High thermoelectric figure of merit in nanostructured p-type PbTe-MTe (M = Ca, Ba)

Kanishka Biswas, Jiaqing He, Guoyu Wang, Shih Han Lo, Ctirad Uher, Vinayak P. Dravid, Mercouri G Kanatzidis

Research output: Contribution to journalArticle

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Abstract

We demonstrate that by endotaxially embedding nanocrystals of the alkaline earth tellurides CaTe or BaTe in PbTe doped with Na 2Te heat carrying phonons can be strongly scattered with little effect on the power factor. An intriguing observation is that the insertion of CaTe in PbTe increases the solubility of Na 2Te, thereby allowing high levels of carrier concentration. Powder X-ray diffraction patterns reveal that all samples crystallize in the NaCl-type structure without noticeable secondary phase, while scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) demonstrate the presence of endotaxially coherent/semi-coherent nanostructures in the PbTe-CaTe/BaTe samples. We show that this is the principal factor for the very low thermal conductivity. Electron energy loss spectroscopy (EELS) confirms the presence of Ca in the nanoprecipitates. We present a comparison in the lattice thermal conductivity in going from nanocrystals of CaTe to SrTe to BaTe in PbTe. Temperature dependent Hall coefficient measurements of PbTe-CaTe materials suggest that the carrier population in the so-called heavy hole valence band in PbTe becomes important above 450 K and is responsible for the high power factors. The highest thermoelectric figure of merit, ZT, value achieved is ∼1.5 at 765 K for 6% CaTe containing sample, while 3% BaTe containing sample shows the ZT of ∼1.3 at 760 K.

Original languageEnglish
Pages (from-to)4675-4684
Number of pages10
JournalEnergy and Environmental Science
Volume4
Issue number11
DOIs
Publication statusPublished - Nov 2011

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thermal conductivity
Nanocrystals
transmission electron microscopy
Thermal conductivity
Transmission electron microscopy
telluride
Electron energy loss spectroscopy
Phonons
Valence bands
Crystal lattices
Diffraction patterns
Carrier concentration
Nanostructures
solubility
Solubility
Earth (planet)
scanning electron microscopy
spectroscopy
X-ray diffraction
Powders

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Environmental Chemistry
  • Pollution
  • Nuclear Energy and Engineering

Cite this

High thermoelectric figure of merit in nanostructured p-type PbTe-MTe (M = Ca, Ba). / Biswas, Kanishka; He, Jiaqing; Wang, Guoyu; Lo, Shih Han; Uher, Ctirad; Dravid, Vinayak P.; Kanatzidis, Mercouri G.

In: Energy and Environmental Science, Vol. 4, No. 11, 11.2011, p. 4675-4684.

Research output: Contribution to journalArticle

Biswas, Kanishka ; He, Jiaqing ; Wang, Guoyu ; Lo, Shih Han ; Uher, Ctirad ; Dravid, Vinayak P. ; Kanatzidis, Mercouri G. / High thermoelectric figure of merit in nanostructured p-type PbTe-MTe (M = Ca, Ba). In: Energy and Environmental Science. 2011 ; Vol. 4, No. 11. pp. 4675-4684.
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