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Protocols and methodologies for acquiring and analyzing critical-current versus longitudinal-strain data in Bi2Sr2CaCu2O8+x wires

Journal Article · · Superconductor Science and Technology

In the literature on Bi2Sr2CaCu2O8+x (Bi-2212) superconducting wires, it is evident that measurement protocols for transport critical-current Ic versus longitudinal strain epsilon and definitions of the so-called 'strain limit' are generally dissimilar. Yet, values obtained for the 'strain limit' are frequently assimilated to being those of the irreversible strain limit ϵirr, regardless of the Ic degradation-criterion used to define it. In effect, ϵirr should correspond specifically to the Ic(ϵ) irreversibility onset, where crack formation in Bi-2212 filaments presumably starts. Because Ic(ϵ) degradation remains progressive over a fairly wide strain range beyond ϵirr, the different Ic degradation-criteria in use do not yield to the same result and, thus, are not equivalent from metrology perspective. Indeed, in studying densified samples of a modern Bi-2212 round wire, we found ϵirr ≈ 0.4% and ϵ5% ≈ 0.6% (ϵ5% being the strain where Ic degrades by 5%). In this paper, we outline and suggest Ic(ϵ)-measurement protocols and data-analysis methodologies in the hope to converge the various approaches taken for studying Bi-2212 strain properties and, thus, remove related result discrepancies. A unified approach would enable more objective data comparisons among laboratories and among different Bi-2212 conductors. It would pave the way for more rigorous studies of effects potentially associated with wire design, powder, heat treatments, and other such parameters on the conductor's strain properties.

Research Organization:
Florida State Univ., Tallahassee, FL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF); USDOE
Grant/Contract Number:
SC0017657; DMR-1644779; DMR-2128556
OSTI ID:
2481137
Alternate ID(s):
OSTI ID: 2479938; OSTI ID: 2497800
Journal Information:
Superconductor Science and Technology, Vol. 38, Issue 1; ISSN 0953-2048
Publisher:
IOP PublishingCopyright Statement
Country of Publication:
United States
Language:
English

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