Tuning the thermoelectric properties of polycrystalline FeSb 2 by the in situ formation of Sb/InSb nanoinclusions
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Wenjie Xie Wuhan University of Technology, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan 430070, HuBei, China
Daniel Thompson, Tim Holgate, and Menghan Zhou Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634
Yonggao Yan Wuhan University of Technology, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan 430070, HuBei, China
Terry M. Tritta) Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 (Received 5 January 2011; accepted 7 March 2011)
As a narrow gap, strongly correlated electron semiconductor, FeSb2 single crystals can exhibit a colossal thermopower1 (on the order of 40,000 lV/K or greater) and a relatively high lattice thermal conductivity2 (over 300 W/m-K) at temperatures around 10 K. In this work, a series of FeSb2 polycrystalline samples with different amounts of additional Indium were prepared by a quench-and-anneal method followed by a spark plasma sintering procedure. The x-ray diffraction, scanning electron microscopy, and elemental analysis verified that the Sb/InSb nanoinclusions were formed in situ on the boundaries of coarse FeSb2 grains. The presence of such nanoinclusions and other as-formed multiscale microstructures can scatter phonons and thus dramatically reduce the corresponding lattice thermal conductivity. Furthermore, the electrical properties can be also improved because of the addition of high mobility carriers from the InSb nanoinclusions. Overall, FeSb2-based materials have shown some promising potential for possible thermoelectric cooling applications at cryogenic temperatures.
I. INTRODUCTION
Address all correspondence to this author. e-mail: [email protected] This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/ DOI: 10.1557/jmr.2011.86
temperature, and thermal conductivity (including the lattice thermal conductivity jl and carrier thermal conductivity je), respectively. Although there is no known theoretical limit for the ZT value, TE materials with ZT , ;1 are still relatively rare and furthermore there are no practical useful TE materials that work at very low temperatures, especially in liquid nitrogen range (T , 77 K) to achieve solid state cooling for high temperature superconductors. In addition, very few candidate materials are even remotely available for further investigation of their properties and potential usage at these low cryogenic temperatures. As a narrow gap, strongly correlated electron semiconductor, FeSb2 single crystals are recently reported to exhibit a huge negative Seebeck coefficient ;45,000 lV/K and a record high power factor of 2300 lW/K2-cm at about 10 K, which is 65 times larger than the state-of-the-art Bi2Te3.1 This colossal Seebeck coefficient is possibly caused by the strong electron correlations among the 3d electrons of F
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