Hydrothermal Synthesis, Structure, and Superconductivity of Simple Cubic Perovskite (Ba0.62K0.38)(Bi0.92Mg0.08)O3 with Tc ∼ 30 K

Mirza H K Rubel; Takahiro Takei; Nobuhiro Kumada; M Mozahar Ali; Akira Miura; Kiyoharu Tadanaga; Kengo Oka; Masaki Azuma; Eisuke Magome; Chikako Moriyoshi; Yoshihiro Kuroiwa

doi:10.1021/acs.inorgchem.6b01853

Hydrothermal Synthesis, Structure, and Superconductivity of Simple Cubic Perovskite (Ba_0.62K_0.38)(Bi_0.92Mg_0.08)O₃ with T_c ∼ 30 K

Inorg Chem. 2017 Mar 20;56(6):3174-3181. doi: 10.1021/acs.inorgchem.6b01853. Epub 2017 Feb 24.

Authors

Affiliations

¹ Department of Materials Science and Engineering, University of Rajshahi , Rajshahi 6205, Bangladesh.
² Center for Crystal Science and Technology, University of Yamanashi , 7-32 Miyamae-cho, Kofu 400-8511, Japan.
³ Faculty of Engineering, Hokkaido University , Kita 13, Nishi 8, Kita-ku, Sapporo 060-8628, Japan.
⁴ Faculty of Science, Chuo University , 112-8551, 1-13-27, Kasuga, Bunkyo-ku, Tokyo 192-0393, Japan.
⁵ Laboratory for Materials and Structures, Tokyo Institute of Technology , 4259 Nagatsuta, Kanagawa 226-8503, Japan.
⁶ Department of Physical Science, Hiroshima University , 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan.

PMID: 28233995
DOI: 10.1021/acs.inorgchem.6b01853

Abstract

We have synthesized a new superconducting perovskite bismuth oxide by a facile hydrothermal route at 220 °C. The choice of starting materials, their mixing ratios, and the hydrothermal reaction temperature was crucial for obtaining products with superior superconducting properties. The structure of the powder sample was investigated using laboratory X-ray diffraction, high-resolution synchrotron X-ray diffraction (SXRD) data, and electron diffraction (ED) patterns [transmission electron microscopy (TEM) analysis]. The refinement of SXRD data confirmed a simple perovskite-type structure with a cubic cell of a = 4.27864(2) Å [space group Pm3̅m (No. 221)]. Elemental analysis detected magnesium in the final products, and a refinement based on SXRD and inductively coupled plasma data yielded an ideal undistorted simple cubic perovskite-type structure, with the chemical composition (Ba_0.62K_0.38)(Bi_0.92Mg_0.08)O₃. ED patterns also confirmed the simple cubic perovskite structure; the cube-shaped microstructures and compositional homogeneity on the nanoscale were verified by scanning electron microscopy and TEM analyses, respectively. The fabricated compound exhibited a large shielding volume fraction of about 98% with a maximum T_c^mag of ∼30 K, which was supported by the measured bismuth valence as well. Its electrical resistivity dropped at ∼21 K, and zero resistivity was observed below 7 K. The compound underwent thermal decomposition above 400 °C. Finally, the calculated band structure showed a metallic behavior for this hydrothermally synthesized bismuth oxide.