scholarly journals Synchysite-(Ce) from Cinquevalli (Trento, Italy): Stacking Disorder and the Polytypism of (Ca,REE)-Fluorcarbonates

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 77 ◽  
Author(s):  
Giancarlo Capitani
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stacking Faults ◽  
Stacking Sequence ◽  
Transmission Electron ◽  
Unit Cells ◽  
Cell Refinement ◽  
Diffraction Patterns ◽  
Microscopy Images ◽  
Stacking Disorder

Synchysite-(Ce) at Cinquevalli occurs as fine needles intergrown with quartz in quartz-dikes and in association with altered K-feldspar and oxidized chalcopyrite as major constituents. Synchysite-(Ce) [Ca1.00(Ce0.43La0.26Nd0.17Y0.07Pr0.04Sm0.02Gd0.01)Σ=1.00(CO3)2(F0.58(OH)0.42)], shows an overgrowth rim of bastnäsite-(Ce) [(Ce0.34La0.25Nd0.17Pb0.07C a0.06Y0.06Pr0.04S m0.02Gd0.01)Σ=1.00C O3(F0.75(OH)0.25)]. Unit cell refinement of synchysite (C2/c) and bastnäsite (P62c) led to a = 12.272(4), b = 7.100(2), c = 18.640(5) Å, β = 102.71(5)°, and a = 7.085(1), c = 9.746(2) Å, respectively. Polysomatic faults are sporadic, but polytypic disorder is widespread. High resolution transmission electron microscopy images taken along [100] or ⟨130⟩ show an apparent order and the related diffraction patterns are streak-free. Conversely, along [010] or ⟨110⟩, a high density of stacking faults is observed and the related diffraction patterns show hhl rows with h ≠ 3n affected by streaks. No ordered domain larger than a few unit cells was detected. The stacking sequence of (Ca,REE)-fluorcarbonates can be compared with subfamily-B mica polytypes (2M2, 2O and 6H), which are characterized by n·60° (n = odd) rotations. Subfamily-A polytypes (1M, 2M1 and 3T), characterized by n·60° (n = even) rotations, should not be possible. Synchysite, characterized by ±60° rotations, can be likened to the 2M2 polytype.

Surface structure of (001) Au films by high resolution transmission electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 246-247
Author(s):  
William Krakow
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Atomic Layer ◽  
Surface Layers ◽  
Transmission Electron ◽  
Fcc Lattice ◽  
Unit Cells ◽  
Diffraction Patterns ◽  
Fractional Unit

In nonprimitive lattices, surface layers corresponding to partially filled unit cells give rise to reflections forbidden in the bulk structure. These reflections allow detailed studies of the surface layer by high resolution transmission electron microscopy and computer modeling experiments.The occurrence of fractional unit cells at the surface of (001) oriented Au films can be demonstrated by assembling the fcc lattice by the alternate stacking of planar {100} type layers such that the atoms of,each atomic layer are embedded in the depressions of neighboring planes above and below. The stacking sequence is of the ABABAB….type with the B layers shifted an amount ao/2 in the [100] direction (Fig. 1a). The presence of an excess A or B layer gives rise to additional reflections with mixed odd and even Miller indices which are forbidden in the fcc lattice, e.g., (110). In obtaining diffraction patterns from ∼100Å thick Au films the forbidden reflections were approximately 2% of the corresponding bulk lattice reflections and easily identified (see Fig. 1b).

Analysis of Lattice Defects in an Epitaxial PbTiO3 Thick Film by Transmission Electron Microscopy

2013 ◽  
Vol 566 ◽  
pp. 171-174
Author(s):  
Kenta Aoyagi ◽  
Takanori Kiguchi ◽  
Yoshitaka Ehara ◽  
Hiroshi Funakubo ◽  
Toyohiko J. Konno
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Thick Film ◽  
Strain Relaxation ◽  
Stacking Faults ◽  
Local Strain ◽  
Transmission Electron ◽  
Unit Cells ◽  
High Resolution Tem ◽  
Measured Strain

The microstructure of an epitaxial PbTiO3 thick film was investigated by using transmission electron microscopy (TEM). An analysis of bright-field TEM (BFTEM) images revealed the existence of displacements along the [00 direction of PbTiO3. High-resolution TEM (HRTEM) observation indicated that stacking faults parallel to the (001) plane of PbTiO3 are formed in the thick film. Local strain fields around the stacking faults were quantified by geometric phase analysis of the HRTEM image. The measured strain suggested the presence of a pair of extrinsic and intrinsic stacking faults. The distance between an extrinsic stacking fault and an intrinsic one corresponds to two unit cells along the [00 direction of PbTiO3. The formation of these stacking faults is considered to be associated with the strain relaxation of the film.

scholarly journals Patterns detection in diffraction images of transmission electron microscopy

2020 ◽  
Author(s):  
Stepan Nebaba ◽  
Alexander Pak
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Transmission Electron Microscopy ◽  
Distance Estimation ◽  
Transmission Electron ◽  
Automated Processing ◽  
Material Sample ◽  
Diffraction Patterns ◽  
Automated Algorithms ◽  
Microscopy Images

Specialized software that supports existing approaches to processing images of the crystal structure of materials for analyzing transmission electron microscopy images have a lot of different digital image processing methods, but major part of it are weakly automated. In some tasks automated algorithms of image processing have been developed, e.g. in task of estimation of the width of a layer of material from a raster image. The paper considers the problem of automated processing of diffraction images obtained by transmission electron microscopy. A number of modifications, such as Watershed algorithm, binarization and Fast Fourier Transform, are proposed for existing image processing algorithms. These modifications can help automate the processing of the diffraction pattern of a material sample from an image of transmission electron microscopy. The given examples of image processing of particular cases of diffraction patterns have shown the prospects for the development of algorithm based on combination of the proposed modifications of considered algorithms. Adaptive binarization with Watershed segmentation would be useful in automated distance estimation in transmission electron microscopy images.

TEMTUTOR - a Teaching Multimedia Program for TEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 1161-1162
Author(s):  
V.-T. Kuokkala ◽  
T.K. Lepistö
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Stacking Faults ◽  
Teaching Tool ◽  
Formation Processes ◽  
Multimedia Program ◽  
Transmission Electron ◽  
Hands On ◽  
Diffraction Patterns

Teaching of transmission electron microscopy usually includes both lectures on the contrast theories, electron diffraction, etc., and practical hands-on operation of the microscope. The number of students attending the lectures is normally unlimited, but at the microscope, only a few persons can work at the same time. Since the microscopes are expensive, it would be of a great help if cheaper 'training' microscopes with basic imaging and diffraction capabilities were available. These functions, in fact, can quite easily be realized with fast personal computers and work stations, where the simulation of transmission electron micrographs and related diffraction patterns can help the student better understand the image formation processes. Adding text, audio and video help capabilities to the program, it can be made an efficient supplemental teaching tool.TemTutor for Windows is based on microScope for Windows, which is a BF/DF TEM micrograph simulation program for dislocations and stacking faults.

Planar defects in β-iron disilicide (β-FeSi2) analyzed by transmission electron microscopy and modeling

1992 ◽  
Vol 25 (2) ◽  
pp. 122-128 ◽  
Author(s):  
Y. Zheng ◽  
A. Taccoen ◽  
J. F. Petroff
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Model ◽  
Stacking Faults ◽  
Planar Defects ◽  
Iron Disilicide ◽  
Defect Position ◽  
Transmission Electron ◽  
Lattice Images ◽  
Diffraction Patterns

Microplanar defects were observed in β-iron disilicide by transmission electron microscopy. They were identified as (100)[011]/2 intrinsic stacking faults by means of electron diffraction patterns and observed in high-resolution lattice images. A structural model of the faults is proposed here in setting the defect position at x = ¼ within the cell.

Effects of High-Energy Ions on Synthetic Quartz

1972 ◽  
Vol 30 ◽  
pp. 544-545
Author(s):  
Joseph J. Comer ◽  
Charles Bergeron ◽  
Lester F. Lowe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
High Energy ◽  
Transmission Electron ◽  
Kikuchi Lines ◽  
High Energy Ions ◽  
Diffraction Patterns ◽  
Dauphiné Twinning ◽  
Beam Damage

Using a Van De Graaff Accelerator thinned specimens were subjected to bombardment by 3 MeV N+ ions to fluences ranging from 4x1013 to 2x1016 ions/cm2. They were then examined by transmission electron microscopy and reflection electron diffraction using a 100 KV electron beam.At the lowest fluence of 4x1013 ions/cm2 diffraction patterns of the specimens contained Kikuchi lines which appeared somewhat broader and more diffuse than those obtained on unirradiated material. No damage could be detected by transmission electron microscopy in unannealed specimens. However, Dauphiné twinning was particularly pronounced after heating to 665°C for one hour and cooling to room temperature. The twins, seen in Fig. 1, were often less than .25 μm in size, smaller than those formed in unirradiated material and present in greater number. The results are in agreement with earlier observations on the effect of electron beam damage on Dauphiné twinning.

Examination of Extra Electron Diffraction Spots Observed in Deuterium-Irradiated Silicon by Using Parallel Electron Beam Illumination

1990 ◽  
Vol 48 (2) ◽  
pp. 490-491
Author(s):  
Ryuichiro Oshima ◽  
Shoichiro Honda ◽  
Tetsuo Tanabe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Silicon Single Crystal ◽  
Mixed Solution ◽  
Parallel Beam ◽  
Defect Clusters ◽  
Float Zone ◽  
Transmission Electron ◽  
Extra Electron ◽  
Diffraction Patterns

In order to examine the origin of extra diffraction spots and streaks observed in selected area diffraction patterns of deuterium irradiated silicon, systematic diffraction experiments have been carried out by using parallel beam illumination.Disc specimens 3mm in diameter and 0.5mm thick were prepared from a float zone silicon single crystal(B doped, 7kΩm), and were chemically thinned in a mixed solution of nitric acid and hydrogen fluoride to make a small hole at the center for transmission electron microscopy. The pre-thinned samples were irradiated with deuterium ions at temperatures between 300-673K at 20keV to a dose of 1022ions/m2, and induced lattice defects were examined under a JEOL 200CX electron microscope operated at 160kV.No indication of formation of amorphous was obtained in the present experiments. Figure 1 shows an example of defects induced by irradiation at 300K with a dose of 2xl021ions/m2. A large number of defect clusters are seen in the micrograph.

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