Altering the high-temperature stability and thermoelectric properties of Cu1.8S thermoelectric materials by Se incorporation

Xiang, Siqi; Liang, Yihan; Zhou, Miaolei; Zhang, Xinfang

doi:10.1016/j.jallcom.2022.164812

Cited by 8 publications

(5 citation statements)

References 24 publications

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“…13 Cu 1.8 S-based thermoelectric materials are believed not suitable for working at temperatures higher than 300 °C due to high temperature decomposition. 13,22 When we tested the σ of the sample with the main phase of Cu 1.8 S at different temperatures, we found that the σ of the sample decreased sharply over 300 °C, as shown in Figure 5a. From the DSC results in Figure 5b, it can be seen that the sample begins to be exothermic at about 350 °C and significantly exothermic at 400 °C.…”

Section: Thermal Decompositionmentioning

confidence: 94%

“…It is reported that the Cu 1.8 S material is unstable in an air or nitrogen environment above 300 °C and forms a mixture of Cu 2 O(SO 4 ) and Cu 2 S, Cu 7 S 4 . In the late 1960s, the Minnesota Mining and Manufacturing Company started to develop TEGs based on Ag-doped Cu 2 Se as the p-type material, while this material experienced sizable weight loss when exposed to heat and current flow, and the reason is believed to be Se evaporation. , The cause of instability of Cu 1.8 S at high temperature is caused by the evaporation of S, similar to Se evaporation in Cu 2 Se. At present, there are few reports on the thermal stability of cuprous sulfide materials.…”

Section: Introductionmentioning

confidence: 99%

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Controlling the Thermal Stability, Threshold Voltage, and Thermoelectric Properties of Cuprous Sulfide Thermoelectrics

et al. 2022

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Cu-ion liquid-like copper sulfide materials have excellent thermoelectric properties, while their applications are limited by their high-temperature decomposition and electric field-driven Cu precipitation issues. In particular, high thermoelectric properties and electric field-driven degradation are difficult to reconcile because liquid-like Cu ions are dominant in low κ and high ZT, while they cause electric field-driven degradation. Here, we control the sintering current and duration time to remove the Cu1.8S phase, thereby inhibiting the thermal decomposition of the copper sulfide samples, and introduce the Fe element into the sample matrix to improve its resistance to electric field-driven degradation. We reveal that the kinetic process of Cu1.8S phase decomposition can be suppressed by increasing the relative density of the sample or covering a layer of dense coating/film on the surface of the sample. However, as long as the Cu1.8S phase is present in the sample, it cannot maintain thermal stability above 450 °C. Furthermore, we find that the Fe element forms a nanogrid spinodal decomposition structure in the sample matrix, which acts as a barrier wall to prevent the long-range diffusion of liquid-like Cu ions and inhibit the electric field-driven degradation. The freely movable liquid-like Cu ions in the grid maintain a strong scattering of phonons in a short range, so the sample possesses low κ and high ZT. Then, a strategy to unify the high thermal decomposition temperature, high threshold voltage, and high thermoelectric performance of copper sulfide thermoelectric materials is proposed: transforming the Cu1.8S phase and introducing a liquid-like Cu ion migration barrier.

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Section: Thermal Decompositionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Controlling the Thermal Stability, Threshold Voltage, and Thermoelectric Properties of Cuprous Sulfide Thermoelectrics

et al. 2022

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“…The large off-stoichiometric number δ of Cu ions in Cu 2−δ X is conducive to maintaining a low Cu chemical potential and inhibiting its migration [18,19]. The experimental results demonstrate that Cu 1.8 S with large δ has good stability [14,20]. Cu 1.8 S remains stable for 72 h when the current density is 48 A cm −2 , whereas Cu 2 S exhibits Cu precipitation and cracks within 12 h when the current density is only 12 A cm −2 [14].…”

Section: Introductionmentioning

confidence: 92%

Enhanced thermoelectric properties and electrical stability for Cu1.8S-based alloys: Entropy engineering and Cu vacancy engineering

Zhou

Shan

et al. 2023

Sci. China Mater.

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Cu 1.8 S-based thermoelectric (TE) materials have garnered considerable interest due to their pollution-free, lowcost, and superior performance characteristics. However, high Cu vacancy and Cu migration inhibit their performance and electrical stability improvement. Through mechanical alloying and spark plasma sintering, a series of Cu 1.8 S and Mn x Cu 1.8 -S 0.5 Se 0.5 (0.01 ≤ x ≤ 0.06) bulk samples were prepared in this study. With Se alloying and Mn doping, the configuration entropy of Mn x Cu 1.8 S 0.5 Se 0.5 increases from low-entropy 0.4R * for pristine Cu 1.8 S to medium-entropy 1.2R * for Mn x Cu 1.8 S 0.5 -Se 0.5 . Mn x Cu 1.8 S 0.5 Se 0.5 subsequently crystallized in a cubic phase with enhanced symmetry and Mn solid solubility. High solubility enables the filling of excessive Cu vacancies, the reduction of carrier concentration, the adjustment of band structure, the enhancement of the Cu migration energy barrier, and the inhibition of Cu migration. Even at current densities exceeding 25 A cm −2 at 750 K, the resistance of Mn 0.03 Cu 1.8 S 0.5 Se 0.5 remained hardly changed, indicating a vastly improved electrical stability. In addition, the ultralow thermal conductivity of the lattice is achieved by decreasing the sound velocity and softening the lattice. At 773 K, the bulk ZT of Mn 0.06 Cu 1.8 S 0.5 Se 0.5 reaches a maximum of 0.79, which is twice that of pure Cu 1.8 S. The results indicate that combining entropy engineering and Cu vacancy engineering is an effective strategy for developing high-performance Cu 1.8 S TE materials.

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“…Solution processed 300 100 -200 --- [23] Solution processed 300 ~175 653 -- [26] Solution processed 300 --97.8 (x = 0.31) 120 (x = 0.48) - [25] Solution processed 300 ~125 --- [27] Ball milled & printed 300 50 250 (x = 0.10) [22] High-pressure, high-temperature 300 400 450 (x = 0.01) 540 (x = 0.03) [33] High-pressure, high-temperature 325 ~450 (x = 0.8, y = 0.2) ~200 (x = 1, y = 0.2) [18] Mechanical alloying & spark plasma sintering 325 600 270 -490 (15 -5 wt% Cu 2 S) [12] Mechanical alloying & spark plasma sintering 300 140 (x = 0.85) 50 (x = 1) [34] Mechanical alloying & spark plasma sintering 325 ~100 (y = 0.2) [35] Melting-annealing 340 700 -850 750 -- [6] Melting-annealing 300 600 700 450 -650 800 -1000 [9] Melting-annealing 300 -750 ~200 (x = 0.50) 775 -1125 (x < 0.20) [15][16][17] Pulsed laser deposition 325 844 [20] Wet-chemical synthesis, vacuum assisted filtration + cold pressing 300 270 a)…”

Section: Improved Seebeck Coefficient Stabilitymentioning

confidence: 99%

“…Although improving performance slightly, doping with elemental tin (Sn) and lithium (Li) did not produce clear improvements in stability. [13,14] Mao et al [9] and Zhao et al [15][16][17] explored sulfur (S) alloying as a route to Cu 2 Se stabilization, and showed that for melt-annealed samples, a slight Cu deficiency (Cu:Se ratio 1.96:1 as compared to stoichiometric 2:1) in combination with up to 20% selenium (Se) substitution with S was favorable both with regards to performance as well as material stability. Zhao et al [15] improved the power factor from ~750 µW m −1 K −2 for Cu 2 Se to ~1125 µW m −1 K −2 for Cu 2 S 0.06 Se 0.94 at 300 K. Mao et al [9] report power factors in the range ~600 µW m −1 K −2 for Cu 2-y Se and Cu 2-y S x Se 1-x and 800 -1000 µW m −1 K −2 for Cu 2 S x Se 1-x at 300 K. Exploring the sulfur-rich regime, Xiang et al [18] added Se to Cu 2-y S and improved the power factor at 325 K from ~200 µW m −1 K −2 for Cu 1.8 S to ~450 µW m −1 K −2 for Cu 1.8 S 0.8 Se 0.2 while reducing material decomposition.…”

Section: Introductionmentioning

confidence: 99%

Harnessing High Power Factors with Enhanced Stability in Heavy Metal-Free Solution-Processed Thermoelectric Copper Sulfoselenide Thin Films

Sahu¹

2022

MatLab

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Thermoelectric devices have the potential to recover waste heat from inefficient energy conversion processes. State-of-the-art thermoelectrics demonstrate low efficiency and incorporate materials containing rare and toxic elements. In this regard, p-type copper selenide (Cu 2 Se) has been identified as a promising and environmentally benign alternative. Unfortunately, the high diffusivity of liquid-like copper ions results in structural instability and performance degradation during operation, especially at moderate to high temperatures above 200 °C. Sulfur substitution has been utilized in melt-annealed samples to improve the stability of Cu 2 Se during operation, however this fabrication process is energy intensive and does not allow for use of flexible substrates. In this work, we report a solution-based direct thin film route to tune carrier concentration in copper sulfoselenide (Cu 2-y S x Se 1-x ) thin films by controlling sulfur content and degree of copper saturation. We observe that improved thermoelectric performance through copper saturation in nominally copper-deficient Cu 2-y Se films comes at a huge cost, with significantly reduced material stability due to enhanced copper migration resulting in severe degradation of the thermopower. Circumventing copper saturation, we show that controlled sulfur addition and tuning of annealing temperature has a synergistic effect, resulting in improved stability of the thermoelectric properties during continuous operation for mildly copper-deficient films while sustaining a high power factor of 800 μW/mK 2 at room temperature. Our results demonstrate a pathway for generating high performance solution processed thermoelectric devices with flexible form factors, and reinforce the case for Cu 2-y S x Se 1-x thin films as a heavy metal free alternative for scavenging low grade waste heat.

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Altering the high-temperature stability and thermoelectric properties of Cu1.8S thermoelectric materials by Se incorporation

Cited by 8 publications

References 24 publications

Controlling the Thermal Stability, Threshold Voltage, and Thermoelectric Properties of Cuprous Sulfide Thermoelectrics

Controlling the Thermal Stability, Threshold Voltage, and Thermoelectric Properties of Cuprous Sulfide Thermoelectrics

Enhanced thermoelectric properties and electrical stability for Cu1.8S-based alloys: Entropy engineering and Cu vacancy engineering

Harnessing High Power Factors with Enhanced Stability in Heavy Metal-Free Solution-Processed Thermoelectric Copper Sulfoselenide Thin Films

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