Reversible effect of strain on transport critical current in Bi2Sr2CaCu2O8+x superconducting wires: A modified descriptive strain model

Published

December 5, 2011

Author(s)

Najib Cheggour, Xifeng Lu, T G. Holesinger, Theodore C. Stauffer, J Jiang, Loren F. Goodrich

Abstract

A reversible strain effect on transport critical current I_c was found in Bi₂Sr₂CaCu₂O_8+x (Bi-2212) high-temperature superconducting round wires. I_c showed unambiguous reversibility at 4 K and 16 T up to an irreversible strain limit of about 0.3 % in longitudinal tension, prompting hope that the Bi-2212 conductor has the potential to sustain mechanical strains generated in high-field magnets. However, I_c was not reversible under longitudinal compression and buckling of Bi-2212 grain colonies was identified as the main reason. A two-component model was proposed, which suggests the presence of mechanically weak and strong Bi-2212 components within the wire filaments. Porosity embedded in the weak component renders it structurally unsupported and, therefore, makes it prone to cracking under strain ε. I_c(ε) is irreversible in tension if the weak component contributes to the transport critical current but becomes reversible once connectivity of the weak component is broken through strain increase or cycling. A modified descriptive strain model was also developed, which illustrates the effect of strain in the Bi-2212 conductor and supersedes the existing descriptive model. Unlike the latter, the new model suggests that higher pre-compressive strains should improve I_c if buckling of Bi-2212 grains does not occur, and should result in a wider I_c(ε) plateau in the applied tensile regime without degradation of the initial I_c. The new model postulates that a reversible strain effect should exist even in the applied compressive strain regime if buckling of Bi-2212 grains could be prevented through elimination of porosity and mechanical reinforcement of the wire.

Citation

Superconductor Science and Technology

Volume

25

Pub Type

Journals

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Keywords

Reversible Strain Effect, Bi-2212, Strain Model, Critical Current, Buckling, Cracks, Porosity, Microstructure

Citation

Cheggour, N. , Lu, X. , Holesinger, T. , Stauffer, T. , Jiang, J. and Goodrich, L. (2011), Reversible effect of strain on transport critical current in Bi₂Sr₂CaCu₂O_8+x superconducting wires: A modified descriptive strain model, Superconductor Science and Technology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908512 (Accessed April 18, 2024)