A cubic tin selenide-based thermoelectric crystal and a method of making the same

Abstract

The application provides a cubic tin selenide-based thermoelectric crystal and a preparation method thereof, and relates to the technical field of crystal synthesis. The preparation method comprises the following steps: tin, silver, antimony and selenium are weighed and put into a first container, vacuumizing and sealing; the first container is heated to 953-1373K and kept for 15-30h; after cooling, the alloy ingot is taken out and put into a second container, vacuumizing and sealing; the second container is heated to 973-1373K and kept for 5-30h, then cooled to 923-1173K at a first cooling rate, then cooled to 873-923K at a second cooling rate, and then cooled to room temperature at a third cooling rate. The application prepares a bulk cubic tin selenide single crystal material, realizes a very high grain orientation degree, and can obtain a high-performance thermoelectric material.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal synthesis, and in particular to a cubic tin selenide-based thermoelectric crystal and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Thermoelectric technology (TE) offers great potential for recovering low-quality waste heat due to its ability to directly convert heat into electricity. Based on two major physical effects, the Seebeck effect and the Peltier effect, thermoelectric materials can be used for applications such as thermoelectric power generation, thermoelectric cooling, and precise temperature control. Thermoelectric devices are solid-state devices with a simple structure, no moving parts, and zero pollutant emissions.

[0004] Tin selenide (SnSe) with an orthorhombic structure is a simple, green and environmentally friendly chalcogenide thermoelectric material system. Its twisted rock salt structure leads to strong anharmonicity of the Sn-Se bond, which gives it excellent thermoelectric properties. However, the high-temperature structural phase transition of the material itself directly affects the measurement, regulation and service of the material's high-temperature thermoelectric properties. Theoretical and experimental confirmation shows that tin selenide alloys have a highly symmetric cubic structure. Interestingly, cubic phase tin selenide also has strong anharmonicity. In addition, thanks to the high crystal structure symmetry and the relativistic effect of spin-orbit coupling, cubic tin selenide has obtained a higher band degeneracy, giving cubic tin selenide potential excellent thermoelectric properties.

[0005] The preparation of cubic tin selenide is primarily based on two strategies. The first involves the use of molecular beam epitaxy to produce cubic tin selenide thin films on substrates such as NaCl and Bi2Se3. The second involves the synthesis of cubic tin selenide single crystals using a solid solution alloying strategy. However, limited research on the intrinsic properties of cubic tin selenide has led to slow progress in studying its thermoelectric transport properties. Crystalline materials are an effective vehicle for studying the intrinsic properties of materials, so it is necessary to develop methods for preparing cubic tin selenide single crystals.

[0006] The technical document "Mao Lisha. Preparation of tin selenide crystals and their electrothermal transport properties [D]. University of Chinese Academy of Sciences (Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences), 2020." discloses a method for preparing layered SnSe single crystals, but does not involve the preparation of cubic phase tin selenide single crystals. The layered single crystal structure is easy to dissociate, the performance shows strong anisotropy, and the cost of sample preparation and cutting is high. There is also a high-temperature phase transition, which is not conducive to the precise measurement and regulation of high-temperature performance, and is not conducive to recycling. The Chinese patent "A tin selenide-based thermoelectric material, its preparation method and application" with application publication number "CN111710775A" discloses a method for preparing cubic phase tin selenide polycrystals, but it is significantly different from single crystal preparation. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a cubic tin selenide-based thermoelectric crystal and a preparation method thereof, and to obtain a cubic tin selenide-based single crystal based on a cooling crystallization method.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] In a first aspect, a method for preparing a cubic tin selenide-based thermoelectric crystal comprises the following steps:

[0010] S1. Weighing tin (Sn), silver (Ag), antimony (Sb), and selenium (Se) in a stoichiometric ratio and placing them into a first container, evacuating and sealing the first container;

[0011] S2, heating the first container to 953-1373K and keeping it warm for 15-30h, then cooling it to 773-923K and keeping it warm for 15-30h;

[0012] S3, taking out the alloy ingot from the first container, crushing it and placing it in a second container, evacuating and sealing the second container;

[0013] S4. Raise the temperature of the second container to 973-1373 K and keep it there for 5-30 hours, then cool it to 923-1173 K at a set first cooling rate, then cool it to 873-923 K at a set second cooling rate, and then cool it to room temperature at a set third cooling rate.

[0014] Optionally, in S1, the first container includes an outer first sealed tube and an inner first sealed tube placed therein, and the tin, silver, antimony and selenium elements are placed in the inner first sealed tube.

[0015] Optionally, in S1, the air pressure in the inner first sealed tube is lower than 1.0 Pa; and the air pressure in the gap between the outer first sealed tube and the inner first sealed tube is lower than 1.0 Pa.

[0016] Optionally, in S2, the heating rate is 0.5 to 10 K / min, and the cooling rate is 1 to 10 K / min.

[0017] Optionally, in S2, swing melting is performed during the insulation process between heating and cooling, with a swing rate of 10 to 200 times / min.

[0018] Optionally, in S2, after the cooling and heat preservation process is completed, cold water quenching or natural cooling is performed.

[0019] Optionally, in S3, the crushing method is to crush the alloy ingot into particles with a particle size of 0.5 to 8 mm.

[0020] Optionally, in S3, the second container includes an outer second sealed tube and an inner second sealed tube placed therein, and the particles of the alloy ingot are placed in the inner second sealed tube.

[0021] Optionally, in S3, the air pressure in the inner second sealed tube is lower than 1.0 Pa; the air pressure in the gap between the outer second sealed tube and the inner second sealed tube is lower than 1.0 Pa.

[0022] Optionally, in S4, the heating rate is 0.5 to 5 K / min, the first cooling rate is 0.01 to 0.05 K / min, the second cooling rate is 0.01 to 0.05 K / min, and the third cooling rate is 0.1 to 1.0 K / min.

[0023] In the second aspect, the cubic tin selenide-based thermoelectric crystal prepared by the above-mentioned preparation method is a cubic tin selenide-based single crystal with a chemical formula of Sn 1-2X (AgSb) X Se, 0.1≤X≤0.3.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The present invention prepares bulk cubic tin selenide single crystal materials through high-temperature swing melting and cooling crystallization methods, achieving extremely high grain orientation and uniform distribution of the four elements of tin, silver, antimony, and selenium, which is helpful for studying the intrinsic properties of the material. Compared with layered cubic tin selenide single crystal materials, the cubic phase single crystals prepared by the present invention do not have crystal structure phase transitions, making it easy to accurately control the performance of the sample; and the cubic structure has more stable mechanical properties than the layered structure and will not dissociate; compared with cubic phase polycrystals, the cubic phase single crystals prepared by the present invention have better electrical transport properties, thereby obtaining better comprehensive thermoelectric performance. In addition, the preparation of single crystal materials is more conducive to the study of the material's charge transport mechanism, eliminating the influence of grain boundaries on the material's electrical and thermal properties.

[0026] 2. The carrier concentration of the sample prepared by the present invention is 8.8×10 19 cm -3 ; The electrical conductivity is effectively improved: room temperature and high temperature can reach 200S cm -1 and 280S cm -1 ; The thermal conductivity at room temperature and high temperature is 0.75Wm -1 K -1 With 0.85Wm -1 K -1 The comprehensive thermoelectric figure of merit can reach 0.7 at 823K, making it a high-performance thermoelectric material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 This is a schematic diagram of the second container in Example 1.

[0029] Figure 2 This is the X-ray diffraction detection spectrum of the sample block in Example 1.

[0030] Figure 3 This is the X-ray diffraction detection spectrum of the sample powder in Example 1.

[0031] Figure 4 This is a scanning electron microscope morphology image of the sample block in Example 1.

[0032] Figure 5 These are the electron backscatter diffraction element distribution diagrams of the sample block in Example 1, (a) is the Sn element distribution diagram, (b) is the Ag element distribution diagram, (c) is the Sb element distribution diagram, and (d) is the Se element distribution diagram.

[0033] Figure 6 This is a curve diagram showing the change in conductivity of the sample block in Example 1 with temperature.

[0034] Figure 7 This is a graph showing the Seebeck coefficient of the sample block in Example 1 changing with temperature.

[0035] Figure 8 This is a curve diagram showing the change of thermal conductivity of the sample block in Example 1 with temperature.

[0036] Figure 9 This is a graph showing the change in thermoelectric figure of merit of the sample block in Example 1 with temperature.

[0037] Among them, 1. pointed bottom cylindrical sample; 2. inner second sealing tube; 3. outer second sealing tube; 4. quartz glass plug. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] A method for preparing a cubic tin selenide-based thermoelectric crystal, comprising the following steps:

[0041] S1. Weigh tin, silver, antimony, and selenium according to the stoichiometric ratio and place them into a first container, evacuate the container, and seal the first container;

[0042] S2. Raise the temperature of the first container and its contents to 953-1373 K and keep it at this temperature for 15-30 hours, then lower the temperature to 773-923 K and keep it at this temperature for 15-30 hours, and then cool it to room temperature;

[0043] S3, taking out the alloy ingot from the first container, crushing it and placing it in a second container, evacuating and sealing the second container;

[0044] S4. Raise the temperature of the second container and its contents to 973-1373 K and keep it at this temperature for 5-30 h, then cool it to 923-1173 K at a first cooling rate, then cool it to 873-923 K at a second cooling rate, and then cool it to room temperature at a third cooling rate.

[0045] In the above process, cubic tin selenide-based single crystals are synthesized by using the alloy solid solution strategy, and silver and antimony are used to promote the formation of cubic tin selenide. In S4, a multi-stage slow cooling method is used to prepare cubic tin selenide-based single crystals.

[0046] Optionally, in S1, the first container includes an outer first sealed tube and an inner first sealed tube placed therein, and the tin, silver, antimony and selenium elements are placed in the inner first sealed tube; the inner first sealed tube is a quartz glass tube, and the outer first sealed tube is a larger quartz glass tube.

[0047] Optionally, in S1, the air pressure in the inner first sealed tube is lower than 1.0 Pa; the air pressure in the gap between the outer first sealed tube and the inner first sealed tube is lower than 1.0 Pa; during preparation, after the inner first sealed tube is evacuated, the quartz glass tube is heated with a flame, and the heating position is rotated along the axial direction until the quartz glass tube is sealed, and then the inner first sealed tube is placed in the outer first sealed tube, and a quartz glass plug for sealing is placed, the above vacuum operation is repeated, and sealing is performed according to the same method, and the flame heating position is located at the quartz glass plug.

[0048] Optionally, in S2, the heating rate is 0.5 to 10 K / min and the cooling rate is 1 to 10 K / min, so that the components are fully and evenly diffused and the container is prevented from bursting.

[0049] Optionally, in S2, swing melting is performed during the insulation process between heating and cooling. Under the same temperature and time conditions, swinging can make the sample mixing and reaction more complete. The swinging rate is 10 to 200 times / min. The equipment used for swing melting is a high-temperature swing furnace, which is a common equipment for promoting uniform dispersion of various components.

[0050] Optionally, in S2, cold water quenching or natural cooling is performed after the cooling and holding process is completed. Water quenching can shorten the preparation cycle.

[0051] Optionally, in S3, the crushing method is to crush the alloy ingot into particles with a particle size of 0.5 to 8 mm. The particle size needs to be compatible with the diameter of the inner second sealing tube, which is helpful for subsequent preparation of crystal materials.

[0052] Optionally, in S3, the second container includes an outer second sealed tube and an inner second sealed tube placed therein, the particles of the alloy ingot are placed in the inner second sealed tube, the inner second sealed tube is a quartz glass tube with a pointed bottom, and the outer second sealed tube is a quartz glass tube with a larger size.

[0053] Optionally, in S3, the air pressure in the inner second sealed tube is lower than 10.0 Pa; the air pressure in the gap between the outer second sealed tube and the inner second sealed tube is lower than 10.0 Pa, and the preparation method is the same as the vacuuming and sealing method in S1.

[0054] Optionally, in S4, the heating rate is 0.5 to 5 K / min; the first cooling rate is 0.01 to 0.05 K / min, the second cooling rate is 0.01 to 0.05 K / min, and the third cooling rate is 0.1 to 1.0 K / min, so as to obtain high-quality crystals.

[0055] Optionally, in S4, the second container is kept in a vertical position, and the equipment is a high-temperature annealing furnace or a suspension zone melting furnace, so that the internal components are crystallized in a stable equilibrium state to obtain a cubic tin selenide-based thermoelectric crystal product.

[0056] The cubic tin selenide-based thermoelectric crystal prepared by the above-mentioned preparation method is a cubic tin selenide-based single crystal with a chemical formula of Sn 1-2X (AgSb) X Se, 0.1≤X≤0.3.

[0057] Example 1

[0058] A cubic tin selenide-based thermoelectric crystal with the chemical formula Sn 0.5 (AgSb) 0.25 Se, the preparation method includes the following steps.

[0059] S1. According to the stoichiometric ratio, 15.16310000g of tin, 6.88910000g of silver, 7.77635000g of antimony, and 20.17145000g of selenium with a purity of 99.999% were weighed respectively and placed in a quartz glass tube with a diameter of 12.7 mm (i.e., the first inner sealed tube). The vacuum pump connected to the first inner sealed tube was turned on to evacuate the tube for 10 minutes and ensure that the air pressure in the tube was less than 10.0 Pa. Then, a molecular pump connected to the first inner sealed tube was turned on to further evacuate the tube for 10 minutes until the air pressure in the tube was less than 1.0 Pa. Pa below; then, heating with an acetylene flame and rotating the inner first sealed tube in the axial direction until the inner first sealed tube is sealed; placing the inner first sealed tube in a quartz glass tube with a diameter of 20 mm (i.e., the outer first sealed tube), and inserting a quartz glass stopper, repeating the above vacuuming operation until the air pressure in the tube is below 1.0 Pa, heating the quartz glass stopper position with an acetylene flame, and rotating the outer first sealed tube in the axial direction until the outer first sealed tube is sealed, thereby obtaining a first container sealed with the preparation raw materials.

[0060] S2. Place the first container obtained in S1 vertically in a high-temperature rocking furnace for melting operation. The process conditions of the melting operation are set as follows: first, slowly heat up to 1273K at a rate of 5K / min, then turn on the rocking switch, and keep it in this temperature zone for 20 hours, rocking at a rate of 50 times / min; after the rocking is completed, turn off the rocking switch; then cool it down to 873K at a rate of 5K / min, and keep it at this temperature for 20 hours, and cool it naturally after the insulation process is completed.

[0061] S3, the molten alloy ingot is taken out from the first container, crushed and ground in a mortar to obtain uniform particles with a particle size of less than 5 mm, 45 g of the particles are loaded into a sharp bottom quartz glass tube with a diameter of 15 mm (i.e. the inner layer second sealing tube), and then the inner layer second sealing tube is sealed by using an acetylene flame after being vacuumized to an air pressure lower than 1.0 Pa in the tube by using a vacuum pump and a molecular pump in sequence according to the method of S1, then the inner layer second sealing tube is placed in a quartz glass tube with a diameter of 20 mm (i.e. the outer layer second sealing tube), the above vacuumizing operation is repeated, and then the outer layer second sealing tube is sealed by using an acetylene flame to heat the position of the quartz glass plug and rotate the outer layer second sealing tube along the axial direction until the outer layer second sealing tube is sealed, thereby obtaining the second container with the alloy ingot particles sealed therein.

[0062] S4, the second container is vertically placed in a high-temperature annealing furnace, first heated to 1223 K at a rate of 2 K / min and kept for 10 h, then cooled to 1073 K at a rate of 0.015 K / min, then cooled to 973 K at a rate of 0.02 K / min, and then cooled to room temperature at a rate of 0.5 K / min, at this time, the second container is as shown in Figure 1 , the sharp bottom cylindrical sample 1 is still sealed in the inner layer second sealing tube 2, the inner layer second sealing tube 2 is still sealed in the outer layer second sealing tube 3, the quartz glass plug 4 is plugged in the tube opening of the outer layer second sealing tube 3 and maintains a state of being fused with the outer layer second sealing tube 3 to maintain sealing, and the second container is opened to obtain a sharp bottom cylindrical sample with a diameter of 15 mm.

[0063] Example 2

[0064] A cubic tin selenide-based thermoelectric crystal, the chemical formula of which is Sn 0.4 (AgSb) 0.3 Se, the difference between the preparation method and Example 1 is that:

[0065] In S1, tin with a purity of 99.999% is weighed at 12.15465000 g, silver is weighed at 8.9.35020000 g, antimony is weighed at 9.35020000 g, and selenium is weighed at 20.21170000 g according to the stoichiometric ratio.

[0066] In S2, the temperature is raised to 1373 K at a rate of 10 K / min and kept for 15 h, then the temperature is lowered to 923 K at a rate of 10 K / min and kept for 15 h, and then water cooling is performed to room temperature.

[0067] In S4, the temperature was first raised to 1373 K at a rate of 5 K / min and kept for 5 h, then cooled to 1173 K at a rate of 0.05 K / min, then cooled to 923 K at a rate of 0.03 K / min, and then cooled to room temperature at a rate of 1.0 K / min. The second container was opened to obtain a pointed-bottom cylindrical sample with a diameter of 15 mm.

[0068] Example 3

[0069] A cubic tin selenide-based thermoelectric crystal with the chemical formula Sn 0.4 (AgSb) 0.3 Se, the preparation method is different from that of Example 1 in that:

[0070] In S1, 12.15465000 g of tin with a purity of 99.999%, 8.935020000 g of silver, 9.35020000 g of antimony, and 20.21170000 g of selenium with a purity of 99.999% were weighed respectively according to the stoichiometric ratio.

[0071] In S2, the temperature was raised to 953 K at a rate of 0.5 K / min and kept at this temperature for 30 h, then cooled to 773 K at a rate of 1 K / min and kept at this temperature for 15 h, and then water-cooled to room temperature.

[0072] In S4, the temperature was first raised to 973 K at a rate of 0.5 K / min and kept for 30 h, then cooled to 923 K at a rate of 0.03 K / min, then cooled to 873 K at a rate of 0.01 K / min, and then cooled to room temperature at a rate of 0.1 K / min. The second container was opened to obtain a pointed-bottom cylindrical sample with a diameter of 15 mm.

[0073] Comparative Example 1

[0074] A cubic tin selenide-based thermoelectric crystal, the chemical formula of which is Sn0.5(AgSb)0.25Se, is prepared in the following manner:

[0075] In S1, the double-tube method is not used. After the sample is swing-melted, the quartz glass tube may break during the cooling process, which may cause the sample to oxidize due to contact with air, resulting in subsequent experimental failure or damage to material properties.

[0076] Comparative Example 2

[0077] A cubic tin selenide-based thermoelectric crystal, the chemical formula of which is Sn0.5(AgSb)0.25Se, is prepared in the following manner:

[0078] In S2, after the end of the holding swing, the swing switch is closed; then the temperature is decreased to 873 K at a rate of 5 K / min, and then directly naturally cooled. In this case, the sample element distribution is uneven. Ultimately, the single crystal sample cannot be synthesized.

[0079] Comparative Example 3

[0080] A cubic tin selenide-based thermoelectric crystal, chemical formula Sn0.5(AgSb)0.25Se, the preparation method is different from that of Example 1 in that:

[0081] In S4, the second container is vertically placed in the high-temperature annealing furnace, first heated to 1223 K at a rate of 2 K / min and held for 10 h, then cooled to 973 K at a rate of 0.02 K / min, and then cooled to room temperature at a rate of 0.5 K / min. Too fast cooling rate leads to sample breakage.

[0082] Comparative Example 4

[0083] A cubic tin selenide-based thermoelectric crystal, chemical formula Sn 0.5 (AgSb) 0.25 Se, the preparation method is different from that of Example 1 in that:

[0084] In S4, after the end of the holding, the temperature is decreased to 1073 K at a rate of 0.1 K / min, then decreased to 973 K at a rate of 0.2 K / min, and then decreased to room temperature at a rate of 1.5 K / min. Too fast cooling rate also leads to sample breakage.

[0085] Detection content

[0086] The performance of thermoelectric materials is characterized by a dimensionless parameter (thermoelectric figure of merit, zT): zT = σS 2 T / κ.

[0087] In the right side of the formula, σ, S, T and κ are electrical conductivity, Seebeck coefficient, absolute temperature and thermal conductivity, respectively, and σS 2 is defined as the power factor (PF);

[0088] κ = κ e + κ l + κ b , that is, the total thermal conductivity is the sum of the electronic thermal conductivity (κ e ), the lattice thermal conductivity (κ l ) and the bipolar thermal conductivity (κ b ).

[0089] From the expression of zT, high performance thermoelectric materials need to have excellent electrical conductivity, Seebeck coefficient and low thermal conductivity.

[0090] X-ray diffraction detection was performed on the sample block obtained in Example 1, and the pattern is shown in Figure 2 X-ray diffraction detection was performed on the sample block obtained in Example 1, and the pattern is shown in Figure 3 It can be seen that the block prepared in Example 1 has extremely high grain orientation degree, and there is only one diffraction peak, indicating that the entire block has only one crystal phase, reflecting that the sample prepared in Example 1 is a single-oriented bulk single crystal material, which is different from the layered single crystal and cubic phase tin selenide polycrystal in the background art.

[0091] The scanning electron microscope morphology of the sample block obtained in Example 1 is shown in Figure 4 The electron backscatter diffraction element distribution map under the same field of view is shown in Figure 5 Figure 5 (a) is the Sn element distribution map, Figure 5 (b) is the Ag element distribution map, Figure 5 (c) is the Sb element distribution map, Figure 5 (d) is the Se element distribution map, it can be seen that the four elements are uniformly distributed.

[0092] The curve of the electrical conductivity of the sample block obtained in Example 1 with temperature change is shown in Figure 6 At the near room temperature end, the electrical conductivity gradually decreases with the increase of temperature; then, the electrical conductivity of the sample increases with the increase of temperature, showing a semiconductor transport behavior; the maximum value of the electrical conductivity is about 290 S cm -1 at 823 K. The curve of the Seebeck coefficient with temperature change is shown in Figure 7 Unlike the trend of the electrical conductivity with temperature change, the Seebeck coefficient gradually increases with the increase of temperature. The curve of the thermal conductivity with temperature change is shown in Figure 8 With the increase of temperature, the thermal conductivity of the sample first decreases and then increases, and the lowest thermal conductivity value of about 0.69 W m -1 K -1 The curve of the thermoelectric figure of merit of the sample block of Example 1 obtained above with temperature change is shown in Figure 9 The sample finally obtains the maximum thermoelectric figure of merit of about 0.7 at 823 K.

[0093] The carrier concentration of the sample block in Example 1 is 8.8 x 10 19 cm -3 at room temperature.

[0094] ​Correspondingly, the sample of Comparative Example 1 is detected, and the performance thereof is poor or complete single crystal material cannot be obtained.

[0095] Compared with the layered SnSe single crystal in the background art, the performance advantage of the present application is embodied in: having more beneficial electrical transport performance.

[0096] Compared with the cubic phase tin selenide polycrystal in the background art, the advantage of the present application is embodied in: higher electrical conductivity at the near room temperature end.

[0097] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a cubic tin selenide-based thermoelectric crystal, characterized in that the steps include: S1. Weigh tin, silver, antimony, and selenium according to a stoichiometric ratio and place them into a first container. Evacuate and seal the first container. The first container includes an outer first sealed tube and an inner first sealed tube placed therein. The tin, silver, antimony, and selenium are placed in the inner first sealed tube. The inner first sealed tube is a quartz glass tube, and the outer first sealed tube is a quartz glass tube. S2, heating the first container to 953-1373 K and holding the temperature for 15-30 h, then cooling the container to 773-923 K and holding the temperature for 15-30 h; in S2, the heating rate is 0.5-10 K / min, and the cooling rate is 1-10 K / min; in S2, swing melting is performed during the holding period between heating and cooling; S3, taking out the alloy ingot from the first container, crushing it and placing it in a second container, evacuating and sealing the second container; S4. Raise the temperature of the second container to 973-1373 K and keep it there for 5-30 hours, then cool it to 923-1173 K at a first cooling rate, then cool it to 873-923 K at a second cooling rate, and then cool it to room temperature at a third cooling rate; in S4, the heating rate is 0.5-5 K / min; the first cooling rate is 0.01-0.05 K / min, the second cooling rate is 0.01-0.05 K / min, and the third cooling rate is 0.1-1.0 K / min.

2. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 1, wherein: The air pressure in the inner first sealed tube is lower than 1.0 Pa; the air pressure in the gap between the outer first sealed tube and the inner first sealed tube is lower than 1.0 Pa.

3. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 1, wherein: In S2, the swing rate is 10~200 times / min.

4. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 1, wherein: In S2, after the cooling and holding process is completed, cold water quenching or natural cooling is performed.

5. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 1, wherein: In S3, the crushing method is to crush the alloy ingot into particles with a particle size of 0.5-8 mm.

6. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 1, wherein: The second container includes an outer second sealed tube and an inner second sealed tube placed therein, and particles of the alloy ingot are placed in the inner second sealed tube.

7. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 6, wherein: The inner second sealed tube is a quartz glass tube with a pointed bottom, and the outer second sealed tube is a quartz glass tube.

8. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 7, wherein: The air pressure in the inner second sealed tube is lower than 1.0 Pa; the air pressure in the gap between the outer second sealed tube and the inner second sealed tube is lower than 1.0 Pa.

9. The method for preparing a cubic tin selenide-based thermoelectric crystal according to claim 1, wherein: In S4, the second container is kept in a vertical position, and the equipment is a high-temperature annealing furnace or a suspension zone melting furnace.

10. The cubic tin selenide-based thermoelectric crystal prepared by the method for preparing a cubic tin selenide-based thermoelectric crystal according to any one of claims 1 to 9, characterized in that: It is a cubic tin selenide-based single crystal with the chemical formula Sn 1-2X (AgSb) X Se, 0.1≤X≤0.3.

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