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Crystal structure, magnetization, Te-125 NMR, and Seebeck coefficient of Ge49Te50R1 (R = La, Pr, Gd, Dy, and Yb)

TitleCrystal structure, magnetization, Te-125 NMR, and Seebeck coefficient of Ge49Te50R1 (R = La, Pr, Gd, Dy, and Yb)
Publication TypeJournal Article
Year of Publication2017
AuthorsLevin, EM, Cooling, C, Bud'ko, SL, Straszheim, WE, Lograsso, TA
JournalMaterials Chemistry and Physics
Volume192
Pagination58-66
Date Published05
Type of ArticleArticle
ISBN Number0254-0584
Accession NumberWOS:000397685900009
Keywordsalloys, and spin-lattice, germanium telluride, GeTe alloyed with rare earth, Lattice parameters, magnetization, Materials Science, performance, power, relaxation, Seebeck coefficient, semiconductor, Te-125 NMR. spectra, transport
Abstract

GeTe, a self -doping semiconductor, is a well-known base compound for thermoelectric and phase change materials. It is known, that replacement of Ge in Ag6.5Sb6.5Ge37Te50 (TAGS -85) material by rare earth Dy significantly enhances both the power factor and thermoelectric figure of merit. Here we demonstrate how replacement of Ge in GeTe by rare earths with different atomic size and localized magnetic moments affect XRD patterns, magnetization, Te-125 NMR spectra and spin -lattice relaxation, and the Seebeck coefficient of the alloys with a nominal composition of Ge49Te50R1 (R = La, Pr, Gd, Dy, and Yb). SEM, EDS and WDS data show that rare earth atoms in the matrix are present at smaller extent compared to a nominal composition, whereas rare earth also is present in inclusions. Rare earths affect the Seebeck coefficient, which is a result of interplay between the reduction due to higher carrier concentration and enhancement due to magnetic contribution. The effect of replacement of Ge in GeTe by Dy on the Seebeck coefficient is smaller than that observed in Ag6.5Sb6.5Ge36 Te50Dy1. This can be explained by larger amount of rare earth, which can be embedded into the lattice of materials containing [Ag+ Sb] atomic pairs and possible effect from these pairs.(C) 2017 Elsevier B.V. All rights reserved.

DOI10.1016/j.matchemphys.2017.01.038
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Complex States

Alternate JournalMater. Chem. Phys.