Abstract
Phase formation in the FeSb2S4-FeNd2S4 and FeSb2S4-FeEr2S4 systems were studied by means of differential thermal analysis, X-ray diffraction technique, microstructural analysis and microhardness measurement. Phase diagrams of the title systems have been constructed and the formation of a quaternary sulfosalt with the FeLnSbS4 composition has been established. The compounds FeNdSbS4 and FeErSbS4 melt congruently at 960 and 1330 K, respectively, and form continuous substitutional solid solutions with FeSb2S4. Sulfosalts FeLnSbS4 crystallize in the orthorhombic structure with following unit cell parameters: a=11.392, b=14.132, c=3.746Å, sp.gr. Pbam, z=4, density ρ=4.88 g/cm3 (for FeNdSbS4); a=11.360, b=13.842, c=3.600 Å, sp. gr. Pbam z=4, ρ=5.17 g/cm3 (for FeErSbS4). The FeLnSbS4 type sulfosalts is classified under the FeSb2S4 berthierite structure.