Understanding of the Extremely Low Thermal Conductivity in High-Performance Polycrystalline SnSe through Potassium Doping

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• 作者：Yue-Xing Chen ; Zhen-Hua Ge ; Meijie Yin ; Dan Feng ; Xue-Qin Huang ; Wenyu Zhao and Jiaqing He
• 刊名：Advanced Functional Materials
• 出版年：2016
• 出版时间：October 4, 2016
• 年：2016
• 卷：26
• 期：37
• 页码：6836-6845
• 全文大小：2514K
• ISSN：1616-3028

文摘

P-type polycrystalline SnSe and K_0.01Sn_0.99Se 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.