A method for synthesizing phosphor crystals by controlling the cooling rate

Abstract

The application provides a method for synthesizing phosphorus crystals by controlling a cooling rate, and relates to the technical field of phosphorus crystal preparation.The method comprises the following steps: loading commercial red phosphorus, bismuth and a transport agent into a sealed device in a heating device with a temperature difference of 10 DEG C or below, vacuum sealing after shaking; performing temperature rising, temperature keeping, temperature dropping and natural cooling to room temperature on the vacuum sealed sealed device; preferentially forming purple phosphorus crystals or black phosphorus crystals by controlling a cooling rate; preferentially forming purple phosphorus crystals when the cooling rate is less than 5 DEG C / h; preferentially forming black phosphorus crystals when the cooling rate is greater than 5 DEG C / h.The application realizes selective and efficient preparation of purple phosphorus crystals and black phosphorus crystals in the same reaction system, has the advantages of simple process, good phase selectivity, simple post-treatment and the like, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of phosphorus crystal preparation technology, and in particular to a method for synthesizing phosphorus crystals by controlling the cooling rate. Background Technology

[0002] Phosphorus crystals, due to their unique structural features and physicochemical properties, possess potential applications in optoelectronic devices, energy storage, catalysis, and functional materials. Among them, black phosphorus and purple phosphorus crystals, as typical allotropes of phosphorus, exhibit distinct crystal structures and performance characteristics. Therefore, developing tunable, reproducible, and scale-up methods for preparing phosphorus crystals is of great significance for advancing fundamental research and application development in related materials.

[0003] The preparation of black phosphorus crystals typically requires high temperature and pressure, mineralizer assistance, or chemical vapor transport. This process often suffers from long reaction cycles, demanding equipment requirements, insufficient product phase selectivity, and difficulty in removing byproducts or residual additives. For purple phosphorus crystals, existing methods include plasma-assisted methods, metal flux methods, bismuth flux methods, and catalytic conversion methods. However, some methods require large amounts of metal flux or specific reaction equipment, resulting in high raw material consumption, complex post-processing, limited batch production, and limitations on subsequent application research and large-scale production.

[0004] Furthermore, black phosphorus crystals and purple phosphorus crystals are quite sensitive to formation conditions. Existing technologies usually require changing the reaction system, the type of mineralizer, the temperature range configuration, or other complex process parameters to achieve the preparation of the target crystal phase. It is difficult to achieve selective control of different phosphorus crystals with simple parameters in the same reaction system.

[0005] Therefore, it is necessary to develop a phosphorus crystal synthesis method that has a simple process flow, low equipment requirements, good phase selectivity, low post-processing burden, and can meet the needs of preparing both black phosphorus crystals and purple phosphorus crystals. Summary of the Invention

[0006] In view of this, the present invention provides a method for synthesizing phosphorus crystals by controlling the cooling rate. The present invention achieves selective and efficient preparation of purple phosphorus and black phosphorus crystals in the same reaction system by heating commercial red phosphorus with the assistance of bismuth and a transport agent in a temperature-controlled heating environment, followed by heating, holding, cooling at a set rate, and natural cooling to room temperature. The cooling rate is used as a key parameter to control the preferential formation of the product's crystal phase. This method has advantages such as simple process, good phase selectivity, and simple post-processing, and has good application prospects.

[0007] The phosphorus crystals described in this invention are black phosphorus crystals or purple phosphorus crystals, and the method for synthesizing phosphorus crystals by controlling the cooling rate includes the following steps: In a heating device with a temperature difference of less than 10°C, commercial red phosphorus, bismuth, and a transport agent are loaded into a sealed device. After shaking the sealed device to mix them, it is vacuum sealed. The vacuum-sealed device is then heated, kept at a constant temperature, cooled down, and allowed to cool naturally to room temperature. The bismuth and transport agent are then recovered to obtain the final product. The method controls the cooling rate to preferentially form the product as purple phosphorus crystals or black phosphorus crystals. When the cooling rate is less than 5°C / h, the resulting product is preferably purple phosphorus crystals; when the cooling rate is greater than 5°C / h, the resulting product is preferably black phosphorus crystals.

[0008] Preferably, when the phosphorus crystals are purple phosphorus crystals, the sealing device is heated from room temperature to 540~650℃, held at that temperature for 1~40 h, then cooled to 400℃~500℃ at a cooling rate of less than 5℃ / h, held at that temperature for 1~40 h, and then naturally cooled to room temperature to obtain purple phosphorus crystals. More preferably, when the phosphorus crystals are purple phosphorus crystals, the sealing device is heated from room temperature to 560℃, held at that temperature for 2 h, then cooled to 480℃ at a cooling rate of 1.9℃ / h, held at that temperature for 1 h, and then naturally cooled to room temperature.

[0009] Preferably, when the phosphorus crystals are black phosphorus crystals, the sealing device is heated from room temperature to 500-650°C, held at that temperature for 0.1-20 h, cooled to 400-500°C at a cooling rate greater than 5°C / h, and then allowed to cool naturally to room temperature to obtain black phosphorus crystals. More preferably, when the phosphorus crystals are black phosphorus crystals, the sealing device is heated from room temperature to 560°C, held at that temperature for 0.1 h, cooled to 480°C at a cooling rate of 15°C / h, and then allowed to cool naturally to room temperature.

[0010] Preferably, the mass ratio of the commercial red phosphorus, bismuth, and transporter is (10~32):1:1.

[0011] Preferably, the transporter is selected from at least one of bismuth iodide, iodine, tin tetraiodide, and potassium iodide.

[0012] Preferably, the sealing device is a quartz tube.

[0013] Preferably, the vacuum sealing is performed at a pressure of 1 to 100 Pa.

[0014] Preferably, nitric acid and ethanol are used to recover bismuth and transport agent from phosphorus crystals.

[0015] The X-ray diffraction pattern of the purple phosphorus crystals prepared by this invention exhibits characteristic peaks at 2θ of 8.14°, 16.32°, 24.58°, and 32.95°, and the Raman characteristic peak includes a peak at 359.6 cm⁻¹. -1 373.2 cm -1450.6 cm -1 472.6 cm -1 and 492.9 cm -1 It has a two-dimensional structure.

[0016] The X-ray diffraction pattern of the black phosphorus crystals prepared by this invention exhibits characteristic peaks at 2θ of 16.9°, 34.28°, and 52.32°, and the Raman characteristic peak includes a peak at 361.4 cm⁻¹. -1 465.6 cm -1 and 437.8 cm -1 .

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention introduces bismuth and a transport agent into a temperature-controlled heating environment to assist the conversion of commercial red phosphorus, and uses the cooling rate as a key process parameter to regulate the crystal phase of the product. This allows the reaction system to preferentially form purple phosphorus crystals or black phosphorus crystals depending on the cooling rate. This method eliminates the need to establish completely different reaction systems for different phosphorus crystals, simplifies process control, and improves the controllability and repeatability of the phosphorus crystal preparation process.

[0018] The method described in this invention can complete the heating, holding, controlled-rate cooling, and natural cooling to room temperature processes within a sealed device, simplifying the reaction apparatus and process flow, and avoiding excessive reliance on complex temperature configurations or high-pressure equipment. Selective generation of the target crystalline phase can be achieved by controlling the cooling process, which helps reduce the operational difficulty during process scale-up and batch preparation.

[0019] This invention employs bismuth and a transport agent to assist in the conversion of red phosphorus, which can reduce the adverse effects of large amounts of metal additives on product separation and purification in traditional metal flux methods, and lower the burden of post-processing. Simultaneously, this method avoids systems such as lead flux that are detrimental to the environment and subsequent applications, and is more conducive to obtaining phosphorus crystal products with fewer impurities and relatively simpler subsequent processing.

[0020] The method of this invention can meet the preparation requirements of both purple phosphorus crystals and black phosphorus crystals, and has good prospects for further application in the preparation of phosphorus crystal materials and related industrial applications. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 The image shows the XRD pattern of the purple phosphorus crystals obtained in Example 1. Figure 2 Raman spectroscopy of the purple phosphorus crystals obtained in Example 1; Figure 3 Here is a SEM image of the purple phosphorus crystals obtained in Example 1; Figure 4 The elemental analysis diagram of the purple phosphorus crystals prepared in Example 1 is shown below. Figure 5 Comparison of the morphology of commercial red phosphorus powder, ground purple phosphorus crystal powder, and prepared blocky black phosphorus crystals. Figure 6 The image shows the XRD pattern of the black phosphorus crystals obtained in Example 5. Figure 7 Raman spectroscopy of the black phosphorus crystals obtained in Example 5; Figure 8 The image shows the Raman diagram of the black phosphorus crystals prepared in Comparative Example 1. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise stated, all experiments were repeated three times, and the results are expressed as averages.

[0025] The commercial red phosphorus used in the examples and comparative examples had a purity of 99.9%; the bismuth had a purity of 99.9% and passed through a 200-mesh sieve before use; and the transporter had a purity of 98%.

[0026] Example 1: A method for synthesizing phosphorus crystals by controlling the cooling rate, the steps of which are as follows: 23 mg of bismuth, 23 mg of bismuth iodide, and 0.69 g of commercial red phosphorus were weighed and placed in a quartz tube 20 cm long and 16 mm in inner diameter. The quartz tube was then vacuum-sealed and fused together. The sealed quartz tube was placed in a muffle furnace (temperature difference less than 10 °C) and heated from room temperature to 560 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then cooled to 480 °C at a rate of 1.9 °C / h and held at that temperature for 1 h. After natural cooling to room temperature, the bismuth and transport agent were recovered to obtain purple phosphorus crystals. 0.668 g of purple phosphorus crystals were collected, with a yield of 96.8%.

[0027] XRD analysis of the prepared purple phosphorus crystals revealed extremely strong characteristic peaks at 8.14° (002), 16.32° (004), 24.58° (006), and 32.95° (008), all characteristic peaks of purple phosphorus. These peaks closely matched the PDF card (PDF#97-002-9273) for purple phosphorus and were consistent with the characteristic peak structures reported in current literature, confirming the successful synthesis of purple phosphorus crystals. Raman results showed that the Raman characteristic peak of the prepared purple phosphorus was 359.6 cm⁻¹. -1 373.2 cm -1 450.6 cm -1 472.6 cm -1 and 492.9cm -1 The structure is consistent with that of purple phosphorus crystals reported in the literature. SEM results show that the prepared purple phosphorus crystals have a typical two-dimensional structure. Elemental analysis of the prepared purple phosphorus crystals revealed that the surface of the crystals contained only a small amount of bismuth, and the purity of the purple phosphorus was 99.75 at%. Subsequent impurity removal only required the removal of bismuth.

[0028] Example 2 The difference from Example 1 is as follows: 0.023 g of bismuth, 0.023 g of iodine and 0.69 g of commercial red phosphorus were weighed and placed in a quartz tube with a length of 20 cm and an inner diameter of 16 mm; the sealed quartz tube was placed in a muffle furnace and heated from room temperature to 580°C at a heating rate of 5°C / min, held at that temperature for 2 h, and then cooled to 400°C at a cooling rate of 2.5°C / h and held at that temperature for 1 h before naturally cooling to room temperature to obtain purple phosphorus crystals. 0.64 g of purple phosphorus crystals were collected, with a yield of 92.8%.

[0029] Example 3 The difference from Example 1 is as follows: 0.067 g of bismuth, 0.067 g of tin tetraiodide and 2 g of commercial red phosphorus were weighed and placed in a quartz tube with a length of 20 cm and an inner diameter of 14 mm; the sealed quartz tube was placed in a muffle furnace and heated from room temperature to 600°C at a heating rate of 5°C / min, held at that temperature for 2 h, cooled to 480°C at a cooling rate of 1°C / h and held at that temperature for 1 h, and then allowed to cool naturally to room temperature to obtain purple phosphorus crystals. 1.83 g of purple phosphorus crystals were collected, with a yield of 91.5%.

[0030] Example 4 The difference from Example 1 is as follows: 0.1 g of bismuth, 0.1 g of bismuth iodide and 3 g of commercial red phosphorus were weighed and placed in a quartz tube with a length of 30 cm and an inner diameter of 14 mm; the sealed quartz tube was placed in a muffle furnace and heated from room temperature to 580°C at a heating rate of 5°C / min. After holding at this temperature for 4 h, the temperature was lowered to 480°C at a cooling rate of 0.8°C / h and held at this temperature for 1 h. Then, the temperature was allowed to cool naturally to room temperature.

[0031] After the reaction was completed, the mass of purple phosphorus crystals collected was 2.88 g, with a yield of 96%.

[0032] Example 5 The difference from Example 1 is as follows: 0.2 g of bismuth, 0.2 g of bismuth iodide and 2 g of commercial red phosphorus were weighed and placed in a quartz tube with a length of 30 cm and an inner diameter of 14 mm; the sealed quartz tube was placed in a muffle furnace and heated from room temperature to 560°C at a heating rate of 5°C / min, held at that temperature for 0.1 h, and then cooled to 480°C at a cooling rate of 15°C / h before naturally cooling to room temperature.

[0033] After the reaction was complete, the quartz tube was removed from the muffle furnace, and 1.96 g of black phosphorus crystals were collected, with a yield of 97.8%.

[0034] A comparison of the morphologies of commercial red phosphorus powder, ground purple phosphorus crystal powder, and prepared bulk black phosphorus crystals. Figure 5 As shown. The XRD and Raman results of black phosphorus crystals are as follows. Figure 6 , Figure 7 As shown. XRD analysis of the prepared black phosphorus crystals showed that the main diffraction peaks of the prepared black phosphorus crystals appeared at 16.9° (020), 34.28° (040) and 52.32° (060), and no impurity peaks appeared, proving the formation of high-purity black phosphorus. Raman results showed that at 361.4 cm⁻¹... -1 465.6cm -1 and 437.8 cm -1 Each of these peaks has a distinct characteristic peak, corresponding to the A1g (out-of-plane), A2g, and B2g (in-plane) vibration modes of BP, respectively.

[0035] Example 6 The difference from Example 1 is as follows: 0.07 g of bismuth, 0.07 g of tin tetraiodide and 0.7 g of commercial red phosphorus were weighed and placed in a quartz tube with a length of 20 cm and an inner diameter of 16 mm; the sealed quartz tube was placed in a muffle furnace and heated from room temperature to 560°C at a heating rate of 5°C / min, held at that temperature for 2 h, and then cooled to 480°C at a cooling rate of 30°C / h before being allowed to cool naturally to room temperature.

[0036] After the reaction was complete, the quartz tube was removed from the muffle furnace, and 0.65 g of black phosphorus crystals were collected, with a yield of 92.9%.

[0037] Example 7 The difference from Example 1 is as follows: 0.1 g of bismuth, 0.1 g of KI and 1.0 g of commercial red phosphorus were weighed and placed in a quartz tube with a length of 20 cm and an inner diameter of 16 mm; the sealed quartz tube was placed in a muffle furnace and heated from room temperature to 580°C at a heating rate of 5°C / min and held at that temperature for 0.1 h; then cooled to 480°C at a cooling rate of 6°C / h and allowed to cool naturally to room temperature.

[0038] After the reaction was complete, the quartz tube was removed from the muffle furnace, and 0.91 g of black phosphorus crystals were collected, with a yield of 91%.

[0039] Comparative Example 1 The difference from Example 1 is that 0.7 g of RP (99.9%, powder) and 1 g of bismuth powder (99.9%, 200 mesh) were directly added to a quartz tube with a length of 20 cm and an inner diameter of 16 mm, and the tube was sealed under vacuum at 1-100 Pa. The tube was then placed in a heating device with a temperature difference of less than 10°C, and the temperature was increased from room temperature to 440°C at a rate of 5°C / min. The reaction was carried out at 440°C for 24 h, and then the temperature was reduced to 250°C within 10 h before being allowed to cool naturally to room temperature.

[0040] The results show that the crystal quality of this method is poor, the crystals are small, and the black phosphorus and metallic bismuth are fused together, making separation difficult. Therefore, adding a transport agent is crucial for the rapid growth of black phosphorus crystals and the separation of bismuth.

[0041] The Raman spectrum of the black phosphorus obtained after the reaction is as follows: Figure 8 As shown, at 361.4 cm -1 465.6 cm -1 and 437.8cm -1 The presence of distinct characteristic peaks at each point corresponds to the A1g (out-of-plane), A2g, and B2g (in-plane) vibrational modes of BP, respectively, demonstrating the successful synthesis of black phosphorus crystals.

[0042] The results showed that black phosphorus crystals could be prepared by directly reacting bismuth powder with commercial red phosphorus, and the presence of a transport agent accelerated the precipitation of black phosphorus crystals. However, this method has drawbacks, including the use of large amounts of metallic bismuth, long preparation cycles, and increased costs associated with the removal of metallic bismuth.

[0043] Comparative Example 2 The difference from Example 1 is that bismuth is not added; instead, 0.023 g of bismuth iodide and 0.69 g of commercial red phosphorus are weighed and placed into two quartz tubes, each 20 cm long and 16 mm in inner diameter; the sealed quartz tubes are then placed into two muffle furnaces, A and B, under different temperature conditions. Condition A: The temperature was increased from room temperature to 560°C at a rate of 5°C / min, and held at that temperature for 0.1 h. back The temperature was lowered to 480℃ at a rate of 15℃ / h and then allowed to cool naturally to room temperature.

[0044] Condition B: The temperature was increased from room temperature to 560℃ at a heating rate of 5℃ / min, held for 2 h, then decreased to 480℃ at a cooling rate of 1.9℃ / h and held for 1 h before being allowed to cool naturally to room temperature.

[0045] After the reaction was completed, the quartz tubes were removed from the muffle furnace. No black phosphorus or purple phosphorus crystals were found to have formed in quartz tubes A and B.

[0046] Comparative Example 3 The difference from Example 1 is that no transport agent was added. 0.023 g of bismuth and 0.69 g of commercial red phosphorus were weighed and placed into a quartz tube 20 cm long and 16 mm in inner diameter. The sealed quartz tubes were then placed into two sets of muffle furnaces, A and B, under different temperature conditions. Condition A: The temperature was increased from room temperature to 560°C at a rate of 5°C / min, and held at that temperature for 0.1 h. back The temperature was lowered to 480℃ at a rate of 15℃ / h and then allowed to cool naturally to room temperature.

[0047] Condition B: The temperature was increased from room temperature to 560℃ at a heating rate of 5℃ / min, held for 2 hours, then decreased to 480℃ at a cooling rate of 1.9℃ / h and held for 1 hour before being allowed to cool naturally to room temperature.

[0048] After the reaction was completed, quartz tubes A and B were removed from the muffle furnace, and no purple phosphorus or black phosphorus crystals were formed in either of them.

[0049] Therefore, it can be seen that, without the addition of a transport agent, the amount of bismuth used is crucial to the formation of black phosphorus. The presence of a transport agent accelerates the vaporization of red phosphorus and the rapid formation and growth of black phosphorus crystals, making it a necessary additive in the preparation of black phosphorus.

[0050] Comparative Example 4 The difference from Example 1 is that bismuth is replaced with tin. 23 mg of tin, 23 mg of bismuth iodide, and 0.69 g of commercial red phosphorus are weighed and placed into a quartz tube 20 cm long and 16 mm in inner diameter. The sealed quartz tube is then placed into two muffle furnaces, A and B, under different temperature conditions. Condition A: The temperature was increased from room temperature to 560°C at a rate of 5°C / min, and held at that temperature for 0.1 h. back The temperature was lowered to 480℃ at a rate of 15℃ / h and then allowed to cool naturally to room temperature.

[0051] Condition B: The temperature was increased from room temperature to 560℃ at a heating rate of 5℃ / min, held for 2 hours, then decreased to 480℃ at a cooling rate of 1.9℃ / h and held for 1 hour before being allowed to cool naturally to room temperature.

[0052] After the reaction was completed, quartz tubes A and B were removed from the muffle furnace, and no purple phosphorus or black phosphorus crystals were formed in either of them.

[0053] Example 8 The difference from Example 1 is that the cooling rate is adjusted to 4.5℃ / h, while other conditions remain unchanged.

[0054] After the reaction, XRD and Raman spectroscopy revealed that the main product was purple phosphorus crystals, with 0.63 g collected, representing a yield of 90%. XRD analysis showed that the product exhibited characteristic peaks of purple phosphorus crystals at 2θ values ​​of 8.1°, 16.3°, 24.6°, and 32.9°. Raman spectroscopy showed that the product had a peak at 357 cm⁻¹. -1 370cm -1 388cm -1 469cm -1 490cm -1 The sample exhibits characteristic peaks of purple phosphorus crystals; elemental analysis results show that the phosphorus content in the obtained purple phosphorus crystals is 99.2%.

[0055] Example 9 The difference from Example 1 is that the heat preservation time is adjusted to 0.1 h and the cooling rate is adjusted to 6℃ / h. After cooling to 480℃, the heat preservation treatment at 480℃ is no longer performed, but the temperature is allowed to cool naturally to room temperature.

[0056] After the reaction, XRD and Raman spectroscopy revealed that the main product was black phosphorus crystals, with 0.64 g of black phosphorus crystals collected, representing a yield of 92.8%. XRD analysis showed that the product exhibited characteristic peaks of black phosphorus crystals at 2θ values ​​of 16.9°, 34.28°, and 52.32°. Raman spectroscopy showed that the product had a peak at 361.4 cm⁻¹. -1 465.6 cm -1 and 437.8 cm -1 The sample exhibits characteristic peaks of black phosphorus crystals; elemental analysis results show that the obtained black phosphorus crystals contain 99% phosphorus.

[0057] Example 10 The difference from Example 1 is that the transport agent is replaced by iodine instead of bismuth iodide, the high temperature holding time at 560°C is adjusted to 0.1 h, the cooling rate is adjusted to 15°C / h, and after cooling to 480°C, the 480°C holding is no longer performed, but the temperature is allowed to cool naturally to room temperature.

[0058] After the reaction, XRD and Raman spectroscopy revealed that the main product was black phosphorus crystals, with 0.64 g of black phosphorus crystals collected, representing a yield of 93%. XRD analysis showed that the product exhibited characteristic peaks of black phosphorus crystals at 2θ values ​​of 16.9°, 34.28°, and 52.32°. Raman spectroscopy showed that the product had a peak at 361.4 cm⁻¹. -1 465.6 cm -1 and 437.8 cm -1 The sample exhibits characteristic peaks of black phosphorus crystals; elemental analysis results show that the obtained black phosphorus crystals contain 99% phosphorus.

[0059] Example 11 The difference from Example 1 is that the transporter is replaced with potassium iodide instead of bismuth iodide, and the cooling rate is adjusted to 4.5℃ / h, while other conditions remain unchanged.

[0060] After the reaction, XRD and Raman spectroscopy revealed that the product was mainly purple phosphorus crystals, with 0.63 g of purple phosphorus crystals collected, representing a yield of 90%. XRD analysis showed that the product exhibited characteristic peaks of purple phosphorus crystals at 2θ values ​​of 8.1°, 16.3°, 24.6°, and 32.9°. Raman spectroscopy showed that the product had a peak at 357 cm⁻¹. -1 370 cm -1 388 cm -1 469 cm -1 490cm -1 The sample exhibits characteristic peaks of purple phosphorus crystals; elemental analysis results show that the phosphorus content in the obtained purple phosphorus crystals is 98%.

[0061] Comparative Example 5 The difference from Example 1 is that the cooling rate is adjusted to 5℃ / h, while other conditions remain unchanged.

[0062] After the reaction, XRD and Raman spectroscopy revealed that the collected black phosphorus and purple phosphorus crystals were 0.42 g and 0.21 g, respectively, with yields of 61% and 30%. XRD analysis showed that the products exhibited characteristic peaks of black phosphorus and purple phosphorus at 2θ values ​​of 16.9°, 34.28°, 52.32° and 8.1°, 16.3°, 24.6°, 32.9°, respectively. Raman spectroscopy showed that the products exhibited characteristic peaks at 361.4 cm⁻¹. -1 465.6 cm -1 and 437.8 cm -1 and 357 cm -1 370 cm -1 388 cm -1 469 cm -1 490 cm -1The peaks at these locations are characteristic of black phosphorus and purple phosphorus, respectively.

[0063] Comparative Example 6 The difference from Example 1 is that after the heat preservation treatment is completed, the temperature is not cooled according to the set cooling rate, but is directly cooled to room temperature naturally.

[0064] After the reaction was completed, XRD and Raman spectroscopy showed that no black phosphorus or purple phosphorus crystals were collected.

[0065] Comparative Example 7 The difference from Example 1 is that the sealed quartz tube is placed in a heating zone with a temperature difference greater than 10°C for the reaction, while other conditions remain unchanged.

[0066] After the reaction, XRD and Raman spectroscopy revealed that the collected purple phosphorus and black phosphorus crystals were 0.45 g and 0 g, respectively, with yields of 65% and 0%. XRD analysis showed that the products exhibited characteristic peaks of purple phosphorus at 2θ values ​​of 8.1°, 16.3°, 24.6°, and 32.9°; Raman spectroscopy showed that the products exhibited characteristic peaks at 357 cm⁻¹. -1 370cm -1 388cm -1 469cm -1 490cm -1 It exhibits characteristic peaks of purple phosphorus.

[0067] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for synthesizing phosphorus crystals by controlling the cooling rate, characterized in that, The phosphorus crystals are black phosphorus crystals and / or purple phosphorus crystals, and the method includes the following steps: In a heating device with a temperature difference of less than 10°C, commercial red phosphorus, bismuth, and a transport agent are loaded into a sealed container, shaken well, and then vacuum-sealed. The vacuum-sealed container is then heated, kept at a constant temperature, cooled down, and allowed to cool naturally to room temperature. The bismuth and transport agent are then recovered to obtain the final product. The method controls the cooling rate to preferentially form the product as purple phosphorus crystals or black phosphorus crystals. When the cooling rate is less than 5°C / h, the resulting product is preferably purple phosphorus crystals; when the cooling rate is greater than 5°C / h, the resulting product is preferably black phosphorus crystals.

2. The method for synthesizing phosphorus crystals by controlling the cooling rate according to claim 1, characterized in that, When the phosphorus crystal is purple phosphorus crystal, the sealing device is heated from room temperature to 540~650℃ and kept at that temperature for 1~40 h. Then, it is cooled to 400℃~500℃ at a cooling rate of less than 5℃ / h and kept at that temperature for 1~40 h. Finally, it is allowed to cool naturally to room temperature to obtain purple phosphorus crystal.

3. The method for synthesizing phosphorus crystals by controlling the cooling rate according to claim 2, characterized in that, When the phosphorus crystal is purple phosphorus crystal, the sealing device is heated from room temperature to 560°C, kept at that temperature for 2 hours, cooled to 480°C at a cooling rate of 1.9°C / h, kept at that temperature for 1 hour, and then allowed to cool naturally to room temperature.

4. The method for synthesizing phosphorus crystals by controlling the cooling rate according to claim 1, characterized in that, When the phosphorus crystal is black phosphorus crystal, the sealing device is heated from room temperature to 500~650℃, kept at that temperature for 0.1~20 h, cooled to 400~500℃ at a cooling rate of more than 5℃ / h, and then naturally cooled to room temperature to obtain black phosphorus crystal.

5. The method for synthesizing phosphorus crystals by controlling the cooling rate according to claim 4, characterized in that, When the phosphorus crystal is black phosphorus crystal, the sealing device is heated from room temperature to 560°C, kept at that temperature for 0.1 h, cooled to 480°C at a cooling rate of 15°C / h, and then allowed to cool naturally to room temperature.

6. The method for synthesizing phosphorus crystals by controlling the cooling rate according to claim 1, characterized in that, The mass ratio of the commercial red phosphorus, bismuth, and transporter is (10~32):1:

1.

7. The method for synthesizing phosphorus crystals by controlling the cooling rate according to claim 1, characterized in that, The transport agent is selected from at least one of bismuth iodide, iodine, tin tetraiodide, and potassium iodide.

8. The method for synthesizing phosphorus crystals by controlling the cooling rate according to claim 1, characterized in that, The sealing device is a quartz tube.

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