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Evolution of phase segregation and eutectic structures in AgPb18SbTe20

Dadda, Jayaram and Müller, Eckhard and Perlt, Susanne and Höche, Thomas and Hermann, Raphael P. and Neubrand, Achim (2014) Evolution of phase segregation and eutectic structures in AgPb18SbTe20. Physica Status Solidi (A) - Applications and Materials Science, 211 (6), pp. 1276-1281. Wiley. doi: 10.1002/pssa.201300199. ISSN 1862-6300.

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The evolution of phase segregation in stoichiometric quenched AgPbmSbTe2+m (m = 18, Lead–Antimony–Silver–Tellurium – LAST-18) compounds was studied starting from the known pseudo-binary diagrams among Ag2Te, PbTe, Sb2Te3 and AgSbTe2. The compositions of secondary phases indicate that liquid phase during cooling, even under quenching conditions, follows mainly the liquidus line on the 2PbTe–Ag0.45Sb0.55Te1.05 quasi-binary section of the phase diagram until it reaches a critical point (18 mol.% of 2PbTe) and then turns to Ag2Te- and Sb2Te3-rich sides of quasi-ternary system. This has led to the formation of various secondary phases at various stages during the solidification, whose microstructural features and morphology strongly depend upon their chemical composition. Moreover, during solidification the local compositional fluctuations of liquid phase in combination with the shift of liquid composition towards Sb-rich side of the phase diagram resulted in the development of eutectic microstructures in some regions of LAST-18 matrix phase. This suggests there exists a miscibility gap and eutectic point below 600 °C on the 2PbTe–Ag0.45Sb0.55Te1.05 boundary line. These eutectic lamellar structures with a cumulative composition close to LAST-3 are on the 200–500 nm length scales and possess thermal conductivity of 0.55–0.65 W/m K at room temperature. The low thermal conductivity of lamellar eutectic structures was later confirmed on bulk samples using laser flash analysis, where the samples were synthesized by quenching and annealing. The results clearly demonstrate that one can engineer the microstructures in LAST compounds by selecting the appropriate initial composition from quasi PbTe–Ag2Te–Sb2Te3 ternary phase diagram to lower the thermal conductivity further.

Item URL in elib:https://elib.dlr.de/92500/
Document Type:Article
Title:Evolution of phase segregation and eutectic structures in AgPb18SbTe20
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Dadda, JayaramGerman Aerospace Center, Institute of Materials Research, Köln, GermanyUNSPECIFIED
Müller, EckhardGerman Aerospace Center, Institute of Materials Research, Köln, Germany and Justus Liebig University Giessen, Institute of Inorganic and Analytical Chemistry, 35392 Giessen, GermanyUNSPECIFIED
Perlt, SusanneLeibniz Institute of Surface Modification (IOM), D-04318 Leipzig, GermanyUNSPECIFIED
Höche, ThomasFraunhofer Institute for Mechanics of Materials (IWM), Halle, GermanyUNSPECIFIED
Hermann, Raphael P.Peter Grünberg Institut and Jülich Centre for Neutron Science, JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany and Faculte des Sciences, Universite de Liege, B-4000, Liege, BelgiumUNSPECIFIED
Neubrand, AchimFraunhofer IWM, Freiburg, GermanyUNSPECIFIED
Date:21 May 2014
Journal or Publication Title:Physica Status Solidi (A) - Applications and Materials Science
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1002/pssa.201300199
Page Range:pp. 1276-1281
Keywords:Ag–Pb–Sb–Te; eutectic lamellar structures; LAST; phase segregations; thermoelectricity; thermal conductivity
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Terrestrial Vehicles (old)
DLR - Research area:Transport
DLR - Program:V BF - Bodengebundene Fahrzeuge
DLR - Research theme (Project):V - Fahrzeugenergiesystem III (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Thermoelectric Materials and Systems
Deposited By: Zabrocki, Dr. Knud
Deposited On:25 Nov 2014 10:39
Last Modified:06 Sep 2019 15:29

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