Extreme phonon anharmonicity underpins superionic diffusion and ultralow thermal conductivity in argyrodite Ag8SnSe6-猫眼课题宝

DOI：

10.1038/s41563-023-01560-x

发表时间：

2023-05

期刊：

Nature Materials

影响因子：

41.2

通讯作者：

中科院分区：

材料科学1区

文献类型：

作者：

Q. Ren;M. Gupta;Minxian Jin;Jingxuan Ding;Jiangtao Wu;Zhiwei Chen;Siqi Lin;O. Fabelo;J. Rodríguez-Velamazán;M. Kofu;K. Nakajima;Marcell Wolf;F. Zhu;Jianli Wang;Zhenxiang Cheng;Guohua Wang;Xin-Yi Tong;Y. Pei;O. Delaire;Jie Ma

超低的导热系数和快速的离子扩散赋予了优良材料作为热电转换器和固体电解质的优异性能。然而，由于对它们复杂的原子动力学的有限了解，这两个特征之间的关联和相互依赖仍然不清楚。在这里，我们用同步加速器X射线和中子散射技术以及机器学习的分子动力学研究了银辉石Ag8SnSe6中的离子扩散和晶格动力学。我们确定了移动银的振动动力学和宿主骨架的关键相互作用，该主体骨架将低能银为主的声子的过度衰减控制为准弹性响应，从而实现了优势性。随之而来的是，长波横声学声子跨越上声子跃迁的持久性挑战了一种所谓的“类液体热传导”图景。相反，低能声子的显著热展宽，甚至开始于50 K以下，揭示了极端的声子非谐性和弱的成键是导致超低热导率(&lt；0.5 W m−1K−1)和快速扩散的势能面的基本特征。我们的结果为能量转换和存储的上离子材料中的复杂原子动力学提供了基本的见解。

Ultralow thermal conductivity and fast ionic diffusion endow superionic materials with excellent performance both as thermoelectric converters and as solid-state electrolytes. Yet the correlation and interdependence between these two features remain unclear owing to a limited understanding of their complex atomic dynamics. Here we investigate ionic diffusion and lattice dynamics in argyrodite Ag8SnSe6using synchrotron X-ray and neutron scattering techniques along with machine-learned molecular dynamics. We identify a critical interplay of the vibrational dynamics of mobile Ag and a host framework that controls the overdamping of low-energy Ag-dominated phonons into a quasi-elastic response, enabling superionicity. Concomitantly, the persistence of long-wavelength transverse acoustic phonons across the superionic transition challenges a proposed ‘liquid-like thermal conduction’ picture. Rather, a striking thermal broadening of low-energy phonons, starting even below 50 K, reveals extreme phonon anharmonicity and weak bonding as underlying features of the potential energy surface responsible for the ultralow thermal conductivity (<0.5 W m−1K−1) and fast diffusion. Our results provide fundamental insights into the complex atomic dynamics in superionic materials for energy conversion and storage.

Extreme phonon anharmonicity underpins superionic diffusion and ultralow thermal conductivity in argyrodite Ag8SnSe6

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