Te-125 NMR chemical-shift trends in PbTe-GeTe and PbTe-SnTe alloys

TitleTe-125 NMR chemical-shift trends in PbTe-GeTe and PbTe-SnTe alloys
Publication TypeJournal Article
Year of Publication2013
AuthorsNjegic B, Levin EM, Schmidt-Rohr K
Journal TitleSolid State Nuclear Magnetic Resonance
Date Published10
Type of ArticleArticle
ISBN Number0926-2040
Accession NumberWOS:000327132700009
KeywordsGETE, glasses, local-structure, magic-angle, NUCLEI, Pb1-xGexTe, pb1-xsnxte, pbte, phase-change materials, Plane-wave DFT, shift calculation, SnTe, solid-state nmr, spectra, systems, te, Te-125 chemical, Te-125 NMR

Complex tellurides, such as doped PbTe, GeTe, and their alloys, are among the best thermoelectric materials. Knowledge of the change in Te-125 NMR chemical shift due to bonding to dopant or "solute" atoms is useful for determination of phase composition, peak assignment, and analysis of local bonding. We have measured the Te-125 NMR chemical shifts in PbTe-based alloys, Pb1-xGexTe and Pb1-xSnxTe, which have a rocksalt-like structure, and analyzed their trends. For low x, several peaks are resolved in the 22-kHz MAS Te-125 NMR spectra. A simple linear trend in chemical shifts with the number of Pb neighbors is observed. No evidence of a proposed ferroelectric displacement of Ge atoms in a cubic PbTe matrix is detected at low Ge concentrations. The observed chemical shift trends are compared with the results of DFT calculations, which confirm the linear dependence on the composition of the first-neighbor shell. The data enable determination of the composition of various phases in multiphase telluride materials. They also provide estimates of the Te-125 chemical shifts of GeTe and SnTe (+970 and + 400 +/- 150 ppm, respectively, from PbTe), which are otherwise difficult to access clue to Knight shifts of many hundreds of ppm in neat GeTe and SnTe. (C) 2013 Elsevier Inc. All rights reserved.

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