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Influence of the Oxygen Partial Pressure on the Phase Evolution During Bi-2212 Wire Melt Processing
C. Scheuerlein1, J. Andrieux2, M.O. Rikel3, J. Kadar4, C. Doerrer1, M. Di Michiel5, A. Ballarino1, L. Bottura1, J. Jiang6, F. Kametani6, E.E. Hellstrom6, D.C. Larbalestier6
1CERN, CH 1211 Geneva 23, Switzerland
2Université Claude Bernard Lyon 1, LMI–UMR CNRS No. 5615, 69622 Villeurbanne, France
3Nexans SuperConductors GmbH, Germany
3Nexans SuperConductors GmbH, Germany
4Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
5The European Synchrotron, ESRF, 71 avenue des Martyrs, 38000 Grenoble, France
6National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
6National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
E-mail: [email protected]h
Abstract — We have studied the influence of the oxygen partial pressure pO2 up to 5.5 bar on the phase changes that occur during melt processing of a state-of-the-art Bi-2212 multifilamentary wire. Phase changes have been monitored in situ by high energy synchrotron X-ray diffraction (XRD). We found that the stability of Bi-2212 phase is reduced with increasing pO2. For pO2>1 bar a significant amount of Bi-2212 phase decomposes upon heating in the range 400 to 650 °C. The extent of decomposition strongly increases with increasing pO2, and at pO2=5.5 bar Bi 2212 decomposes completely in the solid state. Textured Bi 2212 can be formed during solidification when pO2 is reduced to 0.45 bar when the precursor is molten. Since the formation of current limiting second phases is very sensitive to pO2 when it exceeds 1 bar, we recommend to reduce the oxygen partial pressure below the commonly used pO2=1 bar, in order to increase the pO2 margins and to make the overpressure process more robust.
Keywords (Index Terms) — Bi-2212, melt processing, XRD.
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), January 2016.
Submitted September 18, 2015; Selected November 8, 2015. Reference No. ST485; Category 5.
EUCAS 2015 preprint 3A-WT-P-01.01. The final paper version was published online in IEEE Trans. Appl. Supercond. (IEEE Xplore) DOI: 10.1109/TASC.2016.2533574, April 2016.
Submitted September 18, 2015; Selected November 8, 2015. Reference No. ST485; Category 5.
EUCAS 2015 preprint 3A-WT-P-01.01. The final paper version was published online in IEEE Trans. Appl. Supercond. (IEEE Xplore) DOI: 10.1109/TASC.2016.2533574, April 2016.