Ultrahigh Thermoelectric Performance in Environmentally Friendly SnTe Achieved through Stress-Induced Lotus-Seedpod-Like Grain Boundaries

In an effort to improve the thermoelectric performance of the environmentally friendly SnTe, here, a multilevel structure composed of “lotus-seedpod-like” grain boundaries, dense dislocations, and nanopores is innovatively constructed, which synergistically reduces the sound velocity and the phonon relaxation time, resulting in ultralow lattice thermal conductivity throughout a wide temperature range. An ultrahigh figure of merit, ZT, of ≈1.7 and an unprecedented average ZT of ≈1 from 300 to 873 K are obtained. In contrast to the common pore-forming method of volatilization, the strategy of stress-induced recrystallization and gas expansion cogenerating interfacial pores that is used here, is believed to be more widely applicable for many other materials, which opens up a new avenue for improving thermoelectric performance.