The Beijing Municipal Key Laboratory of New Energy Materials and Technologies, School of Materials Sciences and Engineering , University of Science and Technology Beijing , Beijing 100083 , China.
Department of Chemistry, Physics and Atmospheric Sciences , Jackson State University , Jackson , Mississippi 39217 , United States.
Inorg Chem. 2018 Aug 6;57(15):9403-9411. doi: 10.1021/acs.inorgchem.8b01383. Epub 2018 Jul 16.
Two new layered compounds RbZnBiSe and CsCdBiTe are described. RbZnBiSe crystallizes in the orthorhombic space group Pnma, with lattice parameters of a = 15.6509(17) Å, b = 4.218(8) Å, and c = 18.653(3) Å. CsCdBiTe crystallizes in the monoclinic C2/ m space group, with a = 28.646(6) Å, b = 4.4634(9) Å, c = 21.164(4) Å, and β = 107.65(3)°. The two structures are different and composed of anionic layers which are formed by inter connecting of BiQ octahedra (Q = Se or Te) and MQ (M = Zn or Cd) tetrahedra. The space between the layers hosts alkali metal as counter cations. The rubidium atoms of RbZnBiSe structure can be exchanged with other cations (Cd, Pb and Zn) in aqueous solutions forming new phases. RbZnBiSe is an n-type semiconductor and exhibits an indirect band gap energy of 1.0 eV. RbZnBiSe is a congruently melting compound (mp ∼644 °C). The thermal conductivity of this semiconductor is very low with 0.38 W·m·K at 873 K. Density functional theory (DFT) calculations suggest that the low lattice thermal conductivity of RbZnBiSe is attributed to heavy Bi atom induced slow phonon velocities and large Gruneisen parameters especially in the a and c directions. The thermoelectric properties of RbZnBiSe were characterized with the highest ZT value of ∼0.25 at 839 K.
描述了两种新型层状化合物 RbZnBiSe 和 CsCdBiTe。RbZnBiSe 属于正交晶系 Pnma 空间群，晶格参数为 a = 15.6509(17) Å，b = 4.218(8) Å，c = 18.653(3) Å。CsCdBiTe 属于单斜晶系 C2/ m 空间群，晶格参数为 a = 28.646(6) Å，b = 4.4634(9) Å，c = 21.164(4) Å，β = 107.65(3)°。这两种结构不同，都是由 BiQ 八面体（Q = Se 或 Te）和 MQ（M = Zn 或 Cd）四面体相互连接形成的阴离子层组成。层之间的空间容纳了作为抗衡阳离子的碱金属。RbZnBiSe 结构中的铷原子可以在水溶液中与其他阳离子（Cd、Pb 和 Zn）交换，形成新的相。RbZnBiSe 是一种 n 型半导体，具有 1.0 eV 的间接带隙能。RbZnBiSe 是一种完全熔融的化合物（mp ∼644°C）。该半导体的热导率非常低，在 873 K 时为 0.38 W·m·K。密度泛函理论（DFT）计算表明，RbZnBiSe 晶格热导率低是由于 Bi 原子较重导致声子速度缓慢以及在 a 和 c 方向上的 Grüneisen 参数较大。RbZnBiSe 的热电性能特征为在 839 K 时具有约 0.25 的最高 ZT 值。
