scholarly journals Determination of the Formation of the 1/6[031] Extrinsic Stacking Faults in Deformed YBa2Cu3O7−δ

1990 ◽  
Vol 183 ◽  
Author(s):  
M. J. Kramer ◽  
E. P. Kvam ◽  
L. S. Chumbley
Keyword(s):  
High Temperature ◽  
High Temperature Superconductor ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Processing Conditions ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Edge Dislocations ◽  
Image Simulations

AbstractMechanial deformation of the YBa2Cu3O7−δ high temperature superconductor under a number of different processing conditions resulted in the formation of <100> and <110> edge dislocations, both having a (001) slip plane. Subsequent high temperature annealing at 900°C resulted in the formation of extrinsic stacking faults with a large separation of the partial dislocations, up to 0.35 μm, suggesting a very low minimum stacking fault energy of 1.2 × 10−2 J/m2. High resolution transmission electron microscopy (HRTEM) in conjunction with image simulations revealed that the stacking faults were comprised of an extra CuO plane between the Ba layers with an offset of b/2. The stacking fault vector of 1/6[031] requires some separation of the <010> Burgers vectors into the c-axis direction. A model in which [010] separates into 1/6[031] + 1/[031] is consistent with the observed stacking faults.

Dislocations and stacking faults in stainless steel

1957 ◽  
Vol 240 (1223) ◽  
pp. 524-538 ◽  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steel ◽  
Grain Boundaries ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Thin Sections ◽  
Partial Dislocations ◽  
Transmission Electron

Further experiments by transmission electron microscopy on thin sections of stainless steel deformed by small amounts have enabled extended dislocations to be observed directly. The arrangement and motion of whole and partial dislocations have been followed in detail. Many of the dislocations are found to have piled up against grain boundaries. Other observations include the formation of wide stacking faults, the interaction of dislocations with twin boundaries, and the formation of dislocations at thin edges of the foils. An estimate is made of the stacking-fault energy from a consideration of the stresses present, and the properties of the dislocations are found to be in agreement with those expected from a metal of low stacking-fault energy.

Three-dimensional reciprocal space mapping with a two-dimensional detector as a low-latency tool for investigating the influence of growth parameters on defects in semipolar GaN

2015 ◽  
Vol 48 (4) ◽  
pp. 1000-1010 ◽  
Author(s):  
Sondes Bauer ◽  
Sergey Lazarev ◽  
Martin Bauer ◽  
Tobias Meisch ◽  
Marian Caliebe ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Stacking Faults ◽  
Vapour Phase ◽  
Stacking Fault ◽  
Space Mapping ◽  
Reciprocal Space ◽  
Reciprocal Space Mapping ◽  
Partial Dislocations ◽  
Semipolar Gan

A rapid nondestructive defect assessment and quantification method based on X-ray diffraction and three-dimensional reciprocal-space mapping has been established. A fast read-out two-dimensional detector with a high dynamic range of 20 bits, in combination with a powerful data analysis software package, is set up to provide fast feedback to crystal growers with the goal of supporting the development of reduced defect density GaN growth techniques. This would contribute strongly to the improvement of the crystal quality of epitaxial structures and therefore of optoelectronic properties. The method of normalized three-dimensional reciprocal-space mapping is found to be a reliable tool which shows clearly the influence of the parameters of the metal–organic vapour phase epitaxial and hydride vapour phase epitaxial (HVPE) growth methods on the extent of the diffuse scattering streak. This method enables determination of the basal stacking faults and an exploration of the presence of other types of defect such as partial dislocations and prismatic stacking faults. Three-dimensional reciprocal-space mapping is specifically used in the manuscript to determine basal stacking faults quantitatively and to discuss the presence of partial dislocations. This newly developed method has been applied to semipolar GaN structures grown on patterned sapphire substrates (PSSs). The fitting of the diffuse scattering intensity profiles along the stacking fault streaks with simulations based on a Monte Carlo approach has delivered an accurate determination of the basal plane stacking fault density. Three-dimensional reciprocal-space mapping is shown to be a method sensitive to the influence of crystallographic surface orientation on basal stacking fault densities during investigation of semipolar (11{\overline 2}2) GaN grown on anr-plane (1{\overline 1}02) PSS and semipolar (10{\overline 1}1) GaN grown on ann-plane (11{\overline 2}3) PSS. Moreover, the influence of HVPE overgrowth at reduced temperature on the quality of semipolar (11{\overline 2}2) GaN has been studied.

Analysis of Weak-Beam Contrast from SESF/SISF Fault Pairs Associated with ½ <112] Superdislocations in TiAl

1998 ◽  
Vol 552 ◽  
Author(s):  
Mukul Kumar ◽  
S. Sriram ◽  
Adam J. Schwartz ◽  
Vijay K. Vasudevan
Keyword(s):  
Stacking Faults ◽  
Antiphase Boundary ◽  
Stacking Fault ◽  
Intermetallic Alloy ◽  
Diffraction Contrast ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Beam Transmission ◽  
Simulated Images

ABSTRACTThe diffraction contrast from dissociated ½<112] superdislocations in γ-TiAl intermetallic alloy cannot always be analyzed using conventional rules of diffraction contrast. In particular, the configuration involving three similar Shockley partials on adjacent planes has often been ruled out due to the absence of fringes indicating the presence of stacking faults. In order to determine the dissociated configuration, weak-beam transmission electron microscope observations of edge-oriented ½<112] superdislocations have been correlated with computer simulated images. Dissociation of these superdislocations into three similar ⅙<112] partial dislocations bounding a superlattice extrinsic and intrinsic stacking fault pair has been consequently determined from these analyses. It has been found that diffraction contrast alone cannot distinguish between the various configurations that lead to the formation of the fault pair, but the formation of an antiphase boundary or complex stacking fault linked dissociation or locking by stair rod dislocations can be ruled out.

On the determination of stacking-fault energy from dislocation nodes observed by TEM

1994 ◽  
Vol 52 ◽  
pp. 686-687
Author(s):  
Paulo J. Ferreira
Keyword(s):  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Radius Of Curvature ◽  
Bright Field ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Fundamental Understanding ◽  
Line Direction

A fundamental understanding of the mechanical and physical behaviour of metals requires a knowledge of the stacking-fault energy (SFE). This aspect is important because the possibility of cross-slip and thus plastic deformation is a function of the SFE of the material. Impurities may segregate to the faults and change the SFE, which may affect the mechanical behaviour. For low SFE’s materials, the SFE can be determined rather accurately from transmission electron microscopy evaluation of the radius of curvature of dislocation nodes formed by the attractive interaction of dislocations (Fig. 1).This work is directed towards applying the T.E.M. technique to determine the SFE of a 310S stable austenitic stainless steel. The specimens were observed in a JEOL 4000 microscope operated at an accelerating voltage of 200 kV, and equipped with a double tilt stage. Conventional two beam bright field images were used to determine the Burgers vector and line direction of the partial dislocations.

Stacking Fault Formation via 2D Nucleation in PVT Grown 4H-SiC

2015 ◽  
Vol 821-823 ◽  
pp. 85-89 ◽  
Author(s):  
Fang Zhen Wu ◽  
Huan Huan Wang ◽  
Yu Yang ◽  
Jian Qiu Guo ◽  
Balaji Raghothamachar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Opposite Sign ◽  
Stacking Faults ◽  
Stacking Fault ◽  
X Ray ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Structure Simulation ◽  
Simulation Results ◽  
Polytype Structure

Synchrotron white beam x-ray topography (SWBXT), synchrotron monochromatic beam x-ray topography (SMBXT), and high resolution transmission electron microscopy (HRTEM) studies have been carried out on stacking faults in PVT grown 4H-SiC crystal. Their fault vectors were determined by SWBXT to be 1/3<-1100>, 1/2<0001>, 1/6<-2203>, 1/12<4-403>, 1/12<-4403>. HRTEM studies reveal their similarity in stacking sequences as limited numbers of bilayers of 6H polytype structure. Simulation results of the two partial dislocations associated with the stacking faults in SMBXT images reveal the opposite sign nature of their Burgers vectors. A mechanism for stacking fault formation via 2D nucleation is postulated.

On effects of non-systematic reflections on weak-beam images of partial dislocations

1991 ◽  
Vol 49 ◽  
pp. 688-689
Author(s):  
K. Z. Botros ◽  
S. S. Sheinin
Keyword(s):  
High Precision ◽  
Stacking Fault ◽  
Important Application ◽  
Stacking Fault Energy ◽  
Sharp Peak ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Deviation Parameter ◽  
Beam Diffraction

The main features of weak beam images of dislocations were first described by Cockayne et al. using calculations of intensity profiles based on the kinematical and two beam dynamical theories. The feature of weak beam images which is of particular interest in this investigation is that intensity profiles exhibit a sharp peak located at a position very close to the position of the dislocation in the crystal. This property of weak beam images of dislocations has an important application in the determination of stacking fault energy of crystals. This can easily be done since the separation of the partial dislocations bounding a stacking fault ribbon can be measured with high precision, assuming of course that the weak beam relationship between the positions of the image and the dislocation is valid. In order to carry out measurements such as these in practice the specimen must be tilted to "good" weak beam diffraction conditions, which implies utilizing high values of the deviation parameter Sg.

Structure of stacking faults in pyrite using TEM techniques

1992 ◽  
Vol 50 (1) ◽  
pp. 358-359
Author(s):  
Raja Subramanian ◽  
Kenneth S. Vecchio
Keyword(s):  
Lattice Structure ◽  
Stacking Faults ◽  
Covalent Bond ◽  
Group Symmetry ◽  
Iron Pyrite ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Contrast Analysis ◽  
Chlorine Ions

The structure of stacking faults and partial dislocations in iron pyrite (FeS2) have been studied using transmission electron microscopy. Pyrite has the NaCl structure in which the sodium ions are replaced by iron and chlorine ions by covalently-bonded pairs of sulfur ions. These sulfur pairs are oriented along the <111> direction. This covalent bond between sulfur atoms is the strongest bond in pyrite with Pa3 space group symmetry. These sulfur pairs are believed to move as a whole during dislocation glide. The lattice structure across these stacking faults is of interest as the presence of these stacking faults has been preliminarily linked to a higher sulfur reactivity in pyrite. Conventional TEM contrast analysis and high resolution lattice imaging of the faulted area in the TEM specimen has been carried out.

Structure determination of the new high-temperature superconductor Y2Ba4Cu7O14+x

Nature ◽  
1988 ◽  
Vol 334 (6183) ◽  
pp. 596-598 ◽  
Author(s):  
P. Bordet ◽  
C. Chaillout ◽  
J. Chenavas ◽  
J. L. Hodeau ◽  
M. Marezio ◽  
...  
Keyword(s):  
High Temperature ◽  
Structure Determination ◽  
High Temperature Superconductor

The mechanisms of plastic deformation of rapidly solidified Al3Ti and Al67Ni8Ti25 intermetallic compounds.

1988 ◽  
Vol 133 ◽  
Author(s):  
Vijay K. Vasudevan ◽  
Robert Wheeler ◽  
Hamish L. Fraser
Keyword(s):  
Room Temperature ◽  
Considerable Increase ◽  
Stacking Faults ◽  
Temperature Deformation ◽  
Deformation Microstructure ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
The Mean ◽  
Rapidly Solidified ◽  
Mechanisms Of Plastic Deformation

ABSTRACTThe dislocation structures in rapidly solidified Al3Ti with the DO22 structure and the ternary Al-25Ti-8Ni (at.%) alloy with the L12 structure deformed in compression in the temperature range of 25 to 800°C have been studied by transmission electron microscopy. The room temperature deformation microstructure of the Al3Ti compound is characterized by the presence of stacking faults/order twins on {111} planes bounded by partial dislocations with Burgers vector b=1/6<112], as reported by others. At intermediate temperatures, besides the stacking faults, slip is also observed as bands on the {001] plane delineated by dislocations with b=1/2<110] which bound APB's. At 600°C, the reported increase in ductility is associated here with additional slip on the {001)<110], {001)[100] and {001)[010] systems. Dislocations with b=<110] exist as pairs of partial dislocations with b=1/2<110] connected by APB's. The mean separation between the partials was measured to be 30 nm, corresponding to an APB energy of ≍32 mJ.m-2 on the (001) plane. Observations also indicate that the APB energy is anisotropic, i.e., is considerably higher on the {111} planes compared to the {001) plane. The deformation microstructure of the Al-25Ti-8Ni L12 alloy is characterized by slip of dislocations with b=<110> gliding on {111} planes, a major fraction of which exist as dipoles. Following deformation at 300°C, there is essentially no evidence of dissociation of these dislocations, although some dissociated dislocations on (001) having b=l/2<110> are also observed. With an increase in temperature, there is a considerable increase in dislocation activity and strong evidence for 1/2<110> dissociated dislocations is present.

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