Zhou Zhifang, Chai Yaw Wang, Ikuta Yu, Lee Yonghoon, Lin Yuanhua, Kimura Yoshisato
Department of Materials Science and Engineering, Tokyo Institute of Technology, 4259-J3-19, Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.
ACS Appl Mater Interfaces. 2020 Apr 29;12(17):19547-19552. doi: 10.1021/acsami.0c02549. Epub 2020 Apr 14.
Solid solutioning of Mg(Si, Sn) has been a promising approach in reducing thermal conductivity and leads to improvement of thermoelectric performance. In addition to the Mg(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 Mg(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 Mg(Si, Sn) solid solutions. Consequently, the undoped MgSiSn containing a higher density of the layered structure has relatively lower thermal conductivity, 1.9 W m K at 523 K, than MgSiSn with a much lower density of the layered structure, 2.3 W m K at 523 K.
Mg(Si,Sn)的固溶处理一直是降低热导率并改善热电性能的一种很有前景的方法。除了Mg(Si,Sn)固溶体之外，我们还注意到一种具有梯度成分的层状结构，它是由非平衡凝固和包晶反应过程形成的，并且可以进一步降低Mg(Si,Sn)固溶体的热导率。层状结构的所有层都具有相同的面心立方基结构，但每层中的Sn/Si浓度比不同。层与层之间的界面是半共格的，带有不同数量的失配位错相互交织。这样的界面结构带来大量的声子散射源，导致Mg(Si,Sn)固溶体的热导率进一步降低。因此，含有较高密度层状结构的未掺杂MgSiSn在523K时的热导率相对较低，为1.9W/(m·K)，而层状结构密度低得多的MgSiSn在523K时的热导率为2.3W/(m·K)。
