Magnetic levitation forces of multi-seeded melt-growth processed Y_1.6Ba_2.3Cu_3.3O_xbulk superconductors with artificial holes

In this study, Y_1.6Ba_2.3Cu_2.3O_x (YBCO) bulk superconductors were fabricated using a multiple-seeded melt-growth (MSMG) process. The number of seeds (n) varied from 1 to 6. Magnetic levitation forces at 77 K were measured for the YBCO samples cooled under field-cooled (FC) and zero-field-cooled (ZFC) procedures. The maximum repulsive force (F_max) of the n = 1 sample under ZFC conditions was 64.7 N. As n increased to 4, 5, and 6, F_max decreased to 60.9 N, 57.6 N, and 54.3 N, respectively. The reduction in F_max with increasing n was less than 20% compared to the n=1 sample. In contrast, the F_max of the YBCO samples measured under FC was lower than that measured under ZFC. Specifically, the F_max of the n = 1, n = 4, n = 5, and n = 6 samples under FC were 19.9 N, 25.9 N, 23.9 N, and 23.9 N, respectively. Due to the magnetic flux pinning under FC, the attractive forces (22-24 N) were much larger than those (below 5 N) under ZFC. In both cooling conditions, the levitation forces slightly decreased as n increased. Despite the decrease in magnetic levitation forces with increasing n, the process offers the advantage of shorter processing times. Consequently, the MSMG process is considered a cost-effective method for producing large-area YBCO bulk superconductors.