Effects of Zn doping on superconducting properties of melt textured Y-Ba-Cu-O bulk superconductors

Zn doping which may induce a second peak effect in YBa2Cu3O7-delta (YBCO) has been opted as a regular technique to improve the trapped field and flux pinning stability of YBCO bulk superconductors for practical applications, such as quasi-permanent or maglev magnets. Here, the effects of Zn doping on the flux trapping performance of single domain YBCO bulk superconductors have been systematically investigated. The doping amount x varies from 0 to 1.0 mol%. We analyzed the critical transition temperature (T-c), critical current density (J(c)), trapped field (B-t) and the flux relaxation at various temperatures, and measured in addition the levitation force (F-L) for comparison. The doping amount of 0.6 mol% has been proven to be the optimal value, which enhances self-field J(c) by 243.3% at 30 K with an obvious secondary peak effect, resulting in great improvements in trapped field and flux stability. The holistic and local superconducting performances exhibit good agreement, demonstrating Zn-doping an effective method to improve flux pinning properties for practical applications.