SYNTHESIS AND CHARACTERIZATION OF ALKALINE-EARTH INDIUM SULFIDES

In the course of studies of the AIn2S4 (A = Ca, Sr, Ba) system, a number of sulfides with metal stoichiometries near, but not necessarily equal to, 1:2 were encountered, including the new phases Ca1.2In1.9S4 and Sr0.9In2.1S4. Indexed X-ray powder diffraction patterns of Ca3.3In6.6S13 (“Ca1.0In2.0S4.0”), Sr0.9In2.1S4, SrIn2S4, and BaIn2S4 are reported. All compounds have been grown as crystals from ACl2-KCl (A = Ca, Sr, Ba) fluxes. Ca3.3In6.5S13 (“Ca1.0In2.0S4.0”) forms in the monoclinic space group C2/m with unit cell parameters a = 37.628 (4), b = 3.8360 (8), c = 13.722 (1) Å, and β = 91.66 (1)°. X-ray powder diffraction data indicate that this compound is isostructural with the previously reported phases Ca3.1In6.6S13 (“Ca1.0In2.0S4.0”), Sn2.5In7S13 (“Sn0.8In2.2S4.0”), and Pb3In6.67S13 (“Pb0.9In2.1S4.0”). These compounds, along with the known phases Sn5.5In11S22 (“Sn1.0In2.0S4.0”), Sn3.5In9S17 (“Sn0.8In2.1S4.0”), and Pb4In9S17 (“Pb0.9In2.1S4.0”), share structural features that consist of stepped “layers” of edge-sharing InS6 octahedra interconnected by vertex-sharing with columns comprised of other InS6 octahedra to form a three-dimensional structure. The divalent cations reside in bicapped trigonal prismatic sites in the channels formed by the In-S framework. Observed X-ray powder diffraction data for crystals of a new compound, Ca1.2In1.9S4, are reported. Another newly prepared phase, Sr0.9In2.1S4, forms with a C-centered monoclinic unit cell, a = 27.66 (1), b = 3.943 (2), c = 12.683 (7) Å, and β = 94.25 (4)°. The poor crystallinity of these phases has precluded single-crystal X-ray structure determinations. Indexed powder diffraction data are also given for the previously reported orthorhombic forms of SrIn2S4 and BaIn2S4. Although the empirical formulas are similar, the structures of these two latter compounds are unrelated to those of the other ternary indium sulfides mentioned above and feature tetrahedrally coordinated indium. © 1990, American Chemical Society. All rights reserved.