Superionic diffusion and anharmonic lattice dynamics in AgCrSe2

ORAL

Abstract

Superionic conductors exhibit promising thermoelectric properties due to their ultralow thermal conductivity. The fundamental mechanisms have long been debated between the anharmonicity or the breakdown of transverse acoustic (TA) phonons, where the shearing vibrational degrees of freedom are lost, as in a liquid state. We report on neutron/x-ray scattering and first-principles studies on the lattice dynamics and ionic diffusion of AgCrSe2. Our momentum-resolved measurements on single-crystals clearly establish the persistence of long-wavelength TA phonons in the superionic phase, whereas the shorter wavelength, non-dispersive portions of the TA branches severely broaden reflecting extreme anharmonicity. Further, we find a strong repulsion between Ag neighbors, affecting the diffusion mechanism. Our studies of atomic dynamics and diffusion will help rationalize the emergence of ultralow thermal conductivity for thermoelectrics and facilitate the design of high-performance solid-state electrolytes.

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Presenters

  • Jingxuan Ding

    Mechanical Engineering and Materials Science, Duke University, Duke University

Authors

  • Jingxuan Ding

    Mechanical Engineering and Materials Science, Duke University, Duke University

  • Jennifer L Niedziela

    Oak Ridge National Laboratory

  • Dipanshu Bansal

    Indian Institute of Technology Bombay, Mechanical Engineering, Indian Institute of Technology Bombay, Department of Mechanical Engineering & Materials Science, Duke University

  • Andrew May

    Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA, Oak Ridge National Laboratory, Materials Science and Technology Division, Oak-Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge National Lab, Materials Science and Technology Division, Oak Ridge National Laboratory

  • Georg Ehlers

    Oak Ridge National Laboratory, Oak Ridge National Lab, SNS, Oak Ridge National Lab, Neutron Scattering Division, Oak-Ridge National Laboratory

  • Douglas L Abernathy

    Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge National Laboratory, Neutron Scattering Division, Oak Ridge National Laboratory, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6475, USA

  • Yang Ren

    Argonne National Laboratory, Advanced Photon Source, Argonne National Laboratory

  • Ayman Said

    Argonne National Laboratory, Argonne Natl Lab, Advanced Photon Source, Argonne National Laboratory

  • Olivier Delaire

    Department of Mechanical Engineering and Materials Science, Duke University, Mechanical Engineering and Materials Science, Physics, Duke University, Duke University, Department of Mechanical Engineering & Materials Science, Duke University