Multiple Converged Conduction Bands in K2Bi8Se13: A Promising Thermoelectric Material with Extremely Low Thermal Conductivity

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• 作者：Yanling Pei ; Cheng Chang ; Zhe Wang ; Meijie Yin ; Minghui Wu ; Gangjian TanHaijun Wu ; Yuexing Chen ; Lei Zheng ; Shengkai Gong ; Tiejun Zhu ; Xinbing Zhao ; Li Huang ; Jiaqing He ; Mercouri G. Kanatzidis ; Li-Dong Zhao
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：December 21, 2016
• 年：2016
• 卷：138
• 期：50
• 页码：16364-16371
• 全文大小：661K
• ISSN：1520-5126

文摘

We report that K₂Bi₈Se₁₃ exhibits multiple conduction bands that lie close in energy and can be activated through doping, leading to a highly enhanced Seebeck coefficient and a high power factor with elevated temperature. Meanwhile, the large unit cell, complex low symmetry crystal structure, and nondirectional bonding lead to the very low lattice thermal conductivity of K₂Bi₈Se₁₃, ranging between 0.42 and 0.20 W m^–1 K^–1 in the temperature interval 300–873 K. Experimentally, we further support the low thermal conductivity of K₂Bi₈Se₁₃ using phonon velocity measurements; the results show a low average phonon velocity (1605 ms^–1), small Young’s modulus (37.1 GPa), large Grüneisen parameter (1.71), and low Debye temperature (154 K). A detailed investigation of the microstructure and defects was carried out using electron diffraction and transmission microscopy which reveal the presence of a K_2.5Bi_8.5Se₁₄ minor phase intergrown along the side of the K₂Bi₈Se₁₃ phase. The combination of enhanced power factor and low thermal conductivity results in a high ZT value of ∼1.3 at 873 K in electron doped K₂Bi₈Se₁₃ material.