High-temperature thermoelectric properties of the β-As_2−xBi_xTe₃ solid solution

Abstract

International audienceBi2Te3-based compounds are a well-known class of outstanding thermoelectric materials. β-As2Te3, another member of this family, exhibits promising thermoelectric properties around 400 K when appropriately doped. Herein, we investigate the high-temperature thermoelectric properties of the β-As2−xBixTe3 solid solution. Powder X-ray diffraction and scanning electron microscopy experiments showed that a solid solution only exists up to x = 0.035. We found that substituting Bi for As has a beneficial influence on the thermopower, which, combined with extremely low thermal conductivity values, results in a maximum ZT value of 0.7 at 423 K for x = 0.017 perpendicular to the pressing direction

β−As2Te3 : Pressure-induced three-dimensional Dirac semimetal with ultralow room-pressure lattice thermal conductivity

“…Moreover for β-As 2 Te 3 it has experimentally been observed that there is a temperature dependence of the thermal conductivity, for which κ L decreases monotonically with increasing temperature, following roughly a T −1 power law. Such a feature suggests that Umklapp scattering events dominate the thermal transport in this temperature range [19,20]. The κ L values at room temperature, measured in the parallel direction were found to be low, of the order of 0.5 Wm −1 K −1 , however higher than the value obtained in the present calculations at 0.5 GPa.…”

“…Since the tetradymite structure is stable at room conditions, as demonstrated by several experimental studies performed for this compound [10,11,13,[19][20][21]56], we infer that the instability observed at 0 GPa, and located at the Z point, appears because we do not consider the anharmonic effects for the lattice-dynamics calculations. By including the anharmonic contributions, the rhombohedral structure of As 2 Te 3 at 0 GPa would probably tend to stabilize, thus suggesting that these effects can be very important for this compound, namely at the low pressure regime.…”

“…As 2 Te 3 is also very interesting since it has the ability to display rich polymorphism for different experimental conditions (temperature and/or pressure) such as the metastable tetradymite structure (β-As 2 Te 3 ) [5,[10][11][12] and the lowtemperature phase with P2 1 /m symmetry (β -As 2 Te 3 ) [13]. In particular, several theoretical studies have addressed the structural, mechanical, and electronic properties of β-As 2 Te 3 at room conditions [14][15][16][17][18] and it has been experimentally demonstrated that this phase also displays good thermoelectric properties [19][20][21]. Moreover, recent calculations [17,18] show that β-As 2 Te 3 exhibits other outstanding properties, for instance as PCM, which are also related to respective TI features.…”

“…According to a theoretical study [33], it is demonstrated that uniaxial strain could cause a quantum topological phase transition (QTPT) from a band insulator to a TI state at 1.8 GPa. Another theoretical study has shown that application of isotropic strain [20] enables an overlap of the electronic bands at the Fermi level ( V/V ∼ −7%), accompanied by a metallic state transition, characteristic of an ETT [20].…”

Stabilization of Metastable Thermoelectric Crystalline Phases by Tuning the Glass Composition in the Cu–As–Te System

“…The different behaviors observed between the crystalline and composite compounds may then be explained by the different actual compositions of the phases crystallized from the glassy matrix and synthesized separately. As in Bi 2 Te 3 , small deviations from the ideal stoichiometry in both α-As 2 Te 3 and β-As 2 Te 3 are present and strongly affect the thermoelectric properties through variations in the carrier concentration. ,,, …”