Cation preferences in thio-olivines (Fe1-xMgx)(2)SiS4, x <= 0.30, studied by Mossbauer spectroscopy at room temperature

Synthetic (Fe1-xMgx)(2)SiS4, Mg = 0.10, 0.20, 0.30, with olivine structure, Pnma, has been synthesized using quartz-ampoule technique. The powder mate rials have been characterized, using X-ray diffraction (XRD) and Mossbauer spectroscopy techniques. The cell parameters, a, b, c and V increase with x . Paramagnet ic Mossbauer patterns recorded at room temperature can be deco mposed into two doublets, and it is shown from comparisons with earlier sin gle crystal XRD work that the doublet showing lower value of the centroid s hift (isomer shift) and higher absolute value of the quadrupole splitting b elongs to the M1 site. This is contrary to the assignment proposed by us in an earlier report (ERICSSON et al. 1998). Iron is enriched in M1 and the d istribution coefficient K-d = 4(1). Obtained cation partitioning is compare d with literature results for thiogermanates, oxysarcopsides and oxyolivine s.