Innovation of advanced functional high-Tc superconducting thin films by using discontinuous nano-scale linear defects

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04474
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: Kyushu Sangyo University (2021-2022); Kumamoto University (2019-2020)
• Principal Investigator: Sueyoshi Tetsuro 九州産業大学, 理工学部, 准教授 (20315287)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 高温超伝導体 / 臨界電流密度 / 磁束ピンニング / イオン照射

Outline of Final Research Achievements

We demonstrated the crossover from discontinuous columnar defects (CDs) to continuous ones depending on the irradiation angle of the same ion beam in high-Tc superconductors with anisotropic crystalline structure for the first time, by using 80 MeV Xe ion irradiation, which was capable of the formation of discontinuous CDs in the c-axis direction. In addition, the systematic introduction of CDs with different lengths to high-Tc superconducting films by using different ion beams revealed a new finding for the thermal relaxation of critical current density Jc: the segmentation of CDs further suppresses the relaxation rate at lower temperature. Furthermore, systematic studies for volume fractions of CDs controlled by their length and the irradiation fluence enabled us to find the influence of the volume fraction of CDs with different morphologies on Jc, which can be one of key factors to provide the breakthrough in the improvement of in-field Jc.

Free Research Field

電子材料工学

Academic Significance and Societal Importance of the Research Achievements

本研究では，異方的な結晶構造をもつ高温超伝導体においては，イオンビームの照射方向によって短尺状から連続な形状へと線状欠陥の連続性が変わることを，同一のイオンビームを用いて照射角度を変えて系統的に断面TEM観察することで，初めて明らかにした．また，イオン種，エネルギーの制御により，短尺状から連続な形状の線状欠陥を系統的に導入した高温超伝導薄膜を用いることで，磁束クリープに対する線状欠陥の短尺化の直接的な影響を明らかにした．以上の結果は，高温超伝導体の高Jc化に対して重イオンビームは，さらに高い自由度でピン止め点を導入できることを示し，その中で線状欠陥の短尺化が鍵であることを示唆している．