A Cu 1.8 S and Cu 1.96 S-composite thermoelectric materials and their preparation methods

Abstract

This invention discloses a Cu 1.8 S and Cu 1.96 The preparation method of S composite thermoelectric material includes adding CuCl powder and Na2S2O3 powder to deionized water for hydrothermal reaction, and after the reaction is completed, filtering and drying to obtain Cu 1.8 S powder; Cu 1.8 Cu was obtained by hot pressing and sintering S powder. 1.8 S and Cu 1.96 The S-composite thermoelectric material is prepared by hot-pressing at a temperature of 700-900℃ for 15-60 minutes. The Cu obtained by this method... 1.8 S and Cu 1.96 S-composite thermoelectric materials have lower thermal conductivity and a ZT value compared to Cu. 1.8 S has been significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials technology, specifically relating to a Cu 1.8 S and Cu 1.96 S-composite thermoelectric materials and their preparation methods. Background Technology

[0002] With the rapid growth of the world's population, economy, and industrial production, limited fossil fuels can no longer meet the ever-increasing energy demands of today's society. Therefore, finding an efficient and clean energy source and building a sustainable society has become one of the key themes for countries in the 21st century. According to incomplete statistics, approximately 60% of global energy is emitted as waste heat. If this waste heat can be effectively utilized, it will undoubtedly drive further growth in global industry and the economy.

[0003] Thermoelectric materials are a novel type of energy conversion medium, and thermoelectric devices made from them can achieve the interconversion of thermal energy and electrical energy. Thermoelectric devices have advantages such as no moving parts, no noise, high reliability, and flexibility, and have extremely broad application prospects in aerospace, defense, automotive, and medical fields. The conversion efficiency η of a thermoelectric device is related to the thermoelectric figure of merit ZT of the material and the temperature T at both ends of the device. H T C It is related to the temperature difference and the ZT value. Generally speaking, η is proportional to the temperature difference and the ZT value. However, the conversion efficiency of current thermoelectric devices is generally low, with the highest reported conversion efficiency being only 15%, which is far from the efficiency of traditional internal combustion engines.

[0004] Although thermoelectric materials have been studied for nearly 200 years, they (especially power generation devices) have not yet been industrialized on a large scale, primarily due to their low thermoelectric conversion efficiency. When the temperature difference between the hot and cold ends is fixed, the thermoelectric conversion efficiency is measured solely by ZT, which can be expressed as ZT = S 2 σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity. κ is primarily determined by the electronic thermal conductivity. e and lattice thermal conductivity κ l The composition of thermoelectricity is complex. The three parameters S, σ, and κ have a complex coupling relationship. Breaking this interdependence to achieve independent control of electrons and phonons is the focus of current thermoelectric research.

[0005] Thermoelectric materials can realize the interconversion between thermal energy and electrical energy, and are a new type of energy conversion medium. Thermoelectric devices constructed using thermoelectric materials can be used for thermoelectric power generation and semiconductor refrigeration. In recent years, Cu... 2-x M (M = S, Se, Te)-based compounds have gained significant attention in the thermoelectric field due to their excellent thermoelectric properties, abundant elemental reserves, and high cost-effectiveness. Among these, Cu... 2-xS compounds are abundant in natural minerals, and both Cu and S are non-toxic and environmentally friendly elements, aligning with current environmental protection principles. Currently reported Cu₂S-based thermoelectric materials with trace vacancies exhibit extremely high thermoelectric performance; however, during long-term current erosion, Cu ions undergo directional migration and eventually precipitate at one end of the material, leading to device performance degradation. 1.8 Cu₂S possesses an intrinsically high concentration of Cu vacancies, exhibiting excellent current stability; however, its thermal conductivity is slightly higher than that of Cu₂S, resulting in a much lower ZT (Zero-Temperature) than Cu₂S. Therefore, while maintaining Cu… 1.8 The key to the application of this material is to reduce its thermal conductivity while maintaining its excellent electrical properties. Summary of the Invention

[0006] This invention provides a Cu 1.8 S and Cu 1.96 A method for preparing S-composite thermoelectric materials, wherein Cu is prepared by this method. 1.8 S and Cu 1.96 S-composite thermoelectric materials have lower thermal conductivity and a ZT value compared to Cu. 1.8 S has been significantly improved.

[0007] This invention provides a Cu 1.8 S and Cu 1.96 The preparation method of S composite thermoelectric material includes:

[0008] CuCl powder and Na2S2O3 powder were added to deionized water for a hydrothermal reaction. After the reaction was completed, the mixture was filtered and dried to obtain Cu. 1.8 S powder;

[0009] Cu 1.8 Cu was obtained by hot pressing and sintering S powder. 1.8 S and Cu 1.96 The S-composite thermoelectric material is hot-pressed at a temperature of 700-900℃ for a time of 15-60 minutes.

[0010] Preferably, the hot-pressing sintering temperature is 800-900℃. By further controlling the hot-pressing sintering temperature, a larger amount of the second-phase Cu is incorporated. 1.96 The introduction of sulfur (S) significantly reduces thermal conductivity. The composite material provided by this invention, along with Cu... 1.8 Compared to thermoelectric materials, S exhibits little change in electrical conductivity, resulting in a significant increase in ZT value.

[0011] Preferably, the pressure of the hot pressing sintering is 50-100 MPa.

[0012] Preferably, the molar ratio of CuCl powder to Na2S2O3 powder is greater than or equal to 0.5. Using the hydrothermal method provided by this invention, sufficient Na2S2O3 powder can be provided to form CuCl powder. 1.8 S powder has a simple and efficient preparation method.

[0013] More preferably, the molar ratio of CuCl powder to Na2S2O3 powder is 0.5-2.

[0014] Preferably, the hydrothermal reaction temperature is 120-240℃ and the reaction time is 6-24h.

[0015] On the other hand, the present invention provides a Cu 1.8 S and Cu 1.96 S-composite thermoelectric material, through the Cu 1.8 S and Cu 1.96 The S-composite thermoelectric material was prepared using a specific method.

[0016] Preferably, the Cu 1.8 S and Cu 1.96 The Seebeck coefficient of the S-composite thermoelectric material is 50–200 μV / K in the range of 200–600 K, and its electrical conductivity is 4 × 10⁻⁶. 4 ~1.3×10 5 S / m, thermal conductivity 1.5~3.0W / m K, thermoelectric figure of merit ZT 0.6~0.9.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This invention controls the temperature and time of hot pressing sintering in Cu... 1.8 A suitable amount of second-phase Cu is formed in situ on S. 1.96 S, and Cu at high temperature 1.8 S grains break down, forming multiple grain boundaries and pores. Therefore, in Cu with lower thermal conductivity... 1.96 The synergistic effect of S and the multiple grain boundaries and pores formed in hindering heat conduction significantly reduces the intrinsic thermal conductivity. Simultaneously, this invention also ensures an appropriate amount of Cu... 1.8 S maintains a high conductivity, thereby enabling the Cu provided by the present invention to achieve this. 1.8 S and Cu 1.96 S-composite thermoelectric materials have a high ZT value. Attached Figure Description

[0019] Figure 1 Cu obtained in Example 1 of this invention 1.8 XRD and SEM images of S, where... Figure 1 (a) Cu prepared in Example 1 1.8XRD pattern of S Figure 1 (b) and Figure 1 (c) Cu prepared in Example 1 1.8 SEM image of S;

[0020] Figure 2 The images show the XRD patterns of the composite thermoelectric materials prepared in Examples 1-3 of this invention and the thermoelectric material prepared in Comparative Example 1.

[0021] Figure 3 The electrical conductivity, Seebeck coefficient, power factor (PF), thermal conductivity (k), and lattice thermal conductivity (K) of the composite thermoelectric materials prepared in Examples 1-3 and the thermoelectric material prepared in Comparative Example 1 of this invention are described. L ) and ZT curve, where, Figure 3 (a) is a conductivity curve. Figure 3 (b) is a graph of the Seebeck system. Figure 3 (c) is a power factor (PF) curve. Figure 3 (d) is the thermal conductivity (k) curve. Figure 3 (e) represents the lattice thermal conductivity (K). L (curve graph) Figure 3 (f) is the ZT curve. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] Example 1

[0024] Step 1: Weigh 6g of CuCl powder with a purity greater than 99% and 8g of Na2S2O3 powder. Put the powder into a 50ml polytetrafluoroethylene-lined reactor and add 30ml of deionized water.

[0025] Step 2: Seal the reactor and store it in an oven at 200℃ for 10 hours.

[0026] Step 3: After the reaction is complete, filter to obtain blue Cu. 1.8 S powder, such as Figure 1 (a)- Figure 1 As shown in (c), the powder obtained by filtration in this embodiment is Cu. 1.8 S powder.

[0027] Step 4: Place the powder in a 60℃ oven and dry for 3 hours.

[0028] Step 5: Hot-press sinter the dried powder using a hot-press sintering furnace to obtain Cu. 1.8 S-Cu 1.96For S-composite block thermoelectric material, the powder is first poured into a mold with a diameter of 12.7 mm, and the hot pressing sintering temperature is 700℃, the pressure is 75MPa, and the hot pressing time is 30min.

[0029] Example 2

[0030] Unlike Example 1, the hot pressing sintering temperature was 800°C.

[0031] Example 3

[0032] Unlike Example 1, the hot pressing sintering temperature was 900°C.

[0033] Comparative Example 1

[0034] Unlike Example 1, the hot pressing sintering temperature was 600°C, yielding Cu. 1.8 S-thermoelectric materials.

[0035] Performance Analysis:

[0036] like Figure 2 As shown, a comparison using PDF cards reveals that the thermoelectric materials obtained in Examples 1-3 (i.e., at HP of 700-800℃) are Cu. 1.8 S and Cu 1.96 S-composite thermoelectric material, while Comparative Example 1, i.e., thermoelectric material prepared at HP of 600℃, is Cu. 1.8 S.

[0037] The performance of the thermoelectric material provided in the specific embodiments of the present invention is characterized by the dimensionless thermoelectric figure of merit ZT, where ZT = S 2 σT / κ, where S 2 σ represents the power factor (σ is electrical conductivity, S is the Seebeck coefficient), T is the absolute temperature, and κ is the thermal conductivity (lattice thermal conductivity κ). l and electronic thermal conductivity κ e sum).

[0038] The electrical transmission performance testing method provided in a specific embodiment of the present invention involves cutting the hot-pressed block into strips of 2*2*10mm for testing electrical conductivity and Seebeck coefficient.

[0039] like Figure 3 (a)- Figure 3 As shown in (c), the composite electrothermal materials prepared in Examples 1-3 and the composite electrothermal materials prepared in Comparative Example 1 show almost no change in conductivity and Seebeck coefficient above 300 degrees Celsius, and the calculated power factor shows little change.

[0040] The method for testing thermal conductivity provided in a specific embodiment of the present invention involves cutting the bulk thermoelectric material prepared in the embodiment into... A 2mm thick circular disc was used to test thermal conductivity, which was performed using a laser thermal conductivity meter.

[0041] like Figure 3 (d)- Figure 3 As shown in (e), Cu was introduced in Examples 1-3. 1.96 S, thermal conductivity decreases significantly. (Formula S above) 2 The ZT value can be obtained by calculating σT / κ, such as Figure 3 As shown in (f), the thermoelectric figure of merit ZT of the composite materials obtained in Examples 1-3 is significantly higher than that of the Cu obtained in Comparative Example 1. 1.8 When the hot-pressing sintering temperature of the S-thermoelectric material reaches 900℃, the highest ZT value of the corresponding composite thermoelectric material reaches 1.1.

[0042] For those skilled in the art, without departing from the concept of the technical solution of this invention, several modifications and improvements can be made, and these should also be considered within the scope of protection of this invention. These will not affect the effectiveness of the implementation of this patent or the practicality of the patent.

Claims

1. A Cu 1.8 S and Cu 1.96 The method for preparing S-composite thermoelectric materials is characterized by... include: CuCl powder and Na2S2O3 powder were added to deionized water for a hydrothermal reaction. After the reaction was completed, the mixture was filtered and dried to obtain Cu. 1.8 S powder; Cu 1.8 Cu was obtained by hot pressing and sintering S powder. 1.8 S and Cu 1.96 The S-composite thermoelectric material is hot-pressed at a temperature of 700-900℃ for a time of 15-60 minutes. The pressure for hot pressing and sintering is 50-100 MPa; The molar ratio of CuCl powder to Na2S2O3 powder is 0.5-2; The hydrothermal reaction is carried out at a temperature of 120-240℃ for 6-24 hours.

2. The Cu according to claim 1 1.8 S and Cu 1.96 The method for preparing S-composite thermoelectric materials is characterized by... The hot pressing sintering temperature is 800-900℃.

3. A Cu 1.8 S and Cu 1.96 S-composite thermoelectric material, characterized in that... Cu according to any one of claims 1-2 1.8 S and Cu 1.96 The S-composite thermoelectric material was prepared using a specific method.

4. The Cu according to claim 3 1.8 S and Cu 1.96 S-composite thermoelectric material, characterized in that... The Cu 1.8 S and Cu 1.96 The Seebeck coefficient of the S-composite thermoelectric material is 50–200 μV / K in the range of 200–600 K, and its electrical conductivity is 4 × 10⁻⁶. 4 ~1.3×10 5 The thermal conductivity is 1.5–3.0 W / m K, and the thermoelectric figure of merit (ZT) is 0.6–0.9.

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