Structural investigation of YBCO films and bicrystal grain boundary junctions

1994 ◽  
Vol 16 (12) ◽  
pp. 2025-2030 ◽  
Author(s):  
A. Del Vecchio ◽  
C. Camerlingo ◽  
F. De Riccardis ◽  
H. Huang ◽  
B. Ruggiero ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Structural Investigation ◽  
Ybco Films

In-Plane Misoriented Grain Boundary Structures and Superconducting Properties of YBCO Films on MgO Substrate

1993 ◽  
pp. 907-910 ◽  
Author(s):  
Hajime Suzuki ◽  
Tomonori Yamamoto ◽  
Masahiro Ohshima ◽  
Masayuki Itoh ◽  
Yoshihiko Hirotsu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Superconducting Properties ◽  
Ybco Films ◽  
Mgo Substrate

Microstructure of Grain Boundary Junctions in Bicrystal High-Tc Superconductor SQUIDs and its Relation with the Device Noise

1997 ◽  
Vol 3 (S2) ◽  
pp. 667-668
Author(s):  
Y. Huang ◽  
L. Lee ◽  
M. Teepe ◽  
K. L. Merkle ◽  
K. Char
Keyword(s):  
Grain Boundary ◽  
Quantum Interference ◽  
Underlying Mechanism ◽  
Low Noise ◽  
Noise Performance ◽  
Ion Milling ◽  
High Tc ◽  
Ybco Films ◽  
Extreme Sensitivity ◽  
Non Destructive

Superconductor Quantum Interference Devices (SQUIDs), because of their extreme sensitivity to magnetic fields and radiation, have found important applications in biomagnetism, non-destructive evaluation and geophysics. One problem in the application of high-Tc SQUIDs is their noise performance. Recently, considerable progress has been made in reducing the noise. To understand the underlying mechanism, it is important to identify the microstructural origin of the junction noise.In this work actual SQUIDs of good and poor noise performance are studied and compared by TEM. The devices were made by epitaxially growing YBa2Cu3O7-x (YBCO) films using laser ablation on 24° SrTiO3 bi-crystal substrates. The TEM samples were prepared by polishing and ion milling. The TEM observation was performed on a JEOL EM-4000EXII and a Hitachi H-9000 microscope.Observation shows that the YBCO films and the grain boundary junctions (GB J) in the low-noise devices are in good quality. The microstructure of the films and the boundaries in the films are shown in fig. 1 and 2.

Evidence for Extensive Grain Boundary Meander and Overgrowth of Substrate Grain Boundaries in High Critical Current Density ex Situ YBa2Cu3O7−x Coated Conductors

2005 ◽  
Vol 20 (8) ◽  
pp. 2012-2020 ◽  
Author(s):  
D.M. Feldmann ◽  
D.C. Larbalestier ◽  
T. Holesinger ◽  
R. Feenstra ◽  
A.A. Gapud ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Film Thickness ◽  
Critical Current ◽  
Current Density ◽  
Thick Films ◽  
Coated Conductors ◽  
Ex Situ ◽  
High Critical Current Density ◽  
Ybco Films

It has been generally accepted that YBa2Cu3O7−x (YBCO) films deposited on deformation textured polycrystalline metal tapes result in YBCO grain boundary (GB) networks that essentially replicate the GBs of the underlying substrate. Here we report that for thicker YBCO films produced by a BaF2 ex situ process, this is not true. Using electron backscatter diffraction combined with ion milling, we have been able to map the evolution of the YBCO grain structure and compare it to the underlying template in several coated conductors. For thin (≤0.5 μm) YBCO films deposited on rolling-assisted biaxially textured substrates (RABiTS), the YBCO GBs nearly directly overlap the substrate GBs. For 0.7–1.4 μm YBCO films, the GBs were found to meander along the substrate GBs and along the sample normal, with displacements several times the film thickness. In very thick films (2.5–2.9 μm), the YBCO grains can completely overgrow substrate grains and GBs, resulting in a substantial disconnection of the YBCO and substrate GB networks. Similar behavior is found for BaF2 ex situ YBCO films on ion-beam-assisted deposition-type templates. The ability of the YBCO to overgrow substrate grains and GBs is believed to be due to liquid-phase mediated laminar grain growth. Although the behavior of the YBCO GB networks changes with YBCO film thickness, the samples maintained high critical current density (Jc) values of >2 MA/cm2 for films up to 1.4 μm thick, and up to0.9 MA/cm2 for 2.5–2.9-μm-thick films.

Design and Optimization of HTC DC Squids for Magnetometric Applications

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1277-1282
Author(s):  
G. Testa ◽  
A. Monaco ◽  
C. Camerlingo ◽  
M. Russo ◽  
E. Sarnelli
Keyword(s):  
Magnetic Field ◽  
Grain Boundary ◽  
Superconducting Properties ◽  
Ybco Films ◽  
Design And Optimization ◽  
Noise Characteristics ◽  
Field Sensitivity ◽  
Deposition Processes ◽  
The Magnetic Field

In order to optimize the magnetic field sensitivity [Formula: see text] we have followed two different approaches. In the former we have analyzed the influence of the quality of YBCO films on the superconducting properties and noise characteristics of bicrystal grain boundary junctions and dc-SQUIDs. For this purpose we have studied and compared three different YBCO deposition processes. In the latter we have reported the different criteria for the design of SQUID magnetometers usable for applicalions in shielded and unshielded environment.

Control of meandering grain boundary configurations in YBa2Cu3Oy bicrystal thin films based on deposition rate

1996 ◽  
Vol 11 (10) ◽  
pp. 2440-2449 ◽  
Author(s):  
X. F. Zhang ◽  
D. J. Miller ◽  
J. Talvacchio
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Grain Boundary ◽  
Deposition Rate ◽  
Three Dimensional ◽  
Film Deposition ◽  
Island Growth ◽  
Ybco Films ◽  
Transmission Electron ◽  
Film Deposition Rate

Changing the film deposition rate is shown to be one way to influence the meandering configurations of grain boundaries (GB's) formed in YBa2Cu3Oy (YBCO) bicrystal thin films. The magnitude and wavelength of the meander in YBCO films deposited at two different rates have been characterized by transmission electron microscopy (TEM) and statistically quantified. It has been found that the meander becomes more uniform and considerably less rough in films deposited at lower rates compared to that observed in films deposited at higher rates. A mechanism for the formation of the meandering GB is proposed based on heterogeneous nucleation and three-dimensional (3D) island growth together with overgrowth of the YBCO films across the substrate grain boundary. The different island sizes and tendency for overgrowth induced by changing the film deposition rate are believed to play important roles in controlling the meandering GB configuration. The possible effects of meandering configurations on transport properties are discussed.

HTSC grain boundary weak links employing high-quality ICM sputtered YBCO films

1994 ◽  
Vol 16 (12) ◽  
pp. 1967-1972 ◽  
Author(s):  
C. Camerlingo ◽  
H. Huang ◽  
B. Ruggiero ◽  
M. Russo ◽  
E. Sarnelli ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Weak Links ◽  
High Quality ◽  
Ybco Films

Texture formation and grain boundary networks in rolling assisted biaxially textured substrates and in epitaxial YBCO films on such substrates

Micron ◽  
1999 ◽  
Vol 30 (5) ◽  
pp. 463-478 ◽  
Author(s):  
A. Goyal ◽  
S.X. Ren ◽  
E.D. Specht ◽  
D.M. Kroeger ◽  
R. Feenstra ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Texture Formation ◽  
Ybco Films

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

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