High Thermoelectric Performance in Electron-Doped AgBi_3S_5 with Ultralow Thermal Conductivity

摘要

We report electron-doped AgBi_3S_5 as a new high-performance nontoxic thermoelectric material. This compound features exceptionally low lattice thermal conductivities of 0.5-0.3 W m~(-1) K~(-1) in the temperature range of 300-800 K, which is ascribed to its unusual vibrational properties: "double rattling" phonon modes associated with Ag and Bi atoms. Chlorine doping at anion sites acts as an efficient electron donor, significantly enhancing the electrical properties of AgBi_3S_5. In the carrier concentration range (5 X 10~(18)-2 × 10~(19) cm~(-3)) investigated in this study, the trends in Seebeck coefficient can be reasonably understood using a single parabolic band model with the electron effective mass of 0.22 m_e (m_e is the free electron mass). Samples of 0.33% Cl-doped AgBi_3S_5 prepared by spark plasma sintering show a thermoelectric figure of merit of ~1.0 at 800 K.