High-performance Ba1−xKxFe2As2 superconducting tapes with grain texture engineered via a scalable fabrication

Nowadays the development of high-field magnets strongly relies on the performance of superconducting materials. Iron-based superconductors (IBSs) exhibit high upper critical fields and low electromagnetic anisotropy, making them particularly attractive for high-field applications, especially in particle accelerator magnets, nuclear magnetic resonance spectrometers, medical magnetic resonance imaging systems and nuclear fusion reactors. Herein, through an industrially scalable manufacturing strategy, a practical-level critical current density up to 1.1×105 A cm−2 at 4.2 K in an external magnetic field of 10 T was achieved in Cu/ Ag composite-sheathed Ba1−xKxFe2As2 (Ba122) superconducting tapes. The preparation strategy combines flat rolling to induce grain texture and subsequent hot-isostatic-pressing densification. By varying the parameters of rolling, the degree of grain texture was engineered. It is found that the transport properties of the Ba122 tapes can be enhanced by applying a large amount of deformation during rolling, which can be attributed to the improved degree of c-axis texture. Microstructure characterizations on the highest-performance tape demonstrate that the Ba122 phase has a uniform element distribution and small grains with good connectivity. Grain boundary pinning is consequently enhanced as proved by large currents circulating through the sample even at 25 K. Our work proves that Cu/Ag composite-sheathed Ba122 superconducting tapes can be a promising competitor for practical high-field applications in terms of the viable, scalable and cost-effective fabrication strategy applied and the high transport properties achieved in this work.