Quaternary sulfides of the PbLnCuS₃ type (Ln–La, Nd, Sm, Gd, Dy, Er) have been obtained either by melting the elements or through furnace charge, 2PbS+Cu₂S+Ln₂S₃ in a graphite crucible placed in a sealed quartz ampoule at a temperature of 1200–1275 K. Monocrystals of PbSmCuS₃ and PbGdCuS₃ have been grown by mineralization method. The study of X-ray analysis showed that compounds of PbLnCuS₃ type crystallize in the orthorhombic singony (а=8.26¸8.20; b=8.84¸8.80; с=7.96¸7.9Å, space group Pmn2₁). In a series of PbLnCuS₃ compounds, the phenomenon of morphotropy manifests itself, which flows from the exchange of the structural type (PbCuSbS₃ ®KZrCuSe₃ ® Eu₂CuS₂), i.e. when the radius of the cation Ln changes. Their standard thermodynamic functions have been calculated and the temperature dependences of the magnetic susceptibility have been measured

doi.org/10.32737/0005-2531-2023-1-169-175