Synthesis and high thermoelectric efficiency of Zintl phase YbCd2−xZnxSb2

Wang, Xiaojun; Tang, Mingfang; Chen, Hao‐Hong; Yang, Xinxin; Zhao, Jing‐Tai; Burkhardt, Ulrich; Grin, Yuri

doi:10.1063/1.3040321

Cited by 156 publications

(156 citation statements)

References 14 publications

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“…8A). Such a ZT value is competitive with the reported Sb-based p-type Zintl phases (22,26,27,50) and even other good p-type skutterudites (51) and half-Heuslers (52) in this temperature range (Fig. 8B).…”

Section: Methodsmentioning

confidence: 60%

“…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). 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.…”

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confidence: 99%

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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

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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Section: Methodsmentioning

confidence: 60%

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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“…Besides the filled skutterudites and diamond-like compounds, many Zintl compounds are another type of structure with a well-defined conductive network, in this case composed of the polyanion sublattice. [75][76][77][78] Theoretical description of electrical transport and challenges So far, we have reviewed three topics concerning the electrical transport: band engineering; scattering engineering; and conductive networks in complex compounds. The first two are primarily aimed at the power-factor enhancement by the manipulations on either the band structure or the carrier scattering.…”

Section: Manipulation Of Carrier Scatteringmentioning

confidence: 99%

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

et al. 2016

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During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon-phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions. INTRODUCTION Thermoelectric (TE) materials are materials that can generate useful electric potentials when subjected to a temperature gradient (known as the Seebeck effect). Conversely, they also transfer heat against the temperature gradient when a current is driven against this potential (known as the Peltier effect). They are promising energy materials with many applications, such as waste heat harvesting, radioisotope TE power generation, and solid state Peltier refrigeration, all of which are driving growing research interest. A key challenge is to improve the TE properties in order to obtain more efficient energy conversion and in turn enable new practical applications. Good TE materials must have excellent electrical transport properties, measured by the TE power factor ( = S 2 σ, where S is the Seebeck coefficient and σ is the electrical conductivity), and also a very low thermal conductivity κ (composed of the electronic contribution κ e , the lattice contribution κ L , and the bipolar contribution κ bi ). Combining the two aspects gives us the dimensionless figure of merit ZT,

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“…16 and 18) and YbCd 2Àx Zn x Sb 2 , both of which have zT values above unity at high temperatures. 11,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Recently, Yb 9 Mn 4.2 Sb 9 was shown to have promising thermoelectric performance (zT ¼ 0.7 at 950 K) by Bux et al 17 The structure of Yb 9 M 4+x Sb 9 is shown in Fig. 1, where M can be Fig.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric properties of the Yb₉Mn_4.2−xZn_xSb₉solid solutions

et al. 2014

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a Yb 9 Mn 4.2 Sb 9 has been shown to have extremely low thermal conductivity and a high thermoelectric figure of merit attributed to its complex crystal structure and disordered interstitial sites. Motivated by previous work which shows that isoelectronic substitution of Mn by Zn leads to higher mobility by reducing spin disorder scattering, this study investigates the thermoelectric properties of the solid solution, Yb 9 Mn 4.2Àx Zn x Sb 9 (x ¼ 0, 1, 2, 3 and 4.2). Measurements of the Hall mobility at high temperatures (up to 1000 K) show that the mobility can be increased by more than a factor of 3 by substituting Zn into Mn sites. This increase is explained by the reduction of the valence band effective mass with increasing Zn, leading to a slightly improved thermoelectric quality factor relative to Yb 9 Mn 4.2 Sb 9 . However, increasing the Zn-content also increases the p-type carrier concentration, leading to metallic behavior with low Seebeck coefficients and high electrical conductivity. Varying the filling of the interstitial site in Yb 9 Zn 4+y Sb 9 (y ¼ 0.2, 0.3, 0.4 and 0.5) was attempted, but the carrier concentration ($10 21 cm À3 at 300 K) and Seebeck coefficients remained constant, suggesting that the phase width of Yb 9 Zn 4+y Sb 9 is quite narrow.

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Synthesis and high thermoelectric efficiency of Zintl phase YbCd2−xZnxSb2

Cited by 156 publications

References 14 publications

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

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

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

Thermoelectric properties of the Yb₉Mn_4.2−xZn_xSb₉solid solutions

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Synthesis and high thermoelectric efficiency of Zintl phase YbCd2−xZnxSb2

Cited by 156 publications

References 14 publications

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

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

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

Thermoelectric properties of the Yb9Mn4.2−xZnxSb9solid solutions

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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

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

Thermoelectric properties of the Yb₉Mn_4.2−xZn_xSb₉solid solutions