Observations and implications of grain boundary dislocation networks in high-angle YBa2Cu3O7−δ grain boundaries

1990 ◽  
Vol 5 (5) ◽  
pp. 919-928 ◽  
Author(s):  
S. E. Babcock ◽  
D. C. Larbalestier
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Weak Link ◽  
Coincidence Site Lattice ◽  
Boundary Structure ◽  
High Angle ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Regular Networks

Regular networks of localized grain boundary dislocations (GBDs) have been imaged by means of transmission electron microscopy in three different types of high-angle grain boundaries in YBa2Cu3O7-δ, implying that these boundaries possess ordered structures upon which a significant periodic strain field is superimposed. The occurrence of these GBD networks is shown to be consistent with the GBD/Structural Unit and Coincidence Site Lattice (CSL)/Near CSL descriptions for grain boundary structure. Thus, these dislocations appear to be intrinsic features of the boundary structure. The spacing of the observed GBDs ranged from ∼10 nm to ∼100 nm. These GBDs make the grain boundaries heterogeneous on a scale that approaches the coherence length and may contribute to their weak-link character by producing the “superconducting micro-bridge” microstructure which has been suggested on the basis of detailed electromagnetic measurements on similar samples.

TEM Study of Secondary Grain Boundary Dislocations in Near-∑13, Near-∑17 and Near-∑29 [001] Twist Boundaries in Gold

1985 ◽  
Vol 43 ◽  
pp. 244-245
Author(s):  
S.E. Babcock
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
Boundary Structure ◽  
Ordered Structure ◽  
Boundary Dislocation ◽  
High Angle ◽  
Extensive Search ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Twist Boundaries

In 1970, an extensive search by transmission electron microscopy (TEM) for evidence of ordered structure in high-angle [001] twist boundaries helped to establish the credibility of the DSC/CSL description of grain boundary structure. In this work, square grids of line contrast were found in boundaries for which the twist misorientation (Θ) was very near the special Σ5+ Σ13 and Σ17 Θ. The lines ran parallel to the primitive translation vectors (b(1) and b(2)) of the appropriate low-Σ DSC lattice, and their spacing correlated well with the spacing predicted by Frank's formula for dislocations with Burgers vectors b(1) and b(2). The images were interpreted as secondary grain boundary dislocation (SGBD) networks. Only for the near-Σ5 case was g•b analysis carried out to show that the line contrast was characteristic of b= 1/10 <310> type screw SGBD's.

Intrinsic Structure in Grain Boundaries and Boundary Mobility

1978 ◽  
Vol 36 (3) ◽  
pp. 380-391
Author(s):  
L.M. Clarebrough ◽  
C.T. Forwood
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Low Energy ◽  
Boundary Structure ◽  
Boundary Mobility ◽  
High Angle ◽  
Intrinsic Structure ◽  
Cornell University ◽  
Grain Boundary Structure ◽  
Energy Configurations

An outstanding experimental contribution to the knowledge of grain boundary structure in the 1970's is the work of Balluffi and his colleagues at Cornell University on artificially fabricated boundary interfaces in thin films of gold (e.g., Balluffi, Komem and Schober, 1972; Balluffi, Goodhew, Tan and Wagner, 1975). In particular, for high-angle boundaries they have shown that secondary grain boundary dislocations (g.b.d's.) do exist and accommodate a deviation from a low-energy misorientation corresponding to an exact C.S.L. relationship. Further, following the results of Spyridelis, Delavignette and Amelinckx (1967) they have shown that a network of g.b.d's. can act as a diffraction grating, causing extra reflections whose spacing is reciprocally related to the separation of the g.b.d's. (Balluffi, Sass and Schober, 1972). The description of high-angle grain boundaries in terms of secondary g.b.d's. accommodating a departure from an exact C.S.L. orientation is based solely on geometrical considerations, but it has been pointed out that other low-energy configurations may be preferred when account is taken of the nature of interatomic forces (Gleiter and Pumphrey, 1976; Hermann, Gleiter and Baro, 1976; Smith, Vitek and Pond, 1977).

The hierarchy of grain boundary structures in SiC bicrystals

1988 ◽  
Vol 46 ◽  
pp. 596-597
Author(s):  
Y. Ishida ◽  
H. Ichinose ◽  
Y. Inomata
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Lattice Theory ◽  
Coincidence Site Lattice ◽  
Boundary Structure ◽  
Geometrical Theory ◽  
Site Lattice ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Predictive Role

The standard geometrical theory having been developed to describe periodically ordered grain boundaries in metals, ie coincidence-site lattice theory faces a new frontier to be expanded in terms of hierarchy of atomic structures in low energy grain boundaries of polytype SiC bicrystals. The unit translation lattice of the polytype crystal is large and elongated in the direction perpendicular to the basal plane. With the elongated translation lattice, the coincidence-site lattice is generally very large. Often too large to be physically significant, although the predictive role of the coincidence-site lattice theory in specifying the orientation of periodically ordered interface was still preserved. Such periodically ordered boundaries were indeed found to occur in the present SiC bicrystals as is predicted by the geometrical theory. A dual description of the grain boundary structure in terms of hierarchy of atomic structures is shown useful in characterizing the bicrystal boundaries.High purity SiC bicrystals were produced by sublimation-deposition method by cooling the encapseled SiC slowly from 2800K.

First-Principles Studies on Grain Boundary Energies of [110] Tilt Grain Boundaries in Aluminum

2007 ◽  
Vol 561-565 ◽  
pp. 1837-1840 ◽  
Author(s):  
Y. Inoue ◽  
Tokuteru Uesugi ◽  
Yorinobu Takigawa ◽  
Kenji Higashi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
First Principles ◽  
Boundary Structure ◽  
First Principles Calculations ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Tilt Grain Boundary

The grain boundary structure and its energy are necessary for the fundamental understanding of the physical properties of materials. In aluminum, three distinct atomic structures of a Σ9(221)[110] tilt grain boundary have been reported in previous studies using atomistic simulations and a high-resolution transmission electron microscopy (HRTEM). In this work, we studied the atomic structure and energy of the Σ9 tilt grain boundary in aluminum using first-principles calculations. A comparison of the grain boundary energies among the three distinct Σ9 tilt grain boundaries determined through first-principles calculations allowed us to identify the most stable atomic structure of Σ9 tilt grain boundary in aluminum.

Periodic grain boundary structures in aluminium. II. A geometrical method for analysing periodic grain boundary structure and some related transmission electron microscope observations

1977 ◽  
Vol 357 (1691) ◽  
pp. 471-483 ◽  
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Transmission Electron Microscope ◽  
Boundary Structure ◽  
Geometrical Method ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Line Defects

A crystallographic treatment is developed which clarifies the relation between the structure of a grain boundary and its location between relatively translated crystals. Characterization of line defects which can exist in grain boundaries is also facilitated by using this treatment, and the following topics are considered: (1) the computed structures in part I of this work; (2) steps at the cores of perfect grain boundary dislocations; (3) boundary structures related by c.s.l. symmetry; (4) partial grain boundary dislocations. Transmission electron microscope observations of topic 4 are presented.

Grain boundary structure observed by T.E.M

1978 ◽  
Vol 36 (1) ◽  
pp. 410-411
Author(s):  
P.J. Goodhew
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Lower Energy ◽  
Planar Defect ◽  
Boundary Structure ◽  
High Angle ◽  
Thin Specimen ◽  
Special Boundaries ◽  
Grain Boundary Structure

This paper reports some observations on gold by TEM which imply that the dissociation of a high angle grain boundary into two lower energy boundaries may occur extensively.It is well established that grain boundaries of any desired geometry can be created in gold by the welding together of thin single crystals. The resultant thin bicrystal specimens are ideally suited for immediate examination by TEM and many aspects of grain boundary structure and behaviour in such specimens have been studied or discussed. One particularly useful specimen configuration can be achieved if the bicrystal is annealed until its boundary migrates (lowering its total area) until it is perpendicular to the surface of the thin specimen. This specimen geometry has been used to study, inter alia, the faceting of grain boundaries.During a study of the behaviour of coincidence high angle boundaries (i.e. those special boundaries whose geometry is such that a fraction 1/Σ of the lattice sites in both crystals coincide) it was noticed that the boundary under observation was no longer a single planar defect.

Quantitative Analysis of Interface Structure by HRTEM

2001 ◽  
Vol 7 (S2) ◽  
pp. 240-241
Author(s):  
Frank Ernst
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Point Defects ◽  
Experimental Studies ◽  
Boundary Structure ◽  
Atomistic Modeling ◽  
Active Point ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Atomistic Structure

The development of ‘quantitative’ high-resolution transmission electron microscopy (QHRTEM) has led to considerable progress in analyzing and understanding the atomistic structure of grain boundaries and heterointerfaces, which often control relevant macroscopic properties of materials. The following results of recent experimental studies and the comparison of these results with atomistic modeling demonstrate the strength of QHRTEM:1.Grain Boundaries in SrTiO3. Some technical applications of SrTiO3 ceramics rely on special electric properties of this material, which originate from segregation of electrically active point defects to grain boundaries. QHRTEM can substantially contribute to understanding the correlation between the atomistic structure of grain boundaries and the segregation of point defects to these interfaces. As an example for a grain boundary structure solved by QHRTEM, FIGs. la and b present an experimental HRTEM image of the Σ= 3, (111) grain boundary in SrTiO3 and the corresponding atomistic structure as obtained by QHRTEM.

Grain Boundary Structure in ARB Processed Copper

2006 ◽  
Vol 503-504 ◽  
pp. 925-930 ◽  
Author(s):  
Kenichi Ikeda ◽  
Naoki Takata ◽  
Kousuke Yamada ◽  
Fuyuki Yoshida ◽  
Hideharu Nakashima ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Structural Unit ◽  
Md Simulation ◽  
Boundary Structure ◽  
Dislocation Model ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Symmetric Tilt ◽  
The Difference

Grain boundary structures in the Accumulative roll-bonding (ARB) processed copper (ARB-Cu) have been studied. The grain boundary structures were observed by high-resolution transmission electron microscopy (HRTEM). In order to clarify the difference between the grain boundaries in ARB-Cu and equilibrium boundaries, calculated atomic structure of symmetric tilt grain boundaries with <110> common axis (<110> symmetric tilt grain boundary; <110> STGB) in Cu were used. The near 14° boundary in the ARB-Cu could be described by the dislocation model, but the dense dislocation region existed near the grain boundary. The high angle boundaries in ARB-Cu could be described by the structural units which were obtained by molecular dynamics (MD) simulation. Furthermore, in the 2 cycles and 6 cycles ARB-Cu (2cARB-Cu and 6cARB-Cu), the deformation twin boundaries could be observed and described by the structural unit. Therefore, it was concluded that the grain boundary structure in the ARB-Cu was not much different from the normal equilibrium grain boundary and explained by conventional dislocation and structural unit models.

Structural analysis of a Σ5 grain boundary in YBa2Cu3O7δ

1993 ◽  
Vol 51 ◽  
pp. 942-943
Author(s):  
J.-Y. Wang ◽  
Y. Zhu ◽  
A.H. King ◽  
M. Suenaga
Keyword(s):  
Grain Boundary ◽  
Lattice Mismatch ◽  
Weak Link ◽  
Coincidence Site Lattice ◽  
Large Angle ◽  
Dislocation Core ◽  
Superconducting Order Parameter ◽  
Outstanding Problem ◽  
Transmission Electron

One outstanding problem in YBa2Cu3O7−δ superconductors is the weak link behavior of grain boundaries, especially boundaries with a large-angle misorientation. Increasing evidence shows that lattice mismatch at the boundaries contributes to variations in oxygen and cation concentrations at the boundaries, while the strain field surrounding a dislocation core at the boundary suppresses the superconducting order parameter. Thus, understanding the structure of the grain boundary and the grain boundary dislocations (which describe the topology of the boundary) is essential in elucidating the superconducting characteristics of boundaries. Here, we discuss our study of the structure of a Σ5 grain boundary by transmission electron microscopy. The characterization of the structure of the boundary was based on the coincidence site lattice (CSL) model.Fig.l shows two-beam images of the grain boundary near the projection. An array of grain boundary dislocations, with spacings of about 30nm, is clearly visible in Fig. 1(a), but invisible in Fig. 1(b).

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