Promising critical current density characteristics of Ag-sheathed (Sr,Na)Fe₂As₂ tape

Abstract

We report the fabrication of (Sr,Na)Fe 2 As 2 superconducting tapes by the powder-in-tube technique and their characteristics, including the transport critical current density J c at 4.2 K up to 140 kOe, the magnetic J c estimated from magnetic hysteresis curves, magneto-optical (MO) images, and scanning electron microscopy images. In a tape sintered at 875 °C for 1 h, the transport J c reaches 26 kA/cm 2 at 4.2 K and 100 kOe for a field perpendicular to the tape surface. When the field is parallel to the tape surface, the magnetic J c exceeds the practical level of 100 kA/cm 2 at 4.2 K below 25 kOe. Analysis of the MO images reveals clear current discontinuity lines in the core, indicating that the current flows homogeneously and the connections between grains are strong in the core.

Enhancement of critical current density in (Ba,Na)Fe2As2 round wires using high-pressure sintering

“…Iyo et al reported that the transport J c for (Sr,Na)Fe 2 As 2 tapes at 20 K under a magnetic field of 25 kOe was superior to that for (AE',K)Fe 2 As 2 tapes [41]. The transport J c for (Sr,Na)Fe 2 As 2 tapes of 26 kA cm −2 at 4.2 K under 100 kOe, and that for (Ba,Na)Fe 2 As 2 tapes of 40 kA cm −2 at 4.2 K under 40 kOe, were also reported [42,45]. Very recently, J c in (Ba,Na)Fe 2 As 2 HIP round wire reached 150 and 20 kA cm −2 at self-field and 100 kOe, respectively [46][47][48].…”

“…In contrast to K-doped 122-type materials, the investigation of J c of single crystals and the fabrication of wires or tapes of Na-doped 122-type material, (AE,Na)Fe 2 As 2 (AE = Ba, Sr, or Ca) [37][38][39][40], have not been performed extensively, in spite of their comparable T c (∼34 K) to K-doped ones. Only recently, some studies of tapes and wires of (AE,Na)Fe 2 As 2 have been reported [41][42][43][44][45][46][47]. Iyo et al reported that the transport J c for (Sr,Na)Fe 2 As 2 tapes at 20 K under a magnetic field of 25 kOe was superior to that for (AE',K)Fe 2 As 2 tapes [41].…”

Fabrication and characterization of CaKFe4As4 round wires sintered at high pressure

“…For example, the fabrication of Na-doped SrFe 2 As 2 tapes and their promising J c characteristics have been reported recently. [35][36][37][38] Iyo et al reported that the transport J c for Na-doped SrFe 2 As 2 tapes at 20 K under a magnetic field of 25 kOe is superior to that for K-doped AEFe 2 As 2 tapes. 35) Suwa et al reported that the transport J c for Na-doped SrFe 2 As 2 tapes reaches 26 kA cm −2 under 100 kOe at 4.2 K. 36) Recently, new types of IBSs, e.g., the 1144 type with CaKFe 4 As 4 , have been developed.…”

“…[35][36][37][38] Iyo et al reported that the transport J c for Na-doped SrFe 2 As 2 tapes at 20 K under a magnetic field of 25 kOe is superior to that for K-doped AEFe 2 As 2 tapes. 35) Suwa et al reported that the transport J c for Na-doped SrFe 2 As 2 tapes reaches 26 kA cm −2 under 100 kOe at 4.2 K. 36) Recently, new types of IBSs, e.g., the 1144 type with CaKFe 4 As 4 , have been developed. 39) The structure of CaKFe 4 As 4 is similar to that of 122-type IBSs, and the Ca and K layers stack alternately along the c-axis.…”

Superconducting critical current density enhanced to 285 A cm−2 for Sr2VFeAsO3−δ tapes fabricated by ex situ powder-in-tube process

“…ron−based superconducting wires/tapes with superconducting critical temperature (T c ) > 20 K fabricated via the powder−in−tube (PIT) process, 1) were reported for ReFeAsO 1−x F x 2-4) (Re: Rare earth elements), Ae 1−x A x Fe 2 As 2 [5][6][7][8] (Ae: Alkali earth elements, A: Alkali elements), AeAFe 4 As 4 [9][10][11] and Sr 2 VFeAsO 3−δ . 12) In addition, superconducting tapes using FeSe 1−x Te x were reported 13,14) as well, though their T c s were lower than 20 K. Although the T c s of these iron−based superconductors are lower than those of cuprate superconductors, their upper critical magnetic fields (μ 0 H c2 ) are comparable.…”