Phase equilibria in the systems SrS-Ln2S3 (Ln=La, Nd, Gd)

T-x diagrams of SrS-Ln2S3 systems are plotted by means of physicochemical analysis methods from 1000 K to the melt. A continuous solid solution with Th3P4 type structure is produced in the systems between γ-Ln2S3 and SrLn2S4 phases. A negative deviation from the Vegard law in the lattice parameter change from the composition is manifested within the limits of a solid solution. SrLn2S4 phases are melted peritectically and have lattice parameter: SrLa2S4 at 2290 K a=0.8780 nm, SrNd2S4 at 2255 K a=0.8640 nm, SrGd2S4 at 2240 K a=0.8550 nm. Based on β-La2S3 and α=-Ln2S3 3-5 mol.% of SrS are dissolved. At 1770 K 2 mol.% of La2S3, 3 mol.% of NdS3, 4 mol.% of Gd2S3 are dissolved in SrS