Electronic inhomogeneity and Ag:Sb imbalance of Ag1-yPb18Sb1+zTe20 high-performance thermoelectrics elucidated by Te-125 and Pb-207 NMR

TitleElectronic inhomogeneity and Ag:Sb imbalance of Ag1-yPb18Sb1+zTe20 high-performance thermoelectrics elucidated by Te-125 and Pb-207 NMR
Publication TypeJournal Article
Year of Publication2009
AuthorsLevin EM, Cook BA, Ahn K, Kanatzidis MG, Schmidt-Rohr K
Journal TitlePhysical Review B
Volume80
Pages115211
Date Published09/01
ISBN Number1098-0121
Accession NumberISI:000270383200069
Keywordsagpbmsbte2+m, artifacts, heat, high figure, merit, pb1-xsnxte, pbte, temperature
Abstract

Using magic-angle spinning Te-125 and Pb-207 NMR, we have discovered the presence of two phases of approximately tenfold different free-electron concentration, n, in high-performance thermoelectrics Ag1-yPb18Sb1+zTe20 ("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 n approximate to 2 x 10(19) cm(-3) and 0.2 x 10(19) cm(-3), respectively, determined from the spin-lattice relaxation times. Te-125 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.

URL<Go to ISI>://000270383200069
DOI10.1103/Physrevb.80.115211