Microstructure and J/sub c/ improvements in overpressure processed Ag-sheathed Bi-2223 tapes

Yuan, Ye; Jiang, J.; Cai, X. Y.; Patnaik, S.; Polyanskii, A.A.; Hellstrom, E. E.; Larbalestier, D. C.; Williams, R. K.; Huang, Yibing

doi:10.1109/tasc.2003.812047

Cited by 11 publications

(18 citation statements)

References 12 publications

(16 reference statements)

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“…17 We showed that OP processing reduced the crack density and porosity by 11%-16% and increased J c ͑SF, 77 K͒ by 75% to 59 kA/cm 2 and J c ͑0.1 T, 77 K͒ by 82% to 22 kA/cm 2 compared to samples processed identically at 1 bar. The mass density of OP processed samples reached 97% of 2223 theoretical density.…”

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confidence: 65%

“…These FHTϩ1b and FHTϩOP samples were annealed using a heat treatment cycle similar to that published elsewhere. 17 The total OP pressure of the Ar/O 2 mixture was 148 bar. The calculated oxygen partial pressure (pO 2 ) was 0.081 bar a͒ Electronic mail: yongwenyuan@wisc.edu APPLIED PHYSICS LETTERS VOLUME 84, NUMBER 12 22 MARCH 2004 based on the ideal gas law, and the oxygen fugacity was 0.075 and 0.084 bar at room temperature and 820°C, respectively, based on the Lewis-Randall law for nonideal gas.…”

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confidence: 99%

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Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Yuan

Jiang

Cai

et al. 2004

Applied Physics Letters

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Overpressure ͑OP͒ processing otherwise fully treated, commercial Ag-sheathed multifilament (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x ͑2223͒ composite conductors increased the critical current density J c ͑0.1 T, 77 K͒ by 37% to 30.8 kA/cm 2 and the self-field J c ͑SF, 77 K͒ to 69.6 kA/cm 2 . These improvements were obtained on full-size high current conductors such that critical current I c ͑0.1 T, 77 K͒ reached 80.6 A and I c ͑SF, 77 K͒ 181.7 A, even though there was a very strong self-field suppression of I c . Estimated values for the non-self-field-limited I c and J c ͑0 T, 77 K͒ reached 235 A and 90 kA/cm 2 . Scanning electron microscopy and superconducting quantum inference device measurement revealed that OP processing effectively suppressed cracks, porosity, and the volume fraction of the Bi 2 Sr 2 Ca 1 Cu 2 O y ͑2212͒ phase, which are all major current-limiting mechanisms in present 2223 conductors.

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confidence: 65%

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confidence: 99%

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Yuan

Jiang

Cai

et al. 2004

Applied Physics Letters

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“…Thecoreofthefilamentsiswheremostoftheresidualsecondary phases,includingBi-2212,andporosityarelocated.Thisistruefor both monocore or multifilament tapes. In this region, many of the Bi-2223grainsaremisalignedrelativetothesilverinterface.Overpressureprocessinghasbeenshowntobeeffectiveforreducingthe porosity in the core [15]. Changes in the phase assemblage and/or reductionsinthesecondaryphasecontenthavebeenobtainedwith variations in the heat treatments [2], [11], [16], [17].…”

Section: Discussionmentioning

confidence: 99%

A Shell Model for the Filament Structure of Bi-2223 Conductors

Holesinger

Kennison

Liao

et al. 2005

IEEE Trans. Appl. Supercond.

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Abstract-Phase development during the first few minutes of heat treatment of first generation (Bi Pb) 2 Sr 2 Ca 2 Cu 3 O y (Bi-2223) multifilamentary wires determines to a large extent the overall microstructure, the efficiency of primary phase development, competing secondary phase development, texture evolution, and grain-to-grain connectivity. It is shown that the filament structure of these wires can be described in terms of a shell model. The shell next to the silver sheath is comprised of well-formed Bi-2223 colonies grapho-epitaxially aligned to the silver sheath and only a few grains (average one colony) thick. Inside this shell is a less well-aligned, less phase pure, more porous Bi-2223 structure through which current is carried in a nonuniform manner as shown by MOI.

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“…If the formation of impurity phases can be decreased, critical current density will be increased. Recently, over pressure processing was introduced to increase superconducting filament density to improve critical current property [5], [6]. It was also reported the critical current density could be improved through the transformation of Bi-2212 phase of precursor powder to orthorhombic structure from tetragonal structure before rolling process [7].…”

Section: Influence Of Modification Of Annealing and Sheathmentioning

confidence: 99%

Influence of Modification of Annealing and Sheath Materials on Critical Current Density of Bi-2223/Ag Tapes

Kim²,

Yang

et al. 2005

IEEE Trans. Appl. Supercond.

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It is important to improve critical current density of silver-sheathed Bi-2223 tapes for practical applications of material. Bi-2223/Ag superconducting wires with various sheath materials were fabricated by stacking, drawing process with different pre-annealing schedules. Two kinds of powders were prepared. One was pre-annealed at 760 C and low oxygen partial pressure, and the other was only calcined state. Before rolling process, round wires were pre-annealed at 760 C and in a low oxygen partial pressure. Bi-2223/Ag conductor was needed softening annealing at low temperature during drawing process because pre-annealed precursor powder brought about decrease in workability. Pre-annealing let tetragonal structure of Bi-2212 phase of precursor transform to orthorhombic structure and reduce the fraction of second phases at superconducting wire, which could increase critical current density. However the breakages occurred at Ag-alloy sheathed long Bi-2223/Ag tapes during rolling after pre-annealing. Several pre-annealing scenarios were introduced to reduce the breakages during rolling process. We could achieve proper pre-annealing conditions for Ag-alloy clad Bi-2223 tapes by the analysis of mechanical properties. We could achieve highest Je of 8800 A cm 2 at Bi-2223 tape by two-step pre-annealing.

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Microstructure and J/sub c/ improvements in overpressure processed Ag-sheathed Bi-2223 tapes

Cited by 11 publications

References 12 publications

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

A Shell Model for the Filament Structure of Bi-2223 Conductors

Influence of Modification of Annealing and Sheath Materials on Critical Current Density of Bi-2223/Ag Tapes

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