Enhanced high-field transport critical current densities observed for the ex-situ PIT processed Ag/(Ba,K)Fe2As2 thin tapes

TL;DR

This study demonstrates that repeated rolling and heat treatment significantly enhance the critical current density of ex-situ PIT processed (Ba,K)Fe2As2 superconducting tapes with a simple Ag sheath, achieving record values and promising high-field applications.

Contribution

It introduces a simple, effective process of repeated rolling and heat treatment to improve transport Jc in (Ba,K)Fe2As2 tapes with Ag sheath, achieving record high Jc values.

Findings

Transport Jc of 4.4 x 10^3 A/cm^2 at 4.2 K and 10 T.

Jc-H curve remains stable up to 28 T.

Dense grain structure with c-axis alignment development.

Abstract

We found that the transport Jc of the ex-situ PIT processed (Ba,K)Fe2As2 (Ba-122) wire with single Ag sheath can be significantly enhanced by repeating the combined process of rolling and heat treatment. The transport Jc (4.2 K and 10 T) of 4.4 x 103 A/cm2 (Ic =15.7 A) was obtained for a thin tape of 0.3 mm in thickness, which is the highest value reported so far for the PIT processed 122 wires and tapes with a Ag sheath and processed by a conventional route. The measurement by a hybrid magnet showed that Jc-H curve maintains very small field dependence up to the strong magnetic field of 28 T as expected from the previously reported high Hc2 value. The core of the thin tape shows dense grain structure with less cracks and voids and indicates the development of c-axis alignment, although it is still incomplete. The researches to elucidate the origin of Jc enhancement and to have further improvement of transport Jc are now ongoing. The process is simple using a Ag single sheath and, therefore, more realistic technique for long length wire production.