Dislocation Structure of 10° Low-Angle Tilt Grain Boundary in α-Al2O3

2007 ◽  
Vol 558-559 ◽  
pp. 979-982 ◽  
Author(s):  
E. Tochigi ◽  
A. Nakamura ◽  
Naoya Shibata ◽  
Takahisa Yamamoto ◽  
K.P.D. Lagerlöf ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Dislocation Structure ◽  
High Resolution Electron Microscopy ◽  
Stacking Fault ◽  
Partial Dislocations ◽  
Resolution Electron ◽  
Tilt Grain Boundary ◽  
Α Al2o3 ◽  
Repulsive Forces ◽  
Edge Dislocations

Dislocation structure of 10º low-angle tilt grain boundary in α-Al2O3 has been observed by high-resolution electron microscopy (HRTEM). It was found that perfect <1120> edge dislocations, which are introduced to compensate the misorientation, dissociated into two mixed partial dislocations with {1120} stacking-fault in between. The distances between the two partials were estimated by the force balances between repulsive forces of periodical dislocations and attractive forces from stacking-fault. The stacking-fault energy for 10o low-angle tilt grain boundary was estimated to be much higher than the previously reported value.

Σ =13 tilt grain boundary in silicon bicrystal

1990 ◽  
Vol 48 (4) ◽  
pp. 562-563
Author(s):  
M.J. Kim ◽  
Y.L. Chen ◽  
R.W. Carpenter ◽  
J.C. Barry ◽  
G.H. Schwuttke
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Rotation Axis ◽  
Czochralski Method ◽  
High Resolution Electron Microscopy ◽  
Image Simulation ◽  
Simulation Techniques ◽  
Resolution Electron ◽  
The Common ◽  
Tilt Grain Boundary

The structure of grain boundaries (GBs) in metals, semiconductors and ceramics is of considerable interest because of their influence on physical properties. Progress in understanding the structure of grain boundaries at the atomic level has been made by high resolution electron microscopy (HREM) . In the present study, a Σ=13, (510) <001>-tilt grain boundary in silicon was characterized by HREM in conjunction with digital image processing and computer image simulation techniques.The bicrystals were grown from the melt by the Czochralski method, using preoriented seeds. Specimens for TEM observations were cut from the bicrystals perpendicular to the common rotation axis of pure tilt grain boundary, and were mechanically dimpled and then ion-milled to electron transparency. The degree of misorientation between the common <001> axis of the bicrystal was measured by CBED in a Philips EM 400ST/FEG: it was found to be less than 1 mrad. HREM was performed at 200 kV in an ISI-002B and at 400 kv in a JEM-4000EX.

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

1990 ◽  
Vol 48 (1) ◽  
pp. 52-53 ◽  
Author(s):  
Jean-Luc Rouvière ◽  
Alain Bourret
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Structural Transformation ◽  
Mirror Symmetry ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Covalent Bonds ◽  
Resolution Electron ◽  
Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

High-Resolution Electron Microscopy Observations of Grain-Boundary Films in Silicon Nitride Ceramics

1992 ◽  
Vol 287 ◽  
Author(s):  
H.-J. Kleebe ◽  
M. K. Cinibulk ◽  
I. Tanaka ◽  
J. Bruley ◽  
R. M. Cannon ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Silicon Nitride ◽  
High Resolution ◽  
Grain Boundary ◽  
Film Thickness ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Nitride Ceramics ◽  
Boundary Films ◽  
Repulsive Forces

ABSTRACTCharacterization of silicon nitride ceramics by transmission electron microscopy (TEM) provides structural and compositional information on intergranular phases necessary to elucidate the factors that can influence the presence and thickness of grain-boundary films. Different TEM techniques can be used for the detection and determination of intergranular-film thickness, however, the most accurate results are obtained by high-resolution electron microscopy (HREM). HREM studies were applied, in conjunction with analytical electron microscopy, to investigate the correlation between intergranular-phase composition and film thickness. Statistical analyses of a number of grain-boundary films provided experimental verification of a theoretical equilibrium film thickness. Model experiments on a high-purity Si3N4 material, doped with low amounts of Ca, suggest the presence of two repulsive forces, a steric force and a force produced by an electrical double layer, that may act to balance the attractive van der Waals force necessary to establish an equilibrium film thickness.

Dislocation Structure Analysis of Low Angle Tilt Grain Boundaries in Alumina by Elastic Theory

2007 ◽  
Vol 561-565 ◽  
pp. 2465-2468
Author(s):  
Atsutomo Nakamura ◽  
E. Tochigi ◽  
Naoya Shibata ◽  
Takahisa Yamamoto ◽  
Yuichi Ikuhara
Keyword(s):  
Grain Boundaries ◽  
Structure Analysis ◽  
Dislocation Structure ◽  
Stacking Fault ◽  
Elastic Theory ◽  
Partial Dislocations ◽  
Edge Dislocations ◽  
Fault Region

Structure and configuration of boundary dislocations on the low angle tilt grain boundaries in alumina were considered based on the ideas that the boundary is composed of regularly arrayed edge dislocations and that the dislocations could dissociate into partial dislocations as well as glide dislocations in bulk. Moreover, the structure of the dissociated boundary dislocations were evaluated by the calculations based on an elastic theory. The calculations indicated that the largeness of the stacking fault region between partial dislocations formed by the dissociation will decrease with increasing tilt angles. It can be said that the idea and calculations used here will be powerful in considering the dislocation structure of low angle tilt grain boundaries that are not or are difficult to be identified.

Structural variability of edge dislocations in a SrTiO3 low-angle [001] tilt grain boundary

2009 ◽  
Vol 24 (7) ◽  
pp. 2191-2199 ◽  
Author(s):  
James P. Buban ◽  
Miaofang Chi ◽  
Daniel J. Masiel ◽  
John P. Bradley ◽  
Bin Jiang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Scanning Transmission Electron Microscopy ◽  
Spherical Aberration ◽  
Structural Variations ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Tilt Grain Boundary ◽  
Edge Dislocations ◽  
Electron Energy Loss

Using a spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS), we investigated a 6° low-angle [001] tilt grain boundary in SrTiO3. The enhanced spatial resolution of the aberration corrector leads to the observation of a number of structural variations in the edge dislocations along the grain boundary that neither resemble the standard edge dislocations nor partial dislocations for SrTiO3. Although there appear to be many variants in the structure that can be interpreted as compositional effects, three main classes of core structure are found to be prominent. From EELS analysis, these classifications seem to be related to Sr deficiencies, with the final variety of the cores being consistent with an embedded TiOx rocksalt-like structure.

Atomic Structure of 66° [110] Asymmetric Tilt Grain Boundary in Aluminum

1996 ◽  
Vol 466 ◽  
Author(s):  
M. Shamsuzzoha ◽  
P. A. Deymier ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
High Resolution Electron Microscopy ◽  
Structural Features ◽  
Resolution Electron ◽  
Cold Rolling And Annealing ◽  
Line Defects ◽  
Tilt Grain Boundary ◽  
Straight Segments

ABSTRACTA 66° [110] asymmetric tilt grain boundary in Al prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. Due to a 4.5° deviation from the perfect Σ3 misorientation, the boundary is heavily faceted with straight segments running parallel to (111) and (112) planes. All atomic sites across the (111) facets appear to be coincident with the (111) planes at an angle of 66°. The line defects which accommodate the deviation from the perfect twin orientation result in grain boundary stepping. The observed structural features can be described in terms of secondary grain boundary dislocations with Burgers vectors of the type ⅓<111>, and ⅙<112> as well as their interactions.

Structural Study of a [100] 45° Twist Plus 7.5° Tilt Grain Boundary in Aluminium by HREM

1999 ◽  
Vol 589 ◽  
Author(s):  
M. Shamsuzzoha ◽  
P. A. Deymier ◽  
David J. Smith
Keyword(s):  
Grain Boundary ◽  
High Resolution Electron Microscopy ◽  
Image Features ◽  
Boundary Structure ◽  
High Concentration ◽  
Atomic Column ◽  
Resolution Electron ◽  
Cold Rolling And Annealing ◽  
Tilt Grain Boundary ◽  
Local Relaxation

AbstractA [100] 45° twist plus 7.5° tilt grain boundary in aluminium prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. The direct interpretability of the image features in terms of atomic column positions allows structural models of the grain boundary to be developed. The boundary exibits a high concentration of steps due to the 7.5° tilt from a perfect [100] 45° quasiperiodic misorientation. Occurrence of co-incidence and pseudo co-incidence of atomic planes across the interface appears to play an important role in the formation of steps along this boundary. Local relaxation of atoms resulting from the perturbation of the [100] 45° twist bi-crystal determines the boundary structure

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