Approaching high thermoelectric performance in p-type Cu3SbS4-based materials by rational electronic and nano/microstructural engineering

Due to the eco-friendly and earth-abundant features, p-type Cu3SbS4-based sulfides have shown great potential as cost-effective thermoelectric materials for practical applications in power generation and refrigeration. However, low electrical conductivities of p-type Cu3SbS4-based sulfides result in insufficient thermoelectric properties. In this work, a high average ZT of 0.45 and a maximum ZT of 0.85 at 623 K were obtained in Cu3SbS4-based sulfides through rational electronic and nano/microstructural engineering, achieved by mechanical alloying combined with fast spark plasma sintering techniques. Guided by theoretical calculations, we first study the physical properties of Cu3SbS4-xSex to explore the best composition (Cu3SbS3Se) that balances high thermoelectric performance, high thermal stability, and high mechanical performance. Based on this composition, we employed 4 % p-type AgSnSe2 with a narrow bandgap of similar to 0.15 eV to further boost the electrical conductivity of Cu3SbS3Se, generating a high power factor of 12.65 mu W cm(-1) K-2 at 623 K. In addition, comprehensive nano/microstructural characterizations indicate that a combination of dense grain boundaries, phase boundaries, and multi-dimensional lattice defects acts as rich sources to intensely scatter multi-frequency phonons, leading to a decreased thermal conductivity of 0.93 W m(-1) K-1 at 623 K. This work provides a new route to boost the thermoelectric properties of sulfides for practical applications.