Thermoelectric properties of phosphorus-doped van der Waals crystal Ta4SiTe4

Recently, one-dimensional van der Waals crystal Ta4SiTe4 has been reported as a promising low temperature thermoelectric material. Extraordinarily high power factor has been reported for the onedimensional Ta4SiTe4 single whisker and two-dimensional (PVDF)/Ta4SiTe4 composite film, but the thermoelectric properties of three-dimensional Ta4SiTe4 polycrystalline bulks have been rarely investigated. In this study, we prepared a series of phosphorus (P)-doped Ta4SiTe4 polycrystalline bulks by using the high-temperature synthesis and cold press method. Their electrical and thermal transport properties along the directions parallel and perpendicular to the pressure were systematically investigated. Upon doping P at the Si-sites to increase the carrier concentration, the electrical conductivity is enhanced while the intrinsic excitation is suppressed, resulting in significantly improved power factor approaching the theoretically optimal value. All Ta(4)Si(1-x)PxTe(4) bulks possess low lattice thermal conductivities with the values below 1.2 Wm(-1)K(-1). The weak van der Waals interaction among the [Si2Ta8Te8](n) chains results in the appearance of low-lying optical modes and introduces additional scattering to phonons. A peak thermoelectric figure of merit value of 0.18 is obtained at 300 K for polycrystalline Ta4Si0.995P0.005Te4, about double that of pristine polycrystalline Ta4SiTe4. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

By studying phosphorus-doped Ta4SiTe4 polycrystalline bulks, it was found that increasing carrier concentration leads to enhanced electrical conductivity, improved power factor, and reduced thermal conductivity. This results in enhanced thermoelectric performance for the material.