Anderson Localization of Phonons in Random Multilayer Thin Films

2012 ◽  
Vol 1404 ◽  
Author(s):  
Anthony Frachioni ◽  
Bruce White
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Anderson Localization ◽  
Lattice Thermal Conductivity ◽  
Waste Heat ◽  
Mean Free Path ◽  
The United States ◽  
Energy Scavenging ◽  
Multilayer Thin Films

ABSTRACT1020 Joules of energy are generated by the United States each year; 60% of this energy is lost to waste heat [1]. Thermoelectric based energy scavenging has tremendous potential for the recovery of significant quantities of this waste heat. However, utilization of thermoelectric devices is limited due to relatively low energy conversion efficiency and the utilization of relatively scarce materials. This work focuses on generating sustainable and efficient thermoelectric materials through modifications to the lattice vibrations of materials with excellent thermoelectric electronic properties (Seebeck coefficients larger than 500 μV/K). In particular, Anderson localization of phonons in random multilayer thin films has been explored as a means for reducing lattice thermal conductivity to values approaching that of aerogels (∼10 mW/m-K). Silicon has been a sample of choice due to its high crust abundance and Seebeck coefficient. Reverse non-equilibrium molecular dynamics simulations have been utilized to determine the thermal conductivity of structures of interest. Simulations with pure Lennard-Jones argon solids have been performed to establish a methodology and to characterize the effect of different kinds of disorder prior to the examination of silicon. The simulation results indicate that mass disorder confined to randomly selected planes to be an effective way in which to reduce lattice thermal conductivity with the lattice thermal conductivity decreasing by a factor of thirty (to 4 mW/m-K) in the argon case and a factor of over ten thousand (to 15 mW/m-K) for silicon. Based on models in which the charge carrier mean free path is limited by scattering from the planes with mass disorder, the mobility of silicon is expected to reach values of 10 cm2/V-s. At this mobility the thermoelectric figure of merit, ZT, (utilizing the Wiedeman-Franz law to calculate the electronic thermal conductivity) varies between 4.5 and 11 as the mass ratio of the disordered planes is varied from 4 to 10 in 20% of the lattice planes. These results indicate that the pursuit of nanostructured thermoelectric materials in the form of random multilayers may provide a path to efficient and sustainable thermoelectric materials.

scholarly journals Improvement of Thermoelectric Properties through Reduction of Thermal Conductivity by Nanoparticle Addition and Stoichiometric Change to Mg2Si

MRS Advances ◽  
2017 ◽  
Vol 2 (58-59) ◽  
pp. 3637-3643
Author(s):  
William T. Yorgason ◽  
Arden N. Barnes ◽  
Nick Roberts
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Waste Heat ◽  
Mean Free Path ◽  
Phonon Transport ◽  
Thermoelectric Efficiency ◽  
Minimal Impact ◽  
Si Nanoparticle ◽  
Si Nanoparticles

ABSTRACT Thermoelectric materials have been of interest for several decades due to their ability to recapture waste heat of various systems and convert it to useful electricity. One method used to improve the thermoelectric efficiency of a material is to reduce the lattice thermal conductivity (k p ) while not affecting the other properties. In order to reduce the k p of the material, this paper introduces silicon (Si) nanoparticles (NPs) in Mg2Si to manipulate phonon scattering and mean free path. A series of simulations is performed with the metal silicide thermoelectric material MgxSix. The objective of this work is two-fold: 1) to determine the optimal Si nanoparticle (NP) concentration and 2) to determine the optimal MgxSix stoichiometry for minimizing the k p of the system. It should be noted, however, that the assumed reduction in thermal conductivity is only a result of reduced phonon transport and that minimal impact is made on the transport of electrons. Interestingly, the uniform off-stoichiometry (49.55 atomic percent (a/o) Si) sample of MgxSix resulted in a reduction of k p of 84.62 %, while the Si NP sample, with matching a/o Si, resulted in a reduction of k p of 78.82 %.

Ioffe–Regel limit and lattice thermal conductivity reduction of high performance (AgSbTe2)15(GeTe)85 thermoelectric materials

2014 ◽  
Vol 2 (9) ◽  
pp. 3251-3256 ◽  
Author(s):  
Tiejun Zhu ◽  
Hongli Gao ◽  
Yi Chen ◽  
Xinbing Zhao
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Free Path ◽  
Thermoelectric Materials ◽  
High Performance ◽  
Lattice Thermal Conductivity ◽  
State Of The Art ◽  
Mean Free Path ◽  
Lattice Parameter ◽  
Fine Grained

This work shows that the carrier mean free path of TAGS-85 thermoelectric materials is comparable to the lattice parameter, and that refining the grain size will not affect the mobility while benefiting the thermal conductivity reduction. A state-of-the-art ZT of ~ 1.6 is obtained for the fine-grained samples.

scholarly journals The effect of ultrasmall grain sizes on the thermal conductivity of nanocrystalline silicon thin films

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Battogtokh Jugdersuren ◽  
Brian T. Kearney ◽  
James C. Culbertson ◽  
Christopher N. Chervin ◽  
Michael B. Katz ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Grain Size ◽  
Thermoelectric Materials ◽  
Mass Density ◽  
Mean Free Path ◽  
Nanocrystalline Silicon ◽  
Density Fluctuations ◽  
Grain Sizes ◽  
Silicon Thin Films

AbstractNanocrystallization has been an important approach for reducing thermal conductivity in thermoelectric materials due to limits on phonon mean-free path imposed by the characteristic structural size. We report on thermal conductivity as low as 0.3 Wm−1K−1 of nanocrystalline silicon thin films prepared by plasma-enhanced chemical-vapor deposition as grain size is reduced to 2.8 nm by controlling hydrogen dilution of silane gas during growth. A multilayered film composed by alternating growth conditions, with layer thicknesses of 3.6 nm, is measured to have a thermal conductivity 30% and 15% lower than its two constituents. Our quantitative analysis attributes the strong reduction of thermal conductivity with decreasing grain size to the magnifying effect of porosity which occurs concomitantly due to increased mass density fluctuations. Our results demonstrate that ultrasmall grain sizes, multilayering, and porosity, all at a similar nanometer-size scale, may be a promising way to engineer thermoelectric materials.

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,...

scholarly journals The origin of the lattice thermal conductivity enhancement at the ferroelectric phase transition in GeTe

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Đorđe Dangić ◽  
Olle Hellman ◽  
Stephen Fahy ◽  
Ivana Savić
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Transitions ◽  
Thermoelectric Materials ◽  
Ferroelectric Phase Transition ◽  
Lattice Thermal Conductivity ◽  
Ferroelectric Phase ◽  
Structural Phase ◽  
High Symmetry ◽  
Structural Phase Transitions

AbstractThe proximity to structural phase transitions in IV-VI thermoelectric materials is one of the main reasons for their large phonon anharmonicity and intrinsically low lattice thermal conductivity κ. However, the κ of GeTe increases at the ferroelectric phase transition near 700 K. Using first-principles calculations with the temperature dependent effective potential method, we show that this rise in κ is the consequence of negative thermal expansion in the rhombohedral phase and increase in the phonon lifetimes in the high-symmetry phase. Strong anharmonicity near the phase transition induces non-Lorentzian shapes of the phonon power spectra. To account for these effects, we implement a method of calculating κ based on the Green-Kubo approach and find that the Boltzmann transport equation underestimates κ near the phase transition. Our findings elucidate the influence of structural phase transitions on κ and provide guidance for design of better thermoelectric materials.

Investigation of Thermoelectric Materials: Substitution effect of Bi on the Ag1-xPb18MTe20 (M = Sb, Bi) (x = 0, 0.14, 0.3)

2007 ◽  
Vol 1044 ◽  
Author(s):  
Mi-kyung Han ◽  
Huijun Kong ◽  
Ctirad Uher ◽  
Mercouri G Kanatzidis
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
Substitution Effect ◽  
Dimensionless Figure Of Merit ◽  
The Matrix ◽  
Mass Fluctuation

AbstractWe performed comparative investigations of the Ag1-xPb18MTe20 (M = Bi, Sb) (x = 0, 0.14, 0.3) system to better understand the roles of Sb and Bi on the thermoelectric properties. In both systems, the electrical conductivity nearly keeps the same values, while the Seebeck coefficient decreases dramatically in going from Sb to Bi. Compared to the lattice thermal conductivity of PbTe, that of AgPb18BiTe20 is substantially reduced. The lattice thermal conductivity of the Bi analog, however, is higher than that of AgPb18SbTe20 and this is attributed largely to the decrease in the degree of mass fluctuation between the nanostructures and the matrix (for the Bi analog). As a result the dimensionless figure of merit ZT of Ag1-xPb18MTe20 (M = Bi) is found to be smaller than that of Ag1-xPb18MTe20 (M = Sb).

Intrinsically Low Lattice Thermal Conductivity in Natural Superlattice (Bi2)m(Bi2Te3)n Thermoelectric Materials

2021 ◽  
Vol 33 (4) ◽  
pp. 1140-1148
Author(s):  
Hao Zhu ◽  
Chenchen Zhao ◽  
Pengfei Nan ◽  
Xiao-ming Jiang ◽  
Jiyin Zhao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Lattice Thermal Conductivity ◽  
Natural Superlattice

Metal phosphide CuP2 as a promising thermoelectric material: an insight from first-principles study

2021 ◽  
Author(s):  
Un-Gi Jong ◽  
Chol-Hyok Ri ◽  
Chol-Jin Pak ◽  
Chol-Hyok Kim ◽  
Stefaan Cottenier ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Material ◽  
Thermoelectric Materials ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Metal Phosphide ◽  
First Principles Study ◽  
Metal Phosphides ◽  
Large Lattice

In the search for better thermoelectric materials, metal phosphides have not been considered to be viable candidates so far, due to their large lattice thermal conductivity. Here we study thermoelectric...

scholarly journals Lattice Thermal Conductivity in Thermoelectric Materials

2019 ◽  
Vol 34 (3) ◽  
pp. 260 ◽  
Author(s):  
SHEN Jia-Jun ◽  
FANG Teng ◽  
FU Tie-Zheng ◽  
XIN Jia-Zhan ◽  
ZHAO Xin-Bing ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Lattice Thermal Conductivity
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