Zn / Ge co-doped n-type PbS-based thermoelectric material and preparation method thereof

Abstract

The application belongs to the technical field of energy materials, and relates to a thermoelectric material, and particularly provides a Zn / Ge co-doped n-type PbS-based thermoelectric material and a preparation method thereof, so as to solve the problem that the PbS-based material is limited in thermoelectric performance in the near room temperature region due to high lattice thermal conductivity and low carrier concentration. The application is aimed at the base material PbS 0.5 Se 0.35 Te 0.15 A Zn and Ge double metal co-doping strategy is proposed to form a Zn / Ge co-doped n-type PbS-based thermoelectric material: PbS 0.5 Se 0.35 Te 0.15 +x%Zn+y%Ge, wherein 0 The thermoelectric material has excellent near room temperature thermoelectric performance, the room temperature thermoelectric figure of merit can reach 0.54, the average thermoelectric figure of merit in the near room temperature region (300-573 K) can reach 0.80, has a significant low cost advantage, raw material reserves are abundant, cost is low, the preparation process is simple, the preparation period is short, and the repeatability is good, and is conducive to large-scale production. In conclusion, the application is conducive to promoting the wide application of thermoelectric refrigeration technology, especially in the field of thermoelectric semiconductor refrigeration.

Description

Technical Field

[0001] This invention belongs to the field of energy materials technology, and relates to thermoelectric materials. Specifically, it provides a Zn / Ge co-doped n-type PbS-based thermoelectric material and its preparation method. Background Technology

[0002] Thermoelectric technology enables the reversible conversion of heat energy into electrical energy, showing broad application prospects in waste heat recovery and solid-state refrigeration. On the one hand, thermoelectric power generation can utilize the Seebeck effect to convert low-grade heat energy, such as industrial waste heat, into electrical energy, contributing to energy conservation and carbon reduction. On the other hand, thermoelectric refrigeration based on the Peltier effect has advantages such as noiseless operation and high-precision temperature control, making it suitable for emerging fields such as artificial intelligence, big data, cloud computing, and high-precision sensors, meeting the needs for efficient and stable localized cooling. Therefore, developing low-cost, high-performance thermoelectric materials is crucial.

[0003] Currently, most high-performance thermoelectric materials contain tellurium (Te), such as lead telluride (PbTe) and bismuth telluride (Bi₂Te₃). However, the scarcity and high cost of Te severely limit the large-scale application of such materials. In contrast, the abundance of sulfur (S) in the Earth's crust (~420 ppm) is 420,000 times higher than that of Te (~0.001 ppm), giving sulfur-based materials a significant advantage in terms of abundant resources and low cost. Lead sulfide (PbS), as a homologue of PbTe, possesses the same highly symmetric crystal structure, moderate carrier mobility and conductivity. Furthermore, PbS's high melting point and strong Pb-S chemical bonds endow it with higher chemical stability and stronger mechanical properties. However, the high intrinsic thermal conductivity and low carrier concentration of PbS materials result in poor thermoelectric performance, restricting the practical application of PbS-based materials in the thermoelectric field, especially in near-room temperature thermoelectric refrigeration. Therefore, developing near-room temperature, high-performance PbS-based thermoelectric materials is the focus of this invention. Summary of the Invention

[0004] The purpose of this invention is to provide a Zn / Ge co-doped n-type PbS-based thermoelectric material and its preparation method, in order to solve the problem that the thermoelectric performance of PbS-based materials is limited in the near-room temperature region due to the high lattice thermal conductivity and low carrier concentration.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A Zn / Ge co-doped n-type PbS-based thermoelectric material, consisting of a PbS matrix material. 0.5 Se 0.35 Te 0.15 Formed through Zn and Ge bimetallic co-doping, specifically represented as: PbS 0.5 Se 0.35Te 0.15 +x%Zn+y%Ge, where 0<x≤0.1, 0.1≤y≤0.9.

[0007] Furthermore, the doping amount of Zn is: 0.02≤x≤0.1, and the doping amount of Ge is: 0.3≤y≤0.6.

[0008] Furthermore, the doping amount of Zn is x=0.06, and the doping amount of Ge is y=0.5.

[0009] Meanwhile, the present invention also provides a method for preparing the above-mentioned Zn / Ge co-doped n-type PbS-based thermoelectric material, comprising the following steps:

[0010] Step 1: Mix Pb, S, Se, Te raw materials with Zn, Ge raw materials according to PbS 0.5 Se 0.35 Te 0.15 Weigh the mixture according to the atomic stoichiometry ratio of +x%Zn+y%Ge to obtain the mixture.

[0011] Step 2: Place the mixture in a vacuum quartz tube, seal it with a flame and melt it. Cool it to room temperature in the furnace to obtain a molten ingot.

[0012] Step 3: Grind the molten ingot into powder, load it into a mold, and perform spark plasma sintering to obtain Zn / Ge co-doped n-type PbS-based thermoelectric material.

[0013] Furthermore, in step 1, the elemental purity of the Pb, S, Se, and Te raw materials is greater than 99.999%, and the purity of the Zn and Ge raw materials is greater than 99.99%.

[0014] Furthermore, in step 2, the vacuum level in the vacuum quartz tube is less than 10. -3 Pa.

[0015] Furthermore, in step 2, the specific process of the melting reaction is as follows: the temperature is raised to 1100±50 ℃ within 15h~30h, and the temperature is maintained at 1100±50 ℃ for at least 6h.

[0016] Furthermore, in step 3, the specific process of spark plasma sintering is as follows: maintain the pressure at 40 MPa to 50 MPa and the temperature at 500 ± 50 °C for at least 6 minutes.

[0017] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0018] This invention provides a Zn / Ge co-doped n-type PbS-based thermoelectric material, wherein the substrate material is PbS 0.5 Se 0.35 Te0.15 Based on this, it is formed through Zn and Ge bimetallic co-doping. This Zn and Ge bimetallic co-doping strategy enables fine control of carrier concentration, ultimately resulting in thermoelectric materials with excellent near-room temperature thermoelectric performance. The room temperature thermoelectric figure of merit (ZT) can reach 0.54, and the average thermoelectric figure of merit (ZT) in the near-room temperature range (300~573 K) is... ave The efficiency can reach 0.80, which is higher than all currently reported n-type PbS-based thermoelectric materials. At the same time, the present invention also has a significant low-cost advantage. Compared with most Te-based thermoelectric materials (such as Bi2Te3 alloy and PbTe-based materials), the Zn / Ge co-doped n-type PbS-based thermoelectric material in the present invention has abundant raw material reserves and low cost, which can significantly reduce the raw material cost of thermoelectric materials and has higher cost-effectiveness. In addition, the preparation process is simple, the preparation cycle is short, and the repeatability is good, which is conducive to large-scale production.

[0019] In summary, the Zn / Ge co-doped n-type PbS-based thermoelectric material provided by this invention possesses excellent near-room temperature thermoelectric performance and significant low-cost advantages, which is conducive to promoting the widespread application of thermoelectric refrigeration technology, especially in the field of thermoelectric semiconductor refrigeration. Attached Figure Description

[0020] Figure 1 A comparison chart of crustal abundance and market prices of elements S, Se, and Te.

[0021] Figure 2 A comparison chart of the mechanical properties of cubic phase compounds PbS, PbSe, and PbTe.

[0022] Figure 3 This is a schematic diagram of the high-temperature pit furnace used in the melting reaction of this invention.

[0023] Figure 4 This is a schematic diagram of the spark plasma sintering furnace used in the spark plasma sintering process of this invention.

[0024] Figure 5 The graph shows the conductivity test results of the Zn / Ge co-doped n-type PbS-based thermoelectric materials in Examples 5-8 of this invention.

[0025] Figure 6 The figures show the Seebeck coefficient test results of the Zn / Ge co-doped n-type PbS-based thermoelectric materials in Examples 5-8 of this invention.

[0026] Figure 7 The graph shows the test results of carrier concentration and carrier mobility of the Zn / Ge co-doped n-type PbS-based thermoelectric materials in Examples 5-8 of this invention.

[0027] Figure 8The graph shows the power factor test results of the Zn / Ge co-doped n-type PbS-based thermoelectric materials in Examples 5-8 of this invention.

[0028] Figure 9 The graphs show the test results of the total thermal conductivity and lattice thermal conductivity of the Zn / Ge co-doped n-type PbS-based thermoelectric materials in Examples 5-8 of this invention.

[0029] Figure 10 The graph shows the thermoelectric figure of merit test results of the Zn / Ge co-doped n-type PbS-based thermoelectric materials in Examples 5-8 of this invention.

[0030] Figure 11 This is a comparison chart of the electrical conductivity of PbS-based thermoelectric materials in Example 7 of the present invention and Comparative Examples 1-3.

[0031] Figure 12 This is a comparison chart of the Seebeck coefficients of PbS-based thermoelectric materials in Example 7 of the present invention and Comparative Examples 1-3.

[0032] Figure 13 This is a comparison chart of the power factors of PbS-based thermoelectric materials in Example 7 of the present invention and Comparative Examples 1-3.

[0033] Figure 14 This is a comparison chart of the total thermal conductivity of PbS-based thermoelectric materials in Example 7 of the present invention and Comparative Examples 1-3.

[0034] Figure 15 This is a comparison diagram of the lattice thermal conductivity of PbS-based thermoelectric materials in Example 7 of the present invention and Comparative Examples 1-3.

[0035] Figure 16 This is a comparison chart of the thermoelectric figure of merit of PbS-based thermoelectric materials in Example 7 of the present invention and Comparative Examples 1-3.

[0036] Figure 17 This is a comparison chart showing the relationship between room temperature thermoelectric figure of merit and carrier concentration for PbS-based thermoelectric materials in Example 7 and Comparative Examples 4-13 of the present invention.

[0037] Figure 18 This is a comparison of the thermoelectric figure of merit curves of PbS-based thermoelectric materials in Example 7 and Comparative Examples 4-13 of the present invention as a function of temperature.

[0038] Figure 19 This is a comparison chart of the room temperature thermoelectric figure of merit of PbS-based thermoelectric materials in Example 7 and Comparative Examples 4-13 of the present invention.

[0039] Figure 20 This is a comparison chart of the average thermoelectric figure of merit of PbS-based thermoelectric materials in Example 7 and Comparative Examples 4-13 of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] like Figure 1 The image shows a comparison of the crustal abundance and market prices of elements S, Se, and Te. Figure 2 The figure shows a comparison of the mechanical properties of cubic phase compounds PbS, PbSe, and PbTe. As can be seen from the figure, PbS-based materials have a significant cost advantage, and also exhibit stronger hardness and higher Young's modulus, demonstrating superior mechanical properties. Therefore, PbS-based materials have significant advantages in engineering applications. Based on this, considering the performance parameters of thermoelectric materials, excellent thermoelectric materials should possess high electrical transport performance and low thermal conductivity. High electrical transport performance can maintain high-speed carrier transport, while low thermal conductivity can maintain the temperature difference between the two ends of the material. Therefore, this invention proposes a Zn-Ge bimetallic co-doping strategy for PbS-based thermoelectric materials. Firstly, PbS with low lattice thermal conductivity is used... 0.5 Se 0.35 Te 0.15 As a matrix material, on the one hand, Zn has a lower interstitial formation energy in Pb-rich PbS, which allows it to smoothly enter the interstitial spaces of the PbS lattice and form interstitial Zn ions, thereby providing additional free electrons and optimizing the carrier concentration. On the other hand, Ge doping can further increase the carrier concentration and improve the electrical conductivity, while also bringing about larger mass fluctuations and lattice distortion to enhance phonon scattering, which is beneficial for reducing the lattice thermal conductivity.

[0042] Based on the above mechanism, this invention provides 12 embodiments, namely Embodiment 1 to Embodiment 12, each embodiment providing a Zn / Ge co-doped n-type PbS-based thermoelectric material, which is composed of PbS matrix material. 0.5 Se 0.35 Te 0.15 Formed through Zn and Ge bimetallic co-doping, specifically represented as: PbS 0.5 Se 0.35 Te 0.15 +x%Zn+y%Ge, where the doping amount of Zn x and the doping amount of Ge y are shown in Table 1.

[0043] Table 1: Doping amounts of Zn and Ge

[0044]

[0045] The Zn / Ge co-doped n-type PbS-based thermoelectric materials in Examples 1 to 12 were all prepared by the following steps:

[0046] Step 1: Combine Pb strips, S powder, Se granules, Te lumps (purity greater than 99.999%), Zn granules, and Ge lumps (purity greater than 99.99%) according to PbS 0.5 Se 0.35 Te 0.15 Weigh the mixture according to the atomic stoichiometry ratio of +x%Zn+y%Ge to obtain the mixture.

[0047] Step 2: Place the mixture obtained in Step 1 into a round-bottomed quartz tube with an inner diameter of 17 mm, and then evacuate the quartz tube to a vacuum level of less than 10. -3 Pa, the quartz tube is sealed with a flame and then placed in a high-temperature pit furnace for melting reaction, such as Figure 3 As shown, the temperature control program of the high-temperature pit furnace is as follows: heat up to 1100 ℃ in 20 h, hold for 6 h, and then cool down to room temperature with the furnace to obtain polycrystalline n-type PbS-based thermoelectric material molten ingot.

[0048] Step 3: The n-type PbS-based thermoelectric material ingot obtained in Step 2 is melted and cast, then ground into powder using an agate mortar and pestle. The powder is then placed into a graphite mold (15mm in diameter) lined with carbon paper. The graphite mold is then subjected to spark plasma sintering in a vacuum environment. Figure 4 As shown; the pressure and temperature of the discharge plasma sintering furnace were: temperature 550 ℃, pressure 50 MPa (883Kg); the sintering program was: heating to 550 ℃ for 12 min, and the pressure rising to 50 MPa synchronously with the temperature, and maintaining this temperature and pressure for 6 min; after the program was completed, the sample was cooled to room temperature with the furnace to obtain a dense cylindrical ingot with a diameter of 15 mm and a height of 10~11 mm, which is the Zn / Ge co-doped n-type PbS-based thermoelectric material.

[0049] After the carbon paper is removed from the cylindrical ingot obtained by spark plasma sintering, the sample is cut using a low-speed cutter and then polished with sandpaper into columnar and sheet-like samples required for electrical and thermal performance testing. The length and width of the columnar sample do not exceed 4 mm and the height is between 9 and 12 mm; the thickness of the sheet-like sample is between 1 and 2 mm, and it can be square or round, depending on the sample chamber. In this invention, sample chambers of 8 mm × 8 mm, 6 mm × 6 mm, or ϕ6 mm are selected for thermoelectric performance testing of the sample.

[0050] Taking Examples 5-8 as examples, the thermoelectric properties of the samples in Examples 5-8 were tested using a Seebeck and resistivity testing system and a laser thermal conductivity meter. Simultaneously, the Hall carrier concentration at room temperature was measured using a Hall effect testing system. The results are as follows: Figures 5-10 As shown, where, Figure 5 Let σ be the electrical conductivity. Figure 6 S is the Seebeck coefficient. Figure 7 Let n be the carrier concentration (n) and carrier mobility (μ). Figure 8 Power factor (PF) Figure 9 Total thermal conductivity (κ) tot ) and lattice thermal conductivity (κ) lat ), Figure 10 The figure shows a dimensionless thermoelectric figure of merit (ZT). As can be seen from the figure, Zn and Ge co-doping achieved fine control of the carrier concentration in the n-type PbS-based material, optimizing the carrier concentration. In Example 7, the Zn / Ge co-doped n-type PbS-based thermoelectric material (PbS...) 0.5 Se 0.35 Te 0.15 The room temperature ZT value of (+0.06%Zn+0.5%Ge) can reach 0.54.

[0051] Furthermore, using PbS as the matrix material... 0.5 Se 0.35 Te 0.15 Zn-doped sample: PbS 0.5 Se 0.35 Te 0.15 +0.06% Zn, Ge single-doped sample: PbS 0.5 Se 0.35 Te 0.15 +0.5%Ge served as comparative examples 1-3, and was compared with the Zn / Ge co-doped n-type PbS-based thermoelectric materials prepared in Example 7. The results are as follows: Figures 11-16 As shown, where, Figure 11 Let σ be the electrical conductivity. Figure 12 S is the Seebeck coefficient. Figure 13 Power factor (PF) Figure 14 Total thermal conductivity (κ) tot ), Figure 15 Lattice thermal conductivity (κ) lat ), Figure 16 The figure represents the dimensionless thermoelectric figure of merit (ZT). As can be seen from the figure, the thermoelectric performance of the Zn / Ge co-doped n-type PbS-based thermoelectric material provided by this invention is significantly higher than that of the single-doped sample.

[0052] Furthermore, taking the literature "Wang, Lei, et al. High Carrier Mobility in N‐TypePbS" as an example... 0.6 Se 0.4Crystal Enhances Thermoelectric Properties and Module Performance. Small 21.42 (2025): e08078.” is used as Comparative Example 4. To ensure the accuracy of the comparison results, the optimal polycrystalline composition in the literature is selected as the comparative example, labeled as PbS-Sn-Ga; the literature “Wang, Lei, et al. Realizing thermoelectric cooling and power generation in N-type PbS” is used as the comparative example. 0.6 Se 0.4Comparative Example 5 is “via latticeplainification and interstitial doping. Nature Communications 15.1 (2024):3782.”. To ensure the accuracy of the comparison results, the optimal polycrystalline composition in the literature was selected as the comparative example, labeled as PbS+Pb+Cu. Comparative Example 6 is “Liu, Zhengtao, et al. Lattice expansion enables interstitial doping to achieve a high average ZT in n‐type PbS. Interdisciplinary Materials 2.1 (2023): 161-170.”, labeled as PbS+Cu. Comparative Example 7 is “Cheng, Rui, et al. Bridging the miscibility gap towards higher thermoelectric performance of PbS. Acta Materialia 220 (2021): 117337.”, labeled as PbS-Ga. Comparative Example 7 is “Luo, Zhong-Zhen, et al. Enhancement of thermoelectric performance for n-type PbS through synergy of gap state and fermi Comparative Example 8 is “PbS-In-Ga”, denoted as “levelpinning. Journal of the American Chemical Society 141.15 (2019): 6403-6412”; Comparative Example 9 is “Hou, Zhenghao, et al. Boosting thermoelectric properties of n-type PbS across a broad temperature rangethrough doping with trace amounts of InBi. Applied Physics Letters 126.2(2025)”, denoted as “PbS-In-Bi”.Comparative Example 10 is “Enhancing thermoelectric performance of n-type PbS in a wide temperature range through band engineering and dynamic doping. Materials Today Physics (2025): 101907,” labeled as PbS-In-Sb+Cu; Comparative Example 11 is “Xiao, Yu, et al. Band sharpening and band alignment enable high quality factor to enhance thermoelectric performance in n-type PbS. Journal of the American Chemical Society 142.8(2020): 4051-4060,” labeled as PbS-Sn; Comparative Example 12 is “Hou, Zhenghao, et al. Boosting thermoelectric performance of n-type PbS through synergisticallyintegrating In resonant level and Cu dynamic doping. Journal of Physics and Chemistry of Solids 148 (2021): 109640,” labeled as PbS-In+Cu; Comparative Example 12 is “Jiang, Binbin, et al. Realizing high-efficiency power generation in low-cost PbS-based thermoelectric materials. Energy & Environmental Science 13.2(2020): 579-591. This is Comparative Example 13, labeled PbS-Sb; in all labels, "-" indicates Pb site substitution doping, and "+" indicates additional doping. All the above comparative examples represent the optimal polycrystalline composition reported in the literature.

[0053] Example 7 was compared with Comparative Examples 4-13, and the results are as follows: Figures 17-20 As shown; where, Figure 17This graph shows the relationship between thermoelectric figure of merit (ZT) and carrier concentration, where the pentagram represents the present invention. As can be seen from the graph, at room temperature (300K), the carrier concentration of n-type PbS-based materials with a high room temperature ZT value should be around 10. 19 cm -3 In the vicinity, the present invention enables fine control of carrier concentration through Zn and Ge bimetallic co-doping; Figure 18 The curve shows the thermoelectric figure of merit as a function of temperature, where the pentagram represents the present invention; Figure 19 A comparison chart of thermoelectric figure of merit at room temperature. Figure 20 The average thermoelectric figure of merit (ZT) ave The figure shows a comparison of the two materials, where PbS+Zn+Ge represents the present invention. As can be seen from the figure, the present invention benefits from the Zn / Ge bimetallic co-doping strategy. In Example 7, the Zn / Ge co-doped n-type PbS-based thermoelectric material (PbS+Zn+Ge) achieves a room temperature thermoelectric figure of merit of 0.54, and the average thermoelectric figure of merit (ZT) in the temperature range of 300~573 K is [missing value]. ave The figure of merit can reach 0.8. Within the same temperature range, both the room temperature thermoelectric figure of merit and the average thermoelectric figure of merit are the highest values ​​in the prior art.

[0054] In summary, this invention provides a Zn / Ge co-doped n-type PbS-based thermoelectric material with a cubic phase structure. This material can serve as a near-room-temperature, high-performance PbS-based thermoelectric material and possesses excellent mechanical properties. It can be widely used in thermoelectric refrigeration devices and is expected to achieve large-scale development and application.

[0055] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A Zn / Ge co-doped n-type PbS-based thermoelectric material, characterized in that, From the matrix material PbS 0.5 Se 0.35 Te 0.15 Formed through Zn and Ge bimetallic co-doping, specifically represented as: PbS 0.5 Se 0.35 Te 0.15 +x%Zn+y%Ge, where 0<x≤0.1, 0.1≤y≤0.

9.

2. The Zn / Ge co-doped n-type PbS-based thermoelectric material according to claim 1, characterized in that, The doping amount of Zn is: 0.02≤x≤0.1, and the doping amount of Ge is: 0.3≤y≤0.

6.

3. The Zn / Ge co-doped n-type PbS-based thermoelectric material according to claim 1, characterized in that, The doping amount of Zn is x=0.06, and the doping amount of Ge is y=0.

5.

4. The method for preparing the Zn / Ge co-doped n-type PbS-based thermoelectric material according to claim 1, characterized in that, Includes the following steps: Step 1: Mix Pb, S, Se, Te raw materials with Zn, Ge raw materials according to PbS 0.5 Se 0.35 Te 0.15 Weigh the mixture according to the atomic stoichiometry ratio of +x%Zn+y%Ge to obtain the mixture. Step 2: Place the mixture in a vacuum quartz tube, seal it with a flame and melt it. Cool it to room temperature in the furnace to obtain a molten ingot. Step 3: Grind the molten ingot into powder, load it into a mold, and perform spark plasma sintering to obtain Zn / Ge co-doped n-type PbS-based thermoelectric material.

5. The method for preparing the Zn / Ge co-doped n-type PbS-based thermoelectric material according to claim 4, characterized in that, In step 1, the elemental purity of the raw materials Pb, S, Se, and Te is greater than 99.999%, and the purity of the raw materials Zn and Ge is greater than 99.99%.

6. The method for preparing the Zn / Ge co-doped n-type PbS-based thermoelectric material according to claim 4, characterized in that, In step 2, the vacuum level in the vacuum quartz tube is less than 10. -3 Pa.

7. The method for preparing the Zn / Ge co-doped n-type PbS-based thermoelectric material according to claim 4, characterized in that, In step 2, the specific process of the melting reaction is as follows: the temperature is raised to 1100±50 ℃ within 15h~30h, and the temperature is maintained at 1100±50 ℃ for at least 6h.

8. The method for preparing the Zn / Ge co-doped n-type PbS-based thermoelectric material according to claim 4, characterized in that, In step 3, the specific process of spark plasma sintering is as follows: maintain the pressure at 40 MPa to 50 MPa and the temperature at 500 ± 50 °C for at least 6 minutes.

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