Longitudinal Magnetic Field Effect and Influence of Anisotropy of B_c2 in Critical Current Density of YBCO Superconducting Tape

Abstract:

As a high-temperature superconducting material, YBCO superconducting tape has great potential for use in power transmission. However, the critical current density (J_c) in superconducting cables is currently too low for practical applications. The longitudinal magnetic field effect is an effective way to improve the J_c of superconducting materials. J_c in the longitudinal magnetic field (LMF) is greater than J_c in the transverse magnetic field (TMF). On the other hand, the anisotropy of the upper critical field (B_c2) refers to the phenomenon that the B_c2 of superconducting materials changes when the direction of the external magnetic field changes from the ab plane to the c-axis of the YBCO superconducting tape. The objective of this study was to investigate the effects of the longitudinal magnetic field effect and the anisotropy of B_c2 on the J_c characteristics of YBCO superconducting tape. Two cases were set up in this study. In case 1, the direction of the external magnetic field is always parallel to the surface of the YBCO superconducting tape, while in case 2, the direction of the external magnetic field changes from parallel to the surface to perpendicular to the surface. By changing the experimental conditions, J_c was measured at different magnetic field strengths (B), different magnetic field directions (ϕ) and different temperatures (T). The influence of each variable on J_c in the two cases was clarified. Through the experimental results and discussions, the following conclusions were drawn: In comparison to the transverse magnetic field, J_c is increased by up to 30 times in the longitudinal magnetic field. In case 1, the main factor affecting J_c is the LMF effect. In the high-temperature region (80 K), the LMF effect on J_c is significantly greater than in the low-temperature region (40 K). In case 2, as the angle (ϕ) between the direction of the applied magnetic field and the current increases, B_c2 in case 2 gradually decreases, while B_c2 in case 1 remains unchanged, which is the reason for the more significant change in J_c in case 2. Compared with case 1, in case 2, in the low-temperature region (40 K), the LMF effect is the main factor affecting J_c. As T increases, the LMF effect on J_c gradually decreases, and the anisotropy of B_c2 gradually increases. In the high-temperature region (80 K), the anisotropy of B_c2 becomes the main factor affecting J_c.

• Periodical: Materials Science Forum (Volume 1150)
• Pages: 93-101
• DOI: https://doi.org/10.4028/p-JkF4tJ
• Online since: June 2025
• Authors: Yaowei Liu*, Bao Rong Ni
• Keywords: Anisotropy of B_c2, J_c Characteristics, Longitudinal Magnetic Field Effect, YBCO Superconducting Tape

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