Premium
Lattice Softening Significantly Reduces Thermal Conductivity and Leads to High Thermoelectric Efficiency
Author(s) -
Hanus Riley,
Agne Matthias T.,
Rettie Alexander J. E.,
Chen Zhiwei,
Tan Gangjian,
Chung Duck Young,
Kanatzidis Mercouri G.,
Pei Yanzhong,
Voorhees Peter W.,
Snyder G. Jeffrey
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201900108
Subject(s) - materials science , phonon , condensed matter physics , thermal conductivity , thermoelectric materials , thermoelectric effect , phonon scattering , scattering , composite material , thermodynamics , optics , physics
Abstract The influence of micro/nanostructure on thermal conductivity is a topic of great scientific interest, particularly to thermoelectrics. The current understanding is that structural defects decrease thermal conductivity through phonon scattering where the phonon dispersion and speed of sound are assumed to remain constant. Experimental work on a PbTe model system is presented, which shows that the speed of sound linearly decreases with increased internal strain. This softening of the materials lattice completely accounts for the reduction in lattice thermal conductivity, without the introduction of additional phonon scattering mechanisms. Additionally, it is shown that a major contribution to the improvement in the thermoelectric figure of merit (zT > 2) of high‐efficiency Na‐doped PbTe can be attributed to lattice softening. While inhomogeneous internal strain fields are known to introduce phonon scattering centers, this study demonstrates that internal strain can modify phonon propagation speed as well. This presents new avenues to control lattice thermal conductivity, beyond phonon scattering. In practice, many engineering materials will exhibit both softening and scattering effects, as is shown in silicon. This work shines new light on studies of thermal conductivity in fields of energy materials, microelectronics, and nanoscale heat transfer.