Journal
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
Volume 41, Issue 15, Pages 7981-7987Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jeurceramsoc.2021.07.066
Keywords
Optical phonons; Thermal conductivity; Lattice dynamics; Thermal transport mechanisms; Thermal barrier coatings
Categories
Funding
- Na-tional Natural Science Foundation of China [51472135, 52073156, 91960104]
- Basic Discipline Development Fund of Army Engineering University of PLA [KYJBJQZL1905]
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The contribution of optical phonons in complex structural low thermal conductivity oxides, especially in La2Zr2O7, was found to be significant. As structural complexity increases, the contribution of optical phonons becomes more pronounced. This highlights the importance of considering optical phonon contributions in understanding lattice thermal conductivity in crystalline materials.
It has generally been believed that the lattice thermal conductivity (kappa(L)) is mainly contributed by acoustic phonons and the contribution of optical phonons can be neglected in crystalline materials. However, in this work, we demonstrate that the contribution of optical phonons play an important role in the complex structural low-kappa(L) oxides. The mode-wised kappa(L) of three representative oxides, MgO, BaHfO3 and La2Zr2O7, with different structural complexity was calculated using first-principles phonon Boltzmann transport equation (BTE) method. It is found that the contribution of optical phonons become significant as the structural complexity increases. Especially, for La2Zr2O7, the kappa(L) is dominated by optical phonons due to the large density of states. Optical phonons exhibit amorphous-like phonon-phonon scattering characteristics that are different from those of acoustic phonons. Furthermore, calculations for materials other than the three representative oxides were conducted and the results confirmed the validity of our conclusions.
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