A method for preparing a ni p2 crystal

Abstract

The application provides a preparation method of NiP2 crystal, namely, an oscillation type heating is used to control the nucleation number of the crystal, and a cooling rate is controlled, so that NiP2 single crystals with different sizes and shapes are successfully prepared. The application belongs to the field of material science and technology. The crystal growth method provided by the application is not only simple in process and low in cost, but also controllable in crystal size and shape. The application not only solves the problem of difficult growth of large-size NiP2 single crystals, but also has great significance for the development of traditional crystal growth technology and semiconductor preparation process.

Description

Technical Field

[0001] This invention belongs to the field of materials science, specifically relating to a method for preparing NiP2 crystals. Background Technology

[0002] NiP2 crystal is an important functional material with excellent electronic, thermal, and mechanical properties, thus finding wide applications in semiconductors, catalysis, and energy storage. In recent years, with the development of semiconductor technology, there has been an urgent need to improve the overall performance of crystals, including size, purity, and mechanical properties. Therefore, inventing a growth process for NiP2 crystals and a method for controlling its crystal size and defects is of great significance.

[0003] Single-crystal materials possess highly ordered crystal structures and often exhibit superior physical properties in electrical and optical aspects, making them irreplaceable materials in many high-tech fields. Single-crystal materials are also of great significance for condensed matter physics research because their near-ideal crystal structure avoids interference from defects in the research results, which is crucial for revealing the intrinsic physical properties of materials.

[0004] Currently, crystal growth methods mainly include the Czochralski method, the Bridgman method, and the floating zone method. These methods are suitable for high-melting-point materials, and crystal growth requires a certain degree of supercooling. Chemical vapor deposition and physical vapor deposition are suitable for thin film growth, requiring the constituent elements of the material to have similar melting and boiling points, and the elements to be easily volatile. Because Ni and P have very different melting and boiling points—Ni has an extremely high melting point while P has a very low boiling point—the above methods are not suitable for the growth of NiP2 single crystals. In the laboratory, the maximum size of NiP2 single crystals grown by traditional flux methods does not exceed 1 mm. Therefore, it is necessary to find a suitable growth method for large-size NiP2 single crystals to meet applications in semiconductors, catalysis, and energy storage. Summary of the Invention

[0005] This invention aims to solve the technical problems of large-size single crystal growth. Therefore, the main objective of this invention is to provide a method for growing NiP2 crystals. By optimizing the heating method and employing an oscillating heating curve during the preparation of NiP2 single crystals, this method successfully grows large-size NiP2 single crystals, solving the technical difficulty of growing large-size NiP2 single crystals using traditional processes, and producing NiP2 single crystals with fewer defects and higher purity.

[0006] The specific technical solution is as follows:

[0007] A method for preparing NiP2 crystals, using NiP2 polycrystalline material and tin as raw materials, employs a fluxing method, and under vacuum sealing conditions, heats the material to an upper limit temperature, then uses oscillating heating, followed by cooling, to obtain NiP2 single crystals. The oscillating heating is set to 2 to 6 oscillation cycles, preferably 3 to 5 oscillation cycles, between 700 and 1100°C. One oscillation cycle includes: starting from the upper limit temperature - cooling down to the lower limit temperature - holding the temperature - heating up to the upper limit temperature - holding the temperature.

[0008] Furthermore, after heating to the upper limit temperature, the holding time is 24–48 hours;

[0009] Furthermore, the aforementioned oscillating heating has an upper limit temperature of 900–1080℃, a lower limit temperature of 700–800℃, a cooling rate of 90–150℃ / h, a heating rate of 60–100℃ / h, and a holding time of 0.5–1h at the upper and lower limit temperatures.

[0010] Furthermore, during the cooling process, crystal growth is controlled by controlling the cooling rate: when the cooling rate is 1–4 °C / h, the crystal shape is plate-like; when the cooling rate is 4–6 °C / h, the crystal shape is block-like; and when the cooling rate is 6–8 °C / h, the crystal shape is needle-like.

[0011] Furthermore, the molar ratio of NiP2 polycrystalline to tin is 1:6 to 1:26, preferably 1:16 to 1:18, and the purity of the tin is 99.9% to 99.999%.

[0012] Furthermore, the method includes the following steps:

[0013] (1) Take NiP2 polycrystalline material and tin into a container, evacuate and seal it;

[0014] (2) Place the above container in a high-temperature furnace, heat it to the upper limit temperature, and then use a oscillating heating method.

[0015] Then it is cooled.

[0016] Furthermore, the vacuum condition described in step (1) is 10. -3 Pa~10 -4 Pa.

[0017] Further, in step (2), the cooling process is carried out at 400-600°C; after the cooling is completed, the product is centrifuged and washed; the centrifugation speed is 1000-5000 r / min and the centrifugation time is 3-60 s; the washing method is washing with dilute hydrochloric acid solution for 0.5-24 h, and the mass concentration of dilute hydrochloric acid is 5-15%.

[0018] The NiP2 crystal prepared according to the method of the present invention has a monoclinic crystal structure, a space group of C2 / c, and lattice parameters of [missing information]. α=γ=90°, β=119.5615(8)°.

[0019] Furthermore, the preparation process of NiP2 polycrystalline material used in the preparation of NiP2 single crystal is as follows: Ni and P elements are weighed according to the stoichiometric ratio of NiP2, ground and cold-pressed, and then placed in a quartz tube and vacuum-sealed; the sealed quartz tube is then annealed in a high-temperature furnace; the purity of the elemental powder is 98.5–99.999%; during the cold-pressing process, the pressure is 100–600 MPa, and the holding time is 5–30 min; the vacuum condition is 10... -3 ~10 -4 Pa; the annealing treatment temperature is 900~1080℃, and the time is 12~50h.

[0020] Advantages of this invention:

[0021] This invention proposes a novel single-crystal growth technique, innovating upon the traditional flux-based crystal growth method, and introducing a technique for growing large-size NiP2 single crystals using an oscillating heating curve. By selecting tin as the flux and employing an oscillating heating curve and controlled cooling rate, high-quality and large-size NiP2 single crystals can be prepared.

[0022] This invention represents a significant innovation in crystal growth methods. It not only overcomes the shortcomings of small size and uncontrollable growth in NiP2 single crystal technology, but also greatly reduces the cost of NiP2 single crystal growth. This is of great significance for improving the growth technology of large-size crystals and even the development of semiconductor fabrication processes. Attached Figure Description

[0023] Figure 1 X-ray diffraction results for NiP2 polycrystalline material;

[0024] Figure 2 A schematic diagram of a container for flux-grown crystals;

[0025] Figure 3 The temperature change curve during the preparation of NiP2 crystals;

[0026] Figure 4 NiP2 crystals synthesized with fluxes of different proportions;

[0027] Figure 5 X-ray diffraction results for NiP2 single crystal;

[0028] Figure 6 This is a process flow diagram for NiP2 crystal growth;

[0029] Figure 7 A comparison of NiP2 crystals grown under normal heating curves and oscillating heating curves;

[0030] Figure 8 NiP2 crystals grown at different cooling rates;

[0031] Figure 9 NiP2 crystals prepared for different oscillation periods. Detailed Implementation

[0032] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] Synthesis of NiP2 polycrystalline materials.

[0035] (1) Weigh nickel powder and red phosphorus powder using an analytical balance. The nickel powder has a purity of 99.999% and a particle size of 250 mesh (i.e., passing through a 250-mesh sieve), with a mass of 0.2599g. The red phosphorus has a purity of 98.5% and a particle size of 100 mesh (i.e., passing through a 100-mesh sieve), with a mass of 0.2975g. Place the weighed nickel powder and red phosphorus powder in an agate mortar and mix them evenly for 30-60 minutes, specifically 40 minutes.

[0036] (2) Press the above mixture into small discs in a Φ12.7mm mold at a pressure of 500MPa for 10 minutes. Place the discs in a corundum crucible, then place the crucible in a quartz tube and seal it in a vacuum environment with a vacuum degree of 10. -4 Pa. The sealed quartz tube was placed in a muffle furnace for sintering, heated to 1080°C at a rate of 100°C / h, and then held at 1080°C for 24-48h, specifically 30h. Then it was cooled to room temperature in the furnace.

[0037] (3) Repeat the previous process, grinding the previously sintered sample in an agate mortar. After grinding, press it into small round discs in a Φ12.7mm mold at a pressure of 500MPa for 10 minutes. Place the small discs in a corundum crucible, then place the crucible in a quartz tube and seal it in a vacuum environment with a vacuum degree of 10. -4 Pa. The sealed quartz tube was placed in a muffle furnace for sintering, heated to 1080°C at a rate of 100°C / h, and then held at 1080°C for 24-48h, specifically 30h. Then it was cooled to room temperature in the furnace.

[0038] The above process step (3) is repeated twice. The sample sintered for the last time is placed in an agate mortar and ground for 1-3 hours, specifically 2 hours. The ground powder is then passed through a 400-mesh sieve (the powder passing through the sieve is collected). The diffraction data of the powder sample is then tested using a laboratory SmartLab small X-ray diffractometer. The sieved NiP2 powder is spread throughout the sample cell and flattened with a glass slide. The sample cell is then installed on the test stage, and the test parameters are set as follows: test angle 10-90°, step size 0.01°, and speed 1° / min. The diffraction data is analyzed and compared with the standard cards in the crystallography library. The results are as follows. Figure 1 As shown, the synthesized NiP2 polycrystalline powder was determined to be a pure phase with lattice parameters of [value missing]. α=γ=90°, β=119.5615(8)°.

[0039] Example 2

[0040] Flux ratio control for NiP2 crystal growth.

[0041] NiP2 polycrystalline powder and tin particles were weighed using an analytical balance. The NiP2 polycrystalline powder was synthesized in Example 1, and the tin particles had a purity of 99.999% and a particle size of 1–4 mm. The weighed masses of NiP2 polycrystalline powder and tin particles were 1.4484 g: 8.5517 g (molar ratio 1:6), 0.7807 g: 9.2195 g (molar ratio 1:12), 0.5972 g: 9.4023 g (molar ratio 1:16), 0.5344 g: 9.4658 g (molar ratio 1:18), 0.4835 g: 9.5169 g (molar ratio 1:20), and 0.3761 g: 9.6234 g (molar ratio 1:26), for a total of 6 sets of experiments. The weighed mixture was placed in a corundum crucible, then placed in a quartz glass tube, and sealed in a vacuum environment with a vacuum degree of 10. -4 Pa. For example. Figure 2 As shown, two corundum crucibles are placed mouth-to-mouth, with the lower crucible containing the mixture and the upper crucible stuffed with quartz wool. Quartz wool is also stuffed into the bottom and top of the quartz tube. The sealed quartz tube is placed in a muffle furnace and heated to 1080°C at a rate of 100°C / h, and held at 1080°C for 24-48 hours (specifically 30 hours in this case). Temperature oscillation is performed before crystal growth, as shown... Figure 3The oscillating heating zone shown uses oscillating heating to control the number of nuclei. The specific method is as follows: starting from 1080℃, the temperature is lowered to 800℃ at a rate of 100℃ / h, held for 30 minutes, then raised to 1080℃ at a rate of 100℃ / h, and held for 30 minutes. This process constitutes one cycle. After four cycles of temperature oscillation, the temperature is cooled to 500℃ at a rate of 3.6℃ / h. At 500℃, the quartz tube is removed and centrifuged at 3000 r / min. Timing begins when the rated speed is reached, and centrifugation lasts for 10 seconds. The NiP2 crystals are then picked out and soaked in 10% dilute hydrochloric acid for 3-6 hours (4 hours in this case). They are then dried in a vacuum drying oven at 100℃ for 1 hour. The NiP2 crystals synthesized with different molar ratios of NiP2 polycrystalline powder and tin particles are shown below. Figure 4 As shown, the size, quality, and shape of the single crystals were evaluated. At a ratio of 1:6, a large number of small crystals agglomerated into a blocky shape, with numerous grain boundaries present, requiring cleavage to obtain smaller single crystals, resulting in poor quality. At a ratio of 1:12, no agglomeration occurred, but the crystal size was small, generally needle-like, and of average quality. At a ratio of 1:16, the crystal size was large, the shape regular, and the quality good. At a ratio of 1:18, the crystal size was large, the shape regular, and the quality good. At a ratio of 1:20, the number of crystals was small, their size thin, and the quality average. At a ratio of 1:26, the number of crystals was low, they were generally thin flakes, and the quality average. Therefore, ratios of 1:16 and 1:18 were determined to be optimal. Single-crystal diffraction of NiP2 crystals was tested using a SmartLab mini X-ray diffractometer in the laboratory, and the results are as follows... Figure 5 As shown, the single-crystal diffraction peaks are steep and have a small full width at half maximum (FWHM), indicating that the single crystal is of very good quality.

[0042] Example 3

[0043] The growth of NiP2 crystals is controlled by an oscillating heating curve.

[0044] The preparation process of NiP2 single crystals is as follows: Figure 6 As shown, a mixture of NiP2 polycrystalline powder and tin particles was weighed according to the molar ratio of 1:18 as in Example 2. 0.5342 g of NiP2 polycrystalline powder and 9.4653 g of tin particles were weighed and placed in a corundum crucible. The crucible was then sealed in a vacuum environment with a vacuum degree of 10. -4 Pa. Sealing method as follows Figure 2 As shown in Example 2, the sealed quartz tube is placed in a muffle furnace and heated to 1000°C at a rate of 100°C / h, and held at 1000°C for 24-48 hours. Specifically, this is 30 hours. Temperature oscillation is performed before crystal growth, as shown in Example 2. Figure 3The oscillating heating zone shown uses oscillating heating to control the number of nuclei. The specific method is as follows: starting from 1000℃, the temperature is lowered to 800℃ at a rate of 100℃ / h, held for 30 minutes, then increased to 1000℃ at a rate of 100℃ / h, and held for 30 minutes. This process constitutes one cycle, and the temperature oscillation continues for four cycles. Then, the temperature is cooled to 500℃ at a rate of 3.6℃ / h. At 500℃, the quartz tube is removed and centrifuged at 3000 rpm. Timing begins when the rated speed is reached, and centrifugation lasts for 10 seconds. The NiP2 crystals are then picked out and soaked in 10% dilute hydrochloric acid for 3-6 hours (specifically 4 hours in this case). Finally, they are dried in a vacuum drying oven at 100℃ for 1 hour.

[0045] Example 4

[0046] The amount of NiP2 polycrystalline powder weighed was 0.5344 g, and the amount of tin particles weighed was 9.4656 g. The other preparation process was the same as in Example 3, except that after shaking and heating, the cooling rate was 2℃ / h.

[0047] Example 5

[0048] The amount of NiP2 polycrystalline powder weighed was 0.5343g and the amount of tin particles weighed was 9.4657g. The other preparation process was the same as in Example 3, except that after shaking and heating, the cooling rate was 4℃ / h.

[0049] Example 6

[0050] The amount of NiP2 polycrystalline powder weighed was 0.5345g and the amount of tin particles weighed was 9.4651g. The other preparation process was the same as in Example 3, except that after shaking and heating, the cooling rate was 7℃ / h.

[0051] Comparative Example 1

[0052] NiP2 crystals grown using conventional heating curves

[0053] 0.5342 g of NiP2 polycrystalline powder and 9.4653 g of tin particles were weighed and placed in a corundum crucible. The crucible was then sealed in a vacuum environment with a vacuum degree of 10. -4 Pa. The vacuum sealing method is the same as in Example 3. The sealed quartz tube is placed in a muffle furnace and heated to 1000°C at a rate of 100°C / h, and held at 1000°C for 24-48 hours, specifically 30 hours. Then it is cooled to 500°C at a rate of 3.6°C / h. At 500°C, the quartz tube is removed and centrifuged in a centrifuge at a speed of 3000 r / min. Timing starts when the speed reaches the rated speed, and centrifugation lasts for 10 seconds. The NiP2 crystals are picked out and soaked in 10% dilute hydrochloric acid for 3-6 hours, specifically 4 hours. Then it is dried in a vacuum drying oven at 100°C for 1 hour.

[0054] Figure 7 The crystals grown in Example 3 and Comparative Example 1 are shown, representing crystals grown using conventional heating and oscillating heating methods, respectively. Conventional heating involves direct cooling from a high temperature. Due to the difficulty in controlling the number of nuclei, a large number of nuclei grow, and these nuclei easily come into contact with each other during growth, thus limiting crystal growth. In Example 3, the oscillating heating method involves oscillation within the NiP2 nucleation temperature range. Although a large number of nuclei are generated during cooling, they melt during oscillation, and only a few that do not melt are retained and continue to grow during the final cooling process. The advantage of oscillating heating is that it allows for control over the number of nuclei, enabling a smaller number of nuclei to grow during cooling. This avoids crystal contact that restricts growth, resulting in more growth directions and the production of crystals with higher surface quality and larger sizes. Figure 7 Crystals grown using the oscillating heating curve can reach sizes of 6mm × 7mm × 1mm.

[0055] Figure 8 The figures show the shapes and sizes of NiP2 crystals grown at different cooling rates in Examples 4-6. At a cooling rate of 2℃ / h, the crystal size is 20mm × 13mm × 0.3mm; at a cooling rate of 4℃ / h, the crystal size is 2mm × 3mm × 1mm; and at a cooling rate of 7℃ / h, the crystal size is 1mm × 1mm × 10mm. The use of an oscillating heating curve allows a small number of crystal nuclei to be retained, reducing contact during crystal growth and decreasing crystal growth resistance. Therefore, the growth rate of crystals can be controlled by controlling the cooling rate. Crystal growth follows the temperature gradient direction and exhibits a preferred growth trend. The shape and size of the crystal can be controlled by controlling the cooling rate. The growth rate of crystals can be controlled by controlling the cooling rate. When the cooling rate is low, 1℃ / h to 4℃ / h, crystal growth is slow and the preferred growth trend is weak, which is conducive to the growth of large-area plate-shaped crystals. When the cooling rate is fast, 6℃ / h to 8℃ / h, the crystal growth rate is fast and the preferred growth trend is obvious, which is conducive to the growth of fine needle-shaped single crystals. When the cooling rate is moderate, 4℃ / h to 6℃ / h, the crystal grows isotropically, which is conducive to the growth of thicker bulk single crystals.

[0056] Comparative Example 2

[0057] The specific preparation process is the same as in Example 3, except that different oscillation heating cycles are set: 1, 2, 3, 5, 6, and 7 cycles respectively.

[0058] The prepared crystals are as follows Figure 9As shown, the crystals grown in one oscillation cycle are small in size and numerous in number, indicating that one oscillation cycle is too short and the change in the number of nuclei is not significant. The number of crystals grown in two oscillation cycles decreases significantly, while the crystal size increases, indicating that two oscillation cycles help reduce the number of nuclei. The number of crystals grown in three oscillation cycles decreases further, and the crystal size is larger than that of crystals grown in two oscillation cycles. The number of crystals grown in five and six oscillation cycles is found to be basically the same as that grown in four oscillation cycles, indicating that the number of crystals grown in four oscillation cycles has reached equilibrium, and the crystal size is the largest. Further increasing the oscillation cycle does not significantly improve crystal growth and may be applicable to other growth conditions. In the crystal preparation experiment with seven oscillation cycles, the quartz tube broke due to thermal fatigue, the vacuum environment was destroyed, and crystal growth could not proceed.

[0059] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method of producing a NiP2 crystal, characterized by: The method comprises the following steps: taking NiP2 polycrystal and tin in a container, vacuumizing and sealing; placing the container in a high-temperature furnace, heating to an upper limit temperature, and then performing oscillation heating, and then cooling.

2. The method of claim 1, wherein: The cooling process is controlled by controlling the cooling rate: when the cooling rate is 1-4 ℃ / h, the crystal shape is flaky; when the cooling rate is 4-6 ℃ / h, the crystal shape is blocky; and when the cooling rate is 6-8 ℃ / h, the crystal shape is needle-shaped.

3. The method of claim 1, wherein: The purity of the tin is 99.9%-99.999%.

4. The method according to any of claims 1 to 3, characterized in that: The method comprises the following steps: (1) taking NiP2 polycrystal and tin in a container, vacuumizing and sealing; (2) placing the container in a high-temperature furnace, heating to an upper limit temperature, and then performing oscillation heating, and then cooling.

5. The method of claim 4, wherein: The vacuum condition in step (1) is 10 -3 Pa 10 -4 Pa.

6. The method of claim 4, wherein: The cooling process in step (2) is cooling to 400-600 ℃; after the cooling is completed, the product is centrifuged and cleaned; the rotation speed of the centrifugation is 1000-5000 r / min, and the centrifugation time is 3-60 s; the cleaning method is dilute hydrochloric acid solution cleaning, the time is 0.5-24 h, and the mass concentration of the dilute hydrochloric acid is 5-15%.

7. The method of claim 1, wherein: The crystal structure of the NiP2 crystal is monoclinic structure, the space group is C2 / c, the lattice parameters are a=6.367697(57) Å, b=5.615907(53) Å, c=5.631185(54) Å, α=γ=90°, and β=119.5615(8)°.

8. The method of claim 1, wherein: The preparation process of the NiP2 polycrystal is as follows: Ni and P elements are weighed according to the stoichiometric ratio of NiP2, grinded and cold-pressed, and then placed in a quartz tube for vacuum sealing; the sealed quartz tube is placed in a high-temperature furnace for annealing treatment; the purity of the elemental powder is 98.5-99.999%; during the cold-pressing process, the pressure is 100-600 MPa, and the pressure maintaining time is 5-30 min; the vacuum condition is 10 -3 ~10 -4 Pa; the temperature of the annealing treatment is 900-1080 DEG C, and the time is 12-50 h.

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