CONTRIBUTION OF LOW-FREQUENCY LONGITUDINAL PHONONS TO THE LATTICE THERMAL CONDUCTIVITY OF DIELECTRIC SOLIDS

1981 ◽  
Vol 42 (C6) ◽  
pp. C6-256-C6-258
Author(s):  
R. Brito-Orta ◽  
P. G. Klemens
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Low Frequency ◽  
Dielectric Solids

Onset of size effects in lattice thermal conductivity and lifetime of low-frequency thermal phonons

2012 ◽  
Vol 1404 ◽  
Author(s):  
A.A. Maznev
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Size Effects ◽  
Lattice Thermal Conductivity ◽  
Low Frequency ◽  
Square Root ◽  
Relaxation Rates ◽  
Frequency Limit ◽  
Conductivity Of Thin Films ◽  
Closed Form Formula

ABSTRACTThe onset of size effects in phonon-mediated thermal transport along a thin film at temperatures comparable or greater than the Debye temperature is analyzed theoretically. Assuming a quadratic frequency dependence of phonon relaxation rates in the low-frequency limit, a simple closed-form formula for the reduction of the in-plane thermal conductivity of thin films is derived. The effect scales as the square root of the film thickness, which leads to the prediction of measurable size-effects even at “macroscopic” distances ~100 μm. However, this prediction needs to be corrected to account for the deviation from the ω−2 dependence of phonon lifetimes at sub-THz frequencies due to the transition from Landau-Rumer to Akhiezer mechanism of phonon dissipation.

scholarly journals Violation of the T−1 Relationship in the Lattice Thermal Conductivity of Mg3Sb2 with Locally Asymmetric Vibrations

Research ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yifan Zhu ◽  
Yi Xia ◽  
Yancheng Wang ◽  
Ye Sheng ◽  
Jiong Yang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Temperature Dependence ◽  
Lattice Thermal Conductivity ◽  
Elevated Temperatures ◽  
Low Frequency ◽  
Strong Temperature Dependence ◽  
Depth Analysis ◽  
Force Profile ◽  
Phonon Renormalization ◽  
Increasing Temperature

Most crystalline materials follow the guidelines of T−1 temperature-dependent lattice thermal conductivity (κL) at elevated temperatures. Here, we observe a weak temperature dependence of κL in Mg3Sb2, T−0.48 from theory and T−0.57 from measurements, based on a comprehensive study combining ab initio molecular dynamics calculations and experimental measurements on single crystal Mg3Sb2. These results can be understood in terms of the so-called “phonon renormalization” effects due to the strong temperature dependence of the interatomic force constants (IFCs). The increasing temperature leads to the frequency upshifting for those low-frequency phonons dominating heat transport, and more importantly, the phonon-phonon interactions are weakened. In-depth analysis reveals that the phenomenon is closely related to the temperature-induced asymmetric movements of Mg atoms within MgSb4 tetrahedron. With increasing temperature, these Mg atoms tend to locate at the areas with relatively low force in the force profile, leading to reduced effective 3rd-order IFCs. The locally asymmetrical atomic movements at elevated temperatures can be further treated as an indicator of temperature-induced variations of IFCs and thus relatively strong phonon renormalization. The present work sheds light on the fundamental origins of anomalous temperature dependence of κL in thermoelectrics.

Anisotropic intrinsic lattice thermal conductivity of borophane from first-principles calculations

2017 ◽  
Vol 19 (4) ◽  
pp. 2843-2849 ◽  
Author(s):  
Gang Liu ◽  
Haifeng Wang ◽  
Yan Gao ◽  
Jian Zhou ◽  
Hui Wang
Keyword(s):  
Thermal Conductivity ◽  
First Principles ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Low Frequency ◽  
First Principles Calculations ◽  
Very Low Frequency

The thermal transport of borophane is decided by phonons with very low frequency.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

scholarly journals Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aastha Vasdev ◽  
Moinak Dutta ◽  
Shivam Mishra ◽  
Veerpal Kaur ◽  
Harleen Kaur ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Direct Evidence ◽  
Temperature Dependent ◽  
Force Microscopy ◽  
Ferroelectric Domains ◽  
Pdf Analysis ◽  
Ferroelectric Transition Temperature

AbstractA remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

Study of lattice thermal conductivity of tungsten containing bubbles by molecular dynamics simulation

2020 ◽  
Vol 161 ◽  
pp. 112004
Author(s):  
Hongyu Zhang ◽  
Jizhong Sun ◽  
Yingmin Wang ◽  
Thomas Stirner ◽  
Ali Y. Hamid ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Lattice Thermal Conductivity ◽  
Dynamics Simulation

Ultra-low lattice thermal conductivity and high thermoelectric efficiency of K3AuO

2021 ◽  
Vol 130 (4) ◽  
pp. 045101
Author(s):  
Qi Zhong ◽  
Zhenhong Dai ◽  
Junping Wang ◽  
Yinchang Zhao ◽  
Sheng Meng
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Thermoelectric Efficiency

scholarly journals Approximate models for the lattice thermal conductivity of alloy thermoelectrics

2021 ◽  
Author(s):  
Jonathan Skelton
Keyword(s):  
Thermal Conductivity ◽  
Energy Efficiency ◽  
Lattice Thermal Conductivity ◽  
Waste Heat ◽  
Seebeck Effect ◽  
Thermoelectric Generators ◽  
Approximate Models

Thermoelectric generators (TEGs) convert waste heat to electricity and are a leading contender for improving energy efficiency at a range of scales. Ideal TE materials show a large Seebeck effect,...

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