Ag-Segregation to Dislocations in PbTe-Based Thermoelectric Materials
Ag-Segregation to Dislocations in PbTe-Based Thermoelectric Materials
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DOI：
10.1021/acsami.7b17142
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发表时间：
2018-01-31
影响因子：
9.5
通讯作者：
Cojocaru-Miredin, Oana
中科院分区：
文献类型：
--
作者：
Yu, Yuan;Zhang, Siyuan;Cojocaru-Miredin, Oana
位错已被认为是散射中频声子的有效源，有助于。热电性能的提高。位错的结构可以用电子显微镜分辨，而它们的化学成分和装饰状态却几乎不为人知。在这里，我们将透射菊池衍射和（扫描）透射电子显微镜结合原子探针层析成像进行关联，以研究热电掺银碲化铅化合物中位错的锁结构和化学成分。我们的调查表明，银原子偏析位错与10倍过量的银相比，其在矩阵中的平均浓度。然而，沿着位错线的Ag浓度沿着不是恒定的，而是以约5 nm的周期从近似0.8原子%波动到近似10原子%。热导率进行评估，采用激光闪光分析，并与理论计算的基础上的Debye-Callaway模型，表明这些银装饰位错产生更强的声子散射。这些研究结果减少了知识差距，所需的理论计算的哈农散射的位错的组成，并铺平了道路，扩展到热电材料的缺陷工程的概念。
Dislocations have been considered to be an efficient source for scattering midfrequency phonons, contributing to. the enhancement of thermoelectric performance. The structure of dislocations can be resolved by electron microscopy whereas their chemical composition and decoration state are scarcely known. Here, we correlate transmission Kikuchi diffraction and (scanning) transmission electron microscopy in conjunction with atom probe tomography to investigate the lock structure and chemical composition of dislocations in a thermoelectric Ag-doped PbTe compound. Our investigations indicate that Ag atoms segregate to dislocations with a 10-fold excess of Ag compared with its average concentration in the matrix. Yet the Ag concentration along the dislocation line is not constant but fluctuates from similar to 0.8 to similar to 10 atom % with a period of about 5 nm. Thermal conductivity is evaluated applying laser flash analysis, and is correlated with theoretical calculations based on the Debye-Callaway model, demonstrating that these Ag-decorated dislocations yield stronger phonon scatterings. These findings reduce the knowledge gap regarding the composition of dislocations needed for theoretical calculations of honon scattering and pave the way for extending the concept of defect engineering to thermoelectric materials.