Role of Self-Organization, Nanostructuring, and Lattice Strain on Phonon Transport in NaPb18-xSnxBiTe20 Thermoelectric Materials
Role of Self-Organization, Nanostructuring, and Lattice Strain on Phonon Transport in NaPb18-xSnxBiTe20 Thermoelectric Materials
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DOI：
10.1021/ja905448b
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发表时间：
2009-12-16
影响因子：
15
通讯作者：
Dravid, Vinayak P.
中科院分区：
文献类型：
--
作者：
He, Jiaqing;Gueguen, Aurelie;Dravid, Vinayak P.
利用透射电子显微镜研究了PbTe、SnTe、Pb0.65Sn0.35Te和NaPb 18-xSnxBiTe 20（x = 5，9）5种热电材料的成分和显微结构。我们确认，纯PbTe，SnTe，和Pb0.65Sn0.35Te具有均匀的晶体结构和均匀的组合物，没有任何纳米级夹杂物。另一方面，标称NaPb 9 Sn 9 BiTe 20相包含广泛的不均匀性和尺寸分布为3-7 nm的纳米结构。我们发现，该系列的NaPb 13 Sn 5 BiTe 20成员的化学结构更加复杂，除了纳米级沉淀物，自组织的层状结构，存在被确定为PbTe和SnTe的成分分析和透射电子显微镜图像模拟。密度泛函理论计算表明，层状结构的排列符合最低的总能量配置。几何相分析表明，大的分布在纳米夹杂物和层状结构的弹性应变。我们建议，界面引起的弹性扰动在矩阵中发挥决定性的作用，影响的声子传播途径。界面进一步增强声子散射，这又降低了这些系统中的晶格热导率，这直接导致热电品质因数的改善。
The composition and microstructure of five thermoelectric materials, PbTe, SnTe, Pb0.65Sn0.35Te and NaPb18-xSnxBiTe20 (x = 5, 9), were investigated by advanced transmission electron microcopy. We confirm that the pure PbTe, SnTe, and Pb0.65Sn0.35Te have a uniform crystalline structure and homogeneous compositions without any nanoscale inclusions. On the other hand, the nominal NaPb9Sn9BiTe20 phase contains extensive inhomogeneities and nanostructures with size distribution of 3-7 nm. We find that the chemical architecture of the NaPb13Sn5BiTe20 member of the series to be more complex; besides nanoscale precipitates, self-organized lamellar structures are present which were identified as PbTe and SnTe by composition analysis and transmission electron microscopy image simulations. Density functional theory calculations suggest that the arrangement of the lamellar structures conforms to the lowest total energy configuration. Geometric-phase analyses revealed large distributed elastic strain around the nanoscale inclusions and lamellar structures. We propose that interface-induced elastic perturbations in the matrix play a decisive role in affecting the phonon-propagation pathways. The interfaces further enhance phonon scattering which, in turn, reduces the lattice thermal conductivity in these systems that directly results directly in improvement in the thermoelectric figure of merit.