报告时间：2024年8月8日上午9:00

报告地点：武汉大学尖端科技楼2楼报告厅

Biography：Dr. Lei Jin is a permanent staff scientist in the Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich GmbH, Germany since 2017. He received his Ph.D. degree from School of Physics and Technology and Center for Electron Microscopy, Wuhan University, China in 2008, supervised by Prof. Jian-bo Wang. From 2005 to 2006, he acted as a technical assistant (exchange student) in Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China. After staying shortly in Wuhan University in 2009, he was a postdoctoral researcher in the Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, Germany from 2009 to 2016. In 2021, he was awarded the Feodor Lynen Fellowship for experienced scientists, funded by Alexander von Humboldt foundation and stayed one year (2022-2023) in Weizmann Institute of Science, Israel. His research interests include quantitative high-resolution transmission electron microscopy and spectroscopy, structural defects in functional materials and related behavior under working conditions.

Abstract:

Skutterudite, characterized by the chemical formula MX3 or M4X12 (M = Co, Rh, or Ir and X = P, As, or Sb), represents an extended group of materials that have intrinsic inner “cages” formed by corner-sharing MX6 octahedra. The most studied skutterudites for mid-temperature thermoelectric applications are antimony-based alloys, i.e., (Fe,Co)4Sb12, due to the relatively high power factor and comparatively low thermal conductivity, which could be achieved through structural modifications. The most effective modification to lower the thermal conductivity is to introduce fillers, for instance, alkali metals, rare earth, alkaline earth, and the XIII group elements, into the interstitial sites of the cage-like (Fe,Co)4Sb12 lattice. It is generally accepted that the filler atoms are loosely bonded with surrounding (Fe,Co)-Sb “cages” and rattle around individual equilibrium positions with one or more characteristic frequencies (so-called rattlers), thus resulting in the reduction of thermal conductivity.

Though considerable efforts have been devoted to the detection of fillers in real space using advanced transmission electron microscopy (TEM), direct evidence of positions as well as concentration for filler atoms was rarely reported so far, in particular at the atomic resolution.

In this talk, I will present our recent studies of both N- and P-type filled skutterudites by employing the negative spherical aberration imaging (NCSI) technique. We have observed the filler atoms of nominally 20 at.% Yb and fully-filled Ce in (Co,Fe)4Sb12 and measured their off-center shifts cage-by-cage with picometer precision on the basis of image quantifications. This provides atomic-scale evidence for off-centering rattlers in filled skutterudites [1]. Further imaging with reduced electron dose is also performed using a modified integrated differential phase contrast (iDPC) technique [2]. From our results, we argue that the observed off-center shift of fillers is static.

References:

[1] Z.H. Ge, W.J. Li, J. Feng, F. Zheng, C.L. Jia, D. Wu, L. Jin, Adv. Energy Mater. 12 (2022) 2103770.

[2] The author thanks Penghan Lu, Ivan Lazić, Eric G. T. Bosch, Juri Barthel, Zhen-Hua Ge and Rafal E. Dunin-Borkowski for collaborations.

武汉大学科研公共服务条件平台

湖北省电子显微镜学会

武汉大学电子显微镜中心