Radial and axial stiffness of superconducting bearings based on YBCO single-domain bulks processed with artificial holes

Superconducting magnetic bearings are becoming more widespread, due to the unique properties they provide. Their efficiency is unparallel, there are no issues such as contact, friction, and wear. They require low or minimal maintenance, no lubrication and they work under extreme conditions (cryogenic temperatures, high vacuum). In this contribution, the influence of geometric properties of superconducting bulks on the performance of superconducting bearings was studied. The main focus was paid to load capacity, radial and axial stiffnesses. Two samples with a significantly higher aspect ratio compared to conventional bulks were prepared. One of these samples was synthesized with artificially created holes. The samples were prepared using top-seeded melt-growth process with an additional source of a liquid phase in the form of an underlaying pad. The original thickness of 16 mm of the samples with a diameter of 28 mm was repeatedly ground down. Levitation force and trapped field were measured after each grinding step. Using this approach, the dependence of properties of the bulks on their thickness, scaling of these properties with thickness and the influence that artificial holes can make on the properties of finished single domain bulks were studied. The maximum levitation force was greatly improved for bulks with thicknesses of 2-6 mm. Such data is of the utmost importance in the field of superconducting YBCO single domain bulk ceramics, as it allows for better understanding and further improvement of both the manufacturing process and real-world applications of these materials.