WB5-1-INV

Recent progress on the development of K-doped Ba122 bulk superconductors

Dec.2 13:00-13:20 (Tokyo Time)

*Akiyasu Yamamoto1,2,8, Shinnosuke Tokuta1,8, Yuta Hasegawa1, Rikuta Fujii1, Yuki Okada1, Yusuke Shimada3,8, Hikaru Saito4,8, Satoshi Hata4,5,8, Akimitsu Ishii6,8, Akinori Yamanaka6,8, Kazumasa Iida7,8

Dept. of Applied Physics, Tokyo Univ. of Agricul. and Technol.1

Materials Research Center for Element Strategy, Tokyo Institute of Technology2

Institute for Materials Research, Tohoku University3

Dept. of Advanced Materials Science, Kyushu University4

The Ultramicroscopy Research Center, Kyushu University5

Dept. of Mechanical System Engineering, Tokyo Univ. of Agricul. and Technol.6

Dept. of Materials Physics, Nagoya University7

JST-CREST8

Iron-based superconductors (IBSCs) with high Tc of ~60 K in 1111 and ~40 K in 122 are interesting for cryocooled high field applications, owing to their high Hc2 with small anisotropy nearly ~1 (in 122) [1,2]. The unique advantage which distinguishes IBSCs from cuprates is high critical misorientation angle of 9 degrees [3]. Thus high critical current over a sample is expected in randomly oriented, polycrystalline form, which leads to low-cost and scalable production. In our previous studies, we found that sintering mechanically alloyed precursor powder is an effective process to produce Ba122 polycrystalline bulks with high phase purity [4,5]. In the present work, we report (1) the effects of spark plasma sintering on the microstructure and superconducting properties of K doped 122 polycrystalline bulks and (2) Bayesian engineered high critical current density in K doped Ba122 polycrystalline bulks. This work was supported by JST CREST (JPMJCR18J4), JSPS KAKENHI (JP18H01699) and Nanotechnology Platform (A-18-TU-0037) of the MEXT, Japan.

[1] Y. Kamihara et al., J. Am. Chem. Soc. 130(11), 3296-3297 (2008).
[2] H. Hosono et al., Mater. Today 21, 278-302 (2018).
[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 bulks