Phase diagrams of sections in the EuS-Cu2S-Nd2S3 system

Phase equilibria in the EuS-Cu 2 S-Nd 2 S 3 system were studied in an isothermal (970 K) section and NdCuS 2 -EuS and Cu 2 S-EuNdCuS 3 polythermal sections. The complex sulfide EuNdCuS 3 has an orthorhombic crystal lattice (space group Pnma ; a = 1.10438(2) nm, b = 0.40660(1) nm, c = 1.14149(4) nm), is isostructural to BaLaCuS 3 , and melts incongruently at 1470 K: EuNdCuS 3 (0.50 EuS; 0.50 NdCuS 2 ) ai 0.18 EuS ss (0.88 EuS; 0.12 NdCuS 2 ) + 0.82 L (0.415 EuS; 0.585 NdCuS 2 ); Δ H = 17.8 kJ/mol. Within the range 0.5 mol % EuS, EuNdCuS 3 -based solid solutions were not found. At 970 K, the tie lines pass from the compound EuNdCuS 3 to Cu 2 S, EuS, NdCuS 2 , and EuNd 2 S 4 phases and lie between the NdCuS 2 phase and solid solutions (ss) of γ-Nd 2 S 3 with EuNd 2 S 4 . Eutectics are formed between the compounds NdCuS 2 and EuNdCuS 3 at 32.0 mol % EuS T = 1318 K and between the compounds Cu 2 S and EuNdCuS 3 at 20.5 mol % EuNdCuS 3 and T = 1142 K. Five main subordinate triangles were identified in the system.