Analytical methods for the calculation of the elastic interaction of point defects with dislocation loops in hexagonal crystals

Irradiation of metals leads to the formation of point-defects (vacancies and selfinterstitials) that usually agglomerate in the form of dislocation loops. Due to the elastic interaction between SIA (self-interstitial atoms) and dislocations, the loops absorb in most cases more SIA than vacancies. That is why the loops observed by transmission electron microscopy are almost always interstitial in nature. Nevertheless, vacancy loops have been observed in zirconium following electron or neutron irradiation (see for example [1]). Some authors proposed that this unexpected behavior could be accounted for by SIA diffusion anisotropy [2]. Following the approach proposed by Woo [2], the cluster dynamics model presented in [3] that describes point defect agglomeration was extended to the case where SIA diffusion is anisotropic. The model was then applied to the loop microstructure evolution of a zirconium thin foil irradiated with electrons in a high-voltage microscope. The main result is that, due to anisotropic SIA diffusion, the crystallographic orientation of the foil has considerable influence on the nature (vacancy or interstitial) of the loops that form during irradiation.

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Elastic interaction of point defects in cubic and hexagonal crystals

Physics of the Solid State ◽

10.1134/s1063783416050140 ◽

2016 ◽

Vol 58 (5) ◽

pp. 971-980 ◽

Cited By ~ 8

Author(s):

S. A. Kukushkin ◽

A. V. Osipov ◽

R. S. Telyatnik

Keyword(s):

Point Defects ◽

Elastic Interaction ◽

Hexagonal Crystals

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Elastic interaction of dislocation loops and point defects

Czechoslovak Journal of Physics ◽

10.1007/bf01689477 ◽

1964 ◽

Vol 14 (6) ◽

pp. 443-453 ◽

Cited By ~ 24

Author(s):

J. Baštecká ◽

F. Kroupa

Keyword(s):

Point Defects ◽

Elastic Interaction ◽

Dislocation Loops

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BIAS OF BASAL DISLOCATION LOOP IN ZIRCONIUM

10.46813/2021-132-029 ◽

2021 ◽

pp. 29-34

Author(s):

A.V. Babich ◽

P.N. Ostapchuk

Keyword(s):

Numerical Calculation ◽

Dislocation Loop ◽

Point Defects ◽

Function Method ◽

Elastic Field ◽

Its Region ◽

Elastic Interaction ◽

Basal Dislocation ◽

Hexagonal Crystals ◽

Toroidal Geometry

An analytical expression for the elastic interaction energy of radiation point defects of the dipole type with the basal dislocation loop of the hcp metal is obtained using the Green's function method for hexagonal crystals in the Krener approach. It was used for numerical calculation of the bias for the basal dislocation loop of zirconium in a toroidal reservoir. The toroidal geometry of the reservoir allows one to perform the calculation for a loop of any size and without any correction of the elastic field in its region of influence. The dependencies of the loop bias on its radius and nature are obtained for various shapes of dipole defects.

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Study of dislocation loops in Arsenic-Rich as-grown GaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126548 ◽

1987 ◽

Vol 45 ◽

pp. 350-351

Author(s):

Byung-Teak Lee

Keyword(s):

Point Defects ◽

Electronic Devices ◽

Arsenic Concentration ◽

Stoichiometric Compound ◽

Dislocation Loops ◽

Gaas Crystal ◽

Ion Milling ◽

Transmission Electron ◽

Arsenic Source ◽

High Arsenic

Grown-in dislocations in GaAs have been a major obstacle in utilizing this material for the potential electronic devices. Although it has been proposed in many reports that supersaturation of point defects can generate dislocation loops in growing crystals and can be a main formation mechanism of grown-in dislocations, there are very few reports on either the observation or the structural analysis of the stoichiometry-generated loops. In this work, dislocation loops in an arsenic-rich GaAs crystal have been studied by transmission electron microscopy.The single crystal with high arsenic concentration was grown using the Horizontal Bridgman method. The arsenic source temperature during the crystal growth was about 630°C whereas 617±1°C is normally believed to be optimum one to grow a stoichiometric compound. Samples with various orientations were prepared either by chemical thinning or ion milling and examined in both a JEOL JEM 200CX and a Siemens Elmiskop 102.

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Contrast From Point Defects in The Infinitesimal Approximation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001495 ◽

1980 ◽

Vol 38 ◽

pp. 350-351

Author(s):

L. J. Sykes ◽

J. J. Hren

Keyword(s):

Electron Microscope ◽

Point Defects ◽

Broad Class ◽

Stacking Fault ◽

Crystalline Solids ◽

Dislocation Loops ◽

Analytical Expression ◽

Stacking Fault Tetrahedra

In electron microscope studies of crystalline solids there is a broad class of very small objects which are imaged primarily by strain contrast. Typical examples include: dislocation loops, precipitates, stacking fault tetrahedra and voids. Such objects are very difficult to identify and measure because of the sensitivity of their image to a host of variables and a similarity in their images. A number of attempts have been made to publish contrast rules to help the microscopist sort out certain subclasses of such defects. For example, Ashby and Brown (1963) described semi-quantitative rules to understand small precipitates. Eyre et al. (1979) published a catalog of images for BCC dislocation loops. Katerbau (1976) described an analytical expression to help understand contrast from small defects. There are other publications as well.

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Hardening in AlN Induced by Point Defects

MRS Proceedings ◽

10.1557/proc-235-445 ◽

1991 ◽

Vol 235 ◽

Cited By ~ 5

Author(s):

H. Suematsu ◽

T. E. Mitchell ◽

T. Iseki ◽

T. Yano

Keyword(s):

Point Defects ◽

Defect Density ◽

Single Point ◽

Length Change ◽

Dislocation Loops ◽

Three Samples ◽

Different Temperatures ◽

Hardness Change ◽

Isolated Point ◽

Small Clusters

ABSTRACTPressureless-sintered AlN was neutron irradiated and the hardness change was examined by Vickers indentation. The hardness was increased by irradiation. When the samples were annealed at high temperature, the hardness gradually decreased. Length was also found to increase and to change in the same way as the hardness. A considerable density of dislocation loops still remained, even after the hardness completely recovered to the value of the unirradiated sample. Thus, it is concluded that the hardening in AlN is caused by isolated point defects and small clusters of point defects, rather than by dislocation loops.Hardness was found to increase in proportion to the length change. If the length change is assumed to be proportional to the point defect density, then the curve could be fitted qualitatively to that predicted by models of solution hardening in metals. Furthermore, the curves for three samples irradiated at different temperatures and fluences are identical. There should be different kinds of defect clusters in samples irradiated at different conditions, e.g, the fraction of single point defects is the highest in the sample irradiated at the lowest temperature. Thus, hardening is insensitive to the kind of defects remaining in the sample and is influenced only by those which contribute to length change.

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