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

Six new quaternary rare-earth sulfides Ba(3)LnInS(6) (Ln = Pr, Sm, Gd, Yb) and Ba(2)LnGaS(5) (Ln = Pr, Nd) have been synthesized for the first time. Ba(3)LnInS(6) (Ln = Pr, Sm, Gd, Yb) belong to the centrosymmetric space group R (3) over barc of the trigonal system. The structures contain infinite one-dimensional anionic chains (infinity)(1)[LnInS(6)](6-), which are built from face-sharing LnS(6) distorted triangular prisms and InS6 octahedra. Ba(2)LnGaS(5) (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)S-8 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.