Abstract
Most crystalline materials follow the guidelines of T-1 temperature-dependent lattice thermal conductivity (κL) at elevated temperatures. Here, we observe a weak temperature dependence of κL in Mg3Sb2, T-0.48 from theory and T-0.57 from measurements, based on a comprehensive study combining ab initio molecular dynamics calculations and experimental measurements on single crystal Mg3Sb2. These results can be understood in terms of the so-called "phonon renormalization"effects due to the strong temperature dependence of the interatomic force constants (IFCs). The increasing temperature leads to the frequency upshifting for those low-frequency phonons dominating heat transport, and more importantly, the phononphonon interactions are weakened. In-depth analysis reveals that the phenomenon is closely related to the temperature-induced asymmetric movements of Mg atoms within MgSb4 tetrahedron. With increasing temperature, these Mg atoms tend to locate at the areas with relatively low force in the force profile, leading to reduced effective 3rd-order IFCs. The locally asymmetrical atomic movements at elevated temperatures can be further treated as an indicator of temperature-induced variations of IFCs and thus relatively strong phonon renormalization. The present work sheds light on the fundamental origins of anomalous temperature dependence of κL in thermoelectrics.
Original language | English (US) |
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Article number | 4589786 |
Journal | Research |
Volume | 2020 |
DOIs | |
State | Published - Nov 30 2020 |
Funding
This work was supported by the National Key Research and Development Program of China (Nos. 2018YFB0703600, 2017YFB0701600, and 2019YFA0704901), Natural Science Foundation of China (Grant Nos. 11674211, 51632005, and 51761135127), and the 111 Project D16002. W.Z. also acknowledges the support from the Guangdong Innovation Research Team Project (No. 2017ZT07C062), Guangdong Provincial Key Lab program (No. 2019B030301001), Shenzhen Municipal Key Lab program (ZDSYS20190902092905285), and Shenzhen Pengcheng-Scholarship Program. C.F. acknowledges funding support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Projektnummer (392228380). Y.X. and C.W. acknowledge the financial support received from the U.S. Department of Commerce and National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD) under Grant No. 70NANB14H012. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy (U.S. Department of Energy Contract No. DEAC02-05CH11231).
ASJC Scopus subject areas
- General