Synthesis, structure, and electronic properties of Cu(2)SiQ(3) (Q = S, Se)

Cu2SiS3 was prepared by the reaction of the constituent binary chalcogenide s and elements at 800 degrees C, and the isotypic selenium compound was syn thesized by using a KCl/LiCl flux at 550 degrees C. Their crystal structure s were determined from single-crystal X-ray data (Cu2SiS3: a=6.332(1), b=11 .230(1), c=6.273(1) Angstrom, beta=107.49(1)degrees, Z=4, R=0.0319 for 2383 reflections and 54 variables. Cu2SiSe3: a=6.669(1), b=11.797(1), c=6.633(1 ) Angstrom, beta=107.67(1)degrees, Z=4, R=0.0279 for 1976 reflections and 5 4 variables). The crystal structure may be described as a monoclinic supers tructure of sphalerite type, in which sulfur atoms form a slightly distorte d cubic close-packed sublattice, and the Cu and Si atoms are located at one -half of the available tetrahedral Voids between the S-layers. The DSC meas urement indicated the incongruent decomposition of Cu2SiSe3 at 632.2 degree s C, and the electrical resistivity measurements confirmed the expected sem iconducting behaviour of both compounds. (C) 1999 Elsevier Science S.A. All rights reserved.