Systems Ln 2X 3SnX 2 (Ln = terres rares et X = S ou Se) composés Ln 2SnS 5, définition et étude structurale

Abstract

In the ternary systems LnSnS, intermediate compounds are observed only in the quasi-binary Ln 2S 3SnS 2 sections. They have the general formula Ln 2SnS 5, and exist from La to Dy. They are orthorhombic, with the space group Pbam, and their structure was studied with single crystals of La 2SnS 5 (Jaulmes 1974) and Sm 2SnS 5 (Julien-Pouzol and Jaulmes 1976). These structures are extremely similar; they differ only by the coordination of the rare earth, which is 9 for La (with 2 relatively long bonds), and 8 for Sm. Intermediate compounds were not observed in the other regions of the ternary LnSnS systems. No ternary compound has been found in the LnSnSe systems.