New quaternary sulfides in the AE-RE-Sn-S system (AE=alkaline-earth, RE=rare earth)

Abstract: In our investigation of rare earth sulfides in the AE-RE-Sn-S (AE=alkaline-earth, RE=rare earth) system, three isostructural quaternary sulfides have been obtained. These compounds adopt the Eu5Zr3S12 structure type and crystallize in the P-62m space group (no. 189); the crystal data are as follows: Sr2Y2.67Sn3S12, a =11.600(7)Å, c =3.948(3)Å, Z =1; Ca3La2Sn3S12, a =11.5997(6)Å, c =3.9407(4)Å, Z =1; Ca3Er2Sn3S12, a =11.448(3)Å, c =3.8780(11)Å, Z =1. Single-crystal analysis indicated that the crystal structures consist of three types of building block: RES7, AES6, and SnS6 units. The structure of Sr2Y2.67Sn3S12 is characterized by the trimer-chains along the c direction, which are connected into a 3-dimensional framework by the Sn atoms via S(1), S(2), and S(3), with Sr atoms filling in the channels along the c direction. The optical band gap of 1.45eV for Ca3La2Sn3S12 was deduced from the diffuse reflectance spectrum. [Copyright &y& Elsevier]