Understanding of the Extremely Low Thermal Conductivity in High‐Performance Polycrystalline SnSe through Potassium Doping. (8th August 2016)

• Record Type: Journal Article
• Authors: Chen, Yue‐Xing; Ge, Zhen‐Hua; Yin, Meijie; Feng, Dan; Huang, Xue‐Qin; Zhao, Wenyu; He, Jiaqing
• Is Part Of: Advanced functional materials. Volume 26:Number 37(2016)
• Page Start: 6836
• Page End: 6845
• Publication Date: 2016-08-08
• Subjects: polycrystalline SnSe -- thermal conductivity -- thermoelectric materials -- transmission electron microscopy; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201602652
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : P‐type polycrystalline SnSe and K0.01 Sn0.99 Se are prepared by combining mechanical alloying (MA) and spark plasma sintering (SPS). The highest ZT of ≈0.65 is obtained at 773 K for undoped SnSe by optimizing the MA time. To enhance the electrical transport properties of SnSe, K is selected as an effective dopant. It is found that the maximal power factor can be enhanced significantly from ≈280 μW m −1 K −2 for undoped SnSe to ≈350 μW m −1 K −2 for K‐doped SnSe. It is also observed that the thermal conductivity of polycrystalline SnSe can be enhanced if the SnSe powders are slightly oxidized. Surprisingly, after K doping, the absence of Sn oxides at grain boundaries and the presence of coherent nanoprecipitates in the SnSe matrix contribute to an impressively low lattice thermal conductivity of ≈0.20 W m −1 K −1 at 773 K along the sample section perpendicular to pressing direction of SPS. This extremely low lattice thermal conductivity coupled with the enhanced power factor results in a record high ZT of ≈1.1 at 773 K along this direction in polycrystalline SnSe. Abstract : The thermal conductivity significantly decreases after K doping in polycrystalline SnSe. The absence of Sn oxides at the grain boundaries and presence of coherent nanoprecipitates in SnSe matrix result in an impressively low lattice thermal conductivity. Coupled with enhanced power factor results in a maximum figure of merit ( ZT ) ≈ 1.1 at 773 K, which is the highest value ever reported in polycrystalline SnSe.