材料科学
热电效应
热电材料
凝聚态物理
电阻率和电导率
带隙
热导率
微观结构
态密度
固溶体
热力学
冶金
复合材料
光电子学
工程类
物理
电气工程
作者
Gerda Rogl,Kunio Yubuta,V.V. Romaka,H. Michor,Erhard Schafler,A. Grytsiv,E. Bauer,P. Rogl
标识
DOI:10.1016/j.actamat.2018.12.042
摘要
With a small gap in the density of states and a substantially semiconducting behavior half Heusler alloys have drawn attention as thermoelectric materials. For this study we have selected Hf-free compounds, Ti0.5Zr0.5NiSn, Ti0.5Zr0.5NiSn (with a densification aid (DA)) and Ti0.5Zr0.5NiSn0.98Sb0.02 as well their parent alloys TiNiSn and ZrNiSn as cheap thermoelectrics. Electrical resistivity, thermal conductivity and specific heat were evaluated below room temperature (4.2–300 K) in order to get insight into the mechanism of transport properties. SEM and TEM investigations as well as DFT (density functional theory) calculations accompany this research. The fine-grained epitaxial microstructure with a large number of dislocations warrants a low thermal conductivity at ultralow values (∼30 mW/cmK at 300 K) at a narrow band gap with a sufficiently high density of states at the Femi level. High order of components mixing strongly affects the stability of the solid solutions by the configuration entropy term, which causes a shrinkage of the miscibility gap. For the electronic density of states (DOS) the split Zr band and impurity Ni band induce a significant reduction of the effective energy gap and thus explain n-type of conductivity of the compounds and solid solutions studied.
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