Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 111, Issue 30, Pages 10949-10954Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1403601111
Keywords
waste heat recovery; energy harvesting
Categories
Funding
- Mid-career Researcher Program [2011-0028729]
- Nano-Material Technology Development Program (Green Nano Technology Development Program) through a National Research Foundation of Korea - Ministry of Education, Science and Technology [2011-0030146]
- Energy Efficiency and Resources Program of the Korea Institute of Energy Technology Evaluation and Planning Grant
- Korean Government Ministry of Knowledge Economy [20112010100100]
- Center for Energy Efficient Materials
- Energy Frontier Research Center
- US Department of Energy, Office of Basic Energy Sciences [DE-SC0001009]
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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.
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