Synthesis and Crystal Structure of a New Quaternary Chalcoantimonide:KLa_2Sb_3S_9 and KSm_2Sb_3Se_8

摘要

Silver-needle shaped crystals of KLa_2Sb_3S_9 from K_2S_x flux and KSm_2SbS_3Se_8 from NaCl/KCl flux reactions were obtained and their crystal structures were determined by the single crystal X-ray diffraction method.KLa_2Sb_3S_9 crystallizes in the orthorhombic noncentrosymmetric space group P2_12_12_1(No.19)with a unit cell of a=4.220(3)A,b=24.145(2)A,c=14.757(5)A and Z=4.KSm_2Sb-3Se_8 crystallizes in the orthorhombic space group Pnma(No.62)with a unit cell of a=16.719(3)A,b=4.1236(8)A,c=22.151(4)A and Z=4.Both structures have three-dimensional tunnel frameworks filled with K~+ ions.KSm_2Sb_3Se_8 is an ordered version of ALn_(1+-x)Bi_(4+-x)S_8,and it is made up of NaCl-type and Gd_2S_3-type fragments.KLa_2Sb_3S_9 also contains building fragments similar to those of KSm_2Sb_3Se_8,however,there are chalcogen-chalcogen bonds in the Gd_2S_3-type fragment.The formula of KLa_2Sb_3S_9 can be described as(K~+)(La~(3+))_2(Sb~(3+))_3(S~(2-))_7(S_2 ~(2-)).