Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl: Syntheses, crystal structures and optical properties

摘要

Four new chalcohalides, namely NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl, have been synthesized by the conventional high temperature solid-state reactions. They crystallize in three different space groups: space group I4/mcm for NaBa2SnS4Cl and KBa2SnS4Cl, Pnma for KBa2SnS4Br, and P2(1)/c for CsBa2SnS4Cl. In all four compounds, the X- halide anions are only connected to six alkali metal or Ba cations, and the Sn atoms are only tetrahedrally enjoined to four S atoms. However, the M-X-Ba pseudo layers and the SnS4 tetrahedra are arranged in different ways in the three structural types, which demonstrates the interesting effect of ionic radii on the crystal structures. UV-vis-NIR spectroscopy measurements indicate that NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl have band gaps of 2.28, 2.30, 1.95, and 2.06 eV, respectively. (C) 2015 Elsevier Inc. All rights reserved.