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Metallic n‐Type Mg 3 Sb 2 Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance
Author(s) -
Imasato Kazuki,
Fu Chenguang,
Pan Yu,
Wood Max,
Kuo Jimmy Jiahong,
Felser Claudia,
Snyder G. Jeffrey
Publication year - 2020
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.201908218
Subject(s) - thermoelectric effect , materials science , grain boundary , condensed matter physics , phonon scattering , impurity , charge carrier , carrier scattering , scattering , crystallite , electron mobility , doping , electrical resistivity and conductivity , thermoelectric materials , ionized impurity scattering , annealing (glass) , single crystal , semiconductor , crystallography , optoelectronics , thermal conductivity , metallurgy , microstructure , optics , composite material , thermodynamics , chemistry , physics , organic chemistry , quantum mechanics
Mg 3 (Sb,Bi) 2 alloys have recently been discovered as a competitive alternative to the state‐of‐the‐art n‐type Bi 2 (Te,Se) 3 thermoelectric alloys. Previous theoretical studies predict that single crystals Mg 3 (Sb,Bi) 2 can exhibit higher thermoelectric performance near room temperature by eliminating grain boundary resistance. However, the intrinsic Mg defect chemistry makes it challenging to grow n‐type Mg 3 (Sb,Bi) 2 single crystals. Here, the first thermoelectric properties of n‐type Te‐doped Mg 3 Sb 2 single crystals, synthesized by a combination of Sb‐flux method and Mg‐vapor annealing, is reported. The electrical conductivity and carrier mobility of single crystals exhibit a metallic behavior with a typical T −1.5 dependence, indicating that phonon scattering dominates the charge carrier transport. The absence of any evidence of ionized impurity scattering in Te‐doped Mg 3 Sb 2 single crystals proves that the thermally activated mobility previously observed in polycrystalline materials is caused by grain boundary resistance. Eliminating this grain boundary resistance in the single crystals results in a large enhancement of the weighted mobility and figure of merit zT by more than 100% near room temperature. This work experimentally demonstrates the accurate understanding of charge‐carrier scattering is crucial for developing high‐performance thermoelectric materials and indicates that single‐crystalline Mg 3 (Sb,Bi) 2 solid solutions can exhibit higher zT compared to polycrystalline samples.