Chemical Insights into PbSe-x%HgSe: High Power Factor and Improved Thermoelectric Performance by Alloying with Discordant Atoms
Chemical Insights into PbSe-x%HgSe: High Power Factor and Improved Thermoelectric Performance by Alloying with Discordant Atoms
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DOI：
10.1021/jacs.8b11050
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发表时间：
2018-12-26
影响因子：
15
通讯作者：
Kanatzidis, Mercouri G.
中科院分区：
文献类型：
--
作者：
Hodges, James M.;Hao, Shiqiang;Kanatzidis, Mercouri G.
热电发电机可以将热能直接转化为可用电能，但效率低，成本高，阻碍了广泛的应用。因此，热电领域的一个重要目标是开发由更多富含稀土元素组成的高性能新型材料。最好的中温发电系统依赖于重掺杂的PbTe，但这些材料中的Te在地壳中是稀缺的。PbSe正在成为一种成本更低的PbTe替代品，尽管由于功率因数S-2西格玛要小得多，它的性能较差，其中S是塞贝克系数，西格玛是电导率。在这里，我们提出了一种新的p型PbSe系统，Pb0.98Na0.02Se-x%HgSe，当x=2时，它在963K时产生了类似于20微瓦·厘米(-1)·K-2的非常高的功率因数，比性能最好的PbSe-x%MSe材料提高了15%。这一增强归因于高载流子迁移率和汞合金样品在550K附近提前开始能带收敛，从而导致Seebeck系数显著增加。有趣的是，我们发现Hg2+离子在PbSe晶格中处于偏心位置，我们将位移的汞原子称为“不协调的”。DFT计算表明，这一特性在降低热导率方面起到了作用，我们相信这一见解可能会启发工程设计高性能热电材料的新设计标准。高功率因数加上热导率的降低，使在970K时的优良系数ZT达到1.7，这是迄今为止报道的p型PbSe的最高值。
Thermoelectric generators can convert heat directly into usable electric power but suffer from low efficiencies and high costs, which have hindered wide-scale applications. Accordingly, an important goal in the field of thermoelectricity is to develop new high performance materials that are composed of more earth abundant elements. The best systems for midtemperature power generation rely on heavily doped PbTe, but the Te in these materials is scarce in the Earth's crust. PbSe is emerging as a less expensive alternative to PbTe, although it displays inferior performance due to a considerably smaller power factor S-2 sigma, where S is the Seebeck coefficient and sigma is electrical conductivity. Here, we present a new p-type PbSe system, Pb0.98Na0.02Se-x%HgSe, which yields a very high power factor of similar to 20 mu W.cm(-1).K-2 at 963 K when x = 2, a 15% improvement over the best performing PbSe-x%MSe materials. The enhancement is attributed to a combination of high carrier mobility and the early onset of band convergence in the Hg-alloyed samples similar to 550 K), which results in a significant increase in the Seebeck coefficient. Interestingly, we find that the Hg2+ cations sit at an off-centered position within the PbSe lattice, and we dub the displaced Hg atoms "discordant". DFT calculations indicate that this feature plays a role in lowering thermal conductivity, and we believe that this insight may inspire new design criteria for engineering high performance thermoelectric materials. The high power factor combined with a decrease in thermal conductivity gives a high figure of merit ZT of 1.7 at 970 K, the highest value reported for p-type PbSe to date.