Near-room temperature n-type multimetal co-doped PbTe-based thermoelectric materials and their preparation methods

Abstract

This invention belongs to the field of energy materials technology, and provides a near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material and its preparation method, to solve the problem of limited near-room temperature thermoelectric performance of existing PbTe-based thermoelectric materials. This invention proposes a synergistic optimization strategy based on multi-metal co-doping of Ni, Sn, and Cu for intrinsic PbTe, resulting in a near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material: PbTe + x%Ni + y%Sn + z%Cu, 1≤x≤1.4, 0.3≤y≤0.7, 0.3≤z≤0.5. This strategy increases conductivity while maintaining a large Seebeck coefficient at room temperature. ZT Reaching 0.65, the average value in the near-room temperature range (300~473 K) ZT The power factor reaches 0.85; on the other hand, while maintaining a high power factor, the lattice thermal conductivity is significantly reduced, realizing the decoupled control of electroacoustic transport parameters, especially showing significantly enhanced thermoelectric performance in the medium and low temperature region; in addition, the present invention also has the advantages of simple preparation process, short cycle and wide sintering conditions.

Description

Technical Field

[0001] This invention belongs to the field of energy materials technology, specifically a near-room temperature n-type multimetal co-doped PbTe-based thermoelectric material and its preparation method. Background Technology

[0002] With the deepening of global industrialization, energy consumption has risen sharply, and energy shortages and environmental pollution have become increasingly prominent, thus driving the rapid development of sustainable energy conversion technologies. Thermoelectric technology is a green energy technology that utilizes the directional movement of charge carriers within thermoelectric materials to achieve direct and reversible conversion between thermal and electrical energy. It has shown broad prospects in waste heat recovery and electronic refrigeration. On the one hand, based on the Seebeck effect, low-grade thermal energy is converted into electrical energy, i.e., thermoelectric power generation, which contributes to the sustainable use of energy. On the other hand, thermoelectric refrigeration based on the Peltier effect can achieve precise heat transfer, with extremely high response speed and temperature control accuracy, which can meet the application needs of temperature-sensitive emerging fields such as artificial intelligence, big data, and computing platforms. Therefore, the development of high-performance thermoelectric materials is the research focus of this invention.

[0003] Bismuth telluride (Bi2Te3)-based materials are currently the most commercially mature thermoelectric materials, but due to their unique layered crystal structure, the layers are connected by relatively weak van der Waals forces, resulting in poor mechanical properties, such as... Figure 1 As shown; furthermore, the anisotropy of the layered structure increases the difficulty of preparing Bi2Te3, which is generally produced commercially using the zone melting method. This leads to Bi2Te3's tendency to cleave along the growth direction, resulting in relatively low processing yield and long-term service reliability. In contrast, PbTe has a highly symmetric cubic phase crystal structure, such as... Figure 2 As shown, its mechanical properties are significantly better than Bi2Te3, making it more suitable for large-scale production applications. However, while the performance of PbTe-based thermoelectric materials in the mid-temperature range has matured, the development of their thermoelectric properties near room temperature remains insufficient, greatly limiting their potential applications in thermoelectric refrigeration. Therefore, this invention presents a near-room-temperature high-performance n-type multi-metal co-doped PbTe-based thermoelectric material and its preparation method, aimed at improving the thermoelectric performance of PbTe-based thermoelectric materials in the near-room-temperature range. Summary of the Invention

[0004] The purpose of this invention is to provide a near-room-temperature n-type multi-metal co-doped PbTe-based thermoelectric material and its preparation method, in order to solve the problem of limited thermoelectric performance in the near-room-temperature region of existing PbTe-based thermoelectric materials. This invention simultaneously dops Ni, Sn, and Cu into a PbTe matrix material, and the prepared multi-metal co-doped n-type PbTe-based thermoelectric material achieves a high room-temperature ZT value and an average ZT value (ZT). ave With excellent performance of up to 0.65 and 0.85 at K (300~473 K), it has the advantage of high performance near room temperature.

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

[0006] A near-room-temperature n-type multi-metal co-doped PbTe-based thermoelectric material has the chemical formula: PbTe+x%Ni+y%Sn+z%Cu, where 1≤x≤1.4, 0.3≤y≤0.7, and 0.3≤z≤0.5. Ni, Sn, and Cu metal atoms are incorporated into intrinsic PbTe in the form of dopant to form the near-room-temperature n-type multi-metal co-doped PbTe-based thermoelectric material.

[0007] Furthermore, in the near-room temperature n-type multimetal co-doped PbTe-based thermoelectric material, the doping amount of Ni is x=1.2, the doping amount of Sn is y=0.5, and the doping amount of Cu is z=0.4.

[0008] Furthermore, the present invention also provides a method for preparing the near-room temperature n-type multimetal co-doped PbTe-based thermoelectric material, comprising the following steps:

[0009] Step 1: Weigh Pb, Te and Ni, Cu and Sn raw materials according to the atomic stoichiometric ratio of their chemical formulas to obtain a mixture.

[0010] Step 2: Place the mixture in a vacuum quartz tube, seal it with a flame and melt it, then cool it to room temperature with the furnace temperature to obtain a molten ingot;

[0011] Step 3: Grind the molten ingot into powder, load it into a mold and perform spark plasma (SPS) sintering to obtain near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material.

[0012] Furthermore, in step 1, the elemental purity of the Pb and Te raw materials is greater than 99.999%, and the purity of the Ni, Cu, and Sn raw materials is greater than 99.99%.

[0013] Furthermore, in step 2, the specific process of the melting reaction is as follows: the temperature is raised to 1050±50 ℃ within 20h~30h, and held at that temperature for more than 10h.

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

[0015] Furthermore, in step 3, the specific process of spark plasma (SPS) sintering is as follows: the temperature is raised to 500±50 ℃ within 5~15 min, and the pressure is raised to 40MPa~50 MPa simultaneously with the temperature, and maintained at this temperature and pressure for 5~15 min.

[0016] Based on the above technical solution, the beneficial effect of the present invention is to provide a near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material and its preparation method, which has the following advantages:

[0017] 1) It possesses excellent thermoelectric properties. Through a multi-metal co-doping synergistic optimization strategy, it increases conductivity while maintaining a large Seebeck coefficient, with a room temperature power factor (PF) of 43.44 μW / cm². -1 •K -2 The ZT at room temperature is 0.65, and the average ZT in the near-room temperature range (300~473K) is 0.85, making it one of the best performing materials in the current n-type PbTe-based material system.

[0018] 2) It has the advantage of synergistic optimization of electrothermal transport. Multi-metal co-doping significantly reduces the lattice thermal conductivity while maintaining a high power factor, realizing the decoupled control of electroacoustic transport parameters, and showing significantly enhanced thermoelectric performance, especially in the medium and low temperature region.

[0019] 3) It has manufacturing cost advantages, good process adaptability and repeatability. The preparation method is simple, has a short cycle, and has a wide range of sintering conditions, which is conducive to achieving material consistency and large-scale preparation.

[0020] In summary, this invention provides a near-room temperature high-performance n-type multi-metal co-doped PbTe-based thermoelectric material with excellent thermoelectric properties and a simple preparation process, which is of great value for promoting the practical application of near-room temperature thermoelectric conversion technology. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the crystal structure of existing Bi2Te3 materials.

[0022] Figure 2 This is a schematic diagram of the crystal structure of existing PbTe-based thermoelectric materials.

[0023] Figure 3 This is a schematic diagram of the high-temperature pit furnace used in this invention.

[0024] Figure 4 This is a schematic diagram of the spark plasma sintering furnace used in this invention.

[0025] Figure 5 The graph shows the thermoelectric performance test results of the near-room temperature n-type multimetal co-doped PbTe-based thermoelectric material in Example 6 of this invention; wherein, Figure 5 In the figure (a), the conductivity σ is... Figure 5 In the middle (b), S is the Seebeck coefficient. Figure 5 In the middle (c), the carrier concentration and carrier mobility are represented. Figure 5 In the middle (d), the power factor PF is represented. Figure 5 In the middle (e), κ represents the total thermal conductivity. tot With lattice thermal conductivity κ lat , Figure 5 In the middle (f), the dimensionless thermoelectric figure of merit ZT value is given.

[0026] Figure 6 This is a comparison of the thermoelectric figure of merit of the near-room temperature n-type multimetal co-doped PbTe-based thermoelectric material in Example 6 of the present invention with other metal-doped samples in the near-room temperature region.

[0027] Figure 7 This is a comparison chart of the room temperature thermoelectric figure of merit of the near-room temperature n-type multimetal co-doped PbTe-based thermoelectric material in Example 6 of the present invention with the average thermoelectric figure of merit in the near-room temperature region (300~473 K) compared with other metal-doped samples. Detailed Implementation

[0028] 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.

[0029] This invention provides a near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material. Using PbTe as the matrix, the intrinsic PbTe is transformed from a weakly p-type material to an n-type material through co-doping with Ni, Cu, and Sn metal atoms. At the same time, through the strict design of the doping amounts of Ni, Cu, and Sn metal atoms, an electroacoustic synergistic optimization effect is generated, which improves the power factor (PF) of the PbTe-based thermoelectric material while reducing the lattice thermal conductivity, ultimately giving it excellent thermoelectric performance in the near-room temperature region.

[0030] More specifically, based on the expression for the dimensionless thermoelectric figure of merit ZT, an ideal thermoelectric material should possess both high electrical transport performance to ensure efficient electron transport and low thermal conductivity to maintain macroscopic temperature differences. Building upon this, given the high concentration of cation vacancies within intrinsic PbTe, which results in p-type conductivity at room temperature, this invention creatively proposes a multi-metal co-doping synergistic optimization strategy based on Ni, Cu, and Sn to achieve n-type transport characteristics in PbTe. Sn preferentially fills Pb vacancies, compensating for intrinsic acceptor defects to transform the material into n-type and significantly improve carrier mobility. Simultaneously, the temperature-dependent solubility of transition metal Ni and the efficient donor effect of Cu are utilized to optimize carrier concentration across the entire temperature range. Furthermore, the multi-metal co-doped atoms introduce high-density point defects, enhancing phonon scattering through induced fluctuations in the mass and stress fields, thereby effectively reducing lattice thermal conductivity while maintaining excellent electrical performance. Ultimately, this results in the proposed n-type multi-metal co-doped PbTe-based thermoelectric material exhibiting excellent thermoelectric performance in the near-room temperature range.

[0031] In summary, the chemical formula of the near-room temperature n-type multimetal co-doped PbTe-based thermoelectric material is: PbTe+x%Ni+y%Sn+z%Cu, that is, the atomic stoichiometric ratio is Pb:Te:Ni:Sn:Cu=1:1:x%:y%:z%, 1≤x≤1.4, 0.3≤y≤0.7, 0.3≤z≤0.5.

[0032] Based on the above technical solution, the present invention provides 7 embodiments, namely Embodiment 1 to Embodiment 7, wherein the doping amount of Ni x, Sn y, and Cu z are shown in Table 1.

[0033] Table 1. Atomic doping of Ni, Cu, and Sn metals

[0034]

[0035] The near-room temperature n-type multimetal co-doped PbTe-based thermoelectric materials in Examples 1 to 7 were prepared by the following steps:

[0036] Step 1: Pb strips and Te blocks with a purity greater than 99.999%, and Ni blocks, Cu particles, and Sn particles with a purity greater than 99.99% are mixed according to the atomic stoichiometric ratio of PbTe+x%Ni+y%Sn+z%Cu (Pb:Te:Ni:Sn:Cu=1:1:x%:y%:z%) to obtain a mixture.

[0037] Step 2: Place the mixture obtained in Step 1 into a round-bottomed quartz tube with an inner diameter of 17 mm, and then subject the quartz tube to vacuum treatment with a vacuum degree of less than 10. -3Pa, the quartz tube was sealed with a flame gun and then placed in a high-temperature pit furnace for melting reaction, such as Figure 3 As shown;

[0038] The temperature control program of the high-temperature pit furnace is as follows: heat up to 1050 ℃ in 24 h, hold for 10 h, and cool down to room temperature with the furnace to obtain polycrystalline n-type PbTe-based thermoelectric material molten ingot;

[0039] Step 3: The n-type PbTe-based thermoelectric material ingot obtained in Step 2 is fused and ground into powder using an agate mortar and pestle. The powder is then placed into a graphite mold (15 mm in diameter) lined with carbon paper. The graphite mold is then subjected to spark plasma sintering in a vacuum environment. Figure 4 As shown;

[0040] The sintering process of the spark plasma sintering furnace is as follows: temperature is 500 ℃ and pressure is 50 MPa (883 Kg); specifically, the temperature is raised to 500 ℃ in 10 min, and the pressure is raised to 50 MPa synchronously with the temperature. This temperature and pressure are maintained for 10 min, and the furnace is cooled to room temperature to obtain a dense disc-shaped ingot with a diameter of 15 mm and a height of 8~10 mm, which yields the multi-metal co-doped n-type PbTe-based thermoelectric material.

[0041] The following describes the beneficial effects of the present invention in detail using Example 6 as an example, combined with testing. Other embodiments have similar excellent thermoelectric performance.

[0042] After the carbon paper is removed from the disc-shaped ingot, the sample is cut using a low-speed cutter. Then, it is sanded into columnar and sheet-shaped samples required for testing electrical and thermal properties. The length and width of the columnar sample do not exceed 5 mm, and the height is between 9 and 12 mm. The thickness of the sheet-shaped sample is between 1 and 2 mm, and it can be square or round, depending on the size of the sample support. In this embodiment, sample supports of 8 mm × 8 mm, 6 mm × 6 mm, or 6 mm in diameter are selected.

[0043] Thermoelectric properties of Example 6 were tested using a Seebeck and resistivity testing system and a laser thermal conductivity meter, including: conductivity σ, Seebeck coefficient S, thermal diffusivity D, and the total thermal conductivity and lattice thermal conductivity were calculated. The test temperature range for thermoelectric properties was from room temperature to 500 °C (773 K), and the results are as follows. Figure 5 As shown, Figure 5 In the figure (a), the conductivity σ is... Figure 5 In the middle (b), S is the Seebeck coefficient. Figure 5 In the middle (c), the carrier concentration and carrier mobility are represented. Figure 5 In the middle (d), the power factor PF is represented. Figure 5 In the middle (e), κ represents the total thermal conductivity. tot With lattice thermal conductivity κ lat, Figure 5 In the figure of merit (f), ZT is the dimensionless thermoelectric figure of merit. It should be noted that, to more intuitively demonstrate the beneficial effects of the multi-metal (Ni, Cu, and Sn) co-doping synergistic optimization strategy in this invention, such as... Figure 5 The test results shown include single-doped and double-doped samples for comparison. The single-doped samples are labeled as Sn, Ni or Cu, and the double-doped samples are labeled as NiCu, CuSn or NiSn.

[0044] Depend on Figure 5 As can be seen, compared with single-metal doping and bimetallic doping, the n-type multi-metal co-doped PbTe-based thermoelectric material in Example 6 exhibits superior thermoelectric performance in the near-room temperature range; the Cu-doped sample increased the carrier concentration to 10. 19 On a magnitude scale, Sn-doped samples (such as Sn, CuSn, and NiCuSn) significantly improved carrier mobility, while the addition of Ni reduced the carrier concentration from an excessively high level to a moderate 5 × 10⁻⁶. 18 By reducing carrier concentration, carrier mobility was increased; the synergistic regulation of the three metal elements significantly improved the power factor in the near-room temperature range; furthermore, the multi-metal co-doping optimization strategy introduced gap point defects and lattice distortion, resulting in a decrease in lattice thermal conductivity. Therefore, this invention, based on the synergistic regulation of multi-metal co-doping, achieves synergistic optimization of electroacoustic transport characteristics, thereby improving thermoelectric performance.

[0045] Furthermore, the thermoelectric figure of merit of the near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material in Example 6 of the present invention was compared with that of other metal-doped / double-doped PbTe-based materials, and the results are as follows: Figure 6as shown; among which, "PbTe+In" refers to the literature "Deep defect level engineering: a strategy of optimizing the carrier concentration for high thermoelectric performance"; "PbTe+Cu" refers to the literature "Realization of higher thermoelectric performance by dynamic doping of copper in n-type PbTe"; "PbTe+Ag" refers to the literature "Fine tuning of defects enables high carrier mobility and enhanced thermoelectric performance of n-type PbTe"; "PbTe-Ga-Zn" refers to the literature "Extraordinary role of Zn in enhancing thermoelectric performance of Ga-doped n-type PbTe"; "PbTe-Cr" refers to the literature "High-performance in n-type PbTe-based thermoelectric materials achieved by synergistically dynamic doping and energy filtering"; "PbTe-Ga-In" refers to the literature "Multicomponent Synergistic Doping Enables High‐efficiency n‐Type PbTe Thermoelectric Devices"; "PbTe-Ga" refers to the literature "Weak electron phonon coupling and deep level impurity for high thermoelectric performance Pb 1−x Ga x"Te"; "PbTe-Gd" can be found in the literature "Discordant Gd and electronic band flattening synergistically induce high thermoelectric performance in n-type PbTe"; it should also be noted that in the legend, "-" indicates substitution doping at the Pb site, and "+" indicates additional doping; Figure 6 As can be seen, the near-room temperature multi-metal co-doped n-type PbTe-based thermoelectric material proposed in this invention exhibits significantly superior thermoelectric performance compared to existing single and partially dual-doped systems; combined with Figure 6 As can be seen from the ZT value versus temperature curve, the performance of this invention in the near-room temperature region significantly surpasses that of other doped systems such as PbTe+Cu, PbTe-Cr, and PbTe-Ga.

[0046] Furthermore, the room-temperature thermoelectric figure of merit of the near-room-temperature n-type multi-metal co-doped PbTe-based thermoelectric material (PbTe+1.2%Ni+0.5%Sn+0.4%Cu) in Example 6 of this invention was compared with the average thermoelectric figure of merit in the near-room-temperature region of other metal-doped / double-doped PbTe-based materials. The results are as follows: Figure 7 As shown; by Figure 7 As can be seen, thanks to the synergistic optimization strategy of Ni, Sn, and Cu multi-metal co-doping, the near-room temperature multi-metal co-doped n-type PbTe-based thermoelectric material proposed in this invention can achieve a ZT value of 0.65 at room temperature and a ZT value of [missing value] in the temperature range of 300~473 K. ave The ZT value is as high as 0.85, which is the highest reported value for n-type metal-doped thermoelectric materials within the same temperature range. ave The material with the highest value.

[0047] In summary, this invention proposes a near-room temperature multi-metal co-doped n-type PbTe-based thermoelectric material that exhibits superior thermoelectric performance in the near-room temperature range. Furthermore, its fabrication process is simple and easy to mass-produce, making it widely applicable to thermoelectric refrigeration devices and demonstrating broad application prospects.

[0048] 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 near-room-temperature n-type multi-metal co-doped PbTe-based thermoelectric material, characterized in that, The chemical formula is: PbTe+x%Ni+y%Sn+z%Cu, where 1≤x≤1.4, 0.3≤y≤0.7, and 0.3≤z≤0.5; Ni, Sn, and Cu metal atoms are incorporated into intrinsic PbTe in a doping manner, with an atomic stoichiometric ratio of Pb:Te:Ni:Sn:Cu=1:1:x%:y%:z%, forming the near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material.

2. The near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material according to claim 1, characterized in that, The doping amount of Ni metal atoms is: x=1.2, the doping amount of Sn metal atoms is: y=0.5, and the doping amount of Cu metal atoms is: z=0.

4.

3. The preparation method of the near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material according to claim 1, characterized in that, Includes the following steps: Step 1: Weigh Pb, Te and Ni, Cu and Sn raw materials according to the atomic stoichiometric ratio of their chemical formulas to obtain a mixture. Step 2: Place the mixture in a vacuum quartz tube, seal it with a flame and melt it, then cool it to room temperature with the furnace temperature 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 near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material.

4. The preparation method of the near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material according to claim 3, characterized in that, In step 1, the elemental purity of Pb and Te raw materials is greater than 99.999%, and the purity of Ni, Cu and Sn raw materials is greater than 99.99%.

5. The method for preparing the near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material according to claim 3, characterized in that, In step 2, the specific process of the melting reaction is as follows: the temperature is raised to 1050±50 ℃ within 20h~30h, and held at that temperature for more than 10h.

6. The method for preparing the near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material according to claim 3, 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 near-room temperature n-type multi-metal co-doped PbTe-based thermoelectric material according to claim 3, characterized in that, In step 3, the specific process of spark plasma sintering is as follows: the temperature is raised to 500±50 ℃ within 5~15 min, and the pressure is raised to 40MPa~50 MPa synchronously with the temperature, and maintained at this temperature and pressure for 5~15 min.

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