Longitudinal Magnetic Field Effect in REBCO Tapes Investigated by Oxygen deficiency Control

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K14192
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: Tohoku University
• Principal Investigator: Okada Tatsunori 東北大学, 金属材料研究所, 助教 (50793775)
• Project Period (FY): 2021-04-01 – 2023-03-31
• Keywords: 超伝導 / REBCO / 臨界電流 / 磁束ピンニング / 銅酸化物超伝導体 / 鉄系超伝導体 / 酸素欠損 / 機械特性

Outline of Final Research Achievements

We introduced oxygen deficiency into commercial REBCO tapes and attempted to clarify the effect of oxygen deficiency on flux pinning through Jc measurements under a wide range of temperature, magnetic field, and angular conditions.
We observed that introduction of oxygen deficiency makes the critical temperature and carrier density decreased, the in-plane coherence length increased, and the inter-plane coherence length ξc decreased. Jc with the longitudinal magnetic field and Jc with the in-plane transverse magnetic field approached each other, which may be caused by the intrinsic pinning which became more effective due to the decrease in ξc. Furthermore, we evaluated the Jc characteristics of Bi2223 and K-Ba122 tapes and quantitatively described the effects of applied strain, grain boundaries and spherical pinning centers on magnetic flux pinning.
Optimization of tape design based on these results is expected to improve the properties of superconducting tapes.

Free Research Field

超伝導

Academic Significance and Societal Importance of the Research Achievements

超伝導線材における縦磁界効果は臨界電流を飛躍的に向上する手段として注目されているが、縦磁界臨界電流に対する人工ピン・酸素欠損の影響は明らかになっていなかった。本研究にて酸素欠損導入による超伝導特性の変化を明らかにした結果、人工ピンの導入や面間コヒーレンス長の縮小などを通じて面内横磁場に対する臨界電流値を向上させることで、超伝導線材の特性を向上できることが示唆された。
また、Bi2223線材・K-Ba122線材の臨界電流に対するひずみや粒界・球状ピンの影響を定量記述を実現したことで、マグネット等の設計が容易になる。
本研究で得た成果を踏まえた線材設計の最適化により、超伝導線材の特性向上が期待される。