The impact of site selectivity and disorder on the thermoelectric properties of Yb 21 Mn 4 Sb 18 solid solutions: Yb 21 Mn 4−x Cd x Sb 18 and Yb 21−y Ca y Mn 4 Sb 18
The impact of site selectivity and disorder on the thermoelectric properties of Yb 21 Mn 4 Sb 18 solid solutions: Yb 21 Mn 4−x Cd x Sb 18 and Yb 21−y Ca y Mn 4 Sb 18
复制标题
位点选择性和无序性对Yb 21 Mn 4 Sb 18 固溶体热电性能的影响：Yb 21 Mn 4→x Cd x Sb 18 和 Yb 21→y Ca y Mn 4 Sb 18
DOI：
10.1039/d1ma00497b
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发表时间：
2021
影响因子：
5
通讯作者：
Kauzlarich, Susan M.
中科院分区：
文献类型：
--
作者：
He, Allan;Cerretti, Giacomo;Kauzlarich, Susan M.
热电材料能把热转换成电。它们用于在其他电源不可用时发电，或通过回收废热来提高能源效率。Yb 21 Mn 4Sb 18相之前被证明具有良好的热电性能，因为它具有大的塞贝克系数（约290 μV K−1）和低的热导率（0.4 W m−1 K−1）。这些特征分别源于独特的[Mn 4Sb 10]22−亚基和该相固有的大单位晶胞/位点无序。制备了Yb 21 Mn 4 − xCdxSb 18（x = 0，0.5，1.0，1.5）和Yb 21 − yCayMn 4Sb 18（y = 3，6，9，10.5）固溶体，表征了它们的结构，测量了它们从室温到800 K的热电性能。的Cd和Ca的固溶体的结构紊乱进行了详细的研究，使用同步辐射粉末X射线衍射和对分布函数方法，并表明，这些是高度无序的结构。Cd的取代引起更多的金属行为，而Ca取代导致高电阻率。由于Cd和Ca都是等电子取代，性质的变化归因于电子结构的变化。这两种固溶体都显示出热导率仍然非常低（<0.4 W m−1 K−1），塞贝克系数仍然很高（>200 μV K−1）。随着Ca取代的增加，载流子迁移率的温度依赖性从大约T−1变化到T−0.5，表明引入了另一种散射机制。随着键合从与Yb的极性共价键变为与Ca的离子键，极性光学声子散射成为主导机制。Cd固溶体的实验研究结果表明，在800 K时，最大zT为10.1，更重要的是，从300 K到800 K，ZTavg为0.6。
Thermoelectric materials can convert heat into electricity. They are used to generate electricity when other power sources are not available or to increase energy efficiency by recycling waste heat. The Yb21Mn4Sb18 phase was previously shown to have good thermoelectric performance due to its large Seebeck coefficient (∼290 μV K−1) and low thermal conductivity (0.4 W m−1 K−1). These characteristics stem respectively from the unique [Mn4Sb10]22− subunit and the large unit cell/site disorder inherent in this phase. The solid solutions, Yb21Mn4−xCdxSb18 (x = 0, 0.5, 1.0, 1.5) and Yb21−yCayMn4Sb18 (y = 3, 6, 9, 10.5) have been prepared, their structures characterized and thermoelectric properties from room temperature to 800 K measured. A detailed look into the structural disorder for the Cd and Ca solid solutions was performed using synchrotron powder X-ray diffraction and pair distribution function methods and shows that these are highly disordered structures. The substitution of Cd gives rise to more metallic behavior whereas Ca substitution results in high resistivity. As both Cd and Ca are isoelectronic substitutions, the changes in properties are attributed to changes in the electronic structure. Both solid solutions show that the thermal conductivities remain extremely low (∼0.4 W m−1 K−1) and that the Seebeck coefficients remain high (>200 μV K−1). The temperature dependence of the carrier mobility with increased Ca substitution, changing from approximately T−1 to T−0.5, suggests that another scattering mechanism is being introduced. As the bonding changes from polar covalent with Yb to ionic for Ca, polar optical phonon scattering becomes the dominant mechanism. Experimental studies of the Cd solid solutions result in a max zT of ∼1 at 800 K and, more importantly for application purposes, a ZTavg ∼ 0.6 from 300 K to 800 K.