The importance of the Mg–Mg interaction in Mg3Sb2–Mg3Bi2 shown through cation site alloying†,Journal of Materials Chemistry A

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The importance of the Mg–Mg interaction in Mg3Sb2–Mg3Bi2 shown through cation site alloying†
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2019-12-23 , DOI: 10.1039/c9ta11328b
Max Wood _{1,

2,

3,

4} , Kazuki Imasato _{1,

2,

3,

4} , Shashwat Anand _{1,

2,

3,

4} , Jiong Yang _{5,

6,

7,

8} , G. Jeffrey Snyder _{1,

2,

3,

4}

Affiliation

Herein we study the effect alloying Yb onto the octahedral cite of Te doped Mg₃Sb_1.5Bi_0.5 has on transport and the material's high temperature stability. We show that the reduction in mobility can be well explained with an alloy scattering argument due to disrupting the Mg_octahedral–Mg_tetrahedral interaction that is important for placing the conduction band minimum at a location with high valley degeneracy. We note this interaction likely dominates the conducting states across n-type Mg₃Sb₂–Mg₃Bi₂ solid solutions and explains why alloying on the anion site with Bi isn't detrimental to Mg₃Sb₂'s mobility. In addition to disrupting this Mg–Mg interaction, we find that alloying Yb into the Mg₃Sb₂ structure reduces its n-type dopability, likely originating from a change in the octahedral site's vacancy formation energy. We conclude showing that while the material's figure of merit is reduced with the addition of Yb alloying, its high temperature stability is greatly improved. This study demonstrates a site-specific alloying effect that will be important in other complex thermoelectric semiconductors such as Zintl phases.

中文翻译：

通过阳离子位点合金化显示了Mg ₃ Sb ₂ –Mg ₃ Bi ₂中Mg–Mg相互作用的重要性†

本文中，我们研究了将Yb合金化到Te掺杂Mg ₃ Sb _1.5 Bi _0.5的八面体上对运输和材料的高温稳定性的影响。我们表明，在迁移率的降低可以很好地用合金散射参数由于扰乱了Mg的解释_八面体-Mg_四面体相互作用是用于将导带最小值处具有高谷简并的位置很重要。我们注意到，这种相互作用可能会主导n型Mg ₃ Sb ₂ –Mg ₃ Bi ₂固溶体的导电状态，并解释了为什么与Bi一起在阴离子位点上形成合金不会损害Mg ₃Sb ₂的移动性。除了破坏这种Mg-Mg相互作用之外，我们发现将Yb合金化到Mg ₃ Sb ₂结构中会降低其n型掺杂性，这很可能是由于八面体位点的空位形成能发生变化而引起的。我们得出的结论表明，尽管通过添加Yb合金降低了材料的品质因数，但其高温稳定性却大大提高了。这项研究表明了特定位置的合金化作用，这在诸如Zintl相之类的其他复杂热电半导体中将非常重要。

更新日期：2020-01-07

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