High-performance bulk thermoelectrics with all-scale hierarchical architectures
High-performance bulk thermoelectrics with all-scale hierarchical architectures
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DOI：
10.1038/nature11439
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发表时间：
2012-09-20
期刊：
影响因子：
64.8
通讯作者：
Kanatzidis, Mercouri G.
中科院分区：
文献类型：
--
作者：
Biswas, Kanishka;He, Jiaqing;Kanatzidis, Mercouri G.
由于大约三分之二的使用能量作为废热损失，因此迫切需要能够直接可逆地将热量转化为电能的高性能热电材料。然而，热电材料的实际实现受到其迄今为止较低的性能值ZT的限制，根据热力学第二定律，ZT决定了卡诺效率。最近纳米结构降低导热率的成功策略在750-900开尔文（1-3）下达到了创纪录的1.5-1.8 ZT值，但仍然低于通常期望的阈值2。体热电体中的纳米结构允许声子有效散射声子光谱的很大一部分，但具有长平均自由程的声子基本上不受影响。本文表明，通过控制和微调纳米结构热电材料的中尺度结构，可以实现具有长平均自由程的载热声子的散射。因此，通过以分层的方式考虑所有相关长度尺度上的散射源——从原子尺度的晶格无序和纳米尺度的内源性沉淀到中尺度的晶界——我们实现了PbTe晶格导热系数的最大降低和热电性能的极大增强。通过对载热声子在集成长度尺度上的散射采取这种全局性的方法，我们超越了纳米结构，并证明了在915开尔文时，p型PbTe的ZT值与4摩尔浓度的SrTe内源性纳米结构和粉末加工和火花等离子烧结的介观结构相似，ZT值接近2.2。ZT超过2阈值的增加突出了多尺度分层结构在控制大块热电体声子散射中的作用和必要性，并为回收大部分废热提供了现实的前景。
With about two-thirds of all used energy being lost as waste heat, there is a compelling need for high-performance thermoelectric materials that can directly and reversibly convert heat to electrical energy. However, the practical realization of thermoelectric materials is limited by their hitherto low figure of merit, ZT, which governs the Carnot efficiency according to the second law of thermodynamics. The recent successful strategy of nanostructuring to reduce thermal conductivity has achieved record-high ZT values in the range 1.5-1.8 at 750-900 kelvin(1-3), but still falls short of the generally desired threshold value of 2. Nanostructures in bulk thermoelectrics allow effective phonon scattering of a significant portion of the phonon spectrum, but phonons with long mean free paths remain largely unaffected. Here we show that heat-carrying phonons with long mean free paths can be scattered by controlling and fine-tuning the mesoscale architecture of nanostructured thermoelectric materials. Thus, by considering sources of scattering on all relevant length scales in a hierarchical fashion-from atomic-scale lattice disorder and nanoscale endotaxial precipitates to mesoscale grain boundaries-we achieve the maximum reduction in lattice thermal conductivity and a large enhancement in the thermoelectric performance of PbTe. By taking such a panoscopic approach to the scattering of heat-carrying phonons across integrated length scales, we go beyond nanostructuring and demonstrate a ZT value of similar to 2.2 at 915 kelvin in p-type PbTe endotaxially nanostructured with SrTe at a concentration of 4 mole per cent and mesostructured with powder processing and spark plasma sintering. This increase in ZT beyond the threshold of 2 highlights the role of, and need for, multiscale hierarchical architecture in controlling phonon scattering in bulk thermoelectrics, and offers a realistic prospect of the recovery of a significant portion of waste heat.