Anomalous enhancement of thermoelectric performance in GeTe with specific interaxial angle and atomic displacement synergy

Abstract

Discovery and engineering of novel phase structures pave new avenues in the study of phonon-electron decoupling in thermoelectric materials, with the final aim of enhancing their figure of merit ZT . Here, we report a metastable GeTe phase that shows coexisting cubic and rhombohedral phases and enhances the ZT of GeTe-based alloys to ∼0.8 at 300 K and ∼1.3 at 373 K. This is comparable with the state-of-the-art Bi 2 Te 3 -based alloys in the low-temperature range. The ZT enhancement shows a positive correlation with an increased contribution of a special rhombohedral GeTe phase with synergetic specific interaxial angle and atomic displacement, which triggers a multiple-band convergence for enhancing carrier mobility. Moreover, quenching-induced extra phase boundaries and enhanced anharmonicity may cause extra phonon scattering that reduces the lattice thermal conductivity. This work highlights the importance of precision designing phase structures for solving the phonon-electron coupling problem in thermoelectric materials. • A metastable GeTe with coexisting cubic and rhombohedral phases is revealed • An r-GeTe with a specific interaxial angle and atomic displacement is extracted • Weight carrier mobility can be dramatically increased by engineering this phase • The obtained thermoelectric performance is comparable with Bi 2 Te 3 Phase engineering provides an avenue to realize phonon-electron decoupling in thermoelectric materials. Wang et al. reveal a metastable GeTe with coexisting cubic and rhombohedral phases where the rhombohedral GeTe with synergetic specific interaxial angle and atomic displacement triggers multiple-band convergence for sharply increasing the carrier mobility.