Impact of grain boundary characteristics on lattice thermal conductivity: A kinetic theory study on ZnO
Impact of grain boundary characteristics on lattice thermal conductivity: A kinetic theory study on ZnO
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晶界特征对晶格热导率的影响：ZnO 的动力学理论研究
DOI：
10.1103/physrevb.95.155313
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发表时间：
2017-04
影响因子：
3.7
通讯作者：
Liang Xin
中科院分区：
文献类型：
--
作者：
Liang Xin
晶界是存在于多晶材料中的自然界面，在输运性质中起着重要作用。本文以氧化锌为例，从动力学理论的角度研究了晶界晶体失配、局域杂质调制和晶格间距对晶格热导率的影响。我们采用一个基于位错的模型来描述声子的晶界散射，其中晶界的结构特征是显式固有的，晶界散射时间取决于声子的频率。这与灰色模型或常用的Casimir极限形成对比，后者对晶界特征和声子频率都是盲目的。结果表明，晶格热导率一般随晶界错向角的增大而减小，晶界间距越小，晶格热导率越小，而晶界间距越大，晶格热导率越小。有趣的是，我们的结果表明，局域晶界化学比晶体失配对声子弛豫时间和界面热阻(Kapitza)的影响更大。我们的结果表明，除了纳米结构工程方法外，晶格热导率还有新的调整机会，并证明了晶界特性对多晶体中声子传导的协同效应。
Grain boundaries are natural interfaces present in polycrystalline materials and have an important role in transport properties. In this work, the impact of grain boundary crystallographic mismatch, local impurity modulation, and spacing on lattice thermal conductivity is examined from the kinetic theory approach, with ZnO as a case study. We employ a dislocation-based model to describe the grain boundary scatterings of phonons, in which structural characteristics of grain boundaries are explicitly built-in and grain boundary scattering time depends on phonon frequency. This is in contrast to the gray model or the commonly used Casimir limit, which is blind to both grain boundary features and phonon frequency. We show that the lattice thermal conductivity generally decreases with grain boundary misorientation angle, and this dependence is significant for small grain boundary spacing while it tends to diminish for a large one. Intriguingly, our results show that local grain boundary chemistry can affect even more substantially than the crystallographic misfit on phonon relaxation time and interfacial thermal (Kapitza) resistance. Our results suggest new opportunities in tuning lattice thermal conductivity besides the nanostructure engineering approach, and demonstrates the synergetic effects of grain boundary characteristics on phonon conduction in polycrystals.