A practical field guide to thermoelectrics: Fundamentals, synthesis, and characterization

Zevalkink, Alex; Smiadak, David M.; Blackburn, Jeffrey L.; Ferguson, Andrew J.; Chabinyc, Michael L.; Delaire, Olivier; Wang, Jian; Kovnir, Kirill; Martin, Joshua; Schelhas, Laura T.; Sparks, Taylor D.; Kang, Stephen Dongmin; Dylla, Maxwell; Snyder, G. Jeffrey; Ortiz, Brenden R.; Toberer, Eric S.

doi:10.1063/1.5021094

Cited by 235 publications

(241 citation statements)

References 253 publications

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“…On the other hand, as the Fermi level moves deeper into the bands, charge carriers below the Fermi level compensate the entropy transported by carriers above the Fermi level. This decreases the Seebeck coefficient, which represents the average entropy carried per charge carrier . The position of the Fermi level depends upon the carrier concentration, which can be easily measured.…”

Section: Intrinsic Defects and Carrier Concentrationmentioning

confidence: 99%

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Cagnoni

Cojocaru‐Mirédin

et al. 2019

Adv Funct Materials

166

203

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Thermoelectric materials have attracted significant research interest in recent decades due to their promising application potential in interconverting heat and electricity. Unfortunately, the strong coupling between the material parameters that determine thermoelectric efficiency, i.e., the Seebeck coefficient, electrical conductivity, and thermal conductivity, complicates the optimization of thermoelectric energy converters. Main‐group chalcogenides provide a rich playground to alleviate the interdependence of these parameters. Interestingly, only a subgroup of octahedrally coordinated chalcogenides possesses good thermoelectric properties. This subgroup is also characterized by other outstanding characteristics suggestive of an exceptional bonding mechanism, which has been coined metavalent bonding. This conclusion is further supported by a map that separates different bonding mechanisms. In this map, all octahedrally coordinated chalcogenides with good performance as thermoelectrics are located in a well‐defined region, implying that the map can be utilized to identify novel thermoelectrics. To unravel the correlation between chemical bonding mechanism and good thermoelectric properties, the consequences of this unusual bonding mechanism on the band structure are analyzed. It is shown that features such as band degeneracy and band anisotropy are typical for this bonding mechanism, as is the low lattice thermal conductivity. This fundamental understanding, in turn, guides the rational materials design for improved thermoelectric performance by tailoring the chemical bonding mechanism.

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Section: Intrinsic Defects and Carrier Concentrationmentioning

confidence: 99%

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Cagnoni

Cojocaru‐Mirédin

et al. 2019

Adv Funct Materials

166

203

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“…The slight deviation of the Seebeck coefficient (Figure 2b) between the single crystal and polycrystalline samples is explained by the small difference in the carrier concentration (Figure 2c), which might come from the difference of actual content of Te dopant. To evaluate the electrical performance independent from carrier concentration, we further analyzed the weighted mobility [ 37–38 ] of the single crystals and polycrystalline samples obtained from the electrical conductivity and Seebeck coefficient measurements.…”

Section: Figurementioning

confidence: 99%

“…Higher weighted mobility corresponds to a higher power factor as well as higher zT , when the carrier concentration is optimized. [ 37–38 ] In contrast to the small difference in Seebeck coefficient, the improvement of electrical conductivity near room temperature is much more pronounced. This improvement in the electrical conductivity due to the elimination of grain boundary resistance results in a significant enhancement of the weighted mobility.…”

Section: Figurementioning

confidence: 99%

Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

et al. 2020

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Mg3(Sb,Bi)2 alloys have recently been discovered as a competitive alternative to the state‐of‐the‐art n‐type Bi2(Te,Se)3 thermoelectric alloys. Previous theoretical studies predict that single crystals Mg3(Sb,Bi)2 can exhibit higher thermoelectric performance near room temperature by eliminating grain boundary resistance. However, the intrinsic Mg defect chemistry makes it challenging to grow n‐type Mg3(Sb,Bi)2 single crystals. Here, the first thermoelectric properties of n‐type Te‐doped Mg3Sb2 single crystals, synthesized by a combination of Sb‐flux method and Mg‐vapor annealing, is reported. The electrical conductivity and carrier mobility of single crystals exhibit a metallic behavior with a typical T−1.5 dependence, indicating that phonon scattering dominates the charge carrier transport. The absence of any evidence of ionized impurity scattering in Te‐doped Mg3Sb2 single crystals proves that the thermally activated mobility previously observed in polycrystalline materials is caused by grain boundary resistance. Eliminating this grain boundary resistance in the single crystals results in a large enhancement of the weighted mobility and figure of merit zT by more than 100% near room temperature. This work experimentally demonstrates the accurate understanding of charge‐carrier scattering is crucial for developing high‐performance thermoelectric materials and indicates that single‐crystalline Mg3(Sb,Bi)2 solid solutions can exhibit higher zT compared to polycrystalline samples.

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“…The quality factor analysis is a good reference method to evaluate thermoelectric materials. [59,60] This quality factor B, which determines the zT versus η curve, is plotted in Figure S2 in the Supporting Information for each compound. This parameter reaches a maximum value of 0.38 for the Sr-filled skutterudite, predicting a zT close to unity if the chemical potential is modified correctly.…”

Section: Thermoelectric Transport Propertiesmentioning

confidence: 99%

Unveiling the Correlation between the Crystalline Structure of M‐Filled CoSb₃ (M = Y, K, Sr) Skutterudites and Their Thermoelectric Transport Properties

Gainza

Serrano‐Sánchez

Rodrigues

et al. 2020

Adv Funct Materials

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Skutterudite‐type pnictides based on CoSb3 are promising semiconductor materials for thermoelectric applications. An exhaustive structural characterization by synchrotron X‐ray powder diffraction of different M‐filled CoSb3 (M = Y, K, Sr, La, Ce, Yb) skutterudites, with a panoply of M atoms with very different chemical nature, allows to better understand the effects of filling from a crystallo‐chemical point of view. These analyses focus on the correlation of chemical and structural features with the enhanced thermoelectric properties displayed by certain families of filled‐CoSb3 skutterudites. These are mainly determined by Sb positional parameters, yielding Oftedal plots that depend on the filling fraction, ionic state, and atomic radius of the filler. Together with the distortion of [Sb4] rings and [CoSb6] octahedra present in the skutterudite structure, these results are linked to the band‐convergence concept and its influence on the thermoelectric transport properties. Here, the structural changes observed in the different chemical compositions are relevant to understand the improved thermoelectric performance of single partially filled n‐type skutterudites.

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A practical field guide to thermoelectrics: Fundamentals, synthesis, and characterization

Cited by 235 publications

References 253 publications

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Unveiling the Correlation between the Crystalline Structure of M‐Filled CoSb₃ (M = Y, K, Sr) Skutterudites and Their Thermoelectric Transport Properties

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A practical field guide to thermoelectrics: Fundamentals, synthesis, and characterization

Cited by 235 publications

References 253 publications

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Metallic n‐Type Mg3Sb2 Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Unveiling the Correlation between the Crystalline Structure of M‐Filled CoSb3 (M = Y, K, Sr) Skutterudites and Their Thermoelectric Transport Properties

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Metallic n‐Type Mg₃Sb₂ Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance

Unveiling the Correlation between the Crystalline Structure of M‐Filled CoSb₃ (M = Y, K, Sr) Skutterudites and Their Thermoelectric Transport Properties