scholarly journals Twinning in Czochralski-Grown 36°-RY LiTaO3 Single Crystals

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1009
Author(s):  
Yutaka Ohno ◽  
Yuta Kubouchi ◽  
Hideto Yoshida ◽  
Toshio Kochiya ◽  
Tomio Kajigaya
Keyword(s):  
Single Crystals ◽  
Slip Plane ◽  
Edge Dislocation ◽  
Lithium Tantalate ◽  
Initiation Site ◽  
The Other ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Dislocation Arrays ◽  
Extension Direction

The origin of twinning during the Czochralski (CZ) growth of 36°-RY lithium tantalate (LiTaO3) single crystals is examined, and it is shown that lineages composed of dislocation arrays act as an initiation site for twinning. Two types of lineages expand roughly along three different {12¯10} planes and two different {11¯00} planes. The former lineages and some latter lineages are composed of two types of mixed-dislocations with different Burgers vectors, while the other lineages are composed of only one type of edge-dislocation. All the dislocations have the Burgers vector of ⟨12¯10⟩ type with the compression side at the +Z side. Twin lamellae on {101¯2} are generated at a lineage during the CZ growth. We have hypothesized that dislocations in the lineage with b = 1/3⟨12¯10⟩ change their extension direction along a slip plane of {101¯2}, and they dissociate into pairs of partial dislocations with b = 1/6⟨22¯01⟩and 1/6⟨02¯21¯⟩ forming twin lamellae on {101¯2}.

WORK HARDENING IN EASY GLIDE

1967 ◽  
Vol 45 (2) ◽  
pp. 765-775 ◽  
Author(s):  
P. M. Hazzledine
Keyword(s):  
Flow Stress ◽  
Slip Plane ◽  
Edge Dislocation ◽  
Work Hardening ◽  
Slip Line ◽  
Opposite Sign ◽  
Experimental Measurements ◽  
Line Pattern ◽  
Burgers Vector ◽  
Single Slip

A theory of single-slip work hardening is proposed, in which the flow stress is controlled by the stress required for one group of dislocations to pass another group with the same Burgers vector but with opposite sign on a parallel slip plane. The strain and the details of the slip-line pattern are calculated as a function of stress from the known properties of edge-dislocation multipoles. The predictions of the theory are compared with experimental measurements on Mg and are found to be in fair agreement.The theory presented is a highly simplified first version, and various possible developments of it are discussed.

CBED analysis of extended defects in melt-grown GaSe single crystals

1990 ◽  
Vol 48 (4) ◽  
pp. 494-495
Author(s):  
C. De Blasi ◽  
D. Manno
Keyword(s):  
Single Crystals ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Convergent Beam Electron Diffraction ◽  
Extended Defects ◽  
Burgers Vector ◽  
First Order ◽  
Partial Dislocations ◽  
Kinematical Condition ◽  
Convergent Beam

The study of dislocations and stacking faults in melt grown GaSe single crystals has been carried out by the Convergent Beam Electron Diffraction (CBED) technique.The presence of stacking faults induces distortions in the Kikuchi lines observed in the CBED transmitted disk. According to the kinematical condition of the stacking fault visibility, such lines show modifications when g·R is not integer, The displacement vector R has been determined by the analysis of the visibility and invisibility conditions in the transmitted disk, recorded according to the Tanaka method, The Burgers vector b of dislocations has been determined by the analysis of the modifications induced both in Kikuchi lines and in the First Order Laue Zone (FOLZ) reflections, observed in low camera length CBED patterns. Splitting and unsplitting of the reflections correspond to the visibility and invisibility of the dislocations in the kinematical approximation of diffraction contrast, The condition g·b = 0 is not strictly a sufficient condition for the vanishing of the modifications induced by the dislocation, neverthless it is generally very useful as a criterion for determining the direction of b, Moreover, some reflections g give g·b = ⅓ in the case of partial dislocations. This condition does not produce enough contrast to be detected, so that it is one more for the defect invisibility. The Thompson construction has been used in order to calculate the amplitude of b and to discriminate perfect or partial dislocations.

The role of structural imperfections in the photodimerization of 9-cyanoanthracene

1971 ◽  
Vol 324 (1559) ◽  
pp. 459-468 ◽  
Keyword(s):  
Fluorescence Microscopy ◽  
Excitation Energy ◽  
Slip Plane ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Structural Imperfections ◽  
Active Slip

Crystalline 9-cyanoanthracene undergoes photodimerization to give the trans dimer which is unexpected on the basis of the topochemical preformation theory. The possibility that the reaction occurs at defects is investigated; and the nature of the structural imperfections are described, as are also the types of product nuclei and their modes of growth. Interference-contrast and fluorescence microscopy have been employed for the examination of cleaved and partially dimerized faces of the monomer. It is shown that there is an active slip plane (221), and consideration of feasible dislocation reactions, particularly those involving unit strength dislocations which have a component of the Burgers vector in [100], reveals that, within stacking-fault regions (bounded by partial dislocations), the monomer molecules are in trans registry. It is suggested that molecules in such stacking faults act as traps for the excitation energy, and that reaction occurs at these sites.

Synchrotron Topography Studies of Growth and Deformation-Induced Dislocations in 4H-SiC

2012 ◽  
Vol 1433 ◽  
Author(s):  
M. Dudley ◽  
H. Wang ◽  
F. Wu ◽  
S. Byrappa ◽  
S. Shun ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Basal Plane ◽  
Partial Dislocation ◽  
Reversible Process ◽  
Burgers Vector ◽  
Shockley Partial ◽  
Partial Dislocations ◽  
Equilibrium Concentrations ◽  
Dislocation Multiplication

ABSTRACTSynchrotron topography studies are presented of the behavior of growth dislocations and deformation-induced dislocations in 4H-SiC single crystals. The growth dislocations include those in threading orientation with line directions approximately along c with Burgers vectors of a, c, and na+mc (where n and m are integers) while the deformation-induced dislocations include those with line directions confined to the basal plane with Burgers vectors of a and Shockley partial dislocations with Burgers vectors of 1/3<1-100> as well as those with line directions in the {1-100} prismatic planes with Burgers vectors of a. Processes leading to the nucleation of the growth dislocations are discussed as well as their deflection onto the basal plane during crystal growth in a reversible process. This latter process can lead to the conversion of segments of the deflected growth dislocations into deformation induced dislocations. In some cases this can lead to dislocation multiplication via the Hopping Frank-Read source mechanism and in others to the motion of single Shockley partial dislocations leading to Shockley stacking fault expansion. Studies are also presented of interactions between threading growth dislocations with c-component of Burger’s vector facilitated by climb processes which are mediated by interactions with non-equilibrium concentrations of vacancies. This can lead to reactions whereby complete or partial dislocation Burgers vector annihilation occurs.

Twinning and crystal slip in black monoclinic ZnP2

1986 ◽  
Vol 1 (1) ◽  
pp. 187-192 ◽  
Author(s):  
Michael E. Fleet ◽  
Joseph C. White
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Slip Plane ◽  
Cell Parameter ◽  
Twin Plane ◽  
Stacking Fault ◽  
Orthorhombic Unit Cell ◽  
Partial Dislocations ◽  
Parameter Ratio ◽  
Monoclinic Cell

Monoclinic βZnP2 (black ZnP2) single crystals, synthesized in the presence of excess P, contain regions of polysynthetic lamellar-twinned structure, with dislocations and stacking fault-like features. The twin law is a* twin axis, (100) composition plane: (100) is also the slip plane. The twin composition plane migrates across (100) lattice fringes. In the revised βZnP2 crystal structure, Zn(1) and P(4) positions are related across a (100) twin composition plane at x = 0.84 by two twin operations, with axes through is also a possible slip plane, with three partial dislocations, ½[001], ½[001], and ½[001]. A third possible twin operation relates Zn(2) and P(1) positions across a (100) twin plane at x = 0.5, with twin axis through All twin and slip operations result in very little distortion in nearest- and nextnearest-neighbor coordination geometries. Twin and stacking fault mistakes may be facilitated by approach of the monoclinic cell parameter ratio c[α sin(β — π/2)] to 4 (which yields a pseudo-orthorhombic unit cell) and by Zn1-xP2 nonstoichiometry.

Determination of the Burgers vector of a dislocation in a Fe-Mn alloy by weak-beam image in HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 330-331
Author(s):  
Y. Ishida ◽  
H. Ishida ◽  
K. Kohra ◽  
H. Ichinose
Keyword(s):  
High Order ◽  
Simulation Technique ◽  
The Other ◽  
Image Simulation ◽  
Diffraction Vector ◽  
Burgers Vector ◽  
Weak Beam ◽  
Beam Image ◽  
Edge Component

IntroductionA simple and accurate technique to determine the Burgers vector of a dislocation has become feasible with the advent of HVEM. The conventional image vanishing technique(1) using Bragg conditions with the diffraction vector perpendicular to the Burgers vector suffers from various drawbacks; The dislocation image appears even when the g.b = 0 criterion is satisfied, if the edge component of the dislocation is large. On the other hand, the image disappears for certain high order diffractions even when g.b ≠ 0. Furthermore, the determination of the magnitude of the Burgers vector is not easy with the criterion. Recent image simulation technique is free from the ambiguities but require too many parameters for the computation. The weak-beam “fringe counting” technique investigated in the present study is immune from the problems. Even the magnitude of the Burgers vector is determined from the number of the terminating thickness fringes at the exit of the dislocation in wedge shaped foil surfaces.

scholarly journals Probing anisotropic mechanical behaviour in carbamazepine form III

CrystEngComm ◽  
2021 ◽  
Author(s):  
Benjamin P. A. Gabriele ◽  
Craig J. Williams ◽  
Matthias E. Lauer ◽  
Brian Derby ◽  
Aurora J. Cruz-Cabeza
Keyword(s):  
Single Crystals ◽  
Slip Plane ◽  
Mechanical Behaviour ◽  
Molecular Simulations ◽  
Afm Imaging

Nanoindentation measurements in single crystals of carbamazepine form III show that the (020) face is stiffer and harder than the (002) and (101) faces. AFM imaging and molecular simulations reveal that the (020) plane is the most likely slip plane.

A comparative study on the domain switching characteristics of near stoichiometric lithium niobate and lithium tantalate single crystals

2005 ◽  
Vol 120 (1-3) ◽  
pp. 125-129 ◽  
Author(s):  
S. Ganesamoorthy ◽  
M. Nakamura ◽  
S. Takekawa ◽  
S. Kumaragurubaran ◽  
K. Terabe ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Comparative Study ◽  
Single Crystals ◽  
Domain Switching ◽  
Lithium Tantalate ◽  
Switching Characteristics

Effect of Hydrostatic Pressure on Geometry of Slip in Silicon Iron Single Crystals

1983 ◽  
Vol 22 ◽  
Author(s):  
A.V. Dobromyslov ◽  
G.V. Dolgikh ◽  
N.I. Talutz ◽  
V.T. Shmatov ◽  
B. I. Beresnev
Keyword(s):  
Hydrostatic Pressure ◽  
Single Crystals ◽  
Slip Plane ◽  
Special Structure ◽  
Normal Stresses ◽  
Silicon Iron ◽  
Screw Dislocations ◽  
Effect Of Pressure ◽  
Effect Of Hydrostatic Pressure

ABSTRACTThe effect of the pressure 550MPa on the choice of the acting slip plane in the single crystals of Fe−2,9%Si was studied. It was established that the presence of pressure resulted in the increase of the slip asymmetry. The effect of pressure is attributed to the action of normal stresses and to the special structure of screw dislocations.

Sign in / Sign up

Export Citation Format

Share Document