Abstract Scope |
In order to obtain the mechanism of the low thermal conductivity in the superionic heavy-metal materials, different methods have been investigated, such as the liquid-behaviors, anharmonicity, phonon folding, etc.. Recently, the Ag9GaSe6-family has been reported as a perfect thermoelectric system as an alloy with wooden-level thermal conductivity. We successfully synthesized the Ag9GaSe6-based samples and applied neutron scattering technique with large machine-learned MD simulations and DFT to study the lattice and dynamic spectra of the single crystal Ag8SnSe6. In addition, both diffusing behavior of Ag-ions and the bond information were obtained. The Sn-ions and Se-ions build up the host lattice frame, while the Ag-ion contributes the mobile vibrations and regulate the damping of phonons, which clearly promoting the superionicity of this system. Unlike the low-dimensional liquid behavior, the ultra-low thermal conductivity is originated from the thermal broadening of low-energy phonons reveals extreme anharmonicity and weak bonding. |