An Unlikely Route to Low Lattice Thermal Conductivity: Small Atoms in a Simple Layered Structure
An Unlikely Route to Low Lattice Thermal Conductivity: Small Atoms in a Simple Layered Structure
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DOI：
10.1016/j.joule.2018.06.014
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发表时间：
2018-09-19
期刊：
影响因子：
39.8
通讯作者：
Zevalkink, Alexandra
中科院分区：
文献类型：
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作者：
Peng, Wanyue;Petretto, Guido;Zevalkink, Alexandra
层状化合物Mg3Sb2具有与PbTe和Bi2Te3相当的低晶格热导率，尽管其密度低且结构简单。为了解释Mg_3Sb_2低热导率的原因，我们用实验和理论方法研究了AMg（2）Pn（2）Zintl化合物（A = Mg，Ca，Yb，Pn = Sb，Bi）的弹性、热膨胀和非谐性的变化趋势。声子计算揭示大模式Gruneisen参数在Mg3Sb2相比，同构化合物，特别是在横向声学模式涉及相邻层的剪切。高温共振超声光谱证实了Mg3Sb2中声学分支的快速软化。我们将Mg3Sb2的反常热行为归因于Mg的尺寸太小，对于八面体配位的位置来说太小，导致弱的层间键合。这些结果表明，尺寸过小的阳离子可能会提供一个低晶格热导率的途径，即使在地球丰富的，低密度的材料。
The layered compound Mg3Sb2 exhibits low lattice thermal conductivity comparable with PbTe and Bi2Te3, despite its low density and simple structure. To explain the origins of the low thermal conductivity in Mg3Sb2, we use experimental and theoretical methods to explore trends in the elasticity, thermal expansion, and anharmonicity of AMg(2)Pn(2) Zintl compounds with A = Mg, Ca, and Yb, and Pn = Sb and Bi. Phonon calculations reveal large mode Gruneisen parameters in Mg3Sb2 compared with isostructural compounds, in particular in transverse acoustic modes involving shearing of adjacent layers. High-temperature resonant ultrasound spectroscopy confirms the rapid softening of the acoustic branches in Mg3Sb2. We attribute the anomalous thermal behavior of Mg3Sb2 to the diminutive size of Mg, which is too small for the octahedrally coordinated site, leading to weak interlayer bonding. These results suggest that undersized cations may provide a route to low lattice thermal conductivity, even in earth-abundant, low-density materials.