Anomalous Lattice Thermal Conductivity in Rocksalt IIA-VIA Compounds

Materials with an intrinsic (ultra)low lattice thermal conductivity (k\(_L\)) are critically important for the development of efficient energy conversion devices. In the present work, we have investigated microscopic origins of low k\(_L\) behavior in BaO, BaS and MgTe by exploring lattice dynamics...

Full description

Saved in:
Bibliographic Details
Published inarXiv.org
Main Authors Rakesh Roshan, S C, Yedukondalu, N, Rajmohan Muthaiah, Lavanya, K, Anees, P, R Rakesh Kumar, Rao, T Venkatappa, Ehm, Lars, Parise, John B
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 26.10.2021
Subjects
Acoustics
Atomic properties
Barium oxides
Barium sulfides
Energy conversion
Ferroelectricity
Heat conductivity
Heat transfer
Lattice vibration
Lead tellurides
Phonons
Scattering
Softening
Tensile strain
Thermal conductivity
Transport properties
Online AccessGet full text

Cover

More Information
Summary:Materials with an intrinsic (ultra)low lattice thermal conductivity (k\(_L\)) are critically important for the development of efficient energy conversion devices. In the present work, we have investigated microscopic origins of low k\(_L\) behavior in BaO, BaS and MgTe by exploring lattice dynamics and phonon transport of 16 iso-structural MX (Mg, Ca, Sr, Ba and X = O, S, Se and Te) compounds in the rocksalt (NaCl)-type structure by comparing their lattice transport properties with the champion thermoeletric iso-structural material, PbTe. Anomalous trends are observed for k\(_L\) in MX compounds except the MgX series in contrast to the expected trend from their atomic mass. The underlying mechanisms for such low k\(_L\) behavior in relatively low atomic mass systems namely BaO, BaS and MgTe compounds are thoroughly analyzed. We propose the following dominant factors that might be responsible for low k\(_L\) behavior in these materials: 1) softening of transverse acoustic (TA) phonon modes despite low atomic mass, 2) low lying optic (LLO) phonon modes fall deep into acoustic mode region which enhances overlap between longitudinal acoustic (LA) and LLO phonon modes which increases scattering phase space, 3) short phonon lifetimes and high scattering rates, 4) relatively high density (\r{ho}) and large Gr\"uneisen parameter. Moreover, tensile strain also causes a further reduction in k\(_L\) for BaO, BaS and MgTe through phonon softening and near ferroelectric instability. Our comprehensive study on 16 binary MX compounds might provide a pathway for designing (ultra)low k\(_L\) materials even with simple crystal systems through phonon engineering.
ISSN:2331-8422