凝聚态物理
材料科学
塞贝克系数
热电效应
有效质量(弹簧-质量系统)
兴奋剂
密度泛函理论
休斯勒化合物
费米能级
电阻率和电导率
电子迁移率
电子能带结构
费米能量
态密度
热导率
电子结构
电子
化学
计算化学
物理
热力学
量子力学
复合材料
作者
Zhang Ju,Yuanxu Wang,Shiqi Zhong,San-Huang Ke
出处
期刊:ACS applied energy materials
[American Chemical Society]
日期:2023-01-05
卷期号:6 (2): 714-722
被引量:3
标识
DOI:10.1021/acsaem.2c02849
摘要
Lately, the nominal 19-electron half-Heusler compound NbCoSb, historically viewed as a metal, has attracted reacquaintance and widespread attention because of its unexpected high thermoelectric (TE) performance. Here, the electronic structures of NbxCo1–yNiySb (x = 0.8, 1; y = 0, 0.1) have been systematically investigated by using the first-principles method and semiclassical Boltzmann transport theory. We demonstrate that Ni doping at Co sites in NbCoSb with 20% intrinsic Nb vacancies (Nb0.8CoSb) leads to a large band degeneracy, and the conduction band edge are mainly provided by the d-orbitals of the Ni, Co, and Nb atoms. The relative localization of the d orbitals not only remarkably increased the density-of-states effective mass near the Fermi energy but also retained a high mobility, which resulted in an optimal electrical conductivity without significant reduction of the Seebeck coefficient (∼−411.08 μV K –1 at 800 K) and thereby a large power factor. Meanwhile, Ni doping still preserved a low lattice thermal conductivity. As a result, a peak zT of 1.18 was achieved at 1100 K in the compound Nb0.8Co0.9Ni0.1Sb with a carrier concentration of 4.35 × 1020 cm–3. The present work identifies that Ni doping is an effective method to improve the TE properties of nominally 19-electron NbCoSb compounds with Nb vacancies and demonstrates the great potential for searching of nonstoichiometric 19-electron half-Heusler compounds with vacancies.
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