scholarly journals Enhancing the thermoelectric figure of merit in engineered graphene nanoribbons

2015 ◽  
Vol 6 ◽  
pp. 1176-1182 ◽  
Author(s):  
Hatef Sadeghi ◽  
Sara Sangtarash ◽  
Colin J Lambert
Keyword(s):  
Thermoelectric Properties ◽  
Fermi Energy ◽  
Figure Of Merit ◽  
Graphene Nanoribbons ◽  
The Other ◽  
Monolayer Graphene ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Inner Surface ◽  
Current Flows

We demonstrate that thermoelectric properties of graphene nanoribbons can be dramatically improved by introducing nanopores. In monolayer graphene, this increases the electronic thermoelectric figure of merit ZT e from 0.01 to 0.5. The largest values of ZT e are found when a nanopore is introduced into bilayer graphene, such that the current flows from one layer to the other via the inner surface of the pore, for which values as high as ZT e = 2.45 are obtained. All thermoelectric properties can be further enhanced by tuning the Fermi energy of the leads.

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.

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.

Thermoelectric Properties of CoSb3-based Skutterudite Compounds

2010 ◽  
Vol 1267 ◽  
Author(s):  
Adul Harnwunggmoung ◽  
Ken Kurosaki ◽  
Hiroaki Muta ◽  
Shinsuke Yamanaka
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Filling Ratio ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Alloy Scattering ◽  
Skutterudite Compound

AbstractCoSb3 is known as a skutterudite compound that could exhibit high thermoelectric figure of merit. However, the thermal conductivity of CoSb3 is relatively high. In order to enhance the thermoelectric performance of this compound, we tried to reduce the thermal conductivity of CoSb3 by substitution of Rh for Co and by Tl-filling into the voids. The polycrystalline samples of (Co,Rh)Sb3 and Tl-filled CoSb3 were prepared and the thermoelectric properties such as the Seebeck coefficient, electrical resistivity, and thermal conductivity were measured in the temperature range from room temperature to 750 K. The Rh substitution for Co reduced the lattice thermal conductivity, due to the alloy scattering effect. The minimum value of the lattice thermal conductivity was 4 Wm-1K-1 at 750 K obtained for (Co0.7Rh0.3)Sb3. Also the lattice thermal conductivity rapidly decreased with increasing the Tl-filling ratio. T10.25Co4Sb12 exhibited the best ZT values; the maximum ZT was 0.9 obtained at 600 K.

Enhancement of thermoelectric figure of merit by incorporation of large single crystals in Ca3Co4O9 bulk materials

2003 ◽  
Vol 18 (7) ◽  
pp. 1646-1651 ◽  
Author(s):  
Ryoji Funahashi ◽  
Saori Urata ◽  
Toyohide Sano ◽  
Masaaki Kitawaki
Keyword(s):  
Electrical Conductivity ◽  
Composite Material ◽  
Single Crystals ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Bulk Materials ◽  
Flux Method ◽  
Thermoelectric Figure ◽  
Grain Alignment

Having recently succeeded in synthesizing large single crystals of (Ca2CoO3)CoO2 (Co-349) with superior thermoelectric properties using a modified flux method, we have prepared a composite material of Co-349 powder and single crystals and examined its thermoelectric properties. The electrical conductivity σ of this composite, which contained 20 wt.% single crystals, was higher than that of a sample without the single crystals. While the achievable effect has yet to be fully realized, improved grain alignment and the effect of current bypassing grain boundaries through the large single crystals in the composite are thought to cause the increasing σ, which consequently results in an enhanced thermoelectric figure of merit of about 0.56 at 973 K in air.

Thermoelectric Properties of a Wide–Gap Chalcopyrite Compound AgInSe2

2012 ◽  
Vol 519 ◽  
pp. 188-192 ◽  
Author(s):  
P.Z. Ying ◽  
H. Zhou ◽  
Y.L. Gao ◽  
Y.Y. Li ◽  
Y.P. Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Chemical Compositions ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Remarkable Improvement ◽  
Wide Gap ◽  
Chalcopyrite Compound

Here we report the thermoelectric properties of a wide–gap chalcopyrite compound AgInSe2, and observed the remarkable improvement in electrical conductivity σ, due to the bandgap (Eg = 1.12 eV) reduction compared to In2Se3. The improvement in σ is directly responsible for the enhancement of thermoelectric figure of merit ZT, though the thermal conductivity is much higher at 500 ~ 724 K. The maximum ZT value is 0.34 at 724 K, increasing by a factor of 4, indicating that this chalcopyrite compound is of a potential thermoelectric candidate if further optimizations of chemical compositions and structure are made.

Effect of Zn substitution at a Cu site on the transport behavior and thermoelectric properties in Cu3SbSe4

RSC Advances ◽  
2016 ◽  
Vol 6 (7) ◽  
pp. 5528-5534 ◽  
Author(s):  
Aparabal Kumar ◽  
P. Dhama ◽  
Deepash S. Saini ◽  
P. Banerji
Keyword(s):  
Thermal Conductivity ◽  
Beneficial Effect ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Transport Behavior ◽  
Zn Substitution

Zn substitution at Cu site in Cu3SbSe4 reduces the thermal conductivity giving beneficial effect to the thermoelectric figure of merit.

scholarly journals First-principles study of thermoelectric properties of Mg2Si–Mg2Pb semiconductor materials

RSC Advances ◽  
2018 ◽  
Vol 8 (31) ◽  
pp. 17168-17175 ◽  
Author(s):  
Tao Fan ◽  
Congwei Xie ◽  
Shiyao Wang ◽  
Artem R. Oganov ◽  
Laifei Cheng
Keyword(s):  
Thermoelectric Properties ◽  
Solid Solutions ◽  
First Principles ◽  
Figure Of Merit ◽  
Semiconductor Materials ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
First Principles Study

Thermoelectric figure of merit of Mg2Si1−xPbx solid solutions as a function of temperature.

scholarly journals The impact of charge transfer and structural disorder on the thermoelectric properties of cobalt intercalated TiS2

2016 ◽  
Vol 4 (9) ◽  
pp. 1871-1880 ◽  
Author(s):  
Gabin Guélou ◽  
Paz Vaqueiro ◽  
Jesús Prado-Gonjal ◽  
Tristan Barbier ◽  
Sylvie Hébert ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Charge Transfer ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Structural Disorder ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Low Levels ◽  
The Impact

The thermoelectric figure of merit of TiS2 is increased by 25% through the intercalation of low levels of cobalt due to an increased electrical conductivity, arising from charge transfer, and a reduced thermal conductivity resulting from disorder.

OPTIMIZATION OF THERMOELECTRIC PROPERTIES BY Cu SUBSTITUTION IN LaCoO3 CERAMICS

2014 ◽  
Vol 28 (09) ◽  
pp. 1450065 ◽  
Author(s):  
K. K. CHOUDHARY ◽  
N. KAURAV ◽  
S. K. GHOSH
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundaries ◽  
Thermoelectric Power ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Linear Temperature Dependence ◽  
Thermoelectric Figure ◽  
Linear Temperature ◽  
Cu Substitution

The thermoelectric properties of LaCo 1-x Cu x O 3-δ ceramics are theoretically analyzed, it is observed that thermoelectric figure of merit ZT ( = S2σT/κ) is maximized by Cu substitution in LaCo 1-x Cu x O 3-δ at x = 0.15. The lattice thermal conductivity (κ ph ) and phonon drag thermoelectric power [Formula: see text] were estimated by the scattering of phonons with defects, grain boundaries, electrons and phonon umklapp scattering to evaluate the thermoelectric figure of merit ZT. The Mott expression is used to estimate the electron diffusive thermoelectric power [Formula: see text] using Fermi energy as electron free parameter, [Formula: see text] shows linear temperature dependence. The electron contribution to thermal conductivity (κe) is estimated using temperature-dependent electron relaxation time. We found that Cu substitution increases the phonon scattering with grain boundaries and defects which significantly decrease the thermal conductivity and subsequently increase the thermoelectric power. The present numerical analysis of thermoelectric properties will help in designing more efficient thermoelectric materials for thermoelectric applications.

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