Syntheses, Structures and Band Gaps of KLnSiS(4) (Ln = Sm, Yb)

Two new quaternary sulfides,KSmSiS4(1) and KYbSiS4(2),have been synthesized by high-temperature solid-state reaction.Single-crystal X-ray diffraction analyses indicate that both compounds crystallize in the space group P21/m,and the crystal data are as follows:a = 6.426(11),b = 6.582(11),c = 8.602(15) ,β = 107.90(13)°,Z = 2,V = 346.2(10) 3,Dc = 3.317 g/cm3,F(000) = 318,μ(MoKα) = 10.334 mm-1,the final R = 0.0559 and wR = 0.1370 for 1;and a = 6.3244(10),b = 6.5552(10),c = 8.5701(15) ,β = 108.001(13)°,Z = 2,V = 337.91(9) 3,Dc = 3.621 g/cm3,F(000) = 334,μ(MoKα) = 15.737 mm-1,the final R = 0.0422 and wR = 0.0960 for 2.The KLnSiS4(Ln = Sm,Yb) structure consists of corrugated ∞2 [LnSiS4]-layers which are formed by edge-sharing LnS8 bicapped trigonal prisms and SiS4 tetrahedra.The K+ cations are located in the cavities defined by S2-anions between the ∞2 [LnSiS4]-layers.Band-gap analyses show that compounds 1 and 2 are semiconductors with optical band-gaps of 2.40 and 2.34 eV,respectively.