Fr 11/11 10:00 am, PAN 110
Prof. Jie Ma (Shanghai Jiao Tong University)
Decoupling lattice vibrations in superionic thermoelectric Ag8SnSe6 with
colossal phonon anharmonicity
Due to the ultralow lattice thermal conductivity and excellent fast ionic diffuse properties, superionic solids are extensively studied as a group of promising energy conversion and storage materials, particularly for thermoelectric and all-solid-state battery applications.
Meanwhile, unveiling the essential roles of atomic dynamics in superior thermal transport properties is crucial for further improving the performance of existing materials or designing future materials. Although the disappearance of shear recovery force and the concomitant suppression of transverse-phonon transport channel is broadly considered the main reason for the anomalous ultralow lattice thermal conductivity, this explanation has been seriously challenged and the genuine reason remains to be explored [1-3]. On the other hand, more and more attention has been put into the phonon-ion interactions in the attempt to explain the essential factors for ionic diffusion [4]. However, more details are still missed owing to limited experimental and theoretical studies of atomic dynamics. Here, we performed experiments on recently reported argyrodite-type Ag 8 SnSe 6 single crystal [5, 6] with state-of-the-art synchrotron X-ray diffraction (SXRD), single-crystal neutron diffraction (SCND), single-crystal/powder inelastic neutron scattering (INS) and quasi-elastic neutron scattering (QENS) techniques, complemented with large-scale first-principle modeling using machine-learned molecular dynamics. The momentum and energy resolved scattering measurements and simulations enable us to comprehensively map the microscopic spatio-temporal correlations of atoms responsible for bulk transport properties. It reveals that the superior thermal transport properties originate from the extremely soft chemical bonds and colossal anharmonic potential energy landscape.
References
[1] B. Li et al., Nat. Mater. 17, 226-230 (2018);
[2] D. J. Voneshen et al., Phys. Rev. Lett. 118, 145901 (2017);
[3] J. L. Niedziela et al., Nat. Phys. 15, 73-78 (2019);
[4] M. K. Gupta et al., Energy Environ. Sci. 14, 6554-6563 (2021);
[5] S. Lin et al., Joule 1, 816-830 (2017);
[6] M. Jin et al., Chem. Mater. 31, 2603-2610 (2019).