Open AccessLiquid‐Phase Hot Deformation to Enhance Thermoelectric Performance of n‐type Bismuth‐Telluride‐Based Solid Solutions
Author(s) -
Wu Yehao,
Yu Yuan,
Zhang Qi,
Zhu Tiejun,
Zhai Renshuang,
Zhao Xinbing
Publication year - 2019
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201901702
Subject(s) - materials science , bismuth telluride , thermoelectric effect , eutectic system , crystallite , electron mobility , thermoelectric materials , nucleation , deformation (meteorology) , thermal conductivity , composite material , condensed matter physics , alloy , metallurgy , optoelectronics , thermodynamics , physics
Bismuth‐telluride‐based solid solutions are the best commercial thermoelectric materials near room temperature. For their n‐type polycrystalline compounds, the maximum figures of merit ( zT s) are often less than 1.0 due to the degraded carrier mobility resulting from the loss of texture. Herein, a liquid‐phase hot deformation procedure, during which the Bi 2 (Te,Se) 3 ingots are directly hot deformed with the extrusion of liquid eutectic phase, is performed to enhance the thermoelectric performance of n‐type Bi 2 (Te,Se) 3 alloys. The deformation‐induced dynamic recrystallization is remarkably suppressed due to the reduction of nucleation sites and the release of deformation stress by liquid phase, contributing to a weakened carrier scattering and enhanced carrier mobility. The liquid eutectic phase also facilitates the rotation of grains and enhanced (000 l ) texture, further improving carrier mobility. In addition, the dense dislocations and lattice distortion introduced into the matrix reduce the lattice thermal conductivity. As a result, a high zT value of 1.1 at 400 K is obtained, about 75% increment over the normal one‐step hot deformed alloys. This work not only demonstrates a simple and efficient technique for achieving superior n‐type Bi 2 Te 3 ‐based materials, but also elucidates the important role of liquid eutectic phase in hot deformation.