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Changing the Band Gaps by Controlling the Distribution of Initial Particle Size to Improve the Power Factor of N‐Type Bi 2 Te 3 Based Polycrystalline Bulks
Author(s) -
Zhang Chengcheng,
Fan Xi An,
Hu Jie,
Jiang Chengpeng,
Xiang Qiusheng,
Li Guangqiang,
Li Yawei,
He Zhu
Publication year - 2017
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201600696
Subject(s) - materials science , seebeck coefficient , particle size distribution , particle size , particle (ecology) , grain size , grain boundary , sintering , electrical resistivity and conductivity , crystallite , band gap , microstructure , composite material , condensed matter physics , metallurgy , optoelectronics , thermal conductivity , chemical engineering , electrical engineering , oceanography , engineering , geology , physics
In this work, n‐type Bi 2 Te 2.7 Se 0.3 bulks are prepared by resistance pressure sintering technique from different particle sized powders, and the microstructure and electrical transport properties are investigated as function of the initial particle size distribution. With the initial particle size decreasing, more antisite defects, grain‐boundaries and interface defects are introduced, and lead to a larger carrier concentration due to donor‐like effect and a lower mobility due to the increasing grain boundary and carrier scattering, which results in a lower Seebeck coefficient and electrical resistivity. As a result, a maximum power factor of about 2.89 mW mK −2 at room temperature is achieved for the bulk sintered from the mix powders with different particle size distribution due to the optimization of the carrier concentration. The band gaps and the intrinsic excitation temperature are effectively adjusted by controlling the particle size in a narrow distribution. The sample sintered from the powders below 400 mesh has the highest average power factor above 2.44 mW mK −2 in the whole testing temperature range due to the improving band gaps and intrinsic excitation temperature.