The influence of carbon on melt processing Ag sheathed Bi2Sr2CaCu2O8 tape

Zhang, W.; Hellstrom, E. E.

doi:10.1016/0921-4534(94)90065-5

Cited by 34 publications

(12 citation statements)

References 19 publications

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“…Solid state Ag and its alloys are widely used as sheath materials for wires and tapes [41,[68][69][70][71][72][73][74][75][76][77][78] and therefore the influence of Ag on the phase relation has to be studied. As Ag is not dissolved in the 2212 and 2223 phases, as well as the known cuprates of the system, the assumption is legitimate that Ag does not significantly affect the system.…”

Section: The System Bi 2 O 3 -Pbo-sro-cao-cuo-agmentioning

confidence: 99%

“…At temperatures above about 865 • C several different phase equilibria were observed containing the 2212 phase and liquids in which Ag is either completely dissolved (figure 20) or also present as a solid phase [20,[81][82][83][84][85]. This phenomenon is important for the preparation of Agcontaining 2212 ceramics.…”

Section: The System Bi 2 O 3 -Pbo-sro-cao-cuo-agmentioning

confidence: 99%

“…Partial melt processing is one of the most widely used techniques for the processing of textured 2212 wires and tapes [41,75,85,87]. During melting several peritectic reactions occur depending on the temperature, the oxygen partial pressure [88] and even the Ag content.…”

Section: Melt Equilibria Of the 2212 And 2223 Phasesmentioning

confidence: 99%

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Phase diagram studies in the system Bi - Pb - Sr - Ca - Cu - O - Ag

Majewski

1997

Supercond. Sci. Technol.

110

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Phase diagram studies with emphasis on the high temperature superconducting phases Bi 2+x Sr 2−y Ca 1+y CuO 8+d (2212 phase) and (Bi, Pb) 2+x Sr 2−y Ca 2+y CuO 10+d (2223 phase) are reviewed in this article. The phase relations of the Bi 2 O 3 -SrO-CaO-CuO and the homogeneity regions of the 2212 and 2223 phases have been studied in detail at various temperatures and oxygen partial pressures. However, the Pb-doped system has been investigated less comprehensively. The studies of this system are mostly focused on the 2212 and 2223 phase and the experimental work regarding the 2223 phase is often concentrated on the processing of 2223 samples with high critical current density and not on the preparation of single phase 2223 ceramics.The investigations of the Ag-containing system have just started. Nevertheless, first results show that Ag significantly influences the phase relations and the temperature dependence of the cation solubilities of the 2212 and 2223 solid solutions. These results indicate that the obtained phase diagrams of the system Bi 2 O 3 -PbO-SrO-CaO-CuO cannot be applied without caution when Ag is present. Therefore, as Ag is widely used as a sheath material for the processing of 2212 and 2223 wires and tapes, the investigation of the entire Ag-containing system is inevitable.

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Section: The System Bi 2 O 3 -Pbo-sro-cao-cuo-agmentioning

confidence: 99%

Section: The System Bi 2 O 3 -Pbo-sro-cao-cuo-agmentioning

confidence: 99%

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Phase diagram studies in the system Bi - Pb - Sr - Ca - Cu - O - Ag

Majewski

1997

Supercond. Sci. Technol.

110

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“…Internal gases may include residual air and humidity present in as-drawn wires, gases released as a result of contaminants adsorbed on powder surfaces [24] and solid remnants in powder gasifying upon heating. Contaminants and gas impurities may include hydrates, hydroxides, carbonates [25], nitrates, and residues such as wire drawing lubricants (hydrocarbons); they transform to gases (H 2 O, CO 2 , or NO 2 ) upon heating. One evidence for this conjecture is that tapes with high carbon contents were observed to swell over long length, crack, or even bulge locally [23].…”

Section: Introductionmentioning

confidence: 99%

Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires

Shen

Ghosh

Cooley

et al. 2013

Journal of Applied Physics

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High engineering critical current density J E of >500 A/mm 2 at 20 T and 4.2 K can be regularly achieved in Ag-sheathed multifilamentary Bi 2 Sr 2 CaCu 2 O x (Bi-2212) round wire when the sample length is several centimeters. However, J E (20 T) in Bi-2212 wires of several meters length, as well as longer pieces wound in coils, rarely exceeds 200 A/mm 2 . Moreover, long-length wires often exhibit signs of Bi-2212 leakage after melt processing that are rarely found in short, open-end samples. We studied the length dependence of J E of state-of-the-art powder-in-tube (PIT) Bi-2212 wires and gases released by them during melt processing using mass spectroscopy, confirming that J E degradation with length is due to wire swelling produced by high internal gas pressures at elevated temperatures [1,2]. We further modeled the gas transport in Bi-2212 wires and examined the wire expansion at critical stages of the melt processing of as-drawn PIT wires and the wires that received a degassing treatment or a colddensification treatment before melt processing. These investigations showed that internal gas pressure in long-length wires drives creep of the Ag sheath during the heat treatment, causing wire to expand, lowering the density of Bi-2212 filaments, and therefore degrading the wire J E ; the creep rupture of silver sheath naturally leads to the leakage of Bi-2212 liquid. Our work shows that proper control of such creep is the key to preventing Bi-2212 leakage and achieving high J E in long-length Bi-2212 conductors and coils.

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“…A precise temperature measurement was not possible during this experiment, but Bi-2212 melting occurred at significantly lower temperature than has been observed in the composite wires. The rather low melting temperature of the precursor granulate may be related to the absorption of CO 2 from air [18], and possibly to differences in the oxygen partial pressure [19].…”

Section: Density Of the Loose Precursor Powder Used In The Pitmentioning

confidence: 99%

Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

Scheuerlein

Michiel

Scheel

et al. 2011

Supercond. Sci. Technol.

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Recent study of the current-limiting mechanisms in Bi-2212 round wires has suggested that agglomeration of the residual Bi-2212 powder porosity into bubbles of filament-diameter size occurs on melting the Bi-2212 filaments.These pores introduce a major obstacle to current flow, which greatly reduces the critical current density (J c ). Here we present an in situ non-destructive tomographic and diffraction study of the changes occurring during the heat treatment of wires and starting powder, as well as a room temperature study of ex situ processed wires. The in situ through-process study shows that the agglomeration of residual porosity is more complex than previously seen.Filament changes start with coalescence of the quasi-uniform and finely divided powder porosity into lens-shaped defects at about 850 0 C when the Bi-2201 impurity phase decomposes before the Bi-2212 starts to melt. These lens-shaped voids grow to bubbles of a filament diameter on melting of the Bi-2212 and continue to lengthen and then to agglomerate across multiple filaments while the filaments are in the liquid state. The experiment makes clear why melt processing is vital to developing high J c and also shows how rearrangement of the residual filament porosity on melting imposes a strong longitudinal inhomogeneity in each filament. Reducing the bubble density is clearly an important path to reaching much higher J c values in Bi-2212 round wires. Synchrotron micro-tomography is an exceptionally powerful technique for studying the spatial extent of the porosity on a scale of about 2 m and larger.Published in Superconductor Science and Technology (2011) Geneva, Switzerland CERN-ATS-2011-243December 2011 AbstractRecent study of the current-limiting mechanisms in Bi-2212 round wires has suggested that agglomeration of the residual Bi-2212 powder porosity into bubbles of filament-diameter size occurs on melting the Bi-2212 filaments. These pores introduce a major obstacle to current flow, which greatly reduces the critical current density (J c ). Here we present an in situ non-destructive tomographic and diffraction study of the changes occurring during the heat treatment of wires and starting powder, as well as a room temperature study of ex situ processed wires. The in situ through-process study shows that the agglomeration of residual porosity is more complex than previously seen. Filament changes start with coalescence of the quasi-uniform and finely divided powder porosity into lens-shaped defects at about 850 • C when the Bi-2201 impurity phase decomposes before the Bi-2212 starts to melt. These lens-shaped voids grow to bubbles of a filament diameter on melting of the Bi-2212 and continue to lengthen and then to agglomerate across multiple filaments while the filaments are in the liquid state. The experiment makes clear why melt processing is vital to developing high J c and also shows how rearrangement of the residual filament porosity on melting imposes a strong longitudinal inhomogeneity in each filament. Reducing the bubble density i...

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The influence of carbon on melt processing Ag sheathed Bi2Sr2CaCu2O8 tape

Cited by 34 publications

References 19 publications

Phase diagram studies in the system Bi - Pb - Sr - Ca - Cu - O - Ag

Phase diagram studies in the system Bi - Pb - Sr - Ca - Cu - O - Ag

Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires

Void and phase evolution during the processing of Bi-2212 superconducting wires monitored by combined fast synchrotron micro-tomography and x-ray diffraction

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