The effect of phonon‐grain boundary scattering on the lattice thermal conductivity and thermoelectric conversion efficiency of heavily doped fine‐grained, hot‐pressed silicon germanium alloy

1981 ◽  
Vol 52 (12) ◽  
pp. 7421-7426 ◽  
Author(s):  
D. M. Rowe ◽  
V. S. Shukla
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Conversion Efficiency ◽  
Silicon Germanium ◽  
Lattice Thermal Conductivity ◽  
Boundary Scattering ◽  
Fine Grained ◽  
Thermoelectric Conversion ◽  
Germanium Alloy ◽  
Heavily Doped

Fundamental insight into control of thermal conductivity in silicon-germanium alloy nanowires

2014 ◽  
Vol 1707 ◽  
Author(s):  
Yongjin Lee ◽  
Gyeong S. Hwang
Keyword(s):  
Thermal Conductivity ◽  
Silicon Germanium ◽  
Nonequilibrium Molecular Dynamics ◽  
Boundary Scattering ◽  
Alloy Scattering ◽  
Scattering Effect ◽  
Germanium Alloy ◽  
Alloy Nanowires ◽  
Fundamental Insight ◽  
Insight Into

ABSTRACTWe present a computational analysis of thermal transport in Silicon-Germanium alloy nanowires (SiGeNWs), particularly focusing on the relative roles of alloy scattering and boundary scattering to the significant reduction of thermal conductivity (κ). Our nonequilibrium molecular dynamics (NEMD) simulations confirm the strong dependence of κ on Si:Ge ratio, as observed in previous experimental studies. Interestingly, as the amount of impurity increases, the difference in κ between SiGe bulk and SiGeNW becomes smaller. Especially, κSiGeNW and κSiGe have similar κ values when the Ge content is 20-80 %. From a nonequilibrium Green’s function (NEGF)-density functional theory (DFT) analysis, it is suggested that the most reduction in transmission channels is attributed to the strong alloy scattering effect for both Si0.8Ge0.2 bulk and Si0.8Ge0.2 NW. The boundary scattering effect in the SiGe alloy system seems to be unimportant as alloy scattering is dominant. The improved understanding provides fundamental insight into how to modify Si-based materials to enhance their thermoelectric (TE) properties through nanostructuring and alloying.

Thermal Conductivity of N-Type Si-Ge

1991 ◽  
Vol 234 ◽  
Author(s):  
Paul G. Klfmens
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
Electronic Conductivity ◽  
Boundary Scattering ◽  
Low Frequencies ◽  
Free Carriers ◽  
Anharmonic Interactions ◽  
Debye Frequency

ABSTRACTThe lattice thermal conductivity of 80-20 Si-Ge is treated theoretically for the case of the Fermi energy positioned for optimum figure of merit. The spectral distribution of the lattice conductivity is limited by anharmonic interactions, by the randomness of the Si-Ge lattice and, at low frequencies, by the interaction with free carriers and neutral donors. The two latter processes dominate over grain boundary scattering. The spectral conductivity is sharply peaked around 0.1 of the Debye frequency. A further reduction in lattice conductivity can be obtained by small insulating inclusions. This is partially offset by a reduction in electronic conductivity, but results in some improvement in the figure of merit.

scholarly journals Attaining Low Lattice Thermal Conductivity in Half-Heusler Sublattice Solid Solutions: Which Substitution Site Is Most Effective?

2022 ◽  
Vol 3 (1) ◽  
pp. 1-14
Author(s):  
Rasmus Tranås ◽  
Ole Martin Løvvik ◽  
Kristian Berland
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Solid Solutions ◽  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Parent Compound ◽  
Combined Effect ◽  
Boundary Scattering ◽  
Heusler Compounds ◽  
Grain Boundary Scattering

Low thermal conductivity is an important materials property for thermoelectricity. The lattice thermal conductivity (LTC) can be reduced by introducing sublattice disorder through partial isovalent substitution. Yet, large-scale screening of materials has seldom taken this opportunity into account. The present study aims to investigate the effect of partial sublattice substitution on the LTC. The study relies on the temperature-dependent effective potential method based on forces obtained from density functional theory. Solid solutions are simulated within a virtual crystal approximation, and the effect of grain-boundary scattering is also included. This is done to systematically probe the effect of sublattice substitution on the LTC of 122 half-Heusler compounds. It is found that substitution on the three different crystallographic sites leads to a reduction of the LTC that varies significantly both between the sites and between the different compounds. Nevertheless, some common criteria are identified as most efficient for reduction of the LTC: The mass contrast should be large within the parent compound, and substitution should be performed on the heaviest atoms. It is also found that the combined effect of sublattice substitution and grain-boundary scattering can lead to a drastic reduction of the LTC. The lowest LTC of the current set of half-Heusler compounds is around 2 W/Km at 300 K for two of the parent compounds. Four additional compounds can reach similarly low LTC with the combined effect of sublattice disorder and grain boundaries. Two of these four compounds have an intrinsic LTC above ∼15 W/Km, underlining that materials with high intrinsic LTC could still be viable for thermoelectric applications.

LATTICE THERMAL CONDUCTIVITY IN A HOLLOW SILICON NANOWIRE

2005 ◽  
Vol 19 (06) ◽  
pp. 1017-1027 ◽  
Author(s):  
WEI-QING HUANG ◽  
KE-QIU CHEN ◽  
Z. SHUAI ◽  
LINGLING WANG ◽  
WANGYU HU
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Lattice Thermal Conductivity ◽  
Silicon Nanowire ◽  
Boundary Scattering ◽  
Phonon Confinement ◽  
Time Approximation ◽  
Si Nanowire ◽  
Scattering Mechanisms ◽  
Relaxation Time Approximation

We theoretically investigate the lattice thermal conductivity of a hollow Si nanowire under the relaxation time approximation. The results show that the thermal conductivity in such structure is decreased markedly below the bulk value due to phonon confinement and boundary scattering. The thermal conductivities under different scattering mechanisms are given, and it is found that the boundary scattering is dominant resistive process for the decrease of the thermal conductivity.

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