Ba₃LnInS₆ (Ln = Pr, Sm, Gd, Yb) and Ba₂LnGaS₅ (Ln = Pr, Nd): Syntheses, Structures, and Magnetic and Optical Properties

Six new quaternary rare-earth sulfides Ba3LnInS6 (Ln = Pr, Sm, Gd, Yb) and Ba2LnGaS5 (Ln = Pr, Nd) have been synthesized for the first time. Ba3LnInS6 (Ln = Pr, Sm, Gd, Yb) belong to the centrosymmetric space group R3̅c of the trigonal system. The structures contain infinite one-dimensional anionic chains 1∞[LnInS6]6–, which are built from face-sharing LnS6 distorted triangular prisms and InS6 octahedra. Ba2LnGaS5 (Ln = Pr, Nd) crystallize in the centrosymmetric space group I4/mcm of the tetragonal system. Their structures consist of (BaLn)S layers built from (BaLn)­S8 bicapped trigonal prisms. These layers are stacked perpendicular to the c axis and further connected by GaS4 tetrahedra to form a three-dimensional framework with channels occupied by Ba2+ cations. As deduced from magnetic susceptibility measurements on Ba2NdGaS5, it is paramagnetic and obeys the Curie–Weiss law. Besides, the band gap of Ba2NdGaS5 is determined to be about 2.12(2) eV.