The p-n conduction type transition in Ge-incorporated Bi₂Te₃ thermoelectric materials

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• 作者：Hsin-jay Wu ; ^{ssky0211@mail.nsysu.edu.tw" class="auth_mail" title="E-mail the corresponding author} ; Bo-Yu Chen ; Hao-Yen Cheng
• 关键词：Thermoelectric materials ; Bi2Te3 ; Isothermal section ; zT ; p-n transition
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：1 January 2017
• 年：2017
• 卷：122
• 期：Complete
• 页码：120-129
• 全文大小：3609 K

文摘

The capability of converting waste heat into electricity characterizes the technology of thermoelectricity as a feasible solution in dealing with the energy issue. The Bi₂Te₃-based alloys have long been in the spotlight as they show promising zTs and high thermal stability near the room-temperature region. Herein, the experimentally determined 523 K isothermal section of ternary Bi-Ge-Te system concludes that the four ternary compounds, the Ge₃Bi₂Te₆, the Ge_1.5Bi_1.5Te₅, the Ge₁Bi₂Te₄ and the Ge₁Bi₄Te₇, are thermally stabilized and the solubility of Ge in Bi₂Te₃ could reach ∼5.0 at.%Ge. The thermoelectric performance of various Ge-incorporated Bi₂Te₃ alloys with compositions of Bi_40-yGe_xTe_60-x+y (x = 0–12.5, y = 0–10.0) are evaluated within 300 K-650 K. The conduction type of those alloys transits from p-type, for the un-doped Bi₂Te₃, to n-type semiconducting as one of the following conditions are satisfied: (1) the concentration of Te drops to less than 60.0 at.%, or (2) the concentration of Te exceeds 60.0 at.% and the ratios of Ge/Bi is larger than 0.2. The zT peak values reach zT∼0.9 at 325 K for p-type alloy P2 (Bi_39.0Ge_1.0Te_60.0), which features a Bi₂Te₃ single-phase microstructure, and zT∼0.45 at 525 K for n-type alloy N5 (Bi_32.5Ge₁₀Te_57.5), which falls in a Bi₂Te₃+Ge₁Bi₂Te₄+Te three-phase region, respectively.