Synthesis And Characterization Of A New Quaternary Selenide Ba4sn3gese9 Containing [Sngese5](4-) And [Sn2se4](4-) Units

A new quaternary selenide Ba4Sn3GeSe9 was synthesized by high temperature solid state reaction method and fully characterized by elemental analysis, UV-vis spectrum, and single-crystal X-ray diffraction. The title compound crystallizes in the orthorhombic space group Pnma with a = 12.463(3), b = 9.308(2) and c = 17.892(5) angstrom. Ba4Sn3GeSe9 can be characterized by a zero-dimensional compound composed by special [GeSnSe5](4-) units, [Sn2Se4](4-) units and the adjacent cations Ba2+ ions. The [GeSnSe5](4-) unit is composed of a SnSe3 trigonal pyramid formed by divalent Sn2+ and edge-sharing with a GeSe4 tetrahedron, and the [Sn2Se4](4-) unit is composed of two SnSe3 trigonal pyramids. Ba4Sn3GeSe9 is an indirect semiconductor with a band gap of 1.21 eV.