Two new ternary chalcogenides Ba2ZnQ3 (Q = Se, Te) with chains of ZnQ4 tetrahedra: syntheses, crystal structure, and optical and electronic properties
Abstract
Single crystals of Ba(2)ZnQ(3) (Q = Se, Te) were obtained by solid-state reactions at 1173 K. These isostructural compounds crystallize in the K2AgI3 structure type. The Zn atoms in this structure are coordinated to four Q atoms (2 Q1, 1 Q2, 1 Q3) and these form a distorted tetrahedron around each Zn atom. Each ZnQ(4) tetrahedron shares two corners with neighboring ZnQ(4) tetrahedra resulting in the formation of infinite chains of [ZnQ(4)(4-)] units. The absorption spectrum of a single crystal of Ba2ZnTe3 shows an absorption edge at 2.10(2) eV, consistent with the dark-red color of the crystals. From DFT calculations Ba2ZnSe3 and Ba2ZnTe3 are found to be semiconductors with electronic band gaps of 2.6 and 1.9 eV, respectively.