A new continuous two-step molecular precursor route to rare-earth oxysulfides Ln 2O 2S

A continuous two-step molecular precursor pathway is designed for the preparation of rare-earth oxysulfides Ln 2O 2S (Ln=Y, La, Pr, Nd, Sm-Lu). This new route involves a first oxidation step leading to the rare-earth oxysulfate Ln 2O 2SO 4 which is subsequently reduced to the rare-earth oxysulfide Ln 2O 2S by switching to a H 2-Ar atmosphere. The whole process occurs at a temperature significantly lower than usual solid state synthesis (T≤650 °C) and avoids the use of dangerous sulfur-based gases, providing a convenient route to the synthesis of the entire series of Ln 2O 2S. The molecular precursors consist in heteroleptic dithiocarbamate complexes [Ln(Et 2dtc) 3(phen)] and [Ln(Et 2dtc) 3(bipy)] (Et 2dtc=N,N- diethyldithiocarbamate; phen=1,10-phenanthroline; bipy=2,2′-bipyridine) and were synthesized by a new high yield and high purity synthesis route. The nature of the molecular precursor determines the minimum synthesis temperature and influences therefore the purity of the final Ln 2O 2S crystalline phase. © 2012 Elsevier Inc