Computational design of thermoelectric alloys through optimization of transport and dopability

Qu, Jiaxing; Balvanz, Adam; Baranets, Sviatoslav; Bobev, Svilen; Gorai, Prashun

doi:10.1039/d1mh01539g

Cited by 16 publications

(16 citation statements)

References 57 publications

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“…Therefore, we performed DFT calculations on the SQS ,, of AgMnSnSbTe 4 and AgMnPbSbTe 4 , respectively (Figure ). The absence of the electronic states of the two spin channels at the Fermi level reflects their semiconductor nature.…”

Section: Resultsmentioning

confidence: 99%

High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn_1–xPb_xSbTe₄

Luo

et al. 2022

Chem. Mater.

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We investigate the structure and thermoelectric properties of a new high-entropy solid solution system AgMnSn1–x Pb x SbTe4 (x = 0, 0.25, 0.5, 0.75, and 1), which crystallizes in the rock-salt NaCl structure with cations Ag, Mn, Sn, Pb, and Sb randomly disordered over the Na site. Our density functional theory calculations indicate that AgMnSn1–x Pb x SbTe4 exhibits complex multi-peak valence band structures, whose energy difference is lower than 0.11 eV, leading to effective band convergence and thus high density of states effective mass m* and Seebeck coefficients. As a consequence, AgMnSn0.25Pb0.75SbTe4 has a peak ZT of 1.3 at 773 K and a desirable average ZT value of 0.8 in the temperature range of 400–773 K. In addition, we propose the lattice distortion degree (i.e., δ) as an important indicator of thermoelectric performance for high-entropy materials. Specifically, with the gradual increase in δ, the lattice thermal conductivity decreases monotonically from 0.90 W m–1 K–1 for AgMnSnSbTe4 (i.e., δ = 0.205) to 0.54 W m–1 K–1 for AgMnPbSbTe4 (i.e., δ = 0.230) at 300 K. Meanwhile, the generalized material parameter B x */B 0 * and ZT increase monotonically from 1 and 0.11 for δ = 0.205 to 3.15 and 0.29 for δ = 0.230 at 300 K.

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Section: Resultsmentioning

confidence: 99%

High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn_1–xPb_xSbTe₄

Luo

et al. 2022

Chem. Mater.

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“…We explain the poor p‐type dopability of AgBiSe 2 ‐based materials by calculating the point defect energetics of the end member AgBiSe 2 in the L 1 1 phase using density functional theory (DFT) calculations. In principle, one can examine the formation of point defects in the disordered ABSS alloy using, for example, special quasi‐random structures (SQS); [ 23 ] however, we show that our results of AgBiSe 2 match experimental observations well and provide first‐order insights into the unstable p‐type conductivity in AgBiSe 2 ‐based materials.…”

Section: Resultsmentioning

confidence: 60%

Suppressing Charged Cation Antisites via Se Vapor Annealing Enables p‐Type Dopability in AgBiSe₂–SnSe Thermoelectrics

et al. 2022

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figure-of-merit (zT) of a TE material, which is given by zT = S 2 σT/κ, where S, σ, T, and κ are the Seebeck coefficient, electrical conductivity, absolute temperature, and thermal conductivity, respectively. [3] Nevertheless, the competing interplay between electrical and thermal properties has stagnated the rise of zT for decades. [4] Ternary ABX 2 -type (A = group I, B = group V, X = group VI elements) compounds have gained considerable attention as promising candidates for TE applications. [5] Lone-pair electrons of B-site cations contribute to strong phonon-phonon interactions and lower the lattice thermal conductivity. [6] Therefore, several ABX 2 compounds show temperature-independent thermal conductivities unlike those of conventional TE materials. [7] This intriguing property provides a venue for modulating electronic properties with more degrees of freedom because ABX 2 compounds are relatively free from the complicated trade-off relationship between electrical and thermal properties. However, utilizing ABX 2 compounds has been limited by serious problems: an absence of rational design rules, complex phase stability, and poor reproducibility. [8,9] For example, an undoped hexagonal AgBiSe 2 shows a wide range of Seebeck coefficients from −450 to 250 µV K −1 depending on the synthesis condition (Figure 1a,b). In addition, the B-site cation determines the sign of the Seebeck coefficient, where most Sb-based ABX 2 compounds are intrinsically p-type and Bi-based Cation disordering is commonly found in multinary cubic compounds, but its effect on electronic properties has been neglected because of difficulties in determining the ordered structure and defect energetics. An absence of rational understanding of the point defects present has led to poor reproducibility and uncontrolled conduction type. AgBiSe 2 is a representative compound that suffers from poor reproducibility of thermoelectric properties, while the origins of its intrinsic n-type conductivity remain speculative. Here, it is demonstrated that cation disordering is facilitated by Bi Ag charged antisite defects in cubic AgBiSe 2 which also act as a principal donor defect that greatly controls the electronic properties. Using density functional theory calculations and in situ Raman spectroscopy, how saturation annealing with selenium vapor can stabilize p-type conductivity in cubic AgBiSe 2 alloyed with SnSe at high temperatures is elucidated. With stable and controlled hole concentration, a peak is observed in the weighted mobility and the density-ofstates effective mass in AgBiSnSe 3 , implying an increased valley degeneracy in this system. These findings corroborate the importance of considering the defect energetics for exploring the dopability of ternary thermoelectric chalcogenides and engineering electronic bands by controlling self-doping.

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“…Compounds with AM 2 Pn 2 and A 2 MPn 2 stoichiometry illustrate an example of the benefits and drawbacks of this generalized understanding of layered structures . Recent studies have emphasized the importance of cation bonding, identity, disorder, and defects in Yb 2 – x Ca x CdSb 2 , Ca 2 – x Eu x CdSb 2 , Yb 2– x Eu x CdSb 2 , Ca 2– x Lu x CdSb 2 , A 2 CdP 2 (A = Ba, Sr), and AZn 2 Sb 2 (A = Ca, Sr, Yb, Eu) in determining electronic properties and structure type. ,− In addition, studies on Mg 3 Sb 2 have revealed that the Zintl formalism does not adequately describe interactions between cations and [Mg 2 Sb 2 ] 2– slabs in AMg 2 Pn 2 compounds, which cannot be considered layered structures due to isotropic bonding networks, even though they adopt the CaAl 2 Si 2 structure type. , These examples highlight the need for better understanding of chemical bonding, defects, and local structure in each system to enable optimization of thermoelectric properties.…”

Section: Introductionmentioning

confidence: 99%

Deciphering Defects in Yb_2–xEu_xCdSb₂ and Their Impact on Thermoelectric Properties

et al. 2022

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Layered Zintl phases with A2MPn2 stoichiometry are an underexplored class of potential thermoelectric materials with complex and diverse chemistry. The solid solution Yb2–x Eu x CdSb2 is an example of the promise these compounds hold, as one composition, Yb1.64Eu0.36CdSb2, has reported one of the highest zTs of any Zintl phase material at 525 K. The present study examines changes in structure and bonding of this solid solution that impacts thermoelectric performance. Pair distribution function analysis is combined with electronic structure modeling to take a chemical bonding-based approach to deconvolute the impact of defects on thermal and electronic properties in Yb2–x Eu x CdSb2. Yb2–x Eu x CdSb2 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) samples were synthesized, and thermoelectric properties and defect chemistry were investigated. Samples from the middle of the series x = 0.2 and 0.3 were found to be the most highly defected, exhibiting Yb and Sb vacancies, as well as distortions in the Yb–Sb coordination spheres that correlate with thermoelectric properties. The highest efficiency is reported for x = 0.4 (zT ≈ 0.9 at 525 K), and the thermoelectric quality factor predicts that x = 0.3 could achieve zT > 2 by synthetically tuning the defect structure and thereby carrier concentration. The strategy of investigating local structure outlined in this study can be applied to a variety of other thermoelectric materials to provide insight into the hidden role of defect chemistry in understanding the structure–property relationships in extended solids.

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Computational design of thermoelectric alloys through optimization of transport and dopability

Abstract: We develop a computational framework to guide the systematic optimization of transport properties and dopability of thermoelectric alloys.

Cited by 16 publications

References 57 publications

High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn_1–xPb_xSbTe₄

High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn_1–xPb_xSbTe₄

Suppressing Charged Cation Antisites via Se Vapor Annealing Enables p‐Type Dopability in AgBiSe₂–SnSe Thermoelectrics

Deciphering Defects in Yb_2–xEu_xCdSb₂ and Their Impact on Thermoelectric Properties

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Computational design of thermoelectric alloys through optimization of transport and dopability

Abstract: We develop a computational framework to guide the systematic optimization of transport properties and dopability of thermoelectric alloys.

Cited by 16 publications

References 57 publications

High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn1–xPbxSbTe4

High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn1–xPbxSbTe4

Suppressing Charged Cation Antisites via Se Vapor Annealing Enables p‐Type Dopability in AgBiSe2–SnSe Thermoelectrics

Deciphering Defects in Yb2–xEuxCdSb2 and Their Impact on Thermoelectric Properties

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High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn_1–xPb_xSbTe₄

High Thermoelectric Performance and Low Lattice Thermal Conductivity in Lattice-Distorted High-Entropy Semiconductors AgMnSn_1–xPb_xSbTe₄

Suppressing Charged Cation Antisites via Se Vapor Annealing Enables p‐Type Dopability in AgBiSe₂–SnSe Thermoelectrics

Deciphering Defects in Yb_2–xEu_xCdSb₂ and Their Impact on Thermoelectric Properties