Se-alloying reducing lattice thermal conductivity of Ge0.95Bi0.05Te

Wang, De‐Zhuang; Liu, Wei‐Di; Shi, Xiao‐Lei; Gao, Han; Wu, Hao; Yin, Liang‐Cao; Zhang, Yuewen; Wang, Yifeng; Wu, Xueping; Li, Qingfeng

doi:10.1016/j.jmst.2021.08.020

Cited by 20 publications

(11 citation statements)

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“…14 Besides substitution on the cation sites, anion alloying also enhances the thermoelectric performance. 15 Se alloying introduces strong point defect phonon scattering and dramatically reduces κ l . The halogen I successfully reduces n and leads to optimized thermoelectric properties in GeTe.…”

Section: Introductionmentioning

confidence: 99%

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Chemistry in Advancing Thermoelectric GeTe Materials

Hong

Chen

2022

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS:The ever-growing energy crisis and the deteriorated environment caused by carbon energy consumption motivate the exploitation of alternative green and sustainable energy supplies. Because of the unique advantages of zero-emission, no moving parts, accurate temperature control, a long steady-state operation period, and the ability to operate in extreme situations, thermoelectrics, enabling the direct conversion between heat and electricity, is a promising and sustainable option for power generation and refrigeration. However, with increasing application potentials, thermoelectrics is now facing a major challenge: developing high-performance, Pb-free, and lowtoxic thermoelectric materials and devices.As one group of promising candidates, GeTe derivatives have the potential to replace the widely used thermoelectric materials containing highly toxic elements.In this Account, we summarize our recent progress in developing highperformance GeTe-based thermoelectric materials via exploring innovative strategies to enhance electron transports and dampen phonon propagations. First, we fundamentally illustrate the underlying chemistry and physical reason for an intrinsically high carrier concentration in GeTe, which enormously restrains the thermoelectric performance of GeTe. From our theoretical calculations, the formation energy of Ge vacancy is the lowest among the defects in GeTe, energetically favoring Ge vacancies in the lattice and leading to intrinsically high carrier concentrations. Accordingly, aliovalent doping/alloying is proposed to increase the formation energy of Ge vacancies and decrease the carrier concentration to the optimal level. We then outline the newly developed method to refine the band structures of GeTe with tuned electronic transport. On the basis of the molecular orbital theory, the energy offset between two valence band edges at the L and Σ points in GeTe should be ascribed to the slightly different Ge_4s orbital characters at these two points, which guides the screening of dopants for band convergence. Besides, the Rashba spin splitting is explored to increase the band degeneracy of GeTe. Afterward, we analyze the dampened phonon propagation in GeTe to minimize its lattice thermal conductivity. Alloying with the heavy Sb atoms can shift the optical phonon modes toward low frequency and reinforce the interaction of optical and acoustic phonon modes so that the inherent phonon scattering is enhanced. In addition, planar vacancies and superlattice precipitates can significantly strengthen phonon scattering to result in ultralow lattice thermal conductivity. After that, we overview the finite elemental analysis simulations to optimize the device geometry for maximizing the device performance and introduce the as-developed prototype GeTe-based thermoelectric device. In the end, we point out future directions in the development of GeTe for device applications. The strategies summarized in this Account can serve as references for developing wide materi...

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Section: Introductionmentioning

confidence: 99%

“…Reproduced with permission from ref 15. Copyright 2022 Elsevier.Temperature-dependent (h) κ, (i) κ l , and (j) zT of GeTe, Ge 0.98 V 0.02 Te,26 Ge 0.95 Bi 0.05 Te, and Ge 0.95 Bi 0.05 Te 0.7 Se 0.3 15.…”

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confidence: 99%

Chemistry in Advancing Thermoelectric GeTe Materials

Hong

Chen

2022

Acc. Chem. Res.

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“…Figure 4c compares the μ of the (GeTe) 1−x (CuBiSe 2 ) x pellets with solely Se [47] and Bi doped, [25] and their co-doped [49] GeTe as a function of n h . As can be seen, the μ of the (GeTe) 1−x (CuBiSe 2 ) x pellets are much higher than other typical GeTe-based materials, including Ge 0.9 Sb 0.1 Te 0.88 Se 0.12 , [47] Ge 0.94 Bi 0.06 Te, [25] and Ge 0.95 Bi 0.05 Te 0.7 Se 0.3 , [49] indicating that CuBiSe 2 alloying is effective in retaining high μ due to the similar electronegativity between Cu and Ge. This value is also similar to the μ of (GeTe 1−y Sb y Te) 1−x (Cu 2 Te) x alloys.…”

Section: Resultsmentioning

confidence: 99%

“…The intrinsic GeTe shows a S of ≈140 µV K −1 at 723 K, while x (x = 0-0.06), with a comparison to other alloying components at room temperature. [25,33,41,47,48] c) n h -dependent μ, with a comparison to other typical GeTe-based thermoelectric materials, including Ge 0.9 Sb 0.1 Te 0.88 Se 0.12 , [47] Ge 0.94 Bi 0.06 Te, [25] and Ge 0.95 Bi 0.05 Te 0.7 Se 0.3 , [49] at room temperature. d) Temperature-dependent S. e) n h -dependent S. f,g) Band structure calculated for f) R-Ge 25 Te 27 and g) R-Ge 23 CuBiTe 25 Se 2 .…”

Section: Resultsmentioning

confidence: 99%

High Carrier Mobility and High Figure of Merit in the CuBiSe₂ Alloyed GeTe

Yin

Liu

et al. 2021

Advanced Energy Materials

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Dimensionless figure-of-merit (zT) is the most typical descriptor to evaluate thermoelectric materials, which is defined as zT = S 2 σT/κ, where S, σ, T and κ are the Seebeck coefficient, the electrical conductivity, the absolute temperature, and the thermal conductivity, respectively. [4,5] κ includes the lattice thermal conductivity (κ l ) and the electrical thermal conductivity (κ e ). [6,7] To achieve high energy conversion efficiency, high zT values with high power factor (S 2 σ) and low κ are required. According to extensive investigations, S 2 σ can be increased by quantum confinement, [8,9] modulation doping, [10] band convergence, [5,11] and resonant state engineering. [12,13] Whereas, κ (mainly κ l ) is mainly reduced by introducing a variety of lattice defects as phonon scattering centers such as point defects, [14,15] dislocations, [16,17] stacking faults, [18,19] nano precipitates, [20,21] and hierarchical architecture structures. [22,23] GeTe is a promising mid-temperature material with a phase transition from the rhombohedral phase (R-GeTe) to the cubic phase (C-GeTe) at ≈700 K. However, the intrinsic high carrier concentration (n h for p-type GeTe, ≈10 21 cm −3 due to massive Ge vacancies) limits its S 2 σ and thus zT (≈0.75 at ≈740 K). [24,25] To According to theMott's relation, the figure-of-merit of a thermoelectric material depends on the charge carrier concentration and carrier mobility. This explains the observation that low thermoelectric properties of GeTe-based materials suffer from the degraded carrier mobility, on account of the fluctuation of electronegativity and ionicity of various elements. Here, highperformance CuBiSe 2 alloyed GeTe with high carrier mobility due to the small electronegativity difference between Cu and Ge atoms and the weak ionicity of CuTe and BiTe bonds, is developed. Density functional theory calculations indicate that CuBiSe 2 alloying increases the formation energy of Ge vacancies and correspondingly reduces the amount of Ge vacancies, leading to an optimized carrier concentration and a high power factor of ≈37.4 µW cm −1 K −2 at 723 K. Moreover, CuBiSe 2 alloying induces dense point defects and triggers ubiquitous lattice distortions, leading to a reduced lattice thermal conductivity of 0.39 W m −1 K −1 at 723 K. These synergistic effects result in an optimization of the carrier mobility, the carrier concentration, and the lattice thermal conductivity, which favors an enhanced peak figure-of-merit of ≈2.2 at 723 K in (GeTe) 0.94 (CuBiSe 2 ) 0.06 . This study provides guidance for the screening of GeTe-based thermoelectric materials with high carrier mobility.

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“…Recent progress has resulted in a high ZT value of about 2 with a projected efficiency of 20%, which is expected to have a significant impact on the energy production and conservation sectors . Currently, TE materials that are of keen interest are Bi 2 Te 3 ; PbTe; Bi 2 Se 3 ; PbSe; SnTe; Ge 0.95 Bi 0.05 Te; Ge 1– x – y Ta x Sb y Te; half-Heusler compounds like Ti x (Zr 0.5 Hf 0.5 ) (1– x ) NiSn ( x = 0–0.7) or BXGa (X = Be, Mg, and Ca); skutterudites; Mg 2 X (X = Si, Ge, and Sn); ternary compounds (e.g., MgAgSb and BiCuSeO), binary compoundsoxides like ZnO, SrTiO 3 , or NaCo 2 O 4 ; and nitrides like BN, copper chalcogenides, ScN, or C 3 N 4 ; etc.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Insights into Synthesis, Structural Features, and Thermoelectric Properties of High-Performance Inorganic Chalcogenide Nanomaterials for Conversion of Waste Heat to Electricity

Manjunatha¹,

Mulla

Nagaraj³

et al. 2022

ACS Appl. Energy Mater.

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Thermoelectrics are energy harvesters that can directly convert waste heat into electrical energy and vice versa. Currently, thermoelectric (TE) devices display lower efficiency as the materials used for construction possess a very low figure of merit (ZT). Therefore, understanding the structural features of materials, finding new materials, and analyzing their chemistry and physics play a vital role in enhancing their energy conversion efficiency. Among the different classes of TE materials, some inorganic chalcogenides are perfect candidates for power generation as they possess excellent TE properties. The objective of this review is to provide insights into structural features and innovative methods to obtain enhanced thermoelectric properties of selected inorganic chalcogenides. The review covers recent advances in preparation methods, structural features, and thermoelectric properties of selected metal selenides (Bi2Se3, Ag2Se, SnSe, etc.) and metal tellurides (Bi2Te3, SnTe, PbTe, etc.). The review also discusses the critical parameters for designing and optimizing the TE materials to obtain the required electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (k). In addition, promising mechanistic approaches to be adopted for enhancing the efficiency of TE materials such as doping, alloying, and nanostructuring are discussed in detail. Finally, a summary that describes advancements in the materials design is provided with a prospect for future applications from these materials in the development of energy harvesting technology.

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Se-alloying reducing lattice thermal conductivity of Ge0.95Bi0.05Te

Cited by 20 publications

References 45 publications

Chemistry in Advancing Thermoelectric GeTe Materials

Chemistry in Advancing Thermoelectric GeTe Materials

High Carrier Mobility and High Figure of Merit in the CuBiSe₂ Alloyed GeTe

Comprehensive Insights into Synthesis, Structural Features, and Thermoelectric Properties of High-Performance Inorganic Chalcogenide Nanomaterials for Conversion of Waste Heat to Electricity

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Se-alloying reducing lattice thermal conductivity of Ge0.95Bi0.05Te

Cited by 20 publications

References 45 publications

Chemistry in Advancing Thermoelectric GeTe Materials

Chemistry in Advancing Thermoelectric GeTe Materials

High Carrier Mobility and High Figure of Merit in the CuBiSe2 Alloyed GeTe

Comprehensive Insights into Synthesis, Structural Features, and Thermoelectric Properties of High-Performance Inorganic Chalcogenide Nanomaterials for Conversion of Waste Heat to Electricity

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High Carrier Mobility and High Figure of Merit in the CuBiSe₂ Alloyed GeTe