Polythermal Section FeSb2S4–FeSm2S4 of the FeS–Sb2S3–Sm2S3 System

Abstract

Phase equilibria in the FeSb2S4–FeSm2S4 system were studied by physicochemical analysis methods (differential thermal and X-ray powder diffraction analyses and microhardness and density measurements), and the T–x phase diagram of the system was constructed. Intermediate phase FeSmSbS4 melting congruently at 1255 K was found to form. According to the X-ray powder diffraction data, FeSmSbS4 crystallizes in the orthorhombic system with the unit cell parameters a = 11.446 A, b = 14.160 A, c = 3.800 A, Z = 4, space group Pnam, ρpycn = 4.96 g/cm3, and ρX-ray = 5.00 g/cm3. In the FeSb2S4–FeSmSbS4 segment of the phase diagram of the FeSb2S4–FeSm2S4 system, an unlimited series of solid solutions with an orthorhombic unit cell forms. The isothermal section of the FeS–Sb2S3–Sm2S3 system at 298 K was constructed. The molar specific heat Cp (T) of FeSb2S4 was approximated within the range 300–800 K.