Syntheses, Crystal Structures, and Physical Properties of La5Cu6O4S7 and La5Cu6.33O4S7

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• 作者：George H. Chan ; Ming-Ling Liu ; Li-Dong Chen ; Fu-Qiang Huang ; Daniel E. Bugaris ; Daniel M. Wells ; John R. Ireland ; Mark C. Hersam ; Richard P. Van Duyne ; James A. Ibers
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：May 19, 2008
• 年：2008
• 卷：47
• 期：10
• 页码：4368 - 4374
• 全文大小：1613K
• 年卷期：v.47,no.10(May 19, 2008)
• ISSN：1520-510X

文摘

Single crystal and bulk powder samples of the quaternary lanthanum copper oxysulfides La₅Cu_6.33O₄S₇ and La₅Cu₆O₄S₇ have been prepared by means of high-temperature sealed-tube reactions and spark plasma sintering, respectively. In the structure of La₅Cu_6.33O₄S₇, Cu atoms tie together the fluorite-like ²_∞[La₅O₄S⁵⁺] and antifluorite-like ²_∞[Cu₆S₆⁵⁻] layers of La₅Cu₆O₄S₇. The optical band gap, E_g, of 2.0 eV was deduced from both diffuse reflectance spectra on a bulk sample of La₅Cu₆O₄S₇ and for the (010) crystal face of a La₅Cu_6.33O₄S₇ single crystal. Transport measurements at 298 K on a bulk sample of La₅Cu₆O₄S₇ indicated p-type metallic electrical conduction with σ_electrical = 2.18 S cm⁻¹, whereas measurements on a La₅Cu_6.33O₄S₇ single crystal led to σ_electrical = 4.5 10⁻³ S cm⁻¹ along [100] and to semiconducting behavior. In going from La₅Cu₆O₄S₇ to La₅Cu_6.33O₄S₇, the disruption of the ²_∞[Cu₆S₆⁵⁻] layer and the decrease in the overall Cu²⁺ (3d⁹) concentration lead to a significant decrease in the electrical conductivity.