Progress in Buffer-Supported Seeding Architectures for Reliable Epitaxial Growth of REBa2Cu3O7−δ Bulk Cryomagnets with Superior Properties

Abstract

Large-scale REBa2Cu3O7−δ (REBCO, RE = rare earth elements) superconducting crystals, whose excellent electromagnetic properties have been discovered over 30 years, possess considerable potential for scientific research and engineering applications. However, further development of these materials was hindered due to the lack of reliable fabrication processes. The controlled nucleation and growth of REBCO bulk cryomagnets for obtaining high crystallographic orientation and superior superconducting performance is strongly dependent on the seeding technique, including seeding architecture, seed material and seeding mode. In the most recent decade, a buffer layer technology has been developed for the growth of REBCO single grains, greatly enhancing the effectiveness of seeds. An overview of the most recent progress in seeding technology is presented by highlighting the advanced buffer-assisted seeding architectures. Distinctive functions of buffers are summarized as blocking the mutual contamination between the seed and the main pellet, enhancing thermal stability by a seed/buffer layer structure and improving the bulk crystallinity as a larger secondary homo-seed. The presented strategy gives valuable insight into the underlying mechanisms and provides tools for the seeding structural design in the growth of REBCO superconductors, which is scalable and can be extended to more functional oxide systems.