Sr9Mg4.45(1)Bi9 and Sr9Mg4.42(1)Sb9: Mg-Containing Zintl Phases with Low Thermal Conductivity
Sr9Mg4.45(1)Bi9 and Sr9Mg4.42(1)Sb9: Mg-Containing Zintl Phases with Low Thermal Conductivity
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Sr9Mg4.45(1)Bi9 和 Sr9Mg4.42(1)Sb9：低导热率含镁 Zintl 相
DOI：
10.1021/acs.inorgchem.1c00078
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发表时间：
2021
影响因子：
4.6
通讯作者：
Xia Sheng-Qing
中科院分区：
文献类型：
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作者：
Zhang Jian;Liu Qian;Liu Ke-Feng;Tan Wen-Jie;Liu Xiao-Cun;Xia Sheng-Qing
Zintl相的名义公式为9-4-9，它们作为热电材料的潜在应用是非常有趣的。然而，这种相的形成通常需要二价过渡金属，例如Zn、Mn和Cd，它们共价键合到磷属元素原子上。本文首次合成了Sr9Mg4.45（1）Bi 9和Sr9Mg4.42（1）Sb 9两种含镁化合物，并用X射线单晶衍射方法测定了它们的结构。两种标题化合物均属于正交晶系Pnma空间群，与Ca_9 Mn_（4.41）（1）Sb_9同构，与经典的9-4-9相相比，具有复杂的多阴离子结构。对于Sr9Mg4.45（1）Bi 9，其低热导率，结合其高电导率和适中的塞贝克系数，导致在773 K下0.57的良好品质因数，这显然在未优化的9-4-9相中占优势。这种含Mg的9-4-9相的发现是非常重要的，因为该发现不仅丰富了著名的9-4-9族的结构图，而且提供了非常有价值的热电候选物，肯定值得更深入的研究。
Zintl phases with nominal 9–4–9 formulas are very interesting for their potential applications as thermoelectric materials. However, the formation of such phases usually requires divalent transition metals, for example, Zn, Mn, and Cd, which are covalently bonded to the pnictogen atoms. In this report, for the first time, two Mg-containing compounds with such structures as Sr9Mg4.45(1)Bi9and Sr9Mg4.42(1)Sb9were synthesized and their structures were determined by the single-crystal X-ray diffraction method. Both title compounds crystallize in the orthorhombic space groupPnmaand are isostructural with Ca9Mn4.41(1)Sb9, which features complex polyanion structures compared to the classical 9–4–9 phases. For Sr9Mg4.45(1)Bi9, its low thermal conductivity, combined with its high electrical conductivity and moderate Seebeck coefficient, leads to a decent figure of merit of 0.57 at 773 K, which obviously prevails in the unoptimized 9–4–9 phases. The discovery of such Mg-containing 9–4–9 phases is very significant, as the discovery not only enriches the structure map of the well-known 9–4–9 family but also provides very valuable thermoelectric candidates surely deserving of more in-depth investigation.