Compound melamine hexafluoroaluminate and melamine chlorohexafluoroaluminate birefringent crystal and method of making and use

Abstract

This invention provides a compound melamine hexafluoroaluminate chloride and a birefringent crystal of melamine hexafluoroaluminate chloride, along with their preparation methods and uses. The compound has the chemical formula (C3N6H8)2AlF6‧Cl and a molecular weight of 432.74. The crystal also has the chemical formula (C3N6H8)2AlF6‧Cl and a molecular weight of 432.74, belonging to the monoclinic crystal system with space group [missing information]. P twenty one / c The unit cell parameters are a =10.305(4) Å, b =8.721(3) Å, c =8.828(3) Å, α =90°, β =106.655(12) °, gamma =90°, unit cell volume is 760.1(4) Å 3 Its light transmission range is 224–1600 nm, and its birefringence is between 0.34 (1064 nm) and 0.96 (224 nm). The crystal is grown using an aqueous solution evaporation method. This crystal has moderate mechanical hardness, is easy to cut, polish, and store, and the growth conditions are simple and easy to achieve. It is non-hygroscopic and stable in air. It possesses a large light transmission range and birefringence, and can be used to fabricate polarizing beam splitters, phase delay devices, and electro-optic modulation devices.

Description

Technical Field

[0001] This invention relates to a compound melamine hexafluoroaluminate and a birefringent crystal of melamine hexafluoroaluminate, as well as their preparation method and uses. Background Technology

[0002] Birefringent crystals are core materials for optical devices such as polarizing prisms, optical isolators, and phase retarders. Currently, practically applicable crystals all have significant shortcomings: natural calcite suffers from severe cleavage, making it prone to breakage during processing; rutile, while possessing high birefringence, has a short-wavelength cutoff of approximately 400 nm, rendering it unsuitable for ultraviolet and some visible light applications, and requires high-temperature flame fusion growth at temperatures above 1800 °C, resulting in extremely high energy consumption and a tendency for oxygen defects; yttrium vanadate requires high-temperature Czochralski growth, leading to high costs, and is prone to reduction at high temperatures, causing optical inhomogeneities; α-BBO is susceptible to phase transition cracking during growth, resulting in low yield; lithium niobate has a birefringence of only about 0.084@633 nm, making it insufficient for high extinction ratio polarization devices. These oxide crystals generally rely on harsh high-temperature growth conditions, resulting in long preparation cycles, high energy consumption, and high costs. Organic-inorganic hybrid systems offer a new approach for novel birefringent crystals. Fluoroaluminate octahedral units (such as AlF6) 3- Fluoroaluminate crystals possess high microscopic polarization anisotropy, and when combined with organic cations containing conjugated rings, their birefringence effect can be further amplified through hydrogen bond networks and layered stacking. However, currently reported organic-inorganic hybrid crystals containing fluoroaluminates either have low birefringence or limited transmission bands, and most are difficult to grow into macroscopic single crystals under mild conditions such as room temperature and pressure, severely limiting their practical applications. Therefore, there is an urgent need to develop a novel birefringent crystal that combines high birefringence, wide transmission band, excellent physicochemical stability, and can be grown into macroscopic crystals using isothermal processes such as low-temperature solution methods.

[0003] The melamine hexafluoroaluminate crystal synthesized in this invention, due to its large birefringence, can be used as a Glan prism, polarizing prism, polarizing beam splitter, optical isolator, circulator, beam shifter, optical polarizer, and optical modulator, etc. Summary of the Invention

[0004] The purpose of this invention is to provide a compound, melamine hexafluoroaluminate chloride, with the chemical formula (C3N6H8)2AlF6‧Cl and a molecular weight of 432.74, which is prepared by aqueous solution evaporation.

[0005] Another objective of this invention is to provide a birefringent crystal of melamine hexafluoroaluminate chloride, with the chemical formula (C3N6H8)2AlF6‧Cl, a molecular weight of 432.74, belonging to the monoclinic crystal system, and a space group of [missing information]. P twenty one / c The unit cell parameters are a=10.305(4) Å, b = 8.721(3) Å, c = 8.828(3) Å, α = 90°, β = 106.655(12) °, γ =90°, unit cell volume is 760.1(4) Å 3 .

[0006] Another objective of this invention is to provide a method for growing melamine hexafluoroaluminate birefringent crystals.

[0007] Another object of the present invention is to provide the use of melamine hexafluoroaluminate birefringent crystals for the manufacture of optical communication components such as Glan prisms, polarizing prisms, polarizing beam splitters, optical isolators, circulators, beam shifters, optical polarizers, and optical modulators.

[0008] The present invention discloses a compound, melamine hexafluoroaluminate chloride, with the chemical formula (C3N6H8)2AlF6‧Cl and a molecular weight of 432.74, which is prepared by aqueous solution evaporation.

[0009] The compound melamine hexafluoroaluminate is prepared by aqueous solution evaporation, and the specific operation is carried out according to the following steps: a. With a molar ratio of C3H6N6∶Al = 3∶2, add C3H6N6 and Al source materials to a polytetrafluoroethylene beaker containing 15 ml of deionized water, slowly add 5 ml of 40% hydrofluoric acid, stir until the solid is completely dissolved, then add 1 ml of hydrochloric acid, and stir at room temperature for 0.5 hours. The Al source materials are Al(OH)(CH3COO)2, Al(OH)3, and Al2O3. Alternatively, in a molar ratio of C3H6N6∶Al∶F = 3∶2∶6, add C3H6N6, Al source material, and F source material to a polytetrafluoroethylene beaker containing 10 ml of deionized water, slowly add 1 ml of hydrochloric acid, stir at room temperature for 0.5 hours, where the Al source material is (NH4)3AlF6 or Al(OH)3, and the F source material is (NH4)3AlF6 or NH4F; Alternatively, using a molar ratio of C3H6N6:Al = 3:2, add C3H6N6 and AlCl3 to a polytetrafluoroethylene beaker containing 5 ml of deionized water, dissolve them under ice bath cooling, slowly add 2 ml of 40% hydrofluoric acid, and stir at room temperature for 0.5 hours; Alternatively, using a molar ratio of C3H6N6∶Al:F = 3∶2:6, in a PTFE beaker, first add 10 mL of deionized water and pre-cool in an ice bath. Add 2.0 mmol of AlCl3 in small, repeated additions, stirring until completely dissolved after each addition. Maintaining the ice bath cooling, add 6.0 mmol of NH4F to the solution and stir until completely dissolved. Then add 3.0 mmol of C3H6N6 and stir at room temperature for 0.5 hours. Alternatively, using a molar ratio of C3H6N6∶Al = 3∶2, suspend 2.0 mmol Al(OH)3 in 10 mL of water in a polytetrafluoroethylene beaker, and add 3.0 mmol NH4F. Add 5 mL of 40% hydrofluoric acid dropwise under ice bath conditions, stir at room temperature for 0.5 hours, and after the solid dissolves, add 1 mL of hydrochloric acid and 3.0 mmol C3H6N6. Stir in a 50 °C water bath and purge with nitrogen to remove ammonia for 2 hours. b. Place the mixed solution obtained in step a on an intelligent temperature controller and perform evaporation treatment at a temperature of 40-60 ℃. After 5-10 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure.

[0010] A birefringent crystal of melamine hexafluoroaluminate chloride, with the chemical formula (C3N6H8)2AlF6‧Cl and a molecular weight of 432.74, belongs to the monoclinic crystal system and has a space group of [missing information]. P twenty one / c The unit cell parameters are a = 10.305(4) Å, b = 8.721(3) Å, c = 8.828(3) Å, α = 90°, β = 106.655(12) °, γ = 90°, unit cell volume is 760.1(4) Å 3 .

[0011] The method for preparing the melamine hexafluoroaluminate birefringent crystal involves growing the crystal using an aqueous solution evaporation method, and the specific operation is carried out according to the following steps: a. With a molar ratio of C3H6N6:Al = 2:1, add the Al source material to a polytetrafluoroethylene beaker containing 100 ml of deionized water, and slowly add 25 ml of 40% hydrofluoric acid, 10 ml of hydrochloric acid and 20 mmol of C3H6N6 in sequence. Stir magnetically for 1-2 hours, and filter with filter paper to obtain a clear solution. The Al source materials are Al(OH)(CH3COO)2, Al(OH)3 and Al2O3. Alternatively, in a molar ratio of C3H6N6∶Al∶F = 2∶1∶6, add C3H6N6, Al source material, and F source material to a polytetrafluoroethylene beaker containing 100 ml of deionized water, slowly add 10 ml of hydrochloric acid, stir at room temperature for 1 hour, and filter to obtain a clear solution, wherein the Al source material is (NH4)3AlF6 or Al(OH)3, and the F source material is (NH4)3AlF6 or NH4F; Alternatively, using a molar ratio of C3H6N6∶Al = 2∶1, add 10.0 mmol of AlCl3 to a polytetrafluoroethylene beaker, dissolve it in 50 mL of deionized water under ice bath cooling, slowly add 25 mL of 40% hydrofluoric acid, stir until clear, add 20.0 mmol of C3H6N6, stir magnetically for 1.5 hours, and filter to obtain a clear solution; Alternatively, using a molar ratio of C3H6N6∶Al:F = 2∶1:6, add 100 mL of deionized water to a polytetrafluoroethylene beaker and pre-cool it in an ice bath. Add 10.0 mmol of AlCl3 in small portions, stirring until completely dissolved after each addition, and then add the next amount. Keep the solution cool in an ice bath. Add 60.0 mmol of NH4F to the solution and stir until completely dissolved. Then add 20.0 mmol of C3H6N6 and stir at room temperature for 2 hours. Filter to obtain a clear solution. Alternatively, in a molar ratio of C3H6N6∶Al = 2∶1, 10.0 mmol Al(OH)3 is suspended in 100 mL of water in a polytetrafluoroethylene beaker, 30.0 mmol NH4F is added, and 25 mL of 40% hydrofluoric acid is added dropwise under ice bath conditions. After the solid dissolves, 10 mL of hydrochloric acid and 20.0 mmol C3H6N6 are added, the mixture is stirred for 1.5 hours, and nitrogen gas is passed through to remove ammonia for 30 minutes. A small amount of insoluble matter is removed with filter paper to obtain a clear solution. b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles grow at the bottom of the container from the solution in step b, cool the solution to room temperature at a rate of 2-5 ℃ / day or keep it at a constant temperature of 25-35 ℃ for 10-30 days. Once the crystals continue to grow and their size does not change significantly, the growth is complete. Filter the solution containing the crystals to obtain melamine hexafluoroaluminate birefringent crystals.

[0012] The use of the melamine hexafluoroaluminate birefringent crystal in the preparation of circulators, optical isolators, optical polarizers, optical modulators or beam shifters.

[0013] The optical polarizer is a polarizing beam splitter prism.

[0014] The polarizing beam splitter is a Lochtein prism, a Wollaston prism, or a Glan prism.

[0015] The melamine hexafluoroaluminate birefringent crystal of this invention is synthesized by an aqueous solution evaporation method, and the melamine hexafluoroaluminate birefringent crystal is grown by the aqueous solution evaporation method. The chemical reaction formula is as follows: (1) Al(OH)(CH3COO)2 + 6HF + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 2CH3COOH+ H2O (2) Al(OH)3 + 6HF + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3H2O (3) Al2O3 + 12HF + 4C3N6H6 + 2HCl → 2(C3N6H8)2AlF6·Cl + 3H2O (4) (NH4)3AlF6 + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3NH3↑ (5) AlCl3 + 6HF + 2C3N6H6 → (C3N6H8)2AlF6·Cl + 2HCl↑ (6) AlCl3 + 6NH4F + 2C3N6H6 → (C3N6H8)2AlF6·Cl + 2HCl↑+ 6NH3↑ (7) Al(OH)3 + 3HF + 3NH4F + 2C3N6H6 + HCl →(C3N6H8)2AlF6·Cl + 3NH3↑ +3H2O (8) Al(OH)3+ 6NH4F + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl+ 3NH3↑ +3H2O The melamine hexafluoroaluminate birefringent crystal of the present invention is used in the infrared-ultraviolet band, with a transmission range of 224-1600 nm and a birefringence between 0.34 (1064 nm) and 0.96 (224 nm).

[0016] The melamine hexafluoroaluminate birefringent crystal described in this invention has the chemical formula (C3N6H8)2AlF6‧Cl and a molecular weight of 432.74, belonging to the monoclinic crystal system. P twenty one / c The unit cell parameters are a = 10.305(4) Å, b = 8.721(3) Å, c =8.828(3) Å, α = 90°, β = 106.655(12) °, γ = 90°, unit cell volume is 760.1(4) Å 3 Its transmission range is 224-1600 nm, and its birefringence is between 0.34 (1064 nm) and 0.96 (224 nm). The crystal is easy to grow, cut, grind, polish, and store; it is grown using an aqueous solution evaporation method. The obtained crystal is stable in air. It can be used to fabricate polarizing beam splitters such as Glan prisms, Wollaston prisms, Lochte prisms, or beam splitters, and has important applications in optics and communications. Attached Figure Description

[0017] Figure 1 The powder XRD pattern of the compound (C3N6H8)2AlF6‧Cl of this invention; Figure 2 This is a structural diagram of the (C3N6H8)2AlF6‧Cl crystal of the present invention; Figure 3 This is the UV-Vis diffuse reflectance image of the (C3N6H8)2AlF6‧Cl crystal of this invention; Figure 4 This is a graph showing the birefringence calculation of (C3N6H8)2AlF6‧Cl according to the present invention. Figure 5 This is a schematic diagram of a beam shifter fabricated from a crystal grown by the method of the present invention, where 1 is the incident light, 2 is the o-ray, 3 is the e-ray, 4 is the optical axis, 5 is a melamine hexafluoroaluminate (C3N6H8)2AlF6‧Cl birefringent crystal, 6 is the light transmission direction, and 7 is the optical axis plane. Figure 6 This is a schematic diagram of the optical isolator of the present invention; Figure 7This is a schematic diagram of the wedge-shaped birefringent crystal polarization beam splitter of the present invention, where 1 is the incident light, 2 is the o-ray, 3 is the e-ray, 4 is the optical axis, and 5 is a melamine hexafluoroaluminate (C3N6H8)2AlF6‧Cl birefringent crystal. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments. It should be noted that the following embodiments are not intended to limit the scope of protection of the present invention, and any improvements made based on the present invention do not depart from the spirit of the present invention. Unless otherwise specified, the raw materials or equipment used in the present invention are commercially available. Example 1

[0019] The compound was prepared according to reaction formula (1): Al(OH)(CH3COO)2 + 6HF + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl +2CH3COOH + H2O. a. In a polytetrafluoroethylene beaker, weigh 2.0 mmol (324 mg) of basic aluminum acetate and 3.0 mmol (378 mg) of melamine, add 15 mL of deionized water and stir to disperse, slowly add 5 mL of 40% hydrofluoric acid, the solid gradually dissolves, add 1 mL of hydrochloric acid while stirring, and stir at room temperature for 0.5 hours. b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 60 °C. After 5 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure. Example 2

[0020] The compound was prepared according to reaction (2): Al(OH)3 + 6HF + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3H2O. a. In a polytetrafluoroethylene beaker, 2.0 mmol (156 mg) of aluminum hydroxide and 3.0 mmol (378 mg) of melamine were added to 15 mL of deionized water and stirred to form a suspension. 5 mL of 40% hydrofluoric acid was slowly added dropwise, and the solid gradually dissolved. Then 1 mL of hydrochloric acid was added, and the mixture was stirred at room temperature for 0.5 hours. b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 40 °C. After 10 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure. Example 3

[0021] The compound was prepared according to reaction (3): Al2O3 + 12HF + 4C3N6H6 + 2HCl → 2(C3N6H8)2AlF6·Cl + 3H2O. a. In a polytetrafluoroethylene beaker, weigh 1 mmol (102 mg) of alumina powder and 3.0 mmol (378 mg) of melamine, mix with 15 mL of deionized water to form a slurry, add 5 mL of 40% hydrofluoric acid dropwise, then add 1 mL of hydrochloric acid, stir at room temperature for 0.5 hours to obtain a clear solution. b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 60 °C. After 5 days, a polycrystalline powder sample of the target compound, melamine hexafluoroaluminate chloride, is obtained, which can be used for X-ray single-crystal diffraction to determine its crystal structure. Example 4

[0022] The compound was prepared according to reaction (4): (NH4)3AlF6 + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3NH3↑. a. In a polytetrafluoroethylene beaker, add 2.0 mmol (396 mg) ammonium hexafluoroaluminate and 3.0 mmol melamine, add 10 mL of deionized water, add 1 mL of hydrochloric acid while stirring, and stir for 0.5 hours to obtain a clear solution; b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 50 °C. After 8 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure. Example 5

[0023] The compound was prepared according to reaction (5): AlCl3 + 6HF + 2C3N6H6 → (C3N6H8)2AlF6·Cl + 2HCl↑. a. In a fume hood, carefully add 2.0 mmol (266 mg) of anhydrous aluminum trichloride and 3.0 mmol of melamine to a polytetrafluoroethylene beaker, and dissolve them in 5 mL of deionized water under ice bath cooling. Slowly add 2 mL of 40% hydrofluoric acid, and stir for 0.5 hours to obtain a suspension. HCl gas is released during the process. b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 60 °C. After 5 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure. Example 6

[0024] The compound was prepared according to reaction (6): AlCl3 + 6NH4F + 2C3N6H6 → (C3N6H8)2AlF6·Cl + 2HCl↑ + 6NH3↑. a. In a fume hood, first add 10 mL of deionized water and pre-cool in an ice bath. Add 2.0 mmol (266 mg) of anhydrous aluminum chloride in small, repeated additions, stirring until completely dissolved after each addition. Keeping the solution cooled in the ice bath, add 6.0 mmol (222 mg) of ammonium fluoride and stir until completely dissolved. Then add 3.0 mmol (378 mg) of melamine and stir at room temperature for 0.5 hours. b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 50 °C. After 8 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure. Example 7

[0025] The compound was prepared according to reaction (7): Al(OH)3 + 3HF + 3NH4F + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3NH3↑ + 3H2O. a. In a polytetrafluoroethylene beaker, 2.0 mmol (156 mg) of aluminum hydroxide was suspended in 10 mL of water, and 3.0 mmol (111 mg) of ammonium fluoride solid was added. 5 mL of 40% hydrofluoric acid was added dropwise under ice bath conditions, and the mixture was stirred at room temperature for 0.5 hours. After the solid dissolved, 1 mL of hydrochloric acid and 3.0 mmol of melamine were added. The mixture was stirred in a 50 °C water bath and nitrogen was purged to remove ammonia for 2 hours to obtain a clear solution. b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 50 °C. After 7 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure. Example 8

[0026] The compound was prepared according to reaction (8): Al(OH)3 + 6NH4F + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3NH3↑ + 3H2O. a. In a 100 mL polytetrafluoroethylene beaker, weigh 2.0 mmol (156 mg) aluminum hydroxide, 6.0 mmol (222 mg) ammonium fluoride, and 3.0 mmol (378 mg) melamine. Add 10 mL of deionized water and stir to disperse, forming a white suspension. Then, slowly add 1 mL of concentrated hydrochloric acid. The system becomes almost completely transparent. Continue stirring at room temperature for 0.5 hours to obtain a pale yellow clear solution.

[0027] b. Place the mixed solution obtained in step a on a smart temperature controller and evaporate it at 50 °C. After 7 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure. Example 9

[0028] Crystals were grown using the aqueous solution evaporation method according to reaction formula (1): Al(OH)(CH3COO)2 + 6HF + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl +2CH3COOH + H2O. a. In a polytetrafluoroethylene beaker, 10 mmol (1.62 g) of basic aluminum acetate was dispersed in 100 mL of deionized water. Under ice bath conditions, 60 mmol of 40% hydrofluoric acid, 10 mmol of hydrochloric acid and 20 mmol (2.52 g) of melamine were slowly added in sequence. After stirring magnetically for 1 hour, the solution was filtered through filter paper to obtain a clear solution. b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the solution is cooled to room temperature at a rate of 5 °C / day and held at this temperature for 20 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 2.1 × 2.8 × 1.5 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 10

[0029] According to reaction (2): Al(OH)3 + 6HF + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3H2O, crystals are grown using the aqueous solution evaporation method. a. In a polytetrafluoroethylene beaker, weigh 10 mmol (0.78 g) of aluminum hydroxide, add 100 mL of water, and slowly add 25 mL of 40% hydrofluoric acid and 10 mL of hydrochloric acid while stirring continuously. After complete dissolution, add 20 mmol (2.52 g) of melamine and stir magnetically for 2 hours to ensure the reaction is complete. Filter with filter paper to obtain a clear solution. b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the temperature is lowered to 30°C at a rate of 3°C / day and held at this temperature for 20 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 1.6 × 2.2 × 1.5 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 11

[0030] According to reaction formula (3): Al2O3 + 12HF + 4C3N6H6 + 2HCl → 2(C3N6H8)2AlF6·Cl + 3H2O, crystals are grown using the aqueous solution evaporation method. a. In a polytetrafluoroethylene beaker, add 5 mmol (0.51 g) of alumina, 25 ml of 40% hydrofluoric acid, 10 ml of hydrochloric acid and 20 mmol (2.52 g) of melamine in sequence, add 100 mL of water, stir magnetically for 1.5 hours, filter with filter paper to obtain a clear solution; b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the temperature is lowered to room temperature at a rate of 3 °C / day for 10 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 2.3 × 1.8 × 2.1 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 12

[0031] According to reaction (4): (NH4)3AlF6 + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3NH3↑, crystals are grown using the aqueous solution evaporation method. a. Weigh 10 mmol (1.95 g) ammonium hexafluoroaluminate and 20 mmol (2.52 g) melamine into a polytetrafluoroethylene beaker, add 100 mL of water, add 10 mL of hydrochloric acid while stirring, stir for 1 hour, filter with filter paper to obtain a clear solution; b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the temperature is lowered to room temperature at a rate of 2 °C / day and held constant for 25 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 1.3 × 2.7 × 2.2 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 13

[0032] According to reaction (5): AlCl3 + 6HF + 2C3N6H6 → (C3N6H8)2AlF6·Cl + 2HCl↑, crystals are grown using the aqueous solution evaporation method. a. In a fume hood, carefully add 10.0 mmol (1.33 g) of anhydrous aluminum trichloride to a polytetrafluoroethylene beaker, dissolve it in 50 mL of deionized water under ice bath cooling, slowly add 25 mL of 40% hydrofluoric acid, stir until clear, add 20.0 mmol (2.52 g) of melamine, stir magnetically for 1.5 hours, during which HCl gas is released, filter to obtain a clear solution; b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the temperature is lowered to 30°C at a rate of 5°C / day and held at this temperature for 10 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 1.3 × 2.5 × 1.6 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 14

[0033] According to reaction (6): AlCl3 + 6NH4F + 2C3N6H6 → (C3N6H8)2AlF6·Cl + 2HCl↑ + 6NH3↑, crystals are grown using the aqueous solution evaporation method. a. In a fume hood, first add 100 mL of deionized water and pre-cool it in an ice bath. Add 10.0 mmol (1.33 g) of anhydrous aluminum chloride in small portions, stirring until completely dissolved after each addition before adding the next batch. Keep the solution cooled in an ice bath. Add 60.0 mmol (2.22 g) of ammonium fluoride to the solution and stir until completely dissolved. Then add 20.0 mmol (2.52 g) of melamine and stir at room temperature for 2 hours. Filter to obtain a clear solution. b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the temperature is reduced to 30°C at a rate of 3°C / day and held constant for 20 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 1.2 × 2.5 × 2.3 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 15

[0034] According to reaction formula (7): Al(OH)3 + 3HF + 3NH4F + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3NH3↑ + 3H2O, crystals are grown using the aqueous solution evaporation method. a. In a polytetrafluoroethylene beaker, 10.0 mmol (0.78 g) of aluminum hydroxide was suspended in 100 mL of water, and 30.0 mmol (1.11 g) of ammonium fluoride solid was added. 25 mL of 40% hydrofluoric acid was added dropwise under ice bath. After the solid dissolved, 10 mL of hydrochloric acid and 20.0 mmol of melamine were added. The mixture was stirred for 1.5 hours and nitrogen gas was passed through to remove ammonia for 30 minutes. A small amount of insoluble matter was removed with filter paper to obtain a clear solution. b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the solution is cooled to room temperature at a rate of 4 °C / day for 20 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 1.6 × 2.8 × 1.1 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 16

[0035] According to reaction formula (8): Al(OH)3 + 6NH4F + 2C3N6H6 + HCl → (C3N6H8)2AlF6·Cl + 3NH3↑ + 3H2O, crystals are grown using the aqueous solution evaporation method. a. In a polytetrafluoroethylene beaker, weigh 20.0 mmol (2.52 g) of melamine, 10.0 mmol (0.78 g) of aluminum hydroxide and 60.0 mmol (2.22 g) of ammonium fluoride and add 100 mL of deionized water and stir to disperse, forming a white suspension. Slowly add 10 mL of hydrochloric acid while stirring, and the system becomes almost completely transparent. Continue stirring at room temperature for 1 hour, and filter to obtain a clear solution. b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles have grown at the bottom of the container from the solution in step b, the temperature is lowered to 30°C at a rate of 4°C / day and held at this temperature for 25 days. Once the crystals continue to grow without significant change in size, growth is complete. The solution containing the crystals is then filtered to obtain large, transparent crystals measuring 3.1 × 3.6 × 2.3 mm. 3 Melamine hexafluoroaluminate birefringent crystal. Example 17

[0036] The arbitrary melamine hexafluoroaluminate birefringent crystals obtained in Examples 9-16 were used to prepare beam shifters (such as...). Figure 5 As shown), a beam shifter is fabricated by machining a birefringent crystal such that its optical axis plane forms an angle θ with the edge, as shown. Figure 5 As shown in a; when natural light is incident perpendicularly, it can be split into two linearly polarized beams with mutually perpendicular vibration directions, such as Figure 5 As shown in b, the o-ray and e-ray are respectively. The greater the birefringence, the farther the two beams can be separated, which facilitates beam separation. Example 18

[0037] The melamine hexafluoroaluminate birefringent crystals obtained in Examples 9-16 were used to prepare optical isolators (such as...). Figure 6 As shown, an optical isolator is formed by placing a Faraday rotator that can rotate the polarization plane of the incident beam by 45° between a pair of birefringent crystal deflectors placed at 45° angles to each other. It only allows the forward-propagating beam to pass through the system, while blocking the backward-propagating beam. Figure 6 'a' indicates that the incident light beam can pass through. Figure 6 b indicates that the reflected light is blocked. Example 19

[0038] The melamine hexafluoroaluminate birefringent crystals obtained in Examples 9-16 were used to prepare wedge-shaped birefringent crystal polarization beam splitters (such as...). Figure 7 As shown), a wedge-shaped birefringent crystal, with its optical axis oriented as follows. Figure 7 As shown, a beam of natural light can be split into two linearly polarized beams after passing through a crystal. The greater the birefringence, the farther the two beams can be separated, which facilitates the separation of the beams.

Claims

1. A compound melamine hexafluoroaluminic chloride, characterized by The compound has the chemical formula (C3N6H8)2AlF6‧Cl and a molecular weight of 432.

74. It was prepared by aqueous solution evaporation.

2. A process for the preparation of the compound melamine hexafluoroaluminic chloride as claimed in claim 1, characterized in that It is prepared by aqueous solution evaporation, and the specific operation is carried out according to the following steps: a. With a molar ratio of C3H6N6∶Al = 3∶2, add C3H6N6 and Al source materials to a polytetrafluoroethylene beaker containing 15 ml of deionized water, slowly add 5 ml of 40% hydrofluoric acid, stir until the solid is completely dissolved, then add 1 ml of hydrochloric acid, and stir at room temperature for 0.5 hours. The Al source materials are Al(OH)(CH3COO)2, Al(OH)3, and Al2O3. Alternatively, in a molar ratio of C3H6N6∶Al∶F = 3∶2∶6, add C3H6N6, Al source material, and F source material to a polytetrafluoroethylene beaker containing 10 ml of deionized water, slowly add 1 ml of hydrochloric acid, stir at room temperature for 0.5 hours, where the Al source material is (NH4)3AlF6 or Al(OH)3, and the F source material is (NH4)3AlF6 or NH4F; Alternatively, using a molar ratio of C3H6N6:Al = 3:2, add C3H6N6 and AlCl3 to a polytetrafluoroethylene beaker containing 5 ml of deionized water, dissolve them under ice bath cooling, slowly add 2 ml of 40% hydrofluoric acid, and stir at room temperature for 0.5 hours; Alternatively, using a molar ratio of C3H6N6∶Al:F = 3∶2:6, in a PTFE beaker, first add 10 mL of deionized water and pre-cool in an ice bath. Add 2.0 mmol of AlCl3 in small, repeated additions, stirring until completely dissolved after each addition. Maintaining the ice bath cooling, add 6.0 mmol of NH4F to the solution and stir until completely dissolved. Then add 3.0 mmol of C3H6N6 and stir at room temperature for 0.5 hours. Alternatively, using a molar ratio of C3H6N6∶Al = 3∶2, suspend 2.0 mmol Al(OH)3 in 10 mL of water in a polytetrafluoroethylene beaker, and add 3.0 mmol NH4F. Add 5 mL of 40% hydrofluoric acid dropwise under ice bath conditions, stir at room temperature for 0.5 hours, and after the solid dissolves, add 1 mL of hydrochloric acid and 3.0 mmol C3H6N6. Stir in a 50 °C water bath and purge with nitrogen to remove ammonia for 2 hours. b. Place the mixed solution obtained in step a on an intelligent temperature controller and perform evaporation treatment at a temperature of 40-60 ℃. After 5-10 days, a polycrystalline powder sample of the target compound melamine hexafluoroaluminate chloride is obtained, which can be used for X-ray single crystal diffraction to determine its crystal structure.

3. A melamine hexafluoroaluminate birefringent crystal, characterized in that: The crystal has a chemical formula of (C3N6H8)2AlF6·Cl, a molecular weight of 432.74, belongs to a monoclinic system, and a space group of P 21 / c , a unit cell parameter of a = 10.305(4) Å, b = 8.721(3) Å, c = 8.828(3) Å, α = 90 °, β = 106.655(12) °, γ = 90 °, and a unit cell volume of 760.1(4) Å 3 .

4. A method for preparing a melamine hexafluoroaluminate birefringent crystal as described in claim 3, characterized in that... The birefringent crystals of melamine hexafluoroaluminate chloride were grown using the aqueous solution evaporation method. The specific operation was carried out according to the following steps: a. With a molar ratio of C3H6N6:Al = 2:1, add the Al source material to a polytetrafluoroethylene beaker containing 100 ml of deionized water, and slowly add 25 ml of 40% hydrofluoric acid, 10 ml of hydrochloric acid and 20 mmol of C3H6N6 in sequence. Stir magnetically for 1-2 hours, and filter with filter paper to obtain a clear solution. The Al source materials are Al(OH)(CH3COO)2, Al(OH)3 and Al2O3. Alternatively, in a molar ratio of C3H6N6∶Al∶F = 2∶1∶6, add C3H6N6, Al source material, and F source material to a polytetrafluoroethylene beaker containing 100 ml of deionized water, slowly add 10 ml of hydrochloric acid, stir at room temperature for 1 hour, and filter to obtain a clear solution, wherein the Al source material is (NH4)3AlF6 or Al(OH)3, and the F source material is (NH4)3AlF6 or NH4F; Alternatively, using a molar ratio of C3H6N6∶Al = 2∶1, add 10.0 mmol of AlCl3 to a polytetrafluoroethylene beaker, dissolve it in 50 mL of deionized water under ice bath cooling, slowly add 25 mL of 40% hydrofluoric acid, stir until clear, add 20.0 mmol of C3H6N6, stir magnetically for 1.5 hours, and filter to obtain a clear solution; Alternatively, using a molar ratio of C3H6N6∶Al:F = 2∶1:6, add 100 mL of deionized water to a polytetrafluoroethylene beaker and pre-cool it in an ice bath. Add 10.0 mmol of AlCl3 in small portions, stirring until completely dissolved after each addition, and then add the next amount. Keep the solution cool in an ice bath. Add 60.0 mmol of NH4F to the solution and stir until completely dissolved. Then add 20.0 mmol of C3H6N6 and stir at room temperature for 2 hours. Filter to obtain a clear solution. Alternatively, in a molar ratio of C3H6N6∶Al = 2∶1, 10.0 mmol Al(OH)3 is suspended in 100 mL of water in a polytetrafluoroethylene beaker, 30.0 mmol NH4F is added, and 25 mL of 40% hydrofluoric acid is added dropwise under ice bath conditions. After the solid dissolves, 10 mL of hydrochloric acid and 20.0 mmol C3H6N6 are added, the mixture is stirred for 1.5 hours, and nitrogen gas is passed through to remove ammonia for 30 minutes. A small amount of insoluble matter is removed with filter paper to obtain a clear solution. b. Transfer the clear solution obtained in step a to a crystallizing dish, seal it with plastic wrap, and poke several small holes in the plastic wrap. Place the crystallizing dish in an electric thermostatic drying oven at 60°C for constant temperature evaporation treatment. c. After crystal particles grow at the bottom of the container from the solution in step b, cool the solution to room temperature at a rate of 2-5 ℃ / day or keep it at a constant temperature of 25-35 ℃ for 10-30 days. Once the crystals continue to grow and their size does not change significantly, the growth is complete. Filter the solution containing the crystals to obtain melamine hexafluoroaluminate birefringent crystals.

5. The use of the melamine hexafluoroaluminate birefringent crystal according to claim 3 in the preparation of circulators, optical isolators, optical polarizers, optical modulators or beam shifters.

6. The use according to claim 5, characterized in that... The optical polarizer is a polarizing beam splitter prism.

7. The use according to claim 6, characterized in that... The polarizing beam splitter is a Lochtein prism, a Wollaston prism, or a Glan prism.

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