Abstract:Instead of ordinal pure Ag, Ag-based Sn binary alloys (up to 7.5 at%Sn) with higher mechanical strength are used for the sheath material of ex situ powder-in-tube (PIT)-processed (Ba,K)Fe2As2(Ba-122) tapes. We found that the use of the Ag-Sn alloy enhances the densification and texturing of the Ba-122 core, resulting in higher transport, Jc. Moreover, the optimum heat treatment temperature for a high Jc can be lowered by around 100 °C due to the higher packing density of the Ba-122 core prior to the final heat… Show more
“…reported that the smoothness of the interface between the sheath and the core in (Ba,K)Fe 2 As 2 tape is significantly improved by using Ag-Sn binary alloy sheaths [64]. Using proper metal sheath, which is hard and stable against core material, uniform core shape in the wire can also be realized.…”
We report the fabrication of small (Ba,A)Fe 2 As 2 (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 (I c ) of the whole coil using (Ba,Na)Fe 2 As 2 and (Ba,K)Fe 2 As 2 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 (J c ) and I c in (Ba,Na)Fe 2 As 2 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 J c 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 J c .
“…reported that the smoothness of the interface between the sheath and the core in (Ba,K)Fe 2 As 2 tape is significantly improved by using Ag-Sn binary alloy sheaths [64]. Using proper metal sheath, which is hard and stable against core material, uniform core shape in the wire can also be realized.…”
We report the fabrication of small (Ba,A)Fe 2 As 2 (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 (I c ) of the whole coil using (Ba,Na)Fe 2 As 2 and (Ba,K)Fe 2 As 2 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 (J c ) and I c in (Ba,Na)Fe 2 As 2 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 J c 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 J c .
“…It should be noted that the high F values (>0.5) of previous BaK-122 and SrK-122 tapes were achieved using advanced techniques efficient for obtaining the c -axis orientation; (i) application of large uniaxial pressure (~4 GPa, which is 4 times larger than that in this work), (ii) application of hot-press technique, or (iii) use of Ag-Sn alloy sheath or Ag/stainless steel (SS) double sheath (which are harder than the pure Ag sheath used in this work). Thus, the comparison of F values between the BaNa-122 tape and various BaK-/SrK-122 tapes demonstrates that the use of BaNa-122 material is promising for obtaining a better c -axis orientation of the tape core.Figure 5Orientation factor F of BaK-122 11,15,25,30,31 , SrK-122 14,16,32 , and BaNa-122. Several F values were calculated using the XRD patterns given in the references.…”
Section: Discussionmentioning
confidence: 92%
“…Orientation factor F of BaK-122 11,15,25,30,31 , SrK-122 14,16,32 , and BaNa-122. Several F values were calculated using the XRD patterns given in the references.…”
Improvement of the critical current density (Jc) of superconducting wires/tapes is one of the key issues in the field of superconductivity applications. Here we report the fabrication of a silver-sheathed Ba1−xNaxFe2As2 (BaNa-122) superconducting tape by using a powder-in-tube technique and its superconducting properties, in particular transport Jc, as well as the tape-core texture. The optimally-doped BaNa-122 tape with Na concentration x = 0.4 exhibits the superconducting critical temperature (Tc) of 33.7 K and high transport Jc of 4 × 104 A/cm2 at 4.2 K in a magnetic field of 4 T. Patterns of x-ray diffraction for the superconducting core show that the degree of c-axis orientation is significantly enhanced through the tape fabrication process. The tendency of c-axis orientation is advantageous for achieving higher Jc, suggesting the high potential of BaNa-122 for superconducting wire/tape applications.
“…Among all IBSs, 122-type compounds such as (Ba,K)Fe 2 As 2 have the best transport J c [15]. (Ba,K)Fe 2 As 2 (Ba-122), known as a 122-type IBS, has been widely studied because of its great potential for high-field magnet application [16][17][18][19]. For practical purpose, the preparation of wires and tapes is particularly important, and the transport J c is an important indicator of the performance of wires and tapes.…”
Iron-based superconductors (IBSs) have received extensive attention in superconductivity mechanisms and high-field applications based on their ultra-high upper critical fields and low anisotropy. A major goal in the application research of IBSs is the fabrication of superconducting wires and tapes with high critical current density (J c ) and low cost. The use of Cu/Ag composite sheath can reduce the use of expensive silver, thereby reducing the cost of the tapes. In this paper, (Ba,K)Fe 2 As 2 (Ba-122) tapes with Cu/Ag composite sheath were fabricated by a pre-composite process, which provides a feasible method for fabricating high-performance iron-based superconducting wires and tapes. Pre-composite tapes sintered at 750°C for 3 h achieved a high J c of 6.2 × 10 4 A cm −2 at 10 T and 4.2 K. It is found that the high-density superconducting cores, large-size grains and uniform element distribution are the major causes of the high J c . The results suggest that the low-cost Ba-122 tapes with pre-composite Cu/ Ag sheath have great practical application prospect in the future.
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