Influence on Processing and Magnetic Flux Properties of Single Grain YBCO Fabricated from Layered Precursor Powders

The fabrication of single domain Y-Ba-Cu-O(YBCO) bulk superconductors usually involves precursor pellets that contain a uniform distribution of YBa2Cu3O7-delta(Y123) and Y2BaCuO5(Y211) compounds. However, the concentration of Y211 phase particles in the fully melt processed superconducting bulk increases significantly with distance from the seed, leading to accumulation of Y211 phase particles and degradation of superconducting properties. By top seeded melt texture growth (TSMTG) process, single domain YBCO bulk superconductors at about 23 mm in diameters, and 9 mm in thickness were fabricated from layered precursor pellets and conventional precursor pellets, respectively. The growth morphology, microstructure and magnetic flux properties of both layered and conventional pellets were comparatively studied. The experiments suggest that the layered precursor pellets allow a sufficient growth in c growth sector, a more uniform distribution of Y211 phase in the matrix and a significant enhancement of the trapped field. Thus for the layered pellets, a trapped magnet field of 0.91 T is achieved at 77 K and the flux distribution is also of high symmetry. The present results are very valuable for further improving the properties of YBCO bulk superconductors.