Luo Zhong-Zhen, Cai Songting, Hao Shiqiang, Bailey Trevor P, Su Xianli, Spanopoulos Ioannis, Hadar Ido, Tan Gangjian, Luo Yubo, Xu Jianwei, Uher Ctirad, Wolverton Christopher, Dravid Vinayak P, Yan Qingyu, Kanatzidis Mercouri G
School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore.
Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States.
J Am Chem Soc. 2019 Oct 9;141(40):16169-16177. doi: 10.1021/jacs.9b09249. Epub 2019 Sep 26.
PbTe-based thermoelectric materials are some of the most promising for converting heat into electricity, but their n-type versions still lag in performance the p-type ones. Here, we introduce midgap states and nanoscale precipitates using Ga-doping and GeTe-alloying to considerably improve the performance of n-type PbTe. The GeTe alloying significantly enlarges the energy band gap of PbTe and subsequent Ga doping introduces special midgap states that lead to an increased density of states (DOS) effective mass and enhanced Seebeck coefficients. Moreover, the nucleated GaTe nanoscale precipitates and off-center discordant Ge atoms in the PbTe matrix cause intense phonon scattering, strongly reducing the thermal conductivity (∼0.65 W m K at 623 K). As a result, a high room-temperature thermoelectric figure of merit ZT ∼ 0.59 and a peak ZT of ∼1.47 at 673 K were obtained for the PbGaTe-5%GeTe. The ZT value that is most relevant for devices is ∼1.27 from 400 to 773 K, the highest recorded value for n-type PbTe.
基于PbTe的热电材料是将热能转化为电能最具潜力的材料之一，但其n型版本的性能仍落后于p型。在此，我们通过Ga掺杂和GeTe合金化引入中间能隙态和纳米级沉淀物，以显著提高n型PbTe的性能。GeTe合金化显著扩大了PbTe的能带隙，随后的Ga掺杂引入了特殊的中间能隙态，导致态密度（DOS）有效质量增加和塞贝克系数增强。此外，在PbTe基体中形成的GaTe纳米级沉淀物和偏心不协调的Ge原子引起强烈的声子散射，大大降低了热导率（在623 K时约为0.65 W m K）。结果，对于PbGaTe-5%GeTe，在室温下获得了高达约0.59的热电优值ZT，在673 K时峰值ZT约为1.47。对于器件而言，最相关的ZT值在400至773 K范围内约为1.27，这是n型PbTe记录的最高值。
