High Thermoelectric Figure of Merit in PbTe Alloys Demonstrated in PbTe–CdTe

Pei, Yanzhong; LaLonde, Aaron D.; Heinz, Nicholas A.; Snyder, G. Jeffrey

doi:10.1002/aenm.201100770

Cited by 255 publications

(211 citation statements)

References 63 publications

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“…1 Recent reports on PbTe and its alloys have suggested an extraordinarily high peak zT of between 1.5 and 2.2 depending on the specific dopant and alloy. [2][3][4][5][6] The reports have led to a renewed interest in the lead chalcogenides and have generated a debate concerning the mechanism for their high thermoelectric performance. The mechanism is believed to be the enhanced degeneracy arising from band convergence, which yields higher thermopower without greatly reducing carrier mobility.…”

mentioning

confidence: 99%

Temperature dependent band gap in PbX (X = S, Se, Te)

Gibbs¹,

Kim²,

Wang³

et al. 2013

Applied Physics Letters

158

124

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PbTe is an important thermoelectric material for power generation applications due its high conversion efficiency and reliability. Its extraordinary thermoelectric performance is attributed to band convergence of the light L and heavy Σ bands. However, the temperature at which these bands converge is disputed. In this letter, we provide direct experimental evidence combined with ab initio calculations that confirm an increasing optical gap up to 673 K and predict a band convergence temperature of 700 K, much higher than previous measurements showing saturation and band convergence at 450 K.

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mentioning

confidence: 99%

Temperature dependent band gap in PbX (X = S, Se, Te)

Gibbs¹,

Kim²,

Wang³

et al. 2013

Applied Physics Letters

158

124

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“…Many experimental works were performed with alloying to adjust the convergence temperature to desired range. The band structure modifications of PbTe-based materials through isovalent substitutions by Mn, 58,59 IIB, 60 and IIA elements 61 were originally studied before 1980s, [62][63][64] and have been revisited with intensive investigation for TE applications. Compared to lead chalcogenides, the strategy of valley convergence through alloying plays a more important role in the zT enhancement for SnTe, since the room temperature energy offset between L and Σ valleys for SnTe is much higher (~0.3 eV for SnTe,~0.1 eV for PbTe).…”

Section: Valley Degeneracymentioning

confidence: 99%

Valleytronics in thermoelectric materials

et al. 2018

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The central theme of valleytronics lies in the manipulation of valley degree of freedom for certain materials to fulfill specific application needs. While thermoelectric (TE) materials rely on carriers as working medium to absorb heat and generate power, their performance is intrinsically constrained by the energy valleys to which the carriers reside. Therefore, valleytronics can be extended to the TE field to include strategies for enhancing TE performance by engineering band structures. This review focuses on the recent progress in TE materials from the perspective of valleytronics, which includes three valley parameters (valley degeneracy, valley distortion, and valley anisotropy) and their influencing factors. The underlying physical mechanisms are discussed and related strategies that enable effective tuning of valley structures for better TE performance are presented and highlighted. It is shown that valleytronics could be a powerful tool in searching for promising TE materials, understanding complex mechanisms of carrier transport, and optimizing TE performance.npj Quantum Materials (2018) 3:9 ; doi:10.1038/s41535-018-0083-6 INTRODUCTIONThe demand for renewable energy harvesting has been growing because of the limited fossil fuels and increasing worldwide energy consumption. Thermoelectric (TE) materials, which have the capability of converting heat directly into electricity under a temperature gradient, have been regarded as an alternative option to alleviate energy shortage.1 Though TE devices have already been applied in deep space exploration and solid state cooling, 2,3 the relatively low energy conversion efficiency limits their wide commercialization, 4 which is mainly constrained by the performance of TE materials as characterized by the dimensionless figure of merit, zT = α 2 σT/(κ e + κ L ), where α is the Seebeck coefficient, σ is the electrical conductivity, κ e and κ L are, respectively, the electronic and lattice contributions to the total thermal conductivity κ, and T is the absolute temperature.5 Since all three physical properties (α, σ, and κ) are carrier concentration dependent, zT could reach its maximum value at an optimized carrier concentration. zT max is determined by a combination of intrinsic physical parameters as well as the temperature, all of which integrated into a term called the TE quality factor, B. Higher quality factor B leads to higher zT max at a fixed temperature. With a single parabolic band model in the nondegenerate limit, B could be expressed as:

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“…Effective approaches include nanostructuring, 2-7 lattice anharmonicity, 8,9 liquid phonons, 10,11 vacancy [12][13][14] or interstitial 15 point defects and a low sound velocity. 16 Band engineering concepts including a large number of degenerated bands, [17][18][19][20][21][22][23][24][25] a low band effective mass 26 and weak carrier scattering 27 have also proven to be successful in enhancing the TE performance. The knowledge of the band structure is thus critical for band engineering and optimizing the electrical transport of TE materials.…”

Section: Introductionmentioning

confidence: 99%

“…Since band engineering approaches such as band convergence have recently proven to enhance effectively the TE performance of both PbTe 17,21,23,62 and SnTe 63,64 in their p-type forms, it is believed that a detailed investigation of the band structure and the inherent transport properties of GeTe in both its low-and high-temperature phases would be helpful not only for guiding the band/microstructure engineering approaches for further improvements but also for evaluating their net contributions.…”

Section: Introductionmentioning

confidence: 99%

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

et al. 2017

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PbTe and SnTe in their p-type forms have long been considered high-performance thermoelectrics, and both of them largely rely on two valence bands (the first band at L point and the second one along the Σ line) participating in the transport properties. This work focuses on the thermoelectric transport properties inherent to p-type GeTe, a member of the group IV monotellurides that is relatively less studied. Approximately 50 GeTe samples have been synthesized with different carrier concentrations spanning from 1 to 20 × 10 20 cm − 3 , enabling an insightful understanding of the electronic transport and a full carrier concentration optimization for the thermoelectric performance. When all of these three monotellurides (PbTe, SnTe and GeTe) are fully optimized in their p-type forms, GeTe shows the highest thermoelectric figure of merit (zT up to 1.8). This is due to its superior electronic performance, originating from the highly degenerated Σ band at the band edge in the low-temperature rhombohedral phase and the smallest effective masses for both the L and Σ bands in the high-temperature cubic phase. The high thermoelectric performance of GeTe that is induced by its unique electronic structure not only provides a reference substance for understanding existing research on GeTe but also opens new possibilities for the further improvement of the thermoelectric performance of this material.

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High Thermoelectric Figure of Merit in PbTe Alloys Demonstrated in PbTe–CdTe

Cited by 255 publications

References 63 publications

Temperature dependent band gap in PbX (X = S, Se, Te)

Temperature dependent band gap in PbX (X = S, Se, Te)

Valleytronics in thermoelectric materials

Electronic origin of the high thermoelectric performance of GeTe among the p-type group IV monotellurides

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