Current transfer lengths and the origin of linear components in the voltage - current curves of Ag-sheathed BSCCO components

Polák, M.; Zhang, W; Parrell, J.A.; Cai, X. Y.; Polyanskii, Anatolii; Hellstrom, E. E.; Larbalestier, D. C.; Majoroš, M.

doi:10.1088/0953-2048/10/10/007

Cited by 52 publications

(43 citation statements)

References 16 publications

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“…Such ohmic regions are characteristic of the V(I) curves measured along the c axis of 2212 single crystals 23 and they are occasionally observed in transport at 4.2 K along damaged 2223 tapes. 24,25 By contrast, our curves are very similar in shape to the extended E(J) curves measured by Yamasaki et al 26 with J in the plane of 2223 films. The similarity of our tape data to film data suggests that the dissipation density, E-J, is associated with transport along a-b planes in tapes, just as it is in films.…”

Section: Figsupporting

confidence: 86%

Role of c-axis field components in making the transport E(J) characteristics of (Bi,Pb)2Sr2Ca2Cu3Ox tapes insensitive to the direction of field within the tape plane

Edelman

Larbalestier

1998

Journal of Applied Physics

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We report extended ͑over four decades͒ electric field versus current density characteristics of ͑Bi,Pb͒ 2 Sr 2 Ca 2 Cu 3 O 10 tapes in magnetic fields applied along each of the three principal tape axes at 77 K, and along the two principal axes in the tape plane at 4.2 K. The characteristics are almost independent of field direction in the tape plane at both temperatures. Similar insensitivity of the critical current to magnetic field direction observed in other polycrystalline high temperature superconductors has been ascribed to the percolative nature of current flow, while the insensitivity in ͑Bi,Pb͒ 2 Sr 2 Ca 2 Cu 3 O 10 ͑2223͒ films and Bi 2 Sr 2 CaCu 2 O 8 single crystals has been attributed to c-axis conduction across Josephson junctions. We show that the insensitivity of the critical current density to the field direction of these tapes follows naturally from the fact that the dissipation depends only on the field component lying along the c axis of individual 2223 grains. Lorenz-force driven motion of the pancake vortices that form within each 2223 grain provides a dissipation mechanism that involves only the c-axis components of the field. The angular dispersion of the grains in the tape ensures a c-axis field component in most grains, regardless of the applied field direction. This produces the remarkable insensitivity of E(J) over some four orders of magnitude of the electric field.

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Section: Figsupporting

confidence: 86%

Role of c-axis field components in making the transport E(J) characteristics of (Bi,Pb)2Sr2Ca2Cu3Ox tapes insensitive to the direction of field within the tape plane

Edelman

Larbalestier

1998

Journal of Applied Physics

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“…We found that E -J characteristics such as these are produced by ohmic resistance, which results from current transfer around damaged regions into the silver sheath. 21 However, when this sample was measured by the resistance method, 0 H* was quite clearly defined as 155 mT, as shown in the inset to Fig. 4.…”

mentioning

confidence: 93%

Determination of irreversibility field variations in mono- and multifilamentary (Bi,Pb)2Sr2Ca2Cu3Ox tapes by transport current methods

Anderson

Parrell

Polák

et al. 1997

Applied Physics Letters

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The irreversibility field, H*, has been measured for a variety of mono-and multifilamentary ͑Bi,Pb͒ 2 Sr 2 Ca 2 Cu 3 O x ͑2223͒ tapes using two different transport current techniques. It is common to characterize the quality of 2223 tapes by their zero-field, 77 K critical current density ͓J c (0 T, 77 K͔͒, even though this ignores the fact that significant self-fields depress J c (0 T, 77 K) and the possibility that the in-field J c (B) characteristics may be optimized independently of the J c (0 T, 77 K) value. To provide more useful information, we propose a second characterization, that of the irreversibility field, H*. Having both H* and J c (0 T, 77 K) information helps in separating the two independent contributions that better connectivity and stronger flux pinning can make to the J c of a tape. We illustrate this point with results from a variety of mono-and multifilamentary Bi-2223/Ag tapes in damaged and undamaged conditions, which show that H* ͑77 K͒ can vary from ϳ100 to ϳ200 mT and not directly correlate with J c (0 T, 77 K). The two proposed protocols for H* measurement are robust and compatible with common transport measurement procedures. © 1997 American Institute of Physics. ͓S0003-6951͑97͒00352-5͔Both the zero-field, J c (0), and the in-field, J c (B), critical current densities of ͑Bi,Pb͒ 2 Sr 2 Ca 2 Cu 3 O x ͑2223͒ tapes must be improved to make applications economically feasible. J c is defined experimentally as J c ϭI c /A where I c is the critical current and A is the area of the whole ceramic cross section. However, this averaged, overall J c is most certainly an understatement of the maximum local J c because the current percolates through only a fraction of the cross-sectional area, A active . J c (0) contains significant contributions from current paths that include weakly linked grain boundaries, which are decoupled by small magnetic fields, and it is thus at least partially limited by self-fields generated by the transport current. However, J c (B) is strongly influenced by the strength of the flux pinning. At high fields, either intragranular 1-6 or intergranular 7,8 flux pinning becomes the main J c -limiting mechanism. Because different mechanisms determine J c (0) and J c (B), this leads us to believe that J c (B) may be optimized independently of J c (0). The irreversibility field, H*, is an increasingly common parameter used to measure flux pinning because it is strongly influenced by flux pinning. H* can be measured by several magnetization and transport current techniques. Previous work [8][9][10] has shown that individual composites often show a direct correlation between H* and J c (0). However, as we have accumulated a larger database of H* and J c (0) characterizations, we have found that there is no universal correlation and we, therefore, conclude that it is vital to characterize both the flux pinning and zero-field properties, if the highest performance is to be developed in BSCCO-2223 tapes.When H* is measured by magnetization, the magnetization signal is averaged ov...

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“…Values of the same order of magnitude were also given in [13]. Details of the calculation of boundary resistances from measured zvalues will be published separately.…”

Section: Anisotropy Of Pefmentioning

confidence: 99%

Time constant measurements and effective permeability of a stack of high-T/sub c/ tapes

Eckelmann

Krempaský²,

Schmidt³

2001

IEEE Trans. Appl. Supercond.

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Filament cross-sections of High-Tc tapes have generally a large aspect ratio. The magnetic moment of the filaments which determines the magnetic properties of a stack of tapes therefore depends strongly on the magnetic field orientation. The stack can be treated as a material with an effective permeability Pes. For large field amplitudes Pef approaches unity, while for low amplitudes it can be considerably smaller than unity, namely in the case of perpendicular external field. We derived expressions for y,f for parallel and perpendicular field amplitudes well below the filament penetration field. Under this assumption the filaments are supposed to be perfectly diamagnetic. The theoretical predictions for pef are compared with the values extracted from direct time constant measurements.The experiments were performed with samples stacks of twisted and untwisted Bi-2223 tapes. The effective transverse matrix resistivity was found to be highly anisotropic which is understood as the presence of a boundary layer resistance between filaments and silver matrix.

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Current transfer lengths and the origin of linear components in the voltage - current curves of Ag-sheathed BSCCO components

Cited by 52 publications

References 16 publications

Role of c-axis field components in making the transport E(J) characteristics of (Bi,Pb)2Sr2Ca2Cu3Ox tapes insensitive to the direction of field within the tape plane

Role of c-axis field components in making the transport E(J) characteristics of (Bi,Pb)2Sr2Ca2Cu3Ox tapes insensitive to the direction of field within the tape plane

Determination of irreversibility field variations in mono- and multifilamentary (Bi,Pb)2Sr2Ca2Cu3Ox tapes by transport current methods

Time constant measurements and effective permeability of a stack of high-T/sub c/ tapes

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