Barium tantalum sulfide, BaTaS3, has been prepared and single crystals have been grown from a barium chloride flux. The crystal structure of BaTaS3 has been refined by single-crystal analysis and the space group is P63/mmc with two formula units per unit cell. The hexagonal cell dimensions are a = 6.846 ± 0.005 and c = 5.744 ± 0.005 Å. The calculated density is 5.91 g/cm3 and the observed density is 5.80 g/cm3. The structure was refined with the use of anisotropic temperature factors to a final R factor on F of 0.087 for 186 independent reflections above background. BaTaS3 was found to be isostructural with BaVS3 and CsNiCl3. The structure is based on the hexagonal close packing of BaS3 layers and consists of infinite chains along the c axis formed by face-shared octahedra; the Ta cations occupy all the S6 octahedra and are spaced midway between the close-packed layers. Low-temperature X-ray studies show that there are no temperature-dependent crystallographic transitions between 77 and 298°K. Pressed and sintered bars of polycrystalline BaTaS3 indicate semiconductor behavior with an activation energy of 0.01-0.06 eV. This behavior is attributed to a distortion of the hexagonal structure as a result of the pressure used in preparing the bar. The electrical properties are discussed in terms of direct interactions between the tantalum cations in adjoining octahedra. © 1969, American Chemical Society. All rights reserved.
