A Novel Top Seeding Method for Reliable Growth of Single-Grain YBCO Bulk Superconductor with High Levitation Property above 26 N/cm2

A novel top seeding method based on the NdBCO/YBCO/MgO film seed placed in the top pit of the precursor solid pellet was proposed herein and was used to fabricate single-grain YBCO bulk superconductors by the 011-type infiltration growth technique. Y2O3 and CeO2 nanopowders were used in the solid pellet to improve the microstructure in the final obtained bulk. The results indicate that this novel seeding method can be used to simultaneously fix the seed and ensure the grain growth from the bottom NdBCO layer of the seed. Repeated experiments prove the reliability of the method. Scanning electron microscopy images revealed that more refined nanoprecipitates (∼100 nm in size) with local high concentrations were present in the sample microstructure. The maximum levitation force of the sample reached 63.63 N and the force density was calculated as 26.45 N/cm2, representing a very high levitation property that meets the demands of practical applications. Consequently, this study provides a reliable preparation process for high-quality YBCO bulks that is essential for the batch-production of REBCO bulk materials for large-scale applications.