Progress in wire fabrication of iron-based superconductors

TL;DR

This paper reviews recent advances in the fabrication of iron-based superconducting wires and tapes, highlighting techniques to achieve high critical current densities suitable for high-field applications.

Contribution

It provides a comprehensive overview of fabrication methods, focusing on 122 pnictide wires and tapes, and discusses strategies to enhance their performance for practical use.

Findings

Transport Jc above 10^4 A/cm^2 at 4.2 K and 10 T in 122 tapes

Use of Ag sheath, additives, and optimized heat treatment improves Jc

Ex situ process and texture control enhance grain connectivity

Abstract

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