Low-Symmetry Rhombohedral GeTe Thermoelectrics

Li, Juan; Zhang, Xinyue; Chen, Zhiwei; Lin, Siqi; Li, Wen; Shen, Jiahong; Witting, Ian T.; Faghaninia, Alireza; Chen, Yue; Jain, Anubhav; Chen, Lidong; Snyder, G. Jeffrey; Pei, Yanzhong

doi:10.1016/j.joule.2018.02.016

Cited by 452 publications

(547 citation statements)

References 70 publications

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“…The medium temperature IV–VI compounds provide a playground to manipulate the thermoelectric properties by band engineering and hierarchical structure phonon scattering, leading to the enhancement of zT from nearly 1 to above 2. For instance, p‐type PbTe shows a maximum zT of ≈2.6 at 850 K, while p‐type GeTe possesses a maximum zT of 2.4 at 600 K, p‐type SnSe single crystals show a zT of 2.6 at 923 K, and n‐type SnSe single crystals show a zT of 2.8 at 773 K . Some rare‐earth chalcogenides can even be used above 1000 K due to their high thermal stability, such as La 3− x Te 4 which exhibits a maximum zT of ≈1.1 at 1275 K .…”

Section: Introductionmentioning

confidence: 99%

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Cagnoni

Cojocaru‐Mirédin

et al. 2019

Adv Funct Materials

177

214

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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: Introductionmentioning

confidence: 99%

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Cagnoni

Cojocaru‐Mirédin

et al. 2019

Adv Funct Materials

177

214

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“…[ 38 ] Therefore, many previous studies for improving thermoelectric GeTe focus on optimizing the carrier concentration. [ 39–45 ] An obvious solution is doping of elements acting as electron donors to decrease the hole carrier concentration. For example, Bi and Sb have been reported to be effective donors to decrease the carrier concentration.…”

Section: Introductionmentioning

confidence: 99%

“…[ 47 ] Up to now, the record high thermoelectric performance was achieved in GeTe containing Pb substitution. [ 40 ] However, the toxicity of Pb is always a concern for terrestrial application.…”

Section: Introductionmentioning

confidence: 99%

Manipulating the Ge Vacancies and Ge Precipitates through Cr Doping for Realizing the High‐Performance GeTe Thermoelectric Material

Shuai

Sun

Tan

et al. 2020

Small

143

107

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GeTe alloy is a promising medium‐temperature thermoelectric material but with highly intrinsic hole carrier concentration by thermodynamics, making this system to be intrinsically off‐stoichiometric with Ge vacancies and Ge precipitations. Generally, an intentional increase of formation energy of Ge vacancy by element substitution will lead to an effective dissolution of Ge precipitates for reduction in hole concentration. Here, an opposite direction of decreasing the formation energy of Ge vacancies is demonstrated by substituting Cr at Ge site. This strategy produces more but nearly homogenously distributed Ge precipitations and Ge vacancies, which provides enhanced phonon scattering and effectively reduces the lattice thermal conductivity. Furthermore, Cr atom carries one more electron than Ge and serves as an electron donor for decreasing the hole carrier concentrations. Further optimization incorporates the effect of Bi substitution for facilitating band convergence. A maximum figure of merit (ZT) of 2.0 at 600 K with average ZT of over 1.2 is achieved in the sample of Ge0.92Cr0.03Bi0.05Te, making it one of the best thermoelectric materials for medium‐temperature application.

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“…Importantly, the energy offset between (∆ E L‐∑ ) can be engineered to be within a few k B T for an overall high N v of 12 to 16 thus leading to an enhanced power factor ( PF = S 2 / ρ ). With a further help of microstructure engineering for κ L reduction, an extraordinary zT (>2) has been achieved …”

Section: Introductionmentioning

confidence: 99%

Solute manipulation enabled band and defect engineering for thermoelectric enhancements of SnTe

Yao

Tang

et al. 2019

InfoMat

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With years of development, SnTe as a homologue of PbTe has shown great potential for thermoelectric applications in p‐type conduction, and the most successful strategy is typified by alloying for maximizing the valence band degeneracy. Among the known alloy agents, MnTe has been found to be one of the most effective enabling a band convergence for an enhancement in electronic performance of SnTe, yet its solubility of only ~15 at% unfortunately prevents a full optimization in the valence band structure. This work reveals that additional PbTe alloying not only promotes the MnTe solubility to locate the optimal valence band structure but also increases the overall substitutional defects in the material for a substantial reduction in lattice thermal conductivity. In addition, PbTe alloying simultaneously optimizes the carrier concentration due to the cation size effect. These features all enabled by such a solute manipulation synergistically lead to a very high thermoelectric figure of merit, zT of ~1.5 in SnTe with a 20 at% MnTe and a 30 at% PbTe alloying (Sn0.5Mn0.2Pb0.3Te), demonstrating the effectiveness of solute manipulation for advancing SnTe and similar thermoelectrics.

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Low-Symmetry Rhombohedral GeTe Thermoelectrics

Cited by 452 publications

References 70 publications

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

Manipulating the Ge Vacancies and Ge Precipitates through Cr Doping for Realizing the High‐Performance GeTe Thermoelectric Material

Solute manipulation enabled band and defect engineering for thermoelectric enhancements of SnTe

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