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Direct Observation of Inherent Atomic‐Scale Defect Disorders responsible for High‐Performance Ti 1− x Hf x NiSn 1− y Sb y Half‐Heusler Thermoelectric Alloys
Author(s) -
Kim Ki Sung,
Kim YoungMin,
Mun Hyeona,
Kim Jisoo,
Park Jucheol,
Borisevich Albina Y.,
Lee Kyu Hyoung,
Kim Sung Wng
Publication year - 2017
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201702091
Subject(s) - materials science , atomic units , thermoelectric effect , alloy , thermoelectric materials , transmission electron microscopy , phonon , scanning transmission electron microscopy , thermal conductivity , condensed matter physics , metallurgy , nanotechnology , composite material , thermodynamics , physics , quantum mechanics
Structural defects often dominate the electronic‐ and thermal‐transport properties of thermoelectric (TE) materials and are thus a central ingredient for improving their performance. However, understanding the relationship between TE performance and the disordered atomic defects that are generally inherent in nanostructured alloys remains a challenge. Herein, the use of scanning transmission electron microscopy to visualize atomic defects directly is described and disordered atomic‐scale defects are demonstrated to be responsible for the enhancement of TE performance in nanostructured Ti 1− x Hf x NiSn 1− y Sb y half‐Heusler alloys. The disordered defects at all atomic sites induce a local composition fluctuation, effectively scattering phonons and improving the power factor. It is observed that the Ni interstitial and Ti,Hf/Sn antisite defects are collectively formed, leading to significant atomic disorder that causes the additional reduction of lattice thermal conductivity. The Ti 1− x Hf x NiSn 1− y Sb y alloys containing inherent atomic‐scale defect disorders are produced in one hour by a newly developed process of temperature‐regulated rapid solidification followed by sintering. The collective atomic‐scale defect disorder improves the zT to 1.09 ± 0.12 at 800 K for the Ti 0.5 Hf 0.5 NiSn 0.98 Sb 0.02 alloy. These results provide a promising avenue for improving the TE performance of state‐of‐the‐art materials.