N-type PbSe thermoelectric crystal material and preparation method thereof

Abstract

The invention discloses an N-type PbSe thermoelectric crystal material and a preparation method thereof, and belongs to the field of energy materials.The preparation method comprises the steps that Pb blocks, Se particles and PbBr2 powder are evenly mixed, and a mixed material is prepared; the mixed material is placed in a quartz tube, the tip of the bottom of the quartz tube is conical, and the quartz tube is sealed after being vacuumized until the vacuum degree is smaller than 10 <-3 > Pa; placing the sealed quartz tube in a single-temperature-zone vertical tube furnace, setting a temperature control program of the single-temperature-zone vertical tube furnace, dividing the single-temperature-zone vertical tube furnace into a high-temperature zone and a low-temperature zone, and enabling the tip of the bottom of the quartz tube to be located at the horizontal position of the low-temperature zone of the single-temperature-zone vertical tube furnace during placement, and the upper end of the quartz tube is positioned at the horizontal position of the high-temperature area of the single-temperature-area vertical tube furnace to carry out synthesis reaction. The prepared N-type PbSe thermoelectric crystal material also has the advantages of large size, stable performance and the like, and can meet the requirements of large-scale production and practical application.

Description

Technical Field

[0001] The present invention relates to the field of energy materials, and in particular to an N-type PbSe thermoelectric crystal material and a preparation method thereof. Background Art

[0002] Thermoelectric energy conversion technology based on the Seebeck effect and the Peltier effect can realize the direct conversion of thermal energy into electrical energy, which has attracted widespread attention from researchers. Thermoelectric devices have the advantages of simple structure, no moving parts, high reliability, easy maintenance and environmental protection. They are currently used in many fields such as deep space exploration, waste heat recovery, and medical monitoring. Compared with traditional energy conversion methods, thermoelectric materials provide a more efficient and clean energy conversion method. At present, the research focus in the field of thermoelectrics is on materials with excellent thermoelectric properties, such as AgSbTe2, GeTe, and PbTe containing Te elements. However, the scarcity and high cost of Te limit the widespread application of these materials. Therefore, the development of low-cost and efficient thermoelectric materials has become a current research hotspot.

[0003] PbSe, as a thermoelectric material with a highly symmetric face-centered cubic structure, has attracted widespread attention in recent years. The crystal structure of PbSe is a rock salt type (NaCl type) structure, which has good electrical transport and thermoelectric properties. By using spark plasma sintering (SPS), researchers successfully prepared PbSe polycrystalline materials and introduced additional Cu / Zn / Ni to achieve n-type conductivity [Qian, X.; Wang, D.; Zhang, Y.; Wu, H.; Pennycook, SJ; Zheng, L.; Poudeu, PFP; Zhao, L.-D., Contrasting roles of small metallic elements M(M = Cu, Zn, Ni) in enhancing the thermoelectric performance of n-typePbM 0.01Se. J. Mater. Chem. A 2020, 8 (11), 5699-5708.]. The conversion efficiency of thermoelectric materials is related to the thermoelectric figure of merit ZT in the entire working temperature range, so the key to improving thermoelectric efficiency lies in improving the average ZT value. Although polycrystalline PbSe materials can obtain high ZT values ​​in high temperature regions, due to the presence of grain boundaries, carriers in the near-room temperature region will be strongly scattered by grain boundaries, resulting in a significant decrease in mobility, thereby limiting the further improvement of electrical transport performance (power factor PF) in the entire temperature range, resulting in a low average ZT value. Therefore, how to overcome the influence of grain boundaries on electrical properties and improve the thermoelectric performance of PbSe materials has become an important topic in current research on thermoelectric materials. Summary of the invention

[0004] One of the purposes of the present invention is to provide an N-type PbSe thermoelectric crystal material and a preparation method thereof to solve the shortcomings of the N-type PbSe thermoelectric crystal material in the prior art, that is, the material has poor electrical transport performance and thermoelectric performance.

[0005] The present invention is implemented by the following technical scheme, a method for preparing an N-type PbSe thermoelectric crystal material, comprising: S100, mixing Pb blocks, Se particles and PbBr2 powder evenly to prepare a mixed material; S200, placing the mixed material in a quartz tube, the bottom tip of the quartz tube is conical, and evacuating the quartz tube to a vacuum degree of less than 10 -3 After Pa, the quartz tube is sealed; S300, the sealed quartz tube is placed in a single-temperature zone vertical tube furnace, the temperature control program of the single-temperature zone vertical tube furnace is set, and the single-temperature zone vertical tube furnace is divided into a high-temperature zone and a low-temperature zone, and the bottom tip of the quartz tube is placed at a horizontal position of the low-temperature zone of the single-temperature zone vertical tube furnace, and the upper end of the quartz tube is located at a horizontal position of the high-temperature zone of the single-temperature zone vertical tube furnace, and a synthesis reaction is carried out.

[0006] Furthermore, the stoichiometric ratio of the Pb block, Se particle and PbBr2 powder of the mixed material is Pb:Se:Br = 1:1-x:x, wherein 0.05%≤x≤0.3%.

[0007] Furthermore, the mass purity of the Pb block of the mixed material is ≥99.99%, and the mass purity of the Se particles and PbBr2 powder is ≥99.999%.

[0008] Furthermore, the cone angle θ is ≤30°, the outer diameter of the quartz tube is 20 mm, the inner diameter is 17 mm, and the tube wall thickness is 1.5 mm.

[0009] Furthermore, the temperature gradient between the high temperature area and the low temperature area is 100 °C, and the heating rate is 50 °C h -1 ; Cooling rate: 2.5℃ h -1 .

[0010] Furthermore, the temperature control program of the single-temperature zone vertical tube furnace includes: the high-temperature zone is first heated to 1150°C and kept warm for 1440 minutes; then the temperature is reduced to 950°C, and then the temperature is reduced to 25°C along with the furnace; the low-temperature zone is 100°C different from the high-temperature zone, the low-temperature zone is first heated to 1050°C, and kept warm for 1440 minutes; then the temperature begins to be reduced to 850°C, and then the temperature is reduced to 25°C along with the furnace.

[0011] Another aspect of the present invention further provides an N-type PbSe thermoelectric crystal material, which is prepared according to the preparation method described above.

[0012] Furthermore, the chemical formula of the thermoelectric crystal material is PbSe 1-x Br x (0.05%≤x≤0.3%), the carrier concentration range of the thermoelectric crystal material is: ~ 2.9×10 18 - 1.0×10 20 cm -3 .

[0013] Furthermore, the thermoelectric crystal material PbSe 1-x Br x When x = 0.05%, the carrier concentration of the thermoelectric crystal material is ~ 2.9×10 18 cm -3 The crystal mobility at room temperature is ~ 2369 cm² V -1 s -1 , PF greater than ~ 40 μW cm -1 K -2 .

[0014] Furthermore, the thermoelectric crystal material PbSe 1-x Br x When x = 0.25%, the carrier concentration of the thermoelectric crystal material is ~ 2.5×10 19 cm -3 , PF ave is ~ 33.3 μW cm -1 K -2 , ZT ave is ~ 1.2.

[0015] Furthermore, the crystal structure of the thermoelectric crystal material is a face-centered cubic structure, belonging to the Fm m space group.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] 1. The present invention adopts the vertical temperature gradient single temperature zone solidification method to successfully prepare large-sized, high-quality PbSe thermoelectric crystal materials. By using Br as an electron dopant, the material is transformed from intrinsic P-type (holes) to N-type (electrons), and by precisely controlling the Br content (chemical formula is PbSe 1-x Br x , 0.05%≤x≤0.3%), further optimizing the electron concentration.

[0018] 2. The carrier concentration range of the N-type PbSe thermoelectric crystal material prepared by the present invention is ~ 2.9×10 18 - 1.0×10 20 cm -3 , the mobility can reach up to ~ 2369 cm² V at room temperature -1 s -1 , the average power factor (PF) is up to 33.3 μWcm -1 K -2 , the average thermoelectric figure of merit (ZT) is up to 1.2. Compared with polycrystalline materials at the same concentration, the present invention significantly improves the thermoelectric transport performance of N-type PbSe crystals. In addition, the N-type PbSe thermoelectric crystal material prepared by the present invention also has the advantages of large size and stable performance, which can meet the needs of large-scale production and practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0020] Figure 1 This is a schematic diagram of the structure of the single-temperature zone vertical tube furnace used in Examples 1-3 of the present invention.

[0021] Figure 2 This is a physical picture of the N-type PbSe crystal prepared in Example 2 of the present invention.

[0022] Figure 3 is the conductivity σ of the samples in Examples 1-3 of the present invention and Comparative Example 1.

[0023] Figure 4 It is the Seebeck coefficient S of the samples in Examples 1-3 of the present invention and Comparative Example 1.

[0024] Figure 5 It is the power factor PF of the samples of Examples 1-3 of the present invention and Comparative Example 1.

[0025] Figure 6 is the total thermal conductivity κ of the samples of Examples 1-3 and Comparative Example 1 of the present invention tot .

[0026] Figure 7 It is the thermoelectric figure of merit ZT of the samples of Examples 1-3 of the present invention and Comparative Example 1.

[0027] Figure 8 It is the average PF value and average ZT value of the samples of Examples 1-3 of the present invention and Comparative Example 1.

[0028] Table 1 shows the thermoelectric performance parameters of the samples of Examples 1-3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0030] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art in the art of the present invention. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail. Regarding the "comprising", "including", "having", "containing" and the like used herein, they are all open-ended terms, that is, they mean including but not limited to. Unless the context clearly indicates otherwise, the expressions "a" and "one" used herein include plural references. The term "about" used herein means a range of ±20% of the value thereafter. In some embodiments, the term "about" means a range of ±10% of the value thereafter. In some embodiments, the term "about" means a range of ±5% of the value thereafter.

[0031] Example embodiment 1.

[0032] This exemplary embodiment provides a method for preparing an N-type PbSe thermoelectric crystal material, comprising the following steps:

[0033] (1) Pb blocks, Se particles and PbBr2 powder are mixed in a glove box to obtain a mixed material;

[0034] (2) placing the mixed material in step (1) into a quartz tube, evacuating the tube and sealing the tube;

[0035] (3) Placing the vacuum-sealed quartz tube containing the mixed material obtained in step (2) in a single-temperature zone vertical tube furnace to carry out a synthesis reaction to obtain an N-type PbSe thermoelectric crystal material.

[0036] In this embodiment, Pb blocks, Se particles and PbBr2 powder are mixed to obtain a mixed material. In this embodiment, the stoichiometric ratio of the Pb blocks, Se particles and PbBr2 powder is preferably Pb:Se:Br = 1:1-x:x, 0.05%≤x≤0.3%, and the carrier concentration range is: ~ 2.9×10 18 - 1.0×10 20 cm -3 In the present invention, the mass purity of the Pb block is independently ≥99.99%, and the mass purity of the Se particles and PbBr2 powder is ≥99.999%. In this embodiment, the Br is used as an effective N-type dopant to regulate the carrier concentration. 1- Replace Se 2- Additional electrons will be generated, which can effectively increase the carrier concentration of the PbSe material and effectively improve its electrical conductivity, that is, its electrical transport performance, thereby further improving its thermoelectric conversion efficiency.

[0037] After obtaining the mixed material, the present invention puts the mixed material into a quartz tube for vacuum treatment. In this embodiment, the bottom tip of the quartz tube is preferably conical, and the angle of the cone is preferably θ≤30°, so as to generate seed crystals for preferred orientation growth. In this embodiment, the outer diameter of the quartz tube is 20 mm, the inner diameter is 17 mm, and the tube wall thickness is 1.5 mm.

[0038] In this embodiment, the vacuum treatment is preferably to evacuate the quartz tube containing the mixed material to a vacuum degree of less than 10 -3 In this embodiment, the quartz tube is evacuated to a vacuum degree less than 10 -3 Pa can effectively prevent the raw materials from oxidizing during the single crystal growth process.

[0039] After the vacuum treatment is completed, the obtained quartz tube is preferably sealed in this embodiment. The sealing method in this embodiment is not particularly limited, and a method for sealing a quartz tube well known to those skilled in the art can be used. In the specific implementation process of this embodiment, the quartz tube is sealed by using a flame.

[0040] After the vacuum treatment is completed, in this embodiment, the obtained quartz tube containing the mixed material is placed in a single temperature zone vertical tube furnace to perform a synthesis reaction to obtain an N-type PbSe thermoelectric crystal material.

[0041] When the quartz tube containing the mixed material is placed in a single-temperature zone vertical tube furnace, the bottom tip of the quartz tube containing the mixed material is located at the horizontal position of the low temperature zone of the single-temperature zone vertical tube furnace, and the upper end of the quartz tube containing the mixed material is located at the horizontal position of the high temperature zone of the single-temperature zone vertical tube furnace. Before the synthesis reaction is carried out, the single-temperature zone vertical tube furnace is preferably vacuumed to a vacuum degree of less than 10 -1 Pa, thereby avoiding the adverse effects of gas convection on the spatial stability of the temperature range distribution.

[0042] In this embodiment, the temperature control program of the high temperature zone of the single temperature zone vertical tube furnace is preferably: the temperature control program of the high temperature zone of the single temperature zone vertical tube furnace is: first heat up to 1150°C and keep warm for 1440 min; then cool down to 950°C, and then cool down to 25°C along with the furnace.

[0043] The temperature control program of the low temperature zone of the single temperature zone vertical tube furnace is as follows: first heat up to 1050°C and keep warm for 1440 min; then start cooling to 850°C and then cool down to 25°C along with the furnace.

[0044] In this embodiment, the temperature gradient of the high temperature zone and the low temperature zone is 100°C, and the heating rate is independently 50°C h -1 The cooling rate of the first cooling of the high temperature zone and the low temperature zone is 2.5℃ h -1 The second cooling rate is furnace cooling. The present invention can obtain high-quality PbSe crystals by accurately controlling the cooling rate, and can melt various elements in the raw materials by controlling the heating rate.

[0045] Figure 1 This is a schematic diagram of the structure of the single temperature zone vertical tube furnace used in this embodiment. Figure 1 It can be seen that the single-temperature-zone vertical tube furnace includes a quartz tube and a heating furnace chamber. The tip of the quartz tube is a pointed cone. The raw materials in this embodiment are placed in the quartz tube, and the bottom tip of the quartz tube is located at the horizontal position of the low-temperature zone of the single-temperature-zone vertical tube furnace. The upper end of the quartz tube is located at the horizontal position of the high-temperature zone of the single-temperature-zone vertical tube furnace to carry out the synthesis reaction.

[0046] Finally, the N-type PbSe thermoelectric crystal material was prepared, and its crystal structure was face-centered cubic structure, belonging to Fm m space group.

[0047] This exemplary embodiment introduces a method for preparing a high-performance N-type PbSe thermoelectric crystal material. A large-size, high-quality PbSe thermoelectric crystal material was successfully prepared by using a vertical temperature gradient single-zone solidification method. By using Br as an electron dopant, the material was transformed from intrinsic P-type (holes) to N-type (electrons), and by precisely controlling the Br content (chemical formula PbSe 1-x Br x , 0.05%≤x≤0.3%), further optimizing the electron concentration. The carrier concentration range of the N-type PbSe thermoelectric crystal material prepared in this application is ~ 2.9×10 18 cm -3 - 1.0×10 20 cm -3 , the mobility can reach up to ~ 2369 cm² V at room temperature -1 s -1 The average power factor (PF) is up to 33.3 μW cm -1 K -2 , the average thermoelectric figure of merit (ZT) is up to 1.2. Compared with polycrystalline materials at the same concentration, the present application significantly improves the thermoelectric transport performance of N-type PbSe crystals. In addition, the N-type PbSe thermoelectric crystal material prepared in the present application has the advantages of large size and stable performance, which can meet the needs of large-scale production and practical applications.

[0048] Next, the contents of the present invention will be further described in conjunction with specific embodiments.

[0049] Embodiment 1,

[0050] This embodiment provides a method for preparing an N-type PbSe thermoelectric crystal material, comprising the following steps:

[0051] (1) Pb blocks with a purity greater than 99.99%, Se particles with a purity greater than 99.999%, and PbBr2 powder are mixed in a glove box according to a stoichiometric ratio of Pb:Se:Br = 1:0.9975:0.0005 to obtain a mixed material;

[0052] (2) Place the mixed material obtained in step (1) into a quartz tube with a pointed cone at the front end (outer diameter of 20 mm, inner diameter of 17 mm, and tube wall thickness of 1.5 mm), and evacuate the quartz tube containing the mixed material until the vacuum degree is less than 10 -3 Pa, flame-sealed quartz tube;

[0053] (3) placing the quartz tube obtained in step (2) into a single-temperature zone vertical tube furnace, so that the upper end and the bottom tip of the quartz tube are respectively located at the horizontal position of the high temperature zone and the horizontal position of the low temperature zone of the tube furnace, and evacuating the single-temperature zone vertical tube furnace to a vacuum degree of less than 10 -1 Pa; the temperature control program of the single temperature zone vertical tube furnace is set as follows: first heat up to 1150°C and keep warm for 1440 min; then cool down to 950°C, and then cool down to 25°C along with the furnace.

[0054] The temperature gradient of the high temperature zone and the low temperature zone is 100°C, and the heating rate is 50°C h -1 The cooling rate of the first cooling of the high temperature zone and the low temperature zone is 2.5℃ h -1 The second temperature reduction rate is furnace cooling. The synthesis reaction is carried out according to the temperature control program to finally obtain the N-type PbSe thermoelectric crystal material.

[0055] Embodiment 2,

[0056] This embodiment provides a method for preparing an N-type PbSe thermoelectric crystal material. The main preparation process is the same as that of Embodiment 1, and the difference from Embodiment 1 is that:

[0057] The stoichiometric ratios of Pb, Se and Br in this embodiment are 1:0.9995:0.0025 respectively.

[0058] Embodiment 3,

[0059] This embodiment provides a method for preparing an N-type PbSe thermoelectric crystal material. The main preparation process is the same as that of Embodiment 1, and the difference from Embodiment 1 is that:

[0060] The stoichiometric ratios of Pb, Se and Br in this embodiment are 1:0.997:0.003 respectively.

[0061] Comparative Example 1

[0062] The difference from Example 2 is that Comparative Example 1 is polycrystalline PbSe, and the stoichiometric ratio of its components is the same as that of Example 2.

[0063] The samples cut from Examples 1 to 3 and Comparative Example 1 were tested using a Seebeck coefficient / resistance analysis system and a laser thermal conductivity meter, including electrical conductivity σ, Seebeck coefficient S, thermal conductivity κ tot Then the PF value, ZT value, average PF value and average ZT value of the N-type PbSe crystal sample are calculated. The test temperature of the material is 323 K to 773 K, and the average PF value and average ZT value are obtained by calculating the thermoelectric parameters in the entire test temperature range.

[0064] Figure 3is the conductivity σ of Examples 1-3 and Comparative Example 1. 1- With the increase of , the carrier concentration of the sample gradually increases, and the conductivity of Examples 1-3 gradually increases; and from Example 2 and Comparative Example 1 with the same components (same carrier concentration), it can be seen that the conductivity of the sample of Example 2 prepared by the present invention is greater than that of the polycrystalline sample of Comparative Example 1, which is attributed to the higher mobility of PbSe crystals.

[0065] Figure 4 is the Seebeck coefficient S of Examples 1-3 and Comparative Example 1. By using Br as an electron dopant, the material is transformed from intrinsic P-type (holes) to N-type (electrons); and from Example 2 and Comparative Example 1 having the same components, it can be seen that the Seebeck coefficient of the sample of Example 2 prepared by the present invention is similar to that of the polycrystalline sample of Comparative Example 1.

[0066] Figure 5 is the power factor PF of Examples 1-3 and Comparative Example 1. Figure 3-5 It can be seen that by optimizing the carrier concentration and improving the mobility, the carrier concentration of the sample in Example 1 is ~ 2.9×10 18 cm -3 , the crystal mobility is as high as ~ 2369 cm² V at room temperature -1 s -1 , PF up to ~ 40 μW cm -1 K -2 The above; Example 2 sample, the carrier concentration reaches the optimal ~2.5×10 19 cm -3 The average PF value reached 33.3 μW cm -1 K -2 .

[0067] Figure 6 is the total thermal conductivity κ of Examples 1-3 and Comparative Example 1 tot . Figure 7 It is the thermoelectric figure of merit ZT of Examples 1-3 and Comparative Example 1. Figure 8 are the average PF value and average ZT value of Examples 1-3 and Comparative Example 1. Figure 6-8 It can be seen that, combined with the above optimized carrier concentration and mobility, the sample of Example 2 has a ZT of up to 1.73 at high temperature; the average PF value in the test temperature range is up to 33.3 μW cm -1 K -2 , the average ZT value reached up to 1.2.

[0068] Table 1 shows the thermoelectric performance parameters of Examples 1-3 and Comparative Example 1. It can be seen from the table that the carrier concentration, carrier mobility, average PF value and average ZT value of Examples 1-3 and Comparative Example 1. Among them, the carrier concentration of the sample in Example 1 is ~ 2.9×10 18 cm -3 , the crystal mobility is as high as ~ 2369 cm² V at room temperature -1 s -1 ; Example 2 sample, the carrier concentration reaches the optimal ~2.5×10 19 cm -3 The average PF value in the test temperature range reached up to 33.3 μW cm -1 K -2 , the average ZT value reached up to 1.2.

[0069] Table 1. Thermoelectric performance parameters

[0070]

[0071] As can be seen from the above examples, the present invention introduces a method for preparing a high-performance N-type PbSe thermoelectric crystal material. The present invention adopts a vertical temperature gradient single-zone solidification method to successfully prepare a large-size, high-quality PbSe thermoelectric crystal material. By using Br as an electron dopant, the material is transformed from intrinsic P-type (holes) to N-type (electrons), and by precisely controlling the Br content (chemical formula PbSe 1-x Br x , 0.05%≤x≤0.3%), further optimizing the electron concentration. The carrier concentration range of the N-type PbSe thermoelectric crystal material prepared by the present invention is ~ 2.9×10 18 cm -3 - 1.0×10 20 cm -3 , the mobility can reach up to ~ 2369 cm² V at room temperature -1 s -1 The average power factor (PF) is up to 33.3 μW cm -1 K -2 , the average thermoelectric figure of merit (ZT) is up to 1.2. Compared with polycrystalline materials at the same concentration, the present invention significantly improves the thermoelectric transport performance of N-type PbSe crystals. In addition, the N-type PbSe thermoelectric crystal material prepared by the present invention has the advantages of large size and stable performance, which can meet the needs of large-scale production and practical applications.

[0072] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an N-type PbSe thermoelectric crystal material, characterized in that: The preparation method comprises: S100, mixing Pb blocks, Se particles and PbBr2 powder uniformly to prepare a mixed material; S200, placing the mixed material in a quartz tube, the bottom tip of the quartz tube is conical, and evacuating the quartz tube to a vacuum degree of less than 10 -3 After Pa, the quartz tube is sealed; S300, placing the sealed quartz tube in a single-temperature-zone vertical tube furnace, setting a temperature control program for the single-temperature-zone vertical tube furnace, dividing the single-temperature-zone vertical tube furnace into a high-temperature zone and a low-temperature zone, placing the quartz tube so that the bottom tip is located at a horizontal position in the low-temperature zone of the single-temperature-zone vertical tube furnace, and the upper end of the quartz tube is located at a horizontal position in the high-temperature zone of the single-temperature-zone vertical tube furnace, and performing a synthesis reaction.

2. The method for preparing an N-type PbSe thermoelectric crystal material according to claim 1, characterized in that: The stoichiometric ratio of the Pb block, Se particle and PbBr2 powder in the mixed material is Pb:Se:Br = 1:1-x:x, wherein 0.05%≤x≤0.3%.

3. The method for preparing an N-type PbSe thermoelectric crystal material according to claim 1, characterized in that: The mass purity of the Pb block of the mixed material is ≥99.99%, and the mass purity of the Se particles and PbBr2 powder is ≥99.999%.

4. The method for preparing an N-type PbSe thermoelectric crystal material according to claim 1, characterized in that: The angle θ of the cone is ≤30°, the outer diameter of the quartz tube is 20 mm, the inner diameter is 17 mm, and the tube wall thickness is 1.5 mm.

5. The method for preparing an N-type PbSe thermoelectric crystal material according to claim 1, characterized in that: The temperature gradient between the high temperature zone and the low temperature zone is 100°C, and the heating rate is 50°C h -1 ; Cooling rate is 2.5℃h -1 .

6. The method for preparing an N-type PbSe thermoelectric crystal material according to claim 1, characterized in that: The temperature control program of the single-temperature zone vertical tube furnace includes: the high-temperature zone is first heated to 1150°C and kept warm for 1440 minutes; then the temperature is reduced to 950°C, and then the temperature is reduced to 25°C along with the furnace; the low-temperature zone is 100°C different from the high-temperature zone, the low-temperature zone is first heated to 1050°C, and kept warm for 1440 minutes; then the temperature begins to be reduced to 850°C, and then the temperature is reduced to 25°C along with the furnace.

7. An N-type PbSe thermoelectric crystal material, characterized in that: The thermoelectric crystal material is prepared according to the preparation method according to any one of claims 1 to 6, and the chemical formula of the thermoelectric crystal material is PbSe 1-x Br x (0.05%≤x≤0.3%), the carrier concentration range of the thermoelectric crystal material is: 2.9×10 18 ~1.0×10 20 cm -3 .

8. The N-type PbSe thermoelectric crystal material according to claim 7, characterized in that: The thermoelectric crystal material PbSe 1-x Br x When x = 0.05%, the carrier concentration of the thermoelectric crystal material is 2.9×10 18 cm -3 The crystal mobility at room temperature is 2369 cm² V -1 s -1 , PF More than 40 μW cm -1 K -2 .

9. The N-type PbSe thermoelectric crystal material according to claim 7, characterized in that: The thermoelectric crystal material PbSe 1-x Br x When x = 0.25%, the carrier concentration of the thermoelectric crystal material is 2.5×10 19 cm -3 , PF ave 33.3 μW cm -1 K -2 , ZT ave is 1.

2.

10. The N-type PbSe thermoelectric crystal material according to claim 7, characterized in that: The crystal structure of the thermoelectric crystal material is a face-centered cubic structure, belonging to Fm m space group.

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