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<i> R</i>3̅<i>c</i> 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 <i>I</i>4/<i>mcm</i> 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 <i>c</i> 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