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Materials (Basel). 2017 Jul 6;10(7). pii: E763. doi: 10.3390/ma10070763.

Effect of Substitutional Pb Doping on Bipolar and Lattice Thermal Conductivity in p-Type Bi0.48Sb1.52Te₃.

Author information

1
Materials R&D Center, Samsung Advanced Institute of Technology, Samsung Electronics, Suwon 16419, Korea. projet.special@gmail.com.
2
Department of Nano Applied Engineering, Kangwon National University, Chuncheon 24341, Korea. roh5397@gmail.com.
3
Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea. khlee2014@kangwon.ac.kr.
4
Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea. srw321@uos.ac.kr.
5
Materials R&D Center, Samsung Advanced Institute of Technology, Samsung Electronics, Suwon 16419, Korea. schne92@uos.ac.kr.
6
Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea. sang1.kim@uos.ac.kr.
7
Department of Energy Science, Sungkunkwan University, Suwon 16419, Korea. kimsungwng@skku.edu.

Abstract

Cation substitutional doping is an effective approach to modifying the electronic and thermal transports in Bi₂Te₃-based thermoelectric alloys. Here we present a comprehensive analysis of the electrical and thermal conductivities of polycrystalline Pb-doped p-type bulk Bi0.48Sb1.52Te₃. Pb doping significantly increased the electrical conductivity up to ~2700 S/cm at x = 0.02 in Bi0.48-xPbxSb1.52Te₃ due to the increase in hole carrier concentration. Even though the total thermal conductivity increased as Pb was added, due to the increased hole carrier concentration, the thermal conductivity was reduced by 14-22% if the contribution of the increased hole carrier concentration was excluded. To further understand the origin of reduction in the thermal conductivity, we first estimated the contribution of bipolar conduction to thermal conductivity from a two-parabolic band model, which is an extension of the single parabolic band model. Thereafter, the contribution of additional point defect scattering caused by Pb substitution (Pb in the cation site) was analyzed using the Debye-Callaway model. We found that Pb doping significantly suppressed both the bipolar thermal conduction and lattice thermal conductivity simultaneously, while the bipolar contribution to the total thermal conductivity reduction increased at high temperatures. At Pb doping of x = 0.02, the bipolar thermal conductivity decreased by ~30% from 0.47 W/mK to 0.33 W/mK at 480 K, which accounts for 70% of the total reduction.

KEYWORDS:

bipolar conduction; bismuth telluride; lattice thermal conductivity; thermoelectrics

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