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Title: Criteria for extending the operation periods of thermoelectric converters based on IV-VI compounds

Abstract

The recent energy demands affected by the dilution of conventional energy resources and the growing awareness of environmental considerations, had positioned the research of renewable energy conversion methods in general and of thermoelectric direct conversion of thermal into electrical energies in particular, in the forefront of the currently active applicative sciences. IV-VI thermoelectric compounds (e.g. GeTe, PbTe and SnTe) and their alloys comprise some of the most efficient thermoelectric compositions ever reported. Yet a proper utilization of such materials in practical thermoelectric devices, still requires an overcoming the so-called technological “valley of death”, including among others, transport properties' degradation, due to sublimation of volatile Te rich species, while being subjected to elevated temperatures for long periods of time. In an attempt to establish practical operation criteria for extending the operation periods of such thermoelectric converters, it is currently shown based on thermal gravimetric and metallurgical considerations that such harmful sublimation can be practically bridged over by limiting the maximal operating temperatures to the 410–430 °C range for GeTe rich alloys and to 510–530 °C for PbTe and SnTe rich alloys, depending of the thermoelectric leg's diameter. - Graphical abstract: Evaporation rate in the GeTe and PbTe system showing the measuredmore » evaporation rates and the maximal operating temperatures for different compositions. In addition, the microstructure after evaporation is shown for PbTe, TAGS-85, and doped Pb{sub 0.13}Ge{sub 087}Te. Display Omitted - Highlights: • Evaporation rates of GeTe and PbTe based thermoelectric compounds were determined. • A criterion for their maximum operating temperature was established. • The materials showed phase separations and off-stoichiometry compositions.« less

Authors:
 [1];  [2]; ; ;  [1]
  1. Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva (Israel)
  2. Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva (Israel)
Publication Date:
OSTI Identifier:
22584196
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 241; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALLOYS; DOPED MATERIALS; ENERGY CONVERSION; ENERGY DEMAND; GERMANIUM; GERMANIUM TELLURIDES; LEAD; LEAD TELLURIDES; MICROSTRUCTURE; SUBLIMATION; THERMOELECTRIC GENERATORS; TIN TELLURIDES; VOLATILITY

Citation Formats

Sadia, Yatir, E-mail: yatttir@yahoo.com, Ohaion-Raz, Tsion, Ben-Yehuda, Ohad, Korngold, Meidad, and Gelbstein, Yaniv. Criteria for extending the operation periods of thermoelectric converters based on IV-VI compounds. United States: N. p., 2016. Web. doi:10.1016/J.JSSC.2016.06.006.
Sadia, Yatir, E-mail: yatttir@yahoo.com, Ohaion-Raz, Tsion, Ben-Yehuda, Ohad, Korngold, Meidad, & Gelbstein, Yaniv. Criteria for extending the operation periods of thermoelectric converters based on IV-VI compounds. United States. doi:10.1016/J.JSSC.2016.06.006.
Sadia, Yatir, E-mail: yatttir@yahoo.com, Ohaion-Raz, Tsion, Ben-Yehuda, Ohad, Korngold, Meidad, and Gelbstein, Yaniv. Thu . "Criteria for extending the operation periods of thermoelectric converters based on IV-VI compounds". United States. doi:10.1016/J.JSSC.2016.06.006.
@article{osti_22584196,
title = {Criteria for extending the operation periods of thermoelectric converters based on IV-VI compounds},
author = {Sadia, Yatir, E-mail: yatttir@yahoo.com and Ohaion-Raz, Tsion and Ben-Yehuda, Ohad and Korngold, Meidad and Gelbstein, Yaniv},
abstractNote = {The recent energy demands affected by the dilution of conventional energy resources and the growing awareness of environmental considerations, had positioned the research of renewable energy conversion methods in general and of thermoelectric direct conversion of thermal into electrical energies in particular, in the forefront of the currently active applicative sciences. IV-VI thermoelectric compounds (e.g. GeTe, PbTe and SnTe) and their alloys comprise some of the most efficient thermoelectric compositions ever reported. Yet a proper utilization of such materials in practical thermoelectric devices, still requires an overcoming the so-called technological “valley of death”, including among others, transport properties' degradation, due to sublimation of volatile Te rich species, while being subjected to elevated temperatures for long periods of time. In an attempt to establish practical operation criteria for extending the operation periods of such thermoelectric converters, it is currently shown based on thermal gravimetric and metallurgical considerations that such harmful sublimation can be practically bridged over by limiting the maximal operating temperatures to the 410–430 °C range for GeTe rich alloys and to 510–530 °C for PbTe and SnTe rich alloys, depending of the thermoelectric leg's diameter. - Graphical abstract: Evaporation rate in the GeTe and PbTe system showing the measured evaporation rates and the maximal operating temperatures for different compositions. In addition, the microstructure after evaporation is shown for PbTe, TAGS-85, and doped Pb{sub 0.13}Ge{sub 087}Te. Display Omitted - Highlights: • Evaporation rates of GeTe and PbTe based thermoelectric compounds were determined. • A criterion for their maximum operating temperature was established. • The materials showed phase separations and off-stoichiometry compositions.},
doi = {10.1016/J.JSSC.2016.06.006},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 241,
place = {United States},
year = {Thu Sep 15 00:00:00 EDT 2016},
month = {Thu Sep 15 00:00:00 EDT 2016}
}
  • Doping in a manner that introduces anisotropy in order to reduce thermal conductivity is a significant focus in thermoelectric research today. By solving the semiclassical Boltzmann transport equations in the constant scattering time (τ) approximation, in conjunction with ab initio electronic structure calculations, within Density Functional Theory, we compare the Seebeck coefficient (S) and figure of merit (ZT) of bulk PbTe to PbTe/SnTe/PbTe heterostructures and PbTe doping superlattices (SLs) with periodically doped planes. Bismuth and Thallium were used as the n- and p-type impurities, respectively. The effects of carrier concentration are considered via chemical potential variation in a rigid bandmore » approximation. The impurity bands near the Fermi level in the electronic structure of PbTe SLs are of Tl s- and Bi p-character, and this feature is independent of the doping concentration or the distance between impurity planes. We observe the impurity bands to have a metallic nature in the directions perpendicular to the doping planes, yet no improvement on the values of ZT is found when compared to bulk PbTe. For the PbTe/SnTe/PbTe heterostructures, the calculated S presents good agreement with recent experimental data, and an anisotropic behavior is observed for low carrier concentrations (n<10{sup 18} cm{sup −3}). A large value of ZT{sub ||} (parallel to the growth direction) of 3.0 is predicted for n=4.7×10{sup 18} cm{sup −3} and T=700 K, whereas ZT{sub p} (perpendicular to the growth direction) is found to peak at 1.5 for n=1.7×10{sup 17} cm{sup −3}. Both electrical conductivity enhancement and thermal conductivity reduction are analyzed. - Graphical abstract: Figure of merit for PbTe/SnTe/PbTe heterostructure along the [0 0 1] direction, P.D. Borges, J.E. Petersen, L. Scolfaro, H.W. Leite Alves, T.H. Myers, Improved thermoelectric properties of IV–VI-based heterostructures and superlattices. - Highlights: • Thermoelectric properties of IV–VI-based heterostructures and superlattices. • High figure of merit is predicted for the PbTe/SnTe/PbTe heterostructure. • Nanotechnology has an important role for the development of thermoelectric devices.« less
  • Element- and orbital-selective x-ray absorption and magnetic circular dichroism measurements are carried out to probe the electronic structure and magnetism of Ir 5d electronic states in double perovskite Sr2MIrO6 (M = Mg, Ca, Sc, Ti, Ni, Fe, Zn, In) and La2NiIrO6 compounds. All the studied systems present a significant influence of spin-orbit interactions in the electronic ground state. In addition, we find that the Ir 5d local magnetic moment shows different character depending on the oxidation state despite the net magnetization being similar for all the compounds. Ir carries an orbital contribution comparable to the spin contribution for Ir4+ (5d(5))more » and Ir5+ (5d(4)) oxides, whereas the orbital contribution is quenched for Ir6+ (5d(3)) samples. Incorporation of a magnetic 3d atom allows getting insight into the magnetic coupling between 5d and 3d transition metals. Together with previous susceptibility and neutron diffractionmeasurements, the results indicate that Ir carries a significant local magnetic moment even in samples without a 3d metal. The size of the (small) net magnetization of these compounds is a result of predominant antiferromagnetic interactions between local moments coupled with structural details of each perovskite structure« less
  • Cited by 16
  • Three new diamond-like compounds with the formula of I{sub 2}−II−IV−VI{sub 4} (I=Cu; II=Mg; IV=Si, Ge; VI=S, Se) have been synthesized via traditional high-temperature solid-state reactions and structurally characterized by single crystal X-ray diffraction analysis. All the three compounds crystallize in the space group Pmn2{sub 1} in the wurtzite-type superstructure with a=7.563(4), b=6.448(3), c=6.179(3) Å, Z=2 for Cu{sub 2}MgSiS{sub 4} (1); a=7.953(5), b=6.797(4), c=6.507(4) Å, Z=2 for Cu{sub 2}MgGeS{sub 4} (2); a=7.638(4), b=6.515(4), c=6.225(3) Å, Z=2 for Cu{sub 2}MgSiSe{sub 4} (3). All atoms in these compounds are tetrahedrally coordinated. Optical diffuse reflectance UV/Vis/NIR spectra indicate that compounds 1 and 2 havemore » the band gaps of 3.20 and 2.36 eV, respectively. Electronic structure calculations using the CASTEP code indicate that they are all direct band gap compounds. - Graphical abstract: Three new diamond-like compounds, Cu{sub 2}MgSiS{sub 4}, Cu{sub 2}MgGeS{sub 4}, and Cu{sub 2}MgSiSe{sub 4}, have been synthesized. All the three compounds crystallize in the space group Pmn2{sub 1} and all atoms are tetrahedrally coordinated. Highlights: • Three new diamond-like compounds Cu{sub 2}MgSiS{sub 4}, Cu{sub 2}MgGeS{sub 4} and Cu{sub 2}MgSiSe{sub 4} have been synthesized. • All ions are tetrahedrally coordinated. • Electronic structure calculations indicate that they are all direct band gap compounds.« less