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Local composition and carrier concentration in Pb0.7Ge0.3Te and Pb0.5Ge0.5Te alloys from Te-125 NMR and microscopy

TitleLocal composition and carrier concentration in Pb0.7Ge0.3Te and Pb0.5Ge0.5Te alloys from Te-125 NMR and microscopy
Publication TypeJournal Article
Year of Publication2014
AuthorsLevin, EM, Kramer, MJ, Schmidt-Rohr, K
JournalJournal of Physics and Chemistry of Solids
Volume75
Pagination1269-1276
Date Published11
Type of ArticleArticle
ISBN Number0022-3697
Accession NumberWOS:000340984700014
Keywordsband structure, chalcogenides, design, Electron microscopy, germanium telluride, gete, Microstructure, Nuclear magnetic resonance (NMR), pbte, semiconductors, thermoelectric-materials, X-ray diffraction
Abstract

Pb0.7Ge0.3Te and Pb0.5Ge0.5Te alloys, (i) quenched from 923 K or (ii) quenched and annealed at 573 K for 2 h, have been studied by Te-125 NMR, X-ray diffraction, electron and optical microscopy, as well as energy dispersive spectroscopy. Depending on the composition and thermal treatment history, Te-125 NMR spectra exhibit different resonance frequencies and spin-lattice relaxation times, which can be assigned to different phases in the alloy. Quenched and annealed Pb0.7Ge0.3Te alloys can be considered as solid solutions but are shown by NMR to have components with various carrier concentrations. Quenched and annealed Pb0.5Ge0.5Te alloys contain GeTe- and PbTe-based phases with different compositions and charge carrier concentrations. Based on the analysis of non-exponential Te-125 NMR spin-lattice relaxation, the fractions and carrier concentrations of the various phases have been estimated. Our data show that alloying of PbTe with Ge results in the formation of chemically and electronically inhomogeneous systems. Te-125 NMR can be used as an efficient probe to detect the local composition in equilibrium as well as non-equilibrium states, and to determine the local carrier concentrations in complex multiphase tellurides. (C) 2014 Elsevier Ltd. All rights reserved.

DOI10.1016/j.jpcs.2014.06.004
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SSNMR

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Structures and Dynamics