Ultralow thermal conductivity from transverse acoustic phonon suppression in distorted crystalline α-MgAgSb
Xiyang Li, Pengfei Liu, Enyue Zhao, Zhigang Zhang, T. Guidi, Manh Duc Le, Maxim Avdeev, Kazutaka Ikeda, Toshiya Otomo, Maiko Kofu, Kenji Nakajima, Jie Chen, Lunhua He, Yang Ren, Xun‐Li Wang, Bao‐Tian Wang, Zhifeng Ren, Huaizhou Zhao, Fangwei Wang
Abstract
Abstract Low thermal conductivity is favorable for preserving the temperature gradient between the two ends of a thermoelectric material, in order to ensure continuous electron current generation. In high-performance thermoelectric materials, there are two main low thermal conductivity mechanisms: the phonon anharmonic in PbTe and SnSe, and phonon scattering resulting from the dynamic disorder in AgCrSe 2 and CuCrSe 2 , which have been successfully revealed by inelastic neutron scattering. Using neutron scattering and ab initio calculations, we report here a mechanism of static local structure distortion combined with phonon-anharmonic-induced ultralow lattice thermal conductivity in α -MgAgSb. Since the transverse acoustic phonons are almost fully scattered by the compound’s intrinsic distorted rocksalt sublattice, the heat is mainly transported by the longitudinal acoustic phonons. The ultralow thermal conductivity in α -MgAgSb is attributed to its atomic dynamics being altered by the structure distortion, which presents a possible microscopic route to enhance the performance of similar thermoelectric materials.