High thermoelectric performance of p-type SnTe via a synergistic band engineering and nanostructuring approach

Gangjian Tan, Li Dong Zhao, Fengyuan Shi, Jeff W. Doak, Shih Han Lo, Hui Sun, Chris Wolverton, Vinayak P. Dravid, Ctirad Uher, Mercouri G Kanatzidis

Research output: Contribution to journalArticle

216 Citations (Scopus)

Abstract

SnTe is a potentially attractive thermoelectric because it is the lead-free rock-salt analogue of PbTe. However, SnTe is a poor thermoelectric material because of its high hole concentration arising from inherent Sn vacancies in the lattice and its very high electrical and thermal conductivity. In this study, we demonstrate that SnTe-based materials can be controlled to become excellent thermoelectrics for power generation via the successful application of several key concepts that obviate the well-known disadvantages of SnTe. First, we show that Sn self-compensation can effectively reduce the Sn vacancies and decrease the hole carrier density. For example, a 3 mol % self-compensation of Sn results in a 50% improvement in the figure of merit ZT. In addition, we reveal that Cd, nominally isoelectronic with Sn, favorably impacts the electronic band structure by (a) diminishing the energy separation between the light-hole and heavy-hole valence bands in the material, leading to an enhanced Seebeck coefficient, and (b) enlarging the energy band gap. Thus, alloying with Cd atoms enables a form of valence band engineering that improves the high-temperature thermoelectric performance, where p-type samples of SnCd0.03Te exhibit ZT values of ∼0.96 at 823 K, a 60% improvement over the Cd-free sample. Finally, we introduce endotaxial CdS or ZnS nanoscale precipitates that reduce the lattice thermal conductivity of SnCd0.03Te with no effect on the power factor. We report that SnCd0.03Te that are endotaxially nanostructured with CdS and ZnS have a maximum ZTs of ∼1.3 and ∼1.1 at 873 K, respectively. Therefore, SnTe-based materials could be ideal alternatives for p-type lead chalcogenides for high temperature thermoelectric power generation.

Original languageEnglish
Pages (from-to)7006-7017
Number of pages12
JournalJournal of the American Chemical Society
Volume136
Issue number19
DOIs
Publication statusPublished - May 14 2014

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Thermal Conductivity
Electric Conductivity
Temperature
Valence bands
Band structure
Vacancies
Power generation
Thermal conductivity
Salts
Lead
Hole concentration
Chalcogenides
Seebeck coefficient
Thermoelectric power
Alloying
Crystal lattices
Carrier concentration
Precipitates
Energy gap
Rocks

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

High thermoelectric performance of p-type SnTe via a synergistic band engineering and nanostructuring approach. / Tan, Gangjian; Zhao, Li Dong; Shi, Fengyuan; Doak, Jeff W.; Lo, Shih Han; Sun, Hui; Wolverton, Chris; Dravid, Vinayak P.; Uher, Ctirad; Kanatzidis, Mercouri G.

In: Journal of the American Chemical Society, Vol. 136, No. 19, 14.05.2014, p. 7006-7017.

Research output: Contribution to journalArticle

Tan, Gangjian ; Zhao, Li Dong ; Shi, Fengyuan ; Doak, Jeff W. ; Lo, Shih Han ; Sun, Hui ; Wolverton, Chris ; Dravid, Vinayak P. ; Uher, Ctirad ; Kanatzidis, Mercouri G. / High thermoelectric performance of p-type SnTe via a synergistic band engineering and nanostructuring approach. In: Journal of the American Chemical Society. 2014 ; Vol. 136, No. 19. pp. 7006-7017.
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AU - Lo, Shih Han

AU - Sun, Hui

AU - Wolverton, Chris

AU - Dravid, Vinayak P.

AU - Uher, Ctirad

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AB - SnTe is a potentially attractive thermoelectric because it is the lead-free rock-salt analogue of PbTe. However, SnTe is a poor thermoelectric material because of its high hole concentration arising from inherent Sn vacancies in the lattice and its very high electrical and thermal conductivity. In this study, we demonstrate that SnTe-based materials can be controlled to become excellent thermoelectrics for power generation via the successful application of several key concepts that obviate the well-known disadvantages of SnTe. First, we show that Sn self-compensation can effectively reduce the Sn vacancies and decrease the hole carrier density. For example, a 3 mol % self-compensation of Sn results in a 50% improvement in the figure of merit ZT. In addition, we reveal that Cd, nominally isoelectronic with Sn, favorably impacts the electronic band structure by (a) diminishing the energy separation between the light-hole and heavy-hole valence bands in the material, leading to an enhanced Seebeck coefficient, and (b) enlarging the energy band gap. Thus, alloying with Cd atoms enables a form of valence band engineering that improves the high-temperature thermoelectric performance, where p-type samples of SnCd0.03Te exhibit ZT values of ∼0.96 at 823 K, a 60% improvement over the Cd-free sample. Finally, we introduce endotaxial CdS or ZnS nanoscale precipitates that reduce the lattice thermal conductivity of SnCd0.03Te with no effect on the power factor. We report that SnCd0.03Te that are endotaxially nanostructured with CdS and ZnS have a maximum ZTs of ∼1.3 and ∼1.1 at 873 K, respectively. Therefore, SnTe-based materials could be ideal alternatives for p-type lead chalcogenides for high temperature thermoelectric power generation.

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