Reduced Thermal Conductivity of Mg2(Si, Sn) Solid Solutions by a Gradient Composition Layered Microstructure

Zhifang Zhou; Yaw Wang Chai; Yu Ikuta; Yonghoon Lee; Yuanhua Lin; Yoshisato Kimura

doi:10.1021/acsami.0c02549

Reduced Thermal Conductivity of Mg₂(Si, Sn) Solid Solutions by a Gradient Composition Layered Microstructure

ACS Appl Mater Interfaces. 2020 Apr 29;12(17):19547-19552. doi: 10.1021/acsami.0c02549. Epub 2020 Apr 14.

Authors

Zhifang Zhou^{1

2}, Yaw Wang Chai¹, Yu Ikuta³, Yonghoon Lee³, Yuanhua Lin², Yoshisato Kimura¹

Affiliations

¹ Department of Materials Science and Engineering, Tokyo Institute of Technology, 4259-J3-19, Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
² State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.
³ KELK Ltd., 3-25-1 Shinomiya, Hiratsuka, Kanagawa 254-8543, Japan.

PMID: 32243125
DOI: 10.1021/acsami.0c02549

Abstract

Solid solutioning of Mg₂(Si, Sn) has been a promising approach in reducing thermal conductivity and leads to improvement of thermoelectric performance. In addition to the Mg₂(Si, Sn) solid solutions, we have noticed a layered structure with a gradient composition, which is formed by nonequilibrium solidification and peritectic reaction process and can provide further reduction of thermal conductivity of the Mg₂(Si, Sn) solid solutions. All layers of the layered structure have the same face-centered cubic-based structure but varying Sn/Si concentration ratios in each layer. The interfaces between the layers are semi-coherent, reticulating with different numbers of misfit dislocations. Such an interfacial structure brings large numbers of phonon-scattering sources, resulting in further reduction of thermal conductivity in the Mg₂(Si, Sn) solid solutions. Consequently, the undoped Mg₂Si_0.75Sn_0.25 containing a higher density of the layered structure has relatively lower thermal conductivity, 1.9 W m^-1 K^-1 at 523 K, than Mg₂Si_0.25Sn_0.75 with a much lower density of the layered structure, 2.3 W m^-1 K^-1 at 523 K.

Keywords: Mg2(Si, Sn) solid solutions; gradient composition layered structure; phonon scattering; semi-coherent interfacial structure; thermal conductivity; thermoelectric materials.