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).

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.

Effect of thermal annealing on grain boundary chemistry of polycrystalline TiBa2Ca2Cu3Oy films

1994 ◽  
Vol 52 ◽  
pp. 968-969
Author(s):  
Z. L. Wang ◽  
C. L. Briant ◽  
J. DeLuca ◽  
A. Goyal ◽  
D. M. Kroeger ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Weak Link ◽  
Zero Field ◽  
Stabilized Zirconia ◽  
Local Texture ◽  
Transmission Electron ◽  
Axis Alignment ◽  
Boundary Chemistry ◽  
Small Misorientation ◽  
Misorientation Angles

Recent studies have shown that spray-pyrolyzed films of the Tl-1223 compound (TlxBa2Ca2Cu3Oy, with 0.7 < × < 0.95) on polycrystalline yttrium stabilized zirconia substrates can be prepared which have critical current density Jc near 105 A/cm2 at 77 K, in zero field. The films are polycrystalline, have excellent c-axis alignment, and show little evidence of weak-link behavior. Transmission electron microscopy (TEM) studies have shown that most grain boundaries have small misorientation angles. It has been found that the films have a nigh degree of local texture indicative of colonies of similarly oriented grains. It is believed that inter-colony conduction is enhanced by a percolative network of small angle boundaries at colony interfaces. It has also been found that Jc is increased by a factor of 4 - 5 after the films were annealed at 600 °C in oxygen. This study is thus carried out to determine the effect on grain boundary chemistry of the heat treatment.

The Study of Defects in Metals Using High Resolution Transmission Electron Microscopy and Atomistic Calculations

1990 ◽  
Vol 183 ◽  
Author(s):  
M. J. Mills ◽  
M. S. Daw
Keyword(s):  
Grain Boundary ◽  
Good Description ◽  
Dislocation Core ◽  
Thin Foil ◽  
Core Structure ◽  
Embedded Atom ◽  
Pair Potentials ◽  
Transmission Electron ◽  
Atomistic Calculations ◽  
Stringent Test

AbstractThe coupling of HRTEM with atomistic calculations is described for the study of grain boundaries and dislocations in aluminum. HRTEM images of the Σ9 (221) [110] grain boundary are compared with molecular statics calculations using both the Embedded Atom Method (EAM) and two pair potentials. Comparison between observed and simulated images are shown to serve as a stringent test of the theoretical methods. Atomistic calculations can in turn provide threedimensional information about the defect structure. Using the EAM, it is also possible to account for the effects of thin foil geometries on the minimim energy configuration of defects. While these effects are found to be minimal for grain boundary structures, the influence of the thin-foil geometries on the core structure of the 60° dislocation in aluminum is discussed. These comparisons indicate that the EAM function provides a good description of grain boundary structures, but fails to reproduce the observed dislocation core structure due to a low predicted value of the intrinsic stacking fault energy (SFE) on the (111). In contrast, the pair potentials used in this study provide reasonable SFE values, but appear to be less accurate for the prediction of the Σ9 (221) [110] grain boundary structures.

scholarly journals Structural characterization of Yba2Cu3O7–δ/Y2O3 composite films

1998 ◽  
Vol 13 (4) ◽  
pp. 954-958 ◽  
Author(s):  
P. R. Broussard ◽  
M. A. Wall ◽  
J. Talvacchio
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Coincidence Site Lattice ◽  
Composite Films ◽  
X Ray Diffraction ◽  
Plane Orientation ◽  
Transmission Electron ◽  
Two Phases ◽  
High Degree

Using 4-circle x-ray diffraction and transmission electron microscopy, we have studied the microstructure and in-plane orientation of the phases present in thin film composite mixtures of Yba2Cu3O7–δ and Y2O3. We see a high degree of in-plane orientation and have verified a previous prediction for the in-plane order of Y2BaCuO5 on (110) MgO. Transmission electron microscopy shows the composite films to be a mixture of two phases, with YBCO grain sizes of ≈1 μm. We have also compared our observations of the in-plane order to the predictions of a modified near coincidence site lattice model.

scholarly journals Growth and Characterization of High-Quality GaN Nanowires on PZnO and PGaN by Thermal Evaporation

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
L. Shekari ◽  
H. Abu Hassan ◽  
S. M. Thahab ◽  
Z. Hassan
Keyword(s):  
Gallium Nitride ◽  
Thermal Evaporation ◽  
Lattice Mismatch ◽  
Growth Direction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gan Nanowires ◽  
Transmission Electron

In the current research, an easy and inexpensive method is used to synthesize highly crystalline gallium nitride (GaN) nanowires (NWs) on two different substrates [i.e., porous zinc oxide (PZnO) and porous gallium nitride (PGaN)] on Si (111) wafer by thermal evaporation without any catalyst. Microstructural studies by scanning electron microscopy and transmission electron microscope measurements reveal the role of the substrates in the nucleation and alignment of the GaN NWs. Further structural and optical characterizations were performed using high-resolution X-ray diffraction, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. Results indicate that the NWs have a single-crystal hexagonal GaN structure and growth direction in the (0001) plane. The quality and density of GaN NWs grown on different substrates are highly dependent on the lattice mismatch between the NWs and their substrates. Results indicate that NWs grown on PGaN have better quality and higher density compared to NWs on PZnO.

scholarly journals Grain Boundary Characterization of Nanocrystalline Cu from the Stereological Analysis of Transmission Electron Microscope Orientation Maps

2011 ◽  
Vol 17 (S2) ◽  
pp. 1416-1417 ◽  
Author(s):  
A Darbal ◽  
K Ganesh ◽  
K Barmak ◽  
G Rohrer ◽  
P Ferreira ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Transmission Electron Microscope ◽  
Stereological Analysis ◽  
Transmission Electron ◽  
Orientation Maps

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

TEM Characterization of 2º Tilt Grain Boundary in Alumina

2007 ◽  
Vol 561-565 ◽  
pp. 2427-2430 ◽  
Author(s):  
E. Tochigi ◽  
Naoya Shibata ◽  
Atsutomo Nakamura ◽  
Takahisa Yamamoto ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Separation Distance ◽  
Stacking Fault ◽  
Tem Characterization ◽  
Transmission Electron ◽  
Tilt Grain Boundary ◽  
The Relationship

Dislocation structure of {1120}/<1100> 2º tilt grain boundary in alumina was observed by transmission electron microscopy (TEM). The grain boundary consisted of periodical array of basal dislocations, which were dissociated into pairs of 1/3<1010> and 1/3<0110> partials with {1120} stacking-fault in between. The relationship between the separation distance of partials and the stacking-fault was modeled by considering the force balances of periodical dislocations. The estimated stacking-fault energy for 2o tilt grain boundary was consistent with the previous reports.

Grain boundary in textured YBa2Cu3O7−δ superconductor

1991 ◽  
Vol 6 (12) ◽  
pp. 2507-2518 ◽  
Author(s):  
Yimei Zhu ◽  
H. Zhang ◽  
H. Wang ◽  
M. Suenaga
Keyword(s):  
Grain Boundaries ◽  
Coincidence Site Lattice ◽  
Large Angle ◽  
Low Energy ◽  
Site Lattice ◽  
Microscopy Technique ◽  
Rotation Axes ◽  
Transmission Electron ◽  
Complex Crystal Structure ◽  
Complex Crystal

The misorientations of over 200 pairs of adjacent grains separated by grain boundaries in textured YBa2Cu3O7−δ were measured using a transmission electron microscopy technique. The results indicate that there exist discrete preferred rotation angles and rotation axes. The existence of low-energy boundaries is inferred. The results are analyzed based on the Constrained Coincidence Site Lattice (CCSL) and O2-lattice theories and imply the applicability of such theories for the case of large-angle grain boundaries in a complex crystal structure such as YBa2Cu3O7−δ. The results of analysis also show that some boundaries are likely to be reduced in oxygen near the boundary to satisfy the constraint of the coincidence site lattice.

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