Na3SbS3: Single Crystal X-ray Diffraction, Raman Spectroscopy, and Impedance Measurements

Na3SbS3 was prepared by the reaction of anhydrous Na2S, antimony, and sulfur in a ratio of 3:2:3 at 870 K. The pale yellow compound is air and moisture sensitive. A microcrystalline sample was obtained after annealing Na3SbS3 for two weeks at 720 K. The crystal structure of Na3SbS3 was determined by single-crystal X-ray diffraction at 123 K. Na3SbS3 crystallizes in the cubic space group P213 (No. 198) with a = 8.6420(1) Å, V = 645.42(1) Å3 and Z = 4. The structure refinement converged to R = 0.0099 (wR = 0.0181) for 592 independent reflections and 23 parameters. Na3SbS3 is isotypic with Na3AsS3. Sodium atoms are located on three different sites, which show a strongly distorted octahedral coordination sphere of sulfur. The coordination polyhedra of equivalent sodium sites share common vertices, whereas those of different sodium sites share common faces. Antimony and sulfur form trigonal SbS3 pyramids, which coordinate sodium as a mono-, bi-, or tridentate ligand. Raman spectroscopic investigations result in stretching modes ν(Sb–S) at 334, 321, and 312 cm–1, respectively. Thermoanalytical studies do not show any additional thermal effects up to the melting point of 875 K. Impedance spectroscopy on Na3SbS3 in a range from 325 to 570 K shows a temperature dependent Na+ conductivity, which is 1.9 × 10–6 Ω–1·cm–1 at 570 K