YBa2Cu3O7−x Grain Boundary Weak Links on MgO Bicrystal

1992 ◽  
Vol 275 ◽  
Author(s):  
H. B. Lu ◽  
S. L. Tu ◽  
J. J. Wang ◽  
J. Lin ◽  
T. W. Huang ◽  
...  
Keyword(s):  
Thin Films ◽  
Laser Ablation ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Weak Link ◽  
Weak Links ◽  
Artificial Boundaries ◽  
Tilt Boundaries ◽  
Preliminary Study ◽  
High Degree

ABSTRACTThe characteristics of YBa2Cu3O7−x (YBCO) thin films by laser ablation on MgO bicrystals have been investigated. The bicrystals were fabricated by hot pressing two single crystals with the configuration of [001] tilt boundaries. The YBCO films were epitaxial grown with C-axis normal to the both adjacent grains of bicrystals. The FWHM about (005) reflection was 0.4–0.5 degree, indicating the high degree of the oriention for the film with small mosaic spread. Our preliminary study showed that the typical value of Jc on either side of the bicrystal boundary was 0.4–10×106 A/cm2 at 15K, while that across the 10° tilt boundaries was 0.3–9×105 A/cm2 at 15K. These results implied that the artificial grain boundaries effectively weakened the supercurrent, and therefore, the weak-link properties of artificial boundaries were more easily controllable than those of naturally occuring grain boundaries.

A TEM study of microstructures of YBa2Cu3O7−x thin films deposited on LaAlO3 by laser ablation

1991 ◽  
Vol 6 (9) ◽  
pp. 1823-1828 ◽  
Author(s):  
S.N. Basu ◽  
A.H. Carim ◽  
T.E. Mitchell
Keyword(s):  
Thin Films ◽  
Laser Ablation ◽  
Film Thickness ◽  
Single Crystal ◽  
Grain Boundaries ◽  
Misfit Dislocations ◽  
High Angle ◽  
Interfacial Structures ◽  
High Degree ◽  
Periodic Spacing

The microstructures of YBa2Cu3O7−x thin films deposited by laser ablation on single crystal (001) LaAlO3 substrates have been investigated. The orientation of the YBa2Cu3O7−x layer next to the interface is found to be completely c-perpendicular, with a high degree of epitaxy between the film and the substrate. Misfit dislocations, with a periodic spacing of around 13 nm, are present at the interface. Two distinct interfacial structures are seen in these films. At a film thickness of around 400 nm, nucleation of c-parallel grains occurs, leading to a switchover from a c, and, and-perpendicular to a c-parallel microstructure. Amorphous particulates, ejected from the target during processing, lead to the formation of misoriented grains, giving rise to high-angle grain boundaries in the film.

Grain Boundaries in Yba2 Cu3O7-δ Thin Films

1989 ◽  
Vol 169 ◽  
Author(s):  
M. Grant Norton ◽  
Lisa A. Tietz ◽  
C. Barry Carter ◽  
Stephen E Russek ◽  
Brian H. Moeckly ◽  
...  
Keyword(s):  
Thin Films ◽  
Laser Ablation ◽  
Grain Boundaries ◽  
Weak Link ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Superconducting Films ◽  
High Angle ◽  
Twin Boundaries

AbstractGrain boundaries in YBa2Cu3O7-δ thin films deposited on (001)-MgO by pulsed laser ablation have been characterized using selected area diffraction. In addition to twin boundaries, the presence of both low-angle and high-angle grain boundaries were characteristic of the film's microstructure. The presence of certain grain boundaries may be responsible for the weak-link Josephson behavior observed in small constrictions formed in superconducting films on MgO.

Structure of high-angle-tilt boundaries in YBa2Cu3-O7-x thin films

1991 ◽  
Vol 49 ◽  
pp. 1086-1087
Author(s):  
D. H. Shin ◽  
J. Silcox ◽  
S. E. Russek ◽  
D. K. Lathrop ◽  
B. H. Moeckly ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Boundaries ◽  
Weak Link ◽  
Boundary Region ◽  
Atomic Scale ◽  
High Resolution Imaging ◽  
High Angle ◽  
Superconducting Properties ◽  
Tilt Boundaries ◽  
Resolution Imaging

It has been known that high angle tilt grain boundaries in c-axis oriented YBa2Cu3O7-x thin films cause weak link behavior in the transport properties reducing Jc's by several orders of magnitude. These grain boundaries have been shown to be clean both structurally and chemically by high resolution imaging and microanalysis studies. Therefore the mechanism of weak link behavior in thin film YBa2Cu3O7-x is not yet understood.Recently it has been deduced from the behavior of weak link Jc under small magnetic fields that the high angle tilt boundaries are nonuniform, consisting of several regions of good contact, each about 5-10 % of the boundary length, with the rest of the boundary region being poor. This seems to suggest that the superconducting properties at the boundary may be sensitive to changes in structures of atomic scale, since typical grain boundaries are free of macroscopic (≥ 10 Å) defects all along the boundaries.

Evidence for Weak Link Effects in Epitaxial Thin Films of YBCO on LaAlO3

1992 ◽  
Vol 275 ◽  
Author(s):  
J. Bohandy ◽  
B. F. Kim ◽  
K. Moorjani ◽  
F. J. Adrian
Keyword(s):  
Thin Films ◽  
Grain Boundaries ◽  
Weak Link ◽  
Weak Links ◽  
Superconducting Thin Films ◽  
Epitaxial Thin Films ◽  
High Quality ◽  
Microwave Loss

ABSTRACTEvidence of weak link effects in epitaxial thin films of YBa2Cu3O7-yon LaAlO3 is obtained from magnetically modulated resistance (MMR) measurements. This result suggests that weak links could provide a mechanism for the residual microwave loss in high quality superconducting thin films which contain predominantly low angle grain boundaries.

scholarly journals Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

2021 ◽  
Author(s):  
A. Bauer ◽  
M. Vollmer ◽  
T. Niendorf
Keyword(s):  
Martensitic Transformation ◽  
Grain Boundary ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Boundaries ◽  
Tensile Tests ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Grain Orientations ◽  
High Degree

AbstractIn situ tensile tests employing digital image correlation were conducted to study the martensitic transformation of oligocrystalline Fe–Mn–Al–Ni shape memory alloys in depth. The influence of different grain orientations, i.e., near-〈001〉 and near-〈101〉, as well as the influence of different grain boundary misorientations are in focus of the present work. The results reveal that the reversibility of the martensite strongly depends on the type of martensitic evolving, i.e., twinned or detwinned. Furthermore, it is shown that grain boundaries lead to stress concentrations and, thus, to formation of unfavored martensite variants. Moreover, some martensite plates seem to penetrate the grain boundaries resulting in a high degree of irreversibility in this area. However, after a stable microstructural configuration is established in direct vicinity of the grain boundary, the transformation begins inside the neighboring grains eventually leading to a sequential transformation of all grains involved.

Interaction Between Lattice Dislocations and Grain Boundaries In Ordered Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
B.J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F.W. Schapink
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Partial Dislocation ◽  
Atomistic Simulations ◽  
Many Body ◽  
Shockley Partial Dislocation ◽  
Screw Dislocations ◽  
Applied Shear Stress ◽  
Tilt Boundaries

ABSTRACTThe interaction of 1/2<1 1 0> screw dislocations with symmetric [1 1 0] tilt boundaries was investigated by atomistic simulations using many-body potentials representing ordered compounds. The calculations were performed with and without an applied shear stress. The observations were: absorption into the grain boundary, attraction of a lattice Shockley partial dislocation towards the grain boundary and transmission through the grain boundary under the influence of a shear stress. It was found that the interaction in ordered compounds shows similarities to the interaction in fcc.

Influence of grain boundary weak links on the nonequilibrium response of YBaCuO thin films to short laser pulses

1994 ◽  
Vol 7 (4) ◽  
pp. 751-755 ◽  
Author(s):  
Gregory N. Gol'tsman ◽  
Ivan G. Goghidze ◽  
Pavel B. Kouminov ◽  
Boris S. Karasik ◽  
Alexei D. Semenov ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Laser Pulses ◽  
Weak Links ◽  
Short Laser Pulses

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.

Texture Formation and Improvement of Grain Boundary Weak‐Links in Tape Shaped Wire Prepared by the Unidirectional Solidification Technique.

1989 ◽  
Vol 169 ◽  
Author(s):  
Michiya Okada ◽  
Toyotaka Yuasa ◽  
Tosimi Matsumoto ◽  
Katuzo Aihara ◽  
Masahiro Seido ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Fine Particles ◽  
Unidirectional Solidification ◽  
Weak Links ◽  
Second Phase ◽  
Texture Formation

AbstractAu‐Sheathed Y‐Ba‐Cu‐O(YBCO) and Tl‐Ba/Sr‐Ca‐Cu‐O(TBSCCO) tapes were fabricated by the drawing‐rolling and subsequent unidirectional solidification. A typical microstructure of melt‐textured polycrystallite including fine particles of second phase(e.q. Y‐211) was observed. The Tl‐2223 tapes prepared at an optimized condition yielded Jc=15,300 A/cm2 at 77K in the absence of magnetic field, and l,100A/cm2 in a magnetic field of IT. The enhancement of Jc in a magnetic field is suggested to be due to the improvement of weak‐links in grain boundaries.

Defects in Superconductor thin Films

1994 ◽  
Vol 357 ◽  
Author(s):  
A. S. Nandedkar ◽  
L. Ganapathi
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Computer Aided ◽  
Superconductor Thin Films

AbstractComputer aided simulations were used to investigate various grain boundary configurations in superconducting (YBa2Cu3O7) thin films. Four angles for tilt grain boundaries were simulated (12.45°, 53.5°, 66.4°, and 74.6°). Energies of unrelaxed configurations were calculated.

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