Right sizes of nano- and microstructures for high-performance and rigid bulk thermoelectrics

Hongchao Wang, Yonsei University
Je-Hyeong Bahk, Birck Nanotechnology Center, Purdue University
Chanyoung Kang, Yonsei University
Junphil Hwang, Yonsei University
Kangmin Kim, Yonsei University
Jungwon Kim, Yonsei University
Peter Burke, University of California - Santa Barbara
John E. Bowers, University of California - Santa Barbara
Arthur C. Gossard, University of California - Santa Barbara
Ali Shakouri, University of California - Santa Cruz; Birck Nanotechnology Center, Purdue University
Woochul Kim, Yonsei University

Date of this Version



This is the Publisher PDF of Wang, H; Bahk, J-H; Kang, C; Hwang, J; Kim, K; Kim, J; Burke, P; Bowers, JE; Gossard, A; Shakouri, A; and Kim, W. "Right sizes of nano- and microstructures for high-performance and rigid bulk thermoelectrics." PNAS, 111:30, 10949-10954. 2014. Copyright National Academy of Sciences, available at http://dx.doi.org/10.1073/pnas.1403601111


In this paper, we systematically investigate three different routes of synthesizing 2% Na-doped PbTe after melting the elements: (i) quenching followed by hot-pressing (QH), (ii) annealing followed by hot-pressing, and (iii) quenching and annealing followed by hot-pressing. We found that the thermoelectric figure of merit, zT, strongly depends on the synthesis condition and that its value can be enhanced to similar to 2.0 at 773 K by optimizing the size distribution of the nanostructures in the material. Based on our theoretical analysis on both electron and thermal transport, this zT enhancement is attributed to the reduction of both the lattice and electronic thermal conductivities; the smallest sizes (2 similar to 6 nm) of nanostructures in the QH sample are responsible for effectively scattering the wide range of phonon wavelengths to minimize the lattice thermal conductivity to similar to 0.5 W/m K. The reduced electronic thermal conductivity associated with the suppressed electrical conductivity by nanostructures also helped reduce the total thermal conductivity. In addition to the high zT of the QH sample, the mechanical hardness is higher than the other samples by a factor of around 2 due to the smaller grain sizes. Overall, this paper suggests a guideline on how to achieve high zT and mechanical strength of a thermoelectric material by controlling nano-and microstructures of the material.


Nanoscience and Nanotechnology