Dual-phonon-scattering engineering in SiGe-based heterostructures for enhanced thermoelectric performance

SiGe-based thermoelectric (TE) materials exhibit exceptional thermal stability and environmental compatibility for medium-to-high-temperature applications, but their TE performance is limited by inherently high thermal conductivity. This study demonstrates a novel strategy to overcome this limitation by introducing transition metal carbide. Among five investigated candidates (TiC, ZrC, HfC, NbC, TaC), ZrC incorporation proves most effective, achieving a peak zT of ∼1.3 at 873 K and an average zT ( zT avg ) of 0.72 across 323–873 K in n-type SiGe-based materials, representing an obvious improvement over prior reports. This improvement is mainly attributed to a substantial reduction in lattice thermal conductivity ( κ l ), decreasing from 1.98 W m −1  K −1 –1.75 W m −1  K −1 at 873 K compared to the pristine alloy. Phonon dispersion analysis reveals that the extremely low κ l stems from two factors: specific phononic characteristics of ZrC, including a small optical-optical phonon gap, weak acoustic phonon bunching, and low-frequency (∼2.9 THz) acoustic-optical coupling in comparison with other carbides; and a significant phonon spectrum mismatch at the ZrC/SiGe interface. This work advances TE material optimization through targeted dual-phonon-scattering engineering.