T. Schleid, F. Lissner
Nov 20, 1992
Citations
0
Influential Citations
11
Citations
Journal
Journal of Alloys and Compounds
Abstract
Abstract The reaction of thulium and ytterbium with sulphur (2:3 molar ratios, 850°C, 7 days) in sealed silica containers yields single-crystal sesquisulphides in the presence of some NaCl as a flux. Yellow needles of F-Tm2S3 (monoclinic, P21/m (no. 11), Z = 4, α = 1115.13(9) pm, b . 389.42(3) pm, c = 1089.06(9) pm, β = 108.811(7)°, R = 0.049, Rw = 0.037) and orange beads of T-Yb2S3 (cubic, Ia 3 (no. 206), Z = 16, a = 1246.83(3) pm, R = 0.015, Rw = 0.014) are the single-phase binary products. There are four crystallographically independent Tm3+ in F-Tm2S3, two in distorted octahedral, one in monocapped and one in bicapped trigonal prismatic coordination of S2−. Previously addressed as Tm2S3-II, it is the only sesquisulphide structure known so far that offers coordination numbers of six, seven and eight for M3+ simultaneously. The crystal structure of T-Yb2S3 (bixbyite-type structure, well known for the sesquioxides of the “heavier” lanthanides as C type) exhibits two crystallographically independent Yb3+ in a more or less distorted octahedral neighbourhood of S2−.