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Title: Thermoelectric performance of co-doped SnTe with resonant levels

Abstract

Some group III elements such as Indium are known to produce the resonant impurity states in IV-VI compounds. The discovery of these impurity states has opened up new ways for engineering the thermoelectric properties of IV-VI compounds. In this work, resonant states in SnTe were studied by co-doping with both resonant (In) and extrinsic (Ag, I) dopants. A characteristic nonlinear relationship was observed between the Hall carrier concentration (n{sub H}) and extrinsic dopant concentration (N{sub I}, N{sub Ag}) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured n{sub H}. Upon substituting extrinsic dopants beyond a certain amount, the n{sub H} changed proportionally with additional dopants (Ag, I) (the doping region). The Seebeck coefficients are enhanced as the resonant impurity is introduced, whereas the use of extrinsic doping only induces minor changes. Modest zT enhancements are observed at lower temperatures, which lead to an increase in the average zT values over a broad range of temperatures (300–773 K). The improved average zT obtained through co-doping indicates the promise of fine carrier density control in maximizing the favorable effect of resonant levels for thermoelectric materials.

Authors:
; ;  [1];  [2];  [3];  [3];  [4]
  1. Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)
  2. Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd. Pasadena, California 91125 (United States)
  3. Materials Science, California Institute of Technology, 1200 California Blvd., Pasadena, California 91125 (United States)
  4. (Russian Federation)
Publication Date:
OSTI Identifier:
22594439
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 4; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CARRIER DENSITY; CARRIERS; CONCENTRATION RATIO; DOPED MATERIALS; IMPURITIES; INDIUM; NONLINEAR PROBLEMS; THERMOELECTRIC MATERIALS; THERMOELECTRIC PROPERTIES; TIN TELLURIDES

Citation Formats

Zhou, Min, Han, Yemao, Li, Laifeng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com, Gibbs, Zachary M., Wang, Heng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com, Snyder, G. Jeffrey, and TMO University, Saint Petersburg 197101. Thermoelectric performance of co-doped SnTe with resonant levels. United States: N. p., 2016. Web. doi:10.1063/1.4959845.
Zhou, Min, Han, Yemao, Li, Laifeng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com, Gibbs, Zachary M., Wang, Heng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com, Snyder, G. Jeffrey, & TMO University, Saint Petersburg 197101. Thermoelectric performance of co-doped SnTe with resonant levels. United States. doi:10.1063/1.4959845.
Zhou, Min, Han, Yemao, Li, Laifeng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com, Gibbs, Zachary M., Wang, Heng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com, Snyder, G. Jeffrey, and TMO University, Saint Petersburg 197101. 2016. "Thermoelectric performance of co-doped SnTe with resonant levels". United States. doi:10.1063/1.4959845.
@article{osti_22594439,
title = {Thermoelectric performance of co-doped SnTe with resonant levels},
author = {Zhou, Min and Han, Yemao and Li, Laifeng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com and Gibbs, Zachary M. and Wang, Heng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com and Snyder, G. Jeffrey and TMO University, Saint Petersburg 197101},
abstractNote = {Some group III elements such as Indium are known to produce the resonant impurity states in IV-VI compounds. The discovery of these impurity states has opened up new ways for engineering the thermoelectric properties of IV-VI compounds. In this work, resonant states in SnTe were studied by co-doping with both resonant (In) and extrinsic (Ag, I) dopants. A characteristic nonlinear relationship was observed between the Hall carrier concentration (n{sub H}) and extrinsic dopant concentration (N{sub I}, N{sub Ag}) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured n{sub H}. Upon substituting extrinsic dopants beyond a certain amount, the n{sub H} changed proportionally with additional dopants (Ag, I) (the doping region). The Seebeck coefficients are enhanced as the resonant impurity is introduced, whereas the use of extrinsic doping only induces minor changes. Modest zT enhancements are observed at lower temperatures, which lead to an increase in the average zT values over a broad range of temperatures (300–773 K). The improved average zT obtained through co-doping indicates the promise of fine carrier density control in maximizing the favorable effect of resonant levels for thermoelectric materials.},
doi = {10.1063/1.4959845},
journal = {Applied Physics Letters},
number = 4,
volume = 109,
place = {United States},
year = 2016,
month = 7
}
  • Herein, we report a significantly improved thermoelectric figure of merit ZT of ~1.1 at ~923 K in p-type SnTe through In 2Te 3 alloying and iodine doping. We propose that the introduction of indium at Sn sites in SnTe creates resonant levels inside the valence bands, thereby considerably increasing the Seebeck coefficients and power factors in the low-to-middle temperature range. Unlike SnTe–InTe, the SnTe–In 2Te 3 system displays much lower lattice thermal conductivity. Utilizing a model for point defect scattering, we analyze the origin of the low thermal conductivity in SnTe–In 2Te 3 and attribute it mainly to the strongmore » vacancy originated phonon scattering between Sn atoms and the vacancies introduced by In 2Te 3 alloying and partly to the interfacial scattering by In-rich nanoprecipitates present in SnTe matrix. By alloying only In 2Te 3 with SnTe, a ZT value of ~0.9 at 923 K was achieved. ZT can be further increased to ~1.1 at 923 K through adjusting the charge carriers by iodine doping at Te sites.« less
  • We report a significant enhancement of the thermoelectric performance of p-type SnTe over a broad temperature plateau with a peak ZT value of similar to 1.4 at 923 K through In/Cd codoping and a CdS nanostructuring approach. Indium and cadmium play different but complementary roles in modifying the valence band structure of SnTe. Specifically, In-doping introduces resonant levels inside the valence bands, leading to a considerably improved Seebeck coefficient at low temperature. Cd-doping, however, increases the Seebeck coefficient of SnTe remarkably in the mid- to high-temperature region via a convergence of the light and heavy hole bands and an enlargementmore » of the band gap. Combining the two dopants in SnTe yields enhanced Seebeck coefficient and power factor over a wide temperature range due to the synergy of resonance levels and valence band convergence, as demonstrated by the Pisarenko plot and supported by first-principles band structure calculations. Moreover, these codoped samples can be hierarchically structured on all scales (atomic point defects by doping, nanoscale precipitations by CdS nanostructuring, and mesoscale grains by SPS treatment) to achieve highly effective phonon scattering leading to strongly reduced thermal conductivities. In addition to the high maximum ZT the resultant large average ZT of similar to 0.8 between 300 and 923 K makes SnTe an attractive p-type material for high-temperature thermoelectric power generation.« less