scholarly journals Electron Microscopy Imaging of Flux Pinning Defects in YBCO Superconductors

2021 ◽  
Author(s):  
◽  
Anne-Hélène Puichaud
Keyword(s):  
Electron Microscopy ◽  
Magnetic Flux ◽  
Critical Current ◽  
Flux Pinning ◽  
Coated Conductors ◽  
Electron Holography ◽  
Coated Conductor ◽  
Lorentz Microscopy ◽  
Superconducting Wires ◽  
Ybco Superconductors

<p>High-temperature superconductors are of great interest because they can transport electrical current without loss. For real-world applications, the amount of current, known as the critical current Ic, that can be carried by superconducting wires is the key figure of merit. Large Ic values are necessary to off-set the higher cost of these wires. The factors that improve Ic (microstructure/performance relationship) in the state-of-the-art coated conductor wires based on YBa₂Cu₃O₇ (YBCO) are not fully understood. However, microstructural defects that immobilise (or pin) tubes of magnetic flux (known as vortices) inside the coated conductors are known to play a role in improving Ic. In this thesis, the vortex-defect interaction in YBCO superconductors was investigated with high-end transmission electron microscopy (TEM) techniques using two approaches.  First, the effect of dysprosium (Dy) addition and oxygenation temperature on the microstructure and critical current were investigated in detail. Changing only the oxygenation temperature leads to many microstructural changes in pure YBCO coated conductors. It was found that Dy addition reduces the sensitivity of the YBCO to the oxygenation temperature, in particular it lowers the microstructural disorder while maintaining the formation of nanoparticles, which both contribute to the enhancement of Ic.  In the second approach, two TEM based techniques (off-axis electron holography and Lorentz microscopy) were used to study the magnetic flux vortices. Vortex imaging was attempted with a TEM operated at 300 kV on both a YBCO crystal as well as a YBCO coated conductor. Many challenges were encountered including sample preparation, inhomogeneity, and geometry, in addition to the need to perform measurements at cryogenic temperatures. Although vortices were not able to be observed in the coated conductors, tentative observation of vortices in a YBCO crystal was made using Lorentz microscopy. Improvements for future electron holography experiments on YBCO at low voltage are suggested. This work represents a pioneering step towards directly imaging vortices in YBCO using more widely available microscopes with the aim of better understanding flux pinning to ultimately boost Ic in superconducting wires.</p>

scholarly journals Electron Microscopy Imaging of Flux Pinning Defects in YBCO Superconductors

2021 ◽  
Author(s):  
◽  
Anne-Hélène Puichaud
Keyword(s):  
Electron Microscopy ◽  
Magnetic Flux ◽  
Critical Current ◽  
Flux Pinning ◽  
Coated Conductors ◽  
Electron Holography ◽  
Coated Conductor ◽  
Lorentz Microscopy ◽  
Superconducting Wires ◽  
Ybco Superconductors

<p>High-temperature superconductors are of great interest because they can transport electrical current without loss. For real-world applications, the amount of current, known as the critical current Ic, that can be carried by superconducting wires is the key figure of merit. Large Ic values are necessary to off-set the higher cost of these wires. The factors that improve Ic (microstructure/performance relationship) in the state-of-the-art coated conductor wires based on YBa₂Cu₃O₇ (YBCO) are not fully understood. However, microstructural defects that immobilise (or pin) tubes of magnetic flux (known as vortices) inside the coated conductors are known to play a role in improving Ic. In this thesis, the vortex-defect interaction in YBCO superconductors was investigated with high-end transmission electron microscopy (TEM) techniques using two approaches.  First, the effect of dysprosium (Dy) addition and oxygenation temperature on the microstructure and critical current were investigated in detail. Changing only the oxygenation temperature leads to many microstructural changes in pure YBCO coated conductors. It was found that Dy addition reduces the sensitivity of the YBCO to the oxygenation temperature, in particular it lowers the microstructural disorder while maintaining the formation of nanoparticles, which both contribute to the enhancement of Ic.  In the second approach, two TEM based techniques (off-axis electron holography and Lorentz microscopy) were used to study the magnetic flux vortices. Vortex imaging was attempted with a TEM operated at 300 kV on both a YBCO crystal as well as a YBCO coated conductor. Many challenges were encountered including sample preparation, inhomogeneity, and geometry, in addition to the need to perform measurements at cryogenic temperatures. Although vortices were not able to be observed in the coated conductors, tentative observation of vortices in a YBCO crystal was made using Lorentz microscopy. Improvements for future electron holography experiments on YBCO at low voltage are suggested. This work represents a pioneering step towards directly imaging vortices in YBCO using more widely available microscopes with the aim of better understanding flux pinning to ultimately boost Ic in superconducting wires.</p>

scholarly journals Opportunities for Chromatic Aberration Corrected High-Resolution Transmission Electron Microscopy, Lorentz Microscopy and Electron Holography of Magnetic Minerals

2012 ◽  
Vol 18 (S2) ◽  
pp. 1708-1709 ◽  
Author(s):  
R. Dunin-Borkowski ◽  
L. Houben ◽  
J. Barthel ◽  
A. Thust ◽  
M. Luysberg ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Chromatic Aberration ◽  
Electron Holography ◽  
Magnetic Minerals ◽  
Lorentz Microscopy ◽  
Transmission Electron ◽  
Aberration Corrected

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Characterization of a Co-CoO Obliquely Evaporated Magnetic Tape by Analytical Electron Microscopy and Electron Holography

2004 ◽  
Vol 10 (1) ◽  
pp. 116-121 ◽  
Author(s):  
Daisuke Shindo ◽  
Masasuke Hosokawa ◽  
Zheng Liu ◽  
Yasukazu Murakami ◽  
Takuya Ito ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Magnetic Flux ◽  
Analytical Electron Microscopy ◽  
Magnetic Domain ◽  
High Resolution Electron Microscopy ◽  
Columnar Structure ◽  
Mapping Method ◽  
Thickness Variation ◽  
Electron Holography ◽  
Analytical Electron

The microstructure and magnetic domain structure of a Co-CoO obliquely evaporated tape for magnetic recording are studied by analytical electron microscopy and electron holography, respectively. While the existence of Co and CoO crystallites is confirmed by energy-filtered electron diffraction, columnar structure of the Co crystallites surrounded by the densely packed CoO crystallites is visualized by an elemental mapping method with electron energy loss spectroscopy, and the crystal orientation relation among the Co crystallites is clarified by high-resolution electron microscopy. It is found that the neighboring Co crystallites have close crystal orientations. On the other hand, electron holography reveals the magnetic flux distribution in a thin section of the tape. Although there exists the background resulting from the effect of inner potential with thickness variation, the distribution of lines of magnetic flux is found to correspond well to the recorded pattern.

Flux-line observation by electron Holography

1993 ◽  
Vol 51 ◽  
pp. 1024-1025
Author(s):  
Akira Tonomura
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Magnetic Flux ◽  
Transition Region ◽  
Flux Line ◽  
Electron Holography ◽  
Phase Measurements ◽  
Flux Lines ◽  
Magnetic Flux Lines ◽  
Line Observation

In electron microscopy, the intensity of an electron beam transmitted through an object can be observed. While in electron holography, the phase of the electron beam can also be observed and displayed as an interference micrograph. Using a technique unique to holography, the precision of phase measurements can be increased to 1/100 of the electron wavelength. An interference micrograph of a magnetic object can be interpreted in a straightforward way: Contour fringes directly indicate projected magnetic flux lines and a constant magnetic flux of h/e (= 4 × 10-15 Wb) flows between two adjacent fringes (See Fig. 1).Examples of magnetic recordings are shown in Fig. 2. Flux lines inside and outside of the magnetic tapes, recorded in different ways, can directly and quantitatively be observed as interference micrographs. Figure 2 (a) shows an example of in-plane magnetic recording. Two magnetization streams, pointed in opposite directions, merge and produce vortices in the transition region similar to those produced by streams of water.

scholarly journals Engineered Microstructures and Transport Properties in YBCO Coated Conductors

2001 ◽  
Vol 689 ◽  
Author(s):  
T. G. Holesinger ◽  
B. J. Gibbons ◽  
J. Y. Coulter ◽  
S. R. Foltyn ◽  
J. R. Groves ◽  
...  
Keyword(s):  
Transport Properties ◽  
Buffer Layer ◽  
Critical Current ◽  
Film Structure ◽  
Coated Conductors ◽  
Superconducting Film ◽  
Coated Conductor ◽  
Layer Material ◽  
Current Densities ◽  
Ybco Coated Conductors

ABSTRACTEach process used to deposit or make the bi-axially textured template, buffer layer(s), and the superconductor in a coated conductor creates interfaces along which defects or interfacial reactions may result. These defects can be additive and propagate through the entire film structure to affect the growth and properties of the superconducting film. Defects within the films and their corresponding transport properties have been correlated with the differences in the thickness of the underlying buffer layer material. This knowledge can be used to control and engineer the structure of the coated conductor to maximize critical current densities.

Phase evolution in Ba–(Nd,Eu,Gd)–Cu–O-coated conductor films

2008 ◽  
Vol 23 (8) ◽  
pp. 2067-2071 ◽  
Author(s):  
W. Wong-Ng ◽  
I. Levin ◽  
J. Ritter ◽  
L.P. Cook ◽  
G. Liu ◽  
...  
Keyword(s):  
Phase Structure ◽  
Flux Pinning ◽  
Solution Method ◽  
Phase Evolution ◽  
Coated Conductors ◽  
Coated Conductor ◽  
X Ray Diffraction ◽  
Structure Form ◽  
X Ray ◽  
Phase Relationships

Phases that are in equilibrium with BaR2CuO6+x (R=lanthanides and Y), such as the “green-phase” and “brown-phase” structural variants of BaR2CuO5 in bulk samples, are attractive choices for flux-pinning for coated conductor applications because of the guaranteed chemical stability. In films, high-temperature x-ray diffraction studies of Ba2RCu3O6+x superconductor deposited on SrTiO3 substrate using the trifluoroacetate solution method demonstrate that while BaNd2CuO5 (“brown-phase” structure) develops at 735 °C and 100 Pa pO2, neither BaGd2CuO5 nor Ba(Nd1/3Eu1/3Gd1/3)2CuO5 (both green-phase structure) form at these conditions. As a result, Ba2(Nd1/3Eu1/3Gd1/3)Cu3O6+x in thin films is in equilibrium with the brown-phase, and Ba2GdCu3O6+x is in equilibrium with Gd2O3 in the Ba–Gd–Cu–O system, in contrast to the bulk systems. Different phase relationships in the vicinity of the Ba2RCu3O6+x phase imply different phases are available for flux-pinning applications. These differences will need to be considered carefully in designing optimized superconducting coated conductors.

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