Rubel Mirza H K, Takei Takahiro, Kumada Nobuhiro, Ali M Mozahar, Miura Akira, Tadanaga Kiyoharu, Oka Kengo, Azuma Masaki, Magome Eisuke, Moriyoshi Chikako, Kuroiwa Yoshihiro
Department of Materials Science and Engineering, University of Rajshahi , Rajshahi 6205, Bangladesh.
Center for Crystal Science and Technology, University of Yamanashi , 7-32 Miyamae-cho, Kofu 400-8511, Japan.
Inorg Chem. 2017 Mar 20;56(6):3174-3181. doi: 10.1021/acs.inorgchem.6b01853. Epub 2017 Feb 24.
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 (BaK)(BiMg)O. 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 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.
我们通过在220°C的简易水热法合成了一种新型超导钙钛矿铋氧化物。起始原料的选择、它们的混合比例以及水热反应温度对于获得具有优异超导性能的产物至关重要。使用实验室X射线衍射、高分辨率同步加速器X射线衍射（SXRD）数据和电子衍射（ED）图案[透射电子显微镜（TEM）分析]对粉末样品的结构进行了研究。SXRD数据的精修证实了一种简单的钙钛矿型结构，其立方晶胞参数a = 4.27864(2) Å [空间群Pm3̅m (No. 221)]。元素分析在最终产物中检测到了镁，基于SXRD和电感耦合等离子体数据的精修得到了理想的无畸变简单立方钙钛矿型结构，其化学组成为(BaK)(BiMg)O。ED图案也证实了简单立方钙钛矿结构；通过扫描电子显微镜和TEM分析分别验证了纳米级的立方体形微观结构和成分均匀性。制备的化合物表现出约98%的大屏蔽体积分数，最大转变温度T约为30 K，这也得到了所测铋价态的支持。其电阻率在约21 K时下降，在7 K以下观察到零电阻率。该化合物在400°C以上发生热分解。最后，计算得到的能带结构表明这种水热合成的铋氧化物具有金属行为。
