The study of modulated structures, mixed layer polytypes and 1-D quasi-crystals by means of electron microscopy and electron diffraction

1989 ◽  
Vol 16 (1-4) ◽  
pp. 3-40 ◽  
Author(s):  
S. Amelinckx ◽  
G. Van Tendeloo ◽  
D. Van Dyck ◽  
J. Van Landuyt
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Mixed Layer ◽  
Modulated Structures ◽  
Quasi Crystals

Electron Microscopic Study of Long Period Modulated Structures with Continuously Variable Periodicity

1983 ◽  
Vol 21 ◽  
Author(s):  
D. Colaitis ◽  
Van Dyck ◽  
C. Conde-Amiano ◽  
S. Amelinckx
Keyword(s):  
Electron Microscopy ◽  
Phase Transitions ◽  
Electron Diffraction ◽  
Microscopic Study ◽  
Electron Microscopic ◽  
Antiphase Boundaries ◽  
Planar Defects ◽  
Long Period ◽  
Modulated Structures ◽  
Reversible Phase

ABSTRACTSome systems show continuous and reversible phase transitions which are characterised by the appearance of irrational sunerlattice reflections with a position that shifts continuously and reversibly with temperature. This diffraction feature is not necessarily caused by a deformation modulation but can also originate from the reneated occurrence of planar defects with a variable “average” periodicity. The planar defects can be of different type (e.g. planes of different composition, antiphase boundaries, twin planes) as shown for the systems Ni3+xTe2, Cu3−xTe2, Cu2−S, mPbS-nBi2S3 ( > 2) and Cu 0.75VS2, using electron-microscopy and electron diffraction.

Modulated structures of Bi-based high-Tc superconducting oxides studied by High Resolution Electron Microscopy and electron diffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 80-81
Author(s):  
Sigemaro Nagakura ◽  
Yoshihiko Hirotsu ◽  
Naoki Yamamoto ◽  
Katsumi Miyagawa ◽  
Yuji Ikeda ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
High Tc ◽  
Modulated Structures ◽  
Resolution Electron ◽  
Incommensurate Structures ◽  
Superconducting Oxides ◽  
Electron Microscopes

In the superconducting Bi-Sr-Ca-Cu-O system, ideal compositions of the low Tc(Tc∼90 K) and the high Tc(Tc∼110K) phases are Bi2Sr2CaCu2Oy(y∼8:2212 phase) and Bi2Sr2Ca2 Cu3Oy (y∼10:2223 phase), respectively. The fundamental structures of these phases are tetragonal with parameters: at=bt=0.54 and ct=3.08 nm for the 2212 phase, and at=bt=0.54 and ct=3.71 nm for the 2223 phase. These phases have incommensurate structures with modulation along their b-axes. In this study, the modulated structures of Pb-doped 2212 and 2223 phases have been investigated by means of high resolution electron microscopy and electron diffraction. Samples Bi2-xPbxSr2CaCu2Oy(x=0-0.4, melt-quenched and annealed) and Bi2−xPbxSr2Ca2Cu3Oy(x=0-0.6, sintered) were observed in high resolution electron microscopes operating at 200 kV and 1 MV.Analysis of the incommensurate modulated structures of the 2212 and 2223 phases was made by using samples Bi2Sr2CaCu2Oy and Bi1.6Pb0.4Sr2Ca2Cu3Oy. The lattice parameters of the incommensurate superstructures are a=at and c=ct for both of these phases, but b∼5bt and b∼bt for the 2212 and 2223 phases, respectively.

A study of one-dimensional incommensurate modulated structure determination in high-resolution transmission electron microscopy

2014 ◽  
Vol 70 (6) ◽  
pp. 563-571 ◽  
Author(s):  
Xueming Li ◽  
Binghui Ge ◽  
Fanghua Li ◽  
Huiqian Luo ◽  
Haihu Wen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Dimensional Structure ◽  
Electron Diffraction Data ◽  
Image Deconvolution ◽  
Transmission Electron ◽  
Modulated Structures ◽  
Phase Extension

The methods for determining incommensurate modulated structures (IMSs) in high-resolution transmission electron microscopy have been studied and improved to a level more perfect than before. This is demonstrated by means of the IMS determination for Bi2.31Sr1.69CuO6+δas an example. First, as previously, the projected potential map (PPM) of the IMS with resolution 0.2 nm was obtained after image deconvolution from a [100] image. Secondly, the resolution of the PPM was enhanced to 0.1 nm through phase extension combined with the electron-diffraction data so that the substitutional and displacive modulation functions could be determined. Thirdly, a (2+1)-dimensional structure model that corresponds to the [100] projected IMS was built for calculating the related partial structure factors that were utilized to correct the experimental electron-diffraction intensities for both main and satellite reflections. After three cycles of diffraction-intensity correction and phase extension, all unoverlapped atoms projected along the [100] direction in Bi2.31Sr1.69CuO6+δwere resolved, and the modulations of substitution and displacement could be observed clearly. The substitution of Bi for Sr atoms at the Sr(O) columns was seen in the final PPM and verified by high-dimensional image simulation.

New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

1971 ◽  
Vol 29 ◽  
pp. 44-45
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Electron Diffraction ◽  
Water Vapor Pressure ◽  
Biological Materials ◽  
Thin Membrane ◽  
Reliable System ◽  
System A ◽  
Water Films ◽  
Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

Studies of Oxide Formation on Copper Thin Films by Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 316-317
Author(s):  
G. G. Hembree ◽  
M. A. Otooni ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Crystal Surface ◽  
Crystal Defects ◽  
Diffraction Reflection ◽  
Reaction Products ◽  
Intermediate Energies ◽  
Crystal Films ◽  
Reflection Electron Microscopy

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.

Dynamical Scattering in Crystalline Biological Specimens. I. Criteria of Validity for Scattering Approximations

1975 ◽  
Vol 33 ◽  
pp. 192-193
Author(s):  
Robert M. Glaeser ◽  
Bing K. Jap
Keyword(s):  
Biological Sciences ◽  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Born Approximation ◽  
Materials Science ◽  
Image Data ◽  
Dynamical Effect ◽  
Crystallographic Structure ◽  
Electron Microscope Image

The dynamical scattering effect, which can be described as the failure of the first Born approximation, is perhaps the most important factor that has prevented the widespread use of electron diffraction intensities for crystallographic structure determination. It would seem to be quite certain that dynamical effects will also interfere with structure analysis based upon electron microscope image data, whenever the dynamical effect seriously perturbs the diffracted wave. While it is normally taken for granted that the dynamical effect must be taken into consideration in materials science applications of electron microscopy, very little attention has been given to this problem in the biological sciences.

Characterization of submicrometer fluid Inclusions in minerals by Analytical/Transmission Electron Microscopy and electron diffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 424-424
Author(s):  
George Guthrie ◽  
David Veblen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Light Microscopy ◽  
Fluid Inclusions ◽  
Energy Dispersive Spectrometer ◽  
Analytical Transmission Electron Microscopy ◽  
Transmission Electron

The nature of a geologic fluid can often be inferred from fluid-filled cavities (generally <100 μm in size) that are trapped during the growth of a mineral. A variety of techniques enables the fluids and daughter crystals (any solid precipitated from the trapped fluid) to be identified from cavities greater than a few micrometers. Many minerals, however, contain fluid inclusions smaller than a micrometer. Though inclusions this small are difficult or impossible to study by conventional techniques, they are ideally suited for study by analytical/ transmission electron microscopy (A/TEM) and electron diffraction. We have used this technique to study fluid inclusions and daughter crystals in diamond and feldspar.Inclusion-rich samples of diamond and feldspar were ion-thinned to electron transparency and examined with a Philips 420T electron microscope (120 keV) equipped with an EDAX beryllium-windowed energy dispersive spectrometer. Thin edges of the sample were perforated in areas that appeared in light microscopy to be populated densely with inclusions. In a few cases, the perforations were bound polygonal sides to which crystals (structurally and compositionally different from the host mineral) were attached (Figure 1).

Computers and diffraction analysis

1989 ◽  
Vol 47 ◽  
pp. 44-45
Author(s):  
J. A. Eades
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Diffraction Analysis ◽  
Electron Diffraction Analysis ◽  
Image Simulation ◽  
Correct Interpretation ◽  
High Profile ◽  
High Resolution Images ◽  
Image Simulations

For well over two decades computers have played an important role in electron microscopy; they now pervade the whole field - as indeed they do in so many other aspects of our lives. The initial use of computers was mainly for large (as it seemed then) off-line calculations for image simulations; for example, of dislocation images.Image simulation has continued to be one of the most notable uses of computers particularly since it is essential to the correct interpretation of high resolution images. In microanalysis, too, the computer has had a rather high profile. In this case because it has been a necessary part of the equipment delivered by manufacturers. By contrast the use of computers for electron diffraction analysis has been slow to prominence. This is not to say that there has been no activity, quite the contrary; however it has not had such a great impact on the field.

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