Glass-like phonon scattering from a spontaneous nanostructure in AgSbTe2


Materials with very low thermal conductivity are of great interest for both thermoelectric and optical phase-change applications. Synthetic nanostructuring is most promising for suppressing thermal conductivity through phonon scattering, but challenges remain in producing bulk samples. In crystalline AgSbTe2 we show that a spontaneously forming nanostructure leads to a suppression of thermal conductivity to a glass-like level. Our mapping of the phonon mean free paths provides a novel bottom-up microscopic account of thermal conductivity and also reveals intrinsic anisotropies associated with the nanostructure. Ground-state degeneracy in AgSbTe2 leads to the natural formation of nanoscale domains with different orderings on the cation sublattice, and correlated atomic displacements, which efficiently scatter phonons. This mechanism is general and suggests a new avenue for the nanoscale engineering of materials to achieve low thermal conductivities for efficient thermoelectric converters and phase-change memory devices.

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Figure 1: Single-crystal phonon data for δ-phase AgSbTe2 at 300 K.
Figure 2: Temperature dependence of phonon properties, showing limited anharmonicity below 300 K.
Figure 3: TEM and neutron diffuse scattering, revealing the nanostructure in δ-phase AgSbTe2.
Figure 4: Mean free paths and lattice thermal conductivity derived from INS data.


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Simulations and integration of results (O.D.), as well as synthesis and characterization (A.F.M., M.A.M. and B.C.S) were supported by the US Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division. Neutron scattering (J.M.) and electron microscopy (C.E.C. and Y.S-H.) were supported by the US Department of Energy, Office of Basic Energy Sciences, through the S3TEC Energy Frontier Research Center (DESC0001299). L.H.V. and V.M.K. acknowledge support provided by the Joint Directed Research and Development programme of the UTK Science Alliance. The Oak Ridge National Laboratory's Spallation Neutron Source and High-Flux Isotope Reactor are sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

Author information




O.D. designed the study. O.D. and J.M. performed and analysed neutron scattering experiments, and wrote the manuscript. A.F.M., M.A.M. and B.C.S. synthesized and characterized the samples. C.E.C and Y.S-H. performed electron microscopy and analysed the results thereof. L.H.V. and V.M.K. performed and analysed ultrasound measurements. O.D. performed first-principles simulations. D.L.A, G.E., T.H., A.H. and W.T. helped with neutron data acquisition.

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Correspondence to O. Delaire.

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Ma, J., Delaire, O., May, A. et al. Glass-like phonon scattering from a spontaneous nanostructure in AgSbTe2. Nature Nanotech 8, 445–451 (2013).

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