Stacking Fault-Induced Minimized Lattice Thermal Conductivity in the High-Performance GeTe-Based Thermoelectric Materials upon Bi₂Te₃ Alloying

Materials with low lattice thermal conductivity (κlat) are crucial for the applications of thermal insulation and thermoelectric (TE) energy conversion. Stacking fault (SF)-induced phonon scattering within interfaces has been put forward theoretically by Klemens in 1950s. However, unlike other traditional defects such as point defects, grain boundaries, and dislocations, the role of SF for reducing κlat remains poorly understood and is yet to be revealed experimentally. The layered Bi2Te3 with a van der Waals gap shows different stacking structures than the nonlayered GeTe, which is used to introduce SFs into the GeTe-based alloys in this work. On the basis of the experimental and theoretical modeling results, this paper reveals the significant contribution of SF phonon scattering for minimizing the κlat. Besides the achieved extremely low κlat (∼0.39 W m-1 K-1 at 573 K), optimized carrier density and band convergence are also realized in the GeTe-based alloys upon Bi2Te3 alloying, leading to a significant high TE figure of merit ZT > 2 at 773 K and an averaged ZT > 1.4 within 300-773 K. This SF engineering strategy provides a different avenue to reduce the κlat for enhancing the performance of thermal insulation and TE materials.