Synthesis and phase width of new quaternary selenides Pb(x)Sn(6-x)Bi(2)Se(9) (x=0-4.36)

Abstract

Quaternary chalcogenides Pb(x)Sn(6-x)Bi(2)Se(9) (x=0-4.36) were synthesized with solid-state methods; their structures were determined from the X-ray diffraction of single crystals. Pb(x)Sn(6-x)Bi(2)Se(9) crystallizes in an orthorhombic space group Cmcm (No. 63); the structure features a three-dimensional framework containing slabs of NaCl-(3 1 1) type that exhibits identical layers containing seven octahedra units, which expand along the direction [0 1 0]. Each slab contains fused rectangular units that are connected to each other with M-Se contacts in a distorted octahedral environment. Calculations of the band structure, measurements of Seebeck coefficient and electrical conductivity confirm that these compounds are n-type semiconductors with small band gaps and large electrical conductivities. (C) 2010 Elsevier Inc. All rights reserved.