A type n-lead selenide-based thermoelectric material, its preparation method and application

Abstract

This invention discloses an n-type lead selenide-based thermoelectric material, its preparation method, and its application, belonging to the field of energy material preparation technology. The chemical formula of the n-type lead selenide-based thermoelectric material is Pb. 1‑ x Cr x Se 0.998 Cl 0.002 (0.002≤x≤0.006); The material is prepared by mixing high-purity raw materials according to the molar ratio in the chemical formula, and using a high-temperature melting method combined with a discharge plasma sintering method to obtain the target lead selenide-based thermoelectric material. This invention utilizes the dual doping of Cr and Cl elements; the synergistic effect of these two elements greatly improves the electrical conductivity of the n-type lead selenide-based thermoelectric material while simultaneously reducing its thermal conductivity, resulting in the prepared Pb... 0.996 Cr 0.004 Se 0.998 Cl 0.002 The material not only exhibits a high thermoelectric figure of merit at a high temperature of 723 K, but also achieves an average thermoelectric figure of merit of 1.037 between medium and low temperatures of 300-673 K. This invention can significantly improve the thermoelectric figure of merit of n-type lead selenide-based thermoelectric materials, which is beneficial not only for improving the conversion efficiency of thermoelectric power generation devices but also for expanding their industrial applications.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric material preparation technology, specifically relating to an n-type lead selenide-based thermoelectric material, its preparation method, and its application. Background Technology

[0002] Fossil fuels play a fundamental role in industrial development, but inevitably lead to climate change and energy crises. The low energy efficiency in actual industrial production results in significant waste heat dissipation, prompting increasing research into thermoelectric materials. Thermoelectric materials, based on the Seebeck effect, utilize the material's inherent charge carriers as the working medium to directly convert waste heat into electrical energy. They are clean, pollution-free, noiseless, and zero-emission energy conversion materials with enormous potential commercial value. Therefore, developing low-cost, high-performance, and environmentally friendly thermoelectric materials is the ultimate goal for the widespread application of thermoelectric technology. The thermoelectric conversion efficiency of a thermoelectric material is determined by its thermoelectric figure of merit (ZT), ZT = S 2 σ T / κ tot ,in T , σ , S and κ tot These are absolute temperature, electrical conductivity, Seebeck coefficient, and thermal conductivity, respectively; the higher the thermoelectric figure of merit or average thermoelectric figure of merit, the stronger the material's ability to convert thermal energy and electrical energy into each other.

[0003] PbSe, PbTe, and PbS belong to the same class of thermoelectric materials and have similar crystal structures. Compared to PbTe, the content of selenium (Se) in the Earth's crust (0.05 ppm) is 50 times that of tellurium (Te) (0.001 ppm); compared to PbS, PbSe is safer. Therefore, PbSe shows great potential as a thermoelectric material. In recent years, researchers have been actively studying ways to improve the thermoelectric properties of PbSe and expand its application temperature range, resulting in the development of many high-performance n-type PbSe thermoelectric materials. Improving the thermoelectric properties of PbSe by doping it with multiple elements is a common method; Chinese patent document CN115991603A discloses a method for preparing Cr / Te co-doped PbSe-based thermoelectric materials, which uses Cr and Te co-doped PbSe thermoelectric materials to prepare PbSe thermoelectric materials. 0.97 Cr 0.03 Se 0.94 Te 0.06 The thermoelectric figure of merit (ZT) at 673 K is 4.4 times that of the uncomposite PbSe thermoelectric material, but the thermoelectric figure of merit (ZT) in the medium and low temperature range is lower. avgThe concentration of PbSe is only around 0.3; PbSe is doped with Sb, Cu, and Te. The introduction of these three elements helps to reduce the lattice thermal conductivity, ensuring a relatively high Seebeck coefficient, and ultimately preparing PbSe. 0.9875 Sb 0.0125 Cu 0.0125 Se 0.99 Te 0.01 The peak figure of merit (ZT) of this material is 1.44, but the average figure of merit (ZT) in the mid-to-low temperature region is relatively low (J. Mater. Chem. A, 2024, 12, 8583-8591); Chinese patent document with publication number CN118234360A describes the preparation of PbSe by doping with Ga and Sb to obtain Pb. 1-x (GaSb) x Se 1-y Pb 0.99875 (GaSb) 0.00125 Se 0.999 The thermoelectric figure of merit (TFP) of PbSe-based thermoelectric materials is around 0.6 at room temperature, but only about 0.9 at high temperatures. Therefore, developing a method for preparing PbSe-based thermoelectric materials that exhibits both a high TFP at high temperatures (above 723 K) and an excellent average TFP in the mid-to-low temperature range (300-573 K), thereby expanding the application temperature range of PbSe-based thermoelectric materials, is an important research topic in PbSe thermoelectric materials. Summary of the Invention

[0004] The purpose of this invention is to provide an n-type lead selenide-based thermoelectric material, its preparation method, and its application. The preparation method optimizes the PbSe thermoelectric material by co-doping with Cr and Cl elements, so that the thermoelectric material not only has a high thermoelectric figure of merit at high temperatures, but also has an excellent average thermoelectric figure of merit in the medium and low temperature range, which greatly expands the application temperature range of lead selenide-based thermoelectric materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides an n-type lead selenide-based thermoelectric material, wherein the chemical formula of the n-type lead selenide-based thermoelectric material is Pb. 1-x Cr x Se 1-y Cl y Where 0.002≤x≤0.006, 0.001≤y≤0.003.

[0007] Secondly, the present invention provides a method for preparing an n-type lead selenide-based thermoelectric material, comprising the following steps:

[0008] (1) Combine the elements Pb, Cr, and Se and the compound PbCl2 according to the chemical formula Pb1-x Cr x Se 1-y Cl y The ingredients are prepared in a stoichiometric ratio of 0.002≤x≤0.006, 0.001≤y≤0.003, mixed, and then placed in a quartz tube for vacuum sealing and melting reaction to obtain the material precursor.

[0009] (2) Grind, sinter into blocks and slice the obtained material precursor to obtain n-type lead selenide-based thermoelectric material.

[0010] Preferably, in step (1), the melting reaction conditions are: heating at a rate of 80~100℃ / h to 900~1200℃ and then holding at that temperature for 2~6h.

[0011] Preferably, in step (2), the sintering block is heated to 500-600°C at a heating rate of 50-120°C / min and held for 5-15 minutes; the sintering pressure is 30-40 MPa.

[0012] Thirdly, the present invention provides an application of the above-mentioned n-type lead selenide-based thermoelectric material in thermoelectric conversion devices.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. The method for preparing n-type PbSe-based thermoelectric materials provided by this invention successfully achieves synergistic optimization of the performance of n-type PbSe-based thermoelectric materials across the entire temperature range (medium-low temperature and high temperature regions) by doping PbSe-based thermoelectric materials with Cr and Cl elements. In the medium-low temperature region (300-573K), Cl provides sufficient charge carriers to maintain the material's electrical conductivity at a high level, while Cr effectively reduces lattice thermal conductivity, thereby reducing the material's thermal conductivity without a significant decrease in the Seebeck coefficient. Therefore, the thermoelectric figure of merit in the low-temperature region is significantly improved. In the high-temperature region (573-723K), Cl ensures the stability of high-temperature electrical transport, while Cr ensures that the total thermal conductivity is suppressed to an extremely low value. The synergistic effect of the two allows the thermoelectric figure of merit to continue to rise and reach its peak in the high-temperature region. In summary, Cl, as an n-type dopant, stabilizes the electronic structure of the matrix by providing a high carrier concentration; Cr, while acting as a strong phonon scattering center, blocks the trend of the Seebeck coefficient decreasing with increasing carrier concentration through band modulation. The synergistic effect of Cr and Cl elements enables the material to maintain a high Seebeck coefficient while achieving high electrical conductivity. This synergistic mechanism allows PbSe-based thermoelectric materials to exhibit excellent performance across different temperature ranges. Therefore, co-doping with Cr and Cl, through multi-scale control of electron and phonon transport respectively, can simultaneously improve the thermoelectric figure of merit in both high-temperature and mid-to-low-temperature regions.

[0015] 2. The n-type PbSe-based thermoelectric material provided by this invention not only exhibits excellent thermoelectric figure of merit in the high-temperature region, but also shows a significant improvement in the thermoelectric figure of merit (ZT) in the medium- and low-temperature regions. The PbSe-based thermoelectric material prepared in Examples 1-7 of this invention... 0.998 Cr 0.002 Se 0.998 Cl 0.002 Pb 0.997 Cr 0.003 Se 0.998 Cl 0.002 Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 Pb 0.995 Cr 0.005 Se 0.998 Cl 0.002 Pb 0.994 Cr 0.006 Se 0.998 Cl 0.002 Pb 0.998 Cr 0.002 Se 0.999 Cl 0.001 and Pb 0.998 Cr 0.002 Se 0.998 Cl 0.003 The thermoelectric figures of merit at 723 K were 1.27, 1.34, 1.39, 1.31, 1.22, 1.21, and 1.23, respectively, compared to single-doped Cl PbSe. 0.998 Cl 0.002 The thermoelectric figure of merit (TFP) at 723 K (1.15) increased by as much as 10.43%, 18.26%, 20.86%, 13.91%, 6.08%, 5.22%, and 6.95%, respectively. Compared with the thermoelectric material with single Cr doping (Adv. Energy Mater. 2015, 1401977), the TFP at 723 K (~1.0) increased by as much as 27%, 36%, 39%, 31%, 22%, 21%, and 23%, respectively. 1-x Cr x Se 1-y Cl y The average thermoelectric figure of merit for thermoelectric materials in the range of 300-573 K are 0.908, 0.976, 1.037, 0.936, 0.851, 0.885, and 0.892, respectively, compared to PbSe. 0.998 Cl 0.002The average thermoelectric figure of merit (TFP) between 300 and 573 K is 0.607, representing increases of up to 49.59%, 60.79%, 70.84%, 54.20%, 40.19%, 49.58%, and 60.79%, respectively. Compared to single-doped Cr thermoelectric materials (Adv. Energy Mater. 2015, 1401977), the average TFP in the 300-573 K range (~0.74) is increased by up to 22.7%, 31.8%, 40.1%, 26.5%, 15%, 22.7%, and 31.8%, respectively. In summary, Pb... 1-x Cr x Se 1-y Cl y The thermoelectric figure of merit (TGI) is 0.545-0.674 at room temperature (300K), 0.851-1.037 in the medium-low temperature range (300-573K), and 1.21-1.39 at high temperature (723K); among them, Pb has the best thermoelectric performance. 0.996 Cr 0.004 Se 0.998 Cl 0.002 The thermoelectric material exhibits good thermoelectric figures of merit at room temperature (300K), medium and low temperature range (300-573K), and high temperature range (723K), which are 0.674, 1.037, and 1.39, respectively.

[0016] 3. The method for preparing n-type PbSe-based thermoelectric materials provided by this invention can regulate Pb through the synergistic effect of co-doping with Cr and Cl elements. 1-x Cr x Se 1-y Cl y Crystal structure and grain growth kinetics. Cl reduces melt viscosity and promotes compositional homogeneity. By reducing the viscosity of the transient liquid phase or surface diffusion layer at grain boundaries, it significantly accelerates the cross-grain boundary diffusion rate of atoms / ions. Cr effectively introduces lattice strain to inhibit excessive grain growth and further promotes material diffusion. The synergy between Cl and Cr creates a crystal growth environment during sintering with unimpeded diffusion but controlled grain boundaries. This synergistic effect allows the material to achieve sufficient densification under lower external pressure through efficient diffusion creep and grain boundary slip mechanisms, without relying on high pressure for forced plastic deformation, thus successfully preparing high-density, high-performance thermoelectric bulk materials. Therefore, the preparation process of this invention can significantly reduce the sintering pressure of bulk sintering through the synergistic effect of co-doped Cl and Cr elements. The sintering pressure in this invention is 30-40 MPa, while the disclosed sintering pressure for single-doped Cr is 80 MPa. The reduction in sintering pressure not only lowers equipment requirements and significantly saves equipment investment but also effectively reduces energy consumption.

[0017] Therefore, this invention provides a highly promising technical path for developing high-performance, low-cost, tellurium (Te)-free PbSe-based thermoelectric devices, opening up a new era for the application of PbSe in a wider range of industrial waste heat recovery (such as automobile exhaust and chemical processes) and near-room temperature and other medium-low temperature fields. Attached Figure Description

[0018] Figure 1 X-ray diffraction patterns of powder samples prepared in Examples 1-5 and Comparative Example 1 of this invention;

[0019] Figure 2 The conductivity graphs of the samples prepared in Examples 1-5 and Comparative Example 1 of this invention as a function of temperature are shown.

[0020] Figure 3 The diagram shows the Seebeck coefficient of the samples prepared in Examples 1-5 and Comparative Example 1 as a function of temperature.

[0021] Figure 4 The thermal conductivity diagrams of the samples prepared in Examples 1-5 and Comparative Example 1 of this invention as a function of temperature are shown.

[0022] Figure 5 The thermoelectric figure of merit diagrams of the samples prepared in Examples 1-5 and Comparative Example 1 of this invention as a function of temperature;

[0023] Figure 6 Pb prepared in Example 3 0.996 Cr 0.004 Se 0.998 Cl 0.002 Surface SEM image and EDS energy spectrum. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by known methods.

[0025] Prepare the raw materials: elemental Pb, Cr, Se, and compound PbCl2. The purity of the Pb particles is 99.99% (Beijing Haoke Technology Co., Ltd.), the purity of the Se particles is 99.99% (Hebei Luohong Technology Co., Ltd.), the purity of the Cr particles is 99.99% (Beijing Zhongjinyan New Materials Technology Co., Ltd.), and the compound PbCl2 is analytical grade (Shanghai Maclean Biochemical Technology Co., Ltd.). Example 1

[0026] 1) Combine elemental Pb, Cr, and Se with compound PbCl2 according to the chemical formula Pb0.998 Cr 0.002 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, mixed, and then placed in a quartz tube and vacuum sealed for melting reaction. The reaction conditions were: heating rate of 100℃ / h to raise the furnace temperature from room temperature to 1000℃ and holding for 4h, and then cooling to room temperature to obtain the material precursor.

[0027] 2) Grind the precursor material obtained in step 1) into powder, fill the powder into a graphite mold for sintering, pressurize at 40 MPa, raise the temperature to 600°C at a rate of 60°C / min, and sinter for 5 min to obtain bulk material. Slice the material to obtain n-type Pb. 0.998 Cr 0.002 Se 0.998 Cl 0.002 Thermoelectric materials. Example 2

[0028] The elements Pb, Cr, and Se, and the compound PbCl2 were arranged according to the chemical formula Pb 0.997 Cr 0.003 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, and the remaining experimental steps were the same as in Example 1. Example 3

[0029] The elements Pb, Cr, and Se, and the compound PbCl2 were arranged according to the chemical formula Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, and the remaining experimental steps were the same as in Example 1. Example 4

[0030] The elements Pb, Cr, and Se, and the compound PbCl2 were arranged according to the chemical formula Pb 0.995 Cr 0.005 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, and the remaining experimental steps were the same as in Example 1. Example 5

[0031] The elements Pb, Cr, and Se, and the compound PbCl2 were arranged according to the chemical formula Pb 0.994 Cr 0.006 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, and the remaining experimental steps were the same as in Example 1. Example 6

[0032] Compared with Example 1, except that elemental Pb, Se and compound PbCl2 are prepared according to the chemical formula Pb0.998 Cr 0.002 Se 0.999 Cl 0.001 The ingredients were prepared according to the stoichiometric ratio, and the rest of the experimental steps were the same. Example 7

[0033] Compared with Example 1, except that elemental Pb, Se and compound PbCl2 are prepared according to the chemical formula Pb 0.998 Cr 0.002 Se 0.997 Cl 0.003 The ingredients were prepared according to the stoichiometric ratio, and the rest of the experimental steps were the same. Example 8

[0034] 1) Elements Pb, Cr, and Se, and compound PbCl2 according to the chemical formula Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, mixed, and then placed in a quartz tube and vacuum sealed for melting reaction. The reaction conditions were as follows: the furnace temperature was raised from room temperature to 1200℃ at a heating rate of 90℃ / h and held for 3h. After cooling to room temperature, the material precursor was obtained.

[0035] 2) Grind the precursor material obtained in step 1) into powder, fill the powder into a graphite mold for sintering, pressurize at 40 MPa, raise the temperature to 600°C at a rate of 60°C / min, and sinter for 5 min to obtain bulk material. Slice the material to obtain n-type Pb. 0.996 Cr 0.004 Se 0.998 Cl 0.002 Thermoelectric materials. Example 9

[0036] 1) Elements Pb, Cr, and Se, and compound PbCl2 according to the chemical formula Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, mixed, and then placed in a quartz tube for vacuum sealing and melting reaction. The reaction conditions were as follows: the furnace temperature was raised from room temperature to 900℃ at a heating rate of 80℃ / h and held for 5h. After cooling to room temperature, the material precursor was obtained.

[0037] 2) Grind the precursor material obtained in step 1) into powder, fill the powder into a graphite mold for sintering, pressurize at 30 MPa, raise the temperature to 500°C at a rate of 50°C / min, and sinter for 10 min to obtain PbSe bulk material. Slice the material to obtain n-type Pb. 0.996 Cr 0.004 Se 0.998 Cl 0.002Thermoelectric materials. Example 10

[0038] 1) Elements Pb, Cr, and Se, and compound PbCl2 according to the chemical formula Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, mixed, and then placed in a quartz tube and vacuum sealed for melting reaction. The reaction conditions were as follows: the furnace temperature was raised from room temperature to 1200℃ at a heating rate of 90℃ / h and held for 3h. After cooling to room temperature, the material precursor was obtained.

[0039] 2) Grind the precursor material obtained in step 1) into powder, fill the powder into a graphite mold for sintering, pressurize at 35 MPa, raise the temperature to 550°C at a rate of 100°C / min, and sinter for 15 min to obtain bulk material. Slice the material to obtain n-type Pb. 0.996 Cr 0.004 Se 0.998 Cl 0.002 Thermoelectric materials. Example 11

[0040] 1) Elements Pb, Cr, and Se, and compound PbCl2 according to the chemical formula Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, mixed, and then placed in a quartz tube and vacuum sealed for melting reaction. The reaction conditions were: heating rate of 100℃ / h to raise the furnace temperature from room temperature to 1100℃ and holding for 4h, and then cooling to room temperature to obtain the material precursor.

[0041] 2) Grind the precursor material obtained in step 1) into powder, fill the powder into a graphite mold for sintering, pressurize at 35 MPa, raise the temperature to 600°C at a rate of 80°C / min, and sinter for 10 min to obtain bulk material. Slice the material to obtain n-type Pb. 0.996 Cr 0.004 Se 0.998 Cl 0.002 Thermoelectric materials. Example 12

[0042] 1) Elements Pb, Cr, and Se, and compound PbCl2 according to the chemical formula Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, mixed, and then placed in a quartz tube and vacuum sealed for melting reaction. The reaction conditions were: heating rate of 80℃ / h to raise the furnace temperature from room temperature to 1000℃ and holding for 5h, and then cooling to room temperature to obtain the material precursor.

[0043] 2) Grind the precursor material obtained in step 1) into powder, fill the powder into a graphite mold for sintering, pressurize at 40 MPa, heat to 500°C at a rate of 90°C / min, and sinter for 5 min to obtain bulk material. Slice the material to obtain n-type Pb. 0.996 Cr 0.004 Se 0.998 Cl 0.002 Thermoelectric materials. Comparative Example 1

[0044] Compared with Example 1, except that elemental Pb, Se and compound PbCl2 are prepared according to the chemical formula PbSe 0.998 Cl 0.002 The ingredients were prepared according to the stoichiometric ratio, and the rest of the experimental steps were the same. Comparative Example 2

[0045] Compared with Example 1, except that elemental Pb, Se and Cr are prepared according to the chemical formula Pb 0.996 Cr 0.004 The ingredients were prepared according to the stoichiometric ratio of Se, and the rest of the experimental steps were the same. Performance testing:

[0046] 1) Compare and analyze the crystal structures of the samples prepared in Examples 1-5 and Comparative Example 1; grind the samples into powder using an agate mortar and pestle, and perform powder X-ray diffraction analysis. (See attached...) Figure 1 As shown, the test angle was 20-80 degrees. The X-ray diffraction peaks of all prepared samples were completely consistent with the lead selenide standard card. No diffraction peaks of other impurities were detected, which proves that the samples prepared by the method provided by this invention are all pure phase products. Figure 6 The Pb prepared in Example 3 is given. 0.996 Cr 0.004 Se 0.998 Cl 0.002 SEM characterization of the sample surface and EDS spectra of elemental distribution. The SEM image of the sample shows that it is sintered and dense with no obvious pores; the surface scan spectrum shows that Pb, Se, Cl and Cr are uniformly distributed.

[0047] 2) The electrical properties of the materials prepared in Examples 1-5 and Comparative Example 1 were tested using the CTA-3S thermoelectric material testing system from Beijing Creo Technology Co., Ltd. The relationship between conductivity and temperature is shown in the attached figure. Figure 2 As shown in Table 1, the electrical conductivity of the prepared material decreases with increasing temperature, and further decreases with increasing Cr content. (See attached table.) Figure 3 As shown, the Seebeck coefficients of the materials prepared in Examples 1-5 and Comparative Example 1 gradually increase with increasing doping concentration.

[0048] 3) The thermal diffusivity of the materials prepared in Examples 1-5 and Comparative Example 1 was measured using a Netzsch LFA467 laser flare thermal conductivity meter. D Tests were conducted, and the thermal conductivity was measured. κ = C p Dρ The density was calculated. ρ Specific heat was obtained through Archimedes' method. C p Calculated using the Dulong-Petty formula. The relationship between thermal conductivity and temperature is shown in the attached figure. Figure 4 As shown in Table 1, when y = 0.002, Pb 1-x Cr x Se 0.998 Cl 0.002 The thermal conductivity of the material first decreases and then increases with the increase of Cr doping content.

[0049] 4) Figure 5 This is a graph showing the relationship between the thermoelectric figure of merit and temperature for the thermoelectric materials prepared in Examples 1-5 and Example 1 of this invention. The Pb prepared in Examples 1-5... 0.998 Cr 0.002 Se 0.998 Cl 0.002 Pb 0.997 Cr 0.003 Se 0.998 Cl 0.002 Pb 0.996 Cr 0.004 Se 0.998 Cl 0.002 Pb 0.995 Cr 0.005 Se 0.998 Cl 0.002 and Pb 0.994 Cr 0.006 Se 0.998 Cl 0.002 And the PbSe prepared in Comparative Example 1 0.998 Cl 0.002 The thermoelectric figure of merit (ZT) at 723 K were 1.27, 1.34, 1.39, 1.31, 1.22, and 1.15, respectively, for the n-type Pb obtained in Example 3. 0.996 Cr 0.004 Se 0.998 Cl 0.002 It exhibits the highest thermoelectric figure of merit at 723 K; the average thermoelectric figures of merit between 300 and 573 K are 0.908, 0.976, 1.037, 0.936, 0.851, and 0.607, respectively. The samples prepared in Examples 6-7 of this invention with varying Cl doping amounts (Pb) 0.998 Cr0.002 Se 0.999 Cl 0.001 and Pb 0.998 Cr 0.002 Se 0.998 Cl 0.003 Pb prepared in Examples 8-12 with modified process conditions 0.996 Cr 0.004 Se 0.998 Cl 0.002 The thermoelectric figures of merit (TGIs) of the samples at 723 K were 1.21, 1.23, 1.38, 1.39, 1.37, 1.38, and 1.39, respectively; the average TGIs between 300 and 573 K were 0.885, 0.892, 0.983, 1.028, 0.979, 0.997, and 1.031, respectively. In summary, Pb... 1-x Cr x Se 1-y Cl y The thermoelectric figure of merit (TGI) is 0.545-0.674 at room temperature (300K), 0.851-1.037 in the medium-low temperature range (300-573K), and 1.21-1.39 at high temperature (723K); among them, Pb has the best thermoelectric performance. 0.996 Cr 0.004 Se 0.998 Cl 0.002 The thermoelectric material exhibits good thermoelectric figures of merit (PbSe) at room temperature (300 K), in the medium-low temperature range (300-573 K), and at high temperature (723 K), with values ​​of 0.674, 1.037, and 1.39, respectively. This demonstrates that co-doping PbSe with Cr and Cl elements can effectively improve the PbSe of this thermoelectric material in the medium-low temperature range, thereby expanding the application range of this type of thermoelectric material.

[0050]

[0051] Table 1 shows the thermoelectric figure of merit (TGI) of thermoelectric materials doped with different amounts of Cr and Cl at 723 K, 300 K, and the average TGI from 300 to 573 K. When the Cl doping amount is 0.002, the thermal conductivity of the thermoelectric material first decreases and then increases with the increase of Cr doping amount, reaching its lowest value when the Cr doping amount in the prepared thermoelectric material is 0.004. Figure 4 (As shown). The co-doping strategy of Cr and Cl elements introduces defects of different element types and lattice scales, which not only reduces the negative impact of scattered phonon electron mobility but also effectively achieves ordered lattice manipulation, thus enabling Pb... 1- x Cr x Se 0.998 Cl 0.002The thermoelectric figure of merit (ZT) of the thermoelectric materials in the medium and low temperature range was effectively improved. By comparing the ZT values ​​of the thermoelectric materials prepared in the examples and comparative examples at 723 K, 300 K, and 300-573 K, it can be found that the ZT values ​​of the thermoelectric materials prepared by co-doping of Cr and Cl elements at 300 K and 723 K are improved by as much as 34-251% and 21-54% respectively compared with the ZT values ​​of the thermoelectric materials prepared by single doping of Cr and Cl elements; the average ZT value of the thermoelectric materials prepared by doping of Cr and Cl elements in the 300-573 K range is improved by as much as 40%-72.2% compared with the average ZT value of the undoped thermoelectric materials.

[0052] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An n-type lead selenide-based thermoelectric material, characterized in that: The n-type lead selenide-based thermoelectric material has the chemical formula Pb. 1- x Cr x Se 1-y Cl y Where 0.002≤x≤0.006, 0.001≤y≤0.003; The preparation method of the n-type lead selenide-based thermoelectric material includes the following steps: (1) Combine the elements Pb, Cr, and Se and the compound PbCl2 according to the chemical formula Pb 1-x Cr x Se 1-y Cl y The ingredients are prepared in a stoichiometric ratio of 0.002≤x≤0.006, 0.001≤y≤0.003, mixed, and then placed in a quartz tube for vacuum sealing and melting reaction to obtain the material precursor; the melting reaction conditions are: heating at a rate of 80~100℃ / h to 900~1200℃ and holding at that temperature for 2~6h. (2) Grind, sinter, and slice the material precursor to obtain n-type lead selenide-based thermoelectric material; In step (2), the sintering block is heated to 500-600℃ at a heating rate of 50-120℃ / min and held for 5-15min; the sintering pressure is 30-40MPa.

2. The application of the n-type lead selenide-based thermoelectric material as described in claim 1 in thermoelectric conversion devices.

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