An experimental study of flux pinning and flux dynamics in a system with two types of pinning centre

Adamopoulos, N.; Soylu, B.; Yu, You‐Jun; Evetts, J.E.

doi:10.1016/0921-4534(94)02402-2

Cited by 21 publications

(12 citation statements)

References 24 publications

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“…Previous studies of micrometer-diameter MgO whiskers have shown that this material can be incorporated into BSCCO superconductors with little chemical reaction. 27,28 The principal effect of these micron size whiskers is an improvement in mechanical properties; J c does not appear to be enhanced and in some cases is lowered by their addition. 28 Presumably the reduction of J c is due to a decrease in the cross-sectional superconducting area in the composite, the inhibition of grain growth of the BSCCO phase, and the interference of grain alignment in the presence of the large whiskers.…”

Section: Introductionmentioning

confidence: 99%

Nanostructured high-temperature superconductors: Creation of strong-pinning columnar defects in nanorod/superconductor composites

1997

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A chemical approach to the formation of columnar defects involving the growth and incorporation of MgO nanorods into high temperature superconductors (HTS's) has been developed. MgO nanorods were incorporated into Bi2Sr2CaCu2Oz, Bi2Sr2Ca2Cu3Oz, and Tl2Ba2Ca2Cu3Oz superconductors at areal densities up to 2 × 1010/cm2. Microstructural analyses of the composites demonstrate that the MgO nanorods create a columnar defect structure in the HTS matrices, form a compositionally sharp interface with the matrix, and self-organize into orientations perpendicular and parallel to the copper oxide planes. Measurements of the critical current density demonstrate significant enhancements in the MgO nanorod/HTS composites at elevated temperatures and magnetic fields compared with reference samples.

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Section: Introductionmentioning

confidence: 99%

Nanostructured high-temperature superconductors: Creation of strong-pinning columnar defects in nanorod/superconductor composites

1997

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“…. , O n the other hand, micrometer-diameter MgO whiskers can be incorporated into BSCCO superconductors with little chemical reaction (26,27). These micrometersized whiskers improve mechanical strength, but 1, does not appear to be enhanced and in some cases is lowered by their addition (27).…”

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confidence: 99%

Nanorod-Superconductor Composites: A Pathway to Materials with High Critical Current Densities

Yang

Lieber

1996

Science

564

273

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Most large-scale applications of the high-temperature copper oxide superconductors (HTSCs) require high critical current densities ( J c 's) at temperatures near the boiling point of liquid nitrogen to be technologically useful, although thermally activated flux flow reduces J c dramatically at these temperatures. This intrinsic limitation can be overcome by introducing nanometer-sized columnar defects into an HTSC. Nanorods of magnesium oxide were grown and incorporated into HTSCs to form nanorod-HTSC composites. In this way, a high density of nanorod columnar defects can be created with orientations perpendicular and parallel to the copper oxide planes. The J c 's of the nanorod-HTSC composites are enhanced dramatically at high temperatures and magnetic fields as compared with reference samples; these composites may thus represent a technologically viable strategy for overcoming thermally activated flux flow in large-scale applications.

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“…A second approach has focused on introducing defects associated with dopants, dislocations, and particles. [2][3][4] While this has achieved some success, enhancements to the transport J c of HTS wires in an applied field has not yet occurred. Finally, controlled manipulation of the oxide constitution to produce impurity phase particles in Bi-2212 5 has met with limited success.…”

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confidence: 99%

Enhancement of the 77 K irreversibility field and critical current density of (Bi,Pb)2Sr2Ca 2Cu3Ox tapes by manipulation of the final cooling rate

Parrell

Larbalestier

Riley

et al. 1996

Applied Physics Letters

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By manipulating the cooling rate from the final heat treatment, we have raised the 77 K, self-field critical current density (J c ) of multifilament (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x ͑2223͒ tapes by a factor of 3, and the irreversibility field (H*) by more than 50%. The J c of samples cooled in 7.5% O 2 from their reaction temperature of 825°C increased from ϳ8 to ϳ24 kA/cm 2 and H*͑77 K͒ increased from ϳ120 to ϳ200 mT as the cooling rate was decreased from 5 to 0.016°C/min. The results unambiguously show that the flux pinning properties of 2223 tapes can be improved by simple changes in wire processing. © 1996 American Institute of Physics. ͓S0003-6951͑96͒00145-3͔Improving the J c of 2223 superconductors in an applied magnetic field provides the most direct path to broad application of high-temperature superconductor ͑HTS͒ wire. Agclad 2223 made using the powder-in-tube process is currently the most promising HTS wire technology because established processes can be used to manufacture long lengths of strongly linked material. However, in contrast to Y-and Tl-based superconductors, 2223 has relatively weak flux pinning properties above about 30 K. For this reason, use of 2223 wires in moderate to high applied fields is currently limited to low temperature.Three strategies have been used previously to improve flux pinning in Bi-based superconductors. One successful approach has been postprocessing irradiation. 1 However, although the in-field transport J c can be significantly enhanced, it is not clear to what extent this method can be applied to practical wire manufacturing. A second approach has focused on introducing defects associated with dopants, dislocations, and particles. [2][3][4] While this has achieved some success, enhancements to the transport J c of HTS wires in an applied field has not yet occurred. Finally, controlled manipulation of the oxide constitution to produce impurity phase particles in Bi-2212 5 has met with limited success. In this contribution, we show that simple modifications to the heat treatment can enhance both the zero field and the infield properties of 2223 tapes.Parrell et al. 6 have shown that the rate at which 2223 tapes are cooled after heat treatment can have a large effect on the transport J c , critical temperature (T c ) transition, and filament microstructure. They reported that slow cooling ͑Ͻ0.1°C/min͒ in 7.5% O 2 increased the J c ͑77 K, self-field͒ by as much as 50% over tapes cooled more quickly, and considerably sharpened the T c transition, despite decomposition of the 2223 phase at temperatures below the 2223 phase stability limit. This letter builds on this previous work of Parrell et al. by exploring in detail one contribution to the J c improvement. In particular, we have evaluated the flux pinning contribution by measuring the cooling rate dependence of the irreversibility field, H*.Ag-clad 85-filament samples of nominal composition Bi 1.8 Pb 0.3 Sr 1.9 Ca 2.0 Cu 3.1 O x were processed to develop a dense and aligned 2223 phase structure. The final heat treatment...

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An experimental study of flux pinning and flux dynamics in a system with two types of pinning centre

Cited by 21 publications

References 24 publications

Nanostructured high-temperature superconductors: Creation of strong-pinning columnar defects in nanorod/superconductor composites

Nanostructured high-temperature superconductors: Creation of strong-pinning columnar defects in nanorod/superconductor composites

Nanorod-Superconductor Composites: A Pathway to Materials with High Critical Current Densities

Enhancement of the 77 K irreversibility field and critical current density of (Bi,Pb)2Sr2Ca 2Cu3Ox tapes by manipulation of the final cooling rate

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