Flux Growth and Superconducting Properties of (Ce,Pr)OBiS2 Single Crystals

Masanori Nagao; Akira Miura; Daisuke Urushihara; Yuki Maruyama; Yosuke Goto; Yoshikazu Mizuguchi; Chikako Moriyoshi; Yoshihiro Kuroiwa; Yongming Wang; Satoshi Watauchi; Toru Asaka; Yoshihiko Takano; Kiyoharu Tadanaga; Isao Tanaka

doi:10.3389/fchem.2020.00044

Flux Growth and Superconducting Properties of (Ce,Pr)OBiS₂ Single Crystals

Front Chem. 2020 Feb 4:8:44. doi: 10.3389/fchem.2020.00044. eCollection 2020.

Authors

Affiliations

¹ Center for Crystal Science and Technology, University of Yamanashi, Kofu, Japan.
² Faculty of Engineering, Hokkaido University, Sapporo, Japan.
³ Division of Advanced Ceramics, Nagoya Institute of Technology, Nagoya, Japan.
⁴ Department of Physics, Tokyo Metropolitan University, Hachioji, Japan.
⁵ Department of Physical Science, Hiroshima University, Hiroshima, Japan.
⁶ Creative Research Institution, Hokkaido University, Sapporo, Japan.
⁷ MANA, National Institute for Materials Science, Tsukuba, Japan.

Abstract

Ce_1-x Pr _x OBiS₂ (0. 1 ≤ x ≤ 0.9) single crystals were grown using a CsCl flux method. Their structural and physical properties were examined by X-ray diffraction, X-ray absorption, transmission electron microscopy, and electrical resistivity. All of the Ce_1-x Pr _x OBiS₂ single crystals with 0.1 ≤ x ≤ 0.9 exhibited tetragonal phase. With increasing Pr content, the a-axis and c-axis lattice parameters decreased and increased, respectively. Transmission electron microscope analysis of Ce_0.1Pr_0.9OBiS₂ (x = 0.9) single crystal showed no stacking faults. Atomic-resolution energy dispersive X-ray spectrometry mapping revealed that Bi, Ce/Pr, O, and S occupied different crystallographic sites, while Ce and Pr randomly occupied the same sites. X-ray absorption spectra showed that an increase of the Pr ratio increased the ratio of Ce⁴⁺/Ce³⁺. All of the Ce_1-x Pr _x OBiS₂ crystals showed superconducting transition, with a maximum transition temperature of ~4 K at x = 0.9.

Keywords: BiS2 superconductor; TEM; XAFS; flux growth; single crystals.