Progress on iron-based superconducting wires for practical applications

Iron-based superconductors exhibit numerous advantages, including ultrahigh upper critical fields, high transition temperatures, low anisotropy, and remarkable transport current density. Furthermore, they can be made into superconducting wires and tapes by the economical powder-in-tube method. At present, the utilization of pressure sintering densification and grain texture technology has rendered the transport critical current density of iron-based superconducting tapes to exceed the practical level of 10(5) A/cm(2) under a magnetic field of 10 T. Compared with superconducting tapes, the wires exhibit a more symmetrical cross-sectional shape, which makes it easier to twist the cables, thereby reducing the electromagnetic coupling effect of the wires, improving current uniformity and stability, and meeting the requirements of high-field applications such as magnetic resonance imaging (MRI) systems, nuclear magnetic resonance (NMR) systems, high-energy accelerators, and nuclear fusion reactors. This article presents an overview of the development and current status of iron-based superconducting wires; systematically introduces precursor powder preparation, cold working processes, and heat treatment technologies; and elaborates on the microstructure and flux-pinning characteristics that influence the transport performance of wires, including wires with different metal sheathes and multifilament wires. Last, a summary of studies on iron-based superconducting wires is presented, and future development trends are discussed.