A lead sulfide-based material, a method for producing the same, and a thermoelectric device

Abstract

This application discloses a lead sulfide-based material and its preparation method, as well as a thermoelectric device, belonging to the field of lead sulfide-based material preparation. The preparation method includes the following steps: placing the raw material in a temperature field for heat treatment to obtain the lead sulfide-based material; the temperature field includes a first temperature zone, a second temperature zone, and a third temperature zone sequentially arranged along a first direction; the heat treatment sequentially includes a heating stage, a first isothermal stage, a first cooling stage, a second isothermal stage, a second cooling stage, a third isothermal stage, and a cooling stage. This application mainly reduces the thermal conductivity of the lead sulfide-based material by placing the raw material in a specific temperature field for gradient heat treatment, while significantly improving its various thermoelectric performance parameters, meeting the requirements for thermoelectric devices and showing broad application prospects.

Description

Technical Field

[0001] This application belongs to the field of lead sulfide-based material preparation, specifically relating to a lead sulfide-based material and its preparation method, and a thermoelectric device. Background Technology

[0002] In recent years, with the accelerated advancement of social informatization and intelligentization, the demand for energy in daily life has continued to rise, making energy issues a crucial and pressing issue of our time. Against this backdrop, thermoelectric materials, due to their ability to directly convert heat energy into electrical energy, have attracted widespread attention.

[0003] Among numerous thermoelectric materials, lead sulfide (PbS)-based materials have attracted considerable attention from researchers due to their abundant elemental reserves, low raw material costs, and high Hall mobility. PbS-based materials share similar crystal and electronic band structures with the traditional high-performance thermoelectric material lead telluride (PbTe), but at a significantly lower cost. For example, the cost of some PbS-based materials can be reduced to about 20% of that of lead telluride-based materials. However, the inherently high lattice thermal conductivity of lead sulfide severely limits the improvement of its thermoelectric performance, thus hindering its widespread application in thermoelectric devices. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art. Therefore, the purpose of this application is to provide a lead sulfide-based material, its preparation method, and a thermoelectric device. This application mainly involves subjecting the raw material to gradient heat treatment in a specific temperature field, which not only reduces the thermal conductivity of the lead sulfide-based material but also significantly improves its various thermoelectric performance parameters, meeting the requirements for thermoelectric devices and showing broad application prospects.

[0005] The first aspect of this application discloses a method for preparing a lead sulfide-based material. According to embodiments of this application, the method for preparing the lead sulfide-based material includes the following steps: The raw materials are placed in a temperature field for heat treatment to obtain lead sulfide-based materials. The temperature field includes a first temperature zone, a second temperature zone, and a third temperature zone arranged sequentially along a first direction; The heat treatment sequentially includes a heating stage, a first isothermal stage, a first cooling stage, a second isothermal stage, a second cooling stage, a third isothermal stage, and a cooling stage; The following requirements must be met during the heating phase: a) The raw material is placed in the second temperature zone and heated to a molten state to form a molten material; b) The heating endpoint temperature of the first temperature zone, the second temperature zone, and the third temperature zone is T0; The following requirements must be met during the first isothermal stage: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone are all maintained at T0; The following requirements must be met during the first cooling stage: a) The temperatures in both the first and second temperature zones are maintained at T0; b) The temperature in the third temperature zone decreases from T0 to T1; c) The molten material remains in a molten state; The following requirements must be met during the second isothermal stage: a) The temperatures in both the first and second temperature zones are maintained at T0; b) The temperature of the third temperature zone is maintained at T1; c) The molten material begins to move along the first direction from the second temperature zone to the third temperature zone, forming a solid product; The following requirements must be met during the second cooling stage: a) The temperatures in both the first and second temperature zones decrease from T0 to T2; b) The temperature in the third temperature zone decreases from T1 to T2; c) The solid product stops moving; The following requirements must be met during the third isothermal stage: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone are all maintained at T2; The following requirements must be met during the cooling phase: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone all decrease from T2 to T3.

[0006] The lead sulfide-based material preparation method of the above embodiments of this application mainly involves placing the raw materials in a specific temperature field for gradient heat treatment. This not only reduces the thermal conductivity of the lead sulfide-based material but also significantly improves its various thermoelectric performance parameters, which can meet the requirements of thermoelectric devices and has broad application prospects.

[0007] In addition, the method for preparing lead sulfide-based materials according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, T0 and T1 satisfy the following relationship: 250℃≤T0-T1≤350℃; And / or, T1 and T2 satisfy the following relationship: 200℃≤T1-T2≤300℃; And / or, the T3 satisfies the following relationship: 20℃≤T3≤40℃; And / or, the movement time t1 of the molten material in the second temperature zone satisfies the following relationship: 2000min≤t1≤3000min; And / or, the movement time t2 of the molten material in the third temperature zone satisfies the following relationship: 4500min≤t2≤5500min; And / or, the cooling rate V1 of the third temperature zone from T0 to T1 is < 3℃ / min; And / or, the cooling rate V2 of both the first temperature zone and the second temperature zone from T0 to T2 is < 5℃ / min; And / or, the cooling rate V3 of the third temperature zone from T1 to T2 is < 5℃ / min; And / or, the temperature of the first temperature zone, the second temperature zone, and the third temperature zone all decrease from T2 to T3 at a rate V4 < 10℃ / min.

[0008] In some embodiments of this application, T0 satisfies the following relationship: T0-Tmax>20℃, where Tmax is the highest temperature among all the melting point temperatures of the raw materials; And / or, the first direction includes the vertical direction; And / or, the vertical lengths of the first temperature zone, the second temperature zone, and the third temperature zone are equal.

[0009] In some embodiments of this application, the lead sulfide-based material includes a lead sulfide-based material as shown in Formula 1, wherein Formula 1 is Pb. 1-3 / 2x Sb x S, where 0 ≤ x ≤ 0.005.

[0010] In some embodiments of this application, the following requirements are met during the heating phase: a) Elemental lead, elemental sulfur, and elemental antimony are placed in the second temperature zone in a certain proportion and heated to a molten state to form a molten material; b) The first temperature zone, the second temperature zone and the third temperature zone are all heated from room temperature to T0 at a heating rate of 1-3℃ / min, where T0 is 1150~1200℃.

[0011] In some embodiments of this application, the duration of the first isothermal stage is 950-1100 min; And / or, the time of the second isothermal stage is the sum of t1 and t2.

[0012] In some embodiments of this application, the cooling rate V1 is 0.8~1.5℃ / min; And / or, the cooling rate V2 is 0.5~1℃ / min; And / or, the cooling rate V3 is 0.1~1℃ / min; And / or, the cooling rate V4 is 1~10℃ / min.

[0013] In some embodiments of this application, the movement speed V0 of both the molten material and the solid product is 0.5-1 mm / h.

[0014] The second aspect of this application discloses a lead sulfide-based material. According to an embodiment of this application, the lead sulfide-based material is prepared using the preparation method for lead sulfide-based materials described in the first aspect. As a result, the thermoelectric properties of this lead sulfide-based material are significantly improved.

[0015] A third aspect of this application discloses a thermoelectric device. According to an embodiment of this application, the thermoelectric device comprises the lead sulfide-based material described in the second aspect. Therefore, the thermoelectric conversion efficiency of this thermoelectric device is significantly improved.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the internal structure of the vertical Bridgeman growth furnace in the embodiments of this application.

[0018] Figure 2 This is a schematic diagram of the furnace temperature field distribution in the embodiments of this application.

[0019] Figure 3 This is a graph showing the relationship between the conductivity of the lead sulfide-based thermoelectric material in Example 1 of this application and temperature.

[0020] Figure 4 This is a graph showing the relationship between the thermal conductivity and temperature of the lead sulfide-based thermoelectric material of Example 1 of this application.

[0021] Figure 5 This is a graph showing the Seebeck coefficient of the lead sulfide-based thermoelectric material of Example 1 of this application as a function of temperature.

[0022] Figure 6 This is a graph showing the relationship between the power factor and temperature change of the lead sulfide-based thermoelectric material of Example 1 of this application.

[0023] Figure 7This is a graph showing the relationship between the thermoelectric figure of merit and temperature change of the lead sulfide-based thermoelectric material of Example 1 of this application.

[0024] Figure 8 This is a graph showing the relationship between the conductivity and temperature of the lead sulfide-based thermoelectric materials in Examples 1-3 of this application.

[0025] Figure 9 This is a graph showing the Seebeck coefficient of the lead sulfide-based thermoelectric materials in Examples 1-3 of this application as a function of temperature.

[0026] Figure 10 This is a graph showing the relationship between the power factor and temperature change of the lead sulfide-based thermoelectric materials in Examples 1-3 of this application.

[0027] Explanation of reference numerals in the attached figures: 1: First heating zone; 2: Second heating zone; 3: Third heating zone; 4: Crucible; I: High temperature zone; II: Medium temperature zone; III: Low temperature zone. Detailed Implementation

[0028] The embodiments of this application are described in detail below, and the embodiments described below with reference to the accompanying drawings are merely exemplary and intended to explain this application, and should not be construed as limiting this application.

[0029] The first aspect of this application discloses a method for preparing a lead sulfide-based material. According to embodiments of this application, the method for preparing the lead sulfide-based material includes the following steps: The raw materials are placed in a temperature field for heat treatment to obtain lead sulfide-based materials. The temperature field includes a first temperature zone, a second temperature zone, and a third temperature zone arranged sequentially along a first direction; The heat treatment sequentially includes a heating stage, a first isothermal stage, a first cooling stage, a second isothermal stage, a second cooling stage, a third isothermal stage, and a cooling stage; The following requirements must be met during the heating phase: a) The raw material is placed in the second temperature zone and heated to a molten state to form a molten material; b) The heating endpoint temperature of the first temperature zone, the second temperature zone, and the third temperature zone is T0; The following requirements must be met during the first isothermal stage: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone are all maintained at T0; The following requirements must be met during the first cooling stage: a) The temperatures in both the first and second temperature zones are maintained at T0; b) The temperature in the third temperature zone decreases from T0 to T1; c) The molten material remains in a molten state; The following requirements must be met during the second isothermal stage: a) The temperatures in both the first and second temperature zones are maintained at T0; b) The temperature of the third temperature zone is maintained at T1; c) The molten material begins to move along the first direction from the second temperature zone to the third temperature zone, forming a solid product; The following requirements must be met during the second cooling stage: a) The temperatures in both the first and second temperature zones decrease from T0 to T2; b) The temperature in the third temperature zone decreases from T1 to T2; c) The solid product stops moving; The following requirements must be met during the third isothermal stage: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone are all maintained at T2; The following requirements must be met during the cooling phase: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone all decrease from T2 to T3.

[0030] The lead sulfide-based material preparation method described in the above embodiments of this application mainly involves subjecting the raw materials to gradient heat treatment in a specific temperature field. This not only reduces the thermal conductivity of the lead sulfide-based material but also significantly improves its various thermoelectric performance parameters, meeting the requirements for thermoelectric devices and showing broad application prospects. Specifically: On the one hand, by setting up a temperature field including a first temperature zone, a second temperature zone, and a third temperature zone in this application, the function is to ensure that the temperature gradient can be precisely controlled, and the first temperature zone helps to ensure the stability of the temperature in the second temperature zone.

[0031] On the other hand, the synergistic mechanism of the above-mentioned gradient heat treatment in this application is as follows: The purpose of the heating stage is to allow the raw materials in the crucible to react with each other.

[0032] The purpose of the first isothermal stage is to ensure that the raw materials in the crucible are in a molten state during the descent process (i.e., before the growth process).

[0033] The role of the first cooling stage is to form a temperature field and create growth conditions. At the same time, by controlling the temperature of the third temperature zone from T0 to T1 to meet the condition of 250℃≤T0-T1≤350℃ (for example, it can be 260℃, 280℃, 290℃, 300℃, 320℃ or any of the above values), it is beneficial for the slow and stable growth of the crystal, ensuring that a complete single crystal can be obtained. If the value of "T0-T1" is too large (such as 400℃) or too small (such as 200℃), twinning will occur in the crystal, that is, the bottom of the crucible does not crystallize but the top crystallizes first.

[0034] The role of the second isothermal stage is to ensure the stability of the temperature field during crystal growth, which is part of the crystal growth stage. At the same time, for example, at this time, the molten material begins to move from the second temperature zone to the third temperature zone along the first direction and is controlled to "2000min≤t1≤3000min (for example, it can be 2000min, 2200min, 2300min, 2500min, 2700min, 3000min or any of the above values)" and "4500min≤t2≤5500min (for example, it can be 4500min, 4800min, 5000min, 5200min or any of the above values)", which helps to reduce the temperature field fluctuations caused by the crystal descent. If the time t1 and t2 are too large or too small, the crystal may form grain boundaries or twins.

[0035] The purpose of the second cooling stage is to cool the crystal to the annealing temperature. At the same time, it can control the temperature to "200℃≤T1-T2≤300℃ (e.g., 200℃, 220℃, 240℃, 280℃, 300℃ or any of the above values)," which helps to reduce the possibility of crystal dissociation or cracking. If the value of "T1-T2" is too large or too small, it may cause crystal dissociation.

[0036] The role of the third isothermal stage: the annealing stage; it helps to make the crystal more uniform and to bring the crystal to a thermodynamically stable state (the lowest energy state).

[0037] The purpose of the cooling stage is to cool the crystal to room temperature and obtain a single crystal that has completed its growth.

[0038] According to some specific embodiments of this application, the cooling rate V1 of the third temperature zone from T0 to T1 is <3℃ / min; by controlling the cooling rate V1 <3℃ / min, this application helps to ensure that the raw materials react fully before becoming molten, reduce sulfur volatilization, and lower the vapor pressure of sulfur.

[0039] According to some specific embodiments of this application, the temperature of both the first temperature zone and the second temperature zone decreases from T0 to T2 at a rate V2 < 5℃ / min; by controlling the cooling rate V2 < 5℃ / min, this application helps to reduce the dissociation or cracking of single crystals caused by stress.

[0040] According to some specific embodiments of this application, the cooling rate V3 of the third temperature zone from T1 to T2 is <5℃ / min; by controlling the cooling rate V3 <5℃ / min, this application helps to reduce the dissociation or cracking of single crystals caused by stress.

[0041] According to some specific embodiments of this application, the temperature of the first temperature zone, the second temperature zone, and the third temperature zone all decrease from T2 to T3 at a cooling rate V4 < 10℃ / min; by controlling the cooling rate V4 < 10℃ / min, this application helps to reduce the dissociation or cracking of crystals.

[0042] According to some specific embodiments of this application, T0 satisfies the following relationship: T0-Tmax>20℃, where Tmax is the highest temperature among all the melting point temperatures of the raw materials; And / or, the first direction includes the vertical direction; And / or, the vertical lengths of the first temperature zone, the second temperature zone, and the third temperature zone are equal.

[0043] In some embodiments of this application, the lead sulfide-based material includes a lead sulfide-based material as shown in Formula 1, wherein Formula 1 is Pb. 1-3 / 2x Sb x S, where 0 ≤ x ≤ 0.005.

[0044] In some embodiments of this application, the following requirements are met during the heating phase: a) Elemental lead, elemental sulfur, and elemental antimony are placed in the second temperature zone in a certain proportion and heated to a molten state to form a molten material; b) The first temperature zone, the second temperature zone and the third temperature zone are all heated from room temperature to T0 at a heating rate of 1-3℃ / min, where T0 is 1150~1200℃.

[0045] In some embodiments of this application, the duration of the first isothermal stage is 950-1100 min; and / or, the duration of the second isothermal stage is the sum of t1 and t2.

[0046] In some embodiments of this application, the cooling rate V1 is 0.8~1.5℃ / min; and / or, the cooling rate V2 is 0.5~1℃ / min; and / or, the cooling rate V3 is 0.1~1℃ / min; and / or, the cooling rate V4 is 1~10℃ / min.

[0047] In some embodiments of this application, the movement speed V0 of both the molten material and the solid product is 0.5-1 mm / h.

[0048] The second aspect of this application discloses a lead sulfide-based material. According to an embodiment of this application, the lead sulfide-based material is prepared using the preparation method for lead sulfide-based materials described in the first aspect. As a result, the thermoelectric properties of this lead sulfide-based material are significantly improved.

[0049] A third aspect of this application discloses a thermoelectric device. According to an embodiment of this application, the thermoelectric device comprises the lead sulfide-based material described in the second aspect. Therefore, the thermoelectric conversion efficiency of this thermoelectric device is significantly improved.

[0050] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0051] Example 1 This embodiment provides a lead sulfide-based material, the chemical formula of which is Pb. 0.9925 Sb 0.005 S.

[0052] The preparation method of the above-mentioned lead sulfide-based material includes the following steps: (1) Batching: The three elemental raw materials, lead, sulfur and antimony, were mixed in a molar ratio of 0.9925:1:0.005 to obtain a total mass of 30g of mixed raw material. The raw material was then placed into a conical quartz crucible (the specific dimensions of the conical quartz crucible are a length of 10cm and a diameter of 2cm), and a vacuum of 1×10⁻⁶ was applied. -3 After Pa, the conical quartz crucible is sealed; the sealed conical quartz crucible is then placed into a quartz tube, and the quartz tube is evacuated to a vacuum level not exceeding 1×10⁻⁶. -3 After Pa, the tube is sealed to obtain a sealed quartz tube containing the raw material (the specific dimensions of the sealed quartz tube are 12cm in length and 2.5cm in diameter).

[0053] (2) Furnace loading: Place the sealed quartz tube containing the raw material into the Bridgman furnace (the specific dimensions of the Bridgman furnace are: inner diameter of 20cm, outer diameter of 30cm, and total length of 80cm). The Bridgman furnace is placed vertically and is arranged in the vertical direction with a first temperature zone (vertical length of 10cm), a second temperature zone (vertical length of 10cm), and a third temperature zone (vertical length of 10cm). Specifically, the sealed quartz tube containing the raw material is placed in the second temperature zone of the Bridgman furnace (if the height of the midpoint of the second temperature zone in the vertical direction is considered as 0cm, then the height of the sealed quartz tube containing the raw material in the vertical direction is -2cm, and it is rotated at 5rpm throughout the process).

[0054] (3) Gradient heat treatment: including heating stage, first isothermal stage, first cooling stage, second isothermal stage, second cooling stage, third isothermal stage and cooling stage, as detailed below: (3.1) Heating stage: The first temperature zone, the second temperature zone and the third temperature zone are simultaneously heated from room temperature (specifically 25°C) to the same endpoint temperature T0 (T0=1150°C) at a constant heating rate for 720 min; so that the raw material is heated to a molten state to form a molten material.

[0055] (3.2) First isothermal stage: The temperature of the first temperature zone, the second temperature zone and the third temperature zone are all maintained at T0, and the molten material is kept at T0 temperature for 1050 min.

[0056] (3.3) First cooling stage: The temperatures of the first and second temperature zones are maintained at T0. The temperature of the third temperature zone is cooled from T0 to T1 (T1=850℃, and T0-T1=300℃) at a constant cooling rate of V1 (V1=1.0℃ / min) for 300 min.

[0057] (3.4) Second isothermal stage: When the temperature of the third temperature zone in the first cooling stage stabilizes at T1, the sealed quartz tube containing molten material begins to move vertically from the second temperature zone to the third temperature zone at a constant speed of V0 (V0=0.8mm / h). The total downward movement time in this stage is 7500min (i.e. t1+t2=7500min, of which the movement time t1 in the second temperature zone is 2250min and the movement distance is 30mm; the movement time t2 in the third temperature zone is 5250min and the movement distance is 70mm), forming a solid product.

[0058] (3.5) Second cooling stage: The solid product stops moving; and the first temperature zone, the second temperature zone and the third temperature zone all begin to cool down; specifically, the temperature of the first temperature zone and the second temperature zone both cool down from T0 to T2 (T2=600℃) at a constant cooling rate of V2 (V2=0.61℃ / min), and the temperature of the third temperature zone cools down from T1 to T2 (T2=600℃) at a constant cooling rate of V3 (V3=0.28℃ / min).

[0059] (3.6) Third isothermal stage: The temperature of the first temperature zone, the second temperature zone and the third temperature zone are all maintained at T2. (3.7) Cooling stage: The temperatures of the first temperature zone, the second temperature zone and the third temperature zone are all cooled from T2 to T3 (T3=30℃) at a constant cooling rate of V4 (V4=5℃ / min); when the temperature stabilizes at T3, lead sulfide-based material is obtained.

[0060] Example 2 This embodiment provides a lead sulfide-based material and its preparation method, which differs from Example 1 only in that: (1) The chemical formula of lead sulfide-based materials is Pb 0.994 Sb 0.004 S.

[0061] Example 3 This embodiment provides a lead sulfide-based material and its preparation method, which differs from Example 1 only in that: (1) The chemical formula of lead sulfide-based materials is Pb 0.9955 Sb 0.003 S.

[0062] Example 4 This embodiment provides a lead sulfide-based material and its preparation method, which differs from Example 1 only in that: (1) The chemical formula of lead sulfide-based materials is Pb 0.995 Sb 0.005 S 0.5 Se 0.5 ; (2) T0 is adjusted from 1150℃ to 1100℃; (3) T1 was adjusted from 850℃ to 800℃.

[0063] Test Example 1 This test example demonstrates the performance testing of the lead sulfide-based material obtained in the above embodiments. The testing method is as follows: A diamond wire cutter was used to cut the single-crystal samples to obtain 3*3*9 mm diameter pieces. 3 With 6*6*1.5mm 3The bulk material was then measured using a ZEM3 conductivity and Seebeck coefficient measurement system and tested for thermal diffusivity using an LFA457 laser thermal conductivity meter.

[0064] Test results are as follows Figures 3-10 As shown; where, Figure 3 This is a graph showing the relationship between the conductivity and temperature of the lead sulfide-based thermoelectric material of Example 1 of this application. Figure 4 This is a graph showing the relationship between the thermal conductivity and temperature of the lead sulfide-based thermoelectric material of Example 1 of this application. Figure 5 This is a graph showing the Seebeck coefficient of the lead sulfide-based thermoelectric material of Example 1 of this application as a function of temperature. Figure 6 This is a graph showing the relationship between the power factor and temperature of the lead sulfide-based thermoelectric material of Example 1 of this application. Figure 7 This is a graph showing the relationship between the thermoelectric figure of merit and temperature change of the lead sulfide-based thermoelectric material of Example 1 of this application. Figure 8 This is a graph showing the relationship between the conductivity and temperature of the lead sulfide-based thermoelectric materials in Examples 1-3 of this application. Figure 9 This is a graph showing the Seebeck coefficient of the lead sulfide-based thermoelectric materials in Examples 1-3 of this application as a function of temperature. Figure 10 This is a graph showing the relationship between the power factor and temperature change of the lead sulfide-based thermoelectric materials in Examples 1-3 of this application.

[0065] Depend on Figures 3-10 It can be seen that the lead sulfide-based material prepared in this application has excellent thermoelectric properties. Furthermore, as the Sb doping concentration increases, the conductivity of the single crystal gradually increases and the Seebeck coefficient gradually decreases. In terms of overall performance, Example 1 achieved the best average zT value and high-temperature zT value.

[0066] Test Example 2 Based on the above test examples, this test example tests the thermoelectric performance parameters of the lead sulfide-based materials obtained in Examples 1 to 3 above.

[0067] Test method: Single crystal samples were cut into 3*3*9 mm pieces using a diamond wire cutter. 3 With 6*6*1.5mm 3 The bulk material was then measured using a ZEM3 conductivity and Seebeck coefficient measurement system and tested for thermal diffusivity using an LFA457 laser thermal conductivity meter.

[0068] The test results are shown in Table 1; Note: The experimental data in Table 1 are the results of room temperature tests.

[0069] Table 1

[0070] As shown in Table 1, the lead sulfide-based material prepared in this application has excellent thermoelectric properties. The introduction of Sb can improve the conductivity, but reduce the Seebeck coefficient and the power factor at room temperature. However, the performance gradually improves in the wide temperature range and the high temperature range.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing a lead sulfide-based material, characterized in that, Includes the following steps: The raw materials are placed in a temperature field for heat treatment to obtain lead sulfide-based materials. The temperature field includes a first temperature zone, a second temperature zone, and a third temperature zone arranged sequentially along a first direction; The heat treatment sequentially includes a heating stage, a first isothermal stage, a first cooling stage, a second isothermal stage, a second cooling stage, a third isothermal stage, and a cooling stage; The following requirements must be met during the heating phase: a) The raw material is placed in the second temperature zone and heated to a molten state to form a molten material; b) The heating endpoint temperature of the first temperature zone, the second temperature zone, and the third temperature zone is T0; The following requirements must be met during the first isothermal stage: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone are all maintained at T0; The following requirements must be met during the first cooling stage: a) The temperatures in both the first and second temperature zones are maintained at T0; b) The temperature in the third temperature zone decreases from T0 to T1; c) The molten material remains in a molten state; The following requirements must be met during the second isothermal stage: a) The temperatures in both the first and second temperature zones are maintained at T0; b) The temperature of the third temperature zone is maintained at T1; c) The molten material begins to move along the first direction from the second temperature zone to the third temperature zone, forming a solid product; The following requirements must be met during the second cooling stage: a) The temperatures in both the first and second temperature zones decrease from T0 to T2; b) The temperature in the third temperature zone decreases from T1 to T2; c) The solid product stops moving; The following requirements must be met during the third isothermal stage: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone are all maintained at T2; The following requirements must be met during the cooling phase: a) The temperatures of the first temperature zone, the second temperature zone, and the third temperature zone all decrease from T2 to T3.

2. The method for preparing lead sulfide-based materials according to claim 1, characterized in that, The relationship between T0 and T1 is as follows: 250℃≤T0-T1≤350℃; And / or, T1 and T2 satisfy the following relationship: 200℃≤T1-T2≤300℃; And / or, the T3 satisfies the following relationship: 20℃≤T3≤40℃; And / or, the movement time t1 of the molten material in the second temperature zone satisfies the following relationship: 2000min≤t1≤3000min; And / or, the movement time t2 of the molten material in the third temperature zone satisfies the following relationship: 4500min≤t2≤5500min; And / or, the cooling rate V1 of the third temperature zone from T0 to T1 is < 3℃ / min; And / or, the cooling rate V2 of both the first temperature zone and the second temperature zone from T0 to T2 is < 5℃ / min; And / or, the cooling rate V3 of the third temperature zone from T1 to T2 is < 5℃ / min; And / or, the temperature of the first temperature zone, the second temperature zone, and the third temperature zone all decrease from T2 to T3 at a rate V4 < 10℃ / min.

3. The method for preparing lead sulfide-based materials according to claim 1, characterized in that, The T0 satisfies the following relationship: T0-Tmax>20℃, where Tmax is the highest temperature among all the melting points of the raw materials; And / or, the first direction includes the vertical direction; And / or, the vertical lengths of the first temperature zone, the second temperature zone, and the third temperature zone are equal.

4. The method for preparing lead sulfide-based materials according to any one of claims 1 to 3, characterized in that, The lead sulfide-based material includes lead sulfide-based materials as shown in Chemical Formula 1, where Chemical Formula 1 is Pb. 1-3 / 2x Sb x S, where 0 ≤ x ≤ 0.

005.

5. The method for preparing lead sulfide-based materials according to claim 4, characterized in that, The following requirements must be met during the heating phase: a) Elemental lead, elemental sulfur, and elemental antimony are placed in the second temperature zone in a certain proportion and heated to a molten state to form a molten material; b) The first temperature zone, the second temperature zone and the third temperature zone are all heated from room temperature to T0 at a heating rate of 1-3℃ / min, where T0 is 1150~1200℃.

6. The method for preparing lead sulfide-based materials according to claim 4, characterized in that, The duration of the first isothermal stage is 950~1100 min; And / or, the time of the second isothermal stage is the sum of t1 and t2.

7. The method for preparing lead sulfide-based materials according to claim 4, characterized in that, The cooling rate V1 is 0.8~1.5℃ / min; And / or, the cooling rate V2 is 0.5~1℃ / min; And / or, the cooling rate V3 is 0.1~1℃ / min; And / or, the cooling rate V4 is 1~10℃ / min.

8. The method for preparing lead sulfide-based materials according to claim 4, characterized in that, The velocity V0 of both the molten material and the solid product is 0.5-1 mm / h.

9. A lead sulfide-based material, characterized in that, The lead sulfide-based material is prepared by the method for preparing lead sulfide-based materials according to any one of claims 1 to 8.

10. A thermoelectric device, characterized in that, The thermoelectric device comprises the lead sulfide-based material as described in claim 9.

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