High-performance N-type Pb (Se, Te)-based thermoelectric material and preparation method and application thereof

Abstract

The invention provides a high-performance N-type Pb (Se, Te)-based thermoelectric material and a preparation method and application thereof. The thermoelectric material provided by the invention is a high-performance Pb (Se, Te)-based thermoelectric material rich in nano precipitated phases and dislocations, the chemical general formula of the thermoelectric material is Cr < 0.01 > Pb < 0.99 > Se < 0.75 > Te < 0.25-y > Cu, and y is greater than 0 and less than or equal to 0.002. By doping chromium in PbSe < 0.75 > Te < 0.25 >, on one hand, a resonance energy level can be introduced to increase the Seebeck coefficient, and on the other hand, a separated nano second phase can reduce the heat conductivity of crystal lattices; excessive copper is introduced on the basis of chromium-doped PbSe < 0.75 > Te < 0.25 >, on one hand, copper atoms fill in intrinsic lead vacancies in Cr < 0.01 > Pb < 0.99 > Se < 0.75 > Te < 0.25 > to increase the mobility, and on the other hand, generated high-density dislocation can further reduce the heat conductivity of crystal lattices. Under the collaborative optimization effect of chromium and copper co-doping on electric heat transportation, the thermoelectric performance of the Pb (Se, Te)-based thermoelectric material in a measurement temperature range is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of thermoelectric semiconductor materials, in particular to a high-performance N-type Pb (Se, Te)-based thermoelectric material and a preparation method and application thereof. Background Art

[0002] Thermoelectric materials can directly convert heat energy into electrical energy without pollution and mechanical loss, which can effectively alleviate the greenhouse effect and fossil energy shortage caused by thermal power generation, but the low conversion efficiency limits its commercial value. To obtain a higher conversion efficiency, the material needs to have a high thermoelectric figure of merit ZT, where ZT = S 2 T / ρκ, S is the Seebeck coefficient, ρ is the resistivity, κ is the total thermal conductivity, and T is the absolute test temperature of the material. κ also includes the carrier thermal conductivity κ contributed by carrier transport E and the lattice thermal conductivity κ contributed by phonons L κ L It is directly determined by the crystal structure of the material and is a parameter that can be independently controlled through defect design. It is also a breakthrough for achieving coordinated control of the material's electroacoustic transport and optimizing thermoelectric performance.

[0003] Lead selenide (PbSe) and lead telluride (PbTe) with highly symmetrical face-centered cubic structures are two typical medium-temperature thermoelectric materials. Their high melting point and low lattice thermal conductivity are favorable conditions for realizing high-efficiency thermoelectric conversion technology in a wide temperature range. Moreover, their solid solubility is high. After forming a solid solution, it can not only adjust the band structure, but also enhance phonon scattering to further reduce the lattice thermal conductivity κ L . However, the enhanced alloy scattering will inevitably cause the mobility to deteriorate. In addition, since the N-type materials of these two systems have only one conduction band involved in electron transport, it is difficult to improve the electrical transport performance by means of band convergence. As a result, their thermoelectric performance has always lagged behind that of the P-type materials of the same system. When composing devices, it is difficult to match them with high-performance P-type materials, which limits the thermoelectric conversion efficiency of the devices. At present, the optimization strategies for the thermoelectric performance of N-type PbSe and PbTe mainly include full-scale hierarchical structure design based on band engineering and phonon engineering.

[0004] Studies have shown that when doping lead selenide with transition metals such as vanadium, molybdenum, tungsten and chromium (V, Mo, W and Cr) to prepare N-type PbSe-based thermoelectric materials, it is easier to obtain the optimal carrier concentration at room temperature due to their low solid solubility in the matrix. 18 -10 19, thereby improving the thermoelectric properties of the material at room temperature (X. Wang, X. Li, Z. Zhang, et al, Thermoelectric properties of n-type transition metal-doped PbSe, Materials Today Physics, 6 (2018), 45-52). However, there are no reports or experimental evidences on the introduction of nano-precipitated phases by doping with chromium or other materials to reduce thermal conductivity in PbSe. Summary of the invention

[0005] The purpose of the present invention is to provide a high-performance N-type Pb (Se, Te)-based thermoelectric material and a preparation method and application thereof. The thermoelectric material is a high-performance N-type Pb (Se, Te)-based thermoelectric material rich in nano-precipitated phases and dislocations. Through band engineering and defect design, the electroacoustic transport characteristics of N-type Pb (Se, Te) are synergistically regulated, thereby improving the overall thermoelectric performance of the material.

[0006] The present invention is achieved in that:

[0007] The high-performance N-type Pb(Se,Te)-based thermoelectric material provided by the present invention has a general chemical formula of Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -yCu, where 0<y≤0.002.

[0008] Preferably, 0.001≤y≤0.002. More preferably, y=0.0015. The test or operating temperature range of the thermoelectric material provided by the present invention is 300-873K, the electrical performance in the whole temperature range is greatly improved, and the introduction of multidimensional defects such as point defects, dense dislocations and nanoprecipitates significantly reduces the lattice thermal conductivity.

[0009] Another aspect of the present invention provides a method for preparing the above-mentioned high-performance N-type Pb(Se,Te)-based thermoelectric material, the specific steps of which are as follows:

[0010] (1) Weighing and packaging: High purity (99.999%) Cu, Cr, Pb, Te and Se elements are weighed and packaged according to Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -yCu (0<y≤0.002) stoichiometric ratio is weighed, the weighed raw materials are sequentially placed into a quartz tube with a suitable inner diameter, and the tube is sealed after vacuum is drawn.

[0011] (2) Melting annealing: The quartz tube that has been vacuum sealed in step (1) is placed in a muffle furnace for high-temperature melting reaction and annealing treatment, and the target product ingot is obtained after natural cooling.

[0012] (3) Hot pressing and sintering: The ingot obtained in step (2) is ground into a uniform powder, placed in a mold for hot pressing and sintering, and after natural cooling, a dense chromium and copper co-doped Pb(Se,Te)-based thermoelectric material is obtained.

[0013] In step (1), the weighed single substance raw material is placed in a flat-bottomed quartz tube with a diameter of 13 mm and a height of 170 mm, and the vacuum degree is not less than 3×10 -3 The tube was sealed at Pa.

[0014] The process flow of high temperature melting and annealing in step (2) is as follows: heating from room temperature to 1000°C to 1200°C over 500 to 1000 minutes, and keeping the temperature for 200 to 600 minutes to allow the melting reaction to proceed fully; then cooling to 500°C to 700°C over 100 to 200 minutes, and keeping the temperature for 2 to 3 days for annealing heat treatment to homogenize the sample and obtain the target product ingot.

[0015] Furthermore, in step (2), the quartz tube placed in the muffle furnace is heated from room temperature to 1100° C. over 720 minutes and kept at this temperature for 360 minutes for high temperature melting reaction, then cooled to 600° C. over 150 minutes and kept at this temperature for 2 to 3 days for annealing treatment.

[0016] In step (3), the ingot is manually ground using an agate mortar for at least 10 minutes, and the ground powder is placed in a mold with an inner diameter of 15 mm.

[0017] The process conditions of hot pressing sintering in step (3) are as follows: the mold containing the target product powder is hot pressed and sintered for 20 to 90 minutes at a sintering temperature of 600° C. to 700° C. and a pressure of 30 to 80 MPa at both ends, and then naturally cooled to room temperature. The atmosphere during the hot pressing process can be a vacuum or other protective gas atmosphere, and the atmosphere environment needs to be maintained until the mold cools to room temperature.

[0018] Furthermore, in step (3), the steel mold containing the powder is heated from room temperature to 500°C in an argon atmosphere for 60 minutes, and then heated to 650°C for 30 minutes to prevent the final temperature from exceeding the target temperature due to the excessive heating rate. Then, the temperature is kept for 60 minutes, and finally the temperature is naturally cooled to room temperature. The pressure is constant at 60 MPa during the entire sintering process.

[0019] The N-type Pb(Se,Te)-based bulk thermoelectric material prepared according to the above steps is a dense and uniform column with a diameter of about 15 mm and a height of about 2.5 mm; its density is 7.9-8.1 g / cm 3; The average thermoelectric figure of merit at 300-873K is 1.09~1.17.

[0020] Based on tellurium alloyed lead selenide (PbSe), the present invention first optimizes PbSe by doping with transition metal chromium. 0.75 Te 0.25 The carrier concentration in the matrix near room temperature makes it exhibit the transport behavior of N-type semiconductor, and the substitution of chromium for lead increases the effective mass of the state density, thereby enhancing the Seebeck coefficient. Then, additional solid solution copper fills the Pb vacancies in the matrix to reduce the scattering of carriers, making up for the deterioration of mobility caused by the increase in effective mass, and significantly improving the electrical transport performance of the material. At the same time, the point defects and nano-precipitates introduced by chromium doping, as well as the high-density dislocations formed by the aggregation of copper atoms, realize the scattering of full-frequency phonons, further suppress the lattice thermal conductivity, and optimize the thermal properties of the material. Under the synergistic optimization of the electrothermal transport properties of the material by chromium and interstitial copper atoms, the y=0.0015 sample reaches a high thermoelectric figure of merit of 0.72 at room temperature, and reaches a maximum thermoelectric figure of merit of 1.51 at 723K. Moreover, the thermoelectric performance of the chromium and copper co-doped samples is better than that of the samples doped with Cu or Cr alone with the same content.

[0021] The present invention proposes a Pb(Se,Te)-based thermoelectric material rich in nano-precipitated phases and dislocations and its preparation method by combining energy band engineering and defect design. By adjusting the content of doping components, the thermoelectric performance is continuously optimized, and the thermoelectric figure of merit in the entire test temperature range is greatly improved. When forming a device, it is expected to match with high-performance P-type thermoelectric materials of the same system, expand the service temperature range of the device and improve the thermoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The absolute values ​​of Seebeck coefficient (|S|) and Hall mobility (μ H ) and power factor (PF = S 2 / ρ) varies with carrier concentration (n H ), where the solid and dashed lines are the theoretical curves fitted by the Single Kane Band model. Figure 1 The literature (H. Wang, A. D. LaLonde, Y. Pei, et al. The criteria for beneficial disorder in thermoelectric solid solutions. Advanced Functional Materials, 2013, 23 (12): 1586-1596) also provides the PbSe-Cl, PbSe-Br, PbSe 0.75 Te0.25 The experimental data of -Br sample are used for comparison.

[0023] Figure 2 1-3 and 1-2 are graphs showing the relationship between the resistivity (ρ) and the temperature (T) of the samples of Examples 1-3 and Comparative Examples 1-2 of the present invention.

[0024] Figure 3 Graph showing the relationship between the Seebeck coefficient (S) and the temperature (T) of the samples of Examples 1-3 and Comparative Examples 1-2 of the present invention.

[0025] Figure 4 The figure is a graph showing the relationship between the power factor (PF) and the temperature (T) of the samples of Examples 1-3 and Comparative Examples 1-2 of the present invention.

[0026] Figure 5 1-3 and 1-2 are graphs showing the relationship between the total thermal conductivity (κ) and the temperature (T) of the samples of Examples 1-3 and Comparative Examples 1-2 of the present invention.

[0027] Figure 6 is the lattice thermal conductivity (κ) of the samples of Examples 1-3 and Comparative Examples 1-2 of the present invention L ) and temperature (T).

[0028] Figure 7 This is the dislocation STEM characterization image of the sample in Example 3 of the present invention.

[0029] Figure 8 The STEM spectrum and EDS surface scan results of the nano-precipitated phase of the sample in Example 3 of the present invention.

[0030] Fig. 9 1 is a graph showing the relationship between the thermoelectric figure of merit (ZT) and the temperature (T) of the samples of Examples 1-3 and Comparative Examples 1-4 of the present invention.

[0031] Fig.10 The average thermoelectric figure of merit (ZT) of the samples of Examples 1-3 and Comparative Examples 1-4 at 300-873K avg ) comparison chart. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with specific embodiments and drawings. The embodiments described below are only used to explain the present invention and do not limit the protection scope of the present invention.

[0033] The high-performance N-type Pb(Se,Te)-based thermoelectric material provided by the present invention has a general chemical formula of Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -yCu, where 0<y≤0.002.

[0034] Example 1

[0035] In this embodiment, the chromium doping content is 1%, the copper doping content is 0.15% (y=0.0015), and the material chemical formula is Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -0.0015Cu, the preparation steps are as follows:

[0036] (1) High-purity (99.999%) bulk raw materials of Cu, Cr, Pb, Te and Se elemental elements were weighed according to the molar ratio of the above chemical formula. The total mass of the weighed raw materials was about 10 g. They were placed in a flat-bottomed quartz tube with a diameter of 13 mm and a height of 170 mm, and the vacuum was drawn to a vacuum degree of less than 3×10 -3 After Pa, seal the tube.

[0037] (2) placing the sealed quartz tube in step (1) into a box-type muffle furnace, heating the temperature from room temperature to 1100° C. over 720 minutes, and keeping the temperature for 360 minutes to perform a high-temperature melting reaction, then cooling the temperature to 600° C. over 150 minutes, and keeping the temperature for 2 days to perform an annealing treatment, and obtaining the above-mentioned target product ingot after natural cooling.

[0038] (3) Breaking the quartz tube, taking out the ingot obtained in step (2) and manually grinding it in an agate mortar for 15 minutes, putting the obtained uniform powder into a mold with an inner diameter of 15 mm, and then putting the mold into a vacuum hot pressing sintering furnace. In an argon atmosphere, the temperature is raised from room temperature to 500°C for 60 minutes, and then raised to 650°C for 30 minutes, and kept at this temperature for 60 minutes. The pressure is kept constant at 60 MPa during the whole sintering process, and finally the temperature is naturally lowered to room temperature to obtain the above Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -0.0015Cu thermoelectric material.

[0039] Example 2

[0040] Compared with Example 1, the chromium doping content in this embodiment is 1%, the copper doping content is 0.1% (y=0.001), and the material chemical formula is Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -0.001Cu, and the rest are the same as in Example 1.

[0041] Example 3

[0042] Compared with Example 1, the chromium doping content in this embodiment is 1%, the copper doping content is 0.2% (y=0.002), and the material chemical formula is Cr 0.01Pb 0.99 Se 0.75 Te 0.25 -0.002Cu, and the rest are the same as in Example 1.

[0043] Comparative Example 1

[0044] In this comparative example, the chromium doping content is 1%, the copper doping content is 0% (y=0), and the material chemical formula is Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 , the preparation steps are as follows:

[0045] (1) High-purity (99.999%) Cr, Pb, Te and Se were weighed according to the molar ratio of the above chemical formula. The total mass of the weighed raw materials was about 10 g. They were placed in a flat-bottomed quartz tube with a diameter of 13 mm and a height of 170 mm, and the vacuum was drawn to a vacuum degree of less than 3×10 -3 After Pa, seal the tube.

[0046] (2) placing the sealed quartz tube in step (1) into a box-type muffle furnace, heating the temperature from room temperature to 1100° C. over 720 minutes, and keeping the temperature for 360 minutes to perform a high-temperature melting reaction, then cooling the temperature to 600° C. over 150 minutes, and keeping the temperature for 2 days to perform an annealing treatment, and obtaining the above-mentioned target product ingot after natural cooling.

[0047] (3) Breaking the quartz tube, taking out the ingot obtained in step (2) and manually grinding it in an agate mortar for 15 minutes, putting the obtained uniform powder into a mold with an inner diameter of 15 mm, and then putting the mold into a vacuum hot pressing sintering furnace. In an argon atmosphere, the temperature is raised from room temperature to 500°C for 60 minutes, and then raised to 600°C for 20 minutes, and kept at this temperature for 60 minutes. The pressure is kept constant at 60 MPa during the whole sintering process, and finally the temperature is naturally lowered to room temperature to obtain the above Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 Thermoelectric materials.

[0048] Comparative Example 2

[0049] In this comparative example, the chromium doping content is 0%, the copper doping content is 0.15%, and the material chemical formula is PbSe 0.75 Te 0.25 -0.0015Cu, the preparation steps are as follows:

[0050] (1) High-purity (greater than 99.9%) Cu, Pb, Te and Se were weighed according to the molar ratio of the above chemical formula. The total mass of the weighed raw materials was about 10 g. They were placed in a flat-bottomed quartz tube with a diameter of 13 mm and a height of 170 mm, and the vacuum was drawn to a vacuum degree of less than 3×10 -3 After Pa, seal the tube.

[0051] (2) placing the sealed quartz tube in step (1) into a box-type muffle furnace, heating the temperature from room temperature to 1100° C. over 720 minutes, and keeping the temperature for 360 minutes to perform a high-temperature melting reaction, then cooling the temperature to 600° C. over 150 minutes, and keeping the temperature for 2 days to perform an annealing treatment, and obtaining the above-mentioned target product ingot after natural cooling.

[0052] (3) Breaking the quartz tube, taking out the ingot obtained in step (2) and manually grinding it in an agate mortar for 15 minutes, and putting the obtained uniform powder into a mold with an inner diameter of 15 mm, and then putting the mold into a vacuum hot pressing sintering furnace, heating from room temperature to 500°C in an argon atmosphere for 60 minutes, and then heating to 600°C for 20 minutes, and keeping the temperature for 60 minutes. The pressure is kept at 60 MPa during the whole sintering process, and finally naturally cooling to room temperature to obtain the above-mentioned PbSe 0.75 Te 0.25 -0.0015Cu thermoelectric material.

[0053] Comparative Example 3

[0054] In this comparative example, the chromium doping content is 1%, the copper doping content is 0.15%, and the material chemical formula is Cr 0.01 Pb 0.99 Se 0.85 Te 0.15 -0.0015Cu, the preparation steps are as follows:

[0055] (1) High-purity (greater than 99.9%) bulk raw materials of Cu, Cr, Pb, Te and Se elemental elements were weighed according to the molar ratio of the above chemical formula. The total mass of the weighed raw materials was about 10 g. They were placed in a flat-bottomed quartz tube with a diameter of 13 mm and a height of 170 mm, and the vacuum was drawn to a vacuum degree of less than 3×10 -3 After Pa, seal the tube.

[0056] (2) placing the sealed quartz tube in step (1) into a box-type muffle furnace, heating the temperature from room temperature to 1100° C. over 720 minutes, and keeping the temperature for 360 minutes to perform a high-temperature melting reaction, then cooling the temperature to 600° C. over 150 minutes, and keeping the temperature for 2 days to perform an annealing treatment, and obtaining the above-mentioned target product ingot after natural cooling.

[0057] (3) Breaking the quartz tube, taking out the ingot obtained in step (2) and manually grinding it in an agate mortar for 15 minutes, putting the obtained uniform powder into a mold with an inner diameter of 15 mm, and then putting the mold into a vacuum hot pressing sintering furnace. In an argon atmosphere, the temperature is raised from room temperature to 500°C for 60 minutes, and then raised to 650°C for 30 minutes, and kept at this temperature for 60 minutes. The pressure is kept constant at 60 MPa during the whole sintering process, and finally the temperature is naturally lowered to room temperature to obtain the above Cr 0.01 Pb 0.99 Se 0.85 Te 0.15 -0.0015Cu thermoelectric material.

[0058] Comparative Example 4

[0059] Compared with Comparative Example 3, the chemical formula of the material in this comparative example is Cr 0.01 Pb 0.99 Se 0.65 Te 0.35 -0.0015Cu, and the rest are the same as those in Comparative Example 3.

[0060] The uniform column samples prepared in the above embodiments and comparative examples are cut by a wire cutting machine and manually polished with sandpaper into regular cubes and discs, wherein the cubes are used for resistivity and Seebeck coefficient tests, and the discs can be used for Hall tests or thermal conductivity tests.

[0061] The samples in Example 1, Comparative Example 1 and Comparative Example 2 were tested for Seebeck coefficient, Hall mobility and power factor. The results are as follows: Figure 1 shown. Figure 1 (a) The curve fitting results of the dependence of the Seebeck coefficient on the carrier concentration show that the theoretical state density effective mass m of the sample without Cr (Cu-doped / Cl-doped / Br-doped sample) is d * ~2.7m e , while the samples containing Cr (Cr doped and Cu-Cr co-doped samples) have a larger effective mass of state density (m d * ~3.7m e ). Therefore, Cr doping increases the effective mass of the state density (m d * ), which is beneficial to the improvement of Seebeck coefficient. Figure 1 (b) shows that additional copper doping increases the carrier concentration of the sample while maintaining a high mobility, which is related to the fact that copper atoms occupy intrinsic Pb vacancies and reduce carrier scattering. Finally, the enhancement of the Seebeck coefficient of the Cr-Cu co-doped sample compensates for the deterioration of mobility caused by the increase in effective mass, and a higher power factor is obtained at 300K than that of the copper single doped sample, as shown in Figure 2. Figure 1(c) as shown.

[0062] Figure 2 The relationship between the resistivity and temperature of the samples of Examples 1-3 and Comparative Examples 1-2 is shown in FIG. Figure 3 The relationship between the Seebeck coefficient and temperature of the samples of Examples 1-3 and Comparative Examples 1-2 is shown in FIG. Figure 4 The power factor and temperature of the samples of Examples 1-3 and Comparative Examples 1-2 are shown in FIG. Figure 2-Figure 4 It can be seen that, thanks to the enhancement of the Seebeck coefficient by the Cr resonance energy level and the optimization of the carrier mobility by filling the intrinsic Pb vacancies by copper atoms, the power factor in the entire temperature range is significantly improved, among which the sample with a chromium content of 1% and a copper content of 0.15% in Example 1 obtains the maximum power factor at room temperature.

[0063] Theoretically, the lattice thermal conductivity of Cr-Cu co-doped samples should be lower than that of single copper or chromium doped samples. Figure 5-Figure 6 The results of thermal performance tests show that in the near-room temperature range, the lattice contraction caused by chromium doping reduces the solid solubility of copper in the samples of Examples 1-3, resulting in a weakening of the phonon scattering mechanism induced by copper atoms, and the lattice thermal conductivity is higher than that of the copper-doped sample in Comparative Example 2. As the temperature rises, the excess copper continues to dissolve, and the lattice thermal conductivity of the Cr-Cu co-doped sample in the high-temperature range is lower than that of the single copper or chromium doped sample. Due to the abundant point defects and dense dislocations (such as Figure 7 ) and chromium-rich precipitates (as shown Figure 8 The multi-scale structures (as shown in FIG. 1 ) significantly enhance the multi-frequency phonon scattering and significantly reduce the lattice thermal conductivity. The sample with a copper content of 0.20% in Example 3 has a thermal conductivity of 0.35 Wm at 723 K. -1 K -1 The minimum lattice thermal conductivity is much lower than that of the samples doped with chromium and copper alone in Comparative Examples 1 and 2.

[0064] Co-doping of PbSe with Cr and Cu 0.75 Te 0.25 Under the coordinated optimization of matrix electroacoustic transport, the thermoelectric performance of the samples in Examples 1-3 is significantly improved over the entire test temperature range compared to the chromium-doped sample in Comparative Example 1. In particular, the room temperature thermoelectric figure of merit (ZT) of the sample with a copper doping content of 0.15% in Example 2 reaches 0.72, and a peak ZT of 1.51 and a high average ZT of 1.17 are obtained at 300-873K, surpassing the chromium-doped sample in Comparative Example 1, the copper-doped sample in Comparative Example 2, and the samples with other Te / Se solid solution ratios in Comparative Examples 3-4, such as Figure 9-10As shown, the material prepared by the present invention realizes high-performance N-type Pb(Se,Te)-based thermoelectric material in a wide temperature range, and is expected to form an efficient thermoelectric segmented module with P-type materials with matching performance under the same system, which can be applied to the fields of temperature difference power generation and thermoelectric refrigeration.

[0065] The present invention is not limited to the above-mentioned individual preferred embodiments. There are various modifications, substitutions and improvements within the principle and scope of the present invention. These changes should be included in the scope of protection required by the present invention.

Claims

1. A high-performance N-type Pb(Se,Te)-based thermoelectric material, characterized in that: Its chemical formula is Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -yCu, where 0<y≤0.

002.

2. The high performance N-type Pb(Se,Te)-based thermoelectric material according to claim 1, characterized in that: 0.001≤y≤0.002。 3. The high performance N-type Pb(Se,Te)-based thermoelectric material according to claim 2, characterized in that: y＝0.0015。 4. A method for preparing a high-performance N-type Pb(Se,Te)-based thermoelectric material, characterized in that: The steps include: (1) Weighing and packaging: High-purity Cu, Cr, Pb, Te and Se elements are weighed according to Cr 0.01 Pb 0.99 Se 0.75 Te 0.25 -yCu stoichiometric ratio is weighed, the weighed raw materials are placed in a quartz tube in turn, and the tube is sealed after vacuuming; 0<y≤0.002; (2) Melting annealing: placing the quartz tube that has been vacuum sealed in step (1) into a muffle furnace for high-temperature melting reaction and annealing treatment, and obtaining a smelted target product ingot after natural cooling; (3) Hot pressing and sintering: The ingot obtained in step (2) is ground into a uniform powder, placed in a mold for hot pressing and sintering, and after natural cooling, a dense chromium and copper co-doped Pb(Se,Te)-based thermoelectric material is obtained.

5. The method for preparing a high-performance N-type Pb(Se,Te)-based thermoelectric material according to claim 4, characterized in that: When the tube is sealed in step (1), the vacuum pressure in the tube is less than 3×10 -3 Pa.

6. The method for preparing a high-performance N-type Pb(Se,Te)-based thermoelectric material according to claim 4, characterized in that: The process flow of high temperature melting reaction and annealing treatment in step (2) is as follows: heating from room temperature to 1000°C to 1200°C over 500 to 1000 minutes, and keeping the temperature for 200 to 600 minutes to carry out melting reaction; then cooling to 500°C to 700°C over 100 to 200 minutes, and keeping the temperature for 2 to 3 days to carry out annealing treatment.

7. The method for preparing a high-performance N-type Pb(Se,Te)-based thermoelectric material according to claim 6, characterized in that: In step (2), the quartz tube placed in the muffle furnace is heated from room temperature to 1100° C. over 720 minutes and kept at this temperature for 360 minutes for high temperature melting reaction, then cooled to 600° C. over 150 minutes and kept at this temperature for 2 to 3 days for annealing treatment.

8. The method for preparing a high-performance N-type Pb(Se,Te)-based thermoelectric material according to claim 4, characterized in that: The process conditions of hot pressing sintering in step (3) are as follows: the mold containing the target product powder is hot pressed and sintered for 20 to 90 minutes at a sintering temperature of 600°C to 700°C and a pressure of 30 to 80 MPa at both ends, and then naturally cooled to room temperature; the atmosphere during the hot pressing process is a vacuum or protective gas atmosphere.

9. The method for preparing a high-performance N-type Pb(Se,Te)-based thermoelectric material according to claim 8, characterized in that: In step (3), the mold containing the powder is heated from room temperature to 500°C in an argon atmosphere for 60 minutes, then to the target sintering temperature of 650°C for 30 minutes, the pressure at both ends is adjusted to 60 MPa, kept at this temperature for 60 minutes, and finally cooled naturally to room temperature.

10. Application of the high-performance N-type Pb(Se, Te)-based thermoelectric material according to any one of claims 1 to 3 and the high-performance N-type Pb(Se, Te)-based thermoelectric material prepared by the method according to any one of claims 4 to 9 in thermoelectric conversion technology.

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