  Nowadays the development of high-field magnets strongly relies on the
performance of superconducting materials. Iron-based superconductors 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 and cost-effective manufacturing strategy, a practical
level critical current density up to 1.1x10^5 A/cm2 at 4.2 K in an external
magnetic field of 10 T was achieved in Cu/Ag composite sheathed Ba0.6K0.4Fe2As2
superconducting tapes. The preparation strategy combines flat rolling to induce
grain texture and a 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 Ba1-xKxFe2As2 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
Ba1-xKxFe2As2 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 Ba1-xKxFe2As2 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.
