Thermoelectric transport properties of CaMg<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>Bi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>, EuMg<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>Bi<mml:math xmlns:mml="http://www.w3.org/1998/Math/M

May, Andrew F.; McGuire, Michael A.; Singh, David J.; Ma, Jie; Delaire, Olivier; Huq, Ashfia; Cai, Wei; Wang, Hsin

doi:10.1103/physrevb.85.035202

Cited by 78 publications

(45 citation statements)

References 43 publications

(41 reference statements)

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“…Because of their structural similarity, the three com- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 In narrow band gap semiconductors at high temperatures and low carrier concentrations the minority carriers reduce the Seebeck coefficient and increase the electrical conductivity. 29 As both holes and electrons carry heat, the overall thermal conductivity increases. 30 These effects can be seen prominently in Figures 3 and 4 in the case of Ti 2 CO 2 because of its narrow band gap, whereas they are small for Zr 2 CO 2 and Hf 2 CO 2 .…”

Section: Resultsmentioning

confidence: 99%

Thermoelectric Performance of the MXenes M₂CO₂ (M = Ti, Zr, or Hf)

2016

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We present the first report in which the thermoelectric properties of two-dimensional MXenes are calculated by considering both the electron and phonon transport. Specifically, we solve the transport equations of the electrons and phonons for three MXenes, M 2 CO 2 , where M = Ti, Zr, or Hf, in order to evaluate the effect of the metal M on the thermoelectric performance. The lattice contribution to the thermal conductivity, obtained from the phonon life times, is found to be lowest in Ti 2 CO 2 and highest in Hf 2 CO 2 in the temperature range from 300 K to 700 K. The highest figure of merit is predicted for Ti 2 CO 2 . The heavy mass of the electrons due to flat conduction bands results in a larger thermopower in the case of n-doping in these compounds.

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Section: Resultsmentioning

confidence: 99%

Thermoelectric Performance of the MXenes M₂CO₂ (M = Ti, Zr, or Hf)

2016

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“…Such a high resistivity is not reasonable when considering the appearance of the 4d and 4f electrons in Eu (33). Inspired by our previous investigation on analogous Bi-based Zintl AMg 2 Bi 2 (A = Ca, Yb) phases, disordered (Ca,Yb, Eu)Mg 2 Bi 2 Zintl phases have been studied in this work.…”

Section: Significancementioning

confidence: 99%

“…Despite the extensive research on Zintl antimonides, analogous Bi-based Zintl materials have received little attention, even given the competitive TE performance of this system. For the CaAl 2 Si 2 -type Zintl phases, the crystal structures of both alkalineearth-based and rare-earth-based AMg 2 Bi 2 (A = Mg, Ca, Sr, Ba, Yb, Eu, Sm) have been reported (32)(33)(34). However, the reported ZT is ∼0.4 in YbMg 2 Bi 2 and ∼0.1 in CaMg 2 Bi 2 and EuMg 2 Bi 2 via melting, grinding, and annealing, not good enough for practical applications.…”

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confidence: 99%

Higher thermoelectric performance of Zintl phases (Eu _0.5 Yb _0.5 ) _1−x Ca _x Mg ₂ Bi ₂ by band engineering and strain fluctuation

Shuai

Geng

Lan

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

162

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Complex Zintl phases, especially antimony (Sb)-based YbZn 0.4 Cd 1.6 Sb 2 with figure-of-merit (ZT) of ∼1.2 at 700 K, are good candidates as thermoelectric materials because of their intrinsic "electron-crystal, phonon-glass" nature. Here, we report the rarely studied p-type bismuth (Bi)-based Zintl phases (Ca,Yb,Eu)Mg 2 Bi 2 with a record thermoelectric performance. Phase-pure EuMg 2 Bi 2 is successfully prepared with suppressed bipolar effect to reach ZT ∼ 1. Further partial substitution of Eu by Ca and Yb enhanced ZT to ∼1.3 for Eu 0.2 Yb 0.2 Ca 0.6 Mg 2 Bi 2 at 873 K. Density-functional theory (DFT) simulation indicates the alloying has no effect on the valence band, but does affect the conduction band. Such band engineering results in good p-type thermoelectric properties with high carrier mobility. Using transmission electron microscopy, various types of strains are observed and are believed to be due to atomic mass and size fluctuations. Point defects, strain, dislocations, and nanostructures jointly contribute to phonon scattering, confirmed by the semiclassical theoretical calculations based on a modified Debye-Callaway model of lattice thermal conductivity. This work indicates Bi-based (Ca, Yb,Eu)Mg 2 Bi 2 is better than the Sb-based Zintl phases. technology that converts heat into electricity, is currently used in subsea and spacecraft (1), and is foreseen to play an important role in the power industry and automobiles (2-5). Widespread applications are currently limited as a result of the low efficiency of TE materials (6). TE efficiency depends on the Carnot term as well as the TE figure-of-merit, ZT, defined as ZT = (S 2 σ/κ)T, where S, σ, κ, and T are the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively. S 2 σ is known as the power factor (PF) (7). Even though PF can be enhanced by electronic structure engineering, and κ can be reduced by an increase in phonon scattering, it is very difficult to independently increase PF and simultaneously decrease κ because they are oppositely related to carrier concentration and effective mass.As an alternative to evaluating the maximum ZT, a dimensionless material parameter B at particular temperature has proven to be useful (8-10).where m*, m 0 , μ, κ Lat , and T are the carrier effective mass, free electron mass, carrier mobility, lattice thermal conductivity, and absolute temperature, respectively. Therefore, heavy effective mass, high carrier mobility, and low lattice thermal conductivity are highly desirable for good TE performance. Practically, some strategies and concepts have been proposed to achieve this goal, e.g., band convergence and resonant states for heavier effective mass (11-13), band alignment and weak electron-phonon and alloy scattering to achieve high carrier mobility (14-16), and alloying or nanostructuring to enhance phonon scattering (17)(18)(19) (22,23), and A y Mo 3 Sb 7-x Te x (24). In particular, Zintl phases AB 2 Sb 2 (A = Ca, Yb, Eu, Sr; B = Zn, Mn, Cd, Mg) (25-29) crystalli...

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“…Indeed, as the layer and the interlayer spacing can often be modified independently, the possibility to transform and hopefully tune adequately the electronic and thermal transport properties is real. For instance, this has been proven in layered compounds crystallizing in the CaAl 2 Si 2 structure type [1][2][3][4][5], in the CdI 2 type structures [6][7][8][9], or in the parent misfits compounds [11][12][13]. The study of these layered compounds have shown that it is possible to somewhat decouple the thermal and electronic properties as, in a simple view, the crystalline layers primarily conduct the charge carriers whereas the thermal transport is mainly affected by the content of the interlayer spacing.…”

Section: Introductionmentioning

confidence: 99%

“…HRTEM image of the sample Cu 0.05 TiS 1.5 Se 0 5. showing the local disruption of the periodicity of the stacking of the TiX 2 layers.…”

mentioning

confidence: 99%

Tuned thermoelectric properties of TiS1.5Se0.5 through copper intercalation

Nunna

Gascoin

Guilmeau

2015

Journal of Alloys and Compounds

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Thermoelectric transport properties of CaMg2Bi2, EuMg2Bi
Andrew F. May
¹
,
Michael A. McGuire
²
,
David J. Singh
³

et al.

Cited by 78 publications

References 43 publications

Thermoelectric Performance of the MXenes M₂CO₂ (M = Ti, Zr, or Hf)

Thermoelectric Performance of the MXenes M₂CO₂ (M = Ti, Zr, or Hf)

Higher thermoelectric performance of Zintl phases (Eu _0.5 Yb _0.5 ) _1−x Ca _x Mg ₂ Bi ₂ by band engineering and strain fluctuation

Tuned thermoelectric properties of TiS1.5Se0.5 through copper intercalation

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Thermoelectric transport properties of CaMg2Bi2, EuMg2BiAndrew F. May1, Michael A. McGuire2, David J. Singh3 et al.

Cited by 78 publications

References 43 publications

Thermoelectric Performance of the MXenes M2CO2 (M = Ti, Zr, or Hf)

Thermoelectric Performance of the MXenes M2CO2 (M = Ti, Zr, or Hf)

Higher thermoelectric performance of Zintl phases (Eu 0.5 Yb 0.5 ) 1−x Ca x Mg 2 Bi 2 by band engineering and strain fluctuation

Tuned thermoelectric properties of TiS1.5Se0.5 through copper intercalation

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Thermoelectric transport properties of CaMg2Bi2, EuMg2Bi
Andrew F. May
¹
,
Michael A. McGuire
²
,
David J. Singh
³

et al.

Thermoelectric Performance of the MXenes M₂CO₂ (M = Ti, Zr, or Hf)

Thermoelectric Performance of the MXenes M₂CO₂ (M = Ti, Zr, or Hf)

Higher thermoelectric performance of Zintl phases (Eu _0.5 Yb _0.5 ) _1−x Ca _x Mg ₂ Bi ₂ by band engineering and strain fluctuation