1. Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals
- Author
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Zhao, Li-Dong, Lo, Shih-Han, Zhang, Yongsheng, Sun, Hui, Tan, Gangjian, Uher, Ctirad, Wolverton, C., Dravid, Vinayak P., and Kanatzidis, Mercouri G.
- Subjects
Thermoelectricity -- Research ,Crystals -- Thermal properties -- Electric properties ,Materials research ,Tin compounds -- Thermal properties -- Electric properties ,Selenides -- Thermal properties -- Electric properties ,Environmental issues ,Science and technology ,Zoology and wildlife conservation - Abstract
The main obstacle to improving the thermoelectric efficiency of a material arises from the common interdependence of electrical and thermal conductivity, whereas one ideally wants to raise the former while lowering the latter: a simple layered crystalline material -- SnSe -- is now reported that seems to have these qualities built in. Impressive thermoelectric performance from SnSe crystals Thermoelectric materials hold promise as a practical means of converting waste heat into electrical energy, but the energy-conversion efficiency of existing materials tends to be rather low. The main obstacle to improving the thermoelectric efficiency of a material arises from the common interdependence of electrical and thermal conductivity. Thermoelectric efficiency demands high electrical but low thermal conductivity and one route that might provide that combination is nanostructuring. Now Li-Dong Zhao and colleagues describe a simple layered crystalline material, tin selenide (SnSe), that appears to have these qualities built in. The authors identify features in the bonding structure of this material that they believe to be responsible, and suggest that these might help to guide the discovery of other candidate materials for high thermoelectric performance. 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.sup.1,2, especially for compounds free of Pb and Te. Here we report an unprecedented ZT of 2.6 [plus or minus] 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 [plus or minus] 0.3 along the c axis but a significantly reduced ZT of 0.8 [plus or minus] 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 Grüneisen parameters, which reflect the anharmonic and anisotropic bonding. We attribute the exceptionally low lattice thermal conductivity (0.23 [plus or minus] 0.03 W m.sup.-1 K.sup.-1 at 973 K) in SnSe to the anharmonicity. These findings highlight alternative strategies to nanostructuring for achieving high thermoelectric performance., Author(s): Li-Dong Zhao [sup.1] , Shih-Han Lo [sup.2] , Yongsheng Zhang [sup.2] , Hui Sun [sup.3] , Gangjian Tan [sup.1] , Ctirad Uher [sup.3] , C. Wolverton [sup.2] , Vinayak [...]
- Published
- 2014
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