Robust mechanical properties of Ag2Se1–xTex thermoelectric materials

Heyang Chen; Shenghong Ren; Hengyang Feng; Tian-Ran Wei; Ling Fu; Zhenyu Pan; Kunpeng Zhao; Xiuyan Li; Xun Shi

doi:10.1360/nso/20250005

All issues

Volume 4 / No 3 (2025)

Natl Sci Open, 4 3 (2025) 20250005

Full HTML

Special Topic: Thermoelectric Materials and Devices

Open Access

Issue		Natl Sci Open Volume 4, Number 3, 2025 Special Topic: Thermoelectric Materials and Devices


Article Number		20250005
Number of page(s)		10
Section		Materials Science
DOI		https://doi.org/10.1360/nso/20250005
Published online		30 April 2025

National Science Open 4: 20250005, 2025

RESEARCH ARTICLE

Robust mechanical properties of Ag₂Se_1–_xTe_x thermoelectric materials

Heyang Chen¹^,#, Shenghong Ren²^,3^,#, Hengyang Feng¹, Tian-Ran Wei¹^,4^*, Ling Fu¹, Zhenyu Pan¹^*, Kunpeng Zhao¹^,4, Xiuyan Li² and Xun Shi¹^,5^*

¹ State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
² Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
³ School of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China
⁴ Wuzhen Laboratory, Tongxiang 314500, China
⁵ State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

^* Corresponding authors (emails: tianran_wei@sjtu.edu.cn (Tian-Ran Wei); zpan@sjtu.edu.cn (Zhenyu Pan); xshi@mail.sic.ac.cn (Xun Shi))

Received: 4 February 2025
Revised: 15 April 2025
Accepted: 18 April 2025

Abstract

High mechanical robustness is essential to the material’s processibility for the applications in flexible and miniaturized electronics. As state-of-the-art room-temperature thermoelectric materials, Ag₂Se_1–xTe_x alloys exhibit superior thermoelectric transport properties but their mechanical properties remain largely unexplored. Herein, we systematically investigate the mechanical and thermoelectric properties of a series of Ag₂Se_1–xTe_x materials. Among them, Ag₂Se_0.9Te_0.1 shows robust mechanical properties including a large compression strain of (26.7 ± 4.5)%, a high compression strength of (279.2 ± 49) MPa, and an excellent fracture toughness of (4.5 ± 0.6) MPa m^1/2. These robust mechanical properties are ascribed to the dense dislocations as well as possible sub-grain rotations. Combined with the excellent thermoelectric figure of merit, zT of 0.78 at 300 K and 1.1 at 380 K, the Ag₂Se_1–xTe_x alloys are promising candidates for robust and efficient thermoelectric applications near room temperature.

Key words: thermoelectric / Ag₂Se-Ag₂Te / mechanical properties

^#

Contributed equally to this work.

© The Author(s) 2025. Published by Science Press and EDP Sciences.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

INTRODUCTION

Thermoelectric materials enable the direct conversion between heat and electricity, providing a promising solution for green energy utilization and environmental protection [1,2]. The past two decades have witnessed the blossom of a variety of high-performance thermoelectric materials [3–7] along with new theories and design strategies. In recent years, thermoelectric technology has widely expanded its realm and found new applications in several booming industries, especially the self-powered flexible and nano/micro-scale electronics used as physiological monitors and wearable intelligent sensors [8,9]. To meet these conditions, thermoelectric materials are required to possess both a high zT (defined as zT = S²σT/κ, where S, σ, T, and κ represent the Seebeck coefficient, electrical conductivity, absolute temperature, and thermal conductivity, respectively) and robust mechanical properties around room temperature to ensure decent processibility and deformability [10,11].

Traditional high-performance thermoelectric materials are typically brittle. For example, Bi₂Te₃-based polycrystalline alloys, the best room-temperature thermoelectric materials, show a small compressibility of merely ~5% [6,12–19]> (Figure 1). As a consequence, seeking mechanically robust thermoelectric materials is a long-standing goal for promoting the application of thermoelectric devices. Fortunately, among the promising room-temperature thermoelectric materials, the Ag₂Se and Ag₂Te compounds are reported to show decent mechanical properties [20–28]: the compression strength and ultimate strain values can reach approximately 275 and 160 MPa, 40% and 20% for high-quality Ag₂Se and Ag₂Te samples, respectively. Interestingly, a large elongation of around 43% was found in nano-sized Ag₂Te material [26]. The introduction of domains and secondary phases was also employed to enhance the mechanical properties [23,27,28]. In addition to the pristine compounds, alloying is a classic and effective method to modulate transport and mechanical properties [29]. Feng et al. [26] studied the mechanical properties of Te-rich Ag₂(Te, Se) alloys, i.e., Ag₂Te_0.92Se_0.08, Ag₂Te_0.88Se_0.12, and Ag₂Te_0.8Se_0.2. The compression strains range from 10% to 22% and the strengths are 92–160 MPa.

Figure 1

(A) Average values of the compression strength and ultimate strain for Ag₂Se_1–xTe_x samples in this work (red stars); data of Ag₂Se [27,28,33], Ag₂Te [23,26], Ag₂Te_1–ySe_y [26] and Bi₂Te₃-based polycrystalline thermoelectric materials [6,12–14,17–19] are included for comparison. Raw data are listed in Table S1. (B) Comparison of mechanical and physical properties between Ag₂Se_0.9Te_0.1 and typical Bi₂Te₃-based polycrystalline thermoelectric materials [6,12].

Despite the above progress, the understanding of the mechanical properties of Ag₂(Se, Te) is still quite inadequate in terms of several aspects. Firstly, several key mechanical properties, such as fracture toughness and energy absorption, are overlooked in previous studies while these parameters are particularly important to evaluate materials ability to resist crack propagation. Secondly, for the Ag₂Se-Ag₂Te alloys, the mechanical study focuses only on Te-rich compositions (from Ag₂Te to Ag₂Te_0.8Se_0.2) [26] while a wide range of compositions remain to be explored. In addition, the underlying deformation mechanisms for this system need further exploration.

In this study, we comprehensively investigate the mechanical properties of Ag₂Se-Ag₂Te series materials, in terms of a wide range of compositions and diverse mechanical behaviors. It is found that this series of high-performance thermoelectric materials combines decent compressibility, strength, and toughness. As a case study, the high-performance Ag₂Se_0.9Te_0.1 material shows superior mechanical properties. Particularly, the fracture toughness of (4.5 ± 0.6) MPa m^1/2 is larger than typical thermoelectric counterparts like (Bi, Sb)₂Te₃, MgAgSb and Mg₃(Sb, Bi)-based materials [6,30,31]. Detailed microstructural analyses reveal that the large compressibility and toughness should originate from the dislocation multinucleation as well as the sub-grain rotation. This work demonstrates Ag₂Se_1–xTe_x materials as promising thermoelectric materials with high performance and toughness for durable and stable thermoelectric devices.

MATERIALS AND METHODS

A series of Ag₂Se_1–xTe_x samples were synthesized by a melting and annealing process followed by spark plasma sintering (SPS). High-purity elements Ag (shots, 99.99%, Alfa Aesar), Se (shots, 99.999%, Aladdin), and Te (shots, 99.999%, Aladdin) were weighted and then sealed in quartz tubes under vacuum. Slight Ag deficiencies were introduced in this procedure to finely tune the transport properties. The quartz tubes were slowly heated to 1273 K and kept at this temperature for 12 h. Afterwards, the tubes were cooled down to 1023 K over 25 h, and then to 723 K. After being dwelled at 723 K for 72 h, the tubes are naturally cooled down to room temperature. The as-prepared ingots were ground into powders under liquid nitrogen and dried in the oven at 338 K for 24 h to remove moisture. Powders were then consolidated by SPS at 623 K under the pressure of 55 MPa for 10 min.

The X-ray diffraction (XRD) was carried out with the Cu-Kα source with a scanning speed of 4°/min. The sample morphologies were examined by field emission scanning electron microscopy (FESEM, TESCAN RISE-MAGNA), along with energy dispersive X-ray analysis to observe elemental distribution. The transmission electron microscope (TEM) was characterized by FEI Talos F200X. The electrical conductivity and Seebeck coefficient were measured using ZEM-3 (Advanced Riko, Japan). The thermal conductivity was obtained via κ = λ × C_p × d, where λ is thermal diffusivity measured by Netzsch LFA-457, C_p is the heat capacity estimated by the Dulong-Petit law, and the density d was measured using Archimedes method. The differential scanning calorimetry was conducted on Netzsch DSC 404. The carrier concentration was measured by Lakeshore 8400 series using the van der Pauw method. The confocal laser scanning microscope test for the surface was performed on ZEISS LSM 900. Compression, three-point bending and fracture toughness tests were performed on SHIMADZU AGS-X. The specimen size is about 3 mm × 3 mm × 6.5 mm for compression with a constant strain rate of 0.005 min^–1, 2 mm × 1 mm × 18 mm for three-point bending and 3 mm × 2 mm × 18 mm with pre-crack length of 1.1 mm for fracture toughness. The loading speed for three-point bending and fracture toughness tests was set at 0.1 mm/min. The sound velocity data were measured by the ultrasonic measurement system UMS-100 with transverse wave transducers of 5 MHz and longitudinal wave transducers of 10 MHz.

RESULTS

Phase structures

For the Ag₂Se_1–xTe_x samples, the XRD patterns (Figure S1) are indexed to the Ag₂Se-based orthorhombic structure and Ag₂Te-based monoclinic structure when x < 0.7 and x > 0.7, respectively. For the composition of x = 0.7, the diffraction peaks are mainly indexed to Ag₂Se structure but a minor Ag₂Te-structured phase is also observed, indicating a mixed phase (also see Figure S2 for XRD refinement). The peaks shift to lower angles with increasing Te content in the Ag₂Se-structure region, which validates the alloying effect of Te in enlarging the lattice. All the Ag, Se, and Te elements show a homogeneous distribution as shown in Figure S1. With increasing Te content, the orthorhombic-to-cubic transition temperature slightly varies between 407 and 410 K as reflected by the DSC analysis (Figure S1). For the Ag₂Se_0.3Te_0.7 mixed-phase sample, two distinct endothermic peaks appear. This phase transition composition is also consistent with previous reports [32].

Mechanical properties

The compression stress-strain curves of Ag₂Se_1–xTe_x samples are shown in Figure S3. Although there is a certain degree of data scattering, the average values are still useful for comparison. For both Ag₂Se and Ag₂Te, the average compression strength and strain well exceed 200 MPa and 30%, among the highest reported data for the two materials [23,33]. Compared with the pristine binary compounds, both the strength and compressibility decrease for the alloys, except two compositions: Ag₂Se_0.9Te_0.1 and Ag₂Se_0.3Te_0.7 (Figures 1A and 2A). As summarized in Figure 1A, the Ag₂Se_1–xTe_x alloys are obviously more compressible and stronger than Bi₂Te₃-based materials (see raw data in Table S1). Taking Ag₂Se_0.9Te_0.1 as a typical case, the average compression strength is as high as 279.2 MPa and the average strain is 26.7%. For a couple of samples, the largest strength and strain can even reach around 300 MPa and 29%, respectively (Figure S3). The three-point bending test results are shown in Figure S3(i). The composition-dependent bending strength of the alloys is consistent with the compression strength. The Ag₂Se sample exhibits the maximum fractured bending strain of around 3% while other compositions show the values around 1%, a sign of brittle behavior in bending. The difference between bending and compression behaviors is well expected considering the different stress states.

Figure 2

(A) Compression strength, compression strain and bending strength for Ag₂Se_1–xTe_x samples. (B) Fracture toughness K_IC for Ag₂Se_1–xTe_x samples; data of Bi_0.5Sb_1.5Te₃ [6], Mg₃Sb_1.3Bi_0.7 [31], PbTe [34] are also given for comparison. (C) Schematic illustration of energy absorption (modulus of toughness) for Ag₂Se under compression test. (D) Modulus of toughness for Ag₂Se, Ag₂Se_0.9Te_0.1 and other typical thermoelectric materials [12,30,35]. The error bars in panels A, B, and D denote the standard deviation from multiple measurements.

The fracture toughness K_IC, the ability to resist the propagation of the crack, is also measured on single-edge notch-bending specimens (see the calculation detail in Supplementary Data). As shown in Figure 2B, the K_IC values share the similar tendency with the strength. The highest value of (4.5 ± 0.6) MPa m^1/2 appears at the composition Ag₂Se_0.9Te_0.1, which is higher than other thermoelectric materials like BiSbTe (0.9 MPa m^1/2) [6], PbTe (0.59 MPa m^1/2) [34], and Mg₃Sb_1.3Bi_0.7 (3.0 MPa m^1/2) [31]. Moreover, the integral of the area under stress-strain curves is often used to represent the total energy absorbed per unit volume up to failure as shown in Figure 2C. This value is termed as modulus of toughness, giving the overall measure of materials’ ability to withstand both elastic and plastic deformation [35]. This parameter is especially important when facing a significant amount of impact. As shown in Figure 2D, this value is derived as (65 ± 16) MJ m^–3 for Ag₂Se and (55 ± 17) MJ m^–3 for Ag₂Se_0.9Te_0.1 from the compression stress-strain curve, much larger than most traditional thermoelectric materials. The high K_IC and modulus of toughness clearly indicate the tough and robust character of the materials.

Figure S5 shows the composition-dependent bulk modulus (B) and shear modulus (G) that are obtained from the measured sound speed. The bulk modulus is around 64 GPa for Ag₂Se and 48 GPa for Ag₂Te, which are comparable with the clathrate Ba₈Ga₁₆Ge₃₀ (66 GPa) and Mg₃Sb₂-based materials (45 GPa), and larger than hot-deformed Bi₂Te₃-based materials (ranging from 29 to 39 GPa) [6,36,37]. The alloyed samples show a slight decrease in modulus, which is consistent with the compression strength in Figure 2A.

Microstructural analysis

We perform detailed microstructural analyses to understand the origin of these robust mechanical properties. As shown in Figures S6 and S7, clear slip bands appear after compression for typical compositions Ag₂Se_0.9Te_0.1, Ag₂Se and Ag₂Te. In contrast, the bent samples exhibit intergranular fracture morphologies (Figure S4), suggesting the brittle behavior. Obvious dislocation lines are observed in broad regions in compressed Ag₂Se_0.9Te_0.1 (TEM bright-field image, Figure 3A and Figure S8) and some are further identified as dislocation arrays in a single grain (HRTEM, Figure 3B). The formation of dislocation arrays indicates the multiplication, movements and accumulation of dislocations in Ag₂(Se, Te) materials. The dislocation density estimated via the bright-field images is around 0.9 × 10¹⁴–2.1 × 10¹⁴ m^–2 (Figure S8), which is a high density comparable with 10% tensile deformed Cu metal [38]. The dual effects of dislocations on mechanical properties of these materials can be understood from two aspects. On the one hand, the existence, motion, and multiplication of dislocations can well mediate the compressive deformation by sliding and multiplication, which changes the large local stress into a long-range diffuse stress field and prevents stress concentration [39]. On the other hand, these high-density dislocations accompanied with large lattice strains can also further impair the plasticity and enhance the strength by entangling with each other just like in metals [40].

Figure 3

Transmission electron microscope (TEM) analysis of Ag₂Se_0.9Te_0.1 sample with a compression strain 10%. (A) Bright-field image showing typical dislocations marked by red arrows. (B) HRTEM image and corresponding FFT image highlighting the dislocation array. (C) HRTEM image illustrating two sub-grains; inset images are FFT images. (D) Grain interface of the red area in Panel (C); two sets of planes are marked as red and yellow dots, respectively.

Besides dislocations (Figure 3A and B), other mechanisms also contribute to the large compressibility and toughness. As shown in Figure 3C and D, a straight and coherent boundary is observed between Grain 1 and Grain 2 of the compressed Ag₂Se_0.9Te_0.1. The zone axes are $[\bar{8} \bar{1} 3]$ and $[\bar{7} \bar{3} 1]$ , respectively and the corresponding planes at the boundary are (113) and ( $1 \bar{2} 1$ ), respectively (Figure 3D). It is speculated that when undergoing compressive stress, the partial region of one grain is rotated against the other part, thus forming sub-grains with straight, coherent boundaries with certain orientation differences. More HRTEM images with similar structures are given in Figure S9. Compared with randomly oriented boundaries, the formation of these coherent or semi-coherent boundaries can effectively reduce internal stress and favor the plastic deformation rather than fracture in compression. Similar grain boundaries are also observed in compressed Ag₂Te as shown in Figure S10.

Thermoelectric transport properties

The temperature-dependent thermoelectric properties are shown in Figure S11. The transport properties of silver chalcogenides are sensitive to the Ag/anion ratio and fabrication methods [41,42]. In this study, we tuned the stoichiometry through introducing Ag deficiencies to obtain the optimal performance (Figure S12). To be concise, the compositions are still denoted as their stoichiometric ones. The Ag₂Se and Ag₂Se_0.9Te_0.1 samples exhibit high power factor PF of around 25 μW cm^–1 K^–2 compared with other compositions. According to the |S|-n_H plot (Pisarenko relation) shown in Figure 4A [43], the Ag₂Se-structure compositions have a relatively small density-of-state effective mass m_d^* = 0.23m_e as compared with other typical thermoelectric materials (e.g., 1.12m_e for Bi₂Te_2.7Se_0.3 [44], 1.45m_e for GeTe [45], 2.3m_e for Cu₂Se [3]). The small effective mass is beneficial for electrical transport properties, especially the mobility. As shown in Figure 4B, the room-temperature weighted mobility μ_W, an integrated electrical performance indicator, readily decreases for the alloys, being a sign of alloy scattering of electrons.

Figure 4

(A) Absolute Seebeck coefficient |S| versus carrier concentration n_H for Ag₂Se_1–xTe_x materials at 300 K. Data of other Ag₂Se-based materials are taken from Refs. [29,43]. The dashed line represents the calculated Pisarenko curve by the SPB model. (B) Relations of weighted mobility and lattice thermal conductivity with Te content; the dashed lines are calculated curves. (C) Temperature dependence of zT value for Ag₂Se_1–xTe_x samples with optimized Ag content. (D) zT value versus carrier concentration n_H for Ag₂Se_1–xTe_x materials at 300 K. Data of other Ag₂Se-based materials are taken from Refs. [29,43]. The dashed line represents the calculated Pisarenko curve by the SPB model.

As to the lattice thermal conductivity κ_L, the electrical conductivity is so high that the calculation based on the Wiedemann-Franz law and SPB-derived Lorenz number often suffers from large uncertainties. Instead, we employ a κversusσ linear plot to derive κ_L as the intercept, which was proposed in our previous study [46] and illustrated in Figure S13. The κ_L firstly decreases from 0.66 W m^–1 K^–1 for Ag₂Se and Ag₂Se_0.9Te_0.1 to the minimum of 0.14 W m^–1 K^–1 for Ag₂Se_0.5Te_0.5, and then increases to 0.6 W m^–1 K^–1 for Ag₂Te, exhibiting a typical alloying effect trend [47] in which the mass and strain fluctuations can effectively scatter phonons. The variation of μ_w and κ_L with composition at room temperature is roughly fitted according to Ref. [48], which follows the relation of $\frac{1}{x (1 - x)}$ . It is worth mentioning that the varying trend of μ_w and κ_L with the composition is also consistent with that of the modulus (Figure S5). This means that apart from the alloy scattering effect, the lattice softening by alloying is also at play.

Figure 4C shows the temperature-dependent zT for a series of Ag₂Se_1–xTe_x materials. Combining decent PFs and low thermal conductivity, the Ag₂Se_0.9Te_0.1 material shows a high zT value of 0.78 at room temperature and 1.1 at 380 K. Using the single parabolic model [49], assuming the non-degenerate limit of mobility, μ₀, as 2000 cm² V^–1 s^–1 and lattice thermal conductivity as 0.6 W m^–1 K^–1, the theoretical curve of zTversusn_H is plotted in Figure 4D. If the carrier concentration can be further optimized to 1 × 10¹⁸–2 × 10¹⁸ cm^–3, the room-temperature zT will be further enhanced to above unity.

DISCUSSION

In this work, the phase structures, mechanical and thermoelectric properties of Ag₂Se_1–xTe_x alloys are studied. Te alloying transforms the orthorhombic Ag₂Se into the monoclinic phase at the composition of x~0.7. The orthorhombic Ag₂Se-rich materials exhibit higher thermoelectric performance, especially for the Ag₂Se_0.9Te_0.1 sample. The zT value can reach 0.78 at room temperature and 1.1 at 380 K. Noticeably, Ag₂Se_0.9Te_0.1 exhibits superior mechanical robustness with high strength of (279.2 ± 49) MPa, decent compressibility of (26.7 ± 4.5)%, and large fracture toughness of (4.5 ± 0.6) MPa m^1/2. The robust mechanical properties are attributed to the dense dislocations and possible sub-grain rotations. These findings will advance the understanding of the mechanical properties of Ag₂Se/Ag₂Te-based alloys and help develop robust and efficient thermoelectric materials around room temperature.

Data availability

The original data are available from corresponding authors upon reasonable request.

Funding

Tian-Ran Wei was supported by the National Natural Science Foundation of China (92463310, 52373292). Tian-Ran Wei and Kunpeng Zhao were supported by the Zhejiang Provincial Natural Science Foundation of China (LD25E020001). Xun Shi was supported by the National Natural Science Foundation of China (52232010).

Author contributions

T.-R.W. and X.S. designed the research. H.C., S.R., and H.F. did the experiment. L.F. and Z.P. helped conduct the mechanical property test. H.C. wrote the manuscript. T.-R.W., Z.P., K.Z., X.L., and X.S. revised the manuscript.

Conflict of interest

The authors declare no conflict of interest.

Supplementary information

Supplementary file provided by the authors. Access here

The supporting materials are published as submitted, without typesetting or editing. The responsibility for scientific accuracy and content remains entirely with the authors.

References

He J, Tritt TM. Advances in thermoelectric materials research: Looking back and moving forward. Science 2017; 357: eaak9997. [Article] [CrossRef] [PubMed] [Google Scholar]
Zhu T, Liu Y, Fu C, et al. Compromise and synergy in high-efficiency thermoelectric materials. Adv Mater 2017; 29: 1605884. [Article] [CrossRef] [Google Scholar]
Liu H, Shi X, Xu F, et al. Copper ion liquid-like thermoelectrics. Nat Mater 2012; 11: 422-425. [Article] [Google Scholar]
Zhang Z, Zhao K, Chen H, et al. Entropy engineering induced exceptional thermoelectric and mechanical performances in Cu_2-yAg_yTe_1-2xS_xSe_x. Acta Mater 2022; 224: 117512. [Article] [Google Scholar]
Poudel B, Hao Q, Ma Y, et al. High-thermoelectric performance of nanostructured bismuth antimony telluride bulk alloys. Science 2008; 320: 634-638. [Article] [CrossRef] [PubMed] [Google Scholar]
Zheng Y, Zhang Q, Su X, et al. Mechanically robust BiSbTe alloys with superior thermoelectric performance: A case study of stable hierarchical nanostructured thermoelectric materials. Adv Energy Mater 2015; 5: 1401391. [Article] [CrossRef] [Google Scholar]
Mao J, Zhu H, Ding Z, et al. High thermoelectric cooling performance of n-type Mg₃Bi₂-based materials. Science 2019; 365: 495-498. [Article] [Google Scholar]
Zhao X, Yang S, Wen X, et al. A fully flexible intelligent thermal touch panel based on intrinsically plastic Ag₂S semiconductor. Adv Mater 2022; 34: 2107479. [Article] [CrossRef] [Google Scholar]
Yang Q, Yang S, Qiu P, et al. Flexible thermoelectrics based on ductile semiconductors. Science 2022; 377: 854-858. [Article] [NASA ADS] [CrossRef] [PubMed] [Google Scholar]
Wei T, Qiu P, Zhao K, et al. Ag₂Q-Based (Q = S, Se, Te) silver chalcogenide thermoelectric materials. Adv Mater 2023; 35: 2110236. [Article] [CrossRef] [PubMed] [Google Scholar]
Ma Y, Huang H, Liu Y, et al. Remarkable plasticity and softness of polymorphic InSe van der Waals crystals. J Materiomics 2023; 9: 709-716. [Article] [Google Scholar]
Qin H, Qu W, Zhang Y, et al. Nanotwins strengthening high thermoelectric performance bismuth antimony telluride alloys. Adv Sci 2022; 9: 2200432. [Article] [CrossRef] [Google Scholar]
Zhu Y, Sun Y, Zhu J, et al. Mediating point defects endows n-Type Bi₂Te₃ with high thermoelectric performance and superior mechanical robustness for power generation application. Small 2022; 18: 2201352. [Article] [CrossRef] [PubMed] [Google Scholar]
Wang W, Sun Y, Feng Y, et al. High thermoelectric performance bismuth telluride prepared by cold pressing and annealing facilitating large scale application. Mater Today Phys 2021; 21: 100522. [Article] [Google Scholar]
Chen H, Wei T, Zhao K, et al. Room-temperature plastic inorganic semiconductors for flexible and deformable electronics. InfoMat 2021; 3: 22-35. [Article] [Google Scholar]
Qiu J, Yan Y, Luo T, et al. 3D Printing of highly textured bulk thermoelectric materials: Mechanically robust BiSbTe alloys with superior performance. Energy Environ Sci 2019; 12: 3106-3117. [Article] [Google Scholar]
Qiu J, Yan Y, Xie H, et al. Achieving superior performance in thermoelectric Bi_0.4Sb_1.6Te_3.72 by enhancing texture and inducing high-density line defects. Sci China Mater 2021; 64: 1507-1520. [Article] [Google Scholar]
Sun Y, Guo F, Feng Y, et al. Performance boost for bismuth telluride thermoelectric generator via barrier layer based on low Young’s modulus and particle sliding. Nat Commun 2023; 14: 8085. [Article] [Google Scholar]
Zhu Y, Jin Y, Zhu J, et al. Design of n-type textured Bi₂Te₃ with robust mechanical properties for thermoelectric micro-refrigeration application. Adv Sci 2023; 10: 2206395. [Article] [CrossRef] [Google Scholar]
Ferhat M, Nagao J. Thermoelectric and transport properties of β-Ag₂Se compounds. J Appl Phys 2000; 88: 813-816. [Article] [Google Scholar]
Mi W, Qiu P, Zhang T, et al. Thermoelectric transport of Se-rich Ag₂Se in normal phases and phase transitions. Appl Phys Lett 2014; 104: 133903. [Article] [CrossRef] [Google Scholar]
Huang S, Wei TR, Chen H, et al. Thermoelectric Ag₂Se: Imperfection, homogeneity, and reproducibility. ACS Appl Mater Interfaces 2021; 13: 60192-60199. [Article] [Google Scholar]
Wang H, Feng X, Lu Z, et al. Synergetic enhancement of strength-ductility and thermoelectric properties of Ag₂Te by domain boundaries. Adv Mater 2023; 35: 2302969. [Article] [CrossRef] [Google Scholar]
Peng L, Yang S, Wei TR, et al. Phase-modulated mechanical and thermoelectric properties of Ag₂S_1-xTe_x ductile semiconductors. J Materiomics 2022; 8: 656-661. [Article] [Google Scholar]
Huang H, Chen H, Gao Z, et al. Room-temperature wide-gap inorganic materials with excellent plasticity. Adv Funct Mater 2023; 33: 2306042. [Article] [CrossRef] [Google Scholar]
Feng L, Guo A, Liu K, et al. Highly deformable Ag₂Te_1-xSe_x-based thermoelectric compounds. Mater Today Phys 2023; 33: 101051. [Article] [Google Scholar]
Chen J, Sun Q, Bao D, et al. Simultaneously enhanced strength and plasticity of Ag₂Se-based thermoelectric materials endowed by nano-twinned CuAgSe secondary phase. Acta Mater 2021; 220: 117335. [Article] [Google Scholar]
Wang H, Liu X, Zhou Z, et al. Constructing n-type Ag₂Se/CNTs composites toward synergistically enhanced thermoelectric and mechanical performance. Acta Mater 2022; 223: 117502. [Article] [Google Scholar]
Liang J, Qiu P, Zhu Y, et al. Crystalline structure-dependent mechanical and thermoelectric performance in Ag₂Se_1–xS_x system. Research 2020; 2020: 6591981 [Google Scholar]
Liu Z, Gao W, Meng X, et al. Mechanical properties of nanostructured thermoelectric materials α-MgAgSb. Scripta Mater 2017; 127: 72-75. [Article] [Google Scholar]
Shu R, Zhou Y, Wang Q, et al. Mg_3+δSb_xBi_2−x family: A promising substitute for the state-of-the-art n-type thermoelectric materials near room temperature. Adv Funct Mater 2019; 29: 1807235. [Article] [CrossRef] [MathSciNet] [Google Scholar]
Zhu T, Su X, Zhang Q, et al. Structural transformation and thermoelectric performance in Ag₂Te_1−xSe_x solid solution. J Alloys Compd 2021; 871: 159507. [Article] [Google Scholar]
Liu M, Zhang X, Zhang S, et al. Ag₂Se as a tougher alternative to n-type Bi₂Te₃ thermoelectrics. Nat Commun 2024; 15: 6580. [Article] [Google Scholar]
Li G, Aydemir U, Duan B, et al. Micro- and macromechanical properties of thermoelectric lead chalcogenides. ACS Appl Mater Interfaces 2017; 9: 40488-40496. [Article] [Google Scholar]
Li A, Wang Y, Li Y, et al. High performance magnesium-based plastic semiconductors for flexible thermoelectrics. Nat Commun 2024; 15: 5108. [Article] [Google Scholar]
Isotta E, Peng W, Balodhi A, et al. Elastic moduli: A tool for understanding chemical bonding and thermal transport in thermoelectric materials. Angew Chem Int Ed 2023; 62: e202213649. [Article] [CrossRef] [PubMed] [Google Scholar]
Agne M T, Imasato K, Anand S, et al. Heat capacity of Mg₃Sb₂, Mg₃Bi₂, and their alloys at high temperature. Mater Today Phys 2018; 6: 83-88. [Article] [Google Scholar]
Jiang J, Britton TB, Wilkinson A J. Evolution of dislocation density distributions in copper during tensile deformation. Acta Mater 2013; 61: 7227-7239. [Article] [Google Scholar]
Bacon DJ, Hull D. Introduction to Dislocations. Amsterdam: Elsevier, 2011 [Google Scholar]
Zhang BB, Yan FK, Zhao MJ, et al. Combined strengthening from nanotwins and nanoprecipitates in an iron-based superalloy. Acta Mater 2018; 151: 310-320. [Article] [Google Scholar]
Li D, Zhang JH, Li JM, et al. High thermoelectric performance for an Ag₂Se-based material prepared by a wet chemical method. Mater Chem Front 2020; 4: 875-880. [Article] [Google Scholar]
Yang D, Su X, Meng F, et al. Facile room temperature solventless synthesis of high thermoelectric performance Ag₂ Se via a dissociative adsorption reaction. J Mater Chem A 2017; 5: 23243-23251. [Article] [Google Scholar]
Liang J, Liu J, Qiu P, et al. Modulation of the morphotropic phase boundary for high-performance ductile thermoelectric materials. Nat Commun 2023; 14: 8442. [Article] [Google Scholar]
Liu W, Zhang Q, Lan Y, et al. Thermoelectric property studies on Cu-doped n-type Cu_xBi₂Te_2.7Se_0.3 nanocomposites. Adv Energy Mater 2011; 1: 577-587. [Article] [Google Scholar]
Hong M, Wang Y, Liu W, et al. Arrays of planar vacancies in superior thermoelectric Ge_1−x−yCd_xBi_yTe with band convergence. Adv Energy Mater 2018; 8: 1801837. [Article] [CrossRef] [Google Scholar]
Chen H, Shao C, Huang S, et al. High-entropy cubic pseudo-ternary Ag₂(S, Se, Te) materials with excellent ductility and thermoelectric performance. Adv Energy Mater 2024; 14: 2303473. [Article] [CrossRef] [Google Scholar]
Wang H, Pei Y, LaLonde AD, et al. Weak electron-phonon coupling contributing to high thermoelectric performance in n-type PbSe. Proc Natl Acad Sci USA 2012; 109: 9705-9709. [Article] [Google Scholar]
Wei TR, Tan G, Wu CF, et al. Thermoelectric transport properties of polycrystalline SnSe alloyed with PbSe. Appl Phys Lett 2017; 110: 053901. [Article] [CrossRef] [Google Scholar]
Yang S, Gao Z, Qiu P, et al. Ductile Ag₂₀S₇Te₃ with excellent shape-conformability and high thermoelectric performance. Adv Mater 2021; 33: 2007681. [Article] [CrossRef] [PubMed] [Google Scholar]

All Figures

Figure 1

(A) Average values of the compression strength and ultimate strain for Ag₂Se_1–xTe_x samples in this work (red stars); data of Ag₂Se [27,28,33], Ag₂Te [23,26], Ag₂Te_1–ySe_y [26] and Bi₂Te₃-based polycrystalline thermoelectric materials [6,12–14,17–19] are included for comparison. Raw data are listed in Table S1. (B) Comparison of mechanical and physical properties between Ag₂Se_0.9Te_0.1 and typical Bi₂Te₃-based polycrystalline thermoelectric materials [6,12].

In the text

Figure 2

(A) Compression strength, compression strain and bending strength for Ag₂Se_1–xTe_x samples. (B) Fracture toughness K_IC for Ag₂Se_1–xTe_x samples; data of Bi_0.5Sb_1.5Te₃ [6], Mg₃Sb_1.3Bi_0.7 [31], PbTe [34] are also given for comparison. (C) Schematic illustration of energy absorption (modulus of toughness) for Ag₂Se under compression test. (D) Modulus of toughness for Ag₂Se, Ag₂Se_0.9Te_0.1 and other typical thermoelectric materials [12,30,35]. The error bars in panels A, B, and D denote the standard deviation from multiple measurements.

In the text

Figure 3

Transmission electron microscope (TEM) analysis of Ag₂Se_0.9Te_0.1 sample with a compression strain 10%. (A) Bright-field image showing typical dislocations marked by red arrows. (B) HRTEM image and corresponding FFT image highlighting the dislocation array. (C) HRTEM image illustrating two sub-grains; inset images are FFT images. (D) Grain interface of the red area in Panel (C); two sets of planes are marked as red and yellow dots, respectively.

In the text

Figure 4

(A) Absolute Seebeck coefficient |S| versus carrier concentration n_H for Ag₂Se_1–xTe_x materials at 300 K. Data of other Ag₂Se-based materials are taken from Refs. [29,43]. The dashed line represents the calculated Pisarenko curve by the SPB model. (B) Relations of weighted mobility and lattice thermal conductivity with Te content; the dashed lines are calculated curves. (C) Temperature dependence of zT value for Ag₂Se_1–xTe_x samples with optimized Ag content. (D) zT value versus carrier concentration n_H for Ag₂Se_1–xTe_x materials at 300 K. Data of other Ag₂Se-based materials are taken from Refs. [29,43]. The dashed line represents the calculated Pisarenko curve by the SPB model.

In the text

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.