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arXiv 2008.12015cond-mat.mtrl-sci
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Mg $_3$ Sb $_2$热电材料的n型镧系元素掺杂研究

Probing efficient n-type lanthanide dopants for Mg$_3$Sb$_2$ thermoelectrics

Jiawei Zhang, Lirong Song, Bo Brummerstedt Iversen

摘要:

最近发现的n型Mg $_3$ Sb $_2$热电材料引发了广泛的研究活动,寻找潜在的n型掺杂剂,这种材料。使用第一性原理缺陷计算,在这里,我们进行了系统的计算筛选潜在的有效的n型镧系元素掺杂剂的Mg $_3$ Sb $_2$。除了La,Ce,Pr,和Tm,我们发现,高电子浓度($\geq$ 10 $^{20}$ cm $^{-3}$在900 K的生长温度)可以通过在Mg位点上掺杂Nd,Gd,Ho和Lu来实现,这通常比其他镧系元素掺杂剂和阴离子位点掺杂剂Te更有效。实验上,我们确认Nd和Tm作为Mg $_3$ Sb $_2$的有效n型掺杂剂,因为用Nd和Tm掺杂显示出具有比用Te掺杂更高的电子浓度的优异热电优值zT $\geq$ 1.3。通过Nd(Tm)和Te的共掺杂,实现了功率因数的同时提高和热导率的降低。结果,在775 K下,我们在n型Mg $_{3.5}$ Nd $_{0.04}$ Sb $_{1.97}$ Te $_{0.03}$和Mg $_{3.5}$ Tm $_{0.03}$ Sb $_{1.97}$ Te $_{0.03}$,分别,这是在没有与Mg $_3$合金化的n型Mg $_3$ Sb $_2$中的最高值双PDMATHAMN。这项工作揭示了探索有前途的n型掺杂剂的Mg $_3$ Sb $_2$热电设计。

英文摘要:

The recent discovery of n-type Mg$_3$Sb$_2$ thermoelectric has ignited intensive research activities on searching for potential n-type dopants for this material. Using first-principles defect calculations, here we conduct a systematic computational screening of potential efficient n-type lanthanide dopants for Mg$_3$Sb$_2$. In addition to La, Ce, Pr, and Tm, we find that high electron concentration ($\geq$ 10$^{20}$ cm$^{-3}$ at the growth temperature of 900 K) can be achieved by doping on the Mg sites with Nd, Gd, Ho, and Lu, which are generally more efficient than other lanthanide dopants and the anion-site dopant Te. Experimentally, we confirm Nd and Tm as effective n-type dopants for Mg$_3$Sb$_2$ since doping with Nd and Tm shows superior thermoelectric figure of merit zT $\geq$ 1.3 with higher electron concentration than doping with Te. Through codoping with Nd (Tm) and Te, simultaneous power factor improvement and thermal conductivity reduction are achieved. As a result, we obtain high zT values of about 1.65 and 1.75 at 775 K in n-type Mg$_{3.5}$Nd$_{0.04}$Sb$_{1.97}$Te$_{0.03}$ and Mg$_{3.5}$Tm$_{0.03}$Sb$_{1.97}$Te$_{0.03}$, respectively, which are among the highest values for n-type Mg$_3$Sb$_2$ without alloying with Mg$_3$Bi$_2$. This work sheds light on exploring promising n-type dopants for the design of Mg$_3$Sb$_2$ thermoelectrics.

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