Origin of the High Performance in GeTe-Based Thermoelectric Materials upon Bi2Te3 Doping

详细信息    查看全文

• 作者：Di Wu ; Li-Dong Zhao ; Shiqiang Hao ; Qike Jiang ; Fengshan Zheng ; Jeff W. Doak ; Haijun Wu ; Hang Chi ; Y. Gelbstein ; C. Uher ; C. Wolverton ; Mercouri Kanatzidis ; Jiaqing He
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：August 13, 2014
• 年：2014
• 卷：136
• 期：32
• 页码：11412-11419
• 全文大小：533K
• ISSN：1520-5126

文摘

As a lead-free material, GeTe has drawn growing attention in thermoelectrics, and a figure of merit (ZT) close to unity was previously obtained via traditional doping/alloying, largely through hole carrier concentration tuning. In this report, we show that a remarkably high ZT of 1.9 can be achieved at 773 K in Ge_0.87Pb_0.13Te upon the introduction of 3 mol % Bi₂Te₃. Bismuth telluride promotes the solubility of PbTe in the GeTe matrix, thus leading to a significantly reduced thermal conductivity. At the same time, it enhances the thermopower by activating a much higher fraction of charge transport from the highly degenerate 危 valence band, as evidenced by density functional theory calculations. These mechanisms are incorporated and discussed in a three-band (L + 危 + C) model and are found to explain the experimental results well. Analysis of the detailed microstructure (including rhombohedral twin structures) in Ge_0.87Pb_0.13Te + 3 mol % Bi₂Te₃ was carried out using transmission electron microscopy and crystallographic group theory. The complex microstructure explains the reduced lattice thermal conductivity and electrical conductivity as well.