Preparation method and application of high-performance Te-doped CuAgSe thermoelectric material

Abstract

The invention discloses a preparation method of a high-performance Te-doped CuAgSe thermoelectric material, and the method comprises the following steps: S1, mixing selenium powder and tellurium powder according to a set proportion, adding a sodium borohydride solution, and stirring until the mixture is completely dissolved to obtain a selenium-tellurium mixed precursor solution; s2, mixing copper nitrate trihydrate and silver nitrate according to a preset proportion, and adding a solvent for dissolving to obtain a copper-silver mixed precursor solution; s3, under a stirring condition, rapidly injecting the copper-silver mixed precursor solution into the selenium-tellurium mixed precursor solution according to a stoichiometric ratio, and carrying out a reaction at room temperature to form a suspension; and S4, carrying out centrifugal separation on the suspension, washing and drying to obtain Te-doped CuAgSe nano composite material powder. The Te-doped CuAgSe nano composite material is prepared by adopting a surfactant-free water phase synthesis method for the first time, the operation is carried out at room temperature, the step of high-temperature annealing or ligand removal is not needed, the synthesis cost is reduced by more than 30%, the product purity is high (no organic residue exists), and the method is suitable for large-scale production. Through Te doping induced lattice distortion and defect engineering, the lowest lattice thermal conductivity is 0.11 W.m <-1 >. K <-1 >, the peak value zT is 0.68, the average zT is 0.5, and the performance index is obviously superior to that of the prior art.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric materials and devices, and specifically to a method for preparing a high-performance Te-doped CuAgSe thermoelectric material and its application. Background Technology

[0002] Thermoelectric materials achieve the conversion of heat energy into electrical energy through the Seebeck and Peltier effects. Initially developed for deep space exploration missions to provide long-term, reliable, and maintenance-free power sources, their applications have expanded to solid-state refrigeration and thermal management technologies in recent years. With their compact structure and scalability, they offer unique competitive advantages over compression refrigeration systems. The properties of thermoelectric materials are determined by the dimensionless thermoelectric figure of merit. zT Characterization: zT = (S²σ / κ)T in, T It is absolute temperature. S It is the Seebeck coefficient. σ It is electrical conductivity. κ It is the total thermal conductivity, the total thermal conductivity ( κ ) is determined by electronic thermal conductivity ( k e ) and lattice thermal conductivity ( k L Thermoelectric materials consist of two parts, and there are two main methods to optimize their performance: reducing lattice thermal conductivity (…). k L ) and improve thermoelectric power factor ( PF=S²σ However, it should be emphasized that these performance parameters are interconnected through the charge carriers inside the material. Optimizing any one parameter will inevitably affect the other parameters, posing a challenge to performance control.

[0003] In thermoelectric refrigeration applications, high temperature is present near room temperature. zT While materials with high crystallinity are ideal, their limited quantity and inherent defects lead to decreased device performance or hinder practical applications. In near-room temperature (298–443 K) thermoelectric material systems, Bi₂Te₃-based alloys are currently the most technologically mature type, but their strong anisotropy in crystallization necessitates precise orientation control during device fabrication, increasing application difficulty. Although Ag₂Se materials possess high... zT While it has a high efficiency value, it undergoes a phase transition at 406 K and exhibits poor mechanical properties, resulting in a narrow effective operating temperature window that limits its applicability. Traditional CuAgSe-based materials are typically prepared using solid-state synthesis, melt growth, or ball milling methods. These processes not only suffer from high energy consumption but also require surfactant modification (which necessitates subsequent high-temperature treatment for removal). Furthermore, the material itself possesses… zTThe low value severely restricts its practical application.

[0004] In summary, developing a CuAgSe thermoelectric material preparation technology that combines low cost, low energy consumption, and no surfactant residue, while simultaneously optimizing the electronic transport properties of CuAgSe-based materials and effectively suppressing the lattice thermal conductivity, thereby comprehensively improving the cooling and power generation performance of devices, has become a key technical problem that urgently needs to be solved in the field of thermoelectric materials. Summary of the Invention

[0005] To address the problems in the background art, the present invention aims to provide a method for preparing high-performance Te-doped CuAgSe thermoelectric materials and their applications. This method is green and low-consumption, requires no surfactant, and the prepared Te-doped CuAgSe composite material exhibits excellent thermoelectric properties.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a high-performance Te-doped CuAgSe thermoelectric material, comprising the following steps: S1. Mix selenium powder and tellurium powder in a set ratio, add sodium borohydride solution, and stir until completely dissolved to obtain a selenium-tellurium mixed precursor solution. S2. Mix copper nitrate trihydrate and silver nitrate in a predetermined ratio, add solvent to dissolve, and obtain a copper-silver mixed precursor solution. S3. Under stirring conditions, the copper-silver mixed precursor solution obtained in step (2) is rapidly injected into the selenium-tellurium mixed precursor solution obtained in step (1) according to the stoichiometric ratio, and the reaction is carried out at room temperature to form a suspension. S4. Centrifuge the suspension obtained in step (3), wash and dry it to obtain Te-doped CuAgSe nanocomposite powder (CuAgSe). 1-x Te x ).

[0007] In the preferred embodiment, in step S1, the molar ratio of selenium powder to tellurium powder is (1-x):x, where 0.025≤x≤0.10.

[0008] In a preferred embodiment, in step S1, the concentration of sodium borohydride is 0.6~1.0 mol / L, and the total molar ratio of sodium borohydride to selenium telluride is 4:1~6:1.

[0009] In the preferred embodiment, in step S2, the molar ratio of copper nitrate trihydrate (Cu(NO3)2·3H2O) to silver nitrate (AgNO3) is 1:1, and the concentration of the copper-silver mixed precursor solution is 0.04~0.06 mol / L.

[0010] In the preferred embodiment, the stirring rate in step S3 is 300~500 r / min.

[0011] In the preferred embodiment, in step S3, the injection rate is 5~10 mL / min, and the reaction is carried out at room temperature for 5~30 min.

[0012] In the preferred embodiment, in step S4, the precipitate is washed with deionized water and ethanol 3 to 5 times in sequence.

[0013] This invention also provides a high-performance Te-doped CuAgSe thermoelectric material with the chemical formula CuAgSe. 1-x Te x , where 0.025≤x≤0.10.

[0014] The present invention also provides the application of the high-performance Te-doped CuAgSe thermoelectric material in near-room temperature thermoelectric cooling or waste heat power generation, wherein the near-room temperature is 298~443 K.

[0015] The present invention also provides a thermoelectric device based on Te-doped CuAgSe, comprising 5 to 10 pairs of PN thermoelectric legs, wherein each PN thermoelectric leg pair consists of an N-type thermoelectric leg and a P-type thermoelectric leg; the N-type thermoelectric leg is the CuAgSe. 1-x Te x (0.025≤x≤0.10) The P-type thermoelectric leg is made of Bi2Te3-based composite material and is obtained by hot pressing, cutting and surface treatment. The N-type thermoelectric leg has Ni diffusion barrier layers at both ends and Cu electrodes on the outside of the Ni diffusion barrier layers. The P-type thermoelectric leg and the N-type thermoelectric leg are welded to the Cu substrate by soldering material.

[0016] The preparation method of this invention has significant advantages: First, it achieves room temperature operation, eliminating the need for complex conditions such as high temperatures, thus greatly reducing energy consumption and aligning with the concept of green preparation; second, it employs a surfactant-free aqueous phase synthesis process, avoiding surfactant residue problems from the source, eliminating the need for subsequent high-temperature removal steps, simplifying the preparation process while reducing costs, and solving key process defects in the preparation of traditional CuAgSe-based materials. The Te-doped CuAgSe composite material prepared by this method can effectively overcome the performance bottlenecks of traditional materials: achieving extremely low lattice thermal conductivity. k L It precisely solves the core problem of suppressing lattice thermal conductivity, while also possessing excellent thermoelectric properties, significantly improving the dimensionless figure of merit of the material. zT .

[0017] At the same time, the present invention also provides a thermoelectric device based on the high-performance Te-doped CuAgSe thermoelectric material. With the help of the material’s excellent properties, it can achieve efficient near-room temperature cooling and power generation. It can not only meet the cooling needs of electronic devices, but also adapt to energy conversion scenarios such as waste heat recovery and small-scale power generation. It fills the technical gap between high-performance materials and practical devices in the field of near-room temperature thermoelectricity, and promotes the practical application of thermoelectric materials.

[0018] Compared with the prior art, the present invention has at least the following advantages: (1) Innovative synthesis method: For the first time, a surfactant-free aqueous phase synthesis method was used to prepare Te-doped CuAgSe nanocomposite materials. The method operates at room temperature and does not require high-temperature annealing or ligand removal steps, reducing the synthesis cost by more than 30%. The product has high purity (no organic residue) and is suitable for large-scale production.

[0019] (2) Breakthrough in material performance: Through Te doping-induced lattice distortion and defect engineering, a lattice thermal conductivity of 0.11 W·m-1·K-1 was achieved, with a peak zT=0.68 and an average zT=0.5. The performance indicators are significantly better than those of existing technologies.

[0020] (3) Application value of the device: The thermoelectric device constructed has both high-efficiency cooling and power generation performance. The cooling temperature difference, power density and conversion efficiency are all better than existing near-room temperature thermoelectric devices. It can be directly applied to scenarios such as heat dissipation of electronic devices and portable power generation, and has a broad market prospect. Attached Figure Description

[0021] Figure 1 CuAgSe 1-x Te x XRD patterns of nanocomposites (x=0, 0.025, 0.04, 0.05, 0.10); Figure 2 TEM images, HAADF-STEM images, and elemental mapping diagrams of CuAgSe0.95Te0.05 nanoparticles; Figure 3 : A schematic diagram of the structure of the thermoelectric device of the present invention; Figure 4 a) The relationship between the cooling temperature difference (ΔT) and the current (I) of the thermoelectric device of the present invention at different hot end temperatures; b) A comparison of the power density of the thermoelectric device of the present invention with that of the reported intermediate-temperature thermoelectric device as a function of temperature difference (ΔT). Detailed Implementation

[0022] The specific embodiments of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0023] The reagents used in the examples include: Silver nitrate (AgNO3, purity ≥99.8%), copper nitrate trihydrate (Cu(NO3)2·3H2O, purity >99.0%), selenium powder (100 mesh, purity >99.9%), sodium borohydride (NaBH4, purity ≥98%), and tellurium powder (100 mesh, purity ≥99.99%) were all purchased from Aladdin Reagent.

[0024] Structural and chemical characterization: Crystal structure analysis was performed using X-ray diffraction (Cu Kα rays, λ=1.54 Å, Nano-InXider, France); time-resolved XRD was performed at a scan rate of 5 °C·min⁻¹ with a step size of 0.02°. Nanostructure characterization was performed using transmission electron microscopy (Thermo Fisher Scientific Talos F200X, USA, operating voltage 200 kV), including high-resolution TEM (HRTEM), scanning TEM (STEM), and EDX analysis.

[0025] Thermoelectric performance testing: Seebeck coefficient and electrical conductivity were measured using the static DC method and the standard four-probe method (Linseis LSR-3, Germany), respectively. Both parameters were measured simultaneously from room temperature to 443 K, with a heating rate of 10 K·min⁻¹ and an estimation error of 4%. Thermal conductivity was calculated using κ=λCpρ, where λ is the thermal diffusivity, Cp is the specific heat capacity, and ρ is the sample density.

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings: Comparative Example 1: Preparation of CuAgSe nanocomposites (1) Preparation of selenium-tellurium mixed precursor solution: Selenium powder was added to 0.8 mol / L NaBH4 aqueous solution and stirred for 30 min until completely dissolved to obtain a precursor solution with a selenium concentration of 0.16 mol / L; (2) Preparation of copper-silver mixed precursor solution: Weigh 0.121 g (Cu(NO3)2·3H2O) (0.5 mmol) and 0.0849 g AgNO3 (0.5 mmol), add 10 mL of deionized water to dissolve, and obtain a copper-silver precursor solution with a concentration of 0.05 mol / L; (3) Room temperature reaction: Under stirring at 400 r / min, the copper-silver precursor solution was injected into the selenium precursor solution at a rate of 8 mL / min, and the reaction was carried out at room temperature for 15 min to form a black suspension. (4) Purification and drying: The suspension was centrifuged at 8000 r / min for 10 min, and the precipitate was washed three times each with deionized water and ethanol. It was then vacuum dried at 60℃ for 12 h to obtain CuAgSe nanopowder.

[0027] Example 1: CuAgSe 1-x Te x Preparation of nanocomposite materials (1) Preparation of selenium-tellurium mixed precursor solution: Selenium powder and tellurium powder were mixed in a molar ratio of (1-x):x (x=0.025, 0.04, 0.05, 0.10), and 20 mL of 0.8 mol / L NaBH4 aqueous solution was added. The mixture was stirred for 30 min until completely dissolved to obtain a precursor solution with a total selenium-tellurium concentration of 0.16 mol / L. (2) Preparation of copper-silver mixed precursor solution: Weigh 0.121 g Cu(NO3)2·3H2O (0.5 mmol) and 0.0849 g AgNO3 (0.5 mmol), add 10 mL of deionized water to dissolve, and obtain a copper-silver precursor solution with a concentration of 0.05 mol / L; (3) Room temperature reaction: Under stirring at 400 r / min, the copper-silver precursor solution was injected into the selenium-tellurium precursor solution at a rate of 8 mL / min, and the reaction was carried out at room temperature for 15 min to form a black suspension. (4) Purification and drying: The suspension was centrifuged at 8000 r / min for 10 min, and the precipitate was washed three times each with deionized water and ethanol, and then dried under vacuum at 60℃ for 12 h to obtain CuAgSe. 1-x Te x The thermoelectric properties of the nanopowder at 443 K are shown in Table 1. Table 1. Performance Comparison of Materials with Different Te Doping Ratios

[0028] Figure 1 CuAgSe 1-x Te x XRD patterns of nanocomposites, by Figure 1 It can be seen that all CuAgSe 1-x Te x The XRD spectra of the samples were highly matched with those of the orthorhombic phase CuAgSe (JCPDS No. 00-25-1180 and JCPDS No. 00-10-0451). With increasing Te2- doping concentration, CuAgSe... 1-x Te x The diffraction peaks shifted to lower angles (centered at 2θ≈42.4º), indicating that the lattice constant increases linearly with increasing Te content. This is attributed to Te2- occupying Se2- sites (Te2- ions have a larger radius).

[0029] Figure 2TEM images, HAADF-STEM images, and elemental mapping diagrams of CuAgSe0.95Te0.05 nanoparticles are provided. Figure 2 It can be seen that the lattice spacing of the (111) crystal plane is 0.271 nm. The corresponding fast Fourier transform (FFT) spectrum shows the diffraction spots of the (111) and (003) crystal plane families. STEM-EDX element mappings show that Cu, Ag, Se and Te are uniformly distributed in CuAgSe0.95Te0.05, confirming that Te was successfully doped and no impurity nanodomains were formed.

[0030] Example 2: Fabrication of thermoelectric devices Structural Design: The n-type legs are made of CuAgSe0.95Te0.05 (hot-pressed, 2 mm × 2 mm × 1.5 mm), with a 20 μm Ni diffusion barrier layer and Cu electrodes; the p-type legs are made of commercially available Bi2Te3 (1.5 mm × 1.5 mm × 1.5 mm); they are soldered to the Cu substrate using a 96.5%Sn-3.0%Ag-0.5%Cu alloy solder joint, forming 5 pairs of pn-type leg modules, such as... Figure 3 As shown.

[0031] Performance specifications: Maximum cooling temperature difference of 24.5 K (300 K at hot end) and 27.3 K (325 K at hot end); at a temperature gradient of 136 K, the output power density is 0.34 W·cm⁻², and the energy conversion efficiency is 3.6%, which is superior to existing Bi₂Te₃-based (0.23 W·cm⁻²) and Ag₂Se-based (0.10 W·cm⁻²) devices. Figure 4 As shown.

[0032] The above are merely preferred embodiments of the present invention, and only describe the implementation of the present invention. They are not intended to limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a high-performance Te-doped CuAgSe thermoelectric material, characterized in that, Includes the following steps: S1. Mix selenium powder and tellurium powder in a set ratio, add sodium borohydride solution, and stir until completely dissolved to obtain a selenium-tellurium mixed precursor solution. S2. Mix copper nitrate trihydrate and silver nitrate in a predetermined ratio, add solvent to dissolve, and obtain a copper-silver mixed precursor solution. S3. Under stirring conditions, the copper-silver mixed precursor solution obtained in step (2) is rapidly injected into the selenium-tellurium mixed precursor solution obtained in step (1) according to the stoichiometric ratio, and the reaction is carried out at room temperature to form a suspension. S4. Centrifuge the suspension obtained in step (3), wash and dry it to obtain Te-doped CuAgSe nanocomposite powder CuAgSe. 1-x Te x .

2. The method for preparing a high-performance Te-doped CuAgSe thermoelectric material according to claim 1, characterized in that, In step S1, the molar ratio of selenium powder to tellurium powder is (1-x):x, 0.025≤x≤0.

10.

3. The method for preparing a high-performance Te-doped CuAgSe thermoelectric material according to claim 1, characterized in that, In step S1, the concentration of sodium borohydride is 0.6~1.0 mol / L, and the total molar ratio of sodium borohydride to selenium telluride is 4:1~6:

1.

4. The method for preparing a high-performance Te-doped CuAgSe thermoelectric material according to claim 1, characterized in that, In step S2, the molar ratio of copper nitrate trihydrate to silver nitrate is 1:1, and the concentration of the copper-silver mixed precursor solution is 0.04~0.06 mol / L.

5. The method for preparing a high-performance Te-doped CuAgSe thermoelectric material according to claim 1, characterized in that, In step S3, the stirring rate is 300~500 r / min.

6. The method for preparing a high-performance Te-doped CuAgSe thermoelectric material according to claim 1, characterized in that, In step S3, the injection rate is 5~10 mL / min, and the reaction is carried out at room temperature for 5~30 min.

7. The method for preparing a high-performance Te-doped CuAgSe thermoelectric material according to claim 1, characterized in that, In step S4, the precipitate is washed 3 to 5 times with deionized water and ethanol in sequence.

8. A high-performance Te-doped CuAgSe thermoelectric material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7, and has the chemical formula CuAgSe. 1-x Te x , where 0.025≤x≤0.

10.

9. The application of the high-performance Te-doped CuAgSe thermoelectric material according to claim 8, characterized in that, It can be applied to near-room temperature thermoelectric cooling or waste heat power generation.

10. The application according to claim 9, characterized in that, The near-room temperature is 298~443 K.

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