Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals
Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals
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DOI：
10.1038/nature13184
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发表时间：
2014-04-17
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：
Zhao, Li-Dong;Lo, Shih-Han;Kanatzidis, Mercouri G.
热电效应可以在热能和电能之间进行直接和可逆的转化，并为从废热发电提供了可行的途径。热电材料的效率取决于功绩的无量纲图（其中z是优点的图形，t是绝对温度），该图控制了热转化的Carnot效率。高于通常高阈值2.5的增强功能对商业部署具有重要意义（1,2），尤其是对于没有PB和TE的化合物。在这里，我们报告了在923 K时的前所未有的ZT为2.6 +/- 0.3，在沿室 - 温度正交原晶单元的B轴的SNSE单晶体中实现。该材料还显示沿Thec轴的高ZT为2.3 +/- 0.3，但沿A轴明显降低了0.8 +/- 0.2。我们将沿B轴非常高的ZT归因于SNSE中本质上超低的晶格导热率。 SNSE的分层结构源自扭曲的岩石盐结构，并具有异常高的Gruneisen参数，反映了非谐和各向异性粘结。我们将SNSE的异常低晶格导热率（973 K）归因于非谐波。这些发现突出了纳米结构的替代策略，以实现高热电性能。
The thermoelectric effect enables direct and reversible conversion between thermal and electrical energy, and provides a viable route for power generation from waste heat. The efficiency of thermoelectric materials is dictated by the dimensionless figure of merit, ZT (where Z is the figure of merit and T is absolute temperature), which governs the Carnot efficiency for heat conversion. Enhancements above the generally high threshold value of 2.5 have important implications for commercial deployment(1,2), especially for compounds free of Pb and Te. Here we report an unprecedented ZT of 2.6 +/- 0.3 at 923 K, realized in SnSe single crystals measured along the b axis of the room-temperature orthorhombic unit cell. This material also shows a high ZT of 2.3 +/- 0.3 along thec axis but a significantly reduced ZT of 0.8 +/- 0.2 along the a axis. We attribute the remarkably high ZT along the b axis to the intrinsically ultralow lattice thermal conductivity in SnSe. The layered structure of SnSe derives from a distorted rock-salt structure, and features anomalously high Gruneisen parameters, which reflect the anharmonic and anisotropic bonding. We attribute the exceptionally low lattice thermal conductivity (0.2 +/- 0.03 Wm(-1) K-1 at 973 K) in SnSe to the anharmonicity. These findings highlight alternative strategies to nanostructuring for achieving high thermoelectric performance.