Series of compounds methyltrifluoroborate and nonlinear optical crystal of methyltrifluoroborate and preparation method and use thereof

Abstract

The present application relates to a series of compounds methyl trifluoroborate and methyl trifluoroborate nonlinear optical crystal and preparation method and use, the molecular general formula of the series of compounds is A3[CH3BF3]X2, wherein A=NH4, K, Rb, Cs, X=[NO3], Cl, Br, the molecular weight is 207.86-641.37, top seed method is prepared, orthorhombic system, space group Cmc 21 (No.36), the cell parameter is a=11.9141 (17)-12.6254 (2) Å, b=8.1556 (12)-8.4654 (17) Å, c=10.9621 (14)-11.5625 (15) Å, α =90, β =90, γ =90, Z =4, V=1065.2 (3)-1261.9 (1) Å 3 The series of compounds methyl trifluoroborate nonlinear optical crystal obtained by the method has the advantages of wide light transmission waveband, stable physical and chemical properties, moderate mechanical hardness, not easy to break, easy to cut, polish processing and preservation and the like.

Description

Technical Field

[0001] This invention relates to a series of compounds, methyltrifluoroborate and methyltrifluoroborate nonlinear optical crystals, their preparation methods and uses. Background Technology

[0002] Ultraviolet nonlinear optical materials are key materials for generating coherent ultraviolet light in solid-state lasers. To obtain nonlinear optical materials with nonlinear optical properties, the commonly used international method is to introduce nonlinear optical functional units that easily cause distortion into the structure. These units mainly contain d... 0 d 10 Transition metal cation polyhedra or metal cation polyhedra containing lone pairs of electrons have electronic structures. However, these structural units often cause a redshift of the ultraviolet cutoff edge, making them unsuitable for use in the ultraviolet region. Borates, on the other hand, are characterized by their ability to transmit ultraviolet radiation. Many excellent nonlinear optical crystals have been discovered among borates, such as BBO (β-BBO), LBO (LiB3O5), CBO (CsB3O5), and CLBO (CsLiB6O5). 10 Nonlinear optical crystals include KBBF (KBe₂BO₃F₂) crystals. Although the crystal growth techniques for these materials have become increasingly mature, they still have significant drawbacks: such as hygroscopicity, long growth cycles, severe layered growth habits, and high cost. Therefore, synthesizing new nonlinear optical crystal materials remains a very important and challenging task.

[0003] When developing new ultraviolet nonlinear optical crystals, people still choose borate crystals with a wide transmission range and a large laser damage threshold. In order to further broaden the transmission range and make its ultraviolet cutoff edge reach the deep ultraviolet, cations are usually alkali metals or alkaline earth metals without dd electron transitions, and fluoride ions are introduced into the borate framework. Summary of the Invention

[0004] The present invention aims to provide a series of methyltrifluoroborate compounds with the general molecular formula A3[CH3BF3]X2, wherein A = NH4, K, Rb, Cs, and molecular weights ranging from 162.88 to 277.75, prepared using the top-seeded crystal method. Another objective of the present invention is to provide a series of methyltrifluoroborate compounds A3[CH3BF3]X2 nonlinear optical crystals, wherein A = NH4, K, Rb, Cs, X = [NO3], Cl, Br, lacking a center of symmetry, orthorhombic crystal system, space group Cmc21 (No. 36), and cell parameters: 1)(NH4)3[CH3BF3][NO3]2. α=90, β=90, γ=90, Z=4, 2) K3[CH3BF3][NO3]2: α=90, β=90, γ=90, Z=4, 3)Rb3[CH3BF3][NO3]2: α=90, β=90, γ=90, Z=4, 4) Cs3[CH3BF3][NO3]2: α=90, β=90, γ=90, Z=4, 5)(NH4)3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 6) K3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 7) Rb3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 8) Cs3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 9)(NH4)3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4, 10) K3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4, 11) Rb3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4, 11) Cs3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4,

[0005] Another objective of this invention is to provide a method for preparing a series of methyltrifluoroborate nonlinear optical crystals, using a top seed crystal method to grow the crystals.

[0006] Another object of the present invention is to provide the use of a series of methyltrifluoroborate A3[CH3BF3]X2 nonlinear optical crystals.

[0007] The present invention discloses a series of compounds, methyltrifluoroborates, with the general molecular formula A3[CH3BF3]X2, wherein A = NH4, K, Rb, Cs, X = [NO3], Cl, Br, and molecular weights ranging from 207.86 to 641.37, prepared by the top seed crystal method.

[0008] A series of methyltrifluoroborate nonlinear optical crystals, with the general molecular formula A3[CH3BF3]X2, where A = NH4, K, Rb, Cs, and X = [NO3], Cl, Br, lacking a center of symmetry, orthorhombic crystal system, space group Cmc21 (No. 36), and cell parameters: 1)(NH4)3[CH3BF3][NO3]2: α=90, β=90, γ=90, Z=4, 2) K3[CH3BF3][NO3]2: α=90, β=90, γ=90, Z=4, 3)Rb3[CH3BF3][NO3]2: α = 90,

[0009] β = 90, γ = 90, Z = 4 4) Cs3[CH3BF3][NO3]2:

[0010] α=90, β=90, γ=90, Z=4, 5)(NH4)3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 6) K3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 7) Rb3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 8) Cs3[CH3BF3]Cl2: α=90, β=90, γ=90, Z=4, 9)(NH4)3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4, 10) K3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4, 11) Rb3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4, 11) Cs3[CH3BF3]Br2: α=90, β=90, γ=90, Z=4,

[0011] The method for preparing the aforementioned series of methyltrifluoroborate nonlinear optical crystals employs a top-seeded crystal method, and the specific operation is carried out according to the following steps:

[0012] a. Mix the fluorinated compound and methylboric acid at a molar ratio of 1.5-3.5:1 until homogeneous, add 0-50 mL of deionized water to fully mix and dissolve, and obtain a mixed solution. The fluorinated compound is ammonium hydrofluoride, potassium hydrofluoride, rubidium hydrofluoride, cesium hydrofluoride, ammonium tetrafluoroborate, potassium tetrafluoroborate, rubidium tetrafluoroborate, or cesium tetrafluoroborate.

[0013] b. Keep the mixed solution from step a at a constant temperature for 2-5 days until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, take out the crystals and place them on filter paper to dry, thus obtaining a series of compounds containing methyltrifluoroborate, namely ammonium methyltrifluoroborate, potassium methyltrifluoroborate, rubidium methyltrifluoroborate or cesium methyltrifluoroborate.

[0014] c. Mix the methyltrifluoroboric acid compound obtained in step b with the nitric acid or halogen compound at a molar ratio of 1:1.8-2, grind evenly, add 50-150 mL of deionized water to fully mix and dissolve, and obtain a mixture. The nitric acid or halogen compound is ammonium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, ammonium chloride, potassium chloride, rubidium chloride, cesium chloride, ammonium bromide, potassium bromide, rubidium bromide, or cesium bromide.

[0015] Alternatively, fluorine-containing compounds, methylboric acid, and nitric acid or halogen-containing compounds can be directly mixed in a molar ratio of 1.5-2.5:1:2.5-4 to obtain a mixture. Then, 50-100 ml of deionized water is added to fully dissolve the mixture to obtain a solution.

[0016] d. Preparation of A3[CH3BF3]X2 seed crystals: The mixed solution in step c is kept at a constant temperature for 2-5 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as the A3[CH3BF3]X2 seed crystals of this series of compounds.

[0017] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and place the seed crystal on the surface of the saturated mixed solution in step d. Heat the solution to 45-50℃, rotate the seed crystal rod at 1-60 rpm to grow the crystal, keep the temperature constant for 1-3 days, and then cool it to room temperature at a rate of 0.5℃ / h. Remove the crystal from the solution to obtain the A3[CH3BF3]X2 nonlinear optical crystal series.

[0018] The aforementioned series of methyltrifluoroborate nonlinear optical crystals are used in the preparation of harmonic light output from the 1064nm fundamental frequency light of Nd:YAG lasers, which is then used for 2nd, 3rd, or 4th harmonic output.

[0019] The series of methyltrifluoroborate nonlinear optical crystals are used in the preparation of frequency multiplier generators, up or down frequency converters, or optical parametric oscillators.

[0020] The present invention describes a method for preparing a series of methyltrifluoroborate nonlinear optical crystals. This method yields a series of A3[CH3BF3]X2 nonlinear optical crystals with centimeter-sized crystals. These crystals exhibit no obvious layered growth habit. By using large-sized containers and extending the crystal growth period, correspondingly large-sized A3[CH3BF3]X2 nonlinear optical crystals can be obtained. During the growth of this series of A3[CH3BF3]X2 nonlinear optical crystals, the crystals grow easily, are transparent and unencapsulated, and have advantages such as fast growth rate, low cost, and easy acquisition of large-sized crystals.

[0021] Using the method described in this invention, a large-size series of A3[CH3BF3]X2 nonlinear optical crystals are obtained. Based on the crystallographic data of the crystals, the crystal blanks are oriented, and the crystals are cut according to the required angle, thickness, and cross-sectional dimensions. The light-transmitting surface of the crystals is then polished, and the crystals can be used as nonlinear optical devices. This series of A3[CH3BF3]X2 nonlinear optical crystals has advantages such as a wide light transmission band, stable physicochemical properties, moderate mechanical hardness, resistance to breakage, and ease of cutting, polishing, and storage. Attached Figure Description

[0022] Figure 1 The powder XRD pattern of A3[CH3BF3]X2 (A = NH4, K, Rb, Cs, X = [NO3], Cl, Br) of the present invention;

[0023] Figure 2 This is a structural diagram of the A3[CH3BF3]X2 (A = NH4, K, Rb, Cs, X = [NO3], Cl, Br) crystal of the present invention;

[0024] Figure 3This is a schematic diagram illustrating the working principle of the nonlinear optical device fabricated from the A3[CH3BF3]X2 (A=NH4, K, Rb, Cs, X=[NO3], Cl, Br) crystal of the present invention. In the diagram, 1 is the laser, 2 is the emitted beam, 3 is the A3[CH3BF3]X2 (A=NH4, K, Rb, Cs, X=[NO3], Cl, Br) crystal, 4 is the emitted beam, and 5 is the filter. Detailed Implementation

[0025] Example 1

[0026] Based on the reaction formula: 2NH4NO3 + NH4CH3BF3 → (NH4)3[CH3BF3][NO3]2, the nonlinear optical crystal (NH4)3[CH3BF3][NO3]2 was synthesized using the top-seeded crystal method.

[0027] a. Mix NH4HF2 and CH3B(OH)2 at a molar ratio of 1.8:1 to obtain a mixture. Add 50 ml of deionized water to dissolve the mixture completely to obtain a solution. Ammonium hydrofluoride can be replaced by ammonium fluoride or ammonium tetrafluoroborate.

[0028] b. The mixed solution in step a is kept at a constant temperature for 4 days and allowed to stand until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, the crystals are taken out and placed on filter paper to dry, thus obtaining the compound NH4CH3BF3 containing methyltrifluoroboric acid.

[0029] c. Mix NH4CH3BF3 and NH4NO3 in a molar ratio of 1:2 and grind them evenly. Add 50mL of deionized water and mix thoroughly to dissolve, thus obtaining a mixed solution.

[0030] d. Preparation of seed crystals of compound (NH4)3[CH3BF3][NO3]2: The mixed solution in step c is kept at a constant temperature for 2 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as seed crystals of compound (NH4)3[CH3BF3][NO3]2.

[0031] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step d. Heat the solution to 45-50℃, rotate the seed crystal rod at 10 rpm to grow the crystal, keep the temperature constant for 2 days, and then cool it to room temperature at a rate of 0.5℃ / h. After that, take the crystal out of the solution to obtain a 21mm×15mm×6mm (NH4)3[CH3BF3][NO3]2 nonlinear optical crystal.

[0032] Example 2

[0033] Based on the reaction formula: 2KNO3 + KCH3BF3 → K3[CH3BF3][NO3]2, the K3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0034] a. Mix KHF2 and CH3B(OH)2 at a molar ratio of 1.9:1 to obtain a mixture. Add 50 ml of deionized water to dissolve the mixture completely to obtain a solution. Potassium hydrofluoride can be replaced by potassium fluoride or potassium tetrafluoroborate.

[0035] b. The mixed solution in step a is kept at a constant temperature for 2 days and allowed to stand until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, the crystals are taken out and placed on filter paper to dry, thus obtaining the compound KCH3BF3 containing methyltrifluoroboric acid.

[0036] c. Mix KCH3BF3 and KNO3 at a molar ratio of 1:1.8 and grind them evenly. Add 50 mL of deionized water and mix thoroughly to dissolve, thus obtaining a mixed solution.

[0037] d. Preparation of K3[CH3BF3][NO3]2 seed crystals: The mixed solution in step c is kept at a constant temperature for 3 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as K3[CH3BF3][NO3]2 seed crystals.

[0038] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step d. Heat the solution to 47°C, rotate the seed crystal rod at 12 rpm to grow the crystal, keep the temperature constant for 3 days, and then cool it to room temperature at a rate of 0.7°C / h. After that, take the crystal out of the solution to obtain a 22mm×21mm×10mm K3[CH3BF3][NO3]2 nonlinear optical crystal.

[0039] Example 3

[0040] Based on the reaction formula: 2RbNO3 + RbCH3BF3 → Rb3[CH3BF3][NO3]2, the Rb3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0041] a. Mix RbHF2 and CH3B(OH)2 at a molar ratio of 1.5:1 until homogeneous to obtain a mixture. Add 40 ml of deionized water to dissolve the mixture completely to obtain a solution. Rubidium hydrofluoride can be replaced by rubidium fluoride or rubidium tetrafluoroborate.

[0042] b. The mixed solution in step a is kept at a constant temperature for 2 days and allowed to stand until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, the crystals are taken out and placed on filter paper to dry, thus obtaining the compound RbCH3BF3 containing methyltrifluoroboric acid.

[0043] c. Mix RbCH3BF3 and RbNO3 in a molar ratio of 1:2 and grind them evenly. Add 50mL of deionized water and mix thoroughly to dissolve, thus obtaining a mixed solution.

[0044] d. Preparation of Rb3[CH3BF3][NO3]2 seed crystals: The mixed solution in step c is kept at a constant temperature for 5 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as Rb3[CH3BF3][NO3]2 seed crystals.

[0045] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step d. Heat the solution to 45°C, rotate the seed crystal rod at 14 rpm to grow the crystal, keep the temperature constant for 3 days, and then cool it to room temperature at a rate of 0.6°C / h. After that, take the crystal out of the solution to obtain a 14mm×13mm×10mm Rb3[CH3BF3][NO3]2 nonlinear optical crystal.

[0046] Example 4

[0047] Based on the reaction formula: 2CsNO3 + CsCH3BF3 → Cs3[CH3BF3][NO3]2, the Cs3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0048] a. Mix CsHF2 and CH3B(OH)2 at a molar ratio of 2:1 to obtain a mixture. Add 50 ml of deionized water to dissolve the mixture completely. Cesium hydrofluoride can be replaced by cesium fluoride or cesium tetrafluoroborate.

[0049] b. Let the mixed solution in step a stand at a constant temperature for 3 days until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, take out the crystals and place them on filter paper to dry. This will give you the compound CsCH3BF3 containing methyltrifluoroboric acid.

[0050] c. Mix CsCH3BF3 and CsNO3 at a molar ratio of 1:2 and grind them evenly. Add 50 mL of deionized water to fully mix and dissolve them to obtain a mixed solution.

[0051] d. Preparation of seed crystals of compound Cs3[CH3BF3][NO3]2: The mixed solution from step c was kept at a constant temperature for 5 days in a polytetrafluoroethylene beaker, then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as seed crystals of compound Cs3[CH3BF3][NO3]2.

[0052] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step d. Heat the mixed solution to 45°C, rotate the seed crystal rod at 17 rpm to grow the crystal, keep the temperature constant for 4 days, and then cool it to room temperature at a cooling rate of 0.6°C / h. After that, take the crystal out of the solution to obtain a 26 mm × 10 mm × 8 mm Cs3[CH3BF3][NO3]2 nonlinear optical crystal.

[0053] Example 5

[0054] Based on the reaction formula: 2NH4NO3 + NH4CH3BF3 → (NH4)3[CH3BF3][NO3]2, the nonlinear optical crystal (NH4)3[CH3BF3][NO3]2 was synthesized using the top-seeded crystal method.

[0055] NH4HF2, CH3B(OH)2 and NH4NO3 are directly mixed in a molar ratio of 1.8:1:2 to obtain a mixture. 50 ml of deionized water is added to dissolve the mixture completely to obtain a solution. Ammonium hydrofluoride can be replaced by ammonium fluoride or ammonium tetrafluoroborate.

[0056] Preparation of seed crystals of compound (NH4)3[CH3BF3][NO3]2: The obtained mixed solution was kept at a constant temperature for 2 days and placed in a polytetrafluoroethylene beaker. The beaker was then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as seed crystals of compound (NH4)3[CH3BF3][NO3]2.

[0057] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the obtained saturated mixed solution. The temperature of the mixed solution is heated to 46℃, and the seed crystal rod is rotated at 20 rpm to grow the crystal. The temperature is kept constant for 3 days, and then cooled to room temperature at a cooling rate of 0.8℃ / h. The crystal is then taken out of the solution, and a 10mm×15mm×17mm (NH4)3[CH3BF3][NO3]2 nonlinear optical crystal is obtained.

[0058] Example 6

[0059] Based on the reaction formula: 2KNO3 + KCH3BF3 → K3[CH3BF3][NO3]2, the K3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0060] KHF2, CH3B(OH)2 and KNO3 were directly mixed in a molar ratio of 1.5:1:3 to obtain a mixture. 70 ml of deionized water was added to dissolve the mixture completely to obtain a solution. Potassium hydrofluoride can be replaced by potassium fluoride or potassium tetrafluoroborate.

[0061] Preparation of K3[CH3BF3][NO3]2 seed crystals: The obtained mixed solution was kept at a constant temperature for 3 days and placed in a polytetrafluoroethylene beaker. The beaker was then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as K3[CH3BF3][NO3]2 seed crystals.

[0062] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 48℃, and the seed crystal rod is rotated at 23 rpm to grow the crystal. The temperature is kept constant for 4 days, and then cooled to room temperature at a rate of 0.5℃ / h. The crystal is then taken out of the solution, and a K3[CH3BF3][NO3]2 nonlinear optical crystal with a diameter of 32mm×12mm×8mm is obtained.

[0063] Example 7

[0064] Based on the reaction formula: 2RbNO3 + RbCH3BF3 → Rb3[CH3BF3][NO3]2, the Rb3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0065] RbHF2, CH3B(OH)2 and RbNO3 were directly mixed in a molar ratio of 1.6:1:2.8 to obtain a mixture. 80 ml of deionized water was added to dissolve the mixture completely to obtain a solution. Rubidium hydrofluoride can be replaced by rubidium fluoride or rubidium tetrafluoroborate.

[0066] Preparation of seed crystals of compound Rb3[CH3BF3][NO3]2: The obtained mixed solution was kept at a constant temperature for 3 days and placed in a polytetrafluoroethylene beaker. The beaker was then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as seed crystals of compound Rb3[CH3BF3][NO3]2.

[0067] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 50°C, and the seed crystal rod is rotated at 15 rpm to grow the crystal. The temperature is kept constant for 3 days, and then cooled to room temperature at a rate of 0.6°C / h. The crystal is then taken out of the solution, and a 10 mm × 9 mm × 4 mm Rb3[CH3BF3][NO3]2 nonlinear optical crystal is obtained.

[0068] Example 8

[0069] Based on the reaction formula: 2CsNO3 + CsCH3BF3 → Cs3[CH3BF3][NO3]2, the Cs3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0070] CsHF2, CH3B(OH)2 and CsNO3 were directly mixed in a molar ratio of 1.8:1:3 to obtain a homogeneous mixture. 100 ml of deionized water was added to dissolve the mixture completely to obtain a solution. Cesium hydrofluoride can be replaced by cesium fluoride or cesium tetrafluoroborate.

[0071] Preparation of seed crystals of compound Cs3[CH3BF3][NO3]2: The obtained mixed solution was kept at a constant temperature for 2 days and placed in a polytetrafluoroethylene beaker. The beaker was then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as seed crystals of compound Cs3[CH3BF3][NO3]2.

[0072] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 49°C, and the seed crystal rod is rotated at 17 rpm to grow the crystal. The temperature is kept constant for 2 days, and then cooled to room temperature at a rate of 0.9°C / h. The crystal is then taken out of the solution, and a 15mm×14mm×12mm Cs3[CH3BF3][NO3]2 nonlinear optical crystal is obtained.

[0073] Example 9

[0074] Based on the reaction formula: 2NH4NO3 + NH4CH3BF3 → (NH4)3[CH3BF3][NO3]2, the nonlinear optical crystal (NH4)3[CH3BF3][NO3]2 was synthesized using the top-seeded crystal method.

[0075] a. Mix NH4F and CH3B(OH)2 in a molar ratio of 3:1 until homogeneous to obtain a mixture. Add 50 ml of deionized water to dissolve the mixture completely to obtain a solution. Ammonium fluoride can be replaced by ammonium hydrofluoride or ammonium tetrafluoroborate.

[0076] b. Let the mixed solution in step a stand at a constant temperature for 4 days until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, take out the crystals and place them on filter paper to dry. This will give you the compound NH4CH3BF3 containing methyltrifluoroboric acid.

[0077] c. Mix NH4CH3BF3 and KNO3 in a molar ratio of 1:1.8 and grind them evenly. Add 30 mL of deionized water and mix thoroughly to obtain a mixed solution.

[0078] d. Preparation of seed crystals of compound (NH4)3[CH3BF3][NO3]2: The mixed solution in step c is kept at a constant temperature for 2 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as seed crystals of compound (NH4)3[CH3BF3][NO3]2.

[0079] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step c. Heat the mixed solution to 49°C, rotate the seed crystal rod at 26 rpm to grow the crystal, keep the temperature constant for 3 days, and then cool it to room temperature at a cooling rate of 1.3°C / h. After that, take the crystal out of the solution to obtain a 12mm×8mm×6mm (NH4)3[CH3BF3][NO3]2 nonlinear optical crystal.

[0080] Example 10

[0081] Based on the reaction formula: 2KNO3 + KCH3BF3 → K3[CH3BF3][NO3]2, the K3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0082] a. Mix KF and CH3B(OH)2 at a molar ratio of 3.5:1 to obtain a mixture. Add 90 ml of deionized water to dissolve the mixture completely to obtain a solution. Potassium fluoride can be replaced by potassium hydrofluoride or potassium tetrafluoroborate.

[0083] b. The mixed solution in step a is kept at a constant temperature for 3 days and allowed to stand until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, the crystals are taken out and placed on filter paper to dry, thus obtaining the compound KCH3BF3 containing methyltrifluoroboric acid.

[0084] c. Mix KCH3BF3 and KNO3 in a molar ratio of 1:1.8 and grind them evenly. Add 40 mL of deionized water to fully mix and dissolve them to obtain a mixed solution.

[0085] d. Preparation of K3[CH3BF3][NO3]2 seed crystals: The mixed solution in step c is kept at a constant temperature for 2 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as K3[CH3BF3][NO3]2 seed crystals.

[0086] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step c. Heat the mixed solution to 49°C, rotate the seed crystal rod at 16 rpm to grow the crystal, keep the temperature constant for 5 days, and then cool it to room temperature at a cooling rate of 1.2°C / h. After that, take the crystal out of the solution to obtain a 10 mm × 9 mm × 9 mm K3[CH3BF3][NO3]2 nonlinear optical crystal.

[0087] Example 11

[0088] Based on the reaction formula: 2RbNO3 + KCH3BF3 → Rb3[CH3BF3][NO3]2, the Rb3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0089] a. Mix RbF and CH3B(OH)2 at a molar ratio of 2.7:1 to obtain a mixture. Add 60 ml of deionized water to dissolve the mixture completely. Rubidium fluoride can be replaced by rubidium hydrofluoride or rubidium tetrafluoroborate.

[0090] b. The mixed solution in step a is kept at a constant temperature for 2 days and allowed to stand until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, the crystals are taken out and placed on filter paper to dry, thus obtaining the compound RbCH3BF3 containing methyltrifluoroboric acid.

[0091] c. Mix RbCH3BF3 and KNO3 at a molar ratio of 1:1.8 and grind them evenly. Add 40 mL of deionized water to fully mix and dissolve them to obtain a mixed solution.

[0092] d. Preparation of Rb3[CH3BF3][NO3]2 seed crystals: The mixed solution in step c is kept at a constant temperature for 3 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as Rb3[CH3BF3][NO3]2 seed crystals.

[0093] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step c. Heat the mixed solution to 48°C, rotate the seed crystal rod at 14 rpm to grow the crystal, keep the temperature constant for 3 days, and then cool it to room temperature at a cooling rate of 0.9°C / h. After that, take the crystal out of the solution to obtain an 11 mm × 14 mm × 16 mm Rb3[CH3BF3][NO3]2 nonlinear optical crystal.

[0094] Example 12

[0095] Based on the reaction formula: 2CsNO3 + CsCH3BF3 → Cs3[CH3BF3][NO3]2, the Cs3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0096] a. Mix CsF and CH3B(OH)2 at a molar ratio of 3.3:1 until homogeneous to obtain a mixture. Add 60 ml of deionized water to fully dissolve the mixture to obtain a solution. Cesium fluoride can be replaced by cesium hydrofluoride or cesium tetrafluoroborate.

[0097] b. The mixed solution in step a is kept at a constant temperature for 2 days and allowed to stand until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, the crystals are taken out and placed on filter paper to dry, thus obtaining the compound CsCH3BF3 containing methyltrifluoroboric acid.

[0098] c. Mix CsCH3BF3 and KNO3 at a molar ratio of 1:1.8 and grind them evenly. Add 40 mL of deionized water to fully mix and dissolve them to obtain a mixed solution.

[0099] d. Preparation of Cs3[CH3BF3][NO3]2 seed crystals: The mixed solution from step c was kept at a constant temperature for 2 days in a polytetrafluoroethylene beaker, then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as Cs3[CH3BF3][NO3]2 seed crystals.

[0100] e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and lower the seed crystal to the surface of the saturated mixed solution prepared in step c. Heat the mixed solution to 50°C, rotate the seed crystal rod at 8 rpm to grow the crystal, keep the temperature constant for 5 days, and then cool it to room temperature at a cooling rate of 0.8°C / h. After that, take the crystal out of the solution to obtain a 12mm×17mm×16mm Cs3[CH3BF3][NO3]2 nonlinear optical crystal.

[0101] Example 13

[0102] Based on the reaction formula: 2NH4Cl + NH4CH3BF3 → (NH4)3[CH3BF3]Cl2, the nonlinear optical crystal (NH4)3[CH3BF3]Cl2 was synthesized using the top-seeded crystal method.

[0103] NH4F, CH3B(OH)2 and NH4Cl are directly mixed in a molar ratio of 1.8:1:3 to obtain a mixture. 60 ml of deionized water is added to dissolve the mixture completely to obtain a solution. Ammonium fluoride can be replaced by ammonium hydrofluoride or ammonium tetrafluoroborate.

[0104] Preparation of (NH4)3[CH3BF3]Cl2 seed crystals: The obtained mixed solution was kept at a constant temperature for 5 days and placed in a polytetrafluoroethylene beaker. The beaker was then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as (NH4)3[CH3BF3]Cl2 seed crystals.

[0105] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 45℃, and the seed crystal rod is rotated at 22 rpm to grow the crystal. The temperature is kept constant for 4 days, and then cooled to room temperature at a cooling rate of 0.6℃ / h. The crystal is then taken out of the solution, and a (NH4)3[CH3BF3]Cl2 nonlinear optical crystal of 32mm×18mm×10mm is obtained.

[0106] Example 14

[0107] Based on the reaction formula: 2KCl + KCH3BF3 → K3[CH3BF3]Cl2, the K3[CH3BF3][NO3]2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0108] KF, CH3B(OH)2 and KCl were directly mixed in a molar ratio of 1.5:1:3 to obtain a mixture. 40 ml of deionized water was added to dissolve the mixture completely to obtain a solution. Potassium fluoride can be replaced by potassium hydrofluoric acid or potassium tetrafluoroborate.

[0109] Preparation of K3[CH3BF3]Cl2 seed crystals: The obtained mixed solution was kept at a constant temperature for 3 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as K3[CH3BF3]Cl2 seed crystals.

[0110] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 48℃, and the seed crystal rod is rotated at 16 rpm to grow the crystal. The temperature is kept constant for 4 days, and then cooled to room temperature at a rate of 0.8℃ / h. The crystal is then taken out of the solution, and a K3[CH3BF3]Cl2 nonlinear optical crystal with a diameter of 15mm×10mm×8mm is obtained.

[0111] Example 15

[0112] Based on the reaction formula: 2RbCl + RbCH3BF3 → Rb3[CH3BF3]Cl2, the Rb3[CH3BF3]Cl2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0113] RbF, CH3B(OH)2, and RbCl were directly mixed in a molar ratio of 2:1:4 to obtain a homogeneous mixture. 100 ml of deionized water was then added to dissolve the mixture completely to obtain a solution. Rubidium fluoride can be replaced by rubidium hydrofluoride or rubidium tetrafluoroborate.

[0114] Preparation of Rb3[CH3BF3]Cl2 seed crystals: The obtained mixed solution was kept at a constant temperature for 5 days and placed in a polytetrafluoroethylene beaker. The beaker was then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as Rb3[CH3BF3]Cl2 seed crystals.

[0115] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 48℃, and the seed crystal rod is rotated at 14 rpm to grow the crystal. The temperature is kept constant for 2 days, and then cooled to room temperature at a rate of 1.1℃ / h. The crystal is then taken out of the solution, and a 10mm×9mm×8mm Rb3[CH3BF3]Cl2 nonlinear optical crystal is obtained.

[0116] Example 16

[0117] Based on the reaction formula: 2CsCl + CsCH3BF3 → Cs3[CH3BF3]Cl2, the Cs3[CH3BF3]Cl2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0118] CsF, CH3B(OH)2, and CsCl were directly mixed in a molar ratio of 1.6:1:3.2 to obtain a homogeneous mixture. 80 ml of deionized water was then added to dissolve the mixture completely to obtain a solution. Cesium fluoride can be replaced by cesium hydrofluoride or cesium tetrafluoroborate.

[0119] Preparation of Cs3[CH3BF3]Cl2 seed crystals: The obtained mixed solution was kept at a constant temperature for 2 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as Cs3[CH3BF3]Cl2 seed crystals.

[0120] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 49°C, and the seed crystal rod is rotated at 9 rpm to grow the crystal. The temperature is kept constant for 5 days, and then cooled to room temperature at a rate of 1.6°C / h. The crystal is then taken out of the solution, and a 12mm×10mm×8mm Cs3[CH3BF3]Cl2 nonlinear optical crystal is obtained.

[0121] Example 17

[0122] Based on the reaction formula: 2NH4Br + NH4CH3BF3 → (NH4)3[CH3BF3]Br2, the nonlinear optical crystal (NH4)3[CH3BF3]Br2 was synthesized using the top-seeded crystal method.

[0123] NH4F, CH3B(OH)2 and NH4Br are directly mixed in a molar ratio of 1.9:1:2.5 to obtain a mixture. 50 ml of deionized water is added to dissolve the mixture completely to obtain a solution. Ammonium fluoride can be replaced by ammonium hydrofluoride or ammonium tetrafluoroborate.

[0124] Preparation of (NH4)3[CH3BF3]Br2 seed crystals: The obtained mixed solution was kept at a constant temperature for 3 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as (NH4)3[CH3BF3]Br2 seed crystals.

[0125] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 47°C, and the seed crystal rod is rotated at 10 rpm to grow the crystal. The temperature is kept constant for 4 days, and then cooled to room temperature at a rate of 0.8°C / h. The crystal is then taken out of the solution, and a (NH4)3[CH3BF3]Br2 nonlinear optical crystal with a diameter of 11 mm × 10 mm × 7 mm is obtained.

[0126] Example 18

[0127] Based on the reaction formula: 2KNO3 + KCH3BF3 → K3[CH3BF3]Br2, the K3[CH3BF3]Br2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0128] KF, CH3B(OH)2 and KBr were mixed evenly in a molar ratio of 2:1:3 to obtain a mixture. 90 ml of deionized water was added to dissolve the mixture completely to obtain a solution. Potassium fluoride can be replaced by potassium hydrofluoride or potassium tetrafluoroborate.

[0129] Preparation of K3[CH3BF3]Br2 seed crystals: The obtained mixed solution was kept at a constant temperature for 3 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as K3[CH3BF3]Br2 seed crystals.

[0130] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 49°C, and the seed crystal rod is rotated at 10 rpm to grow the crystal. The temperature is kept constant for 5 days, and then cooled to room temperature at a rate of 0.8°C / h. The crystal is then taken out of the solution, and a K3[CH3BF3]Br2 nonlinear optical crystal with a diameter of 14 mm × 9 mm × 8 mm is obtained.

[0131] Example 19

[0132] Based on the reaction formula: 2RbNO3 + RbCH3BF3 → K3[CH3BF3]Br2, the Rb3[CH3BF3]Br2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0133] RbF, CH3B(OH)2, and RbBr were directly mixed in a molar ratio of 1.5:1:3 to obtain a homogeneous mixture. 70 ml of deionized water was added to dissolve the mixture completely to obtain a solution. Rubidium fluoride can be replaced by rubidium hydrofluoride or rubidium tetrafluoroborate.

[0134] Preparation of Rb3[CH3BF3]Br2 seed crystals: The obtained mixed solution was kept at a constant temperature for 5 days and placed in a polytetrafluoroethylene beaker. The beaker was then sealed with a polyvinyl chloride film and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as Rb3[CH3BF3][NO3]2 seed crystals.

[0135] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 50°C, and the seed crystal rod is rotated at 13 rpm to grow the crystal. The temperature is kept constant for 2 days, and then cooled to room temperature at a rate of 0.5°C / h. The crystal is then taken out of the solution, and a 16mm×12mm×8mm Rb3[CH3BF3]Br2 nonlinear optical crystal is obtained.

[0136] Example 20

[0137] Based on the reaction formula: 2CsNO3 + CsCH3BF3 → Cs3[CH3BF3]Br2, the Cs3[CH3BF3]Br2 nonlinear optical crystal was synthesized using the top-seeded crystal method.

[0138] CsF, CH3B(OH)2, and CsBr were directly mixed in a molar ratio of 2.5:1:2.5 to obtain a homogeneous mixture. 80 ml of deionized water was then added to dissolve the mixture completely to obtain a solution. Cesium fluoride can be replaced by cesium hydrofluoride or cesium tetrafluoroborate.

[0139] Preparation of Cs3[CH3BF3]Br2 seed crystals: The obtained mixed solution was kept at a constant temperature for 3 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes were punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution was saturated, crystals began to precipitate. The better quality crystals were taken out as Cs3[CH3BF3]Br2 seed crystals.

[0140] The obtained seed crystal is fixed on the seed crystal rod, and the seed crystal is lowered from the top of the aqueous crystal growth furnace to the surface of the prepared saturated mixed solution. The temperature of the mixed solution is heated to 45℃, and the seed crystal rod is rotated at 10 rpm to grow the crystal. The temperature is kept constant for 5 days, and then cooled to room temperature at a cooling rate of 0.8℃ / h. The crystal is then taken out of the solution, and a 19mm×14mm×10mm Cs3[CH3BF3]Br2 nonlinear optical crystal is obtained.

[0141] Example 21

[0142] The arbitrary A3[CH3BF3]X2 nonlinear optical crystals obtained in Examples 1-20 are processed according to a matching direction, and then... Figure 3 As shown, the laser is positioned at position 3. At room temperature, a Q-switched Nd:YAG laser is used as the light source with an incident wavelength of 1064nm. An infrared beam 2 with a wavelength of 1064nm is emitted from the Q-switched Nd:YAG laser 1 and enters the A3[CH3BF3]X2 single crystal 3, producing green frequency-doubled light with a wavelength of 532nm. The output intensity is approximately 0.9-1.2 times that of KDP under the same conditions.

Claims

1. A series of methyltrifluoroborate nonlinear optical crystals, characterized in that... The general molecular formula of this crystal is A3[CH3BF3]X2, where A = NH4, K, Rb, Cs, and X = [NO3], Cl, Br. It does not have a center of symmetry, belongs to the orthorhombic crystal system, and has a space group of [missing information]. Cmc 21 (No. 36), cell parameters: 1) (NH4)3[CH3BF3][NO3]2: a = 11.8272(14) Å, b = 8.1556(12) Å, c = 10.9621(9) Å, α=90, β=90, γ=90, Z = 4, V= 925.609(2) Å 3 ; 2) K3[CH3BF3][NO3]2: a= 11.9141(17) Å, b = 8.1556(12) Å, c = 10.9621(14) Å, α=90, β=90, γ=90, Z = 4, V=1065.2(3)Å 3 ; 3) Rb3[CH3BF3][NO3]2: a = 12.0141(10) Å, b = 8.3542(10) Å, c = 11.3254(2) Å, α=90, β=90, γ=90, Z = 4, V= 1135.27 (4)Å 3 ; 4) Cs3[CH3BF3][NO3]2: a = 12.210(4)Å, b = 8.417(4) Å, c = 11.5247(8) Å, α=90, β=90, γ=90, Z = 4, V= 1178.52(15) Å 3 ; 5) (NH4)3[CH3BF3]Cl2: a = 12.0246(14) Å, b = 8.2314(12) Å, c = 11.3654 (9) Å, α=90, β=90, γ=90, Z = 4, V= 1124.4(2)Å 3 ; 6) K3[CH3BF3]Cl2: a = 12.2214(14) Å, b = 8.2503(12) Å, c = 11.3324 (9) Å, α=90, β=90, γ=90, Z = 4, V= 1142.2(2)Å 3 ; 7) Rb3[CH3BF3]Cl2: a = 12.4265(15) Å, b = 8.3310(12) Å, c = 11.4513 (9) Å, α=90, β=90, γ=90, Z =4, V= 1185.3(6)Å 3 ; 8)Cs3[CH3BF3]Cl2:a = 12.3327(15) Å,b = 8.3945(17) Å,c =11.5041(7) Å,α=90,β=90,γ=90,Z = 4,V= 1191.1(3)Å 3 ; 9) (NH4)3[CH3BF3]Br2:a =12.0246(14) Å,b = 8.2314(12) Å,c = 11.3654 (9) Å,α=90,β=90,γ=90,Z = 4,V=1124.4(2)Å 3 ; 10) K3[CH3BF3]Br2: a = 12.2463(6) Å, b = 8.4654(17) Å, c = 11.5205(9) Å, α=90, β=90, γ=90, Z = 4, V= 1195.3(7) Å 3 ;11) Rb3[CH3BF3]Br2: a = 12.2463(6) Å, b = 8.4654(17) Å, c = 11.5205 (9) Å, α=90, β=90, γ=90, Z = 4, V= 1195.3(7) Å 3 ; 12)Cs3[CH3BF3]Br2: a = 12.6254(2) Å, b = 8.2716(4) Å, c = 11.5625(15) Å, α=90, β=90, γ=90, Z = 4, V= 1207.44(7) Å 3 。 2. The method for preparing a series of methyltrifluoroborate nonlinear optical crystals according to claim 1, characterized in that... The top-seeded method is used for preparation, and the specific operation is carried out according to the following steps: a. Mix the fluorinated compound and methylboric acid at a molar ratio of 1.5-3.5:1 until homogeneous, add 0-50 mL of deionized water to fully mix and dissolve, and obtain a mixed solution. The fluorinated compound is ammonium hydrofluoride, potassium hydrofluoride, rubidium hydrofluoride, cesium hydrofluoride, ammonium tetrafluoroborate, potassium tetrafluoroborate, rubidium tetrafluoroborate, or cesium tetrafluoroborate. b. Keep the mixed solution from step a at a constant temperature for 2-5 days until the solvent evaporates to supersaturation and crystals begin to precipitate. Before the solvent has completely evaporated, take out the crystals and place them on filter paper to dry, thus obtaining a series of compounds containing methyltrifluoroborate, namely ammonium methyltrifluoroborate, potassium methyltrifluoroborate, rubidium methyltrifluoroborate or cesium methyltrifluoroborate. c. Mix the methyltrifluoroboronic acid compound obtained in step b with the nitric acid or halogen compound at a molar ratio of 1:1.8-2, grind evenly, add 50-150 mL of deionized water to fully mix and dissolve, and obtain a mixed solution. The nitric acid or halogen compound is ammonium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, ammonium chloride, potassium chloride, rubidium chloride, cesium chloride, ammonium bromide, potassium bromide, rubidium bromide, or cesium bromide. Alternatively, fluorine-containing compounds, methylboric acid, and nitric acid or halogen-containing compounds can be directly mixed in a molar ratio of 1.5-2.5:1:2.5-4 to obtain a mixture. Then, 50-100 ml of deionized water is added to fully dissolve the mixture to obtain a solution. d. Preparation of A3[CH3BF3]X2 seed crystals: The mixed solution in step c is kept at a constant temperature for 2-5 days, placed in a polytetrafluoroethylene beaker, sealed with a polyvinyl chloride film, and placed in a static environment without shaking, pollution, or air convection. Several small holes are punched in the seal to adjust the evaporation rate of the solvent in the solution. After the solution is saturated, crystals begin to precipitate. The better quality crystals are taken out as the A3[CH3BF3]X2 seed crystals of this series of compounds. e. Fix the seed crystal obtained in step d onto the seed crystal rod, lower the seed crystal from the top of the aqueous crystal growth furnace, and place the seed crystal on the surface of the saturated mixed solution in step d. Heat the solution to 45-50℃, rotate the seed crystal rod at 1-60 rpm to grow the crystal, keep the temperature constant for 1-3 days, and then cool it to room temperature at a rate of 0.5℃ / h. Remove the crystal from the solution to obtain the A3[CH3BF3]X2 nonlinear optical crystal series.

3. The use of the series of methyltrifluoroborate nonlinear optical crystals according to claim 1 in preparing second-harmonic light output from the 1064 nm fundamental frequency light output by an Nd:YAG laser.

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