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High Seebeck Coefficient and Unusually Low Thermal Conductivity Near Ambient Temperatures in Layered Compound Yb2–xEuxCdSb2
Chemistry of Materials ( IF 8.6 ) Pub Date : 2017-12-18 00:00:00 , DOI: 10.1021/acs.chemmater.7b04517
Joya A. Cooley 1 , Phichit Promkhan 1 , Shruba Gangopadhyay 1 , Davide Donadio 1, 2 , Warren E. Pickett 3 , Brenden R. Ortiz 4 , Eric S. Toberer 4 , Susan M. Kauzlarich 1
Affiliation  

Zintl phases are promising thermoelectric materials because they are composed of both ionic and covalent bonding, which can be independently tuned. An efficient thermoelectric material would have regions of the structure composed of a high-mobility compound semiconductor that provides the “electron–crystal” electronic structure, interwoven (on the atomic scale) with a phonon transport inhibiting structure to act as the “phonon–glass”. The phonon–glass region would benefit from disorder and therefore would be ideal to house dopants without disrupting the electron–crystal region. The solid solution of the Zintl phase, Yb2–xEuxCdSb2, presents such an optimal structure, and here we characterize its thermoelectric properties above room temperature. Thermoelectric property measurements from 348 to 523 K show high Seebeck values (maximum of ∼269 μV/K at 523 K) with exceptionally low thermal conductivity (minimum ∼0.26 W/m K at 473 K) measured via laser flash analysis. Speed of sound data provide additional support for the low thermal conductivity. Density functional theory (DFT) was employed to determine the electronic structure and transport properties of Yb2CdSb2 and YbEuCdSb2. Lanthanide compounds display an f-band well below (∼2 eV) the gap. This energy separation implies that f-orbitals are a silent player in thermoelectric properties; however, we find that some hybridization extends to the bottom of the gap and somewhat renormalizes hole carrier properties. Changes in the carrier concentration related to the introduction of Eu lead to higher resistivity. A zT of ∼0.67 at 523 K is demonstrated for Yb1.6Eu0.4CdSb2 due to its high Seebeck, moderate electrical resistivity, and very low thermal conductivity.

中文翻译:

层状化合物Yb 2– x Eu x CdSb 2中的高塞贝克系数和常温附近的异常低的热导率

Zintl相是有前途的热电材料,因为它们由离子键和共价键组成,可以独立调节。一种有效的热电材料将具有由高迁移率化合物半导体组成的结构区域,该区域提供“电子-晶体”电子结构,并与声子传输抑制结构交织在一起(在原子尺度上),从而起到“声子-玻璃”的作用。 ”。声子-玻璃区域将受益于无序,因此是容纳掺杂剂而不破坏电子晶体区域的理想选择。Zintl相的固溶体,Yb 2– x Eu x CdSb 2代表了这样的最佳结构,在这里我们描述了其在室温以上的热电特性。从348到523 K的热电性能测量显示出高塞贝克值(在523 K时最大值约为269μV/ K),而通过激光闪光分析测得的导热率极低(在473 K时最小值约为0.26 W / m K)。声音数据的速度为低导热率提供了额外的支持。密度泛函理论(DFT)用于确定Yb 2 CdSb 2和YbEuCdSb 2的电子结构和传输性质。镧系元素化合物的f带明显低于(〜2 eV)缝隙。这种能量分离意味着f轨道是热电性质的沉默参与者。但是,我们发现某些杂交扩展到了间隙的底部,并在某种程度上重新标准化了空穴载流子的性质。与引入Eu有关的载流子浓度的变化导致更高的电阻率。甲zT值在523的K ~0.67证明为镱1.6的Eu 0.4 CDSB 2由于它的高的Seebeck,中度电阻率,和非常低的热导率。
更新日期:2017-12-18
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