Strong anharmonic phonon scattering and superior thermoelectric properties of Li2NaBi

Abstract

The thermal transport and thermoelectric properties of bialkali bismuthide compound Li2NaBi are comprehensively investigated using first-principles calculations. The quartic anharmonic renormalization increases the acoustic phonon group velocity at high temperatures. The suppression of three-phonon scattering by the acousto-optic band gap highlights the importance of four-phonon scattering. Strong anharmonic phonon scattering causes the lattice thermal conductivity of Li2NaBi to drop rapidly at high temperatures to only 0.73 Wm−1K−1 at 900 K. Furthermore, good dispersion and high degeneracy in the electronic structure provide higher power factors than most thermoelectric materials. Finally, n-type and p-type Li2NaBi captured ZT values of 2.66 and 2.30 at 900 K, exhibiting excellent thermoelectric performance. This paper reports Li2NaBi as a promising thermoelectric candidate material and elucidates the physical mechanism of its thermal and electrical transport.