Fabrication of small superconducting coils using (Ba,A)Fe2As2 (A: Na, K) round wires with large critical current densities

TL;DR

This paper demonstrates the fabrication of small superconducting coils from (Ba,A)Fe2As2 wires with high critical current densities, achieving record Jc values and magnetic fields, using powder-in-tube and hot-isostatic-press techniques.

Contribution

It introduces a new fabrication process for (Ba,A)Fe2As2 superconducting coils with record critical current densities and magnetic performance.

Findings

Critical currents of 60 A and 66 A for (Ba,Na)Fe2As2 and (Ba,K)Fe2As2 coils.

Maximum transport critical current density of 54 kA/cm² at 4.2 K under 100 kOe.

Achieved magnetic fields of approximately 2.5-2.6 kOe at the coil center.

Abstract

We report the fabrication of small (Ba,A)Fe2As2 (A: Na, K) coils using 10 m-class long round wires, fabricated by powder-in-tube (PIT) method. Coils are sintered using hot-isostatic-press (HIP) technique after glass-fiber insulations are installed. Critical current (Ic) of the whole coil using (Ba,Na)Fe2As2 and (Ba,K)Fe2As2 are 60 A and 66 A under the self-field, and the generated magnetic fields at the center of the coil reach 2.6 kOe and 2.5 kOe, respectively. Furthermore, the largest transport critical current density (Jc) and Ic in (Ba,Na)Fe2As2 wires picked up from the coil reach 54 kAcm-2 and 51.8 A at T = 4.2 K under a magnetic field of 100 kOe, respectively. This value exceeds transport Jc of all previous iron-based superconducting round wires. Texturing of grains in the core of the wire due to the improvement of the wire drawing process plays a key role for the enhancement of Jc.