A barium borate nonlinear crystal material, its preparation method and application

Abstract

This application discloses a barium borate nonlinear crystal material, the chemical formula of which is Ba4B. 14 O 25 This barium borate crystal exhibits a strong frequency doubling effect, with its powder SHG coefficient being 2.4 times that of KH2PO4 (KDP), and it can achieve phase matching, making it a nonlinear optical material with potential application value.

Description

Technical Field

[0001] This application relates to a barium borate nonlinear crystal material, its preparation method, and its application, belonging to the field of nonlinear crystal material technology. Background Technology

[0002] Nonlinear optics has permeated all areas of modern optics and laser technology, playing an increasingly important role in many scientific and high-tech fields such as all-solid-state lasers, ultrafast lasers, spectrometers, optical storage, and computing through frequency conversion, electro-optic modulation, and photorefractive effects. With the rapid development of laser technology, there is a greater demand and higher requirements for nonlinear optical (NLO) crystal materials applicable to the ultraviolet (UV) and deep ultraviolet (DUV) light regions. Among these, borates have a high probability of obtaining non-centrosymmetric structures. The significant difference in electronegativity between B and O atoms is considered the reason for their high transmittance in shorter wavelength regions. Furthermore, the conjugated π orbitals and high anisotropy of electrons in BO / FFBBs are conducive to obtaining a large second-order magnetic susceptibility, allowing them to simultaneously possess a large second-order NLO coefficient and a moderate birefringence. Therefore, they are considered excellent candidate materials for generating ultraviolet and deep ultraviolet harmonics. Numerous borate-based NLO candidate materials are being developed, and currently, borate nonlinear optical crystals used in practical applications include β-BaB₂O₄ (BBO), LiB₃O₅ (LBO), CsB₃O₅ (CBO), and CsLiB₆O₄. 10 Crystals such as CLBO and KBe2BO3F2 (KBBF) exist. However, these crystals suffer from significant drawbacks and limitations, including long growth cycles, hygroscopicity, and severe layered growth habits, which greatly affect their applications. Therefore, designing and synthesizing new ultraviolet and deep ultraviolet nonlinear optical crystals remains an important and challenging task.

[0003] In the exploration and development of novel ultraviolet and deep ultraviolet nonlinear optical crystals, researchers continue to choose borates, which possess a wide transmission spectral range, a high laser damage threshold, and good chemical and mechanical stability. It is well known that alkali metal / alkaline earth metal cations without dd electron transitions can increase the band gap of borates, thereby broadening the transmission range and allowing their absorption cutoff edge to reach the deep ultraviolet region. Therefore, this invention introduces alkaline earth metal barium cations into the borate system, synthesizing a barium borate nonlinear optical crystal applicable to both ultraviolet and deep ultraviolet light. Summary of the Invention

[0004] According to one aspect of this application, a barium borate nonlinear crystal material is provided, which exhibits a strong frequency doubling effect, has a powder SHG coefficient that is 2.4 times that of KH2PO4 (KDP), and can achieve phase matching, making it a nonlinear optical material with potential application value.

[0005] The technical solution adopted in this application is as follows:

[0006] A barium borate nonlinear crystal material, wherein the chemical formula of the barium borate nonlinear crystal material is Ba4B. 14 O 25 .

[0007] Optionally, the barium borate nonlinear crystal material has a monoclinic crystal system, a space group of Cm, and a unit cell parameter of . α=γ=90°, β=118.7°, Z=4.

[0008] Optionally, the cell parameters of the crystal junction of the barium borate nonlinear crystal material are as follows:

[0009]

[0010] Optionally, the cell parameters of the crystal junction of the barium borate nonlinear crystal material are as follows:

[0011]

[0012] Optionally, the ultraviolet absorption cutoff wavelength of the barium borate nonlinear crystal material is less than 200 nm.

[0013] Optionally, the barium borate nonlinear crystal material has a melting point of 900°C.

[0014] Optionally, the barium borate nonlinear crystal material emits green light with a center wavelength of 532 nm when irradiated by a 1064 nm laser.

[0015] According to another aspect of this application, a method for preparing the above-mentioned barium borate nonlinear crystal material is provided.

[0016] When the barium borate nonlinear crystal material is polycrystalline, the following steps are included:

[0017] S11. Grind the raw materials containing barium compounds and boron compounds, and heat them to 290-310℃ for 43-52 hours.

[0018] S12. Grind the intermediate product from step S11 and heat it to 390-410℃ for 11-13 hours.

[0019] S13. Grind the intermediate product from step S12 and heat it to 590-610℃ for 11-13 hours.

[0020] S14. Grind the intermediate product from step S13 and heat it to 730-750℃ for 22-26 hours to obtain barium borate nonlinear crystal material.

[0021] In steps S11 to S14, the grinding speed is 380 to 420 rpm, and the grinding time is 0.8 to 1.2 h.

[0022] Optionally, the step further includes grinding the barium borate nonlinear crystal material into a single-phase polycrystalline powder.

[0023] When the barium borate nonlinear crystal material is a single crystal, the following steps are included:

[0024] S21. Grind the raw materials containing barium compounds, boron compounds, lead compounds, and antimony compounds, and heat them to 400-500℃ for 35-60 hours.

[0025] S22. Grind the intermediate product from step S21, heat it to 800-900℃ and react it for 12-40 hours, then slowly cool it down to obtain barium borate nonlinear crystal material.

[0026] In steps S21 and S22, the heating rate is 0.5 to 10 °C / min.

[0027] The slow cooling process includes: cooling to 680-780°C at a cooling rate of 0.5-3°C / h, and then cooling to 300-400°C at a cooling rate of 4-15°C / h.

[0028] Optionally, the barium borate nonlinear crystal material obtained after slow cooling is a light gray transparent bulk single crystal.

[0029] Optionally, during the slow cooling process, the cooling rate is selected from any value among 0.5℃ / h, 0.8℃ / h, 1.2℃ / h, 2℃ / h, 3℃ / h, 4℃ / h, 5℃ / h, 6℃ / h, 7℃ / h, 8℃ / h, 9℃ / h, 10℃ / h, 11℃ / h, 12℃ / h, 13℃ / h, 14℃ / h, and 15℃ / h, or a range between any two.

[0030] Optionally, in steps S21 and S22, the heating rate is selected from any value among 0.5℃ / min, 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min, and 10℃ / min, or any range between the two.

[0031] Optionally, the slow cooling process includes: cooling to 680-780°C at a cooling rate of 0.8-1.2°C / h, and then cooling to 340-360°C at a cooling rate of 7-9°C / h.

[0032] Optionally, step S22 involves grinding the intermediate product from step S1, heating it to 830–850°C and reacting it for 22–26 hours to obtain a mixed melt, and then slowly cooling it to obtain a barium borate nonlinear crystal material.

[0033] Optionally, the molar ratio of barium to boron in the barium-containing compound and the boron-containing compound, calculated as elements, is 1:(3.3 to 3.7).

[0034] Optionally, the molar ratio of barium, boron, lead, and antimony in the barium-containing compound, boron-containing compound, lead-containing compound, and antimony-containing compound, calculated by element, is 1:(2-4):(0.2-0.5):(0.25-0.45).

[0035] Optionally, the molar ratio of barium, boron, lead, and antimony in the barium-containing compound, boron-containing compound, lead-containing compound, and antimony-containing compound, calculated by element, is 1:(2.5-3):(0.25-0.35):(0.3-0.4).

[0036] Optionally, the boron-containing compound is selected from at least one of boron oxide and boric acid.

[0037] Optionally, the barium-containing compound is selected from at least one of barium carbonate, barium oxide, barium nitrate, barium fluoride, and barium hydroxide.

[0038] Optionally, the lead-containing compound is selected from at least one of lead oxide, lead carbonate, lead fluoride, and lead nitrate.

[0039] Optionally, the antimony-containing compound is selected from at least one of antimony trioxide, antimony pentoxide, and antimony trifluoride.

[0040] Optionally, the boron-containing compound is boric acid.

[0041] Optionally, the barium-containing compound is barium carbonate.

[0042] Optionally, the lead-containing compound is lead oxide.

[0043] Optionally, the antimony-containing compound is antimony trioxide.

[0044] Lead-containing compounds and antimony-containing compounds are used as cosolvents.

[0045] Optionally, the grinding is ball milling.

[0046] According to another aspect of this application, at least one of the above-described barium borate nonlinear crystal materials and the barium borate nonlinear crystal materials prepared by the above-described preparation method is provided as an application of ultraviolet or deep ultraviolet nonlinear optical crystal materials.

[0047] The beneficial effects that this application can produce include:

[0048] (1) The barium borate nonlinear crystal material provided in this application has the following excellent properties: 1) It outputs strong 532nm green light under 1064nm laser irradiation, and its powder SHG coefficient is 2.4 times that of KH2PO4 (KDP), and it can achieve phase matching. It has great potential value as an ultraviolet and deep ultraviolet nonlinear optical material; 2) It has high transmittance in the 200-2000nm spectral range, and its ultraviolet absorption cutoff wavelength is <200nm; 3) It can be stabilized up to 900℃ and has excellent thermal stability.

[0049] (2) The preparation method of barium borate nonlinear crystal material provided in this application can be to synthesize high-purity polycrystalline sample powder by high-temperature solid-state synthesis method and to prepare its high-crystallinity transparent blocky single crystal with light gray color by spontaneous crystallization high-temperature flux method. Attached Figure Description

[0050] Figure 1 Sample 1 obtained in Example 1 of this application # Comparison of X-ray diffraction patterns obtained by fitting the crystal structure resolved by single-crystal X-ray diffraction with patterns obtained by XRD testing;

[0051] Figure 2 Sample 1 obtained in Example 1 of this application # The ultraviolet-visible-near-infrared diffuse reflectance spectrum;

[0052] Figure 3 Sample 1 obtained in Example 1 of this application # Thermogravimetrics;

[0053] Figure 4 Sample 1 obtained in Example 1 of this application # Intensity maps of SHG at different particle sizes under 1064nm laser light. Detailed Implementation

[0054] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0055] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0056] Example 1: Polycrystalline Preparation of Barium Borate Nonlinear Crystal Material

[0057] (1) Polycrystalline sample 1 #Synthesis: Accurately weigh BaCO3 (0.395 g, 2 mmol) and H3BO3 (0.433 g, 7 mmol) and place them in a zirconia ball mill jar. Grind thoroughly in a ball mill for one hour (400 rpm, the same below). Remove the mixture and place it in a platinum crucible. Place it in a muffle furnace and heat to 300℃ for 48 hours. Remove the mixture and ball mill it a second time for one hour. Place it in a muffle furnace and heat to 400℃ for 12 hours. Remove the mixture and ball mill it a third time for one hour. Place it in a muffle furnace and heat to 600℃ for 12 hours. Remove the mixture and ball mill it a fourth time for one hour. Place it in a muffle furnace and heat to 740℃ for 24 hours. After cooling to room temperature, remove the mixture and grind it in an agate mortar to obtain a single-phase polycrystalline powder sample of barium borate nonlinear crystal material.

[0058] Example 2: Single Crystal Preparation of Barium Borate Nonlinear Crystal Material

[0059] Single crystal sample 2 # Preparation: H3BO3 (0.495 g, 8 mmol), BaCO3 (0.592 g, 3 mmol), PbO (0.223 g, 1 mmol), and Sb2O3 (0.146 g, 0.5 mmol) were thoroughly ground in an agate mortar and then placed in a platinum crucible. The mixture was then transferred to a muffle furnace and heated to 500 °C at a rate of 1 °C / min, held at that temperature for 48 hours. Afterward, the mixture was removed, ground evenly, and then returned to the muffle furnace, where it was heated to 840 °C at the same rate and held at that temperature for 24 hours to obtain a mixed melt. Cooling was performed in two steps: first, the temperature was slowly reduced to 740 °C (cooling rate of 1 °C / h), and then further reduced to 350 °C (cooling rate of 8 °C / h). The power was then disconnected, allowing it to cool naturally to room temperature, yielding a light gray, transparent, blocky barium borate nonlinear crystal. Lead-containing compounds and antimony-containing compounds were used as fluxes. (See attached diagram) Figure 1 As shown, the X-ray diffraction pattern obtained by fitting the crystal structure resolved by single-crystal X-ray diffraction and the pattern obtained by XRD testing are consistent in all peak values.

[0060] Test Example 1: Ultraviolet-Visible Diffuse Reflectance Absorption Spectroscopy Test

[0061] Sample 1 obtained in Example 1 # As a representative example, barium borate crystal Ba4B 14 O 25 Diffuse reflectance absorption spectroscopy was performed. The UV-Vis diffuse reflectance spectra of the compounds were measured at room temperature using a PerkinElmer Lambda-950 UV-Vis spectrophotometer. A BaSO4 plate (100% reflectance) was used as the background standard. The test results are as follows: Figure 2 As shown, this indicates that compound Ba4B 14 O 25The crystal has a wide transmission range, with high transmittance in the 200-2000nm spectral range, a reflectance of 71.5% at 200nm, and an ultraviolet absorption cutoff wavelength of <200nm.

[0062] Thermogravimetric analysis of sample in Test Example 2

[0063] Sample 1 obtained in Example 1 # As a representative, Ba4B 14 O 25 Thermogravimetric analysis was performed on a NETZSCH STA449F3 thermogravimetric analyzer from Germany. The results are as follows: Figure 3 As shown in the figure. It can be seen from the figure that Ba4B 14 O 25 The crystal can be stabilized up to 900℃ without losing weight throughout the process.

[0064] Test Example 3: Harmonization Test Experiment and Results

[0065] Sample 1 obtained in Example 1 # As a representative example, barium borate crystals of different sizes (Ba4B) were analyzed. 14 O 25 Perform frequency multiplication tests.

[0066] The specific steps are as follows: A 1064nm wavelength laser generated by a Q-tunable Nd:YAG solid-state laser is used as the fundamental frequency light to irradiate the test crystal powder. The generated second harmonic is detected using a photomultiplier tube, and the harmonic intensity is displayed on an oscilloscope. Each test crystal is ground and sieved into several different particle size ranges (25-45, 45-53, 53-75, 75-105, 105-150, 150-210, 210-300μm) using a standard sieve. The frequency doubling effect at different particle sizes is tested to determine whether the test crystal can achieve phase matching. Based on the second harmonic output intensity of the test crystal and KH2PO4 (KDP) in the same particle size range of 210-300μm, the SHG effect ratio of the test crystal and KDP is calculated. In addition, since the SHG response of β-BaB2O4 (BBO) is generally reported to be 5-6 times that of KDP, we also selected BBO samples with a particle size of 210-300 μm as standard samples for measurement to ensure accurate measurement of the ratio of SHG effect between the test crystal and KDP.

[0067] The results are attached. Figure 4 As shown, the test results indicate that compound Ba4B 14 O 25 Under 1064nm laser irradiation, its powder SHG coefficient is 2.4 times that of KH2PO4 (KDP), and phase matching can be achieved.

[0068] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a barium borate nonlinear crystal material, characterized in that, When the barium borate nonlinear crystal material is polycrystalline, the following steps are included: S11. Grind the raw materials containing barium compounds and boron compounds, and heat them to 290~310℃ for 43~52 hours. S12. Grind the intermediate product from step S11 and heat it to 390~410℃ for 11~13 hours. S13. Grind the intermediate product from step S12 and heat it to 590~610℃ for 11~13 hours. S14. Grind the intermediate product from step S13 and heat it to 730~750℃ for 22~26h to obtain barium borate nonlinear crystal material. In steps S11 to S14, the grinding speed is 380~420 rpm, and the grinding time is 0.8~1.2 h. The chemical formula of the barium borate nonlinear crystal material is Ba4B. 14 O 25 .

2. A method for preparing a barium borate nonlinear crystal material, characterized in that, When the barium borate nonlinear crystal material is a single crystal, the following steps are included: S21. Grind the raw materials containing barium compounds, boron compounds, lead compounds, and antimony compounds, and heat them to 400~500℃ for 35~60 hours. S22. Grind the intermediate product from step S21, heat it to 800~900℃ and react it for 12~40h, then slowly cool it down to obtain barium borate nonlinear crystal material. In steps S21 and S22, the heating rate is 0.5~10℃ / min; The slow cooling process includes: cooling to 680-780℃ at a cooling rate of 0.5-3℃ / h, and then cooling to 300-400℃ at a cooling rate of 4-15℃ / h. The lead-containing compound is selected from at least one of lead oxide, lead carbonate, lead fluoride, and lead nitrate; the antimony-containing compound is selected from at least one of antimony trioxide, antimony pentoxide, and antimony trifluoride. The chemical formula of the barium borate nonlinear crystal material is Ba4B. 14 O 25 .

3. The preparation method according to claim 1, characterized in that, The molar ratio of barium to boron in the barium-containing compound and the boron-containing compound, calculated as elements, is 1:3.3~3.

7.

4. The preparation method according to claim 2, characterized in that, The molar ratio of barium, boron, lead, and antimony in the barium-containing compound, boron-containing compound, lead-containing compound, and antimony-containing compound, calculated by element, is 1:(2~4):(0.2~0.5):(0.25~0.45).

5. The preparation method according to claim 1 or 2, characterized in that, The boron-containing compound is selected from at least one of boron oxide and boric acid; The barium-containing compound is selected from at least one of barium carbonate, barium oxide, barium nitrate, barium fluoride, and barium hydroxide.

6. The preparation method according to claim 2, characterized in that, The slow cooling process includes: cooling to 730-750℃ at a cooling rate of 0.8-1.2℃ / h, and then cooling to 340-360℃ at a cooling rate of 7-9℃ / h.

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