Synthesis and characterization of quaternary chalcogenides InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9

Abstract

Quaternary chalcogenides InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9 were synthesized on direct combination of their elements in stoichiometric ratios at T>800 degrees C under vacuum. Their structures were determined with X-ray diffraction of single crystals. InSn2Bi3Se8 crystallizes in monoclinic space group C2/m (No. 12) with a = 13.557(3) angstrom, b = 4.1299(8) angstrom, c = 15.252(3)angstrom, beta = 115.73(3)degrees, V = 769.3(3) angstrom(3), Z = 2, and R-1/wR(2)/GOF = 0.0206/0.0497/1.092; In0.2Sn6Bi1.8Se9 crystallizes in orthorhombic space group Cmc2(1) (No. 36) with a = 4.1810(8) angstrom, b = 13.799(3) angstrom, c = 31.953(6) angstrom, V=1843.4(6) angstrom(3), Z = 4, and R-1/wR(2)/GOF = 0.0966/0.2327/1.12. InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9 are isostructural with CuBi5S8 and Bi2Pb6S9 phases, respectively. The structures of InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9 feature a three-dimensional framework containing slabs of NaCl-(311) type with varied thicknesses. Calculations of the electronic structure and measurements of electrical conductivity indicate that these materials are semiconductors with narrow band gaps. Both compounds show n-type semiconducting properties with Seebeck coefficients -270 and -230 mu V/K at 300 K for InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9, respectively. (C) 2009 Elsevier Inc. All rights reserved.