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New Opportunities in Existing Thermoelectric Materials: Grain Boundary Engineering in Pulverized p-Bi2Te3 System

Published online by Cambridge University Press:  01 February 2011

Jian He ,
Xiaohua Ji ,
Zhe Su ,
Nick Gothard ,
Justine Edwards  and
Terry M. Tritt
Jian He
Affiliation:
jianhe@clemson.edu, Clemson University, Physics and Astronomy, Kinard Lab of Physics, Clemson, SC, 29634, United States, 864 656 7597
Xiaohua Ji
Affiliation:
xiaohji@clemson.edu, Clemson University, Department of Physics and Astronomy, Clemson, SC, 29634, United States
Zhe Su
Affiliation:
zsu@clemson.edu, Clemson University, Department of Physics and Astronomy, Clemson, SC, 29634, United States
Nick Gothard
Affiliation:
gothard@clemson.edu, Clemson University, Department of Physics and Astronomy, Clemson, SC, 29634, United States
Justine Edwards
Affiliation:
gothard@clemson.edu, Clemson University, Department of Physics and Astronomy, Clemson, SC, 29634, United States
Terry M. Tritt
Affiliation:
justina@clemson.edu, Clemson University, Department of Physics and Astronomy, Clemson, SC, 29634, United States
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Abstract

Grain boundary scattering provides an effective avenue to lower the thermal conductivity in polycrystalline thermoelectric materials, but it is hard to do this without simultaneously degrading the power factor that is the product of electrical conductivity and thermopower. An immediate question arises as to whether one can fabricate a thermoelectrically favorable grain boundary?

In this paper we present a proof-of-principle grain boundary engineering study in the pulverized p-Bi2Te3 system. Utilizing the lately developed hydrothermal nano-coating technique, we fabricated an Alkali-metal(s)-containing surface layer with few tens of nm thick on the p-Bi2Te3 bulk reference grain, where it becomes part of the grain boundary upon hotpressing densification. The electrical resistivity, thermopower, thermal conductivity and Hall coefficient measurements constitute solid evidence that this heterogeneous layer helps decouple the otherwise inter-related resistivity, thermopower and thermal conductivity. To optimize the figure of merit ZT, we carefully varied the ratio between Na, K and Rb concentrations. It was found that the sample treated in the solution with Na/Rb =1:2 achieved a ZT comparable with that of the commercial ingot; in the mean time, the compatibility factor and robustness of device were considerably improved. In principle this technique can be applied to other existing polycrystalline thermoelectric materials as a new “tuning knob”.

Keywords

thermoelectricityhydrothermalBi
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1044: Symposium U – Thermoelectric Power Generation , 2007 , 1044-U02-01
Copyright
Copyright © Materials Research Society 2008

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References

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