A method for rapidly preparing SnSe crystals

Abstract

This invention discloses a rapid method for preparing SnSe crystals, shortening the crystal growth cycle from 260 hours to 52 hours. Compared to the traditional vertical gradient multi-temperature zone cooling method, this method overcomes the difficulty of heat dissipation in the central region during SnSe crystal growth by inserting a graphite rod at the center of the melt to achieve heat dissipation and balance the internal temperature zones. This allows for the successful growth of large SnSe single crystals in a shorter time while maintaining excellent thermoelectric properties. Specifically, the method involves first preparing a mixture according to stoichiometric proportions; then placing the mixture in a quartz tube and fixing a carbon rod at the center, followed by vacuum treatment; finally, placing the quartz tube in a dual-temperature zone vertical tube furnace to react and obtain the corresponding crystals. This invention shortens the crystal preparation time, improves production efficiency, and is applicable to mass production.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, specifically to a method for rapidly preparing SnSe crystals. Background Technology

[0002] Thermoelectric materials, relying directly on the transport of internal charge carriers, can directly convert heat energy into electrical energy, thus building a conversion bridge between electrical and thermal energy and demonstrating enormous application potential in clean energy production and refrigeration technology. Thermoelectric devices, constructed from multiple pairs of P-type and N-type thermoelectric arms, are widely used in various fields such as communication equipment, industrial production, medical and health care, and aerospace due to their compact size, quiet operation, low power consumption, and long service life.

[0003] SnSe (tin selenide) is a group IV-VI semiconductor crystal with a layered structure, belonging to the orthorhombic crystal system (Pnma space group). SnSe is renowned for its excellent thermoelectric properties, making it a potential high-efficiency thermoelectric material. This characteristic stems from its low thermal conductivity and moderate electrical conductivity. Due to SnSe's excellent electrical transport properties and intrinsically low thermal conductivity, doping with SnSe can yield corresponding P-type and N-type materials with high thermoelectric properties, which can then be used to fabricate excellent power generation or cooling devices.

[0004] To realize the numerous applications of SnSe crystals in the new energy field, the primary problem to be solved is crystal preparation. Researchers have successfully obtained high-quality SnSe crystals based on a modified Bridgman method (temperature gradient method). However, this method suffers from excessively long preparation time and small crystal size per batch, which undoubtedly hinders the industrialization of SnSe crystals from the laboratory. Therefore, shortening the crystal growth preparation cycle and increasing the crystal size per batch have become urgent technical problems to be solved. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a method for rapidly preparing SnSe crystals. This method seeks to solve the problem of long SnSe crystal growth cycles, thereby enabling better large-scale crystal production.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A method for rapidly preparing SnSe crystals is provided, comprising the following steps:

[0008] (1) Sn, Se, Mo and SnBr2 are mixed in their stoichiometric ratios to obtain a mixture;

[0009] (2) Place the mixture obtained in step (1) into a quartz tube;

[0010] (3) Place the graphite assembly in the quartz tube of step (2) and vacuum the quartz tube.

[0011] (4) Place the quartz tube from step (3) in a tube furnace to carry out the synthesis reaction and obtain SnSe crystals.

[0012] Furthermore, in step (1), the mass purity of Sn and Se is independently greater than 99.999%, and the mass purity of Mo and SnBr2 is greater than 99%.

[0013] Furthermore, the quartz tube in step (2) is a pointed conical quartz tube with a diameter of 17-20 mm, a wall thickness of 1-1.5 mm, and a bottom conical angle θ ranging from 15° to θ / 2 to 25°.

[0014] Furthermore, the graphite assembly in step (3) consists of a graphite retainer and a graphite rod.

[0015] Furthermore, the graphite fixing plug is a cylinder with a hollowed-out bottom center. The diameter D of the cylinder ranges from 15.5mm to 16.5mm, and the height L ranges from 9.5mm to 10.5mm. The hollowed-out area at the bottom is also cylindrical, with a diameter d ranging from 3.8mm to 4.2mm and a height l ranging from 7.5mm to 8.5mm.

[0016] Furthermore, the diameter r of the graphite rod ranges from 3.8 mm to 4.2 mm, and the length L ranges from 95 mm to 105 mm.

[0017] Furthermore, in step (3), the graphite assembly is placed in the quartz tube, and the distance between the bottom of the graphite rod and the bottom of the quartz tube is in the range of 20-30 mm.

[0018] Furthermore, the vacuuming process performed in step (3) must have a vacuum level less than or equal to 1 x 10⁻⁶. -3 Pa.

[0019] Furthermore, the specific temperature program for the synthesis reaction in the tubular furnace in step (4) is as follows: the tubular furnace is heated to 1040℃ in 8 hours, held at 1040℃ for 2 hours, then the tubular furnace is cooled to 900℃ at a rate of 1℃ / min, then cooled to 820℃ at a rate of 2℃ / h, and finally cooled to room temperature with the furnace.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention introduces graphite-assisted heat conduction to rapidly conduct excess heat from the center of the melt along the graphite rod during the cooling stage, thereby balancing the internal temperature of the melt. This overcomes the difficulty of heat dissipation in the central region during SnSe crystal growth, enabling the successful growth of large SnSe single crystals in a short time while maintaining excellent thermoelectric properties. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the improved crystal growth method used in this invention, in which a mixture with a graphite rod inserted in the center is synthesized at high temperature in a pointed tube.

[0023] Figure 2 A photograph of a large-sized N-type SnSe crystal, 2cm x 4.5cm, with a graphite rod attached to its tip.

[0024] Figure 3 The power factor (PF) of the SnSe crystal provided in Examples 1 to 4 of this invention is a test result data curve of temperature change.

[0025] Figure 4 The graphs show the test results of the ZT value of SnSe crystals as a function of temperature provided in Examples 1-4 of this invention.

[0026] Figure 5 The power factor (PF) of the N-type SnSe crystals provided in Comparative Examples 1-4 of this invention is a test result curve showing the change of power factor (PF) with temperature.

[0027] Figure 6 The graphs show the test results of the ZT value of the N-type SnSe crystals provided in Comparative Examples 1 to 4 of this invention as a function of temperature. Detailed Implementation

[0028] This invention provides a method for rapidly preparing SnSe crystals, comprising the following steps:

[0029] (1) Prepare the mixture according to its stoichiometric ratio.

[0030] (2) Place the mixture from step (1) into a quartz tube.

[0031] (3) Place the graphite assembly in the quartz tube from step (2) and evacuate the quartz tube.

[0032] (4) Place the quartz tube from step (3) in a vertical tube furnace to carry out the synthesis reaction and obtain SnSe crystals.

[0033] This invention involves mixing Sn, Se, Mo, and SnBr2 in their stoichiometric ratios to obtain a mixture. In this invention, the mass purity of Sn and Se is independently greater than 99.99%, and the mass purity of Mo and SnBr2 is greater than 99%.

[0034] In specific embodiments of the method of the present invention, in order to prevent oxidation or deliquescence of the raw materials and the resulting compound, the weighing and mixing processes of the raw materials are carried out under an inert atmosphere. The present invention does not particularly limit the type of inert atmosphere; common inert gases in the art can be used, such as nitrogen (N2), argon (Ar), and helium (He).

[0035] The obtained mixture is placed in a quartz tube, and a graphite assembly is inserted into the center, followed by vacuum treatment. In this invention, the tip of the quartz tube is specifically conical, the tube diameter is preferably about 17-20 mm, and the wall thickness is preferably about 1-1.5 mm. In this invention, the graphite assembly consists of a graphite plug and a graphite rod. Preferably, the graphite plug is a cylinder with a hollowed-out bottom center (diameter D ranges from 15.5 mm to 16.5 mm, height L ranges from 9.5 mm to 10.5 mm), and the hollowed-out area at the bottom is also cylindrical (diameter d ranges from 3.8 mm to 4.2 mm, height l ranges from 7.5 mm to 8.5 mm). The graphite rod has a diameter r range of 3.8 mm to 4.2 mm and a length L range of 95 mm to 105 mm. One end of the graphite rod is ground with a carving tool and then inserted into the opening at the bottom of the graphite plug while rotating. The assembled graphite assembly is placed in a quartz tube with the bottom of the graphite rod relative to the bottom of the quartz tube ranging from 20 to 30 mm. Preferably, the quartz tube wall next to the graphite retainer is burned with a flame torch, causing it to indent inward and firmly securing the graphite assembly in the center of the tube.

[0036] In a specific embodiment of the method of the present invention, the vacuuming process specifically involves using a vacuum pump to evacuate the inside of the quartz tube to a vacuum level of less than 10. -3 Pa, then the nozzle is sealed with a flame gun, which can effectively prevent the raw materials from oxidizing during single crystal growth.

[0037] After vacuuming, in a specific embodiment of the method of the present invention, a quartz tube containing the mixture and graphite components is placed in a tube furnace for the synthesis reaction. Specifically, in a specific embodiment of the method of the present invention, the tip of the quartz tube is preferably slightly higher than the heating wire at the bottom of the furnace cavity, and the top of the quartz tube is specifically located at the horizontal position of the thermocouple in the central area. Before heating the furnace cavity, it is preferable to vacuum the dual-temperature zone vertical tube furnace body until the furnace body vacuum degree is lower than 10. -1 Pa, thereby avoiding the adverse effects on the stability of the overall temperature range distribution of the furnace cavity caused by gas convection during furnace cavity heating.

[0038] In a specific embodiment of the method of the present invention, the temperature control program of the upper temperature zone of the dual-temperature zone vertical tube furnace is as follows: the temperature is raised to 1040°C in 8 hours, and held at this temperature for 2 hours. Then, the temperature is lowered to 900°C at a rate of 1°C / min, and then lowered to 820°C at a rate of 2°C / h. Finally, the temperature is cooled to room temperature along with the furnace.

[0039] The present invention provides the above-mentioned technical solution, which prepares SnSe single crystals in a shorter time.

[0040] The following detailed description of the rapid SnSe crystal preparation method provided by this invention, with reference to specific implementation examples, should not be construed as limiting the scope of protection of this invention.

[0041] Example 1

[0042] (1) Prepare the mixture by mixing the ingredients according to the stoichiometric ratio of Sn:Se:Mo:Br = 0.998:0.97:0.002:0.03;

[0043] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0044] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0045] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0046] Example 2

[0047] (1) Prepare the mixture according to the stoichiometric ratio of Sn:Se:Mo:Br = 0.998:0.96:0.002:0.04;

[0048] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0049] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3Pa, followed by flame gun sealing treatment;

[0050] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0051] Example 3

[0052] (1) Prepare the mixture by mixing the ingredients according to the stoichiometric ratio of Sn:Se:Mo:Br = 0.998:0.95:0.002:0.05;

[0053] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0054] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0055] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0056] Example 4

[0057] (1) Prepare the mixture by mixing the ingredients according to the stoichiometric ratio of Sn:Se:Mo:Br = 0.998:0.94:0.002:0.06;

[0058] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0059] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0060] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0061] Reference Example

[0062] (1) Prepare the mixture by mixing the ingredients according to the stoichiometric ratio of Sn:Se:Br = 1:0.97:0.03;

[0063] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm);

[0064] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0065] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 10 hours, keep at 1040℃ for 10 hours, cool down to 800℃ at a cooling rate of 1℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0066] Table 1: Thermoelectric properties of SnSe crystals with different Br compositions

[0067]

[0068] Table 1 shows the performance values ​​of a series of SnSe crystals prepared by this process. It can be seen that the material is transformed into an N-type semiconductor after being doped with a certain amount of Br. Figure 3 The solid lines show the test results of the power factor (PF) of SnSe crystals in Examples 1-4 as a function of temperature, while the dashed lines represent the power factor (PF) of the corresponding N-type crystals grown using the reference example (conventional growth) method (260 hours). It can be seen that the power factor of the crystals obtained by rapid growth in the embodiments of this application is similar to that of those grown by conventional methods, and both yield N-type crystals with high electrical performance. Figure 4The solid lines show the test results of the ZT value of SnSe crystals in Examples 1-4 as a function of temperature, while the dashed lines represent the ZT values ​​of the corresponding N-type crystals grown using conventional crystal growth methods (taking 260 hours). It can also be seen that the crystals obtained under rapid growth in the embodiments of this application still maintain their original excellent thermoelectric properties.

[0069] Comparative Example 1

[0070] (1) Prepare the mixture by mixing the ingredients according to the stoichiometric ratio of Sn:Se:Mo:Br = 0.998:0.97:0.002:0.03;

[0071] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0072] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0073] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0074] Comparative Example 2

[0075] (1) Prepare the mixture according to the stoichiometric ratio of Sn:Se:Mo:Br:Ge = 0.997:0.97:0.002:0.03:0.001;

[0076] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0077] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0078] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0079] Comparative Example 3

[0080] (1) Prepare the mixture according to the stoichiometric ratio of Sn:Se:Mo:Br:Ge = 0.996:0.97:0.002:0.03:0.002;

[0081] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0082] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0083] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0084] Comparative Example 4

[0085] (1) Prepare the mixture according to the stoichiometric ratio of Sn:Se:Mo:Br:Ge = 0.995:0.97:0.002:0.03:0.003;

[0086] (2) Place the mixture from step (1) into a quartz tube with a pointed bottom (outer diameter ~17mm, tube wall thickness ~1.5mm), assemble the graphite assembly, and insert it into the middle of the quartz tube;

[0087] (3) Evacuate the quartz tube from step (2) until the vacuum level is less than 10. -3 Pa, followed by flame gun sealing treatment;

[0088] (4) Place the sealed quartz tube obtained in step (3) into the tube furnace, so that the bottom tip is slightly higher than the bottom heating wire of the furnace cavity, and the top is specifically located at the horizontal position of the thermocouple in the central area; then set the temperature control program of the tube furnace: heat up to 1040℃ in 8 hours, hold at 1040℃ for 2 hours, cool down to 900℃ at a cooling rate of 1℃ / min, cool down to 820℃ at a cooling rate of 2℃ / h, and finally end the program and cool down to room temperature with the furnace.

[0089] Table 2: Thermoelectric properties of SnSe crystals with different Ge compositions under 3% Br composition

[0090]

[0091]

[0092] Table 3: Crystal size and growth time for all embodiments, comparative examples and reference examples.

[0093]

[0094] In summary, based on the above embodiments, comparative examples, and reference examples, the rapid growth process proposed in this application can significantly shorten the time cost of crystal growth (from the original 260h to 52h) while ensuring the thermoelectric performance of the crystal, which will lay the foundation for the subsequent mass growth of crystals.

[0095] In summary, this invention proposes a novel process for SnSe crystal growth by inserting a graphite rod into the center of the melt to assist in heat conduction. On one hand, during the initial cooling stage of the melt, the extremely high thermal conductivity of graphite allows a large amount of heat from the melt center (highest temperature) to be conducted along the rod during rapid cooling, resulting in a uniform temperature distribution within the melt. On the other hand, during the crystal growth stage, the graphite rod, acting as the high-temperature end, reduces the number of spontaneous nuclei within the melt, promoting the formation of a single nucleation site to grow into a single crystal. This shortens the traditional crystal growth cycle from 260 hours to 52 hours. As shown in Table 3, under the corresponding compositions in all embodiments and comparative examples, centimeter-sized dense, high-quality crystals were successfully grown. Furthermore, because graphite is economical and the improved crystal growth apparatus has a simple structure, it is expected to achieve low-cost, high-efficiency, and high-batch growth of SnSe crystals.

[0096] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0097] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for rapidly preparing SnSe crystals, characterized in that, Includes the following steps: (1) Sn, Se, Mo and SnBr2 are mixed in a stoichiometric ratio of Sn:Se:Mo:Br = 0.998:(0.94~0.97):0.002:(0.03~0.06) to obtain a mixture; (2) Place the mixture obtained in step (1) into a conical quartz tube; (3) Place the graphite assembly in the conical quartz tube of step (2) and vacuum the quartz tube; (4) Place the conical quartz tube from step (3) in a tube furnace to carry out the synthesis reaction and obtain SnSe crystals; In step (3), the graphite assembly includes a graphite plug and a graphite rod. The graphite plug is a cylinder with a hollowed-out bottom center. One end of the graphite rod is inserted into the hollowed-out cylindrical area at the bottom center of the graphite plug, and the other end of the graphite rod is inserted into the mixture at the bottom of the conical quartz tube to conduct heat to the material.

2. The method for rapid preparation of SnSe crystals as described in claim 1, characterized in that, In step (1), the mass purity of Sn and Se is independently greater than 99.999%, and the mass purity of Mo and SnBr2 is greater than 99%.

3. The method for rapid preparation of SnSe crystals as described in claim 1, characterized in that, In step (2), the diameter of the conical quartz tube is 17~20 mm, the wall thickness is 1~1.5 mm, and the bottom is conical at an angle of... θ The range is 15°≤ θ / 2≤25°.

4. The method for rapid preparation of SnSe crystals as described in claim 1, characterized in that, diameter of cylinder D The range is 15.5 mm ≤ D ≤16.5 mm, height of the cylinder L The range is 9.5 mm ≤ L ≤10.5 mm, the bottom hollow area is also cylindrical, its diameter d The range is 3.8 mm≤ d ≤4.2 mm, height l The range is 7.5 mm ≤ l ≤8.5 mm.

5. The method for rapid preparation of SnSe crystals as described in claim 1, characterized in that, Diameter of graphite straight rod r The range is 3.8 mm≤ r ≤4.2 mm, length L The range is 95 mm≤ L ≤105 mm.

6. The method for rapid preparation of SnSe crystals as described in claim 1, characterized in that, In step (3), the distance between the bottom of the graphite rod and the bottom of the quartz tube is 20~30 mm.

7. The method for rapid preparation of SnSe crystals as described in claim 1, characterized in that, The vacuum process performed in step (3) must have a vacuum level less than or equal to 1 x 10⁻⁶. -3 Pa.

8. The method for rapid preparation of SnSe crystals as described in claim 1, characterized in that, The specific temperature program for the synthesis reaction in the tubular furnace in step (4) is as follows: the tubular furnace is heated to 1040℃ in 8 hours, held at 1040℃ for 2 hours, then the tubular furnace is cooled to 900℃ at a rate of 1℃ / min, then cooled to 820℃ at a rate of 2℃ / h, and finally cooled to room temperature with the furnace.

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