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Title: Ultralow thermal conductivity and high-temperature thermoelectric performance in n-type K₂.₅Bi₈.₅Se₁₄
Authors: Luo, Zhong-Zhen
Cai, Songting
Hao, Shiqiang
Bailey, Trevor P.
Hu, Xiaobing
Hanus, Riley
Ma, Runchu
Tan, Gangjian
Chica. Daniel G.
Snyder, G. Jeffrey
Uher, Ctirad
Wolverton, Christopher
Dravid, Vinayak P.
Yan, Qingyu
Kanatzidis, Mercouri G.
Keywords: Engineering::Materials::Functional materials
Issue Date: 2019
Source: Luo, Z., Cai, S., Hao, S., Bailey, T. P., Hu, X., Hanus, R., Ma, R., Tan, G., Chica. Daniel G., Snyder, G. J., Uher, C., Wolverton, C., Dravid, V. P., Yan, Q. & Kanatzidis, M. G. (2019). Ultralow thermal conductivity and high-temperature thermoelectric performance in n-type K₂.₅Bi₈.₅Se₁₄. Chemistry of Materials, 31(15), 5943-5952.
Project: MOE 2018-T2-1-010
MOE 2017-T2-2-069
SERC 1527200022
Journal: Chemistry of Materials
Abstract: We studied the narrow bandgap (0.55 eV) semiconductor K2.5Bi8.5Se14, as a potential thermoelectric material for power generation. Samples of polycrystalline K2.5Bi8.5Se14 prepared by spark plasma sintering exhibit exceptionally low lattice thermal conductivities (κlat) of 0.57 − 0.33 Wm−1K−1 in the temperature range of 300 − 873 K. The physical origin of such low κlat in K2.5Bi8.5Se14 is related to the strong anharmonicity and low phonon velocity caused by its complex low-symmetry, large unit cell crystal structure and mixed-occupancy of Bi and K atoms in the lattice. High-resolution scanning transmission electron microscopy (HRSTEM) studies and micro-analysis indicates that the K2.5Bi8.5Se14 sample is a single phase without intergrowth of the structurally related K2Bi8Se13 phase. The undoped material exhibits n-type character and a figure of merit (ZT) value of 0.67 at 873 K. Electronic band structure calculations indicate that K2.5Bi8.5Se14 is an indirect bandgap semiconductor with multiple conduction bands close to the Fermi level. Phonon dispersion calculations suggest K2.5Bi8.5Se14 has low phonon velocities and large Grüneisen parameters that can account for the observed ultralow κlat. The degree of n-type doping can be controlled by introducing Se deficiencies in the structure providing a simple route to increase the ZT to ~1 at 873 K.
ISSN: 0897-4756
DOI: 10.1021/acs.chemmater.9b02327
Rights: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:MSE Journal Articles

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