Structural Difference in Superconductive and Nonsuperconductive Bi鈥揝 Planes within Bi4O4Bi2S4 Blocks

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• 作者：Akira Miura ; Yoshikazu Mizuguchi ; Tsuyoshi Sugawara ; Yongming Wang ; Takahiro Takei ; Nobuhiro Kumada ; Eisuke Magome ; Chikako Moriyoshi ; Yoshihiro Kuroiwa ; Osuke Miura ; Kiyoharu Tadanaga
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：November 2, 2015
• 年：2015
• 卷：54
• 期：21
• 页码：10462-10467
• 全文大小：407K
• ISSN：1520-510X

文摘

The relationship between the structure and superconductivity of Bi₄O₄S₃ powders synthesized by heating under ambient and high pressures was investigated using synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM) observation. The Bi₄O₄S₃ powders synthesized under ambient pressure exhibited a strong superconductivity (diamagnetic) signal and zero resistivity below 鈭?.5 K, while the Bi₄O₄S₃ powder synthesized by the high-pressure method exhibited a low-intensity signal down to 2 K. Further annealing of the latter Bi₄O₄S₃ powder under ambient pressure led to the development of a strong signal and zero resistivity. The crystal structures of all Bi₄O₄S₃ phases consisted of Bi₄O₄Bi₂S₄ blocks including a Bi鈥揝 layer and anion(s) sandwiched between Bi₄O₄Bi₂S₄ blocks, but minor structural differences were detected. A comparison of the structures of the superconductive and nonsuperconductive Bi₄O₄S₃ samples suggested that the superconductive Bi₄O₄S₃ phases had slightly smaller lattice parameters. The average structures of the superconductive Bi₄O₄S₃ phases were characterized by a slightly shorter and less bent Bi鈥揝 plane. Raman spectroscopy detected vibration of the S鈥揙 bonds, which can be attributed to sandwiched anion(s) such as SO₄^{2鈥?/sup>. TEM observation showed stacking faults in the superconductive Bi₄O₄S₃ phases, which indicated local fluctuation of the average structures. The observed superconductivity of Bi₄O₄S₃ was discussed based on impurity phases, enhanced hybridization of the p_x and p_y orbitals of the Bi鈥揝 plane within Bi₄O₄Bi₂S₄ blocks, local fluctuation of the average structures, compositional deviation related to suspicious anion(s) sandwiched between Bi₄O₄Bi₂S₄ blocks, and the possibility of suppression of the charge-density-wave state by enriched carrier concentrations.}