Abstract Body

The 122-type iron-based superconductors (IBSs) [1] show a higher superconducting transition temperature (T_c) and upper critical field (H_c2) than commercially used superconductors such as NbTi and Nb₃Sn. The superconducting wires and tapes of 122-type IBSs are fabricated using the powder-in-tube (PIT) method, which is beneficial for reducing production costs. Therefore, 122-type IBSs are expected to be used in superconducting wires and tapes for superconducting magnets that generate magnetic fields in liquid He or H₂. The widely accepted threshold for transport critical current density (J_c) in superconducting wires and tapes for practical use is 100 kA/cm² under 100 kOe and at 4.2 K [2]. The record-high transport J_c value for IBS round wires under these conditions is 71 kA/cm² in the (Ba,Na)Fe₂As₂ round wire [3]. The highest transport J_c value under the same conditions for the (Ba,K)Fe₂As₂ round wires is 49 kA/cm² [4]. Meanwhile, the highest transport J_c value for IBS tapes under the same conditions reached 150 kA/cm² in the (Ba,K)Fe₂As₂ tape [5]. The highest value of transport J_c (100 kOe, 4.2 K) for the (Ba,Na)Fe₂As₂ round wires is 44 kA/cm² [6] where there is room for improvements. In this study, we fabricated Ag-sheathed (Ba,Na)Fe₂As₂ tapes by the PIT method, incorporating cold pressing. Figure 1 shows the X-ray diffraction (XRD) pattern of the tape. We assessed c-axis texturing by measuring the texturing parameter (r = I(002) / I(103)) in the XRD pattern. The r value is ~1.2, which is relatively high for (Ba,Na)Fe₂As₂ tapes. We will discuss the fabrication process and measurement results for the transport properties. We will also report the results on (Ba,Na)Fe₂As₂ tapes using harder sheath materials such as Ag-Sn alloy.

References

[1] M. Rotter et al., Phys. Rev. B 101, 107006 (2008).
[2] H. Hosono et al., Mater. Today 21, 278 (2018).
[3] S. Pyon et al., Physica C 613, 1354354 (2023).
[4] S. Pyon et al., J. Phys. Conf. Ser. 2323, 012020 (2022).
[5] H. Huang et al., Supercond. Sci. Technol. 31, 015017 (2018).
[6] T. Tamegai et al., IEEE Trans. Appl. Supercon. 31, 7300505 (2021).

Figure 1. X-ray diffraction (XRD) pattern for Ag-sheathed (Ba,Na)Fe₂As₂ tape with Bragg-Brentano geometry. The longitudinal direction of the tape was set parallel to the X-ray. We subtracted the background.

Keywords: iron-based superconductor, superconducting tapes, X-ray computed tomography