Parallel Dislocation Networks and Cottrell Atmospheres Reduce Thermal Conductivity of PbTe Thermoelectrics
Parallel Dislocation Networks and Cottrell Atmospheres Reduce Thermal Conductivity of PbTe Thermoelectrics
复制标题
DOI：
10.1002/adfm.202101214
复制
发表时间：
2021-03-09
影响因子：
19
通讯作者：
Zhang, Siyuan
中科院分区：
文献类型：
--
作者：
Abdellaoui, Lamya;Chen, Zhiwei;Zhang, Siyuan
位错在声子散射热输运中起着重要的作用。然而，对于本质上导热系数低的材料，如热电材料，经典模型需要极高的位错数(bbb10 （12) cm(-2)）来进一步阻碍热传输。在这项工作中，Na0.025Eu0.03Pb0.945Te的热导率在1 x 10(10) cm（-2）的中等位错密度下显着降低。位错的进一步特征，包括它们的排列、取向和局部化学，对它们的声子散射效应至关重要，并通过相关的显微镜技术进行了表征。电子通道对比成像显示单个颗粒内位错分布均匀，沿四个方向平行。透射电子显微镜（TEM）显示，平行网络是边型的，并且在每一组中共享相同的Burgers向量。原子探针层析成像显示掺杂Na在位错核处富集，形成Cottrell气氛。在瞬变电磁法的原位加热过程中，位错网络是稳定的。利用Callaway输运模型，证明了位错的平行排列和Cottrell气氛使位错在声子散射中更有效。这两种机制为降低隔热材料的导热性提供了新的途径。
Dislocations play an important role in thermal transport by scattering phonons. Nevertheless, for materials with intrinsically low thermal conductivity, such as thermoelectrics, classical models require exceedingly high numbers of dislocations (>10(12) cm(-2)) to further impede thermal transport. In this work, a significant reduction in thermal conductivity of Na0.025Eu0.03Pb0.945Te is demonstrated at a moderate dislocation density of 1 x 10(10) cm(-2). Further characteristics of dislocations, including their arrangement, orientation, and local chemistry are shown to be crucial to their phonon-scattering effect and are characterized by correlative microscopy techniques. Electron channeling contrast imaging reveals a uniform distribution of dislocations within individual grains, with parallel lines along four directions. Transmission electron microscopy (TEM) shows the parallel networks are edge-type and share the same Burgers vectors within each group. Atom probe tomography reveals the enrichment of dopant Na at dislocation cores, forming Cottrell atmospheres. The dislocation network is demonstrated to be stable during in situ heating in the TEM. Using the Callaway transport model, it is demonstrated that both parallel arrangement of dislocations and Cottrell atmospheres make dislocations more efficient in phonon scattering. These two mechanisms provide new avenues to lower the thermal conductivity in materials for thermal-insulating applications.