Tailoring Microstructures Under Strong Non-Equilibrium Conditions: A Feasible Path Towards High JC in Melt Textured YBa2Cu3O7

2000 ◽  
Vol 659 ◽  
Author(s):  
Felip Sandiumenge ◽  
Jérôme Plain ◽  
Teresa Puig ◽  
Xavier Obradors ◽  
Jacques Rabier ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Partial Dislocation ◽  
Enhancement Factor ◽  
Stacking Faults ◽  
Equilibrium Conditions ◽  
Pinning Centers ◽  
Partial Dislocations ◽  
High Oxygen Pressure ◽  
Density Analysis ◽  
Feasible Path

ABSTRACTMelt textured YBa2Cu3O/Y2BaCuO5 were post processed by high oxygen pressure for different periods and temperatures. This process permits the control of the microstructure, in particular the growth and shape of the stacking faults and thereby the partial dislocation density. Analysis of the Jc(H,T) behavior allow to separate the contribution of Y2BaCuO5 interface from that of dislocations. It is shown that the in-plane partial dislocations act as point-like pinning centers increasing Jc up to 180% but this enhancement factor is counterbalanced by the effect of the stacking faults associated to the partial dislocations.

Evolution of Threading Edge Dislocations at Earlier Stages of PVT Growth for 4H-SiC Single Crystals

2016 ◽  
Vol 858 ◽  
pp. 73-76 ◽  
Author(s):  
Komomo Tani ◽  
Tatsuo Fujimoto ◽  
Kazuhito Kamei ◽  
Kazuhiko Kusunoki ◽  
Kazuaki Seki ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Sharp Increase ◽  
Grown Crystal ◽  
Stacking Faults ◽  
Dislocation Network ◽  
Two Dimensional ◽  
Partial Dislocations ◽  
Plane Distribution ◽  
Edge Dislocations ◽  
Crystal Interface

Dislocation structures at the seed/grown-crystal interface in PVT-grown 4H-SiC crystals are investigated. The dislocation density is found to show a sharp increase at the interface and its main contribution is probably ascribable to TEDs which stem from BPDs generating at the interface through the structural transformation. Intense TEM observations reveal an intriguing in-plane distribution structure of the interface BPDs; the BPDs form a two-dimensional dislocation network comprising of {-1100} partial dislocations associated with expanded areas of stacking faults at the nodes of the network.

Densification Behavior in Spark-Plasma-Sintering of MgAl2O4 Spinel

2010 ◽  
Vol 654-656 ◽  
pp. 1986-1989
Author(s):  
Koji Morita ◽  
Byung Nam Kim ◽  
Hidehiro Yoshida ◽  
Keijiro Hiraga
Keyword(s):  
Effective Stress ◽  
Partial Dislocation ◽  
Stacking Faults ◽  
Dislocation Motion ◽  
Densification Rate ◽  
Densification Mechanism ◽  
Partial Dislocations ◽  
Plasma Sintering ◽  
Rate Relationship ◽  
Spark Plasma

The densification mechanism in park-plasma-sintering (SPS) processing was examined in MgAl2O4 spinel. As the relative density ρt increases, that is, as the effective stress σeff decreases, stress exponent n evaluated from effective stress-densification rate relationship continuously varies from n  4 to n  1. TEM observation shows that significant stacking faults caused by partial dislocations are frequently observed in the low ρt region. The results suggest that, for spinel, the predominant densification mechanism in SPS processing changes with ρt from plastic flow by a partial dislocation motion in the low ρt region (n  4) to diffusion-related creep in the high ρt region (n  1).

Stacking faults and dislocations in titanium dioxide, with special reference to non-stoichiometry

1963 ◽  
Vol 276 (1367) ◽  
pp. 542-552 ◽  
Keyword(s):  
Titanium Dioxide ◽  
Partial Dislocation ◽  
Stoichiometric Composition ◽  
Stacking Faults ◽  
Dislocation Loops ◽  
Microscopical Investigation ◽  
Burgers Vector ◽  
Vacancy Clusters ◽  
Partial Dislocations ◽  
Electron Microscopical

A detailed electron microscopical investigation has been made of the stacking faults and dislocations observed in thin films of titanium dioxide grown on the (100) faces of titanium carbide crystals. The large stacking faults formed during the growth process lie on a {101} plane, but they often change from one plane to another of the same family, sometimes on too fine a scale to be clearly resolved. The fault is terminated by a partial dislocation having a vector of the 1/2<101>-type; if the specimen is heated in the microscope, when it becomes non-stoichiometric, the fault anneals out by one of two mechanisms. The first mechanism involves the glide of the partial dislocation terminating the fault, and the second the growth of small dislocation loops formed by the condensation of vacancies introduced as a result of deviations from the stoichiometric composition. Contrast experiments show that the observed dislocations are of two types. The first are dissociated dislocations having a partial 1/2<101> vector, glissile on {101} planes and associated with a stacking fault. The second type of dislocation are undissociated and have a <001> Burgers vector. A sessile configuration is also formed by an interaction between dislocations with 1/2<101> and <001> and Burgers vector. An interaction between glissile partial dislocations and vacancy clusters also occurs, and it is suggested that this is a possible mechanism for the increased yield stress produced when TiO 2 becomes substoichiometric.

The study of defects in Sb2S3 by method of direct lattice resolution

1978 ◽  
Vol 36 (1) ◽  
pp. 312-313
Author(s):  
V.M. Kosevich ◽  
A.A. Sokol ◽  
A.G. Bagmut
Keyword(s):  
Defect Structure ◽  
Partial Dislocation ◽  
Stacking Faults ◽  
Substrate Plane ◽  
Partial Dislocations ◽  
Displacement Vectors ◽  
Initial Stage ◽  
Direct Lattice ◽  
Lattice Resolution ◽  
Deposited Films

1.Sb2S3 has the orthorombic lattice with a=11,23;b=11,31; c=3,84 Å. Its crystal structure is constructed of the double ribbons of antimony and sulphur atoms,parallel to [00l].Vacuum deposited films of Sb2S3 re amorphous{they were crystallyzed in spherolite mode by the electronbeam heating.The study of defect structure of the Sb2S3 spherolite crystals by method of direct lattice resolution was the aim of present work.The images of (100),(200),(010),(020),(110) and (110) planes were obtained.2.Several types of the ribbons stacking faults were obserwed in Sb2S3 crystals with (001) parallel to the substrate plane (Fig.1).The stac-kingfault planes and their displacement vectors R are the following: a) (010),(110),R=1/2 [010];b) (100),R=1/2 [210],R=1/4[210].3.There were obtained the images of partial dislocations with b=1/2 [010] and small-andle boundaries,consisted of the dissociated partial dislocation pairs,in Sb2s3 crystals with (100) and (010) planes parallel to the substrate.Small-angle boundaries appeared on initial stage of the spherolite growth,when splitting of spherolite single-crystal nucleus was taking place (Fig.2).

scholarly journals Generating gradient germanium nanostructures by shock-induced amorphization and crystallization

2017 ◽  
Vol 114 (37) ◽  
pp. 9791-9796 ◽  
Author(s):  
Shiteng Zhao ◽  
Bimal Kad ◽  
Christopher E. Wehrenberg ◽  
Bruce A. Remington ◽  
Eric N. Hahn ◽  
...  
Keyword(s):  
Partial Dislocation ◽  
Stacking Faults ◽  
Surface Region ◽  
Planar Defects ◽  
Partial Dislocations ◽  
Structural And Functional Properties ◽  
Properties Of Materials ◽  
Dynamics Simulations ◽  
Shock Stress ◽  
Complex Gradient

Gradient nanostructures are attracting considerable interest due to their potential to obtain superior structural and functional properties of materials. Applying powerful laser-driven shocks (stresses of up to one-third million atmospheres, or 33 gigapascals) to germanium, we report here a complex gradient nanostructure consisting of, near the surface, nanocrystals with high density of nanotwins. Beyond there, the structure exhibits arrays of amorphous bands which are preceded by planar defects such as stacking faults generated by partial dislocations. At a lower shock stress, the surface region of the recovered target is completely amorphous. We propose that germanium undergoes amorphization above a threshold stress and that the deformation-generated heat leads to nanocrystallization. These experiments are corroborated by molecular dynamics simulations which show that supersonic partial dislocation bursts play a role in triggering the crystalline-to-amorphous transition.

Interaction between Recombination Enhanced Dislocation Glide Process Activated Basal Stacking Faults and Threading Dislocations in 4H-Silicon Carbide Epitaxial Layers

2007 ◽  
Vol 994 ◽  
Author(s):  
Yi Chen ◽  
Michael Dudley ◽  
Kendrick X Liu ◽  
Robert E Stahlbush
Keyword(s):  
Silicon Carbide ◽  
Partial Dislocation ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Epitaxial Layers ◽  
Threading Dislocations ◽  
Screw Dislocations ◽  
Dislocation Glide ◽  
Shockley Partial ◽  
Partial Dislocations

AbstractElectron-hole recombination enhanced glide of Shockley partial dislocations bounding expanding stacking faults and their interactions with threading dislocations in 4H silicon carbide epitaxial layers have been studied using synchrotron white beam X-ray topography and in situ electroluminescence. The mobile silicon-core Shockley partial dislocations bounding the stacking faults are able to cut through threading edge dislocations leaving no trailing dislocation segments in their wake. However, when the Shockley partial dislocations interact with threading screw dislocations, trailing 30o partial dislocation dipoles are initially deposited in their wake due to the pinning effect of the threading screw dislocations. These dipoles spontaneously snap into their screw orientation, regardless the normally immobile carbon-core Shockley partial dislocation components in the dipoles. They subsequently cross slip and annihilate, leaving a prismatic stacking fault in (2-1-10) plane with the displacement vector 1/3[01-10].

Densification Mechanism of MgAl2O4 Spinel during Spark-Plasma-Sintering

2010 ◽  
Vol 63 ◽  
pp. 62-67
Author(s):  
Koji Morita ◽  
Byung Nam Kim ◽  
Hidehiro Yoshida ◽  
Keijiro Hiraga ◽  
Yoshio Sakka
Keyword(s):  
High Purity ◽  
Partial Dislocation ◽  
Stacking Faults ◽  
Dislocation Motion ◽  
Densification Behavior ◽  
Densification Rate ◽  
Densification Mechanism ◽  
Partial Dislocations ◽  
Plasma Sintering ◽  
Spark Plasma

The densification mechanism during the park-plasma-sintering (SPS) processing was examined in high purity MgAl2O4 spinel. As the density ρt increases, that is, as the effective stress σeff decreases, stress exponent n evaluated from σeff dependence of densification rate varies from n ≥ 4 in the low ρt region, n ≈ 2 in the intermediate ρt region to n ≈ 1 in the high ρt region. TEM observation shows that significant stacking faults caused by partial dislocations are observed in the low ρt region, but limited in the high ρt region. The ρt dependent densification behavior and microstructure suggest that the predominant densification mechanism during the SPS processing changes with ρt from plastic flow by partial dislocation motion for the low ρt region (n ≥ 4) to diffusion-related creep for the high ρt region (n ≈ 1).

Controlling Planar Defects in 3C-SiC: Ways to Wake it up as a Practical Semiconductor

2015 ◽  
Vol 821-823 ◽  
pp. 108-114 ◽  
Author(s):  
Hiroyoki Nagasawa ◽  
Ramya Gurunathan ◽  
Maki Suemitsu
Keyword(s):  
Phase Boundary ◽  
Partial Dislocation ◽  
Stacking Faults ◽  
Planar Defects ◽  
Forest Dislocation ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Blocking Property ◽  
Trapezoidal Plate ◽  
Anti Phase Boundary

Eelectrically active defects in 3C–SiC are investigated by considering the structures and interactions of planar defects. An anti-phase boundary (APB) largely degrades the blocking property of semiconductor devices due to its semimetallic nature. Although APBs can be eliminated by orienting the specific polar face of 3C-SiC along a particular direction, stacking faults (SFs) cannot be eliminated due to Shockley-type partial dislocation glide. SFs with Shockley-type partial dislocations form a trapezoidal plate which expands the Si-terminated surface with increasing 3C-SiC thickness. Although the density of SFs can be reduced by counter termination, specific cross-junctions between a pair of counter SFs forms a forest dislocation, and this is regarded as an electrically active defect. This paper proposes an effective way to suppress the forest dislocations and APBs which nucleate during 3C-SiC growth.

Separation of the Driving Force and Radiation-Enhanced Dislocation Glide in 4H-SiC

2012 ◽  
Vol 725 ◽  
pp. 35-40 ◽  
Author(s):  
Koji Maeda ◽  
Rii Hirano ◽  
Yuki Sato ◽  
Michio Tajima
Keyword(s):  
Driving Force ◽  
Partial Dislocation ◽  
Stacking Faults ◽  
Dislocation Velocity ◽  
Electronic Excitations ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Simultaneous Measurements ◽  
Pl Mapping ◽  
Anomalous Expansion

Anomalous expansion of stacking faults (SFs) induced in 4H-SiC under electronic excitations is driven by an electronic force and is achieved by enhanced glide of partial dislocations. An experimental attempt to separate the two physically different effects has been made by conducting photoluminescence (PL) mapping experiments which allowed simultaneous measurements of partial dislocation velocity and SF-originated PL intensity the latter of which is proposed to be related to the driving force for SF expansion through the density of free excitons planarly confined in the SF.

Stacking fault energy in austenitic steels determined by usingin situX-ray diffraction during bending

2014 ◽  
Vol 47 (3) ◽  
pp. 936-947 ◽  
Author(s):  
D. Rafaja ◽  
C. Krbetschek ◽  
C. Ullrich ◽  
S. Martin
Keyword(s):  
Critical Stress ◽  
Partial Dislocation ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Austenitic Steels ◽  
X Ray Diffraction ◽  
X Ray ◽  
Partial Dislocations

A method is presented which determines the stacking fault energy in face-centred cubic materials from the critical stress that is inducedviasample bending in the early stages of plastic deformation. The critical stress is gauged byin situX-ray diffraction. This method utilizes the results of Byun's consideration of the stress dependence of the partial dislocation separation [Byun (2003).Acta Mater.51, 3063–3071]. Byun showed that the separation distance of the partial dislocations increases rapidly when the critical stress is reached and that the critical stress needed for the rapid separation of the partial dislocations is directly proportional to the stacking fault energy. In the approach presented here, the partial dislocation separation and the corresponding triggering stress are monitored by usingin situX-ray diffraction during sample bending. Furthermore, thein situX-ray diffraction measurement checks the possible interactions between stacking faults present on equivalent lattice planes and the interactions of the stacking faults with other microstructure defects. The capability of the proposed method was tested on highly alloyed austenitic steels containing chromium (∼16 wt%), manganese (∼7 wt%) and nickel as the main alloying elements. For the steels containing 5.9 and 3.7 wt% Ni, stacking fault energies of 17.5 ± 1.4 and 8.1 ± 0.9 mJ m−2were obtained, respectively.

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