Chan George H, Liu Ming-Ling, Chen Li-Dong, Huang Fu-Qiang, Bugaris Daniel E, Wells Daniel M, Ireland John R, Hersam Mark C, Van Duyne Richard P, Ibers James A
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
Inorg Chem. 2008 May 19;47(10):4368-74. doi: 10.1021/ic7024796. Epub 2008 Apr 23.
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 La 5Cu6.33O4S7, Cu atoms tie together the fluorite-like (2)infinity[La5O4S(5+)] and antifluorite-like (2) infinity[Cu6S6(5-)] 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 La 5Cu6.33O4S7 single crystal. Transport measurements at 298 K on a bulk sample of La 5Cu 6O 4S 7 indicated p-type metallic electrical conduction with sigma electrical =2.18 S cm(-1), whereas measurements on a La 5Cu6.33O4S7 single crystal led to sigma electrical =4.5 10(-3) S cm(-1) along [100] and to semiconducting behavior. In going from La 5Cu6O4S7 to La5Cu6.33O4S7, the disruption of the (2)infinity[Cu6S6(5-)] layer and the decrease in the overall Cu(2+)(3d(9)) concentration lead to a significant decrease in the electrical conductivity.
通过高温密封管反应和放电等离子烧结分别制备了四元镧铜氧硫化物La5Cu6.33O4S7和La5Cu6O4S7的单晶及块状粉末样品。在La5Cu6.33O4S7的结构中，铜原子将La5Cu6O4S7的类萤石型(2)∞[La5O4S(5 +)]层和类反萤石型(2)∞[Cu6S6(5 -)]层连接在一起。通过对La5Cu6O4S7块状样品的漫反射光谱以及La5Cu6.33O4S7单晶的(010)晶面的漫反射光谱推导得出，其光学带隙Eg为2.0 eV。在298 K下对La5Cu6O4S7块状样品进行的输运测量表明其具有p型金属导电性，电导率σelectrical = 2.18 S cm-1，而对La5Cu6.33O4S7单晶的测量结果显示，沿[100]方向的电导率σelectrical = 4.5×10-3 S cm-1，呈现半导体行为。从La5Cu6O4S7转变为La5Cu6.33O4S7时，(2)∞[Cu6S6(5 -)]层的破坏以及整体Cu(2 +)(3d9)浓度的降低导致电导率显著下降。
