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

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 [Y3S(1)12/2S(2)3S(3)3]1∞ 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 1.45 eV for Ca3La2Sn3S12 was deduced from the diffuse reflectance spectrum.

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► Three new quaternary sulfides have been obtained in the AE-RE-Sn-S system.
► These compounds crystallize in the Eu5Zr3S12 type structure.
► The experimental band gap is 1.45 eV for Ca3La2Sn3S12.