain kinematically forbidden reflections in CBED patterns can be analyzed to obtain information about the presence and type of translational symmetry elements in the crystal space group, such as screw axis and glide planes. However, the microscopist must be aware of numerous pitfalls in analyzing G-M lines as they can be confused with other diffuse scattering (2-D diffraction) present in most CBED patterns. Furthermore, unambiguous determination of exact translational symmetry elements and their orientation requires careful choice of zone axis, voltage and analysis of indices of the forbidden reflections. When done properly, such experiments reveal the exact location and type of translational symmetry elements, e.g. whether the glide plane is a, b, c, n or d type.

Comparison of Multislice Computer Programs for Electron Scattering Simulations and The Bloch Wave Method

2000 ◽  
Vol 6 (S2) ◽  
pp. 126-127
Author(s):  
C. Koch ◽  
J.M. Zuo
Keyword(s):  
Electron Microscope ◽  
Quantitative Analysis ◽  
Electron Scattering ◽  
Electron Beams ◽  
Bloch Wave ◽  
Zone Axis ◽  
Wave Method ◽  
Software Packages ◽  
Transmission Electron ◽  
Diffraction Patterns

As the demand for quantitative analysis of Transmission Electron Microscope (TEM) images and diffraction patterns increases, questions arise about the reliability of computer simulations using different software packages and algorithms that are used for comparison with the experiment. Here, we compared five multislice programs, which are (with the exception of Cerius2) freely available, with each other and also a Bloch wave code. Since multislice method propagates the electron beams through the crystal slice by slice, the development of differences between the programs can easily be seen by comparing amplitudes and phases of different beams vs. thickness (Pendelloesung plot). We calculated Pendelloesung plots for InP [001] in zone axis and tilted beam orientations and the Si [111] forbidden reflections using the following codes: Cerius2, NCEMSS, Autoslic3, Multis4, EMS5 and an updated Bloch wave code written by J.M. Zuo4.

The Determination of Rotation Axis in the Rotation Electron Diffraction Technique

2013 ◽  
Vol 19 (5) ◽  
pp. 1276-1280 ◽  
Author(s):  
Mika Buxhuku ◽  
Vidar Hansen ◽  
Peter Oleynikov ◽  
Jon Gjønnes
Keyword(s):  
Electron Diffraction ◽  
Rotation Axis ◽  
Incident Beam ◽  
Zone Axis ◽  
Crystallographic Direction ◽  
Accurate Knowledge ◽  
Electron Diffraction Technique ◽  
Diffraction Patterns

AbstractMethods to determine the rotation axis using the rotation electron diffraction technique are described. A combination of rotation axis tilt, beam tilt, and simulated experimental diffraction patterns with nonintegers zone axis has been used. Accurate knowledge of the crystallographic direction of the incident beam for deducing the excitation error of reflections simultaneously near Bragg positions is essential in quantitative electron diffraction. Experimental patterns from CoP3 are used as examples.

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.

Pb Displacements in Pb(ZrTi)O3 (PZT)

2009 ◽  
Vol 421-422 ◽  
pp. 389-394 ◽  
Author(s):  
T.R. Welberry ◽  
K.Z. Baba-Kishi ◽  
R.L. Withers
Keyword(s):  
Computer Simulation ◽  
Monte Carlo ◽  
High Temperature ◽  
Diffuse Scattering ◽  
Structural Models ◽  
Cubic Phase ◽  
Rich Phase ◽  
Monte Carlo Computer Simulation ◽  
Selected Area Electron Diffraction ◽  
Diffraction Patterns

Structured diffuse scattering has been observed in selected area electron diffraction patterns of PbZr1-xTixO3 (PZT). This scattering is most evident in the rhombohedral (Zr-rich) phase but has also been observed for a range of compositions including in the important morphotropic phase boundary (MPB) region as well as in the tetragonal (Ti-rich) phase. Monte Carlo computer simulation has been used to show that the scattering originates from the correlation between the displacements of cations in chains running along all four of the cubic <111>c directions. The transverse polarised nature of the scattering means that the ionic shifts are also directed along <111>c. The results are difficult to reconcile with current structural models for the low temperature phases of PZT. It is conjectured that these phases must still contain significant remnants of the disorder present in the high-temperature paraelectric cubic phase.

Continuous Diffuse Electron Scattering from Polymethylene Compounds. A Qualitative Description

1977 ◽  
Vol 32 (10) ◽  
pp. 1161-1165 ◽  
Author(s):  
Douglas L. Dorset
Keyword(s):  
Fourier Transform ◽  
Electron Diffraction ◽  
Electron Scattering ◽  
Diffuse Scattering ◽  
Qualitative Description ◽  
Thermal Diffuse Scattering ◽  
Diffraction Patterns ◽  
Difference Fourier ◽  
Thermal Diffuse

The positions of continuous thermal diffuse scattering streaks in electron diffraction patterns of polymethylene chains packing in hexagonal and orthorhombic perpendicular subcells are predicted using the kinematical difference Fourier transform model of Amoros and Amoros. Indications of correlated chain motions are found for the case of the orthorhombic subcell

Soft Phonons and Anti-phase Domains in SrTiO3 : an Electron Diffuse Scattering Study

1999 ◽  
Vol 5 (S2) ◽  
pp. 212-213
Author(s):  
Renhui Wang ◽  
Yimei Zhu
Keyword(s):  
Phase Transition ◽  
Electron Diffraction ◽  
Diffuse Scattering ◽  
Phonon Mode ◽  
Unit Cell ◽  
Selected Area Electron Diffraction ◽  
Ewald Sphere ◽  
Scattering Study ◽  
Diffraction Patterns ◽  
Tetragonal Phase Transition

It is well known that cubic SrTiO3 possesses a typical perovskite structure whose reciprocal unit cell is shown in Fig. 1 where X, M, and R designate particular points at Brillouin zone boundaries with the Γ point being the zone origin. The instability of the phonon mode designated by the R point leads to the cubic-to-tetragonal phase transition of SrTiO3 at Tc=103 K. By using the same unit-cell as the cubic SrTiO3, reflections (h k 1) / 2 with h, k, and 1 all odd are superlattice reflections characteristic of tetragonal SrTiO3. Previous investigations of diffuse scattering were carried out by neutron and xray diffraction at Temperatures below 240 K. In the present work, observation of the diffuse scattering was extended to a broad Temperature range of 20 ∼ 700 K.Selected-area electron diffraction patterns (EDPs) reveal splitting and streaking of the superlattice reflections as shown in Fig. 2. We can see streaks along the [1 0 0]* direction, e.g., the streak connecting (5 3-5) / 2 and (7 3-5) / 2, the streak connecting (-3-5 7) / 2 and (-1-5 7) / 2. Splitting of the superreflections (7-1-1) / 2, (9-1-1) / 2, and (-7 1 1) / 2, along [0 1-1]* direction is evident. All the splitting and streaking behaviors shown in Fig. 2 and observed in other EDPs may be interpreted as being formed by the intersection of the Ewald sphere with reciprocal rods MRM shown in Fig. 1, which are along the <100>* direction passing through superlattice points.

Computer Indexing of Electron Diffraction Patterns Including the Effects of Lattice Symmetry

1977 ◽  
Vol 35 ◽  
pp. 22-23
Author(s):  
J. S. Lally ◽  
R. J. Lee
Keyword(s):  
Electron Diffraction ◽  
Zone Axis ◽  
Crystal Thickness ◽  
Double Diffraction ◽  
Automated Method ◽  
Lattice Symmetry ◽  
Intensity Calculations ◽  
Unknown Structure ◽  
Diffraction Patterns ◽  
Orientation Parameters

In the 50 year period since the discovery of electron diffraction from crystals there has been much theoretical effort devoted to the calculation of diffracted intensities as a function of crystal thickness, orientation, and structure. However, in many applications of electron diffraction what is required is a simple identification of an unknown structure when some of the shape and orientation parameters required for intensity calculations are not known. In these circumstances an automated method is needed to solve diffraction patterns obtained near crystal zone axis directions that includes the effects of systematic absences of reflections due to lattice symmetry effects and additional reflections due to double diffraction processes.Two programs have been developed to enable relatively inexperienced microscopists to identify unknown crystals from diffraction patterns. Before indexing any given electron diffraction pattern, a set of possible crystal structures must be selected for comparison against the unknown.

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