WB5-3

Synthesis of K-doped Ba122 polycrystalline bulks with high critical current density

Dec.2 13:35-13:50 (Tokyo Time)

*Shinnosuke Tokuta1,5, Yuta Hasegawa1, Rikuta Fujii1, Yusuke Shimada2,5, Satoshi Hata3,4,5, Akiyasu Yamamoto1,5

Dept. of Applied Physics, Tokyo Univ. of Agricul. and Technol., Koganei, Tokyo 184-8588, Japan1

Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan2

Dept. of Advanced Materials Science, Kyushu University, Kasuga, Fukuoka 816-8580, Japan3

The Ultramicroscopy Research Center, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan4

JST-CREST, Kawaguchi, Saitama 332-0012, Japan5

122 phase iron-based superconductors [1] which have modestly high Tc (~ 38 K), very high Hc2 (~ 100 T), small electromagnetic anisotropy (γ ~ 1-2) [2], and large critical grain boundary angle (θc ~ 9˚) [3] are expected for high field magnet applications. The critical current flowing over a polycrystalline 122 material is often reduced by impurities, voids, and intrinsic weak-link at grain boundaries [3]. Therefore, purification and densification are important for enhancement of Jc. In our previous studies, we found that a ball-milling energy during precursor powder preparation is an important parameter for the ambient pressure synthesis of Co-doped BaFe2As2 (Ba122) bulks [4, 5]. In this study, K-doped Ba122 polycrystalline bulks were synthesized using spark plasma sintering (SPS) apparatus with various sintering conditions. The structural properties, microstructure, and superconducting properties of the K-doped Ba122 bulks were evaluated. Highly pure K-doped Ba122 bulks with high density of more than 90% were successfully synthesized. The highest Jc reached more than 1×105 A/cm2 at 5 K under self-field.

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[3] T. Katase, Y. Ishimaru, A. Tsukamoto, H. Hiramatsu, T. Kamiya et al., Nat. Commun. 2, 409 (2011).
[4] S. Tokuta and A. Yamamoto, APL Mater. 7, 111107 (2019).
[5] S. Tokuta, Y. Shimada, and A. Yamamoto, Supercond. Sci. Technol. 33, 094010 (2020).

Keywords: iron-based superconductor, polycrystalline bulk material, spark plasma sintering