Oligomerization Versus Polymerization of Te_x^n- in the Polytelluride Compound BaBiTe₃. Structural Characterization, Electronic Structure, and Thermoelectric Properties

Abstract

The compound BaBiTe3 was prepared by the reaction of Ba/Bi/Te at over 700 °C in either K2Te4 or BaTe3 flux and was recrystallized in a Ba/BaTe3 flux. The black rod-shaped polycrystalline material crystallizes in the orthorhombic space group P212121 (no. 19) with a = 4.6077(2) Å, b = 17.0437(8) Å, c = 18.2997(8) Å, V = 1437.1(2) Å3, Z = 8, and d calc = 6.74 g/cm3. Number with F o 2 > 3σ(Fo)2 3373, number of variables 92, and sin (θ/λ) < 0.7. The final R/R w = 4.55/5.61%. The structure is BaBiSe3 type and may be described as layers made up from interdigitating columnar [Bi4Te10(Te2)]∞ “herring-bone” shaped segments. Ba2+ ions are in distorted tri-capped trigonal prismatic sites between the layers. From band structure calculations, a formal charge distribution taking into account the occurrence of short-bonding Te···Te contacts in the structure can be written as Ba2+ 4Bi3+ 4Te2- 8Te1- 4. The electrical conductivity, thermopower, thermal lattice conductivity, and infrared absorption properties of this material suggest that it is a narrow gap semiconductor. These results are discussed in the context of the band scheme.

Synthesis, Crystal Structures, Optical Properties and Theoretical Calculations of Two Metal Chalcogenides Ba2AlSbS5 and Ba2GaBiSe5

“…With stereochemically active lone-pair electrons, the above trivalent cations exhibit a flexible coordination environment for the formation of M III 'Q n units (n = 3~6; Q = chalcogen), which offers an opportunity to affect their crystal structures and physicochemical properties [13][14][15][16][17][18][19][20][21][22][23][24]. For example, AAsQ 2 (A = Li, Na; Q = S, Se) [15] and A 3 Ta 2 AsS 11 (A = K, Rb) [13] compounds feature [AsS 3 ] 3-pyramids and show strong second harmonic generation (SHG) responses; BaBiTe 3 , AgBi 3 S 5 and A 2 Bi 8 Se 13 (A = Rb, Cs) compounds exhibit small bandgaps and have promising potential as thermoelectric materials [22][23][24]; Ba 2 GaAsSe 5 shows novel [AsGaSe 5 ] 4− anions and high visible-light-induced photocatalytic reactivity [17]. In addition, overall literature research indicates that the above M III 'Q n units can bridge other functional units to form a variety of extended structures [16].…”

Electronic structure and thermoelectric power of cerium compounds at high pressure

“…A variety of materials like skutturudites, intermediate valence compounds [3,4], semiconducting Bi-Sb alloys [5,6] and clathrates [7,8] have been studied and reported to have improved thermoelectric properties. In many of these compounds, pressure tuning of the electronic structure has demonstrated unprecedented thermoelectric figures of merit [3,9].…”

Crystal and electronic structure of the red semiconductor Ba4LaSbGe3Se13 comprising the complex anion [Ge2Se7–Sb2Se4–Ge2Se7]14−

“…Among the most studied materials in thermoelectric research are ternary and higher antimony chalcogenides [1][2][3][4][5][6][7][8][9][10], bismuth chalcogenides [11][12][13][14][15], and germanium and tin-based clathrates [16][17][18][19]. A particularly well explored family of high-temperature thermoelectrics is (AgSbTe 2 ) 1Àx (GeTe) x (TAGS) [20,21].…”