Properties and Defects of Type II Superconductors

MRS Bulletin ◽  
1991 ◽  
Vol 16 (12) ◽  
pp. 37-41 ◽  
Author(s):  
Donglu Shi
Keyword(s):  
Crystal Structure ◽  
Transition Temperature ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Type Ii ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
High Degree ◽  
Superconducting Parameters

Three major superconducting parameters can characterize a type II superconductor: critical transition temperature, Tc, upper critical magnetic field, Hc2, and critical current density, Jc. Because of the variety of crystal structures, chemical stoichiometrics, and microstructures of the materials, these superconducting parameters differ greatly from system to system.It has been found that the critical transition temperature is closely related to the crystal structure and stoichiometry. Previous studies have shown that compounds with a high degree of symmetry tend to be more favorable to superconductivity. Compounds with a cubic structure, such as a bcc structure, usually have higher Tc values than compounds with a hexagonal lattice. Among conventional superconductors, the so-called A-15 structure is most favorable for high transition temperatures. It is well known that many high Tc superconductors such as YBa2Cu3Ox and Bi2Sr2CaCu2Ox have an orthorhombic structure with a high degree of symmetry.The upper critical field, Hc2, is more complicated in terms of its relationship to structural characteristics. Experimental results have indicated that Hc2 is more closely related to the chemical stoichiometry and crystal structure than to the microstructure.However, the critical current density, Jc, can vary tremendously in a compound with a given crystal structure. The change in critical current density is associated with the so-called flux pinning that arises from the interaction between the flux lines and crystal defects. Thus, Jc is determined mostly by the microstructure of the materials.

Critical current density and microstructure variations in YBa2Cu3O7−x + BaSnO3 films with different concentrations of BaSnO3

2008 ◽  
Vol 23 (12) ◽  
pp. 3363-3369 ◽  
Author(s):  
C.V. Varanasi ◽  
J. Burke ◽  
L. Brunke ◽  
H. Wang ◽  
J.H. Lee ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Gradual Increase ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
High Fields ◽  
Magnitude Increase

Previous work on YBa2Cu3O7−x (YBCO) + BaSnO3 (BSO) films with a single composition showed significant critical current density (Jc) improvements at higher fields but lowered Jc in low fields. A detailed study on BSO concentrations provided here demonstrates that significant Jc enhancement can occur even up to 20 mol% BSO inclusion, where typical particulate inclusions in these concentrations degrade the YBCO performance. YBCO + BSO films were processed on (100) LaAlO3 substrates using premixed targets of YBa2Cu3O7-x (YBCO) with additions of 2, 4, 10, and 20 mol% BSO. The critical transition temperature Tc of the films remained high (>87 K), even with large amounts (20 mol%) of BSO. YBCO + BSO films showed a gradual increase in Jc at high fields as the amount of BSO was increased. More than an order of magnitude increase in Jc was measured in YBCO + BSO samples as compared to regular YBCO at 4 T. YBCO + 10 mol% BSO films showed overall improvement at all the field ranges while YBCO + 20 mol% BSO was better only at high fields. Transmission electron microscopy revealed the presence of ∼7–8-nm-diameter BSO nanocolumns, the density of which increased with increasing BSO content correlating well with the observed improvements in Jc.

Characterization of superconducting SmBa2Cu3O7 films grown by pulsed laser deposition

2002 ◽  
Vol 17 (10) ◽  
pp. 2599-2603 ◽  
Author(s):  
Q. X. Jia ◽  
S. R. Foltyn ◽  
J. Y. Coulter ◽  
J. F. Smith ◽  
M. P. Maley
Keyword(s):  
Transition Temperature ◽  
Critical Current Density ◽  
Pulsed Laser Deposition ◽  
Critical Current ◽  
Current Density ◽  
Deposition Temperature ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Superconducting Transition ◽  
Transition Width

We have investigated epitaxial superconducting SmBa2Cu3O7 (Sm123) films grown by pulsed-laser deposition on single-crystal SrTiO3 substrates. The deposition temperature plays an important role in determining the superconducting properties of Sm123 films. The superconducting transition temperature increases with the deposition temperature whereas the transition width decreases at deposition temperatures in the range of 700–875 °C. A Sm123 film deposited at 850 °C exhibits a transition temperature above 93 K with a transition width less than 0.5 K. Even though Sm123 films exhibit a higher transition temperature than Yba2Cu3O7 (Y123), the Sm123 shows lower critical current density at liquid-nitrogen temperature. The nominal critical current density of Sm123 film is less than 1 MA/cm2 at 75.4 K. Nevertheless, the Sm123 films have less anisotropy and stronger pinning characteristics compared to Y123. They are also much smoother with fewer particulates, as revealed by scanning electron microscopy.

Phase Formation and Transport Critical Current Density of Tl2Ba2CaCu2O8 Superconductor with Nano Bi2O3

2017 ◽  
Vol 268 ◽  
pp. 320-324
Author(s):  
I.M.O. Dabaa ◽  
Roslan Abd-Shukor
Keyword(s):  
Transition Temperature ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Liquid Nitrogen Temperature ◽  
Solid State Reaction Method ◽  
Mixed Phase ◽  
Transport Critical Current Density ◽  
High Porosity ◽  
Grain Size And Orientation

The effect of nanosized Bi2O3 (150 nm) on the formation of the Tl2Ba2CaCu2O8 (Tl-2212) phase, transition temperature and transport critical current density has been studied. Samples with nominal starting composition Tl2Ba2CaCu2O8(Bi2O3)x (x = 0 to 0.5 wt. %) were prepared using the solid state reaction method. Most samples except x = 0.5 showed a mixed phase consisting of the Tl2Ba2CaCu2O8 and Tl2Ba2Ca2Cu3O10 (Tl-2223). The x = 0.5 sample showed a single Tl-2212 phase. However, the transition temperature, Tc of the x = 0.5 was very much suppressed (Tonset = 106 K, Tc zero 88 K). All samples showed random grain size and orientation, with partial melting and high porosity. The x = 0.1 mixed phase sample showed the highest transport critical current density of 285 mA/cm2 at liquid nitrogen temperature (78 K).

Supraleiter mit Schichten der A 15-Phasen Nb-Al und Nb-Al-Ge / Superconductor with Layer of the A 15-Phase Nb-Al(Ge)

1974 ◽  
Vol 29 (1) ◽  
pp. 99-106
Author(s):  
A. Müller
Keyword(s):  
Heat Treatment ◽  
Transition Temperature ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Outer Layer ◽  
Subsequent Heat Treatment ◽  
Products Of Reaction ◽  
A15 Phase

A conductor has been prepared, consisting of Niobium and an outer layer of the A15-phase Nb-Al and Nb-Al-Ge respectively. The process involves two steps: Coating of Niobium by hotdipping and subsequent heat treatment. The procedure, the products of reaction and data on the transition temperature Tc and the critical current density J c of the A15-phase are reported. The maximum values obtained for Tc and J c are 18.5 K (19.3 K) and 5 · 104 A/cm2 (2 · 104 A/cm2) at 5 T and 4.2 K for Nb3Al (Nb3Al, Ge).

CRITICAL CURRENT AND TRANSITION TEMPERATURE WIDTH IN OXIDE SUPERCONDUCTORS UNDER PRESSURE

1990 ◽  
Vol 04 (10) ◽  
pp. 645-650 ◽  
Author(s):  
V. M. SVISTUNOV ◽  
V. YU. TARENKOV ◽  
YU. F. REVENKO ◽  
O. I. CHERNJAK ◽  
A. I. D'YACHENKO ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Oxide Superconductors ◽  
Twin Boundaries

The critical current density of Y-based and Bi-based high-T c superconductors has been measured under pressure. The substantial increase of j c with pressure is found. The results of our measurements can be explained if the sample is regarded as a network of S-N-S junctions with arbitrary parameters. These junctions can be formed by integrain layers and/or twin boundaries.

The Influence of Sintering Time in High and Low Density Bi-2223 Superconductor

2015 ◽  
Vol 1107 ◽  
pp. 616-621
Author(s):  
M. Robaiah ◽  
H. Azhan ◽  
K. Azman ◽  
I.N. Syuhaida ◽  
C.M.N. Azura ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Volume Fraction ◽  
Solid State Reaction Method ◽  
Zero Magnetic Field ◽  
Low Density ◽  
X Ray Diffraction ◽  
Sintering Time

The effects of sintering time in high and low density Bi-2223 phase formation have been investigated. The samples were prepared by the solid-state reaction method at various sintering times ranging from 24, 48, 72 and 96 hours. Sucrose was added during palletization and after heated at 400°C for two hours the sucrose was removed and hence low density sample was created. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and critical current density. The transition temperature varies between 102 K and 96 K with increasing of sintering times. The optimal sintering time of the samples Bi-2223 system was found at 850°C for 72 hours. The critical current density,JCof high density and low density Bi-2223 was measured to be 7.547 A/cm2and 8.333 A/cm2respectively at 77 K under zero magnetic field. The critical current density,JCand superconductivity transition temperature,TCof low density were found to be higher than the pure samples. The critical transition temperature increased with a short gap betweenTConsetandTC zero. The most intense peak in the XRD pattern of sample at sintering time 72 hours belong to the high-TCphase which also indicates an increase in the volume fraction of the high-TCphase with optimum sintering time.

Change of Superconducting Parameters of Y-Ba-Cu-O Slabs and Rings due to High-Energy Ion Beams

2006 ◽  
Vol 47 ◽  
pp. 63-68
Author(s):  
I. Kirschner ◽  
A. Balogh ◽  
Cs. Mészáros ◽  
R. Laiho ◽  
Gy. Kovács ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Magnetic Measurements ◽  
High Energy ◽  
External Irradiation ◽  
High Tc ◽  
Fitting Method ◽  
Properties Of Materials ◽  
Superconducting Parameters

Different high-Tc superconducting Y-Ba-Cu-O samples of slabs and rings have been investigated. Using differently prepared Y1Ba2Cu3O7-d materials, significant deviations between irradiated and unirradiated specimens have been detected in their properties. These investigations demonstrate that unlikely prepared superconductors are differently sensitive to the external irradiation, although they have the same composition. The irradiation applied during these experiments consisted of high-energy Bi-ions with the flux of 5x1010 ions/cm2 and with the energy of 720 MeV. As is experienced, a considerable variation of the magnetic moment in the extent of 19-44% and a significant increase of the critical current density up to 41% can be detected. These originate from the change of the properties of materials due to the irradiation. For the evaluation of the experiments a new fitting method is elaborated for the temperature dependence of the critical current density, providing fully correct results for the whole temperature interval. The A.C. magnetic measurements show, that the irradiation causes to reach the state of the perfect diamagnetism at higher temperatures, than in the case of unirradiated samples. Similarly, the irradiated specimens have much lower losses, than the unirradiated ones and even these smaller values disappear at low temperatures.

Critical Current Density Enhancement and Moisture Destruction Studies of the Compound Superconductor Y-Ba-Cu-Ag-O

1987 ◽  
Vol 99 ◽  
Author(s):  
Y. D. Yao ◽  
A. Krol ◽  
Y. H. Krol ◽  
C. Walters ◽  
S. Spagna ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Moisture Treatment ◽  
Density Enhancement ◽  
Order Of Magnitude ◽  
High Transition ◽  
Moisture Conditions ◽  
State Resistance

ABSTRACTWe have fabricated a series of samples of YBa2(Cu1−x Agx)3Oy compounds where 0 ≤ × ≤ 1, with the intention to study the changes in critical current density and the effect of moisture treatment on normal state resistance R in these high transition-temperature superconductors. The samples exhibited a decrease of the transition-temperature Tc vs the Ag concentration x. Tc is about 93 K for YBa2Cu3Oy and 20 KCfor YBa2Ag3Oy, but it is almost unaffected by the presence or Ag for × < 0.2. An enhancement of the critical current density Jc by nearly an order of magnitude for the samples with 0 < × ≤ 0.1 has been observed. Both Jc and R are found to be sensitive to the ambient moisture conditions.

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