Thermoelectric performance of NiyMo3Sb7−xTex (y≤0.1, 1.5≤x≤1.7)

Xu, Hongyi; Kleinke, Katja M.; Holgate, Tim C.; Zhang, H.; Su, Zhe; Tritt, Terry M.; Kleinke, Holger

doi:10.1063/1.3086641

Cited by 32 publications

(34 citation statements)

References 23 publications

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“…This rigid band shift is rationalized as the filling of holes by the extra d electrons of Te. Because of the slope in the eDOS, this shift of E F decreases the number of electronic states at the Fermi level (∼ 42%), in agreement with previous observations by Candolfi et al [16,44] and Xu et al [15]. This decrease in eDOS at Fermi level originates from d-states of Mo(12e), and p-states of Sb(12d), Sb(16f), and Te(12d) atoms, with the projected eDOS showing suppressions at the Fermi level of about ∼77%, respectively.…”

Section: B Bondingsupporting

confidence: 81%

Electron-phonon coupling and thermal transport in the thermoelectric compoundMo3Sb7−xTex

Bansal

Said

et al. 2015

Phys. Rev. B

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Phonon properties of Mo3Sb7−xTex (x = 0, 1.5, 1.7), a potential high-temperature thermoelectric material, have been studied with inelastic neutron and x-ray scattering, and with first-principles simulations. The substitution of Te for Sb leads to pronounced changes in the electronic structure, local bonding, phonon density of states (DOS), dispersions, and phonon lifetimes. Alloying with tellurium shifts the Fermi level upward, near the top of the valence band, resulting in a strong suppression of electron-phonon screening, and a large overall stiffening of interatomic forceconstants. The suppression in electron-phonon coupling concomitantly increases group velocities and suppresses phonon scattering rates, surpassing the effects of alloy-disorder scattering, and resulting in a surprising increased lattice thermal conductivity in the alloy. We also identify that the local bonding environment changes non-uniformly around different atoms, leading to variable perturbation strengths for different optical phonon branches. The respective roles of changes in phonon group velocities and phonon lifetimes on the lattice thermal conductivity are quantified. Our results highlight the importance of the electron-phonon coupling on phonon mean-free-paths in this compound, and also estimates the contributions from boundary scattering, umklapp scattering, and point-defect scattering.

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Section: B Bondingsupporting

confidence: 81%

Electron-phonon coupling and thermal transport in the thermoelectric compoundMo3Sb7−xTex

Bansal

Said

et al. 2015

Phys. Rev. B

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“…Theoretical calculations showed that partial substitution of Sb by Te elements would effectively shift the Fermi levels and then optimize the TE performance, which was confirmed by the experiments. 18,[22][23][24][25] High zT value of 0.8 at 1050 K was reported, making this material an outstanding candidate for high-temperature TE power generation. 18 However, it is not clear if higher performance would be achieved if the carrier concentration could be further reduced.…”

Section: Introductionmentioning

confidence: 99%

“…Attempts to reduce both the carrier concentration and the lattice thermal conductivity by filling with 3-d transition metals has shown to be largely unsuccessful. 22,23 Relatively accurate predictions might be accomplished with a thorough investigation of the transport properties in Mo 3 Sb 7Àx Te x compounds especially the high-temperature carrier scattering mechanism, combined with a model of the band structure, such as a single parabolic band model. 26 Moreover, for the thermal transport, the reason for the increased high-temperature lattice thermal conductivity after Te-doping is still unclear.…”

Section: Introductionmentioning

confidence: 99%

Optimized thermoelectric properties of Mo3Sb7−xTex with significant phonon scattering by electrons

Xiao-li

Pei

Snyder

et al. 2011

Energy Environ. Sci.

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Heavily doped compounds Mo 3 Sb 7Àx Te x (x ¼ 0, 1.0, 1.4, 1.8) were synthesized by solid state reaction and sintered by spark plasma sintering. Both X-ray diffraction and electron probe microanalysis indicated the maximum solubility of Te was around x ¼ 1.8. The trends in the electrical transport properties can generally be understood using a single parabolic band model, which predicts that the extremely high carrier concentration of Mo 3 Sb 7 ($10 22 cm À3 ) can be reduced to a nearly optimized level ($2 Â 10 21 cm À3 ) for thermoelectric figure of merit (zT) by Te-substitution with x ¼ 1.8. The increased lattice thermal conductivity by Te-doping was found to be due to the decreased Umklapp and electronphonon scattering, according to a Debye model fitting. The thermoelectric figure of merit (zT) monotonously increased with increasing temperature and reached its highest value of about 0.51 at 850 K for the sample with x ¼ 1.8, making these materials competitive with the state-of-the-art thermoelectric SiGe alloys. Evidence of significant electron-phonon scattering is found in the thermal conductivity.

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“…The complex Zintl phases, especially Sb-based Zintl compounds, have been demonstrated to be promising TE materials for middleto high-temperature applications. Remarkable achievements have been reported with maximal ZT around or more than 1, e.g., β-Zn 4 Sb 3 (20,21), Yb 14 Mn 1−x Al x Sb 11 (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)(26)(27)(28)(29) crystallizing in CaAl 2 Si 2 structure have been extensively studied with the highest ZT for YbZn 0.4 Cd 1.6 Sb 2 ∼ 1.2 at 700 K. The A sites of these materials have been shown to contain exclusively divalent ions, which are limited to alkalineearth-based and rare-earth-based elements like Eu and Yb, whereas B is a d 0 , d 5 , d 10 transition metal or a main-group element like Mg 2+ (30,31).…”

mentioning

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.

159

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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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Thermoelectric performance of NiyMo3Sb7−xTex (y≤0.1, 1.5≤x≤1.7)

Cited by 32 publications

References 23 publications

Electron-phonon coupling and thermal transport in the thermoelectric compoundMo3Sb7−xTex

Electron-phonon coupling and thermal transport in the thermoelectric compoundMo3Sb7−xTex

Optimized thermoelectric properties of Mo3Sb7−xTex with significant phonon scattering by electrons

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

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Thermoelectric performance of NiyMo3Sb7−xTex (y≤0.1, 1.5≤x≤1.7)

Cited by 32 publications

References 23 publications

Electron-phonon coupling and thermal transport in the thermoelectric compoundMo3Sb7−xTex

Electron-phonon coupling and thermal transport in the thermoelectric compoundMo3Sb7−xTex

Optimized thermoelectric properties of Mo3Sb7−xTex with significant phonon scattering by electrons

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

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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