High Thermoelectric Performance in n-Type Polycrystalline SnSe via Dual Incorporation of Cl and PbSe and Dense Nanostructures
High Thermoelectric Performance in n-Type Polycrystalline SnSe via Dual Incorporation of Cl and PbSe and Dense Nanostructures
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DOI：
10.1021/acsami.9b08108
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发表时间：
2019-06-19
影响因子：
9.5
通讯作者：
Chung, In
中科院分区：
文献类型：
--
作者：
Cha, Joonil;Zhou, Chongjian;Chung, In
尽管对新兴热电材料SnSe进行了大量的研究，但其n型形式在很大程度上是不发达的，主要原因是载流子浓度难以稳定在最佳水平。在本征p型SnSe中，我们双引入Cl和PbSe来诱导n型导电。PbSe合金在提高功率因数的同时抑制了晶格热导率，在823 K时，n型多晶SnSe材料的热电性能ZT最高，为1.2。最佳成分为Sn0.90Pb0.15Se0.95Cl0.05。固相反应制备的样品在平行和垂直于火花等离子体烧结的压制方向上，ZT（max）接近1.1，ZT（max）接近0.8。值得注意的是，后球磨和退火工艺大大降低了结构的各向异性，从而导致两个方向上的ZT（max）都接近1.2。因此，该系统使用专门的样品制备方法，可以控制给出ZT（max）的方向。球面像差校正后的扫描透射电镜分析显示，存在高密度的边缘位错和应变场，而在p型对应物中没有观察到，这有助于降低晶格热导率。我们采用Callaway-Debye模型的理论计算支持热输运和微观结构的实验结果。
Despite extensive studies on emerging thermoelectric material SnSe, its n-type form is largely underdeveloped mainly due to the difficulty in stabilizing the carrier concentration at the optimal level. Here, we dually introduce Cl and PbSe to induce n-type conduction in intrinsic p-type SnSe. PbSe alloying enhances the power factor and suppresses lattice thermal conductivity at the same time, giving a highest thermoelectric figure of merit ZT of 1.2 at 823 K for n-type polycrystalline SnSe materials. The best composition is Sn0.90Pb0.15Se0.95Cl0.05. Samples prepared by the solid-state reaction show a high maximum ZT (ZT(max)) similar to 1.1 and similar to 0.8 parallel and perpendicular to the press direction of spark plasma sintering, respectively. Remarkably, post-ball milling and annealing processes considerably reduce structural anisotropy, thereby leading to a ZT(max)similar to 1.2 along both the directions. Hence, the direction giving a ZT(max) is controllable for this system using the specialized preparation methods for specimens. Spherical aberration-corrected scanning transmission electron microscopic analyses reveal the presence of heavily dense edge dislocations and strain fields, not observed in the p-type counterparts, which contribute to decreasing lattice thermal conductivity. Our theoretical calculations employing a Callaway-Debye model support the experimental results for thermal transport and microscopic structures.