Measuring Interface Potential of Bi2sr2cacu2O8 (001) Twist Boundaries by off-Axis Electron Holography

2001 ◽  
Vol 7 (S2) ◽  
pp. 294-295
Author(s):  
M. A. Schofield ◽  
Y. Zhu
Keyword(s):  
Critical Current ◽  
Boundary Behavior ◽  
Twist Angle ◽  
Weak Links ◽  
Electron Holography ◽  
Boundary Properties ◽  
Interface Potential ◽  
The Rich ◽  
Superconducting Current ◽  
Twist Boundaries

The potential variation, charge transfer and lattice distortion across grain boundaries in polycrystalline superconductors play a crucial role in the transport properties of the material. in particular, the grain interfaces often act as weak links to the superconducting current, which limits the critical current densities that may be obtained. in the case of the high Tc superconductor Bi2Sr2CaCu2O8 (Bi-2212), special interest is paid to (001) twist boundaries since, in part, they are dominant in c-axis aligned tapes and wires, but more interestingly because the superconducting critical current is found to be independent of twist angle for this system. Such grain boundary behavior is presently not understood, and is further puzzling since “impurity phases” of Bi-2223 or Bi-2201 (consisting of additional or missing Cu-Ca-0 planes, respectively) are commonly observed at the (001) twist boundaries. with the rich structure found at these types if interfaces, understanding the potential distribution may lead to new insight about the boundary properties.

Weak Links and Critical Current Anisotropy in Melt-Textured HTSC Ceramics Studied by Magneto-Optical Express Control

1996 ◽  
pp. 543-550 ◽  
Author(s):  
A. I. Belyaeva ◽  
V. V. Eremenko ◽  
L. A. Kotok ◽  
S. E. Logvinova ◽  
V. A. Nastenko
Keyword(s):  
Critical Current ◽  
Weak Links

Effect of ZnO Nano-Oxide Addition on the Superconducting Properties of the (Bi.Pb)2223 Phase

2011 ◽  
Vol 324 ◽  
pp. 241-244 ◽  
Author(s):  
R. Mawassi ◽  
R. Awad ◽  
Mohamad Roumie ◽  
M. Kork ◽  
I. Hassan
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Flux Pinning ◽  
High Temperature Superconductors ◽  
Weak Links ◽  
Superconducting Properties ◽  
X Ray ◽  
Weight Percentage ◽  
Nano Oxide

The major limitation of Bi-system superconductor applications is the intergrain weak links and weak flux pinning capability producing low critical current density of the Bibased phases. In order to enhance these characteristics and other superconducting properties, effective flux pinning centers are introduced into high temperature superconductors. In this work, different weight percentages of ZnO nano oxide were introduced at the final stage of the Bi1.8Pb0.4Sr2Ca2Cu3O10-y superconductor preparation process. Phase characterization was completed by X-ray diffraction (XRD). Exact constitution of the samples was determined using particle induced X-ray emission (PIXE). Granular and microstructure were investigated using scanning electron microscopy (SEM). Electrical resistivity as function of the temperature was carried to evaluate the relative performance of samples, and finally, E-J characteristic curves were obtained at 77K. Using 0.4 ZnO weight percentage, the electrical and granular properties were greatly enhanced, indicating more efficient pinning mechanisms. A critical current density of 949 A/cm2 was obtained which represents more than twice the value obtained for the pure sample (Jc= 445 A/cm2).

Analysis of Electromagnetic Properties of Bulk Superconductors

2021 ◽  
Vol 21 (9) ◽  
pp. 4941-4943
Author(s):  
Sang Heon Lee
Keyword(s):  
Critical Current Density ◽  
Single Crystal ◽  
Critical Current ◽  
Current Density ◽  
Magnetic Force ◽  
Electromagnetic Properties ◽  
Weak Links ◽  
Metallic Silver ◽  
Bulk Superconductor ◽  
Slow Cooling

In the present study, a YBa2Cu3O7−y bulk superconductor added with 5~10 wt% Ag was fabricated employing Sm123 as a seed to produce a superconductive single crystal. Metallic silver was added to the single crystal of YBa2Cu3O7−y to remove defects such as cracks and pores. Electromagnetic properties of the bulk superconductor at 77 K were analyzed based on relationships of magnetic levitation, trapped magnetic force, and critical current density. The critical current density of the superconductor at 77 K and 0 T was 3.53 × 104 A/cm2. Discontinuous points in the distribution of magnetic field lines were not observed, implying that these two specimens grew well as a single crystal without specific weak links. For the growth of a superconductive nano crystal employing slow cooling at temperature of formation of 123 phase, superconductive nano crystals were aligned in a-b direction, the direction of peak current flow. The peak value of the trapped magnetic force of the YBa2Cu3O7−y superconductor specimen was 3.23 kG. Using the FC method, peak forces of attraction and repulsion were 21.696 N and 70.168 N, respectively.

Off-axis electron holography of manganite-based heterojunctions: Interface potential and charge distribution

2019 ◽  
Vol 28 (4) ◽  
pp. 046101
Author(s):  
Zhi-Bin Ling ◽  
Gui-Ju Liu ◽  
Cheng-Peng Yang ◽  
Wen-Shuang Liang ◽  
Yi-Qian Wang
Keyword(s):  
Charge Distribution ◽  
Electron Holography ◽  
Interface Potential

Bending Damage Evolution and Its Influence on Critical Current and N-Value of Bi2223/Ag Superconducting Composite Tape

2005 ◽  
Vol 475-479 ◽  
pp. 933-936
Author(s):  
D. Doko ◽  
N. Miyazaki ◽  
Shojiro Ochiai ◽  
Hiroshi Okuda ◽  
Sang Soo Oh ◽  
...  
Keyword(s):  
Critical Current ◽  
Damage Evolution ◽  
Interfacial Debonding ◽  
The Other ◽  
N Value ◽  
Composite Tape ◽  
Bending Behavior ◽  
Superconducting Current

Bending behavior of Bi2223/Ag superconducting composite tapes, and the influence of the bending damages on critical superconducting current Ic and n-value that is a measure for the sharpness of the transition from super- to normal conduction, were studied. Following damages, responsible to the reduction in critical current at high bending strains, were observed. (i) Transverse and (ii) longitudinal crackings of the filaments, (iii) interfacial debonding between filaments and silver, and (iv) buckling in compression side. The damage of the filaments arose first locally, resulting in a reduction of the Ic and n-value in the corresponding local portion. The overall Ic and n-values were determined by such a local portion. With increasing strain, the damage of the other portions arose successively, resulting in loss of superconductivity in all portions.

Transport Measurements on Superconducting YBa2Cu3O7-δ Thin Film Lines

1989 ◽  
Vol 169 ◽  
Author(s):  
B. H. Moeckly ◽  
D. K. Lathrop ◽  
G. F. Redinbo ◽  
S. E. Russek ◽  
R. A. Buhrman
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Critical Current ◽  
Weak Link ◽  
High Sensitivity ◽  
Weak Links ◽  
Microwave Response ◽  
Field Response ◽  
Current Densities ◽  
Iv Curves

AbstractCritical current densities, magnetic field response, and microwave response have been measured for laser ablated YBa2Cu3O7-δ thin film lines on MgO and SrTiO3 substrates. Films on SrTiO3 have critical current densities > 1 x 106 A/cm2 at 77K and show uniform transport properties in lines of all sizes. Films on MgO have critical current densities which range between 102 and 106 A/cm2 at 77K and show considerable variation from device to device on the same chip. Narrow lines on MgO with low critical current densities show Josephson weak link structure which includes RSJ-like IV curves, microwave induced constant voltage steps, and a high sensitivity to magnetic field. The presence of the Josephson weak links is correlated with small amounts of misaligned grains in films on MgO.

INFLUENCE OF GRAIN BOUNDARIES ON THE TRANSPORT CRITICAL CURRENT DENSITY OF HIGH Tc SUPERCONDUCTORS

1991 ◽  
Vol 05 (14n15) ◽  
pp. 993-999 ◽  
Author(s):  
HUIMIN SHAO ◽  
MU LU ◽  
TIANCHANG LU ◽  
XICHUN JIN ◽  
LINJIANG SHEN ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Grain Boundaries ◽  
Critical Current ◽  
Current Density ◽  
Transport Critical Current Density ◽  
High Tc Superconductors ◽  
High Tc ◽  
Preparation Conditions ◽  
Percolation Path ◽  
Superconducting Current

This paper describes our efforts to improve the preparation conditions of YBCO samples and increase their density by doping with Sn, F, or Ag and our analysis of the influence of different grain boundaries on superconducting current. We come to the conclusion that, as the grain boundaries have an insulation layer between them forming Josephson junctions and the metalled grain boundaries form proximity junctions which are kind of weak couplings for superconductors, the current-carrying capacity of samples having such grain boundaries cannot be expected to greatly increase. Only by increasing the density of samples and purifying the grain boundaries can a better percolation path for supercurrent be created, thereby considerably increasing the critical current density.

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>

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