Effects on the Microstructure and Levitation Force Properties of Multi-Seeded YBCO Superconductors Using in Situ Self-Assembly Seeding Approach

By using the in situ self-assembly (ISSA) seeding approach with multi-seeded melt growth process, large rectangular YBa
₂
Cu
₃
O
_7-
δ
(YBCO) superconductors of 54 mm × 26 mm × 9 mm size were successfully prepared. In the thermal process, the ISSA seeding structure induced the emergence of the [110]-oriented growth zone ([110]
_GZ
), which rapidly expands to the edges of the sample, leading to the formation of a contamination-free crystal homojunction and an increase in the
ab
-plane growth rate. Here, ISSA seeding structures with different guiding orientations were placed in pairs on the precursor to fabricate a large-size multi-seeded YBCO superconductor. Samples were obtained with crystal boundaries of [110]
_GZ
colliding at 45°–45° and [110]
_GZ
being parallel to each other at 0°–0°, respectively. The study investigated how the orientation of the ISSA seeding structure impacts the formation of growth front grain boundaries and the properties of YBCO bulk. As the grain microstructure study indicates, the growth direction of colliding grains would impact the content of residual liquid phase melt impurities in the grain boundary. Following the collision of two [110]
_GZ
grains (45°–45°), only a small amount of liquid phase is left at the grain boundaries. This results in relatively clean grain boundaries, enhancing the intergranular properties. It's really helpful to achieve high performance in multi-seeded YBCO superconductor bulk.