Multi-seeding melt growth process of bulk Y-Ba-Cu-O superconductors for engineering applications

We have prepared polycrystalline and four-domain Y-Ba-Cu-O superconductors in a molar ratio of Y123: Y211 = 10: 4 with lwt% Ce02 addition by melt-processing in air. Trapped field measurements showed that four sharp peaks were observed in a four-domain bulk sample, showing that four grains were successfully formed without defects by a multi-seeding method. Force measurements showed that a four-domain Y-Ba-Cu-O sample exhibited higher repulsive forces and smaller hysteresis loops than polycrystalline Y-Ba-Cu-O sample during the increasing and decreasing field processes, which implies higher pinning performance of the four-domain sample. With the aim of studying the transferable torque forces, we used a multi-pole magnet circuit with NSNS configuration. We confirmed that with the interaction of the magnet circuit, a four-domain Y-Ba-Cu-O sample showed larger forces than a polycrystalline sample both in the field-cooled and the zero-field-cooled mode. We also measured the torque forces acting between the magnet circuit and bulk Y-Ba-Cu-O samples by twisting the magnet circuit in the levitated state. Again a four-domain Y-Ba-Cu-O sample exhibited much higher torque forces than a polycrystalline sample. These results showed that multi-seeded Y-Ba-Cu-O sample with four-domains can be used for torque transfer apllications.