Zintl Chemistry for Designing High Efficiency Thermoelectric Materials

Toberer, Eric S.; May, Andrew F.; Snyder, G. Jeffrey

doi:10.1021/cm901956r

Cited by 612 publications

(506 citation statements)

References 117 publications

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“…As a consequence, the thermal conductivity of skutterudites and clathrates can be reduced greatly while maintaining the electrical conductivity at a high level. Zintl compounds [7] with a large unit cell, including Yb 14 MnSb 11 , Yb 11 GaSb 9 , Ca 11 GaSb 9 and SrZnSb 2 have also been revealed to possess an intrinsically low lattice thermal conductivity due to the high fraction of low-velocity optical phonon modes [8]. In research on low-dimensional material systems, Dresselhaus et al [9] suggested that the power factor (α 2 σ) can be enhanced through the use of quantumconfi nement eff ects.…”

Section: Review Articlementioning

confidence: 99%

High-performance nanostructured thermoelectric materials

et al. 2010

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T he conversion of thermal energy to electrical energy is known as thermoelectric (TE) conversion. Th e TE eff ect can be used for both power generation and electronic refrigeration. When a temperature gradient (ΔT ) is applied to a TE couple consisting of n-type (electron-transporting) and p-type (hole-transporting) elements, the mobile charge carriers at the hot end tend to diff use to the cold end, producing an electrostatic potential (ΔV ). Th is characteristic, known as the Seebeck eff ect, where α = ΔV/ΔT is defi ned as the Seebeck coeffi cient, is the basis of TE power generation, as shown in Figure 1(a). Conversely, when a voltage is applied to a TE couple, the carriers attempt to return to the electron equilibrium that existed before the current was applied by absorbing energy at one connector and releasing it at the other, an eff ect known as the Peltier eff ect, as shown in Figure 1(b). Th ermoelectric technology and solid-state devices based on the TE eff ect have a number of advantages, including having no moving parts, and being reliable and scalable. Th e technology has therefore arouse worldwide interest in many fi elds, including waste heat recovery and solar heat utilization (power generation mode), and temperature-controlled seats, portable picnic coolers and thermal management in microprocessors (active refrigeration mode) [1].Th e effi ciency of TE devices is strongly associated with the dimensionless fi gure of merit (ZT) of TE materials, defi ned as ZT = (α 2 σ/κ)T, where σ, κ and T are the electrical resistivity, thermal conductivity and absolute temperature [2]. High electrical conductivity (corresponding to low Joule heating), a large Seebeck coeffi cient (corresponding to large potential diff erence) and low thermal conductivity (corresponding to a large temperature diff erence) are therefore necessary in order to realize high-performance TE materials. Th e ZT fi gure is also a very convenient indictor for evaluating the potential effi ciency of TE devices. In general, good TE materials have a ZT value of close to unity. However, ZT values of up to three are considered to be essential for TE energy converters that can compete on effi ciency with mechanical power generation and active refrigeration.High-performance TE materials have been pursued since Bi 2 Te 3 -based alloys were discovered in the 1960s. Until the end of last century, moderate progress had been made in the development of TE materials. Th e benchmark of ZT ≈ 1 was broken in the mid-1990s by two Tsinghua University, China Thermoelectric eff ects enable direct conversion between thermal and electrical energy and provide an alternative route for power generation and refrigeration. Over the past ten years, the exploration of high-performance thermoelectric materials has attracted great attention from both an academic research perspective and with a view to industrial applications. This review summarizes the progress that has been made in recent years in developing thermoelectric materials with a high dimensionless fi gure of...

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Section: Review Articlementioning

confidence: 99%

High-performance nanostructured thermoelectric materials

et al. 2010

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“…2,3 In particular, they benefit from extremely low lattice thermal conductivity resulting from their complex unit cells, 4 and their electronic properties can often be finely tuned using chemical substitutions. Excellent thermoelectric performance (zT > 1) has been demonstrated in several Zintl phases, 5 including Yb 14 MnSb 11 and YbZn 2−xCd x Sb 2 . 6,7 Many more Zintl phases, though not yet optimized for thermoelectric applications, appear to be promising candidates.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric Properties and Electronic Structure of the Zintl‐Phase Sr₃AlSb₃

et al. 2013

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The Zintl phase Sr 5 Al 2 Sb 6 has a large, complex unit cell and is composed of relatively earth-abundant and non-toxic elements, making it an attractive candidate for thermoelectric applications. The structure of Sr 5 Al 2 Sb 6 is characterized by infinite oscillating chains of AlSb 4 tetrahedra. It is distinct from the structure type of the previously studied Ca 5 M 2 Sb 6 compounds (M = Al, Ga or In), all of which have been shown to have promising thermoelectric performance. The lattice thermal conductivity of Sr 5 Al 2 Sb 6 (∼0.55 W mK −1 at 1000 K) was found to be lower than that of the related Ca 5 M 2 Sb 6 compounds due to its larger unit cell (54 atoms per primitive cell). Density functional theory predicts a relatively large band gap in Sr 5 Al 2 Sb 6 , in agreement with the experimentally determined band gap of E g ∼ 0.5 eV. High temperature electronic transport measurements reveal high resistivity and high Seebeck coefficients in Sr 5 Al 2 Sb 6 , consistent with the large band gap and valence-precise structure. Doping with Zn 2+ on the Al 3+ site was attempted, but did not lead to the expected increase in carrier concentration. The low lattice thermal conductivity and large band gap in Sr 5 Al 2 Sb 6 suggest that, if the carrier concentration can be increased, thermoelectric performance comparable to that of Ca 5 Al 2 Sb 6 could be achieved in this system.

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“…[1][2][3] The TE performance of a material is characterized by its dimensionless thermoelectric figure of merit ZT = S 2 T/ρκ, where S is the Seebeck coefficient, T the absolute temperature, ρ the electrical resistivity, and κ the total thermal conductivity. Great effort has been expended in materials research and optimization utilizing the concepts of phonon-glass electron-crystal compounds (PGEC), [4][5][6] nano-inclusion materials, 7,8 and investigating compounds with complex crystal structures 9,10 with the goal of achieving high ZT TE materials.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric properties and investigations of low thermal conductivity in Ga-doped Cu2GeSe3

et al. 2011

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In this study, we have synthesized a series of low thermal conductivity diamond-like materials with the general formula Cu 2 Ga x Ge 1-x Se 3 for 0 ≤ x ≤ 0.1, and their transport properties were evaluated to establish their suitability for TE based waste heat recovery applications. We report results for the Seebeck coefficient (S), electrical resistivity (ρ), thermal conductivity (κ), Hall coefficient (R H ), crystal structure, and elastic properties of Cu 2 Ga x Ge 1-x Se 3 for x = 0.01, 0.03, 0.05, 0.07 and 0.1. Powder x-ray diffraction revealed that a small amount of a related cubic polymorph appeared along with the orthorhombic parent phase at high Ga concentrations. This cubic phase is related to the parent phase in that both contain three-dimensional tetrahedral diamond-like substructures. All samples showed positive values of S and R H over the entire temperature range studied, indicative of p-type charge carriers. The largest value of S = 446 μVK -1 was observed at 745 K for undoped Cu 2 GeSe 3 . With increasing Ga content, both S and ρ decreased. Low values of κ were observed for all samples with the lowest value of κ = 0.67 W m -1 K -1 at 745 K for undoped Cu 2 GeSe 3 . This value approaches the theoretical minimum thermal conductivity for these materials at high temperatures. Although this diamondlike material has highly symmetric, lower coordination number tetrahedral bonding, an unusually large Grüneisen parameter (γ), a measure of bonding anharmonicity, was observed for Cu 2 Ga 0.1 Ge 0.9 Se 3 . A value of γ = 1.7 was calculated from the measured values of the elastic properties, heat capacity, and volume thermal expansion. Given the fact that all materials investigated have similar elastic property values and likely comparable coefficients of thermal expansion we surmise that this large Grüneisen parameter is a general feature for this material system. We conclude that this high level of anharmonicity gives rise to enhanced phononphonon scattering that is, in addition to the scattering brought about by the disordered structure, resulting in very low values of thermal conductivity.

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Zintl Chemistry for Designing High Efficiency Thermoelectric Materials

Cited by 612 publications

References 117 publications

High-performance nanostructured thermoelectric materials

High-performance nanostructured thermoelectric materials

Thermoelectric Properties and Electronic Structure of the Zintl‐Phase Sr₃AlSb₃

Thermoelectric properties and investigations of low thermal conductivity in Ga-doped Cu2GeSe3

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Zintl Chemistry for Designing High Efficiency Thermoelectric Materials

Cited by 612 publications

References 117 publications

High-performance nanostructured thermoelectric materials

High-performance nanostructured thermoelectric materials

Thermoelectric Properties and Electronic Structure of the Zintl‐Phase Sr3AlSb3

Thermoelectric properties and investigations of low thermal conductivity in Ga-doped Cu2GeSe3

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Thermoelectric Properties and Electronic Structure of the Zintl‐Phase Sr₃AlSb₃