A silver-based chalcogenide plastic thermoelectric material and its preparation method

Abstract

This invention relates to a silver-based chalcogenide plastic thermoelectric material and its preparation method. The silver-based chalcogenide plastic thermoelectric material is Ag. 2‑x S 0.7 Te 0.3 The preparation process includes the following steps: Ag powder, S powder, and Te powder are weighed in an argon-filled glove box and placed into a stainless steel ball mill jar, which is then sealed. After high-energy ball milling, the milled product is removed and placed into a quartz tube. The tube is then vacuum-sealed using a vacuum sealing system and subsequently transferred to a muffle furnace for annealing at 380–580°C for three days. After furnace cooling, the material is sintered using spark plasma sintering technology at 300–500°C and a pressure of 40–60 MPa for 15–25 minutes to obtain a silver-based chalcogenide plastic thermoelectric material. This invention utilizes a high-energy ball milling method to achieve Ag… 2‑x S 0.7 Te 0.3 The method for preparing plastic thermoelectric materials is simple to operate, can be used for large-scale preparation, and requires simple preparation equipment.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric energy conversion materials, specifically relating to a silver-based chalcogenide plastic thermoelectric material and its preparation method. Background Technology

[0002] Thermoelectric conversion technology, as a green energy conversion technology, can directly convert heat energy into electrical energy based on the Seebeck and Peltier effects. This means it can convert low-grade heat energy, such as environmental waste heat and human body heat, into usable electrical energy. It can also be applied to solid-state refrigeration and precise temperature control. Thermoelectric materials, as the carriers of energy conversion, have their conversion efficiency influenced by the dimensionless thermoelectric figure of merit (zT), where zT = S. 2 σT / κ, where T is the absolute temperature, σ is the conductivity, and S is the Seebeck coefficient. 2 σ represents the power factor, and κ represents the thermal conductivity (composed of electronic thermal conductivity and lattice thermal conductivity). Traditional thermoelectric materials typically exhibit intrinsic brittleness, making it difficult to achieve good contact with heat source surfaces with complex shapes. This affects the efficient collection, conversion, and utilization of heat, limiting the service scenarios and operational stability of thermoelectric materials and devices, and hindering the development and application of thermoelectric conversion technology. Therefore, the development of flexible thermoelectric materials and devices has become an important direction in the thermoelectric field in recent years. Developing materials that combine high thermoelectric performance with excellent mechanical properties is key to the research of flexible thermoelectric materials. Among them, the thermoelectric performance of organic conductive polymers is generally lower than that of inorganic materials; thin-film flexible thermoelectric materials often have complex fabrication processes, and their performance stability is limited by the tightness of the bonding between the material and the flexible substrate. The service environment is also constrained to some extent by the flexible substrate. Therefore, finding high-performance inorganic thermoelectric materials with intrinsic flexibility is an important direction in the research field of flexible thermoelectrics.

[0003] Studies have found that Ag₂S is a room-temperature inorganic plastic semiconductor material that can be easily bent and twisted, exhibiting excellent intrinsic plasticity, but its electrical conductivity is poor. In recent years, researchers have attempted to improve the thermoelectric properties of Ag₂S by dissolving Se and Te elements, discovering a series of silver-based chalcogenide thermoelectric materials that combine flexibility and thermoelectric performance. Therefore, the thermoelectric properties of silver-based chalcogenide plastic materials can be optimized through compositional control, and the influence of compositional changes on the material's mechanical properties can be explored. Furthermore, regarding preparation methods, currently reported silver-based chalcogenide plastic thermoelectric materials are prepared using a high-temperature melting method, which suffers from drawbacks such as high energy consumption and long processing time. High-energy ball milling, on the other hand, offers advantages such as high efficiency, energy saving, and speed. This method can also yield materials with smaller grain sizes, thus facilitating the achievement of low lattice thermal conductivity and improving the zT value. The key issues that urgently need to be addressed are: determining the composition of silver-based chalcogenide plastic thermoelectric materials, exploring the process for preparing silver-based chalcogenide plastic thermoelectric materials using high-energy ball milling, and how to synergistically optimize the thermoelectric and mechanical properties of silver-based chalcogenide plastic thermoelectric materials. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention focuses on Ag 2-x S 0.7 Te 0.3 Controllable, large-scale, and low-cost preparation of silver-based chalcogenide plastic thermoelectric materials, as well as optimization of their thermoelectric and mechanical properties, to address the challenges in improving the performance of silver-based chalcogenide plastic thermoelectric materials.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing a silver-based chalcogenide plastic thermoelectric material, wherein the silver-based chalcogenide plastic thermoelectric material is Ag. 2-x S 0.7 Te 0.3 Its preparation method includes the following steps:

[0006] S1: In an argon-filled glove box, weigh Ag powder, S powder, and Te powder according to the molar ratio in their chemical formulas and place them into a stainless steel ball mill jar. Then seal the ball mill jar. Here, x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05.

[0007] S2: Place the ball mill jar in a ball mill for high-speed ball milling for 8 hours, and after it cools down, place it in a glove box to remove the product; specifically, place the ball mill jar in a ball mill with a rotation speed of 1500 rpm for high-energy ball milling for at least 8 hours.

[0008] S3: The product obtained in S2 is placed into a quartz tube, vacuumed using a vacuum sealing system, and then sealed. The vacuum level is below 5.9 × 10⁻⁶. -2 mbar.

[0009] S4: Transfer the sealed quartz tube to the muffle furnace and set the annealing program: heat to 380-580℃ at a slow heating rate, hold for three days, and then let it cool naturally to room temperature with the furnace.

[0010] S5: The annealed product obtained in S4 was sintered by spark plasma sintering at a temperature of 300–500℃ and a pressure of 40–60 MPa for 15–25 min to obtain Ag. 2-x S 0.7 Te 0.3 Plastic thermoelectric bulk material.

[0011] As an improvement, the molar ratio of Ag powder, S powder and Te powder in S1 is 2:0.7:0.3, 1.99:0.7:0.3, 1.98:0.7:0.3, 1.97:0.7:0.3, 1.96:0.7:0.3 and 1.95:0.7:0.3.

[0012] A silver-based chalcogenide plastic thermoelectric material, wherein the silver-based chalcogenide plastic thermoelectric material is Ag. 2- x S 0.7 Te 0.3 The high-performance silver-based chalcogenide plastic thermoelectric material is prepared by the above method, wherein x = 0 to 0.05.

[0013] Specifically, x = 0, 0.01, 0.02, 0.03, 0.04, or 0.05.

[0014] Compared with the prior art, the present invention has at least the following advantages:

[0015] 1. This invention selects the silver-based chalcogenide Ag2S, which combines excellent mechanical properties with good thermoelectric properties. 0.7 Te 0.3 The high-energy ball milling-annealing-discharge plasma sintering technology was used to achieve the successful and controllable preparation of this compound. The corresponding synthesis method is simple to operate and can be prepared in large quantities. At the same time, the prepared sample has uniform elemental distribution and stable structure and properties. Moreover, the high-energy ball milling process is carried out at room temperature, which is significantly lower than the temperature required by the traditional high-temperature melting method (500-1000℃) and the time consumed is shorter than that of the high-temperature melting method (more than 8 days).

[0016] 2. This invention obtains a novel silver-based chalcogenide plastic thermoelectric material composition through component regulation, and optimizes the carrier concentration and thermal conductivity of the material system.

[0017] 3. The novel silver-based chalcogenide plastic thermoelectric material obtained by this invention has a high z-T peak value and excellent plastic deformation ability, wherein Ag 1.95S 0.7 Te 0.3 The sample's zT peak (623 K) was 1.26, while all Ag... 2-x S 0.7 Te 0.3 The material can achieve more than 80% compressive strain in uniaxial compression tests. Attached Figure Description

[0018] Figure 1 For Ag 2-x S 0.7 Te 0.3 XRD patterns of the blocks (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05).

[0019] Figure 2 For Ag 2-x S 0.7 Te 0.3 (x = 0, 0.02, 0.04, 0.05) Room temperature thermoelectric properties of the bulk material: (a) electrical conductivity, (b) Seebeck coefficient, (c) power factor, (d) thermal conductivity.

[0020] Figure 3 For Ag 2-x S 0.7 Te 0.3 (x=0,0.02,0.04,0.05) The thermoelectric figure of merit of the bulk at 623K.

[0021] Figure 4 Ag prepared by the method of the present invention 1.95 S 0.7 Te 0.3 Room temperature deformation capability.

[0022] Figure 5 This is a simplified flowchart of the method of the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail.

[0024] Ag₂S is a room-temperature inorganic plastic semiconductor material that can be easily bent and twisted, exhibiting excellent plasticity. However, its poor electrical properties limit its application in thermoelectric fields. By dissolving Se and Te elements in Ag₂S, its thermoelectric properties can be optimized without sacrificing its mechanical properties. Further optimization of the carrier concentration through composition control can enhance the thermoelectric performance. This invention achieves Ag₂S… 2-x S 0.7 Te 0.3 Controllable preparation of silver-based chalcogenide plastic thermoelectric materials.

[0025] The following is a detailed explanation of Ag2-x S 0.7 Te 0.3 Preparation of materials (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05):

[0026] Example 1: Ag2S 0.7 Te 0.3 Material preparation process:

[0027] 1) Weigh 3.4528g of Ag powder, 0.3591g of S powder, and 0.6125g of Te powder into a stainless steel ball mill jar in an argon-filled glove box according to the molar ratio of Ag powder, S powder, and Te powder of 2:0.7:0.3, and then seal the ball mill jar.

[0028] 2) The ball mill jar was placed on a ball mill with a power of 245W for ball milling reaction. The ball milling program was set to 80min×1+100min×4, for a total of 5 ball milling cycles. There was a 20min pause between each rotation cycle, and then the next cycle of ball milling was carried out, for a total ball milling time of 8 hours. The ball mill speed was 1500 rpm.

[0029] 3) After the last cycle is completed, wait for the ball mill jar to cool down and then put it into the glove box to remove the product;

[0030] 4) Load the ball-milling product into a quartz tube, and use a vacuum sealing system to evacuate to a vacuum level below 5.9 × 10⁻⁶. - 2 After mbar, encapsulation is performed;

[0031] 5) The encapsulated quartz tube was then transferred to a muffle furnace for annealing, with the heating program set to 1℃·min. -1 The heating rate was increased to 480℃, and the temperature was held at 480℃ for three days, after which the furnace was naturally cooled to room temperature.

[0032] 6) The annealed material is subjected to spark plasma sintering at 400℃ and 50MPa for 20 minutes to obtain Ag2S. 0.7 Te 0.3 Bulk materials.

[0033] The preparation process of Examples 2-30 is the same as that of Example 1, except for the ratio of raw materials (Ag content) and the selection of process parameters (annealing temperature, sintering temperature, sintering pressure and sintering time), as detailed in Table 1.

[0034] It should be noted that the purpose of high-energy ball milling in S2 is to facilitate better chemical reactions in the raw material powder. The inventors discovered through numerous tests that only 8 hours of high-speed ball milling is needed to complete the chemical reactions between monomers. The choice of ball mill significantly affects the Ag yield obtained from the process.2-x S 0.7 Te 0.3 The performance impact of silver-based chalcogenide plastic thermoelectric materials is very small.

[0035] Table 1

[0036]

[0037]

[0038] Figure 1 It is Ag 2-x S 0.7 Te 0.3 (x=0,0.01,0.02,0.03,0.04,0.05) XRD patterns of bulk materials, Ag 2- x S 0.7 Te 0.3 The bulk XRD pattern of the (x=0~0.04) component shows only three distinct diffraction peaks in the range of 2θ=20~60°, which basically correspond to the cubic phase β-Ag2S (PDF 71-0995); Ag 1.95 S 0.7 Te 0.3 The XRD patterns of the components show diffraction peaks that are similar to those of the monoclinic α-Ag₂S (PDF 89-3840) and the cubic β-Ag₂S. These peaks correspond to the (200), (211), and (220) crystal planes of the β-Ag₂S phase, as well as most of the characteristic diffraction peaks of the α-Ag₂S phase, indicating that Ag₂S... 1.95 S 0.7 Te 0.3 Both monoclinic and cubic phases exist simultaneously. Furthermore, bulges were observed in the XRD patterns of all components within the range of 2θ = 30–38°, indicating that Ag... 2-x S 0.7 Te 0.3 Amorphous structures are present in all materials. XRD results confirm that the high-energy ball milling-annealing-spark plasma sintering process successfully produced Ag. 2-x S 0.7 Te 0.3 Synthesis of silver-based chalcogenide thermoelectric materials.

[0039] Figure 2 For Ag 2-x S 0.7 Te 0.3 (x = 0, 0.02, 0.04, 0.05) Room temperature thermoelectric properties of the bulk material. From Figure 2 As can be seen from a, as the Ag content decreases, Ag... 2-x S0.7 Te 0.3 The formation of Ag vacancies in the sample reduces the carrier concentration in the material, which in turn reduces the room temperature conductivity.

[0040] Figure 2 b in Ag 2-x S 0.7 Te 0.3 (x=0,0.02,0.04,0.05) The room temperature Seebeck coefficients of the bulk samples are all negative, indicating that all samples are n-type semiconductors, and their absolute values ​​show a trend opposite to that of conductivity.

[0041] Figure 2 c shows Ag 2-x S 0.7 Te 0.3 (x = 0, 0.02, 0.04, 0.05) represents the room-temperature power factor of the bulk material. The power factor is influenced by both the Seebeck coefficient and the conductivity. Wherein, Ag... 1.98 S 0.7 Te 0.3 The component with the highest power factor at room temperature was 0.38 mW·m. -1 ·K -2 .

[0042] Figure 2 d is Ag 2-x S 0.7 Te 0.3 (x = 0, 0.02, 0.04, 0.05) represents the total thermal conductivity of the bulk material at room temperature. It can be seen that Ag... 2-x S 0.7 Te 0.3 The material has low thermal conductivity, and the Ag content decreases as the Ag content decreases. 2-x S 0.7 Te 0.3 The overall thermal conductivity of the material also decreases accordingly.

[0043] Figure 3 Ag was displayed 2-x S 0.7 Te 0.3 (x = 0, 0.02, 0.04, 0.05) represents the thermoelectric figure of merit of the bulk material at 623 K. Where Ag... 1.95 S 0.7 Te 0.3 The component material achieved a maximum zT of 1.26 at 623 K. These results confirm that the component regulation method of this invention can indeed significantly enhance Ag... 2-x S 0.7 Te 0.3 zT value of silver-based chalcogenide plastic thermoelectric material.

[0044] Figure 4 This invention demonstrates the preparation of Ag2S by the method of the present invention. 0.7 Te 0.3 and Ag 1.95 S 0.7 Te 0.3 The material exhibits good room temperature deformation capacity. It can be seen that the material can be bent and twisted, withstanding significant deformation without being damaged, indicating that it possesses good plasticity and toughness.

[0045] The inventors obtained Ag in some of the embodiments 2-x S 0.7 Te 0.3 The silver-based chalcogenide plastic thermoelectric material underwent uniaxial compression testing, and the mechanical property test results are shown in Table 2.

[0046] Table 2

[0047] Example <![CDATA[Ag 2-x S 0.7 Te 0.3 Silver-based chalcogenide plastic thermoelectric materials Compression engineering strain Example 1 <![CDATA[Ag2S 0.7 The 0.3 ]]> >80％ Example 9 <![CDATA[Ag 1.99 S 0.7 Tea 0.3 ]]> >80％ Example 14 <![CDATA[Ag 1.98 S 0.7 Tea 0.3 ]]> >80％ Example 19 <![CDATA[Ag 1.97 S 0.7 Tea 0.3 ]]> >80％ Example 22 <![CDATA[Ag 1.96 S 0.7 Tea 0.3 ]]> >80％ Example 27 <![CDATA[Ag 1.95 S 0.7 Tea 0.3 ]]> >80％

[0048] Table 2 shows that: all Ag 2-x S 0.7 Te 0.3 The material can achieve more than 80% of the compressive strain in uniaxial compression tests, and has excellent plastic deformation capacity.

[0049] In summary, the above results demonstrate that the high-energy ball milling-annealing-spark plasma sintering technology of this invention successfully achieved Ag… 2-x S 0.7 Te 0.3 The synthesis of silver-based chalcogenide plastic thermoelectric materials was carried out, and excellent thermoelectric properties were obtained through compositional control. Furthermore, all Ag... 2-x S 0.7 Te 0.3 All materials exhibit excellent plastic deformation behavior.

[0050] Based on the Ag2S-Ag2Te pseudo-binary phase diagram, Ag obtained by high-energy ball milling 2-x S 0.7 Te 0.3 During the annealing process, the material undergoes slow heating at a certain rate and is held at a specific temperature, allowing for the full diffusion of various elements and achieving a degree of uniform element distribution. Furthermore, annealing can eliminate residual stress in the ball-milled product to some extent, improving the material's thermal stability and mechanical deformation capacity. The high-temperature, high-pressure process of spark plasma sintering further promotes material densification, significantly impacting its thermal stability and homogeneity, thus contributing to excellent thermoelectric properties.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a silver-based chalcogenide plastic thermoelectric material, characterized in that: The silver-based chalcogenide plastic thermoelectric material is Ag. 2-x S 0.7 Te 0.3 Its preparation method includes the following steps: S1: In an argon-filled glove box, weigh Ag powder, S powder, and Te powder according to the molar ratio in their chemical formulas, then place them into a stainless steel ball mill jar. Seal the jar. x =0.01 ~ 0.05, the molar ratio of Ag powder, S powder, and Te powder is 1.95 ~ 1.99:0.7:0.3; S2: Place the ball milling jar in the ball mill for at least 8 hours of high-energy ball milling, and after it cools down, place it in the glove box to remove the ball milling product; S3: The ball-milled product is loaded into a quartz tube, vacuumed using a vacuum sealing system, and then sealed. The vacuum level is < 5.9 × 10⁻⁶. -2 mbar; S4: Transfer the encapsulated quartz tube to a muffle furnace and set the annealing program: heat to 380~580 ℃ at a slow heating rate, hold for three days, and then let it cool naturally to room temperature with the furnace. S5: Using spark plasma sintering technology, the annealed product obtained in S4 is sintered at a temperature of 300~500 ℃ and a pressure of 40~60 MPa for 15~25 min to obtain Ag. 2-x S 0.7 Te 0.3 Plastic thermoelectric bulk material.

2. The method for preparing a silver-based chalcogenide plastic thermoelectric material as described in claim 1, characterized in that: The molar ratio of Ag powder, S powder, and Te powder in S1 is 1.99:0.7:0.3, 1.98:0.7:0.3, 1.97:0.7:0.3, 1.96:0.7:0.3, or 1.95:0.7:0.

3.

3. A silver-based chalcogenide plastic thermoelectric material, characterized in that, The silver-based chalcogenide plastic thermoelectric material is Ag. 2-x S 0.7 Te 0.3 The silver-based chalcogenide plastic thermoelectric material is prepared by the method described in claim 1 or 2, wherein... x =0.01 ~ 0.05.

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