New ternary phases in some alkaline-earth rare-earth sulfide systems

Open system reactions in flowing H2S have been used to form novel ternary alkaline-earth rare-earth sulfide phases of MLn2S7 composition, where M is either Ca or Sr and Ln may be La, Nd, of Gd; these phases have been characterized by X-ray powder diffraction and electron microprobe analysis. As a group, the compounds studied form as products with melting points below 1100 C when refractory compounds along the MS-Ln2S3 join are oxidized at high sulfur fugacities.