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Title: Analysis and Implications of Structural Complexity in Low Lattice Thermal Conductivity High Thermoelectric Performance PbTe–PbSnS 2 Composites

Abstract

The high-performance PbTe-SnTe-PbS-thermoelectric system forms a completely new composite PbTe PbSnS2 with high n-type figure of merit. Electron diffraction and high-resolution electron microscopy characterization of the thermoelectric composite PbTe + 25% PbSnS2 reveals that the system is nanostructured, with PbSnS(2)nanocrystals in the range Of 80 to 500 nm in size. In most of the cases, they are endotaxially grown within the PbTe matrix. Three independent crystal superstructures were observed for the PbSnS2 inclusions, originating from the same parent SnS-type structure. The presence of the parent structure is not excluded. Modified structural models for two of the superstructures observed in the PbSnS2 precipitates are proposed: Often, more than one of the structural phases am observed In the same nanocrystal, providing one extra phonon scattering factor in the system. Evidence was also found for the growth process of the nanocrystals, starting from PbS and followed by gradual dissolving of SnS. Our findings suggest that this nanostructured thermoelectric composite exhibits unique structural complexity, which Contributes to the low lattice thermal :conductivity reported for these nanocomposite materials.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1352613
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 28; Journal Issue: 11
Country of Publication:
United States
Language:
English

Citation Formats

Ioannidou, Chrysoula, Lioutas, Christos B., Frangis, Nikolaos, Girard, Steven N., and Kanatzidis, Mercouri G. Analysis and Implications of Structural Complexity in Low Lattice Thermal Conductivity High Thermoelectric Performance PbTe–PbSnS 2 Composites. United States: N. p., 2016. Web. doi:10.1021/acs.chemmater.6B00710.
Ioannidou, Chrysoula, Lioutas, Christos B., Frangis, Nikolaos, Girard, Steven N., & Kanatzidis, Mercouri G. Analysis and Implications of Structural Complexity in Low Lattice Thermal Conductivity High Thermoelectric Performance PbTe–PbSnS 2 Composites. United States. doi:10.1021/acs.chemmater.6B00710.
Ioannidou, Chrysoula, Lioutas, Christos B., Frangis, Nikolaos, Girard, Steven N., and Kanatzidis, Mercouri G. 2016. "Analysis and Implications of Structural Complexity in Low Lattice Thermal Conductivity High Thermoelectric Performance PbTe–PbSnS 2 Composites". United States. doi:10.1021/acs.chemmater.6B00710.
@article{osti_1352613,
title = {Analysis and Implications of Structural Complexity in Low Lattice Thermal Conductivity High Thermoelectric Performance PbTe–PbSnS 2 Composites},
author = {Ioannidou, Chrysoula and Lioutas, Christos B. and Frangis, Nikolaos and Girard, Steven N. and Kanatzidis, Mercouri G.},
abstractNote = {The high-performance PbTe-SnTe-PbS-thermoelectric system forms a completely new composite PbTe PbSnS2 with high n-type figure of merit. Electron diffraction and high-resolution electron microscopy characterization of the thermoelectric composite PbTe + 25% PbSnS2 reveals that the system is nanostructured, with PbSnS(2)nanocrystals in the range Of 80 to 500 nm in size. In most of the cases, they are endotaxially grown within the PbTe matrix. Three independent crystal superstructures were observed for the PbSnS2 inclusions, originating from the same parent SnS-type structure. The presence of the parent structure is not excluded. Modified structural models for two of the superstructures observed in the PbSnS2 precipitates are proposed: Often, more than one of the structural phases am observed In the same nanocrystal, providing one extra phonon scattering factor in the system. Evidence was also found for the growth process of the nanocrystals, starting from PbS and followed by gradual dissolving of SnS. Our findings suggest that this nanostructured thermoelectric composite exhibits unique structural complexity, which Contributes to the low lattice thermal :conductivity reported for these nanocomposite materials.},
doi = {10.1021/acs.chemmater.6B00710},
journal = {Chemistry of Materials},
number = 11,
volume = 28,
place = {United States},
year = 2016,
month = 6
}
  • The reduction of thermal conductivity, and a comprehensive understanding of the microstructural constituents that cause this reduction, represent some of the important challenges for the further development of thermoelectric materials with improved figure of merit. Model PbTe-based thermoelectric materials that exhibit very low lattice thermal conductivity have been chosen for this microstructure-thermal conductivity correlation study. The nominal PbTe{sub 0.7}S{sub 0.3} composition spinodally decomposes into two phases: PbTe and PbS. Orderly misfit dislocations, incomplete relaxed strain, and structure-modulated contrast rather than composition-modulated contrast are observed at the boundaries between the two phases. Furthermore, the samples also contain regularly shaped nanometer-scale precipitates.more » The theoretical calculations of the lattice thermal conductivity of the PbTe{sub 0.7}S{sub 0.3} material, based on transmission electron microscopy observations, closely aligns with experimental measurements of the thermal conductivity of a very low value, {approx}0.8 W m{sup -1} K{sup -1} at room temperature, approximately 35% and 30% of the value of the lattice thermal conductivity of either PbTe and PbS, respectively. It is shown that phase boundaries, interfacial dislocations, and nanometer-scale precipitates play an important role in enhancing phonon scattering and, therefore, in reducing the lattice thermal conductivity.« less
  • Lead chalcogenides have exhibited their irreplaceable role as thermoelectric materials at the medium temperature range, owing to highly degenerate electronic bands and intrinsically low thermal conductivities. PbTe-PbS pseudo-binary has been paid extensive attentions due to the even lower thermal conductivity which originates largely from the coexistence of both alloying and phase-separated precipitations. To investigate the competition between alloying and phase separation and its pronounced effect on the thermoelectric performance in PbTe-PbS, we systematically studied Spark Plasma Sintered (SPSed), 3 at% Na- doped (PbTe) 1-x(PbS)x samples with x=10%, 15%, 20%, 25%, 30% and 35% by means of transmission electron microscopy (TEM)more » observations and theoretical calculations. Corresponding to the lowest lattice thermal conductivity as a result of the balance between point defect- and precipitates- scattering, the highest figure of merit ZT~2.3 was obtained at 923 K when PbS phase fraction x is at 20%. The consistently lower lattice thermal conductivities in SPSed samples compared with corresponding ingots, resulting from the powdering and follow-up consolidation processes, also contribute to the observed superior ZT. Notably, the onset of carrier concentration modulation ~600 K due to excessive Na’s diffusion and re-dissolution leads to the observed saturations of electrical transport properties, which is believed equally crucial to the outstanding thermoelectric performance of SPSed PbTe-PbS samples.« less