期刊
JOURNAL OF ALLOYS AND COMPOUNDS
卷 727, 期 -, 页码 1067-1075出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2017.08.166
关键词
Thermoelectric power factor; Ternary alloy; Bi-Sb-Te; Bi-Te-Se; Density functional theory; Doping
资金
- Korea Institute of Energy Technology Evaluation and Planning (KETEP)
- Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea [20162000000910]
- Korea Electrotechnology Research Institute (KERI) Primary research program through the National Research Council of Science & Technology (NST) - Ministry of Science, ICT and Future Planning (MSIP) [17-12-N0101-38]
- Korea Evaluation Institute of Industrial Technology (KEIT) [20162000000910, 17-12-N0101-38] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
The Bi2Te3-related binary compounds (Bi2Te3, Sb2Te3, Bi2Se3, and Sb2Se3) and ternary alloys [(Bi1-xSbx) Te-2(3)(BST, 0 <= x <= 1) and Bi-2(Te1-ySey)(3) (BTSe, 0 <= y <= 1)] are known as the high performance room temperature thermoelectric materials. Here, for the first time, we systematically study the thermoelectric transport properties of BST and BTSe alloys by calculating their thermoelectric power factor (PF) as a function of alloy composition ratio x and y, carrier concentration n, and the absolute temperature T. The band valley degeneracy and the band gap are critical to determine the thermoelectric transport properties of ternaries. We find that PFs of p-type BST are comparable to those of binaries, while those of n-type BTSe are not, due to the band structure similarity. And the p-type BST performances are superior to the n-type BTSe due to the longer carrier relaxation time, transport anisotropy, and the band valley degeneracy. We also find that the optimal carrier concentrations which maximize the PFs (n(opt)) depend on the ternary composition and the transport direction. The bipolar effect is found to be less significant for n-type BTSe due to the large band gap and the large nopt. For p-type poly-crystalline BST, the nopt is between 3 and 4 x 10(19) cm(-3) and it is achievable by Sb alloying and controlling the concentration of intrinsic defect. However, for n-type polycrystalline BTSe, nopt is ranging between 6 x 10(19) cm(-3) and 1 x 10(20) cm(-3) and thereby we need additional extrinsic dopant beyond Se alloying. The defect formation energy calculations reveal that Cl, Br, and I impurities are potential candidates for n-type carrier sources without forming any compensating defect, while F as well as Au is the compensating defect. (C) 2017 Elsevier B.V. All rights reserved.
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