A series of fluorine-containing rare earth borate compounds and fluorine-containing rare earth borate nonlinear optical crystals, and a preparation method and use thereof

Abstract

The present invention relates to a series of fluorine-containing rare earth borate compounds, a series of fluorine-containing rare earth borate nonlinear optical crystals, and their preparation methods and uses. The general crystal chemical formula of the series of compounds and their crystals is all A2REB3O6F2, where A = Rb, Cs, NH4, RE = Sc, Y, La, the molecular weight is 247.46 - 571.14, the series of crystals belong to the orthorhombic system, the space group is Amm2, the cell parameters are a = 2.7182(4)-4.9617(8) Å, b = 7.7013(5)-9.9742(6) Å, c = 10.2634(1)-12.904(3) Å, Z = 2, the series of fluorine-containing rare earth borate compounds are synthesized by a solid-state reaction method or a hydrothermal method, and the series of nonlinear optical crystals grow by a high-temperature melt method, a hydrothermal method or a solution method. The series of materials can be used in the manufacture of second harmonic generators, up and down frequency converters, optical parametric oscillators, etc.

Description

Technical Field

[0001] The present invention relates to a series of fluorine-containing rare earth borate compounds and a method for preparing fluorine-containing rare earth borate nonlinear optical crystals, and a nonlinear optical device fabricated using the series of crystals.

Background Art

[0002] Deep ultraviolet coherent light with a wavelength of 200 - 150 nm has become increasingly important due to its potential applications in semiconductor lithography, laser micromachining, and modern scientific instruments. In the case of solid-state lasers, obtaining deep ultraviolet coherent light is achieved by the cascaded frequency conversion technology of nonlinear optical crystals. However, for applicable deep ultraviolet nonlinear optical crystals, I) a non-centrosymmetric structure, ii) a large second-order nonlinear optical coefficient (d ij ) should be at least equivalent to the d 36 of KDP, iii) high transparency in the deep ultraviolet region and as short an ultraviolet cut-off wavelength as possible, iv) moderate birefringence (Δn = 0.05 - 0.10) to satisfy the phase matching conditions for second harmonic generation in the ultraviolet or deep ultraviolet region, v) easy growth, non-toxic, and it is necessary to meet strict structural and performance requirements including chemical stability and good mechanical properties. However, due to the conflict of some of the above attributes, large bandgap materials often exhibit small doubling responses and birefringence, and the design and synthesis of deep ultraviolet nonlinear optical crystals still pose a great challenge.

[0003] Fluorine-containing borates with asymmetric [Y-O-F] polyhedra and π-conjugated [B3O6] primitives as basic structural units usually have a large band gap and are widely considered as candidate materials for exploring UV or DUV optical crystals. It should be noted that BBO has a strong second harmonic response (6×KDP), and the ultraviolet cut-off edge can reach 189 nm. However, there is a problem of phase transition at 925 °C, and since the ultraviolet cut-off edge is relatively long, this crystal cannot be used as a deep ultraviolet nonlinear optical crystal. However, [Y-O-F] polyhedra with large optical anisotropy are not only advantageous for enhancing the birefringence of the material, but also can connect other groups in the structure to form a 3D framework, and further shorten the ultraviolet cut-off edge. Therefore, the design and synthesis of fluorine-containing rare earth borate compounds with asymmetric [Y-O-F] polyhedra and π-conjugated [B3O6] primitives are effective means for designing deep ultraviolet nonlinear optical materials.

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the objectives of the present invention is to provide a series of fluorine-containing rare earth borate compounds and preparation methods.

[0005] The second objective of the present invention is to provide a series of fluorine-containing rare earth borate nonlinear optical crystals and preparation methods.

[0006] The third objective of the present invention is to provide the applications of a series of fluorine-containing rare earth borate nonlinear optical crystals.

Means for Solving the Problems

[0007] One of the objectives of the present invention is thus realized.

[0008] The object of the present invention is to provide a series of fluorine-containing rare earth borate compounds, the chemical formula of the series of fluorine-containing rare earth borate compounds being A2REB3O6F2, where A = Rb, Cs, NH4, RE = Sc, Y, La, and the molecular formulas are Rb2ScB3O6F2, Cs2ScB3O6F2, (NH4)2ScB3O6F2, Rb2YB3O6F2, Cs2YB3O6F2, (NH4)2YB3O6F2, Rb2LaB3O6F2, Cs2LaB3O6F2 or (NH4)2LaB3O6F2 respectively, and the molecular weight being 247.46 to 571.14. Using the solid-phase reaction method or the hydrothermal method or the solution method, a series of fluorine-containing rare earth borate compounds are prepared by the following chemical reaction formulas.

[0009] 1) 4AF (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 6H3BO3 → 2A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 9H2O↑

[0010] 2) 2AF (A = Rb, Cs, NH4) + 3A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 2REF3 (RE = Sc, Y, La) + 12H3BO3 → 4A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 3CO2↑ + 18H2O↑

[0011] 3) 2A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 6H3BO3 + 4NH4F → 2A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 2CO2↑ + 4NH3↑ + 11H2O↑

[0012] 4) 4A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 2REF3 (RE = Sc, Y, La) + 12H3BO3 + 2NH4F → 4A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 4CO2↑ + 2NH3↑ + 19H2O↑

[0013] 5) 4AOH (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 6H3BO3 + 4NH4F → 2A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 4NH3↑ + 13H2O↑

[0014] 6) 8AOH (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 2REF3 (RE = Sc, Y, La) + 12H3BO3 + 2NH4F → 4A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 2NH3↑ + 23H2O↑

[0015] 7) 6A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 4REF3 (RE = Sc, Y, La) + 18H3BO3 → 6A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 6CO2↑ + 27H2O↑

[0016] 8) 12AOH (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 4REF3 (RE = Sc, Y, La) + 18H3BO3 → 6A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 33H2O↑

[0017] 9) 4AF (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 3B2O3 → 2A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La)

[0018] 10) 2AF (A = Rb, Cs, NH4) + 3A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 2REF3 (RE = Sc, Y, La) + 6B2O3 → 4A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 3CO2↑

[0019] 11) 2A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 3B2O3 + 4NH4F → 2A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 2CO2↑ + 4NH3↑ + 2H2O↑

[0020] 12) 4A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 2REF3 (RE = Sc, Y, La) + 6B2O3 + 2NH4F → 4A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 4CO2↑ + 2NH3↑ + H2O↑

[0021] 13) 4AOH (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 3B2O3 + 4NH4F → 2A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 4NH3↑ + 4H2O↑

[0022] 14) 8AOH (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 2REF3 (RE = Sc, Y, La) + 6B2O3 + 2NH4F → 4A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 2NH3↑ + 5H2O↑

[0023] 15) 6A2CO3 (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 4REF3 (RE = Sc, Y, La) + 9B2O3 → 6A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 6CO2↑

[0024] 16) 12AOH (A = Rb, Cs, NH4) + RE2O3 (RE = Sc, Y, La) + 4REF3 (RE = Sc, Y, La) + 9B2O3 → 6A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 6H2O↑

[0025] 17) 2AF (A = Rb, Cs, NH4) + REN3O9·6H2O (RE = Sc, Y, La) + 3H3BO3 → A2REB3O6F 22 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 6H2O↑ + 3NH3↑ + 6O2↑

[0026] 18) 2AOH (A = Rb, Cs, NH4) + REN3O9·6H2O (RE = Sc, Y, La) + 3H3BO3 + 2AF → A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 8H2O↑ + 5NH3↑ + 6O2↑

[0027] 19) A2CO3 (A = Rb, Cs, NH4) + REN3O9·6H2O (RE = Sc, Y, La) + 3H3BO3 + 2AF → A2REB3O6F2 (A = Rb, Cs, NH4; RE = Sc, Y, La) + 7H2O↑ + 5NH3↑ + 6O2↑ + CO2↑

[0028] The second object of the present invention is thus realized.

[0029] An object of the present invention is to provide a series of fluorine-containing rare earth borate nonlinear optical crystals, and the series of fluorine-containing rare earth borate nonlinear optical crystals have the chemical formula A2REB3O6F2, where A = Rb, Cs, NH4, RE = Sc, Y, La, have no center of symmetry, belong to the orthorhombic system, have the space group Amm2, and the cell parameters are a = 2.7182(4)-4.9617(8) Å, b = 7.7013(5)-9.9742(6) Å, c = 10.2634(1)-12.904(3) Å, Z = 2. A series of fluorine-containing rare earth borate nonlinear optical crystals are grown by the high-temperature melt method, the hydrothermal method or the solution method.

[0030] Growing a series of fluorine-containing rare earth borate nonlinear optical crystals by the high-temperature melt method, and the specific operation is carried out in the following steps.

[0031] a. A series of single-phase polycrystalline powders of fluorine-containing rare earth borate compounds and a flux are uniformly mixed, heated to a temperature of 400 - 1000 °C, held at a constant temperature for a certain period of time to obtain a mixed melt, and then cooled to a temperature of 300 - 900 °C. Here, the molar ratio of the series of single-phase polycrystalline powders of fluorine-containing rare earth borate compounds to the flux is 1:0 - 50. Or directly mix a mixture of A = Rb, Cs, NH4-containing compounds, RE = Sc, Y, La-containing compounds, boron-containing compounds, and fluorine-containing compounds, or a mixture of A-containing compounds, RE-containing compounds, boron-containing compounds, fluorine-containing compounds, and a flux. Then, heat it to a temperature of 400 - 1000 °C, hold at a constant temperature for a certain period of time to obtain a mixed melt, and cool it to a saturation temperature of 300 - 900 °C. Here, the molar ratio of element A in the A-containing compound, element RE in the RE-containing compound, element boron in the boron-containing compound, element fluorine in the fluorine-containing compound, and the flux is 1.5 - 2.2:0.8 - 1.5:2.5 - 3.5:1.5 - 2.2:0 - 50.

[0032] The A = Rb, Cs, NH4-containing compounds include at least one of AOH, A2O, and alkali metal salts. The alkali metal salts include at least one of AF, ACl, ABr, ANO3, A2C2O2, A2CO3, AHCO3, A2SO4, where A = Rb, Cs, NH4.

[0033] The RE = Sc, Y, La-containing compounds are RE2O3, REF3, RE(NO3)3·6H2O.

[0034] The boron-containing compounds include at least one of B2O3, H3BO3, and borates. The borates include at least one of ABO2, ABO3, A3BO3, A2B4O7, where A = Rb, Cs, NH4.

[0035] The fluorine-containing compounds include AF, REF3, where A = Rb, Cs, NH4 and RE = Sc, Y, La. And other fluorine-containing compounds include at least one of KBF4, NaBF4, KPF6, NH4PF6.

[0036] The flux mainly contains alkali metal salts, namely alkali metal carbonates, alkali metal nitrates, alkali metal sulfates, alkali metal oxalates, alkali metal borates, alkali metal phosphates, alkali metal halides, alkali metal fluoroborates, alkali metal metaborates, and alkali metal oxides, alkali metal hydroxides, as well as at least one or more of yttrium fluoride, yttrium nitrate, yttrium oxide, lanthanum fluoride, lanthanum nitrate, lanthanum oxide, scandium fluoride, scandium nitrate, scandium oxide, boron oxide, boric acid, phosphoric acid, lead oxide, lead fluoride, molybdenum oxide, and bismuth oxide.

[0037] The series of fluorine-containing rare earth borate compound single-phase polycrystalline powders are prepared by a solid-phase synthesis method and include the following steps: Mix an A = Rb, Cs, NH4-containing compound, a RE = Sc, Y, La-containing compound, a boron-containing compound, and a fluorine-containing compound, and obtain the series of fluorine-containing rare earth borate compounds by a solid-phase reaction method. The molar ratio of element A in the A-containing compound, element RE in the RE-containing compound, element boron in the boron-containing compound, and element fluorine in the fluorine-containing compound is 1.5 - 2.2:0.8 - 1.5:2.5 - 3.5:1.5 - 2.2. Uniformly mix the raw materials of the A-containing compound, RE-containing compound, boron-containing compound, and fluorine-containing compound, put them into a muffle furnace after grinding, calcine to remove moisture and gas in the raw materials, cool to room temperature, take out and grind, then put them into a muffle furnace for firing, raise the temperature to 350 - 1000 °C, keep the temperature constant for a certain time, cool to room temperature, and take out the series of fluorine-containing rare earth borate compound single-phase polycrystalline powders obtained by grinding.

[0038] b. Preparation of a series of fluorine-containing rare earth borate nonlinear optical crystal seed crystals: Gradually lower the mixed melt obtained in step a to room temperature and crystallize spontaneously to obtain the seed crystals.

[0039] c. Place the crucible containing the mixed melt obtained in step a into the crystal growth furnace. Fix the seed crystal obtained in step b to the seed rod, lower the seed crystal from the top of the crystal growth furnace, first preheat the seed rod, lower the seed crystal until it contacts the liquid surface of the mixed melt or lower it into the mixed melt for melt-back, keep it at a constant temperature for a certain period of time, and then gradually lower the temperature to the saturation temperature.

[0040] d. Continuously lower the temperature slowly, rotate the seed rod to grow the crystal. After the single crystal grows to the desired scale, pull the crystal out from the surface of the mixed melt, slowly lower the temperature to room temperature, and then take the crystal out of the furnace chamber to obtain a series of fluorine-containing rare earth borate nonlinear optical crystals.

[0041] Grow a series of fluorine-containing rare earth borate nonlinear optical crystals A2REB3O6F2 by the hydrothermal method, where A = Rb, Cs, NH4 and RE = Sc, Y, La. The specific operation is carried out in the following steps.

[0042] a. After putting the A = Rb, Cs, NH4-containing compound, RE = Sc, Y, La-containing compound, boron-containing compound, and fluorine-containing compound into the polytetrafluoroethylene lining of the autoclave, add 0.1 - 50 mL of deionized water or 0.1 - 50 g of mineralizer, mix well to make it uniform to obtain a mixed solution. Here, the molar ratio of element A in the A-containing compound, element RE in the RE-containing compound, element boron in the boron-containing compound, element fluorine in the fluorine-containing compound to the mineralizer is 1.5 - 2.2:0.8 - 1.5:2.5 - 3.5:1.5 - 2.2:0 - 30. The mineralizer contains at least one or more of AOH, A2O, AF, ACl, ABr, ABF4, A3PO4, A3BO3, ANO3, A2C2O4, A2CO3, AHCO3, A2SO4, A2HPO4, AH2PO4, Y2O3, YF3, Y(NO3)3·6H2O, La2O3, LaF3, La(NO3)3·6H2O, Sc2O3, ScF3, Sc(NO3)3·6H2O, B2O3, KBF4, NaBF4, KPF6, NH4PF6, where A = Rb, Cs, NH4.

[0043] b. Tightly close the polytetrafluoroethylene-lined lid containing the mixed solution in Project a, place it in the corresponding high-pressure reactor, and tightly close the piston of the reactor.

[0044] c. Place the high-pressure reactor in step b into an incubator, heat it to 120 - 330 °C, keep it at a constant temperature for a certain period of time, and then cool it to room temperature.

[0045] d. Open the high-pressure reactor and filter the solution containing crystals to obtain a series of transparent fluorine-containing rare-earth borate nonlinear optical crystals.

[0046] Grow a series of fluorine-containing rare-earth borate nonlinear optical crystals A2REB3O6F2 by the solution method, where A = Rb, Cs, NH4 and RE = Sc, Y, La. The specific operations are carried out in the following steps.

[0047] After putting a compound containing A = Rb, Cs, NH4, a compound containing RE = Sc, Y, La, a boron-containing compound, and a fluorine-containing compound into a beaker, 0.1 - 400 mL of deionized water is added, and the solution is stirred until clear. Here, the molar ratio of element A in the A-containing compound, element RE in the RE-containing compound, element boron in the boron-containing compound, element fluorine in the fluorine-containing compound to the cosolvent is 1.5 - 2.2:0.8 - 1.5:2.5 - 3.5:1.5 - 2.2:0 - 20, and the cosolvent contains at least one or more of AOH, A2O, AF, ACl, ABr, ABF4, A3PO4, A3BO3, ANO3, A2C2O4, A2CO3, AHCO3, A2SO4, Y(NO3)3·6H2O, La(NO3)3·6H2O, Sc(NO3)3·6H2O, B2O3, KBF4, NaBF4, KPF6, NH4PF6, where A = Rb, Cs, NH4. The beaker is placed on a heating stage, heated to a temperature of 25 - 400 °C, and after a certain time, a series of fluorine-containing rare earth borate nonlinear optical crystals are obtained. To further grow, the seed crystals of the series of crystals are suspended in the solution with a thin platinum wire. To reduce water evaporation, cover the beaker with a polyethylene plate and make dozens of holes the size of millimeters on it. After a certain time, a series of centimeter-sized fluorine-containing rare earth borate nonlinear optical crystals are taken out from the solution.

[0048] The third object of the present invention is thus realized.

[0049] The series of fluorine-containing rare earth borate nonlinear optical crystal products have the advantages of high purity, easy crystal growth, transparency, no inclusions, high growth rate, low cost, and easy obtaining of large-sized crystals. The obtained crystals have relatively wide optical transmission bands, high hardness, good mechanical properties, are not prone to cracking or deliquescence, and are easy to process and store. The series of fluorine-containing rare earth borate nonlinear optical crystals obtained by using the method described in the present invention can be made into nonlinear optical devices according to the uses of the devices. It includes a device that generates at least one output radiation with a frequency different from that of the incident electromagnetic radiation after passing at least one incident electromagnetic radiation through at least one nonlinear optical device, wherein the nonlinear optical crystal therein is an A2REB3O6F2 (A = Rb, Cs, NH4, and RE = Sc, Y, La) crystal, and the molecular formulas are respectively Rb2ScB3O6F2, Cs2ScB3O6F2, (NH4)2ScB3O6F2, Rb2YB3O6F2, Cs2YB3O6F2, (NH4)2YB3O6F2, Rb2LaB3O6F2, Cs2LaB3O6F2 or (NH4)2LaB3O6F2.

Brief Description of the Drawings

[0050]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0051] The present invention will be described in detail below in conjunction with the accompanying drawings and examples, but it is not limited to the described examples. Any improvements and modifications made based on the present invention are within the protection scope of the present invention.

Example

[0052] Example 1

[0053] According to the reaction formula: 4RbF + Y2O3 + 6H3BO3 → 2Rb2YB3O6F2 + 9H2O↑, the Rb2YB3O6F2 compound was synthesized.

[0054] RbF, Y2O3, and H3BO3 were weighed in a molar ratio of 2:0.5:3, placed in a mortar, mixed and ground well, then placed in an open corundum crucible with a diameter of Φ100mm × 100mm, put into a muffle furnace, slowly heated to 400°C, kept at a constant temperature for 24 hours, cooled to room temperature, ground and then put into the muffle furnace again, further heated to 600°C, kept at a constant temperature for 24 hours, and the obtained Rb2YB3O6F2 single-phase polycrystalline powder was taken out. As a result of x-ray analysis of the product, the obtained x-ray spectrum was consistent with the x-ray spectrum obtained from the Rb2YB3O6F2 single-crystal structure.

[0055] The obtained Rb2YB3O6F2 single-phase polycrystalline powder was placed in an open platinum crucible with a diameter of Φ80mm × 80mm, heated to 1000°C at a heating rate of 30°C / h, kept at a constant temperature for 3 hours to obtain a mixed melt, then cooled to 900°C, and slowly cooled to 600°C at a rate of 0.5°C / h, the furnace was stopped, and it spontaneously crystallized to obtain an Rb2YB3O6F2 nonlinear optical crystal seed crystal.

[0056] Crystal growth in the compound melt: The obtained Rb2YB3O6F2 nonlinear optical crystal seed crystal was fixed on a seed rod, the seed crystal was lowered from the top of the crystal growth furnace, first preheated the seed crystal on the surface of the mixed melt for 10 minutes, immersed it in the liquid surface, melt-back the seed crystal in the mixed melt, kept at a constant temperature for 30 minutes, and rapidly cooled to the saturation temperature of 700°C.

[0057] After that, the temperature is decreased at a rate of 0.1 °C per day, the seed rod is rotated at a rotational speed of 10 rpm. After the crystal growth is completed, the crystal is detached from the liquid surface and cooled to room temperature at a rate of 10 °C per hour, and an Rb2YB3O6F2 crystal with a size of 20 mm × 18 mm × 10 mm can be obtained.

[0058] Example 2

[0059] According to the reaction formula: 2RbF + 3Rb2CO3 + Sc2O3 + 2ScF3 + 12H3BO3 → 4Rb2ScB3O6F2 + 3CO2↑ + 18H2O↑, the Rb2ScB3O6F2 compound is synthesized.

[0060] RbF, Rb2CO3, Sc2O3, ScF3, and H3BO3 are directly weighed as raw materials in a molar ratio of 0.5:0.75:0.25:0.5:3. The weighed raw materials and the flux LiBO2 - RbF - H3BO3 are mixed in a molar ratio of 1:15. Here, the molar ratio of LiBO2, RbF, and H3BO3 is 2:5:8. They are placed in an open platinum crucible with a diameter of Φ80 mm × 80 mm, heated to 900 °C, and kept at a constant temperature for 60 hours to obtain a mixed melt. Then, the temperature is slowly decreased to obtain an Rb2ScB3O6F2 nonlinear optical crystal seed crystal.

[0061] The obtained Rb2ScB3O6F2 nonlinear optical crystal seed crystal is fixed on the seed rod, and the seed crystal is lowered from the top of the crystal growth furnace. First, the seed crystal is preheated on the surface of the mixed melt for 10 minutes, then immersed under the liquid surface, and the seed crystal is melt - backed in the mixed melt, kept at a constant temperature for 30 minutes, and rapidly cooled to a saturation temperature of 830 °C. Then, the temperature is slowly decreased at a rate of 1 °C per day without rotating the seed rod. After the crystal grows to the desired scale, the crystal is pulled out from the melt surface and cooled to room temperature at a rate of 20 °C per hour, and then the crystal is taken out of the furnace chamber, and an Rb2ScB3O6F2 crystal with a size of 25 mm × 22 mm × 12 mm can be obtained.

[0062] Example 3

[0063] According to the reaction formula: 2Rb2CO3 + Y2O3 + 6H3BO3 + 4NH4F → 2Rb2YB3O6F2 + 2CO2↑ + 4NH3↑ + 11H2O↑, the Rb2YB3O6F2 compound is synthesized.

[0064] Weigh directly the raw materials of Rb2CO3, Y2O3, H3BO3, and NH4F in a molar ratio of 1:0.5:3:2. Mix the weighed raw materials with the flux K2CO3 - RbF - H3BO3 in a molar ratio of 1:50. Here, the molar ratio of K2CO3, RbF, and H3BO3 is 10:15:25. Put them into an open platinum crucible with Φ80mm×80mm, heat up to 400°C, keep the temperature constant for 60 hours to obtain a mixed melt, and then slowly lower the temperature to obtain the Rb2YB3O6F2 nonlinear optical crystal seed crystal.

[0065] Fix the obtained Rb2YB3O6F2 nonlinear optical crystal seed crystal on a seed rod, lower the seed crystal from the top of the crystal growth furnace. First, preheat the seed crystal on the surface of the mixed melt for 15 minutes, immerse it under the liquid surface, melt back the seed crystal in the mixed melt, keep the temperature constant for 30 minutes, and rapidly cool down to the saturation temperature of 300°C.

[0066] Slowly lower the temperature at a rate of 3°C per day, rotate the seed crystal crucible at a rotation speed of 5 rpm. After the crystal grows to the desired scale, pull the crystal out from the melt surface, lower the temperature to room temperature at a rate of 1°C / h, and then take out the crystal from the furnace chamber, and a Rb2YB3O6F2 crystal with a size of 25mm×22mm×20mm can be obtained.

[0067] Example 4

[0068] According to the reaction formula: 4Cs2CO3 + Y2O3 + 2YF3 + 12H3BO3 + 2NH4F → 4Cs2YB3O6F2 + 4CO2↑ + 2NH3↑ + 19H2O↑, the Cs2YB3O6F2 compound is synthesized.

[0069] a. Weigh the raw materials of Cs2CO3, Y2O3, YF3, H3BO3, and NH4F directly in a molar ratio of 1:0.25:0.5:3:0.5. Mix the weighed raw materials with the flux Cs2CO3-KF-H3BO3 in a molar ratio of 1:40. Here, the molar ratio of Cs2CO3, KF, and H3BO3 is 10:10:20. Put them into an open platinum crucible with a size of Φ80mm×80mm, heat up to 720°C, keep the temperature constant for 60 hours to obtain a mixed melt. Then lower the temperature to 780°C and let it crystallize spontaneously to obtain Cs2YB3O6F2 nonlinear optical crystal seeds.

[0070] Fix the obtained Cs2YB3O6F2 nonlinear optical crystal seed crystal on a seed rod, lower the seed crystal from the top of the crystal growth furnace. First, preheat the seed crystal on the surface of the mixed melt for 15 minutes, immerse it below the liquid surface, melt back the seed crystal in the mixed melt, keep the temperature constant for 30 minutes, quickly cool down to the saturation temperature of 760°C, slowly lower the temperature at a rate of 3°C per day, rotate the seed crystal crucible at a rotation speed of 5 rpm. After the crystal grows to the desired scale, pull the crystal out from the surface of the melt, lower the temperature to room temperature at a rate of 1°C / h, and then take the crystal out of the furnace chamber to obtain a Cs2YB3O6F2 crystal with a size of 25mm×22mm×20mm.

[0071] Example 5

[0072] According to the reaction formula: 4RbOH + Y2O3 + 6H3BO3 + 4NH4F → 2Rb2YB3O6F2 + 4NH3↑ + 13H2O↑, synthesize the Rb2YB3O6F2 compound.

[0073] a. Weigh the raw materials of RbOH, Y2O3, H3BO3, and NH4F directly in a molar ratio of 2:0.5:3:2. Mix the weighed raw materials with the flux Na2CO3-KF-H3BO3 in a molar ratio of 1:18. Here, the molar ratio of Na2CO3, KF, and H3BO3 is 2:6:10. Put them into an open platinum crucible with a size of Φ80mm×80mm, heat up to 900°C, keep the temperature constant for 60 hours, and let it crystallize spontaneously to obtain Rb2YB3O6F2 nonlinear optical crystal seed crystals.

[0074] The obtained Rb2YB3O6F2 nonlinear optical crystal seed crystal was fixed to a seed rod, and the seed crystal was lowered from the top of the crystal growth furnace. First, the seed crystal was preheated on the surface of the mixed melt for 15 minutes, immersed below the liquid surface, and the seed crystal was melt-back in the mixed melt, held at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 860 °C, and then the temperature was slowly decreased at a rate of 3 °C per day. The seed crystal crucible was rotated at a rotation speed of 5 rpm. After the crystal grew to the desired scale, the crystal was pulled out from the melt surface, cooled to room temperature at a rate of 1 °C / h, and then the crystal was taken out of the furnace chamber, and an Rb2YB3O6F2 crystal with a size of 25 mm × 22 mm × 20 mm was obtained.

[0075] Example 6

[0076] According to the reaction formula: 8(NH4)OH + La2O3 + 2LaF3 + 12H3BO3 + 2NH4F → 4(NH4)2LaB3O6F2 + 2NH3↑ + 23H2O↑, the (NH4)2LaB3O6F2 compound was synthesized.

[0077] (NH4)OH, La2O3, LaF3, H3BO3, and NH4F were directly weighed as raw materials in a molar ratio of 2:0.25:0.5:3:0.5 and mixed with a cosolvent. Here, the molar ratio of the cosolvent H3BO3 to La(NO3)3·6H2O was 14:6. Added to a beaker with a volume of 10 mL, and then 0.1 mL of deionized water was further added, and the solution was stirred until clear. Then the beaker was placed on a heating stage and held at a constant temperature of 25 °C, and an (NH4)2LaB3O6F2 nonlinear optical crystal was obtained after 2 days. For further growth, the seed crystal of the (NH4)2LaB3O6F2 crystal was suspended in the solution with a thin platinum wire. To reduce the evaporation of water, the beaker was covered with a polyethylene plate and dozens of holes with a millimeter size were opened on it. After 3 weeks, a centimeter-sized (NH4)2LaB3O6F2 nonlinear optical crystal was taken out of the solution.

[0078] Example 7

[0079] According to the reaction formula: 6Cs2CO3 + Y2O3 + 4YF3 + 18H3BO3 → 6Cs2YB3O6F2 + 6CO2↑ + 27H2O↑, the Cs2YB3O6F2 compound was synthesized.

[0080] Cs2CO3, Y2O3, YF3, and H3BO3 were directly weighed as raw materials in a molar ratio of 1:0.167:0.667:3. The weighed raw materials and the flux KF-Cs2CO3-H3BO3 were mixed in a molar ratio of 1:35. Here, the molar ratio of KF, Cs2CO3, and H3BO3 was 8:7:20. The mixture was placed in an open platinum crucible with a size of Φ80mm×80mm, heated to 880°C, and kept at a constant temperature for 60 hours to obtain a mixed melt, which spontaneously crystallized to obtain Cs2YB3O6F2 nonlinear optical crystal seed crystals.

[0081] The obtained Cs2YB3O6F2 nonlinear optical crystal seed crystals were fixed on a seed rod, and the seed crystals were lowered from the top of the crystal growth furnace. First, the seed crystals were preheated on the surface of the mixed melt for 15 minutes, immersed below the liquid surface, and the seed crystals were melt-back in the mixed melt, kept at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 860°C, and then the temperature was slowly decreased at a rate of 3°C per day. The seed crystal crucible was rotated at a rotation speed of 5 rpm. After the crystal grew to the desired scale, the crystal was pulled out from the surface of the melt, cooled to room temperature at a rate of 1°C / h, and then the crystal was taken out of the furnace chamber, and Cs2YB3O6F2 crystals with a size of 20mm×15mm×6mm were obtained.

[0082] Example 8

[0083] According to the reaction formula: 12CsOH + Y2O3 + 4YF3 + 18H3BO3 → 6Cs2YB3O6F2 + 33H2O↑, the Cs2YB3O6F2 compound was synthesized.

[0084] CsOH, Y2O3, ScF3, and H3BO3 were directly weighed as raw materials in a molar ratio of 2:0.167:0.667:3. The weighed raw materials and the flux CsF-H3BO3 were mixed in a molar ratio of 1:27. Here, the molar ratio of CsF to H3BO3 was 12:15. They were placed in an open platinum crucible with a size of Φ80mm×80mm, heated to a temperature of 860°C, and kept at a constant temperature for 60 hours to obtain a mixed melt, which spontaneously crystallized to obtain Cs2YB3O6F2 nonlinear optical crystal seed crystals.

[0085] The obtained Cs2YB3O6F2 nonlinear optical crystal seed crystals were fixed on a seed rod, and the seed crystals were lowered from the top of the crystal growth furnace. First, the seed crystals were preheated on the surface of the mixed melt for 15 minutes, immersed under the liquid surface, and the seed crystals were melt-back in the mixed melt, kept at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 800°C, and then the temperature was slowly decreased at a rate of 3°C per day, and the seed crystal crucible was rotated at a rotation speed of 5 rpm. After the crystal grew to the desired scale, the crystal was pulled out from the melt surface, cooled to room temperature at a rate of 1°C / h, and then the crystal was taken out of the furnace chamber, and Cs2YB3O6F2 crystals with a size of 20mm×15mm×6mm were obtained.

[0086] Example 9

[0087] According to the reaction formula: 4RbF + La2O3 + 3B2O3 → 2Rb2LaB3O6F2, the Rb2LaB3O6F2 compound was synthesized.

[0088] RbF, La2O3, and B2O3 were directly weighed as raw materials in a molar ratio of 2:0.5:1.5. The weighed raw materials and the flux RbOH-H3BO3 were mixed in a molar ratio of 1:30. Here, the molar ratio of RbOH to H3BO3 was 10:20. They were placed in an open platinum crucible with a size of Φ80mm×80mm, heated to a temperature of 800°C, and kept at a constant temperature for 60 hours to obtain a mixed melt, which spontaneously crystallized to obtain Rb2LaB3O6F2-based nonlinear optical crystal seed crystals.

[0089] The obtained series of Rb2LaB3O6F2 nonlinear optical crystal seed crystals were fixed to a seed rod, and the seed crystals were lowered from the top of the crystal growth furnace. First, the seed crystals were preheated on the surface of the mixed melt for 15 minutes, immersed below the liquid level, the seed crystals were melt-back in the mixed melt, held at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 750 °C, and then the temperature was slowly decreased at a rate of 3 °C per day. The seed crystal crucible was rotated at a rotation speed of 5 rpm. After the crystal grew to the desired scale, the crystal was pulled out from the melt surface, cooled to room temperature at a rate of 1 °C / h, and then the crystal was taken out of the furnace chamber, and an Rb2LaB3O6F2 crystal with a size of 22 mm × 20 mm × 10 mm was obtained.

[0090] Example 10

[0091] According to the reaction formula: 2CsF + 3Cs2CO3 + Y2O3 + 2YF3 + 6B2O3 → 4Cs2YB3O6F2 + 3CO2↑, the Cs2YB3O6F2 compound was synthesized.

[0092] CsF, Cs2CO3, Y2O3, YF3, and B2O3 were directly weighed as raw materials in a molar ratio of 0.5:0.75:0.25:0.5:1.5. The weighed raw materials and the flux CsF-Cs2CO3-H3BO3 were mixed in a molar ratio of 1:50. Here, the molar ratio of CsF, Cs2CO3, and B2O3 was 11:7:32. They were put into an open platinum crucible with a size of Φ80 mm × 80 mm, heated to 600 °C, held at a constant temperature for 10 hours, and spontaneously crystallized to obtain Cs2YB3O6F2 nonlinear optical crystal seed crystals.

[0093] The obtained Cs2YB3O6F2 nonlinear optical crystal seed crystals were fixed to a seed rod, and the seed crystals were lowered from the top of the crystal growth furnace. First, the seed crystals were preheated on the surface of the mixed melt for 15 minutes, immersed below the liquid level, the seed crystals were melt-back in the mixed melt, held at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 550 °C, and then the temperature was slowly decreased at a rate of 3 °C per day. The seed crystal crucible was rotated at a rotation speed of 5 rpm. After the crystal grew to the desired scale, the crystal was pulled out from the melt surface, cooled to room temperature at a rate of 1 °C / h, and then the crystal was taken out of the furnace chamber, and a Cs2YB3O6F2 crystal with a size of 13 mm × 10 mm × 7 mm was obtained.

[0094] Example 11

[0095] According to the reaction formula: 2Rb2CO3 + Y2O3 + 3B2O3 + 4NH4F → 2Rb2YB3O6F2 + 2CO2↑ + 4NH3↑ + 2H2O↑, the Rb2YB3O6F2 compound was synthesized.

[0096] a. Weigh the raw materials of Rb2CO3, Y2O3, B2O3, and NH4F directly in a molar ratio of 1:0.5:1.5:2. Mix the weighed raw materials with the flux RbF - RbOH - B2O3 in a molar ratio of 1:45. Here, the molar ratio of RbF, RbOH, and B2O3 is 15:15:15. Put them into an open platinum crucible with Φ80mm×80mm, heat up to 700°C, keep the temperature constant for 60 hours, and crystallize spontaneously to obtain the Rb2YB3O6F2 nonlinear optical crystal seed crystal.

[0097] Fix the obtained Rb2YB3O6F2 nonlinear optical crystal seed crystal on a seed rod, lower the seed crystal from the top of the crystal growth furnace. First, preheat the seed crystal on the surface of the mixed melt for 15 minutes, immerse it below the liquid surface, melt back the seed crystal in the mixed melt, keep the temperature constant for 30 minutes, rapidly cool down to the saturation temperature of 670°C, and then slowly lower the temperature at a rate of 3°C per day. Rotate the seed crystal crucible at a rotation speed of 5 rpm. After the crystal grows to the desired scale, pull the crystal out from the melt surface, lower the temperature to room temperature at a rate of 1°C / h, and then take out the crystal from the furnace chamber. A Rb2YB3O6F2 crystal with a size of 13mm×10mm×7mm can be obtained.

[0098] Example 12

[0099] According to the reaction formula: 4(NH4)2CO3 + Sc2O3 + 2ScF3 + 6B2O3 + 2NH4F → 4(NH4)2ScB3O6F2 + 4CO2↑ + 2NH3↑ + H2O↑, the (NH4)2ScB3O6F2 compound was synthesized.

[0100] a. Weigh the raw materials of (NH4)2CO3, Sc2O3, ScF3, B2O3, and NH4F directly in a molar ratio of 1:0.25:0.5:1.5:0.5, mix them with a mineralizer. Here, the molar ratio of the mineralizer H3BO3, (NH4)OH, and (NH4)2C2O4 is 10:10:10. Put them into the polytetrafluoroethylene lining of a high-pressure reactor with a volume of 21 mL, add 0.1 g of phosphoric acid, mix well to make it uniform, and obtain a mixed solution.

[0101] b. Tightly close the lid of the polytetrafluoroethylene lining containing the mixed solution in step a, put it into a clean and uncontaminated high-pressure reactor, and tightly tighten the piston of the high-pressure reactor.

[0102] c. Put the high-pressure reactor in step b into an incubator, raise the temperature to 160 °C at a heating rate of 10 °C / h, keep it at a constant temperature for 11 days, and then cool it to room temperature at a cooling rate of 4 °C / h.

[0103] d. Open the high-pressure reactor and filter the solution containing crystals to obtain the (NH4)2ScB3O6F2 nonlinear optical crystal.

[0104] Example 13

[0105] According to the reaction formula: 4(NH4)OH + Y2O3 + 3B2O3 + 4NH4F → 2(NH4)2YB3O6F2 + 4NH3↑ + 4H2O↑, synthesize the (NH4)2YB3O6F2 compound.

[0106] Weigh the raw materials of (NH4)OH, Y2O3, B2O3, and NH4F directly in a molar ratio of 2:0.5:1.5:2, mix the weighed raw materials with a flux (NH4)2C2O4 - B2O3 - CSF in a molar ratio of 1:39. Here, the molar ratio of (NH4)2C2O4, B2O3, and CSF is 7:7:25. Put them into an open platinum crucible with Φ80mm×80mm, raise the temperature to 480 °C, keep it at a constant temperature for 60 hours to obtain a mixed melt, and spontaneously crystallize to obtain the (NH4)2YB3O6F2 nonlinear optical crystal seed.

[0107] The obtained (NH4)2YB3O6F2 nonlinear optical crystal seed crystal was fixed to a seed rod, and the seed crystal was lowered from the top of the crystal growth furnace. First, the seed crystal was preheated on the surface of the mixed melt for 10 minutes, immersed below the liquid level, the seed crystal was melt-back in the mixed melt, kept at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 430 °C, and then the temperature was slowly decreased at a rate of 1 °C per day without rotating the seed rod. After the crystal grew to the desired scale, the crystal was pulled up from the melt surface, cooled to room temperature at a rate of 20 °C / h, and then the crystal was taken out of the furnace chamber, and a (NH4)2YB3O6F2 crystal with a size of 16 mm × 12 mm × 10 mm was obtained.

[0108] Example 14

[0109] According to the reaction formula: 8CsOH + La2O3 + 2LaF3 + 6B2O3 + 2NH4F → 4Cs2LaB3O6F2 + 2NH3↑ + 5H2O↑, the Cs2LaB3O6F2 compound was synthesized.

[0110] CsOH, La2O3, LaF3, B2O3, and NH4F were directly weighed as raw materials in a molar ratio of 2:0.25:0.5:1.5:0.5. The weighed raw materials were mixed with the flux CsF-LaF3-CsNO3-B2O3 in a molar ratio of 1:36. Here, the molar ratio of CsF, LaF3, CsNO3, and B2O3 was 8:5:8:15. It was placed in an open platinum crucible with Φ80 mm × 80 mm, heated to 780 °C, and spontaneously crystallized to obtain a Cs2LaB3O6F2 nonlinear optical crystal seed crystal.

[0111] The obtained Cs2LaB3O6F2 nonlinear optical crystal seed crystal was fixed to a seed rod, and the seed crystal was lowered from the top of the crystal growth furnace. First, the seed crystal was preheated on the surface of the mixed melt for 10 minutes, immersed below the liquid level, the seed crystal was melt-back in the mixed melt, kept at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 760 °C, and then the temperature was slowly decreased at a rate of 1 °C per day without rotating the seed rod. After the crystal grew to the desired scale, the crystal was pulled up from the melt surface, cooled to room temperature at a rate of 20 °C / h, and then the crystal was taken out of the furnace chamber, and a Cs2LaB3O6F2 crystal with a size of 16 mm × 12 mm × 10 mm was obtained.

[0112] Example 15

[0113] According to the reaction formula: 6Rb2CO3 + La2O3 + 4LaF3 + 9B2O3 → 6Rb2LaB3O6F2 + 6CO2↑, the Rb2LaB3O6F2 compound was synthesized,

[0114] Rb2CO3, La2O3, LaF3, and H3BO3 were directly weighed as raw materials in a molar ratio of 1:0.167:0.667:1.5. The weighed raw materials were mixed with the flux CsF-LaF3-KOH-B2O3 in a molar ratio of 1:26. Here, the molar ratio of CsF, LaF3, KOH, and B2O3 was 10:3:5:8. It was placed in an open platinum crucible with Φ80mm×80mm, heated to 950°C, held at a constant temperature for 10 hours, and spontaneously crystallized to obtain Rb2LaB3O6F2 nonlinear optical crystal seed crystals,

[0115] The obtained Rb2LaB3O6F2 nonlinear optical crystal seed crystals were fixed on a seed rod, and the seed crystals were lowered from the top of the crystal growth furnace. First, the seed crystals were preheated on the surface of the mixed melt for 10 minutes, immersed below the liquid surface, and the seed crystals were melt-back in the mixed melt, held at a constant temperature for 30 minutes, rapidly cooled to the saturation temperature of 930°C, and then the temperature was slowly lowered at a rate of 1°C / day without rotating the seed rod. After the crystal grew to the desired scale, the crystal was pulled out from the surface of the melt, cooled to room temperature at a rate of 20°C / h, and then the crystal was taken out of the furnace chamber, and Rb2LaB3O6F2 crystals with a size of 16mm×12mm×10mm were obtained.

[0116] Example 16

[0117] According to the reaction formula: 12CsOH + Y2O3 + 4YF3 + 9B2O3 → 6Cs2YB3O6F2 + 6H2O↑, the Cs2YB3O6F2 compound was synthesized,

[0118] a. Weigh the raw materials of CsOH, Y2O3, YF3, and B2O3 directly in a molar ratio of 2:0.167:0.667:1.5. Mix the weighed raw materials with the flux Cs2CO3 - YF3 - KF - B2O3 in a molar ratio of 1:26. Here, the molar ratio of Cs2CO3, YF3, KF, and B2O3 is 10:3:5:8. Put them into an open platinum crucible with a size of Φ80mm×80mm, heat up to 780°C, keep the temperature constant for 60 hours, and crystallize spontaneously to obtain Cs2YB3O6F2 nonlinear optical crystal seed crystals.

[0119] Fix the obtained Cs2YB3O6F2 nonlinear optical crystal seed crystals on a seed rod, lower the seed crystal from the top of the crystal growth furnace. First, preheat the seed crystal on the surface of the mixed melt for 10 minutes, immerse it below the liquid surface, melt back the seed crystal in the mixed melt, keep the temperature constant for 30 minutes, rapidly cool down to the saturation temperature of 730°C, and then slowly lower the temperature at a rate of 1°C per day without rotating the seed rod. After the crystal grows to the desired scale, pull the crystal out from the melt surface, lower the temperature to room temperature at a rate of 20°C / h, and then take the crystal out of the furnace chamber, and a Cs2YB3O6F2 crystal with a size of 16mm×12mm×10mm can be obtained.

[0120] Example 17

[0121] According to the reaction formula: 2RbF + La(NO3)3·6H2O + 3H3BO3 → Rb2LaB3O6F2 + 6H2O↑ + 3NH3↑ + 6O2↑, synthesize the Rb2LaB3O6F2 compound.

[0122] Weigh the raw materials of RbF, La(NO3)3·6H2O, and H3BO3 directly in a molar ratio of 2:1:3. Mix the weighed raw materials with the flux RbF - H3BO3 in a molar ratio of 1:35. Here, the molar ratio of RbF and H3BO3 is 13:22. Put them into an open platinum crucible with a size of Φ80mm×80mm, heat up to 710°C, keep the temperature constant for 60 hours to obtain a mixed melt, and crystallize spontaneously to obtain a series of Rb2LaB3O6F2 - containing nonlinear optical crystal seed crystals.

[0123] The obtained series of Rb2LaB3O6F2 nonlinear optical crystal seed crystals were fixed on a seed rod, and the seed crystals were lowered from the top of the crystal growth furnace. First, the seed crystals were preheated on the surface of the mixed melt for 15 minutes, immersed below the liquid surface, and the seed crystals were melt-back in the mixed melt, kept at a constant temperature for 30 minutes, and rapidly cooled to the saturation temperature of 690 °C.

[0124] The temperature was slowly decreased at a rate of 3 °C / day, and the seed crystal crucible was rotated at a rotation speed of 5 rpm. After the crystal grew to the desired scale, the crystal was pulled up from the melt surface, cooled to room temperature at a rate of 1 °C / h, and then the crystal was taken out of the furnace chamber. As a result, an Rb2LaB3O6F2 crystal with a size of 22 mm × 18 mm × 14 mm was obtained.

[0125] Example 18

[0126] According to the reaction formula: 2(NH4)OH + Y(NO3)3·6H2O + 3H3BO3 + 2NH4F → (NH4)2YB3O6F2 + 8H2O↑ + 5NH3↑ + 6O2↑, the (NH4)2YB3O6F2 compound was synthesized.

[0127] a. The raw materials of (NH4)OH, Y(NO3)3·6H2O, H3BO3, and NH4F were directly weighed in a molar ratio of 2:1:3:2, mixed with a mineralizer. Here, the molar ratio of the mineralizer H3BO3, NH4OH, and (NH4)2C2O4 was 10:2:10. It was put into the polytetrafluoroethylene lining of a high-pressure reaction kettle with a volume of 21 mL, and 0.1 g of phosphoric acid was further added and mixed well to make it uniform to obtain a mixed solution.

[0128] b. The lid of the polytetrafluoroethylene lining containing the mixed solution in step a was tightly fastened, put into a clean and uncontaminated high-pressure reaction kettle, and the piston of the high-pressure reaction kettle was tightly fastened.

[0129] c. The high-pressure reaction kettle in step b was placed in an incubator, heated to 160 °C at a heating rate of 10 °C / h, kept at a constant temperature for 11 days, and cooled to room temperature at a cooling rate of 4 °C / h.

[0130] d. Open the high-pressure reactor and filter the solution containing crystals to obtain (NH4)2YB3O6F2 nonlinear optical crystals.

[0131] Example 19

[0132] According to the reaction formula: Cs2CO3 + Sc(NO3)3·6H2O + 3H3BO3 + 2NH4F → Cs2ScB3O6F2 + 7H2O↑ + 5NH3↑ + 6O2↑ + CO2↑, synthesize the Cs2ScB3O6F2 compound.

[0133] Directly weigh the raw materials Cs2CO3, Sc(NO3)3·6H2O, H3BO3, and NH4F in a molar ratio of 1:1:3:2, and mix the weighed raw materials with the flux LiF-Cs2CO3-H3BO3 in a molar ratio of 1:33. Here, the molar ratio of LiF, Cs2CO3, and H3BO3 is 7:8:18. Put them into an open platinum crucible with Φ80mm×80mm, heat up to 750°C, keep the temperature constant for 60 hours, and crystallize spontaneously to obtain a series of nonlinear optical crystal seeds containing Cs2ScB3O6F2.

[0134] Fix the obtained series of Cs2ScB3O6F2 nonlinear optical crystal seeds on the seed rod, lower the seed crystal from the top of the crystal growth furnace, first preheat the seed crystal on the surface of the mixed melt for 15 minutes, immerse it under the liquid surface, melt back the seed crystal in the mixed melt, keep the temperature constant for 30 minutes, and rapidly cool down to the saturation temperature of 720°C.

[0135] Slowly lower the temperature at a rate of 3°C per day, rotate the seed crystal crucible at a rotation speed of 5 rpm. After the crystal grows to the desired scale, pull the crystal out from the surface of the melt, lower the temperature to room temperature at a rate of 1°C per hour, and then take out the crystal from the furnace chamber to obtain a Cs2ScB3O6F2 crystal with a size of 22mm×18mm×14mm.

[0136] Example 20

[0137] Any of the Rb2ScB3O6F2, Cs2ScB3O6F2, (NH4)2ScB3O6F2, Rb2YB3O6F2, Cs2YB3O6F2, (NH4)2YB3O6F2, Rb2LaB3O6F2, Cs2LaB3O6F2 or (NH4)2LaB3O6F2 crystals obtained in Examples 1 to 19 were processed into a single crystal device in the alignment direction, set at the position 3 as shown in Fig. 4, and at room temperature, a Nd:YAG Q-switched laser light source with a wavelength of 1064 nm was used as the pump source, incident on the Rb2ScB3O6F2, Cs2ScB3O6F2, (NH4)2ScB3O6F2, Rb2YB3O6F2, Cs2YB3O6F2, (NH4)2YB3O6F2, Rb2LaB3O6F2, Cs2LaB3O6F2 or (NH4)2LaB3O6F2 nonlinear optical crystal 3 to generate a second harmonic light with a wavelength of 532 nm. The output beam 4 contains infrared light with a wavelength of 1064 nm and second harmonic light with a wavelength of 532 nm. After filtering with the filter 5, a laser with a wavelength of 532 nm is obtained.

[0138] Example 21

[0139] Any of the Rb2ScB3O6F2, Cs2ScB3O6F2, (NH4)2ScB3O6F2, Rb2YB3O6F2, Cs2YB3O6F2, (NH4)2YB3O6F2, Rb2LaB3O6F2, Cs2LaB3O6F2 or (NH4)2LaB3O6F2 crystals obtained in Examples 1 to 19 were processed into a single crystal device in the alignment direction, set at the position 3 as shown in Fig. 4, and at room temperature, a Nd:YAG Q-switched laser light source with a wavelength of 532 nm was used as the pump source, incident on the Rb2ScB3O6F2, Cs2ScB3O6F2, (NH4)2ScB3O6F2, Rb2YB3O6F2, Cs2YB3O6F2, (NH4)2YB3O6F2, Rb2LaB3O6F2, Cs2LaB3O6F2 or (NH4)2LaB3O6F2 nonlinear optical crystal 3 to generate a second harmonic light with a wavelength of 266 nm. The output beam 4 contains second harmonic light with wavelengths of 532 nm and 266 nm. After filtering with the filter 5, a laser with a wavelength of 266 nm is obtained.

[0140] Example 22

[0141] Any of the Rb2ScB3O6F2, Cs2ScB3O6F2, (NH4)2ScB3O6F2, Rb2YB3O6F2, Cs2YB3O6F2, (NH4)2YB3O6F2, Rb2LaB3O6F2, Cs2LaB3O6F2 or (NH4)2LaB3O6F2 nonlinear optical crystals obtained in Examples 1 to 19 are made into single crystal devices through directional cutting and polishing processes, and a 1064 nm Nd:YAG Q-switched laser light source is used as a pump source to generate a laser output shorter than 266 nm.

Explanation of symbols

[0142] 1 Laser 2 Emitted beam 3 Series of fluoride-containing rare earth borate nonlinear optical crystals 4 Output beam 5 Filter

Claims

Claim 1 A series of fluorine-containing rare earth borate compounds, wherein the general molecular formula of the series of fluorine-containing rare earth borate compounds is A ２ REB ３ O ６ F ２ where A = Rb, Cs, NH ４ and RE = Sc, Y, La, and their molecular formulas are respectively Rb ２ ScB ３ O ６ F ２ , Cs ２ ScB ３ O ６ F ２ , (NH ４ ) ２ ScB ３ O ６ F ２ , Rb ２ YB ３ O ６ F ２ , Cs ２ YB ３ O ６ F ２ , (NH ４ ) ２ YB ３ O ６ F ２ , Rb ２ LaB ３ O ６ F ２ , Cs ２ LaB ３ O ６ F ２ or (NH ４ ) ２ LaB ３ O ６ F ２ and the molecular weight is from 247.46 to 571.14, a series of fluorine-containing rare earth borate compounds characterized by this. Claim 2 The method for preparing a series of fluorine-containing rare earth borate compounds according to claim 1, characterized by being prepared using a solid-phase reaction method and a hydrothermal method. Claim 3 A = Rb, Cs, NH ４ Mix a compound containing A, a compound containing RE = Sc, Y, La, a boron-containing compound, and a fluorine-containing compound, where the molar ratio of element A in the A-containing compound, element RE in the RE-containing compound, element boron in the boron-containing compound, and element fluorine in the fluorine-containing compound is 1.5 to 2.2: 0.8 to 1.5: 2.5 to 3.5: 1.5 to 2.

2. Further, the raw materials of the A-containing compound, RE-containing compound, boron-containing compound, and fluorine-containing compound are uniformly mixed, put into a muffle furnace after polishing, calcined to remove moisture and gas in the raw materials, cooled to room temperature, taken out, put into a muffle furnace after polishing and fired to obtain a series of single-phase polycrystalline powders of fluorine-containing rare earth borate compounds, A = Rb, Cs, NH ４ Put the compound containing A = Rb, Cs, NH, the compound containing RE = Sc, Y, La, the boron-containing compound, and the fluorine-containing compound into the polytetrafluoroethylene lining of the autoclave, add deionized water and a mineralizer, mix well to make it uniform to obtain a mixed solution, put the autoclave into an incubator and heat it, then cool it down to room temperature, and filter the solution containing the powder to obtain a series of single-phase polycrystalline powders of fluorine-containing rare earth borate compounds. Here, the molar ratio of element A in the A-containing compound, element RE in the RE-containing compound, element boron in the boron-containing compound, and element fluorine in the fluorine-containing compound is 1.5 to 2.2: 0.8 to 1.5: 2.5 to 3.5: 1.5 to 2.

2. A series of fluorine-containing rare earth borate compounds prepared by the hydrothermal method as described above, characterized by the above. wherein A = Rb, Cs, NH ４ The compound contains at least one of AOH, A ２ O, and an alkali metal salt. The alkali metal salt contains at least one of AF, ACl, ABr, ANO ３ , A ２ C ２ O ２ , A ２ CO ３ , AHCO ３ , A ２ SO ４ , wherein A = Rb, Cs, NH ４ and The RE = Sc, Y, La-containing compound is RE ２ O ３ , REF ３ , RE(NO ３ ) ３ ·6H ２ O and contains The boron-containing compound contains B ２ O ３ and at least one of H ３ BO ３ and borate. The borate contains at least one of ABO ２ ABO ３ A ３ BO ３ A ２ B ４ O ７ where A = Rb, Cs, NH ４ and The fluorine-containing compound is AF, REF ３ where A = Rb, Cs, NH ４ and RE = Sc, Y, La, and other fluorine-containing compounds are KBF ４ , NaBF ４ , KPF ６ , NH ４ PF ６ and includes at least one of them, and the series of fluorine-containing rare earth borate compounds according to claim 2, prepared by a solid-phase synthesis method, characterized in that. Claim 4 A series of fluorine-containing rare earth borate nonlinear optical crystals, wherein the chemical formula of the series of crystals is A ２ REB ３ O ６ F ２ where A = Rb, Cs, NH ４ and RE = Sc, Y, La, and the molecular formulas are respectively Rb ２ ScB ３ O ６ F ２ , Cs ２ ScB ３ O ６ F ２ , (NH ４ ) ２ ScB ３ O ６ F ２ , Rb ２ YB ３ O ６ F ２ , Cs ２ YB ３ O ６ F ２ , (NH ４ ) ２ YB ３ O ６ F ２ , Rb ２ LaB ３ O ６ F ２ , Cs ２ LaB ３ O ６ F ２ or (NH ４ ) ２ LaB ３ O ６ F ２ and all crystallize in the orthorhombic system with the space group Amm2, and the cell parameters are a = 2.7182(4) - 4.9617(8) Å, b = 7.7013(5) - 9.9742(6) Å, c = 10.2634(1) - 12.904(3) Å, Z = 2, characterized by a series of fluorine-containing rare earth borate nonlinear optical crystals. Claim 5 The method for preparing a fluorine-containing rare earth borate nonlinear optical crystal according to claim 4, characterized by growing the fluorine-containing rare earth borate nonlinear optical crystal by a high-temperature melt method, a hydrothermal method or a solution method. Claim 6 The high-temperature melt method grows a series of fluorine-containing rare-earth borate nonlinear optical crystals A ２ REB ３ O ６ F ２ where A = Rb, Cs, NH ４ and RE = Sc, Y, La. The specific operations are as follows: a single-phase polycrystalline powder of a series of fluorine-containing rare-earth borate compounds or a mixture of a single-phase polycrystalline powder of a series of fluorine-containing rare-earth borate compounds and a flux, or a mixture of a direct A-containing compound, a RE-containing compound, a boron-containing compound, and a fluorine-containing compound, or a mixture of an A-containing compound, a RE-containing compound, a boron-containing compound, a fluorine-containing compound, and a flux is heated to melting to obtain a mixed melt. Then, the crucible containing the mixed melt is placed in a crystal growth furnace and heated, and the temperature is lowered to the saturation temperature point. At this time, the seed rod is inserted below the liquid surface, and then the seed rod is pulled out of the liquid surface before the melt solidifies to prepare a series of fluorine-containing rare-earth borate nonlinear optical crystals. The hydrothermal method grows a series of fluorine-containing rare earth borate nonlinear optical crystals A ２ REB ３ O ６ F ２ where A = Rb, Cs, NH ４ and RE = Sc, Y, La. The specific operations are as follows: A single-phase polycrystalline powder of a series of fluorine-containing rare earth borate compounds or a mixture of a single-phase polycrystalline powder of a series of fluorine-containing rare earth borate compounds and a mineralizer, or directly a mixture of an A-containing compound, a RE-containing compound, a boron-containing compound, and a fluorine-containing compound or a mixture of an A-containing compound, a RE-containing compound, a boron-containing compound, a fluorine-containing compound, and a mineralizer is placed into the polytetrafluoroethylene lining of a high-pressure reactor, and further deionized water is added and mixed thoroughly to make it uniform to obtain a mixed solution. The polytetrafluoroethylene lining is placed into the high-pressure reactor, and the high-pressure reactor is placed into an incubator for heating and then cooled down to room temperature. When the solution containing crystals is filtered, a series of transparent fluorine-containing rare earth borate nonlinear optical crystals are obtained. The solution method involves growing a series of fluorine-containing rare earth borate nonlinear optical crystals A ２ REB ３ O ６ F ２ where A = Rb, Cs, NH ４ and RE = Sc, Y, La. The specific operations are as follows: putting a single-phase polycrystalline powder of a series of fluorine-containing rare earth borate compounds or a mixture of a single-phase polycrystalline powder of a series of fluorine-containing rare earth borate compounds and a cosolvent, or directly a mixture of an A-containing compound, an RE-containing compound, a boron-containing compound, and a fluorine-containing compound, or a mixture of an A-containing compound, an RE-containing compound, a boron-containing compound, a fluorine-containing compound, and a cosolvent into a beaker, adding deionized water and dissolving it, stirring the solution until it is clear, and placing the beaker in the air to evaporate the solution to grow a series of fluorine-containing rare earth borate nonlinear optical crystals. The method for preparing a series of fluorine-containing rare earth borate nonlinear optical crystals according to claim 5, characterized by the above. Claim 7 The high-temperature melt method grows a series of fluorine-containing rare earth borate nonlinear optical crystals, and the molar ratio of the single-phase polycrystalline powder of the series of fluorine-containing rare earth borate compounds to the flux is 1:0 to 50, or here A = Rb, Cs, NH ４ The molar ratio of element A in the containing compound, element RE in the RE = Sc, Y, La-containing compound, element boron in the boron-containing compound, element fluorine in the fluorine-containing compound to the flux is 1.5 to 2.2:0.8 to 1.5:2.5 to 3.5:1.5 to 2.2:0 to 50, where the flux is alkali metal salts, namely alkali metal carbonates, alkali metal nitrates, alkali metal sulfates, alkali metal oxalates, alkali metal borates, alkali metal phosphates, alkali metal halides, alkali metal fluoroborates, alkali metal metaborates, and alkali metal oxides, alkali metal hydroxides, and one or more of yttrium fluoride, yttrium nitrate, yttrium oxide, lanthanum fluoride, lanthanum nitrate, lanthanum oxide, scandium fluoride, scandium nitrate, scandium oxide, boron oxide, boric acid, phosphoric acid, lead oxide, lead fluoride, molybdenum oxide, bismuth oxide. The hydrothermal method grows a series of fluorine-containing rare earth borate nonlinear optical crystals, and the molar ratio of the series of fluorine-containing rare earth borate compound single-phase polycrystalline powder to the mineralizer is 1:0 to 30, or here A = Rb, Cs, NH ４ The molar ratio of element A in the A-containing compound, element RE in the RE = Sc, Y, La-containing compound, element boron in the boron-containing compound, element fluorine in the fluorine-containing compound to the mineralizer is 1.5 to 2.2:0.8 to 1.5:2.5 to 3.5:1.5 to 2.2:0 to 30, and the mineralizer is AOH, A ２ O, AF, ACl, ABr, ABF ４ , A ３ PO ４ , A ３ BO ３ , ANO ３ , A ２ C ２ O ４ , A ２ CO ３ , AHCO ３ , A ２ SO ４ , Y(NO ３ ) ３ ・6H ２ O, La(NO ３ ) ３ ・6H ２ O, Sc(NO ３ ) ３ ・6H ２ O, B ２ O ３ , KBF ４ , NaBF ４ , KPF ６ , NH ４ PF ６ contains at least one or more of these, where A = Rb, Cs, NH ４ and The aqueous solution method grows a series of fluorine-containing rare earth borate nonlinear optical crystals, where the molar ratio of the series of fluorine-containing rare earth borate compound single-phase polycrystalline powder to the cosolvent is 1:0 to 20, or here, the molar ratio of element A in the A-containing compound, element RE in the RE-containing compound, element boron in the boron-containing compound, element fluorine in the fluorine-containing compound, and the cosolvent is 1.5 to 2.2:0.8 to 1.5:2.5 to 3.5:1.5 to 2.2:0 to 20, and the cosolvent is AOH, A ２ O, AF, ACl, ABr, ABF ４ 、A ３ PO ４ 、A ３ BO ３ 、ANO ３ 、A ２ C ２ O ４ 、A ２ CO ３ 、AHCO ３ 、A ２ SO ４ 、A ２ HPO ４ 、AH ２ PO ４ 、Y(NO ３ ) ３ ・6H ２ O、La(NO ３ ) ３ ・6H ２ O、Sc(NO ３ ) ３ ・6H ２ O、B ２ O ３ 、KBF ４ 、NaBF ４ 、KPF ６ 、NH ４ PF ６ includes at least one or more of them, where A = Rb, Cs, NH ４ and is, a method for preparing a series of fluorine-containing rare earth borate nonlinear optical crystals according to claim 6. Claim 8 A device that includes passing at least one incident electromagnetic radiation through at least one nonlinear optical crystal and generating at least one output radiation having a frequency different from that of the incident electromagnetic radiation, wherein the nonlinear optical crystal therein is the series of fluorine-containing rare earth borate nonlinear optical crystals A ２ REB ３ O ６ F ２ where A = Rb, Cs, NH ４ and RE = Sc, Y, La, a nonlinear optical device characterized by that. Claim 9 Use of a series of fluorine-containing rare earth borate nonlinear optical crystals according to claim 4 in the manufacture of a multi-wavelength band doubling device or an optical element. Claim 10 The series of fluorine-containing rare earth borate nonlinear optical crystals are used in nonlinear optical devices such as second harmonic generators, upper and lower frequency converters, optical parametric oscillators, laser inverter devices, and laser communications. The use of a series of fluorine-containing rare earth borate nonlinear optical crystals according to claim 4, characterized by this.

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