Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Inorg Chem. 2013 Jun 17;52(12):7210-7. doi: 10.1021/ic4008284. Epub 2013 Jun 3.
Mixed S(2-/)S(1-) oxidation states have been discovered in the new quaternary compound NaBa2Cu3S5. Synthesized from the reaction of Cu in a molten alkali metal/polysulfide flux, the compound crystallizes in monoclinic space group C2/m with a = 16.5363(7) Å, b = 5.5374(5) Å, c = 10.3717(10) Å, β = 98.535(8)°. The Na(+) Ba2(+2) Cu(+)3S3S2(2-) crystal structure contains layers of edge sharing CuS4 tetrahedra and sheets of S2(2-) dimers. These layers are separated by mixed Ba/Na cation layers. The conductivity of the single crystals of NaBa2Cu3S5 is ∼450 S cm(-1) at room temperature, and increasing conductivity with decreasing temperature is observed, indicating metallic behavior despite the optical band gap of 0.45 eV. A small positive thermopower (45-55 μV K(-1) from 300 K to 500 K) and Hall effect measurements also confirm p-type conductivity with carrier concentration at 200 K of ∼1.6 × 10(21) cm(-3) and a hole mobility of ∼2 cm(2) V(-1) s(-1). NaBa2Cu3S5 exhibits temperature-independent Pauli paramagnetism.
新的四元化合物 NaBa2Cu3S5 中发现了混合的 S(2-/)S(1-)氧化态。该化合物是通过 Cu 在熔融碱金属/多硫化物熔体中的反应合成的，结晶于单斜空间群 C2/m，a = 16.5363(7) Å，b = 5.5374(5) Å，c = 10.3717(10) Å，β = 98.535(8)°。Na(+) Ba2(+2) Cu(+)3S3S2(2-)晶体结构包含边缘共享的 CuS4 四面体层和 S2(2-)二聚体层。这些层由混合的 Ba/Na 阳离子层隔开。NaBa2Cu3S5 单晶的室温电导率约为 450 S cm(-1)，且随着温度降低电导率增大，表明尽管存在 0.45 eV 的光学带隙，但具有金属行为。较小的正热电势（300 K 至 500 K 时为 45-55 μV K(-1)）和 Hall 效应测量也证实了 p 型导电性，在 200 K 时载流子浓度约为 1.6 × 10(21) cm(-3)，空穴迁移率约为 2 cm(2) V(-1) s(-1)。NaBa2Cu3S5 表现出温度无关的 Pauli 顺磁性质。
