Critical currents in the anisotropic superconductor2H−NbSe2:Evidence for an upper bound of the surface critical-current density

2002 ◽  
Vol 65 (6) ◽  
Author(s):  
G. Lazard ◽  
P. Mathieu ◽  
B. Plaçais ◽  
J. Mosqueira ◽  
Y. Simon ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Upper Bound ◽  
Critical Currents

Critical Currents in NbSe2: Evidence for Surface Pinning

1972 ◽  
Vol 50 (22) ◽  
pp. 2840-2841 ◽  
Author(s):  
J. Kopp ◽  
D. J. Huntley ◽  
R. F. Frindt
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Critical Currents ◽  
Flux Flow ◽  
Flux Lines

The variation of critical current density for flux flow with thickness has been measured for crystals of NbSe2 between 10−6 and 0.03 cm thick. The dominant behavior is that [Formula: see text] (thickness)−1 and this is interpreted as evidence for surface pinning predominating over bulk pinning of the flux lines.

Y2BaCuO5 addition and its effects on critical currents in large grains of YBa2Cu3O7–δ: A quantitative microstructural study

1996 ◽  
Vol 11 (7) ◽  
pp. 1616-1626 ◽  
Author(s):  
Manoj Chopra ◽  
Siu-Wai Chan ◽  
R. L. Meng ◽  
C. W. Chu
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Flux Pinning ◽  
Crack Opening ◽  
Critical Currents ◽  
Interparticle Spacing ◽  
Pinning Force ◽  
Volume Percent ◽  
Initial Volume

The addition of Y2BaCuO5 (211) particles to large grain melt textured YBa2Cu3O7–δ(Y123) has significantly improved the critical current density (Jc) of this material. Here, a systematic quantitative analysis on the effects of the 211 addition was performed on a microscopic scale with a systematic variation of the initial volume percent of 211. From the correlation between critical current measurements and quantitative microscopy of both (001) and (110) sections, a maximum value of Jc is observed, corresponding to a measured Y123 volume percent of 20% ± 3%. Accounting for the loss of liquid phase for the present processing, the corresponding optimum initial volume of 211 for the highest measured Jc is 40%. Further comparison between the weighted Jc and the true flux pinning force (Fp) also shows a maximum pinning force for an initial 211 addition of 40%. Although the weighted Jc starts to decrease with an initial 211 volume of above 40%, the pinning efficiency at higher magnetic fields (2–4 T) of the superconducting Y123 matrix was actually improved with an ever increasing 211 addition to at least 50%. Though an increasing addition of 211 is effective in producing efficient flux pinning sites in the Y123 matrix, percolation paths in the Y123 matrix become limited for supercurrent. Hence, a measured 211 volume corresponding to 80% 211 is proved to give the best possible critical current density. Furthermore, crack opening and crack spacing of the superficial cracks are found to decrease with an increasing 211 addition and with a decreasing 211 interparticle spacing. The penetration and surface length of each of these superficial cracks are hence reduced, which leads to a better electrical connectivity in the Y123 matrix.

Grain boundaries in high-Tc superconductors

1988 ◽  
Vol 46 ◽  
pp. 1008-1009
Author(s):  
M.F. Chisholm
Keyword(s):  
Critical Current Density ◽  
Grain Boundaries ◽  
Critical Current ◽  
Current Density ◽  
Weak Link ◽  
Critical Currents ◽  
Pinning Force ◽  
Conduction Path ◽  
Direct Measurements

One crucial property for most superconductor applications is the materials critical current density. Measurements on single crystals of YBa2Cu3O7, show critical currents to be in excess of 105 A/cm2 at 77K. However, polycrystalline samples show values of 103 A/cm2 or less at 77K. The critical current, unlike other superconductivity properties, is not a property of a specific composition but of a specific sample. Defects, introduced during the material processing, exert a pinning force which makes it possible for Type-II superconductors to carry current without losses. At the same time these defects represent an interruption in the structural and chemical order which has been shown to be necessary for superconductivity in the YBa2Cu3Ox phase, and so they may also act as a weak link in the conduction path. The most direct measurements of the role of individual grain boundaries on the critical current density are those of Chaudhari et al. who examined patterned YBa2Cu3O7 films grown on SrTiO3 substrates.

Growth of and Critical Current Density of TL2BA2CACU2O8 Superconducting Single Crystals

1992 ◽  
Vol 275 ◽  
Author(s):  
H. M. Duan ◽  
T. S. Kaplan ◽  
B. Dlugosch ◽  
A. M. Hermann
Keyword(s):  
Critical Current Density ◽  
Single Crystals ◽  
Critical Current ◽  
Liquid Nitrogen ◽  
Current Density ◽  
Liquid Nitrogen Temperature ◽  
Critical Currents ◽  
Different Temperatures

ABSTRACTLarge single crystals of Tl2Ba2CaCu2O8 superconductors were grown by a two step self-flux process. Crystals are plate-like. The in-plane crystal sizes are as large as 5mmX5mm and the thickness range from 0.01mm to 0.8mm. The critical currents were extracted from I-V curves measured at different temperatures. jc was about 2.4×104 A/cm2 at liquid nitrogen temperature.

scholarly journals Формирование сверхпроводящих покрытий Fe(Se-=SUB=-1-x-=/SUB=-Te-=SUB=-x-=/SUB=-) на поверхности железа

2020 ◽  
Vol 90 (1) ◽  
pp. 69
Author(s):  
В.А. Русаков ◽  
Б.А.-Т. Мелех ◽  
М.П. Волков
Keyword(s):  
Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Phase Structure ◽  
Pure Iron ◽  
Magnetic Moments ◽  
Critical Currents ◽  
Β Phase ◽  
The Magnetic Field

To obtain superconducting coatings Fe(Se1 − xTex) on the surface of iron substrates (strip, tape) two techniques have been used: deposition of coatings from chalcogen vapor and deposition of coatings from a melt of chalcogenides. The resulting coatings had a β-phase structure of the FeSe compound and critical superconductivity parameters close to those of bulk polycrystals. It was shown that for deposition of coatings is mandatory to use compositions including Se and Te, and the optimal substrate is pure iron. The critical current density of coatings were estimated using the magnetic moments dependences on the magnetic field. At T = 4 K and fields greater than 4 T, the critical currents were of the order of 103 A / cm2 for both types of coatings and change slightly with increasing magnetic field

Microstructural characterization of YBa2Cu3O7-x thin films formed by metalorganic CVD

1991 ◽  
Vol 49 ◽  
pp. 1080-1081
Author(s):  
P. Lu ◽  
W. Huang ◽  
C.S. Chern ◽  
Y.Q. Li ◽  
J. Zhao ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Film Growth ◽  
Chemical Vapor ◽  
Microstructural Characterization ◽  
Ion Milling ◽  
Conventional Grinding

The YBa2Cu3O7-x thin films formed by metalorganic chemical vapor deposition(MOCVD) have been reported to have excellent superconducting properties including a sharp zero resistance transition temperature (Tc) of 89 K and a high critical current density of 2.3x106 A/cm2 or higher. The origin of the high critical current in the thin film compared to bulk materials is attributed to its structural properties such as orientation, grain boundaries and defects on the scale of the coherent length. In this report, we present microstructural aspects of the thin films deposited on the (100) LaAlO3 substrate, which process the highest critical current density.Details of the thin film growth process have been reported elsewhere. The thin films were examined in both planar and cross-section view by electron microscopy. TEM sample preparation was carried out using conventional grinding, dimpling and ion milling techniques. Special care was taken to avoid exposure of the thin films to water during the preparation processes.

Facet Topography and Dislocation Structure as a Possible Source for Electrical Heterogeneity in [001] TILT Bicrystals of YBa2Cu3O7-δ

1996 ◽  
Vol 54 ◽  
pp. 338-339
Author(s):  
I-Fei Tsu ◽  
D.L. Kaiser ◽  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Electromagnetic Properties ◽  
Length Scale ◽  
Density Values ◽  
Current Densities ◽  
Applied Fields ◽  
A Current

A current theme in the study of the critical current density behavior of YBa2Cu3O7-δ (YBCO) grain boundaries is that their electromagnetic properties are heterogeneous on various length scales ranging from 10s of microns to ˜ 1 Å. Recently, combined electromagnetic and TEM studies on four flux-grown bicrystals have demonstrated a direct correlation between the length scale of the boundaries’ saw-tooth facet configurations and the apparent length scale of the electrical heterogeneity. In that work, enhanced critical current densities are observed at applied fields where the facet period is commensurate with the spacing of the Abrikosov flux vortices which must be pinned if higher critical current density values are recorded. To understand the microstructural origin of the flux pinning, the grain boundary topography and grain boundary dislocation (GBD) network structure of [001] tilt YBCO bicrystals were studied by TEM and HRTEM.

Effects of surface damage on critical current density in MgB2 thin films

2021 ◽  
Vol 22 ◽  
pp. 14-19
Author(s):  
Soon-Gil Jung ◽  
Duong Pham ◽  
Jung Min Lee ◽  
Yoonseok Han ◽  
Won Nam Kang ◽  
...  
Keyword(s):  
Thin Films ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Surface Damage ◽  
Mgb2 Thin Films
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