Hot pressing to enhance the transport Jc of Sr0.6K0.4Fe2As2 superconducting tapes

TLDR

The study systematically examined how hot‑pressing temperatures between 850 °C and 925 °C affect c‑axis texture, resistivity, hardness, microstructure, and critical‑current properties of Sr₀.₆K₀.₄Fe₂As₂ tapes. Hot‑pressed Sr₀.₆K₀.₄Fe₂As₂ tapes achieved record‑high critical currents—1.2 × 10⁵ A/cm² at 4.2 K/10 T and ~1.0 × 10⁵ A/cm² at 14 T—with weak field dependence, making them competitive with conventional and MgB₂ conductors for high‑field applications.

Abstract

High-performance Sr0.6K0.4Fe2As2 (Sr-122) tapes have been successfully fabricated using hot pressing (HP) process. The effect of HP temperatures (850-925 C) on the c-axis texture, resistivity, Vickers micro-hardness, microstructure and critical current properties has been systematically studied. Taking advantage of high degree of c-axis texture, well grain connectivity and and large concentration of strong-pinning defects, we are able to obtain an excellent Jc of 1.2x10^5 A/cm^2 at 4.2 K and 10 T for Sr-122 tapes. More importantly, the field dependence of Jc turns out to be very weak, such that in 14 T the Jc remains ~1.0x10^5 A/cm^2. These Jc values are the highest ever reported so far for iron-pnictide wires and tapes, achieving the level desired for practical applications. Our results clearly strengthen the position of iron-pnictide conductors as a competitor to the conventional and MgB2 superconductors for high field applications.