Electronic inhomogeneity and Ag:Sb imbalance of Ag1-y Pb18 Sb1+z Te20 high-performance thermoelectrics elucidated by T 125 e and P 207 b NMR

E. M. Levin, B. A. Cook, K. Ahn, M. G. Kanatzidis, K. Schmidt-Rohr

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Abstract

Using magic-angle spinning T 125 e and P 207 b NMR, we have discovered the presence of two phases of approximately tenfold different free-electron concentration, n, in high-performance thermoelectrics Ag1-y Pb18 Sb1+z Te20 ("LAST-18"), proven by pairs of Knight-shifted NMR peaks and biexponential spin-lattice relaxation. The ratio of the phases is typically 2:1 with n2× 1019 cm-3 and 0.2× 1019 cm-3, respectively, determined from the spin-lattice relaxation times. T 125 e NMR spectra show that both phases contain similar concentrations of Sb. The low- n component is assigned to Ag-rich regions with Ag-Sb pairing (but not AgSbTe2), the dominant high- n component to PbTe:Sb resulting from the excess of Sb relative to Ag. The electronic inhomogeneity observed here must be considered in the search for a better understanding of high-performance thermoelectric materials.

Original languageEnglish
Article number115211
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume80
Issue number11
DOIs
Publication statusPublished - Sep 22 2009

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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