Syntheses, crystal structures, and physical properties of La5Cu6O4S7 and La5Cu6.33O4S7
Syntheses, crystal structures, and physical properties of La5Cu6O4S7 and La5Cu6.33O4S7
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DOI：
10.1021/ic7024796
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发表时间：
2008-05-19
影响因子：
4.6
通讯作者：
Ibers, James A.
中科院分区：
文献类型：
--
作者：
Chan, George H.;Liu, Ming-Ling;Ibers, James A.
Single crystal and bulk powder samples of the quaternary lanthanum copper oxysulfides La5Cu6.33O4S7 and La5Cu6O4S7 have been prepared by means of high-temperature sealed-tube reactions and spark plasma sintering, respectively. In the structure of La5Cu6.33O4S7, Cu atoms tie together the fluorite-like (2)(infinity)[La5O4S5+] and antifluorite-like (2)(infinity)[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 La5Cu6.33O4S7 single crystal. Transport measurements at 298 K on a bulk sample of La5Cu6O4S7 indicated p-type metallic electrical conduction with sigma(electrical) = 2.18 S cm(-1), whereas measurements on a La5Cu6.33O4S7 single crystal led to sigma(electrical) = 4.5 10(-3) S cm(-1) along [100] and to semiconducting behavior. In going from La5Cu6O4S7 to La5Cu6.33O4S7, the disruption of the (2)(infinity)[Cu6S65-] layer and the decrease in the overall Cu2+ (3d(9)) concentration lead to a significant decrease in the electrical conductivity.
