CERN Accelerating science

Published Articles
Report number	CERN-ACC-2016-0034
Title	Influence of the oxygen partial pressure on the phase evolution during Bi-2212 wire melt processing
Author(s)	Scheuerlein, C. (CERN) ; Andrieux, J. (Lyon U.) ; Rikel, M.O. (Nexans, Germany) ; Kadar, J. (U. Erlangen-Nuremberg (main)) ; Doerrer, C. (CERN) ; Di Michiel, M. (ESRF, Grenoble) ; Ballarino, A. (CERN) ; Bottura, L. (CERN) ; Jiang, J. (Natl. High Mag. Field Lab.) ; Kametani, F. (Natl. High Mag. Field Lab.) ; Hellstrom, E.E. (Natl. High Mag. Field Lab.) ; Larbalestier, D.C. (Natl. High Mag. Field Lab.)
Publication	2016
Imprint	2015-09-04
In:	IEEE Trans. Appl. Supercond. 26 (2016) 6400304
In:	12th European Conference on Applied Superconductivity, Lyon, France, 06 - 10 Sep 2015, pp.6400304
DOI	10.1109/TASC.2016.2533574
Subject category	Accelerators and Storage Rings ; 10: Future Magnets (MAG) ; 10.3: 5 T HTS Dipole Magnet Design and Construction
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.
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