Highly c-axis orientated superconducting core and large critical current density in Ba0.6Na0.4Fe2As2 powder-in-tube tape

S Imai,K Matsuzaki,Y Yoshida,H Eisaki,S Ishida,Y Tsuchiya,T Nishio,A Iyo,S Itou

doi:10.1038/s41598-019-49363-y

Abstract

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.

Highlights

Polycrystalline powders of BaNa-122 were synthesized by a solid-state reaction
BaAs, NaAs, and Fe2As powders were prepared as precursors by mixing elemental Ba, Na, Fe, and As chunks at stoichiometric molar ratio, sealing them into quartz tubes (BaAs and Fe2As) or stainless-steel container (NaAs), and heating at 650 °C (BaAs and NaAs) and 750 °C (Fe2As)
The polycrystalline powders were pressed into a pellet by applying a pressure of about 100 MPa

Summary

Methods

BaAs, NaAs, and Fe2As powders were prepared as precursors by mixing elemental Ba, Na, Fe, and As chunks at stoichiometric molar ratio, sealing them into quartz tubes (BaAs and Fe2As) or stainless-steel container (NaAs), and heating at 650 °C (BaAs and NaAs) and 750 °C (Fe2As). The mixed powders were put in an alumina crucible and sealed in a stainless-steel container, sintered at 770 °C for 15 hours. The silver tube was groove-rolled into a square wire with the 1.2 × 1.2 mm[2] cross-sectional and subsequently flat-rolled into a tape with a thickness of 0.48 mm. The thin tape was cut into 50 mm long pieces, sealed into a stainless-steel container in a N2-filled glove box, and sintered at 875 °C for 3 h

Results

Discussion

Conclusion