An Extensive Theoretical Study of the Phonon Conductivity and Thermoelectric Properties of SiGe Alloys

2012 ◽  
Vol 1404 ◽  
Author(s):  
Iowerth O. Thomas ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Density Functional ◽  
Theoretical Study ◽  
Phonon Dispersion ◽  
Perturbation Scheme ◽  
Thermoelectric Figure ◽  
Anharmonic Potential ◽  
Group Velocities ◽  
Phonon Dispersion Relations

ABSTRACTWe present an extensive theoretical study of the phonon conductivity and thermoelectric properties of SiGe alloys. Phonon dispersion relations and group velocities – required for conductivity calculations – are obtained by employing the density-functional-perturbation scheme. The cubic anharmonic potential has been expressed by treating the Gr¨uneisen constant as a semi-adjustable mode-averaged parameter. Calculations are also performed, within the nearly-free-electron approximation, for the temperature variation of the Fermi energy, Seebeck coefficient, electrical conductivity, and electronic polar and bipolar contributions to thermal conductivity. Results are compared with experimental measurements for n-doped pressure-sintered Si0.754Ge0.246 alloy. Using these results, we compare our results for the thermoelectric figure-of-merit with previously reported results based on an empirical approach for phonon conductivity.

scholarly journals Impurity Substitution Enhances Thermoelectric Figure of Merit in Zigzag Graphene Nanoribbons

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Saeideh Ramezani Akbarabadi ◽  
Mojtaba Madadi Asl
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Simultaneous Increase ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Zigzag Graphene Nanoribbons

The thermoelectric properties of zigzag graphene nanoribbons (ZGNRs) are sensitive to chemical modification. In this study, we employed density functional theory (DFT) combined with the nonequilibrium green’s function (NEGF) formalism to investigate the thermoelectric properties of a ZGNR system by impurity substitution of single and double nitrogen (N) atoms into the edge of the nanoribbon. N-doping changes the electronic transmission probability near the Fermi energy and suppresses the phononic transmission. This results in a modified electrical conductance, thermal conductance, and thermopower. Ultimately, simultaneous increase of the thermopower and suppression of the electron and phonon contributions to the thermal conductance leads to the significant enhancement of the figure of merit in the perturbed (i.e., doped) system compared to the unperturbed (i.e., nondoped) system. Increasing the number of dopants not only changes the nature of transport and the sign of thermopower but also further suppresses the electron and phonon contributions to the thermal conductance, resulting in an enhanced thermoelectric figure of merit. Our results may be relevant for the development of ZGNR devices with enhanced thermoelectric efficiency.

Enhancement of the thermoelectric figure of merit in DNA-like systems induced by Fano and Dicke effects

2015 ◽  
Vol 17 (16) ◽  
pp. 11077-11087 ◽  
Author(s):  
Hua-Hua Fu ◽  
Lei Gu ◽  
Dan-Dan Wu ◽  
Zu-Quan Zhang
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Theoretical Study ◽  
Thermoelectric Figure Of Merit ◽  
Dna Molecules ◽  
Thermoelectric Figure ◽  
Synthetic Dna

We report a theoretical study highlighting the thermoelectric properties of biological and synthetic DNA molecules.

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

2019 ◽  
Vol 34 (02) ◽  
pp. 2050019 ◽  
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 Of Merit ◽  
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

2001 ◽  
Vol 16 (3) ◽  
pp. 837-843 ◽  
Author(s):  
Xinfeng Tang ◽  
Lidong Chen ◽  
Takashi Goto ◽  
Toshio Hirai
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Single Phase ◽  
Lattice Thermal Conductivity ◽  
Hole Concentration ◽  
Thermoelectric Figure Of Merit ◽  
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.

Stokes’ first problem for an electro-conducting micropolar fluid with thermoelectric properties

2010 ◽  
Vol 88 (1) ◽  
pp. 35-48 ◽  
Author(s):  
Magdy A. Ezzat ◽  
Hamdy M. Youssef
Keyword(s):  
Thermoelectric Properties ◽  
Micropolar Fluid ◽  
Inversion Formula ◽  
Figure Of Merit ◽  
Fourier Expansion ◽  
Fourier Transforms ◽  
Heat Sources ◽  
Layer Model ◽  
Thermoelectric Figure ◽  
Coupled Equations

This work is related to the flow of an electro-conducting micropolar fluid presenting thermoelectric properties effect in the presence of a magnetic field. The electro-conducting thermofluid equation of heat transfer with one relaxation time is derived. The flow of an electro-conducting micropolar fluid over a plate that is moved suddenly is considered. The governing coupled equations in the frame of the boundary-layer model are applied to Stokes' first problem with heat sources. Laplace-transform and Fourier-transform techniques are used to obtain the solution. The inverses of the Fourier transforms are obtained analytically. The Laplace transforms are obtained using the complex inversion formula of the transform together with Fourier-expansion techniques. Numerical results for the temperature distribution, the velocity, and the microrotation components are represented graphically. Thermoelectric figure-of-merit, Seebeck and Peltier effects on a micropolar fluid are studied.

Thermoelectric Transport Properties of SrTiO3 Doped with Pm

2018 ◽  
Vol 280 ◽  
pp. 3-8 ◽  
Author(s):  
A. A. Adewale ◽  
Abdullah Chik ◽  
R. Mohd Zaki ◽  
F. Che Pa ◽  
Yeoh Chow Keat ◽  
...  
Keyword(s):  
Transport Properties ◽  
Figure Of Merit ◽  
Density Functional ◽  
Generalized Gradient ◽  
Thermoelectric Figure ◽  
Functional Theory ◽  
Thermoelectric Transport ◽  
Generalized Gradient Approximation ◽  
High Contribution ◽  
Thermoelectric Transport Properties

Thermoelectric properties of SrTiO3doped with 8%Pm at Sr site were investigated using density functional theory and generalized gradient approximation. The transport properties were calculated based on BoltzTraP code at temperature range 300-1200K. In electronic properties study Fermi level were shifted to conduction band region due to high contribution 4f orbital in Pm. Present study thermoelectric figure of merit ZT result was 0.395 at 300K and 0.638 at 1200K. This shows a considerably good value of ZT for SrTiO3as n-type oxide. Compared to previous work, ZT were at the range of 0.21 - 0.37 for temperature of 300-1000K in Pr, La, Ta and Ho.

Epitaxial Growth and Thermoelectric Properties of Bi2Te3 Based Low Dimensional Structures

2000 ◽  
Vol 626 ◽  
Author(s):  
Joachim Nurnus ◽  
Harald Beyer ◽  
Armin Lambrecht ◽  
Harald Böttner
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Lattice Mismatch ◽  
Structural Performance ◽  
Lead Chalcogenide ◽  
Thermoelectric Figure ◽  
Barrier Materials ◽  
Superlattice Structures ◽  
Low Dimensional ◽  
Secondary Ion

ABSTRACTBi2Te3 based low dimensional structures are interesting material systems to increase the thermoelectric figure of merit ZT by either the expected reduction of the thermal conductivity or by a possible power factor enhancement due to quantum confinement. Due to low lattice mismatch Bi2(Te1-xSex)3, PbSe1-xTex, as well as Pb1-xSrxTe, and BaF2 are suitable for Bi2Te3 based low dimensional structures. Especially due to their significantly enhanced band gap lead chalcogenide compounds like Pb1-xSrxTe (Pb0.87Sr0.13Te: 0.6 eV) are well-suited barrier materials in MQW structures. Alternatively the insulator BaF2 can be used for that purpose.Here we report mainly on results of different superlattice structures mentioned above grown by molecular beam epitaxy (MBE) on BaF2(111). The structural properties of these layers were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and secondary ion mass spectroscopy (SIMS). Structural performance and thermoelectric properties of different Bi2Te3 based superlattices were reported and compared with regard to their superlattice parameters.

Influence of Encapsulation of Fullerenes on Optical and Thermoelectric Properties of Carbon Nanotubes

2021 ◽  
Vol 26 (2) ◽  
pp. 123-131
Author(s):  
E.V. Morozova ◽  
◽  
D.A. Timkaeva ◽  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
C60 Fullerene ◽  
Zone Structure ◽  
Thermoelectric Figure ◽  
High Frequencies ◽  
The One ◽  
Coefficients Of Absorption

The hybrid systems based on the carbon nanotubes (CNT) and fullerenes (nanopipodes) are promising for applications in nanoelectronics. With insignificant variation of the CNT diameter the change of the fullerenes geometry takes place. The periodically located inside fullerenes represent a set of quantum points in the one-dimensional super-lattice. Using the variation of inside fullerenes it is possible to modulate the zone structure of the CNT – fullerene system and to control the electronic and phonon characteristics of nanopipodes. In the work the optical and thermoelectric properties of CNT with encapsulated molecules of C60 fullerene have been investigated. Using the first-principle methods the coefficients of absorption, optical conductivi-ty, thermal conductivity, thermoelectric figure of merit for CNT with fullerenes, periodically lo-cated inside the nanotubes at different distances from each other, have been calculated. It has been shown that with decreasing the distance between fullerenes the optical conductivity of CNT – C60 is suppressed at high frequencies. It has been determined that the conductance of the structures with fullerenes is less than the conductance of a clean tube, and approximately equal for considered distances (12.3 and 19.7 Å) between fullerenes. The CNT thermal conductivity due to the encapsulation of fullerenes considerably (3–4 times) decreases for the considered CNT (8.8) – C60 systems.

scholarly journals Enhanced Thermoelectric Properties of WS2/Single-Walled Carbon Nanohorn Nanocomposites

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 140 ◽  
Author(s):  
Ji Hoon Kim ◽  
Seunggun Yu ◽  
Sang Won Lee ◽  
Seung-Yong Lee ◽  
Keun Soo Kim ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
High Frequency ◽  
Figure Of Merit ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
Carbon Nanohorns ◽  
Single Walled Carbon ◽  
High Frequency Induction

Recently, two-dimensional tungsten disulfide (WS2) has attracted attention as a next generation thermoelectric material due to a favorable Seebeck coefficient. However, its thermoelectric efficiency still needs to be improved due to the intrinsically low electrical conductivity of WS2. In the present study, thermoelectric properties of WS2 hybridized with highly conductive single-walled carbon nanohorns (SWCNHs) were investigated. The WS2/SWCNH nanocomposites were fabricated by annealing the mixture of WS2 and SWCNHs using a high-frequency induction heated sintering (HFIHS) system. By adding SWCNHs to WS2, the nanocomposites exhibited increased electrical conductivity and a slightly decreased Seebeck coefficient with the content of SWCNHs. Hence, the maximum power factor of 128.41 μW/mK2 was achieved for WS2/SWCNHs with 0.1 wt.% SWCNHs at 780 K, resulting in a significantly improved thermoelectric figure of merit (zT) value of 0.027 compared to that of pristine WS2 with zT 0.017.

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