Enhancement of critical current density in (Ba,Na)Fe <sub>2</sub> As <sub>2</sub> round wires using high-pressure sintering
Sunseng Pyon, Daisuke Miyawaki, Tsuyoshi Tamegai, Satoshi Awaji, Hijiri Kito, Shigeyuki Ishida, Yoshiyuki Yoshida
Abstract
Abstract We fabricated (Ba,Na)Fe 2 As 2 superconducting wires using the powder-in-tube method and hot isostatic pressing. By improving powder synthesis processes compared with previous studies, highly pure raw materials for the wire fabrication were obtained. The largest transport critical current density ( J c ) reached 40 kA cm −2 at T = 4.2 K under a magnetic field of 100 kOe. This value exceeds not only the value of transport J c of the previous (Ba,Na)Fe 2 As 2 wire but also those of all iron-based superconducting round wires. Improvements of polycrystalline powder synthesis play a key role for the enhancement of J c . Furthermore, it was clarified that higher densification by high-pressure sintering and the texturing of grains in the core of the wire due to drawing also increased J c effectively. Advantages of (Ba,Na)Fe 2 As 2 wires compared with (Ba,K)Fe 2 As 2 wires are also discussed.