scholarly journals Lattice thermal conductivity in isotope diamond asymmetric superlattices

2021 ◽  
Author(s):  
Hsu Kai Weng ◽  
Akira NAGAKUBO ◽  
Hideyuki Watanabe ◽  
Hirotsugu OGI
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Group Velocity ◽  
Lattice Thermal Conductivity ◽  
Trade Off ◽  
Number Of Layers ◽  
Phonon Group Velocity ◽  
Wide Range ◽  
Superlattice Structures ◽  
Superlattice Period

Abstract We study lattice thermal conductivity of isotope diamond superlattices consisting of 12C and 13C diamond layers at various superlattice periods. It is found that the thermal conductivity of a superlattice is significantly deduced from that of pure diamond because of the reduction of the phonon group velocity near the folded Brillouin zone. The results show that asymmetric superlattices with different number of layers of 12C and 13C diamonds exhibit higher thermal conductivity than symmetric superlattices even with the same superlattice period, and we find that this can be explained by the trade-off between the effects of phonon specific heat and phonon group velocity. Furthermore, impurities and imperfect superlattice structures are also found to significantly reduce the thermal conductivity, suggesting that these effects can be exploited to control the thermal conductivity over a wide range.

Enhanced thermoelectric performance in PbTe-based superlattice structures from reduction of lattice thermal conductivity

2005 ◽  
Vol 87 (2) ◽  
pp. 023105 ◽  
Author(s):  
J. C. Caylor ◽  
K. Coonley ◽  
J. Stuart ◽  
T. Colpitts ◽  
R. Venkatasubramanian
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Thermoelectric Performance ◽  
Superlattice Structures

scholarly journals A Computational Survey of Semiconductors for Power Electronics

2019 ◽  
Author(s):  
Prashun Gorai ◽  
Robert McKinney ◽  
Nancy Haegel ◽  
Andriy Zakutayev ◽  
Vladan Stevanovic
Keyword(s):  
Thermal Conductivity ◽  
Power Electronics ◽  
Figure Of Merit ◽  
Large Scale ◽  
Lattice Thermal Conductivity ◽  
Consumer Products ◽  
Breakdown Field ◽  
Experimental Investigations ◽  
Wide Range ◽  
Screening Parameter

Power electronics (PE) are used to control and convert electrical energy in a wide range of applications from consumer products to large-scale industrial equipment. While Si-based power devices account for the vast majority of the market, wide band gap semiconductors such as SiC, GaN, and Ga2O3 are starting to gain ground. However, these emerging materials face challenges due to either non-negligible defect densities, or high synthesis and processing costs, or poor thermal properties. Here, we report on a broad computational survey aimed to identify promising materials for future power electronic devices beyond SiC, GaN, and Ga2O3. We consider 863 oxides, sulfides, nitrides, carbides, silicides, and borides that are reported in the crystallographic database and exhibit finite calculated band gaps. We utilize ab initio methods in conjunction with models for intrinsic carrier mobility, and critical breakdown field to compute the widely used Baliga figure of merit. We also compute the lattice thermal conductivity as a screening parameter. In addition to correctly identifying known PE materials, our survey has revealed a number of promising candidates exhibiting the desirable combination of high figure of merit and high lattice thermal conductivity, which we propose for further experimental investigations.

Two-channel model for ultralow thermal conductivity of crystalline Tl3VSe4

Science ◽  
2018 ◽  
Vol 360 (6396) ◽  
pp. 1455-1458 ◽  
Author(s):  
Saikat Mukhopadhyay ◽  
David S. Parker ◽  
Brian C. Sales ◽  
Alexander A. Puretzky ◽  
Michael A. McGuire ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Random Walk ◽  
Specific Heat ◽  
Thermal Barrier Coatings ◽  
Lattice Thermal Conductivity ◽  
Channel Model ◽  
Disordered Materials ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Transport Component

Solids with ultralow thermal conductivity are of great interest as thermal barrier coatings for insulation or thermoelectrics for energy conversion. However, the theoretical limits of lattice thermal conductivity (κ) are unclear. In typical crystals a phonon picture is valid, whereas lowest κ values occur in highly disordered materials where this picture fails and heat is supposedly carried by random walk among uncorrelated oscillators. Here we identify a simple crystal, Tl3VSe4, with a calculated phonon κ [0.16 Watts per meter-Kelvin (W/m-K)] one-half that of our measured κ (0.30 W/m-K) at 300 K, approaching disorder κ values, although Raman spectra, specific heat, and temperature dependence of κ reveal typical phonon characteristics. Adding a transport component based on uncorrelated oscillators explains the measured κ and suggests that a two-channel model is necessary for crystals with ultralow κ.

Strain engineering of phonon thermal transport properties in monolayer 2H-MoTe2

2017 ◽  
Vol 19 (47) ◽  
pp. 32072-32078 ◽  
Author(s):  
Aamir Shafique ◽  
Young-Han Shin
Keyword(s):  
Thermal Conductivity ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Boltzmann Transport Equation ◽  
Strain Engineering ◽  
First Principles Calculations ◽  
Boltzmann Transport ◽  
Phonon Group Velocity ◽  
Phonon Lifetime ◽  
Phonon Properties

The effect of strain on the phonon properties such as phonon group velocity, phonon anharmonicity, phonon lifetime, and lattice thermal conductivity of monolayer 2H-MoTe2is studied by solving the Boltzmann transport equation based on first principles calculations.

Umklapp collisions and thermal conductivity

2021 ◽  
pp. 309-321
Author(s):  
Geoffrey Brooker
Keyword(s):  
Thermal Conductivity ◽  
Heat Conduction ◽  
Heat Flow ◽  
Group Velocity ◽  
Thermodynamic Equilibrium ◽  
Reciprocal Lattice ◽  
Reciprocal Lattice Vector ◽  
Momentum Balance ◽  
Lattice Vector ◽  
Phonon Group Velocity

“Umklapp collisions and thermal conductivity” deals with heat conduction in a dielectric solid. Collisions of phonons are divided into Umklapp and normal according as a reciprocal lattice vector is or is not involved in the phonon momentum balance. A local temperature is defined by appeal to local thermodynamic equilibrium. An equilibrium phonon distribution can be off-centred, yet non-decaying, if the only collisions are “normal”, conserving the total phonon momentum. Then heat flow does not decay, even if a representative collision reverses the phonon group velocity. Conversely, in an Umklapp collision it is the non-conservation of phonon momentum that causes heat flow to decay.

scholarly journals Lattice Thermal Conductivity of Some Copper Alloys

1957 ◽  
Vol 10 (4) ◽  
pp. 454 ◽  
Author(s):  
WRG Kemp ◽  
PG Klemens ◽  
RJ Tainsh
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Copper Alloys ◽  
Solute Content ◽  
Zinc Alloys ◽  
Conduction Electrons ◽  
Wide Range ◽  
Electrical Conductivities ◽  
Copper Gold ◽  
Copper Zinc

The thermal and electrical conductivities of three copper-zinc alloys annealed at high temperatures, and of two copper-gold alloys, were measured over a wide range of low temperatures, and their lattice component of thermal conductivity was deduced in the range 2?90 �K. It appears that the high lattice thermal resistance at liquid helium temperatures previously found in copper-zinc alloys is a function of solute content rather than of concentration of conduction electrons and that this resistance can be reduced by high-temperature annealing.

Experimental Investigation of Molten Salt Nanofluid for Solar Thermal Energy Application

2011 ◽  
Author(s):  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Molten Salts ◽  
Solar Power ◽  
Solar Thermal ◽  
Wide Range

The overall efficiency of a Concentrated Solar Power (CSP) system is critically dependent on the thermo-physical properties of the Thermal Energy Storage (TES) components and the Heat Transfer Fluid (HTF). Higher operating temperatures in CSP result in enhanced thermal efficiency of the thermodynamic cycles that are used in harnessing solar energy (e.g., using Rankine cycle or Stirling cycle). Particlularly, high specific heat capacity (Cp) and high thermal conductivity (k) of the HTF and TES materials enable reduction in the size and overall cost of solar power systems. However, only a limited number of materials are compatible for the high operating temperature requirements (exceeding 400°C) envisioned for the next generation of CSP systems. Molten salts have a wide range of melting point (200°C∼500°C) and are thermally stable up to 700°C. However, thermal property values of the molten salts are typically quite low (Cp is typically less than ∼2J/g-K and k is typically less than ∼1 W/m-K). To obviate these issues the molten salts can be doped with nanoparticles — resulting in the synthesis / formation of nanomaterials (nanocomposites and nanofluids). Nanofluids are colloidal suspensions formed by doping with minute concentration of nanoparticles. Nanofluids were reported for anomalous enhancement in their thermal conductivity values. In this study, molten salt-based nanofluids were synthesized by liquid solution method. A differential scanning calorimeter (DSC) was used to measure the specific heat capacity values of the proposed nanofluids. The observed enhancement in specific heat is then compared with predictions from conventional thermodynamic models (e.g. thermal equilibrium model or “simple mixing rule”). Transmission Electron Microscopy (TEM) is used to verify that minimal aggregation of nanoparticles occurred before and after the thermocycling experiments. Thermocycling experiments were conducted for repeated measurements of the specific heat capacity by using multiple freeze-thaw cycles of the nanofluids/ nano-composites, respectively. This study demonstrates the feasibility for using novel nanomaterials as high temperature nanofluids for applications in enhancing the operational efficiencies as well as reducing the cost of electricity produced in solar thermal systems utilizing CSP in combination with TES.

Analytical Model for Lattice Thermal Conductivity Predictions of Periodic Nanoporous Structures

2016 ◽  
Author(s):  
Qing Hao ◽  
Yue Xiao ◽  
Hongbo Zhao
Keyword(s):  
Thermal Conductivity ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Lattice Thermal Conductivity ◽  
Phonon Transport ◽  
Kinetic Relationship ◽  
Wide Range ◽  
Edge Scattering ◽  
Bulk Phonon ◽  
Nanoporous Structures

Phonon transport within nanoporous bulk materials or thin films is of importance to applications in thermoelectrics, gas sensors, and thermal insulation materials. Considering classical phonon size effects, the lattice thermal conductivity KL can be predicted assuming diffusive pore-edge scattering of phonons and bulk phonon mean free paths. In the kinetic relationship, kL can be computed by modifying the phonon mean free paths with the characteristic length ΛPore of the porous structure. Despite some efforts using the Monte Carlo ray tracing method to extract ΛPore, the resulting KL often diverges from that predicted by phonon Monte Carlo simulations. In this work, the effective ΛPore is extracted by directly comparing the predictions by the kinetic relationship and phonon Monte Carlo simulations. The investigation covers a wide range of period sizes and volumetric porosities. In practice, these ΛPore values can be used for thermal analysis of general nanoporous materials.

THE EFFECT OF SPONTANEOUS AND PIEZOELECTRIC POLARIZATION ON THERMAL CONDUCTIVITY OF InN

2013 ◽  
Vol 27 (09) ◽  
pp. 1350031 ◽  
Author(s):  
BIJAYA KUMAR SAHOO ◽  
SUSANT KUMAR SAHOO ◽  
SUKDEV SAHOO
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Group Velocity ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Polarization Property ◽  
Optical And Electrical Properties ◽  
High Quality ◽  
Phonon Group Velocity ◽  
Debye Frequency

The spontaneous (SP) and piezoelectric (PZ) polarization present in the wurtzite III nitrides influence the optical and electrical properties of these materials. The effects of SP and PZ polarization on thermal properties of III nitrides have yet to be investigated. Here we have investigated the SP and PZ effects on thermal conductivity of InN . Inclusion of polarization property modifies the group velocity of phonons. The combined phonon scattering rates and thermal conductivity k of InN are calculated using modified phonon group velocity, Debye frequency and Debye temperature. Without SP and PZ polarization, the room temperature thermal conductivity of InN is found to be 132.55 W/m.K. Inclusion of SP and PZ polarization property enhances the room temperature thermal conductivity from 132.55 to 134.32 W/m.K. Our predicted thermal conductivity values are closer to the recent experimental value 120 W/m.K measured by Levander et al. for a high quality irradiated InN films at room temperature.

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