Department of Applied Science for Electronics and Materials, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka, 816-8580, Japan.
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8568, Japan.
Adv Mater. 2018 Mar;30(13):e1706230. doi: 10.1002/adma.201706230. Epub 2018 Feb 1.
Thermoelectric devices convert heat flow to charge flow, providing electricity. Materials for highly efficient devices must satisfy conflicting requirements of high electrical conductivity and low thermal conductivity. Thermal conductivity in caged compounds is known to be suppressed by a large vibration of guest atoms, so-called rattling, which effectively scatters phonons. Here, the crystal structure and phonon dynamics of tetrahedrites (Cu,Zn) (Sb,As) S are studied. The results reveal that the Cu atoms in a planar coordination are rattling. In contrast to caged compounds, chemical pressure enlarges the amplitude of the rattling vibration in the tetrahedrites so that the rattling atom is squeezed out of the planar coordination. Furthermore, the rattling vibration shakes neighbors through lone pairs of the metalloids, Sb and As, which is responsible for the low thermal conductivity of tetrahedrites. These findings provide a new strategy for the development of highly efficient thermoelectric materials with planar coordination.
热电器件将热流转换为电荷流，从而产生电能。高效器件的材料必须满足高导电性和低导热性的矛盾要求。笼状化合物中的导热系数已知会受到客体原子的大幅振动（所谓的“ rattling ”）的抑制，这种振动会有效地散射声子。在这里，研究了四方铜矿（Cu，Zn）（Sb，As）S 的晶体结构和声子动力学。结果表明，平面配位中的 Cu 原子在 rattling 。与笼状化合物不同，化学压力会增大四方铜矿中 rattling 振动的幅度，从而使 rattling 原子从平面配位中挤出。此外，rattling 振动通过 Sb 和 As 的孤对电子来撼动邻居，这是四方铜矿低热导率的原因。这些发现为开发具有平面配位的高效热电材料提供了新策略。
