Formation Phases and Electrical Properties of Ge-Bi-Te Compounds with Homologous Structures

Abstract

We prepared polycrystalline samples of GeBi 6Àx In x Te 10 (x = 0, 0.06, 0.18, 0.3, and 0.6) by melting a stoichiometric mixture of Ge, Bi, In, and Te, followed by quenching in water and annealing at 723 K for 1 week. Under these preparation conditions and irrespective of the degree of In-substitution, the samples contained two different periodic structures: GeBi 6 Te 10 and GeBi 4 Te 7 structures. The relationship between the Seebeck coefficient, electrical resistivity, and phase fraction of the two structures was investigated at room temperature. We concluded that changes in the transport properties for all samples may reflect a mixture effect of the phase fraction of the two structures and the amounts of In-substitution in the framework of the assumed structure model in this study. The thermoelectric properties of the samples with x = 0 and 0.18 were determined from 300 K to 723 K from the measured electrical properties and the reported lattice thermal conductivity. The sample with x = 0.18 had the highest dimensionless figure of merit: ZT max = 0.11 at 466 K, which was 1.8 times larger than that of the sample with x = 0.

SYNTHESIS AND CRYSTAL STRUCTURE OFA NEW 9P–TYPE LAYERED van der WAALSCOMPOUND SnBi4Te4

“…Recently preparation of mixed-layered compounds having thermoelectric properties are considered to be a more effective method for material design [6][7]. The literature data shows that, the systems -( = Ge, Sn, Pb; =Sb, Bi; =Se, Te) host tetradymite-type layered ternary compounds and exhibit promising thermoelectric properties [7][8][9][10][11][12][13][14]. On the other hand, the discovery of the topological insulating properties in these compounds made themmuch more attractive in the last few years [15][16][17][18][19][20].…”

Synthesis and study of a novel 9P-type mixed layered tetradymite-like GeBi4Te4 compound in the Ge-Te-Bi system

“…One of the contemporary methods in seeking new functional materials is preparation of phases with more complex and long-period mixed layered structures. Ternary compounds of the homologous series (A IV Te)n(𝐵 2 𝑉 Te3)m (A IV = Ge, Sn, Pb; B V = Sb, Bi) are long studied thermoelectric materials [5][6][7][8][9][10][11][12]. The thermal conductivity of such alloys posessing a large unit cell and heavy element atoms, is reduced due to the effective scattering of phonons, that causes to the increase of the thermoelectric effect.…”

Boundaries of the X Phases in Sb–Te and Bi–Te Binary Alloy Systems

“…Both materials allow the recording or rewriting of data as a result of a reversible transition between crystalline and amorphous phases in response to temperature changes due to irradiation with laser light. The thermoelectric properties of these compounds have been examined so as to improve their performance [3][4][5], and research has also been performed with Ge-Bi-Te compounds obtained by the addition of Ge [6]. The properties of these materials are highly correlated with their crystal structures; therefore, the improvement of these compounds will require a good understanding of their structures, temperature characteristics and phase changes.…”