A2Bi8Se13 (A = Rb, Cs), CsBi3.67Se6, and BaBi2Se4: New ternary semiconducting bismuth selenides

L. Iordanidis, P. W. Brazis, T. Kyratsi, J. Ireland, M. Lane, C. R. Kannewurf, W. Chen, J. S. Dyck, C. Uher, N. A. Ghelani, T. Hogan, M. G. Kanatzidis

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Rb2Bi8Se13 (I), Cs2Bi8Se13 (II), CsBi3.67Se6 (III), and BaBi2Se4 (IV) were synthesized by direct combination reactions of the A/Se (A = Rb, Cs, Ba) and Bi2Se3 at ≥650 °C. Their structures were determined by single-crystal X-ray diffraction. Rb2Bi8Se13 and Cs2Bi8Se13 are isostructural and crystallize in the monoclinic space group P21/m (No. 11) with a = 13.4931(4) Å, b = 4.1558(3) Å, c = 24.876(2) Å, β = 96.571(4)°, R1 = 0.0577, and wR2 = 0.1159 [I > 2σ(I)] for I and a = 13.704(1) Å, b = 4.1532(4) Å, c = 25.008(2) Å, β = 96.848(2)°, R1 = 0.0497, and wR2 = 0.1123 [I > 2σ(I)] for II. CsBi3.67Se6 crystallizes in the orthorhombic space group Pnma (No. 62) with a = 23.421(4) Å, b = 4.1877(8) Å, c = 13.710(3) Å, R1 = 0.0611, and wR2 = 0.1384 [I > 2σ(I)]. BaBi2Se4 crystallizes in the hexagonal space group P63/m (No. 176) with a = 26.157(1) Å, c = 4.3245(3) Å, R1 = 0.0371, and wR2 = 0.0817 [I > 2σ(I)]. The structure of A2Bi8Se13 features a three-dimensional framework consisting of wide rectangular NaCl-type infinite rods, running parallel to the b-axis, which are stitched together by CdI2- and Sb2Se3-type fragments. The NaCl-type blocks are aligned parallel to each other, and between them are rows of alkali metal ions. CsBi3.67Se6 consists of narrower NaCl-type infinite rods, which share edges. The cesium metal ions reside in the space between these rods. The bismuth sites that connect the NaCl-type rods are partially occupied. The [Bi2Se4]2- framework in BaBi2Se4 contains tunnels running along the c-axis that are occupied by Ba atoms. All compounds are narrow band-gap semiconductors. Electrical conductivity and thermoelectric power measurements show that I-IV exhibit n-type charge transport. Compounds I and II, however, can also exhibit p-type behavior. The thermal conductivity for I and IV is low with room-temperature values of ∼1.6 W/(m·K) for I and ∼1.2 W/(m·K) for IV. The optical band gaps of all compounds range between 0.3 and 0.6 eV.

Original languageEnglish
Pages (from-to)622-633
Number of pages12
JournalChemistry of Materials
Issue number2
Publication statusPublished - 2001

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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