Fabrication and properties of nano-CeO2 doped Y-Ba-Cu-O bulk superconductors

Single-domain Y-Ba-Cu-O (YBCO) bulk superconductors can be widely used in the superconducting maglev, cryomagnets, motors/generators fields. In order to improve the performance of the YBCO bulk superconductors further, in this work, nano- CeO2 doped YBCO bulk superconductors are fabricated by two infiltration growth techniques (011-IG and 211-IG) respectively, in which two solid pellets of compositions Y-2 O-3 +1.15BaCuO(2) +0.1CuO+1wt.% nano-CeO2 and Y-2 BaCuO5 (Y-211)+1 wt.% nano-CeO2 are employed. And a novel pit-type seeding mode is used to prevent the film seed from moving in the heat treatment process, then the growth morphologies, microstructures and superconducting properties of the samples are investigated. The results show that at a low doping level (1 wt.%), the normal growth of the YBCO crystal is not affected, and fully-grown single-domain YBCO bulk superconductors can be successfully prepared by the two techniques. Furthermore, the positions of the seeds do not move at all, which proves the effectiveness of the new seeding mode. The perpendicular growth sector boundaries on the top surfaces of the samples and clear (00 l ) series X-ray diffraction (XRD) peaks both prove the high c -axis orientations and high growth quality of the samples . The scanning electron microscopy (SEM) results indicate that the nano-CeO2 doping can effectively refine the sizes of the Y-211 micro-particles in the bulk superconductors, and this method is applicable to both techniques. Low-temperature magnetization measurement shows that the nano-CeO (2) doped sample prepared by the 011-IG method shows obviously better J (c) property than the undoped sample at low fields, indicating that the refined Y-211 particles can effectively enhance the delta l -type pinning. In addition, compared with the 211-IG-processed sample, the 011-IG-processed sample performs better in terms of levitation force, microstructure and J(c) property, thus the 011-IG method is a more promising preparation process. The results of this study are important in improving the performance of the YBCO bulk superconductors and optimizing the fabrication technique further.