Synthesis and Phase Width of Quaternary Selenides Pb(4)In(x)M(6-x)Se(13) (M = Bi, x=2.1-2.8; Sb, x=2)

Abstract

Quaternary selenides of Pb(4)In(x)M(6-x)Se(13) (M = Bi, x = 2.1-2.8; Sb, x = 2) were synthesized by solid-state methods, and their structures were determined from X-ray diffraction of single crystals. These compounds are isostructural with Pb(4)In(2)Bi(4)S(13) and crystallize in orthorhombic space group Pbam (No. 55) with Z = 4; the structure features a three-dimensional framework consisting of Z-shaped ribbon units and corner-sharing infinite one-dimensional [InSe(4)](proportional to) chains running parallel to the c-axis, which are connected by Pb atoms to form a three-dimensional structure. Calculations of the band structure and measurements of Seebeck coefficient, electrical conductivity, and diffuse reflectance spectra confirm that these compounds are semiconductors with a narrow band gap. All compounds show semiconducting properties; the Seebeck coefficient of Pb(4)In(2.5)Bi(3.5)Se(13) is -180 mu V/K at 295 K.