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Realizing zT of 2.3 in Ge 1− x − y Sb x In y Te via Reducing the Phase‐Transition Temperature and Introducing Resonant Energy Doping
Author(s) -
Hong Min,
Chen ZhiGang,
Yang Lei,
Zou YiChao,
Dargusch Matthew S.,
Wang Hao,
Zou Jin
Publication year - 2018
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.201705942
Subject(s) - materials science , thermoelectric effect , condensed matter physics , grain boundary , thermoelectric materials , thermal conductivity , figure of merit , phonon , valence (chemistry) , doping , crystallographic defect , optoelectronics , microstructure , thermodynamics , physics , quantum mechanics , metallurgy , composite material
GeTe with rhombohedral‐to‐cubic phase transition is a promising lead‐free thermoelectric candidate. Herein, theoretical studies reveal that cubic GeTe has superior thermoelectric behavior, which is linked to (1) the two valence bands to enhance the electronic transport coefficients and (2) stronger enharmonic phonon–phonon interactions to ensure a lower intrinsic thermal conductivity. Experimentally, based on Ge 1− x Sb x Te with optimized carrier concentration, a record‐high figure‐of‐merit of 2.3 is achieved via further doping with In, which induces the distortion of the density of states near the Fermi level. Moreover, Sb and In codoping reduces the phase‐transition temperature to extend the better thermoelectric behavior of cubic GeTe to low temperature. Additionally, electronic microscopy characterization demonstrates grain boundaries, a high‐density of stacking faults, and nanoscale precipitates, which together with the inevitable point defects result in a dramatically decreased thermal conductivity. The fundamental investigation and experimental demonstration provide an important direction for the development of high‐performance Pb‐free thermoelectric materials.