Synthesis and characterization of a new quaternary selenide Sr(3)GeSb(2)Se(8)

A new quaternary selenide Sr(3)GeSb(2)Se(8) has been synthesized at 750 degrees C from pure elements in a stoichiometric ratio under vacuum. The product as-synthesized is characterized by single-crystal X-ray diffraction, diffuse reflectance spectroscopy, and thermoanalysis. The title compound crystallizes in the orthorhombic space group Pnma with a = 12.633(4) angstrom, b = 4.301(1) angstrom, c = 28.693(7) angstrom, V = 1558.8(8) angstrom(3), Z = 4, R(1)/wR(2) = 0.0582/0.1221, and GOF = 1.077. The structure of Sr(3)GeSb(2)Se(8) features a new structural type that consists of one-dimensional chains of vertex-sharing tetrahedra (1)(infinity)[MSe(3)] (M = Ge/Sb) and fused double chains of edge-shared square pyramids (1)(infinity)[M(2)Se(5)], which are held together by Sr(2+) ions. A band gap of 0.75 eV for Sr(3)GeSb(2)Se(8) was derived from its diffuse reflectance spectrum. (C) 2007 Elsevier Masson SAS. All rights reserved.