Abstract
The narrow-gap semiconductor CsBi4Te6 is a promising material for low temperature thermoelectric applications. Its thermoelectric property is significantly better than the well-explored, high-performance thermoelectric material Bi2Te3 and related alloys. In this work, the thermal expansion and the heat capacity at constant pressure of CsBi4Te6 are determined within the quasiharmonic approximation within the density functional theory. Comparisons are made with available experimental data, as well as with calculated and measured data for Bi2Te3. The phonon band structures and the partial density of states are also investigated, and we find that both CsBi4Te6 and Bi2Te3 exhibit localized phonon states at low frequencies. At high temperatures, the decrease of the volume expansion with temperature indicates the potential of a good thermal conductivity in this temperature region.
Highlights
In the recent years, thermoelectric (TE) materials have been studied extensively due to the advances in the material synthesis and an improved device performance [1] [2]
The most fundamental thermal properties of solids can be determined from the phonon dispersion ωq,v and the corresponding phonon density of states (DOS) as a function of frequency
The results reveal that the thermal expansion increases considerably with increasing temperatures in the low temperature region below 170 K
Summary
Thermoelectric (TE) materials have been studied extensively due to the advances in the material synthesis and an improved device performance [1] [2]. Persson perature; S is the Seebeck coefficient; ρ is the electrical resistivity; and κ is the thermal conductivity. Κ has contribution from the electronic κe and the lattice thermal κL conductivities [3]. The power factor S2/ρ defines the characterized electrical properties. A good thermoelectric material shall typically exhibit low thermal conductivity and a large power factor. Many research groups have reported enhanced ZT in superlattices such as the Bi2Te3/Sb2Te3 systems, where the superlattice structures reduce the lattice thermal conductivity. Novel bulk and alloy compounds, such as antimony slivery telluride and its alloys with skutterudites, have shown improved ZT value which indicates that the materials can be suitable for thermoelectric applications
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