SYNTHESIS AND CHARACTERIZATION OF THE NEW RARE-EARTH TRANSITION-METAL OXYSULFIDES LA6TI2S8O5 AND LA4TI3S4O8

The new compounds La6Ti2S8O5 and La4Ti3S4O8 have been prepared from the reaction of La2S3 with TiO2. Both phases are highly resistive and weakly paramagnetic. Single-crystal X-ray diffraction measurements show that La6Ti2S8O5 crystallizes in space group C-2h(2)-P2(1)/m of the monoclinic system with two formula units in a cell of dimensions a = 12.572(10), b = 4.053(2), c = 16.289(14) Angstrom, beta = 96.79(1)degrees (T = 113 K). The structure contains six crystallographically independent La atoms with four different coordination geometries, and Ti atoms in octahedral coordination. The Ti octahedra form an infinite, corner-sharing dimeric chain in the b direction. La4Ti3S4O8 crystallizes in the monoclinic space group C-2h(3)-C2/m with four formula units in a cell with dimensions a = 18.363(9), b = 3.886(2), c = 17.911(9) Angstrom, beta = 109.83(2)degrees (T = 113 K). The structure is composed of La atoms in tricapped trigonal prisms and Ti atoms in octahedra and highly distorted tetrahedra. There are four distinct linkages between these octahedra that include edge- and corner-shared O and S atoms. a 1995 Academic Press, Inc.