Synthesis and characterization of quaternary selenides Sn(2)Pb(5)Bi(4)Se(13) and Sn(8.65)Pb(0.35)Bi(4)Se(15)

Abstract

Quaternary selenides Sn(2)Pb(5)Bi(4)Se(13) and Sn(8.65)Pb(0.35)Bi(4)Se(15) were synthesized from the elements in sealed silica tubes; their crystal structures were determined by single-crystal and powder X-ray diffraction. Both compounds crystallize in monoclinic space group C2/m (No.12), with lattice parameters of Sn(2)Pb(5)Bi(4)Se(13): a = 14.001(6) angstrom, b = 4.234(2) angstrom, c = 23.471(8) angstrom, V = 1376.2(1) angstrom(3), R(1)/wR(2) = 0.0584/0.1477, and GOF = 1.023; Sn(8.65)Pb(0.35)Bi(4)Se(15): a = 13.872(3) angstrom. b = 4.2021(8) (4) angstrom, c = 26.855(5) angstrom, V = 1557.1(5) angstrom(3), R(1)/wR(2) = 0.0506/0.1227, and GOF = 1.425. These compounds exhibit tropochemical cell-twinning of NaCl-type structures with lillianite homologous series L(4, 5) and L(4, 7) for Sn(2)Pb(5)Bi(4)Se(13) and Sn(8.65)Pb(0.35)Bi(4)Se(15), respectively. Measurements of electrical conductivity indicate that these materials are semiconductors with narrow band gaps; Sn(2)Pb(5)Bi(4)Se(13) is n-type, whereas Sn(8.65)Pb(0.35)Bi(4)Se(15) is a p-type semiconductor with Seebeck coefficients -80(5) and 178(7) mu V/K at 300 K, respectively. (C) 2009 Elsevier Masson SAS. All rights reserved.