Method for synthesizing Te crystal at high temperature and high pressure

Abstract

The invention discloses a method for synthesizing Te crystals at high temperature and high pressure, and belongs to the technical field of Te crystal synthesis, and the method comprises the following steps: taking Te powder as an initial raw material, and carrying out high-temperature and high-pressure reaction in a sealed environment: raising the pressure to 4.8-5.2 Gpa, then raising the temperature to 570-610 DEG C, carrying out heat preservation and pressure preservation for 25-35 minutes, then quenching, and after the reaction is finished, rapidly cooling to obtain Te crystals; and slowly releasing the pressure to obtain the Te crystal. According to the method, the high-quality and large-size Te crystal is synthesized, a problem in the technical field of material synthesis and preparation at present is solved, and a guarantee is provided for experimental research of the Te crystal. Part of defects of high-quality Te crystal growth at high temperature and high pressure are overcome, and the adopted growth mode can effectively reduce negative effects of Te volatility on crystal growth and does not introduce new impurities.

Description

Technical Field

[0001] The present invention belongs to the technical field of Te crystal synthesis, and particularly relates to a method for synthesizing Te crystals under high temperature and high pressure. Background Art

[0002] Te crystal, namely tellurium crystal, is a crystal material composed of tellurium element. The synthesis methods of Te crystals mainly include chemical vapor deposition, hydrothermal method, physical vapor deposition, solution synthesis method, solution synthesis method, solution synthesis method, and van der Waals epitaxy method. Among them, the solid-phase synthesis method forms Te crystals by reacting Te powder under high temperature and high pressure conditions. This method is suitable for preparing large-sized Te crystals, but Te is volatile in this synthesis method, which makes it difficult to maintain a constant concentration of Te during single crystal growth. The fluctuation of concentration will lead to unstable crystal quality and difficult to accurately control the growth rate, thus affecting the consistency and performance of the final product.

[0003] Due to the hexagonal lattice structure of Te crystals, during the crystal growth process, especially when growing large-sized single crystals, cracks are likely to occur on the crystal surface, which severely limits the preparation of large-sized high-quality Te single crystals. The preparation process of high-purity Te is complex and difficult, and in single crystal growth, if the impurity content cannot be strictly controlled, it will have a negative impact on the electronic properties and structural quality of the final single crystal, reducing the application value of the product. In addition, growing Te single crystals under high temperature and high pressure conditions further increases the difficulty: in a high temperature and high pressure environment, the volatility of Te is more significant, especially at temperatures above 1000 °C, Te is extremely volatile, which makes it extremely difficult to maintain a stable concentration of Te in a high temperature environment, greatly affecting the growth and quality of the crystal. Te may undergo a phase change under high temperature and high pressure conditions, and its solubility changes significantly with temperature and pressure. This makes the control of solubility in the crystal growth process extremely complex, increasing the difficulty and uncertainty of the growth process. In a high temperature and high pressure growth environment, Te crystals are prone to accumulate large stresses during growth, and these stresses will lead to the formation of cracks or other defects, so stress management during growth is crucial. Under high pressure conditions, the crystal structure of Te may change, and pressure changes will affect the arrangement of Te molecules, possibly generating new phases or undesired defect structures. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for synthesizing Te crystals under high temperature and high pressure to solve the problem of unstable Te crystal quality.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for synthesizing Te crystals under high temperature and high pressure includes the following steps:

[0007] Using Te powder as the starting material, a high-temperature and high-pressure reaction is carried out in a sealed environment: the pressure is increased to 4.8 - 5.2 Gpa, then the temperature is raised to 570 - 610 °C, held at constant temperature and pressure for 25 - 35 min and then quenched. After the reaction is completed, it is rapidly cooled and slowly depressurized to obtain Te crystals. The sealed environment is to prevent the volatilization of Te from affecting the product performance. The reaction device for high-temperature and high-pressure can be selected according to the actual situation as long as the crystal growth conditions are achieved or satisfied.

[0008] In some possible implementation manners, during the process of increasing the pressure to 4.8 - 5.2 Gpa: the pressure is increased by 0.5 - 0.6 Gpa in the first 30 - 40 min, and then increased to 4.8 - 5.2 Gpa before 150 min.

[0009] In some possible implementation manners, the conditions for the high-temperature and high-pressure reaction are: the pressure is increased to 5 Gpa, then the temperature is raised to 600 °C, held at constant temperature and pressure for 30 min and then quenched.

[0010] In some possible implementation manners, during the process of increasing the pressure to 5 Gpa: the pressure is increased by 0.5 Gpa in the first 30 min; and then increased to 5 Gpa before 150 min.

[0011] In some possible implementation manners, the rapid cooling means cooling to room temperature within 2 min.

[0012] In some possible implementation manners, the slow depressurization means depressurizing to atmospheric pressure within 150 - 200 min.

[0013] In some possible implementation manners, before the high-temperature and high-pressure reaction, the Te powder is pressed into a cylindrical sample with a height of 3.2 mm and a diameter of 3.5 mm, and the sample is placed in a BN sample chamber.

[0014] In some possible implementation manners, the sealed environment includes assembling the BN sample chamber in a high-pressure synthesis assembly block and placing it in an octahedral anvil high-pressure device.

[0015] In some possible implementation manners, the specific steps for assembling the BN sample chamber in the high-pressure synthesis assembly block include: sealing the upper and lower openings of the BN tube with BN wafers, then sleeving a graphite tube outside the BN tube as a heating layer, closing the upper and lower openings with perforated graphite gaskets, inserting molybdenum columns into the holes as a conductive layer, and closing the outside of the graphite layer with a zirconia tube as a thermal insulation layer.

[0016] In some possible implementation manners, for the obtained Te crystals, the crystals are silver-white in color, the surface coatings are black, and the synthesized product Te crystals are of the hexagonal crystal system.

[0017] Advantages of the present invention:

[0018] The present invention synthesizes high-quality, large-sized crystals of Te, solves a difficult problem in the current field of material synthesis and preparation technologies, and provides guarantee for the experimental research on Te crystals.

[0019] The present invention solves some deficiencies in the growth of high-quality Te crystals under high temperature and high pressure. The growth method adopted by the present invention can effectively reduce the negative impact of the volatility of Te on crystal growth and will not introduce new impurities. Under the growth conditions adopted by the present invention, the crystal structure of the grown Te does not undergo distortion. Brief Description of the Drawings

[0020] The present invention will be further described below in conjunction with the accompanying drawings.

[0021] Figure 1 is the scanning electron microscope image of the Te crystal grown in Example 1 of the present invention;

[0022] Figure 2 is the Raman image of the Te crystal grown in Example 1 of the present invention;

[0023] Figure 3 is the vertical light polarization Raman image of the Te crystal grown in Example 1 of the present invention at 138 cm -1 ;

[0024] Figure 4 is the parallel light polarization Raman image of the Te crystal grown in Example 1 of the present invention at 138 cm -1 ;

[0025] Figure 5 is the image of the change of the resistance of the Te crystal grown in Example 1 of the present invention with temperature;

[0026] Figure 6 is the image of the change of the resistance of the Te crystal grown in Example 1 of the present invention with magnetic field;

[0027] Figure 7 is the Raman image of the Te crystal grown in Comparative Example 2 of the present invention;

[0028] Figure 8 is the Raman image of the Te crystal grown in Comparative Example 3 of the present invention. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0030] Obviously, the following description is only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, the present application can also be applied to other similar scenarios. In addition, it can also be understood that although the efforts made in such a development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing, or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood as the content disclosed in the present application being insufficient.

[0031] However, there will be cases where unnecessary details are omitted. For example, there are cases where the detailed description of well-known matters is omitted and the repeated description of actually identical structures is omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter recited in the claims.

[0032] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0033] The preparation process of high-purity Te crystals is complex and difficult. In single crystal growth, if the impurity content cannot be strictly controlled, it will have a negative impact on the electronic properties and structural quality of the final single crystal, reducing the application value of the product. In a high-temperature and high-pressure growth environment, Te crystals are prone to accumulate large stresses during growth, and these stresses will cause the formation of cracks or other defects, resulting in the distortion of the Te crystal structure.

[0034] Therefore, the embodiments of the present application provide a method for synthesizing Te crystals under high temperature and high pressure, including the following steps:

[0035] Using Te powder as the starting material, carry out a high-temperature and high-pressure reaction in a sealed environment: increase the pressure to 4.8 - 5.2 Gpa, then increase the temperature to 570 - 610 °C, hold the pressure and temperature for 25 - 35 min and then quench (if the holding time is too short, it may cause incomplete crystal growth and the grown crystal size is small), after the reaction is completed, quickly cool and slowly release the pressure to obtain Te crystals. The sealed environment is to prevent Te volatilization from affecting the product performance, and the reaction device for high temperature and high pressure can be selected according to the actual situation as long as the crystal growth conditions are achieved or satisfied.

[0036] In some embodiments, during the process of increasing the pressure to 4.8 - 5.2 Gpa: increase the pressure by 0.5 - 0.6 Gpa in the first 30 - 40 min, and then increase the pressure to 4.8 - 5.2 Gpa before 150 min.

[0037] In some embodiments, the conditions for the high-temperature and high-pressure reaction are as follows: The pressure is increased to 5 GPa, then the temperature is raised to 600 °C, and after holding the pressure and temperature for 30 min, quenching is carried out.

[0038] In some embodiments, during the process of increasing the pressure to 5 GPa: The pressure is increased by 0.5 GPa in the first 30 min; then the pressure is increased to 5 GPa before 150 min.

[0039] In some embodiments, the rapid cooling means that the temperature is decreased to room temperature within 2 min. When the time exceeds 60 min, it is identified by EDS&SEM that the product does not contain Te crystals.

[0040] In some embodiments, the slow pressure release means that the pressure is decreased to atmospheric pressure in 150 - 200 min. (Too fast pressure release will damage the tungsten carbide anvil used in the experiment.)

[0041] In some embodiments, before the high-temperature and high-pressure reaction, the Te powder is pressed into a cylindrical sample with a height of 3.2 mm and a diameter of 3.5 mm, and the sample is placed in a BN sample cell (boron nitride sample cell).

[0042] In some embodiments, the sealed environment includes assembling the BN sample cell in a high-pressure synthesis assembly block and placing it in an octahedral anvil high-pressure device.

[0043] In some embodiments, the specific steps of assembling the BN sample cell in the high-pressure synthesis assembly block include: Sealing the upper and lower openings of the BN tube (boron nitride tube) with BN wafers (boron nitride wafers), then sleeving a graphite tube outside the BN tube as a heating layer, sealing the upper and lower openings with perforated graphite gaskets, inserting molybdenum columns into the holes as a conductive layer, and sealing the outside of the graphite layer with a zirconia tube as a heat-insulating layer.

[0044] In some embodiments, for the obtained Te crystals, the crystals are silver-white in color, the surface coating is black, and the synthesized product Te crystals are of the hexagonal crystal system.

[0045] The following is illustrated with specific embodiments.

[0046] Example 1

[0047] A method for synthesizing Te crystals by high-temperature and high-pressure includes the following steps:

[0048] Step S1: Using analytically pure Te powder as the starting material;

[0049] Step S2: Using a tablet press to press the Te powder in Step S1 into a cylinder with a height of 3.2 mm and a diameter of 3.5 mm, placing the sample in a BN tube, and using BN as the pressure-transmitting device;

[0050] Step S3: Assemble the BN tube containing the sample in the high-pressure synthesis assembly block and place it in an octahedral large press for high-temperature and high-pressure reaction;

[0051] Step S4: After the high-temperature and high-pressure reaction is completed, take out the sample to obtain Te crystals.

[0052] Among them, the specific steps of assembling the BN tube in the high-pressure synthesis assembly block described in Step S3 include: sealing the upper and lower openings of the BN tube with BN wafers; subsequently, putting a graphite tube on the outer layer of the BN tube as a heating layer, sealing the upper and lower openings with perforated graphite gaskets, inserting molybdenum columns into the holes as a conductive layer, and using a zirconia tube as a thermal insulation layer to seal the outside of the graphite layer, and then loading the obtained sample into a regular octahedron made of MgO.

[0053] Among them, the high-temperature and high-pressure reaction conditions in Step S3 are to increase the pressure by 5 GPa and increase the temperature by 600 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 5 GPa before 150 min and increase the temperature by 600 °C), then carry out pressure and temperature holding for 30 min, and then perform quenching, and reduce the temperature to room temperature in 1 min. After depressurizing for 150 min, take out the sample.

[0054] The prepared sample was tested, and the results are as Figures 1-6 shown.

[0055] Figure 1 is the scanning electron microscope image of Te crystals, showing that the grown Te is a single crystal.

[0056] Figure 2 is the Raman image of Te crystals. There are obvious Raman peaks at 118 cm -1 and 138 cm -1 respectively, corresponding to the vibration peaks of Te.

[0057] Figure 3 and Figure 4 are the polarization Raman characteristics of the grown Te single crystal under the conditions of vertical light incidence and parallel light incidence at 138 cm -1 . The polarization Raman spectrum presents a four-lobe shape, indicating that the grown Te has polarization characteristics, which is consistent with the theoretical prediction.

[0058] Figure 5 and Figure 6 are the curves of the resistance of the sample changing with temperature and magnetic field respectively. As the temperature decreases, the resistance of the Te single crystal increases, showing semiconductor characteristics. Within 2 K and 4 T magnetic fields, the grown Te single crystal shows negative magnetoresistance characteristics.

[0059] Example 2

[0060] Compared with Example 1, this example is different in that the high-temperature and high-pressure reaction conditions in step S3 are different. Specifically, the high-temperature and high-pressure reaction conditions in step S3 are to increase the pressure by 5 GPa and increase the temperature by 570 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 5 GPa before 150 min and increase the temperature by 570 °C), then carry out pressure and temperature holding for 30 min, and then carry out quenching, and reduce the temperature to room temperature in 1 min. After depressurizing for 150 min, take out the sample. The obtained sample is the same as that in Example 1.

[0061] Example 3

[0062] Compared with Example 1, this example is different in that the high-temperature and high-pressure reaction conditions in step S3 are different. Specifically, the high-temperature and high-pressure reaction conditions in step S3 are to increase the pressure by 5 GPa and increase the temperature by 580 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 5 GPa before 150 min and increase the temperature by 580 °C), then carry out pressure and temperature holding for 30 min, and then carry out quenching, and reduce the temperature to room temperature in 1 min. After depressurizing for 150 min, take out the sample. The obtained sample is the same as that in Example 1.

[0063] Example 4

[0064] Compared with Example 1, this example is different in that the high-temperature and high-pressure reaction conditions in step S3 are different. Specifically, the high-temperature and high-pressure reaction conditions in step S3 are to increase the pressure by 5 GPa and increase the temperature by 590 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 5 GPa before 150 min and increase the temperature by 590 °C), then carry out pressure and temperature holding for 30 min, and then carry out quenching, and reduce the temperature to room temperature in 1 min. After depressurizing for 150 min, take out the sample. The obtained sample is the same as that in Example 1.

[0065] Example 5

[0066] Compared with Example 1, this example is different in that the high-temperature and high-pressure reaction conditions in step S3 are different. Specifically, the high-temperature and high-pressure reaction conditions in step S3 are to increase the pressure by 5 GPa and increase the temperature by 605 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 5 GPa before 150 min and increase the temperature by 605 °C), then carry out pressure and temperature holding for 30 min, and then carry out quenching, and reduce the temperature to room temperature in 1 min. After depressurizing for 150 min, take out the sample. The obtained sample is the same as that in Example 1.

[0067] Example 6

[0068] Compared with Example 1, this example is different in that the high-temperature and high-pressure reaction conditions in step S3 are different. Specifically, the high-temperature and high-pressure reaction conditions in step S3 are to increase the pressure to 5 GPa and increase the temperature to 610 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 5 GPa before 150 min and increase the temperature to 610 °C), then carry out pressure and temperature holding for 30 min, and then carry out quenching, and reduce the temperature to room temperature in 1 min. After releasing the pressure in 150 min, take out the sample. The obtained sample is the same as that in Example 1.

[0069] Comparative Example 1

[0070] Compared with Example 1, this comparative example is different in that the conditions of the high-temperature and high-pressure reaction are different.

[0071] The specific steps are as follows:

[0072] A method for synthesizing Te crystals by high temperature and high pressure includes the following steps:

[0073] Step S1: Use analytically pure Te powder as the starting material;

[0074] Step S2: Use a tablet press to press the Te powder in step S1 into a cylinder with a height of 3.2 mm and a diameter of 3.5 mm, put the sample into a BN tube, and use BN as the pressure transmission device;

[0075] Step S3: Assemble the BN tube containing the sample in a high-pressure synthesis assembly block and place it in an octahedral large press for high-temperature and high-pressure reaction;

[0076] Step S4: After the high-temperature and high-pressure reaction is completed, take out the sample to obtain Te crystals.

[0077] Among them, the specific steps of assembling the BN tube in the high-pressure synthesis assembly block in step S3 include: sealing the upper and lower openings of the BN tube with BN round pieces: subsequently, put a graphite tube on the outer layer of the BN tube as a heating layer, and seal the upper and lower openings with perforated graphite gaskets, insert molybdenum columns into the holes as a conductive layer, and seal the outside of the graphite layer with a zirconia tube as a heat-insulating layer, and then put the obtained sample into a regular octahedron made of MgO.

[0078] Among them, the high-temperature and high-pressure reaction conditions in step S3 are to increase the pressure to 2 GPa and increase the temperature to 650 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 2 GPa before 60 min and increase the temperature to 650 °C), then carry out pressure and temperature holding for 30 min, and then carry out quenching, and reduce the temperature to room temperature in 1 min. After releasing the pressure in 150 min, take out the sample. The size of the grown crystal is 10-20 μm and it is broken.

[0079] Comparative Example 2

[0080] This comparative example is different from Example 1 in that the conditions of the high-temperature and high-pressure reaction are different.

[0081] The specific steps are as follows:

[0082] A method for synthesizing Te crystals by high temperature and high pressure includes the following steps:

[0083] Step S1: Use analytically pure Te powder as the starting material;

[0084] Step S2: Use a tablet press to press the Te powder in Step S1 into a cylinder with a height of 3.2 mm and a diameter of 3.5 mm. Place the sample in a BN tube and use BN as the pressure transmitting device;

[0085] Step S3: Assemble the BN tube containing the sample in a high-pressure synthesis assembly block and place it in an octahedral large press for high-temperature and high-pressure reaction;

[0086] Step S4: After the high-temperature and high-pressure reaction is completed, take out the sample to obtain Te crystals.

[0087] Among them, the specific steps of assembling the BN tube in the high-pressure synthesis assembly block in Step S3 include: sealing the upper and lower openings of the BN tube with BN circular wafers; subsequently, putting a graphite tube on the outer layer of the BN tube as a heating layer, and closing the upper and lower openings with perforated graphite gaskets. Insert molybdenum columns into the holes as a conductive layer, and use a zirconia tube as a heat-insulating layer to seal the outside of the graphite layer. Then, put the obtained sample into a regular octahedron made of MgO.

[0088] Among them, the high-temperature and high-pressure reaction conditions in Step S3 are: increasing the pressure to 6 GPa and raising the temperature to 540 °C (raising the pressure by 0.5 GPa in the first 30 min, and then raising the pressure to 6 GPa before 180 min and raising the temperature to 540 °C), then performing pressure and temperature holding for 30 min, and then quenching, reducing the temperature to room temperature in 1 min. After releasing the pressure in 150 min, take out the sample. (Raman tests were carried out and it was found that the Raman peaks were not the same as those in Example 1. At this temperature and pressure, the structure changed. The Raman test is Figure 7 )

[0089] Comparative Example 3

[0090] This comparative example is different from Example 1 in that the conditions of the high-temperature and high-pressure reaction are different.

[0091] The specific steps are as follows:

[0092] A method for synthesizing Te crystals by high temperature and high pressure includes the following steps:

[0093] Step S1: Use analytically pure Te powder as the starting material;

[0094] Step S2: Use a tablet press to press the Te powder in Step S1 into a cylinder with a height of 3.2 mm and a diameter of 3.5 mm. Place the sample in a BN tube and use BN as the pressure transmitting device.

[0095] Step S3: Assemble the BN tube containing the sample in Step S2 in a high-pressure synthesis assembly block and place it in an octahedral large press for high-temperature and high-pressure reaction.

[0096] Step S4: After the high-temperature and high-pressure reaction is completed, take out the sample to obtain Te crystals.

[0097] Among them, the specific steps of assembling the BN tube in the high-pressure synthesis assembly block described in Step S3 include: sealing the upper and lower openings of the BN tube with BN wafers; subsequently, putting a graphite tube on the outer layer of the BN tube as a heating layer, and closing the upper and lower openings with perforated graphite gaskets. Insert molybdenum columns into the holes as a conductive layer, and use a zirconia tube as a heat-insulating layer to seal the outside of the graphite layer. Then, put the obtained sample into a regular octahedron made of MgO.

[0098] Among them, the high-temperature and high-pressure reaction conditions in Step S3 are to increase the pressure by 5 GPa and increase the temperature by 700 °C (increase the pressure by 0.5 GPa in the first 30 min, and then increase the pressure to 6 GPa before 150 min and increase the temperature by 540 °C). Then, carry out pressure and temperature holding for 45 min, and then perform quenching to reduce the temperature to room temperature in 1 min. After releasing the pressure in 150 min, take out the sample. (The growth effect is not good, the crystal size is less than 20 μm, and subsequent Raman tests were carried out, which were basically the same as the peaks in Example 1. The Raman test is Figure 8 ).

[0099] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0100] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing Te crystals at high temperature and high pressure, characterized in that: The steps include: Using Te powder as the starting material, a high temperature and high pressure reaction is carried out in a sealed environment: the pressure is increased to 4.8-5.2Gpa, then the temperature is increased to 570-610℃, and the temperature is kept at this temperature and pressure for 25-35min before quenching. After the reaction is completed, the reaction is quickly cooled and the pressure is slowly released to obtain Te crystals.

2. The method for synthesizing Te crystals at high temperature and high pressure according to claim 1, characterized in that: In the process of raising the blood pressure to 4.8-5.2Gpa: increase by 0.5-0.6Gpa in the first 30-40 minutes, and then increase to 4.8-5.2Gpa before 150 minutes.

3. The method for synthesizing Te crystals at high temperature and high pressure according to claim 1, characterized in that: The conditions of the high temperature and high pressure reaction are: increasing the pressure to 5 GPa, then increasing the temperature to 600°C, maintaining the temperature and pressure for 30 minutes, and then quenching.

4. The method for synthesizing Te crystals at high temperature and high pressure according to claim 3, characterized in that: During the process of increasing the pressure to 5 Gpa: increase by 0.5 Gpa in the first 30 minutes; then increase to 5 Gpa before 150 minutes.

5. The method for synthesizing Te crystals at high temperature and high pressure according to claim 1, characterized in that: The rapid cooling refers to cooling to room temperature within 2 minutes.

6. The method for synthesizing Te crystals at high temperature and high pressure according to claim 1, characterized in that: The slow pressure relief refers to reducing the pressure to normal pressure over 150-200 minutes.

7. The method for synthesizing Te crystals at high temperature and high pressure according to claim 1, characterized in that: Before the high temperature and high pressure reaction, the Te powder was pressed into a cylindrical sample with a height of 3.2 mm and a diameter of 3.5 mm, and the sample was placed in a BN sample chamber.

8. The method for synthesizing Te crystals at high temperature and high pressure according to claim 7, characterized in that: The sealed environment includes assembling the BN sample chamber in a high pressure synthesis assembly block and placing it in an octahedral high pressure device.

9. The method for synthesizing Te crystals at high temperature and high pressure according to claim 8, characterized in that: The specific steps of assembling the BN sample chamber in the high-pressure synthesis assembly block include: sealing the upper and lower openings of the BN tube with BN discs, then putting a layer of graphite tube on the outer layer of the BN tube as a heating layer, sealing the upper and lower openings with graphite gaskets with holes, inserting molybdenum columns into the holes as a conductive layer, and sealing the outside of the graphite layer with a layer of zirconia tube as an insulation layer.

10. The method for synthesizing Te crystals at high temperature and high pressure according to claim 1, characterized in that: The obtained Te crystal is silvery white, the surface coating is black, and the synthesized product Te crystal is a hexagonal crystal system.

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