Progress in wire fabrication of iron-based superconductors

Abstract

Iron-based superconductors, with Tc values up to 55 K, are of great interest\nfor applications, due to their lower anisotropies and ultrahigh upper critical\nfields. In the past 4 years, great progress has been made in the fabrication of\niron-based superconducting wires and tapes using the powder-in-tube (PIT)\nprocessing method, including main three types of 122, 11, and 1111 iron-based\nparent compounds. In this article, an overview of the current state of\ndevelopment of iron-based superconducting wires and tapes is presented. We\nfocus on the fabrication techniques used for 122 pnictide wires and tapes, with\nan emphasis on their meeting the critical current requirements for making\nhigh-performance conductors, such as a combination of using Ag sheath, addition\nelement and optimized heat treatment to realize high Jc, ex situ process\nemployed to reduce non-superconducting phases and to obtain a high relative\ndensity, and a texture control to improve grain connectivity. Of particular\ninterest is that so far transport Jc values above 10^4 A/cm^2 at 4.2 K and 10 T\nare obtained in 122 type tapes, suggesting that they are prospective candidates\nfor high-field applications. Finally, a perspective and future development of\nPIT pnictide wires are also given.\n