Résumé
β-As2Te3 belongs to the prominent family of Bi2Te3-based materials, which show excellent thermoelectric properties near room temperature. In this study, we report a joint theoretical and experimental investigation of its electronic and thermal properties at low temperatures (5-300 K). These results are complemented by specific heat measurements (1.8-300 K) that provide further experimental evidence of the first order lattice distortion undergone by β-As2Te3 near 190 K. Data taken on cooling and heating across this transition show that the lattice distortion has little influence on the electronic properties and further evidence a weak hysteretic behavior. Although first-principles calculations predict a semiconducting ground state, these measurements show that β-As2Te3 behaves as a degenerate p-type semiconductor with a high carrierconcentration of 1020 cm-3 at 300 K likely due to intrinsic defects. Calculations of the vibrational properties indicate that the extremely low lattice thermal conductivity values (0.8 W m-1 K-1 at 300 K) mainly originate from low-energy Te optical modes that limit the energy window of the acoustic branches. This limited ability to transport heat combined with a relatively large band gap suggest that high thermoelectric efficiency could be achieved in this compound when appropriately doped.