Understanding of the Extremely Low Thermal Conductivity in High-Performance Polycrystalline SnSe through Potassium Doping
Understanding of the Extremely Low Thermal Conductivity in High-Performance Polycrystalline SnSe through Potassium Doping
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DOI：
10.1002/adfm.201602652
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发表时间：
2016-10-04
影响因子：
19
通讯作者：
He, Jiaqing
中科院分区：
文献类型：
--
作者：
Chen, Yue-Xing;Ge, Zhen-Hua;He, Jiaqing
采用机械合金化（MA）和放电等离子烧结（SPS）相结合的方法制备了p型SnSe和K0.01Sn0.99Se多晶。通过优化MA时间，在773 K时获得了最高ZT，约为0.65。为了提高SnSe的电输运性能，选择K作为有效的掺杂剂。研究发现，未掺杂SnSe的最大功率因数可以显著提高，从约280 μ W m(-1) K-2提高到约350 μ W m(-1) K-2。研究还发现，对SnSe粉末进行轻微氧化，可以提高SnSe多晶的导热性。令人惊讶的是，在K掺杂后，晶界处Sn氧化物的缺失和SnSe基体中相干纳米沉淀的存在使得773 K时沿垂直于SPS压紧方向的样品截面的晶格热导率非常低，接近0.20 W m(-1) K-1。这种极低的晶格热导率加上增强的功率因数导致多晶SnSe在773 K时沿此方向的ZT达到创纪录的1.1。
P-type polycrystalline SnSe and K0.01Sn0.99Se are prepared by combining mechanical alloying (MA) and spark plasma sintering (SPS). The highest ZT of approximate to 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 signifi cantly from approximate to 280 mu W m(-1) K-2 for undoped SnSe to approximate to 350 mu W 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 approximate to 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 approximate to 1.1 at 773 K along this direction in polycrystalline SnSe.