Ternary and quaternary silver chalcogenides are promising semiconductor materials for practical use that possess various valuable physical properties such as optical, electric, ferroelectric, ionic conductivity. Antimony chalcogenides are of interest to the research for thermoelectric properties and optical absorption suitable for thin-film solar cells. Our investigation combined these two directions in the quasi-ternary systems Ag₂S–C^III₂S₃–D^IVS₂ (C^III–Sb, As; D^IV–Ge, Sn) where three new quaternary sulfide compounds were found, Ag₁₁GeSb₃S₁₂, Ag₁₁SnSb₃S₁₂, and Ag₁₁SnAs₃S₁₂.

Alloys of the systems were synthesized by co-melting the elements at up to 1220 K, slow cooling to 500 K, annealing for 500 hrs followed by quenching. Ag₁₁GeSb₃S₁₂ forms at the intersection of AgSbS₂–Ag₈GeS₆ and Ag₃SbS₃–Ag₂GeS₃; Ag₁₁SnSb₃S₁₂ forms at the intersection of AgSbS₂–Ag₈SnS₆ and Ag₃SbS₃–Ag₂SnS₃; and Ag₁₁SnAs₃S₁₂ forms at the intersection of AgAsS₂–Ag₈SnS₆ and Ag₃AsS₃–Ag₂SnS₃. In all cases, the component ratio is 3:1. X-ray phase analysis and microstructure studies show that each compound has a modest homogeneity region of up to 5 mol.%.

The crystal structure of Ag₁₁GeSb₃S₁₂ was investigated by X-ray structural analysis. The diffraction dataset was recorded at a DROM 4-13 powder diffractometer, CuKα radiation, angle range 10°≤2Θ≤100°, scan step 0.02°, 10 s exposure in each point. The diffraction pattern of Ag₁₁GeSb₃S₁₂ was indexed in the cubic symmetry, space group I3m, lattice parameter а=0.54127(2) nm. Sulfur atoms form three-layer closest packing, the statistical mixture of Ag and Ge atoms occupies one half of the octahedral voids, and Sb atoms occupy one quarter of the tetrahedral voids.

Further investigation of the crystal structure of two other compounds as well as the study of optical absorption and electrophysical properties to quantify the prospects of these compounds as materials is pending.