Increasing Efficiencies of Thermoelectric Devices Through Angular Interface Geometries

Thermoelectric Figure ◽

Subsequent Increase ◽

Acoustic Mismatch ◽

Out Of Plane ◽

Plane Direction

The phonon Boltzmann transport equation model is used to evaluate the reduction of out-of-plane thermal conductivity and subsequent increase in thermoelectric figure of merit when an angular interface is patterned between a germanium thin-film and silicon substrate. According to the acoustic mismatch model, the angular structure reduces the out-of-plane thermal conductivity by spatially redistributing phonons traveling in the out-of-plane direction. Simulation results demonstrate a 43% reduction in out-of-plane thermal conductivity when operating in the fully ballistic regime. This decrease in phononic thermal conductivity would result in an increase of intrinsic thermoelectric efficiency by a factor of 1.75.

Термоэлектрические свойства нанокомпозитного Bi-=SUB=-0.45-=/SUB=-Sb-=SUB=-1.55-=/SUB=-Te-=SUB=-2.985-=/SUB=- с микрочастицами SiO-=SUB=-2-=/SUB=-

Физика и техника полупроводников ◽

10.21883/ftp.2019.06.47721.30 ◽

2019 ◽

Vol 53 (6) ◽

pp. 751

Author(s):

А.А. Шабалдин ◽

П.П. Константинов ◽

Д.А. Курдюков ◽

Л.Н. Лукьянова ◽

А.Ю. Самунин ◽

...

Keyword(s):

Thermal Conductivity ◽

Solid Solution ◽

Electrical Conductivity ◽

Wide Temperature Range ◽

Figure Of Merit ◽

Nanostructured Material ◽

Thermoelectric Figure ◽

P Type

AbstractNanocomposite thermoelectrics based on Bi_0.45Sb_1.55Te_2.985 solid solution of p -type conductivity are fabricated by the hot pressing of nanopowders of this solid solution with the addition of SiO_2 microparticles. Investigations of the thermoelectric properties show that the thermoelectric power of the nanocomposites increases in a wide temperature range of 80–420 K, while the thermal conductivity considerably decreases at 80–320 K, which, despite a decrease in the electrical conductivity, leads to an increase in the thermoelectric efficiency in the nanostructured material without the SiO_2 addition by almost 50% (at 300 K). When adding SiO_2, the efficiency decreases. The initial thermoelectric fabricated without nanostructuring, in which the maximal thermoelectric figure of merit ZT = 1 at 390 K, is most efficient at temperatures above 350 K.

Pseudo-Superlattices of Bi2Te3 Topological Insulator Films with Enhanced Thermoelectric Performance

MRS Proceedings ◽

10.1557/opl.2011.1361 ◽

2011 ◽

Vol 1344 ◽

Author(s):

V. Goyal ◽

D Teweldebrhan ◽

A.A. Balandin

Keyword(s):

Thin Films ◽

Thermal Conductivity ◽

Topological Insulator ◽

Figure Of Merit ◽

Room Temperature ◽

Laser Flash ◽

Thermoelectric Figure ◽

Surface Transport ◽

Film Thinning

ABSTRACTIt was recently suggested theoretically that atomically thin films of Bi2Te3 topological insulators have strongly enhanced thermoelectric figure of merit. We used the “graphene-like” exfoliation process to obtain Bi2Te3 thin films. The films were stacked and subjected to thermal treatment to fabricate pseudo-superlattices of single crystal Bi2Te3 films. Thermal conductivity of these structures was measured by the “hot disk” and “laser flash” techniques. The room temperature in-plane and cross-plane thermal conductivity of the stacks decreased by a factor of ∼2.4 and 3.5 respectively as compared to that of bulk. The strong decrease of thermal conductivity with preserved electrical properties translates to ∼140-250% increase in the thermoelectric figure if merit. It is expected that the film thinning to few-quintuples, and tuning of the Fermi level can lead to the topological insulator surface transport regime with the theoretically predicted extraordinary thermoelectric efficiency.

Nanocomposite of Bi2Te3 with Metal Inclusions for Advanced Thermoelectric Applications

MRS Proceedings ◽

10.1557/proc-1218-z05-11 ◽

2009 ◽

Vol 1218 ◽

Author(s):

Sumithra Santhanam ◽

Nathan J. Takas ◽

Dinesh Misra ◽

Pierre F. P. Poudeu ◽

Kevin L. Stokes

Keyword(s):

Thermal Conductivity ◽

Figure Of Merit ◽

Electrical Power ◽

Nanometer Scale ◽

Experimental And Theoretical Studies

Thermoelectric Figure ◽

Thermal And Electrical Properties ◽

AbstractRecent experimental and theoretical studies have shown that the thermal to electrical power conversion efficiency (as measured by the thermoelectric figure of merit) can be enhanced in nanocomposite materials. Primarily, these efforts to improve the thermoelectric efficiency rely on reducing the lattice thermal conductivity through nanostructuring of the materials or the introduction of a second nanometer-scale phase into the composite material. Here, we show that the inclusion of semimetal nanoparticles into bismuth telluride (Bi2Te3) can result in both an increase in the electronic transport properties (so called "power factor") as well as a decrease in lattice thermal conductivity. The effect of different volume fractions of Bi nanoinclusions (3% and 5%) on the thermal and electrical properties of the composite are reported. A marginal increase in the thermoelectric figure of merit is achieved for 3% metal nanoinclusion, whereas a significant improvement in the figure of merit could be achieved for 5% nanoinclusions in the Bi2Te3 thermoelectric matrix.

Ultralow lattice thermal conductivity of chalcogenide perovskite CaZrSe3 contributes to high thermoelectric figure of merit

npj Computational Materials ◽

10.1038/s41524-019-0253-5 ◽

2019 ◽

Vol 5 (1) ◽

Author(s):

Eric Osei-Agyemang ◽

Challen Enninful Adu ◽

Ganesh Balasubramanian

Keyword(s):

Thermal Conductivity ◽

Figure Of Merit ◽

Density Functional ◽

Phonon Scattering ◽

Mean Free Path ◽

Boltzmann Transport ◽

Phonon Modes ◽

Thermoelectric Figure

AbstractAn emerging chalcogenide perovskite, CaZrSe3, holds promise for energy conversion applications given its notable optical and electrical properties. However, knowledge of its thermal properties is extremely important, e.g. for potential thermoelectric applications, and has not been previously reported in detail. In this work, we examine and explain the lattice thermal transport mechanisms in CaZrSe3 using density functional theory and Boltzmann transport calculations. We find the mean relaxation time to be extremely short corroborating an enhanced phonon–phonon scattering that annihilates phonon modes, and lowers thermal conductivity. In addition, strong anharmonicity in the perovskite crystal represented by the Grüneisen parameter predictions, and low phonon number density for the acoustic modes, results in the lattice thermal conductivity to be limited to 1.17 W m−1 K−1. The average phonon mean free path in the bulk CaZrSe3 sample (N → ∞) is 138.1 nm and nanostructuring CaZrSe3 sample to ~10 nm diminishes the thermal conductivity to 0.23 W m−1 K−1. We also find that p-type doping yields higher predictions of thermoelectric figure of merit than n-type doping, and values of ZT ~0.95–1 are found for hole concentrations in the range 1016–1017 cm−3 and temperature between 600 and 700 K.

Improving the Thermoelectric Properties of the Material and Increasing the Efficiency of Conversion Processes

Nano- i Mikrosistemnaya Tehnika ◽

10.17587/nmst.23.243-246 ◽

2021 ◽

Vol 23 (5) ◽

pp. 243-246

Author(s):

D.G. Mustafaeva ◽

Keyword(s):

Thermal Conductivity ◽

Electrical Conductivity ◽

Thermoelectric Properties ◽

Figure Of Merit ◽

Mean Free Path ◽

Charge Carriers ◽

Thermoelectric Figure ◽

Phonon Component

The area of practical application of thermoelectric materials depends on the value of the thermoelectric figure of merit. The use of semiconductor materials makes it possible to realize the conditions under which the ratio of their parameters ensures the achievement of high values of thermoelectric figure of merit. The achievement of the maximum thermoelectric figure of merit causes an increase in the efficiency of conversion processes due to the improvement of the thermoelectric properties of the material. The position of the maximum value of the thermoelectric figure of merit is predetermined by the scattering parameters and the ratio of the mobilities and effective masses of charge carriers. The nature of the change in electrical conductivity is determined by the behavior of the concentration of charge carriers. Thermal conductivity, like electrical conductivity, is proportional to the concentration of electrons and the mean free path. An increase in thermoelectric efficiency is achieved by optimizing thermoelectric parameters by doping and improving the properties of com¬pounds, which leads to an optimization of the concentration of charge carriers, a change in the density of states, and a decrease in the phonon component of thermal conductivity. The improvement of the thermoelectric properties of the material and the increase in the efficiency of the conversion processes are provided at a certain concentration of charge carriers, which corresponds to the optimal value.

Ultralow lattice thermal conductivity at room temperature in 2D KCuSe from first-principles calculations

Physical Chemistry Chemical Physics ◽

10.1039/d1cp04657h ◽

2021 ◽

Author(s):

Zhiyuan Xu ◽

Cong Wang ◽

Xuming Wu ◽

Lei Hu ◽

Yuqi Liu ◽

...

Keyword(s):

Thermal Conductivity ◽

First Principles ◽

Figure Of Merit ◽

Room Temperature ◽

Transport Theory ◽

First Principles Calculations ◽

Boltzmann Transport ◽

Thermoelectric Figure ◽

Boltzmann Transport Theory

Ultralow lattice thermal conductivity is crucial to achieve a high thermoelectric figure of merit for thermoelectric applications. In this work, using the first-principles and phonon Boltzmann transport theory, we investigate...

Influence of multi-sintering on the thermoelectric properties of Bi2Sr2Co2Oy ceramics

Modern Physics Letters B ◽

10.1142/s0217984920500190 ◽

2019 ◽

Vol 34 (02) ◽

pp. 2050019 ◽

Cited By ~ 2

Author(s):

Y. Zhang ◽

M. M. Fan ◽

C. C. Ruan ◽

Y. W. Zhang ◽

X.-J. Li ◽

...

Keyword(s):

Thermal Conductivity ◽

Thermoelectric Properties ◽

Figure Of Merit ◽

Phonon Scattering ◽

Sintered Sample ◽

Thermoelectric Figure ◽

The Third ◽

Ceramic Samples ◽

Optimum Formula

[Formula: see text] ceramic samples have a structure similar to phonon glass electronic crystals, and their thermoelectric properties can be effectively adjusted through repeated grinding and sintering. The results show that multi-sintering can make their grain refined and increase their grain boundary, which will effectively increase density and phonon scattering. Finally, multi-sintering can reduce the resistivity and thermal conductivity, thus obviously improve thermoelectric figure of merit [Formula: see text] of [Formula: see text]. The optimum [Formula: see text] value of 0.26 is achieved at 923 K by the third sintered sample.

Effects of Ce filling fraction and Fe content on the thermoelectric properties of Co-rich CeyFexCo4−xSb12

Journal of Materials Research ◽

10.1557/jmr.2001.0109 ◽

2001 ◽

Vol 16 (3) ◽

pp. 837-843 ◽

Cited By ~ 66

Author(s):

Xinfeng Tang ◽

Lidong Chen ◽

Takashi Goto ◽

Toshio Hirai

Keyword(s):

Thermal Conductivity ◽

Thermoelectric Properties ◽

Figure Of Merit ◽

Single Phase ◽

Hole Concentration ◽

Thermoelectric Figure ◽

Filling Fraction ◽

Fe Content

Single-phase filled skutterudite compounds, CeyFexCo4−xSb12 (x = 0 to 3.0, y = 0 to 0.74), were synthesized by a melting method. The effects of Fe content and Ce filling fraction on the thermoelectric properties of CeyFexCo4−xSb12 were investigated. The lattice thermal conductivity of Ce-saturated CeyFexCo4−xSb12, y being at the maximum corresponding to x, decreased with increasing Fe content (x) and reached its minimum at about x = 1.5. When x was 1.5, lattice thermal conductivity decreased with increasing Ce filling fraction till y = 0.3 and then began to increase after reaching the minimum at y = 0.3. Hole concentration and electrical conductivity of Cey Fe1.5Co2.5Sb12 decreased with increasing Ce filling fraction. The Seebeck coefficient increased with increasing Ce filling fraction. The greatest dimensionless thermoelectric figure of merit T value of 1.1 was obtained at 750 K for the composition of Ce0.28Fe1.52Co2.48Sb12.

ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, MEMS and NEMS: Volume 1 ◽

Thermal Conductivity Reduction in Few-Layer Graphene

10.1115/ipack2011-52245 ◽

2011 ◽

Author(s):

Dhruv Singh ◽

Jayathi Y. Murthy ◽

Timothy S. Fisher

Keyword(s):

Thermal Conductivity ◽

Weak Coupling ◽

Phonon Scattering ◽

Single Layer ◽

Acoustic Mode ◽

Single Layer Graphene ◽

Boltzmann Transport ◽

Layer Graphene ◽

Out Of Plane ◽

Few Layer Graphene

Using the linearized Boltzmann transport equation and perturbation theory, we analyze the reduction in the intrinsic thermal conductivity of few-layer graphene sheets accounting for all possible three-phonon scattering events. Even with weak coupling between layers, a significant reduction in the thermal conductivity of the out-of-plane acoustic modes is apparent. The main effect of this weak coupling is to open many new three-phonon scattering channels that are otherwise absent in graphene. The highly restrictive selection rule that leads to a high thermal conductivity of ZA phonons in single-layer graphene is only weakly broken with the addition of multiple layers, and ZA phonons still dominate thermal conductivity. We also find that the decrease in thermal conductivity is mainly caused by decreased contributions of the higher-order overtones of the fundamental out-of-plane acoustic mode. Moreover, the extent of reduction is largest when going from single to bilayer graphene and saturates for four layers. The results compare remarkably well over the entire temperature range with measurements of of graphene and graphite.

Thermoelectric Properties of Semiconducting Intermetallic Compounds: FeGa3and RuGa3

MRS Proceedings ◽

10.1557/proc-793-s8.38 ◽

2003 ◽

Vol 793 ◽

Author(s):

Y. Amagai ◽

A. Yamamoto ◽

C. H. Lee ◽

H. Takazawa ◽

T. Noguchi ◽

...

Keyword(s):

Thermal Conductivity ◽

Electrical Resistivity ◽

High Temperature ◽

Seebeck Coefficient ◽

Transport Properties ◽

Figure Of Merit ◽

Room Temperature ◽

Thermoelectric Figure ◽

High Seebeck Coefficient

ABSTRACTWe report transport properties of polycrystalline TMGa3(TM = Fe and Ru) compounds in the temperature range 313K<T<973K. These compounds exhibit semiconductorlike behavior with relatively high Seebeck coefficient, electrical resistivity, and Hall carrier concentrations at room temperature in the range of 1017- 1018cm−3. Seebeck coefficient measurements reveal that FeGa3isn-type material, while the Seebeck coefficient of RuGa3changes signs rapidly from large positive values to large negative values around 450K. The thermal conductivity of these compounds is estimated to be 3.5Wm−1K−1at room temperature and decreased to 2.5Wm−1K−1for FeGa3and 2.0Wm−1K−1for RuGa3at high temperature. The resulting thermoelectric figure of merit,ZT, at 945K for RuGa3reaches 0.18.