A sodium zinc borate ultraviolet birefringence optical crystal, a preparation method and use thereof

Abstract

This invention relates to a novel birefringent crystal, its preparation and application, and belongs to the field of optical technology. The chemical formula of the birefringent crystal is Na₂ZnB₆O. 11 Na₂ZnB₆O₆ belongs to the monoclinic crystal system, space group C2 / c. This crystal can be prepared in an open system using high-temperature solid-state and high-temperature solution methods. It exhibits excellent birefringence, with a birefringence of 0.094 at 1064 nm and a transmittance of 53% at the ultraviolet cutoff edge of 190 nm. The Na₂ZnB₆O₆ prepared by the method described in this invention... 11 Birefringent crystals can be used to make polarization elements such as optical isolators, circulators, Glan prisms, and optical polarizers, and have important applications in the fields of optics and information communication.

Description

Technical Field

[0001] This invention relates to a method for preparing a sodium zinc borate birefringent optical crystal and a photoelectric modulation device fabricated using the crystal, the chemical formula of which is Na₂ZnB₆O. 11 . Background Technology

[0002] The interaction between light and matter is central to versatile technologies and has significant applications in optoelectronics. Birefringence, as a manifestation of spatially asymmetric light-matter interaction, plays a crucial role in manipulating light polarization. Birefringent crystals, due to their inherent ability to modulate light polarization, have attracted considerable attention in laser phase matching, optical communication, and optical interference filters. With the increasing demand for deep ultraviolet (DUV) light sources, the fabrication of DUV polarized light using birefringent materials has become a research hotspot. After years of exploration by materials scientists, a series of representative novel birefringent materials have been developed, such as borate crystal Ca(BO2)2, tin fluoride crystal α-SnF2, and molybdate crystal α-BaTeMo2O9. However, significant challenges remain in designing DUV birefringent crystals with wide bandgap and high birefringence, as these two properties are typically inversely proportional. For example, MgF2 is a widely used short-wavelength birefringent crystal with excellent DUV transparency, but its birefringence at 532 nm is only 0.012, limiting its application range. To date, there are very few crystals that can simultaneously satisfy short-wave ultraviolet transmittance and high birefringence. Therefore, exploring high-performance DUV birefringent materials is an important research topic.

[0003] This patent application aims to propose a novel d-containing 10 Transition metal ion borate nonlinear optical crystal material - Na2ZnB6O 11 Its preparation method and applications are also described. This material exhibits good birefringence properties, which will provide a wider range of material choices and technical support for the advancement of optical technology. Summary of the Invention

[0004] The first objective of this invention is to provide a sodium zinc borate birefringent optical crystal with the chemical formula Na₂ZnB₆O. 11 ;

[0005] The second objective of this invention is to provide a method for preparing high-purity Na₂ZnB₆O using a traditional high-temperature solid-state method. 11 Compound powder, and Na2ZnB6O grown using a high-temperature solution method. 11 Preparation method of compound optical crystals.

[0006] The third objective of this invention is to provide applications for sodium zinc borate birefringent optical devices.

[0007] The technical solution to achieve the above objectives is as follows:

[0008] The compound sodium zinc borate provided by this invention has the chemical formula Na₂ZnB₆O. 11 The preparation method of the sodium zinc borate birefringent optical material is as follows: sodium-containing compound, zinc-containing compound and boron-containing compound raw materials are uniformly mixed and thoroughly ground according to a certain stoichiometric ratio, placed in a muffle furnace, pre-calcined at low temperature to remove moisture and gas from the raw materials, and then calcined at high temperature for several days. During the process, the raw materials are taken out and ground multiple times to finally obtain the polycrystalline pure phase of sodium zinc borate.

[0009] The sodium-containing compound includes at least one of sodium oxide, sodium hydroxide, or a sodium salt; the sodium salt includes at least one of sodium chloride, sodium bromide, sodium fluoride, sodium nitrate, sodium, sodium bicarbonate, sodium acetate, and sodium sulfate.

[0010] The zinc-containing compound is at least one of zinc oxide or a zinc salt; the zinc salt includes at least one of zinc chloride, zinc fluoride, zinc nitrate, zinc oxalate, zinc carbonate, and zinc sulfate.

[0011] The boron-containing compound is at least one of boron oxide, boric acid, or borates; borates include at least one of potassium borate, rubidium borate, barium borate, strontium borate, and scandium borate.

[0012] The sodium zinc borate compound can be prepared by a high-temperature solid-state reaction method according to the following chemical reaction formula:

[0013] 1)Na2CO3+ZnO+6H3BO3→Na2ZnB6O 11 +CO2↑+9H2O

[0014] 2)2NaHCO3+ZnO+6H3BO3→Na2ZnB6O 11 +2CO2↑+10H2O

[0015] 3)2NaNO3+ZnO+6H3BO3→Na2ZnB6O 11 +2NO₂↑+5O₂↑

[0016] 4) 2NaOH + ZnO + 6H3BO3 → Na2ZnB6O 11 +10H2O↑

[0017] 5)Na2SO4+ZnO+6H3BO3→Na2ZnB6O 11 +SO3↑+9H2O

[0018] 6) Na₂O + ZnO + 6H₃BO₃ → Na₂ZnB₆O 11 +9H2O

[0019] 7) 2NaF + ZnO + 6H3BO3 + 0.5O2 → Na2ZnB6O 11 +F2↑+9H2O

[0020] 8)2NaCl+ZnO+6H3BO3+0.5O2→Na2ZnB6O 11 +Cl2↑+9H2O

[0021] 9)6NaB r +ZnO+6H3BO3+0.5O2→Na2ZnB6O 11 +Br2↑+9H2O

[0022] 10)Na2(C2O4)+ZnO+6H3BO3+0.5O2→Na2ZnB6O 11 +9H2O+2CO2↑

[0023] 11) Na2O + ZnCO3 + 6H3BO3 → Na2ZnB6O 11 +9H2O+CO2↑

[0024] 12) Na2CO3 + ZnCO3 + 6H3BO3 → Na2ZnB6O |1 +2CO2↑+9H2O

[0025] 13)Na2O + Zn(NO3)2 + 6H3BO3 → Na2ZnB6O 11 +2NO2↑+5O2↑

[0026] 14) 2NaNO3 + Zn(NO3)2 + 6H3BO3 → Na2ZnB6O 11 +4NO2↑+5.5O2↑

[0027] 15)2NaOH + Zn(NO3)2 + 6H3BO3 → Na2ZnB6O 11 +2NO2↑+10H2O↑+0.5O2↑

[0028] 16)2NaHCO3+Zn(NO3)2+3B2O3→Na2ZnB6O 11 +H2O +2CO2↑ +NO2↑ +1.5O2↑

[0029] 17) Na2CO3 + ZnCl2 + 0.5O2 + 3B2O3 → Na2ZnB6O 11 +CO2↑+Cl2↑

[0030] 18)Na2CO3+ZnF2+3B2O3+0.5O2→Na2ZnR6O 11 +CO2↑+F2↑

[0031] This invention provides a sodium zinc borate birefringent optical crystal, which is synthesized by a high-temperature solid-state synthesis method, and its chemical formula is Na₂ZnB₆O. 11 Its molecular weight is 352.22, it has a centrosymmetric structure, belongs to the monoclinic crystal system, has a space group of C2 / c, and its unit cell parameters are... α = γ = 90°, β = 112.0370(10)°. It possesses a large experimental optical band gap of 6.04 eV and achieves the largest birefringence among borate-based NLO materials containing [B3O7] moieties, at 0.094 at 1064 nm. Importantly, the compound exhibits a UV cutoff edge in the deep UV region below 190 nm, with a transmittance of 53% at 190 nm.

[0032] This invention provides a method for preparing sodium zinc borate birefringent optical crystals. The method employs the molten salt method to grow the sodium zinc borate birefringent optical crystals, and the specific growth scheme is as follows:

[0033] a. Mix the sodium zinc borate single-phase polycrystalline powder with the flux evenly, heat the temperature to 500-900℃ at a heating rate of 3-100℃ / h, hold the temperature for no less than 24h, and then cool the mixed solution to 400-700℃. The molar ratio of the sodium zinc borate single-phase polycrystalline powder to the flux is 1:0-15.

[0034] Alternatively, a mixture of sodium-containing compounds, zinc-containing compounds, and boron-containing compounds, or a mixture of sodium-containing compounds, zinc-containing compounds, and boron-containing compounds with a flux, can be heated to 600-1200℃ at a heating rate of 3-100℃ / h, held at that temperature for at least 24h, and then cooled to 500-900℃. The molar ratio of sodium-containing compounds, zinc-containing compounds, and boron-containing compounds to flux is 2:1:6:0-15.

[0035] The flux mainly includes Na2O, NaOH, H3BO3, sodium salts, boron salts, PbO, Bi2O3, and composite fluxes, such as one or more of Na2O-H3BO3, NaF-H3BO3, NaF-PbO, Na2O-PbO, Na2O-Bi2O3, H3BO3-PbO, or Bi2O3-PbO-NaF.

[0036] The sodium zinc borate single-phase polycrystalline powder is prepared by a high-temperature solid-state synthesis method, including the following steps: mixing sodium-containing compounds, zinc-containing compounds, and boron-containing compounds, and preparing sodium zinc borate by a high-temperature solid-state reaction method. The molar ratio of sodium in the sodium-containing compound, zinc in the zinc-containing compound, and boron in the boron-containing compound is 2:1:6. The sodium-containing compound, zinc-containing compound, and boron-containing compound raw materials are thoroughly ground, mixed evenly, and placed in a Pt crucible or Al2O3 crucible and placed in a muffle furnace. The raw materials are first pre-calcined to remove moisture and gas, and then heated to 500-900℃ for continuous sintering for no less than 72 hours. During the calcination, the raw materials are removed and ground multiple times. Finally, the temperature is lowered to room temperature to obtain the sodium zinc borate single-phase polycrystalline powder.

[0037] b. Preparation of sodium zinc borate seed crystals: The mixed solution obtained in step a is slowly cooled to room temperature at a cooling rate of 0.1-20℃ / h to obtain sodium zinc borate seed crystals by spontaneous crystallization;

[0038] c. Place the Pt crucible containing the mixed solution obtained in step a into the crystal growth furnace, fix the seed crystal obtained in step b on the seed crystal rod, place the seed crystal above the liquid surface through the platinum wire, preheat the seed crystal for 10-40 min, and when it is 3-16℃ above the saturation point, lower the seed crystal below the liquid surface, keep it at a constant temperature for 5-20 min to remove impurities on the surface of the seed crystal, and then cool it down to the saturation point temperature at a cooling rate of 1-10℃ / min.

[0039] d. Then, slowly cool down Zn at a rate of 1-5℃ / day, and grow the crystal by rotating the seed crystal rod at 3-60 rpm. After the crystal grows to the required size, lift the crystal to 1-2 cm above the liquid surface, and then cool it down to room temperature at a rate of 10-50℃ / h. Finally, open the furnace and take out the crystal to obtain sodium zinc borate birefringent optical crystal.

[0040] The fluxing agents are as follows: Na2O-H3BO3 system: Na2O to H3BO3 molar ratio is 1-10:1-15; NaF-H3BO3 system: NaF to H3BO3 molar ratio is 1-15:1-18; NaF-PbO system: NaF to PbO molar ratio is 1-10:1-20; Na2O-PbO system: Na2O to PbO molar ratio is 5-20:1-20; Na2O-Bi2O3 system: Na2O to Bi2O3 molar ratio is 5-20:1-20; H3BO3-PbO system: H3BO3 to PbO molar ratio is 1-5:5-20; Bi2O3-PbO-NaF system: Bi2O3 to PbO to NaF molar ratio is 1-5:1-6:2-10.

[0041] This invention provides a sodium zinc borate birefringent optical crystal, which is synthesized by a high-temperature solid-state synthesis method, and its chemical formula is Na₂ZnR₆O.11 Its molecular weight is 352.22, it has a centrosymmetric structure, belongs to the monoclinic crystal system, has a space group of C2 / c, and its unit cell parameters are... α = γ = 90°, β = 112.0370(10)°. It possesses a large experimental optical band gap of 6.04 eV and achieves the largest birefringence among borate-based NLO materials containing [B3O7] moieties, at 0.094 at 1064 nm. Importantly, the compound exhibits a UV cutoff edge in the deep UV region below 190 nm, with a transmittance of 53% at 190 nm.

[0042] Because Na2O, NaOH, H3BO3, sodium salts, zinc salts, PbO, Bi2O3, or composite fluxes are used in the growth of second-order nonlinear optical crystals of sodium zinc borate, among which the composite fluxes include one or more of Na2O-H3BO3, NaF-H3BO3, NaF-PbO, Na2O-PbO, Na2O-Bi2O3, H3BO3-PbO, or Bi2O3-PbO-NaF, it is easy to grow larger target crystals; the obtained crystals have advantages such as a wide atmospheric transmission window, excellent thermal stability, and a high laser damage threshold.

[0043] The sodium zinc borate birefringent optical crystal obtained by the method described in this invention can be used to fabricate optoelectronic modulation devices. At room temperature, the optical modulator utilizes the birefringence of the crystal to modulate the polarization state of light. In a photoelastic modulator (PEM), the piezoelectric actuator vibrates along its length, and after entering the birefringent crystal, a stress standing wave is formed, causing the refractive index of the transmitting crystal to change accordingly, thereby achieving the purpose of modulating the polarization state of the incident light. Attached Figure Description

[0044] Figure 1 The present invention is Na2ZnB6O 11 X-ray diffraction pattern of powder and theoretical X-ray pattern based on crystal structure simulation.

[0045] Figure 2 The present invention is Na2ZnB6O 11 Unit cell structure diagram.

[0046] Figure 3 The present invention is Na2ZnB6O 1t UV-Vis diffuse reflectance spectrum and experimental band gap diagram.

[0047] Figure 4 The present invention is Na2ZnB6O 11 A schematic diagram illustrating the working principle of a nonlinear optical device fabricated from a crystal, where 1 represents the incident light wave, 2 is the polarizer, 3 is the polarized light, and 4 is Na₂ZnB₆O. 11 Crystal. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0049] Example 1:

[0050] According to the reaction formula: Na₂CO₃ + ZnO + 6H₃BO₃ → Na₂ZnB₆O 11 +CO2↑+9H2O synthesizes compound Na2ZnB6O 11 ;

[0051] Na₂CO₃, ZnO, and H₃BO₃ were weighed in a molar ratio of 1:1:6 and placed in a mortar, mixed, and ground. The mixture was then placed in a φ60mm×60mm open alumina crucible and placed in a muffle furnace. The temperature was slowly raised to 300℃ and calcined for 12 hours to remove moisture and gases. Afterward, the temperature was raised to 650℃ and calcined for 24 hours. The mixture was then removed, ground, and placed back in the muffle furnace for further calcination at 840℃ for at least 48 hours to prepare a single-phase polycrystalline powder of sodium zinc borate. Powder X-ray diffraction analysis showed that the obtained sample powder X-ray diffraction pattern was consistent with that of sodium zinc borate (Na₂ZnB₆O₃). 11 The X-ray theoretical spectra obtained from the single-crystal structure are in good agreement; see appendix. Figure 1 ;

[0052] The prepared compound sodium zinc borate Na2ZnB6O 11 Single-phase polycrystalline powder was mixed with flux Na₂O-H₃BO₃ at a molar ratio of 1:2, with the molar ratio of Na₂O to H₃BO₃ being 10:1. The mixture was placed in a φ60mm×60mm platinum crucible and heated to 900℃, held at that temperature for at least 24 hours to ensure homogeneous mixing. Simultaneously, a Pt wire was added, followed by cooling to induce spontaneous crystallization. The resulting crystal has the chemical formula Na₂ZnB₆O. 11 Its molecular weight is 352.22, it has a centrosymmetric structure, belongs to the monoclinic crystal system, has a space group of C2 / c, and its unit cell parameters are... α = γ = 90°, β = 112.0370(10)°. It possesses a large experimental optical band gap of 6.04 eV, and the ultraviolet cutoff edge of this compound is 190 nm. See Appendix. Figure 2 and attached Figure 3 .

[0053] The solution was slowly cooled at a cooling rate of 1-5℃ / h to obtain sodium zinc borate seed crystals.

[0054] Crystal growth in compound solution: Na₂ZnB₆O obtained by spontaneous crystallization 11Small crystals are used as seed crystals. Platinum wires are used to fix the seed crystals to the seed crystal rod. First, the seed crystals are placed 1-3 cm above the liquid surface for preheating treatment. Then, the seed crystals are immersed below the liquid surface at a temperature 3-15℃ higher than the saturation point temperature and kept for 5-20 minutes to remove surface impurities. After that, the temperature is quickly cooled to the saturation point temperature.

[0055] Then, cool the crystal at a rate of 1-5℃ / day, with the seed crystal rod rotating at 5-60 rpm. After growth, lift the crystal 1-2 cm above the liquid surface and cool it to room temperature at a rate of 10-50℃ / h. Then remove the crystal to obtain Na2ZnB6O. 11 Crystal.

[0056] The raw material sodium carbonate in the reaction formula can be replaced by other sodium-containing salts such as sodium oxide, sodium chloride, sodium bromide, sodium nitrate, sodium acetate, sodium hydroxide, sodium bicarbonate, or sodium sulfate. Zinc oxide can be replaced by other zinc-containing salts such as zinc chloride, zinc fluoride, zinc nitrate, zinc oxalate, zinc carbonate, or zinc sulfate. Boron oxide can be replaced by other boron salts.

[0057] Example 2:

[0058] According to the reaction formula: 2NaNO3 + ZnO + 6H3BO3 → Na2ZnB6O 11 +2NO₂↑+5O₂↑ synthesizes compound Na₂ZnB₆O 11

[0059] Weigh out the raw materials directly using NaNO3, ZnO, and H3BO3 in a molar ratio of 2:1:6, and mix them with the flux NaF-H3BO3 in a molar ratio of Na2ZnB6O. 11 The ratio of NaF to H3BO3 is 1:3, where the molar ratio of NaF to H3BO3 is 8:1. The mixture is thoroughly mixed, pressed, and placed into a φ60mm×60mm Pt crucible. The mixture is heated to 950℃ at a heating rate of 10-80℃ / h and held at that temperature for at least 24h to ensure uniform mixing of the solution. At the same time, a Pt wire is lowered into the liquid surface, and then the temperature is lowered to induce spontaneous crystallization.

[0060] Sodium zinc borate seed crystals were obtained by slow cooling at a rate of 1-5℃ / h.

[0061] Crystal growth in compound solution: Na₂ZnB₆O obtained by spontaneous crystallization 11 Small crystals are used as seed crystals. Platinum wires are used to fix the seed crystals to the seed crystal rod. First, the seed crystals are placed 1-2 cm above the liquid surface for preheating treatment. Then, the seed crystals are immersed below the liquid surface at a temperature 3-15℃ higher than the saturation point and kept for 5-30 minutes to remove surface impurities. After that, the temperature is quickly cooled to the saturation point temperature.

[0062] The temperature is then lowered at a rate of 1-5℃ / day, with the seed crystal rod rotating at 5-60 rpm. After crystal growth is complete, the crystal is removed from the liquid surface and cooled to room temperature at a rate of 10-50℃ / h. The crystal is then removed from the furnace to obtain Na2ZnB6O. 11 Crystal.

[0063] The raw material sodium nitrate in the reaction formula can be replaced by other sodium-containing salts such as sodium oxide, sodium chloride, sodium bromide, sodium acetate, sodium hydroxide, sodium bicarbonate, or sodium sulfate. Zinc oxide can be replaced by other zinc-containing salts such as zinc chloride, zinc fluoride, zinc nitrate, zinc oxalate, zinc carbonate, or zinc sulfate. Boron oxide can be replaced by other boron salts.

[0064] Example 3:

[0065] According to the reaction formula: 2NaOH + ZnO + 6H3BO3 → Na2ZnB6O 11 +10H₂O↑ synthesizes compound Na₂ZnB₆O 11 ;

[0066] NaOH, ZnO, and H3BO3 were weighed directly in a molar ratio of 2:1:6. The weighed raw materials were mixed with the flux NaF-PbO in a molar ratio of 1:1, wherein the molar ratio of NaF to PbO was 3:1. The mixture was placed in a φ60mm×60mm platinum crucible, heated to 940℃, and held at that temperature for no less than 24 hours to ensure that the solution was homogeneous. At the same time, Pt wire was added, and then the temperature was lowered to induce spontaneous crystallization.

[0067] The solution was slowly cooled at a cooling rate of 1-5℃ / h to obtain sodium zinc borate seed crystals.

[0068] Crystal growth in compound solution: Na₂ZnB₆O obtained by spontaneous crystallization 11 Small crystals are used as seed crystals. Platinum wires are used to fix the seed crystals to the seed crystal rod. First, the seed crystals are placed 1-2 cm above the liquid surface for preheating treatment. Then, the seed crystals are immersed below the liquid surface at a temperature 3-15℃ above the saturation point and kept for 5-20 minutes to remove surface impurities. After that, the temperature is quickly cooled to the saturation point temperature.

[0069] The crystal is slowly cooled at a rate of 1-3℃ / day, with the seed crystal rod rotating at 5-60 rpm. After crystal growth is complete, the crystal is removed from the liquid surface and cooled to room temperature at a rate of 10-50℃ / h. The crystal is then removed from the furnace to obtain Na2ZnB6O. 11 Crystal.

[0070] In the reaction formula, sodium hydroxide can be replaced by other sodium-containing salts such as sodium oxide, sodium chloride, sodium bromide, sodium acetate, sodium bicarbonate, or sodium sulfate; zinc oxide can be replaced by other zinc-containing salts such as zinc chloride, zinc fluoride, zinc nitrate, zinc oxalate, zinc carbonate, or zinc sulfate; and boron oxide can be replaced by other boron salts.

[0071] Example 4:

[0072] According to the reaction formula: Na₂SO₄ + ZnO + 6H₃BO₃ → Na₂ZnB₆O 11 +SO3↑+9H2O synthesize compound Na2ZnB6O 11 ;

[0073] Na2SO4, ZnO, and H3BO3 were weighed directly in a molar ratio of 1:1:6. The weighed raw materials were mixed with the flux Na2O-PbO in a molar ratio of 2:3, wherein the molar ratio of Na2O to PbO was 3:5. The mixture was placed in a φ60mm×60mm platinum crucible, heated to 880℃, and held at that temperature for no less than 24 hours to ensure that the solution was homogeneous. At the same time, Pt wire was added, and then the temperature was lowered to induce spontaneous crystallization.

[0074] The solution was slowly cooled at a cooling rate of 1-5℃ / h to obtain sodium zinc borate seed crystals.

[0075] Crystal growth in compound solution: Na₂ZnB₆O obtained by spontaneous crystallization 11 Small crystals are used as seed crystals. Platinum wires are used to fix the seed crystals to the seed crystal rod. First, the seed crystals are placed 1-2 cm above the liquid surface for preheating. Then, the seed crystals are immersed below the liquid surface at a temperature 3-15℃ above the saturation point and kept for 5-20 minutes to remove surface impurities. After that, the temperature is quickly cooled to the saturation temperature.

[0076] The temperature is slowly reduced at a rate of 1-3℃ / day, with the seed crystal rod rotating at 5-60 rpm. After crystal growth is complete, the crystal is removed from the liquid surface and cooled to room temperature at a rate of 10-50℃ / h. Then, the crystal is removed from the furnace to obtain Na2ZnB6O. 11 Crystal.

[0077] In the reaction formula, sodium sulfate can be replaced by other sodium-containing salts such as sodium oxide, sodium bromide, sodium fluoride, sodium nitrate, sodium carbonate, sodium bicarbonate, or sodium acetate. Zinc oxide can be replaced by other zinc-containing salts such as zinc chloride, zinc fluoride, zinc nitrate, zinc oxalate, zinc carbonate, or zinc sulfate. Boron oxide can be replaced by other boron salts.

[0078] Example 5:

[0079] According to the reaction formula: 2NaCl + ZnO + 6H3BO3 + 0.5O2 → Na2ZnB6O 11+Cl₂↑+9H₂O synthesizes compound Na₂ZnB₆O 11 ;

[0080] Weigh out the raw materials NaCl, ZnO, and H3BO3 directly in a molar ratio of 2:1:6. Mix the weighed raw materials with the flux Na2O-Bi2O3 in a molar ratio of 1:4, where the molar ratio of Na2O to Bi2O3 is 1:2. Place the mixture into a φ60mm×60mm platinum crucible, heat it to 850℃, and hold it at that temperature for at least 24 hours to ensure that the solution is homogeneous. At the same time, add a Pt wire, and then cool it down to induce spontaneous crystallization.

[0081] The solution was slowly cooled at a cooling rate of 1-5℃ / h to obtain sodium zinc borate seed crystals.

[0082] Crystal growth in compound solution: Na₂ZnB₆O obtained by spontaneous crystallization 11 Small crystals are used as seed crystals. Platinum wires are used to fix the seed crystals to the seed crystal rod. First, the seed crystals are placed 1-2 cm above the liquid surface for preheating treatment. Then, the seed crystals are immersed below the liquid surface at a temperature 3-15℃ above the saturation point and kept for 5-20 minutes to remove surface impurities. After that, the temperature is quickly cooled to the saturation point temperature.

[0083] The crystal is slowly cooled at a rate of 1-3℃ / day, with the seed crystal rod rotating at 5-60 rpm. After crystal growth is complete, the crystal is removed from the liquid surface and cooled to room temperature at a rate of 10-50℃ / h. Then, the crystal is removed from the growth furnace to obtain Na2ZnR6O. 11 Crystal.

[0084] In the reaction formula, sodium chloride can be replaced by other sodium-containing salts such as sodium bromide, sodium fluoride, sodium nitrate, sodium carbonate, sodium bicarbonate, sodium acetate, or sodium sulfate. Zinc oxide can be replaced by other zinc-containing salts such as zinc chloride, zinc fluoride, zinc nitrate, zinc oxalate, zinc carbonate, or zinc sulfate. Boron oxide can be replaced by other boron salts.

[0085] Example 6

[0086] Na2ZnB6O 11 Crystal fabrication of optical modulation devices:

[0087] The Na2ZnB6O obtained in Examples 1-7 11 A birefringent crystal determines the optical axis of the crystal, and is oriented and processed according to the required size, angle and thickness. The light-transmitting surface is polished, and it can then be used as an optical modulation device.

[0088] According to the appendix Figure 4As shown, the obtained crystal is fixed at position 4. At room temperature, the incident light 1 first passes through a polarizer 2, which only allows light 3 with a specific polarization direction to pass through. Next is the birefringent crystal 4, which is placed between two parallel plate capacitors. When the light passes through the crystal, due to the electro-optic effect, the phase of the light changes according to the intensity of the electric field, and finally the modulated light wave is output.

[0089] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A crystalline material exhibiting birefringence optical effect, having the chemical formula Na₂ZnB₆O. 11 Its characteristics This crystalline material belongs to the monoclinic crystal system, space group C2 / c (No. 15). The crystal's unit cell parameters have been precisely measured. α=γ=90°, β=112.0370(10)°. And the Z value of the crystal is 1. Preferably, the crystal has an X-ray crystal diffraction pattern substantially as shown in FIG1.

2. The Na2ZnB6O according to claim 1 11 Crystal, characterized in that, The crystal has the structural features shown in Figure 2. Preferably, the crystal has a UV-Vis diffuse reflectance spectrum and experimental band gap diagram that are substantially as shown in Figure 3. Preferably, the Na2ZnB6O 11 The ultraviolet absorption cutoff edge of the crystal is shorter than 190 nm. Preferably, the Na2ZnB6O 11 The experimental band gap of the crystal is 6.04 eV. Preferably, the Na2ZnB6O 11 The birefringence of the crystal is 0.094 at 1064 nm.

3. The Na2ZnB6O as described in claim 1 or 2 11 A method for preparing crystals, characterized in that, The method includes Na2ZnB6O 11 Na₂ZnB₆O was obtained by growing pure-phase polycrystalline powder and flux using the molten salt method. 11 Crystal.

4. The Na2ZnB6O according to claim 3 11 A method for preparing crystals, characterized in that, The method includes the following steps: (1) Preparation of Na2ZnB6O 11 Pure-phase polycrystalline powder; (2) Na2ZnB6O 11 Pure-phase polycrystalline powder and flux are mixed and then heated, melted, held, and cooled in a molten salt furnace to obtain Na₂ZnB₆O. 11 Crystal.

5. The Na2ZnB6O according to claim 3 or 4 11 A method for preparing pure-phase polycrystalline powder, characterized in that, The Na2ZnB6O 11 Pure phase polycrystalline powder is made from sodium- and zinc-containing compounds, B2O3 and / or H3BO3 as raw materials, through weighing, mixing, grinding and furnace firing. Preferably, the potassium-containing compound is at least one selected from NaCl, Na2O, Na2CO3, NaOH, NaH2PO4, NaNO3, and Na2SO4; Preferably, the zinc-containing compound is at least one of zinc oxide or a zinc salt; the zinc salt includes at least one of zinc chloride, zinc fluoride, zinc nitrate, zinc oxalate, zinc carbonate, and zinc sulfate. Preferably, the amount of the raw material used is in accordance with Na2ZnB6O 11 Stoichiometric distribution; Preferably, the Na2CO3 and ZnO can be in excess by 0.5 to 3 wt%, for example, in excess of 1.0 wt%, 1.5 wt%, 2.0 wt%, or 2.5 wt%.

6. The Na2ZnB6O according to claim 5 11 A method for preparing pure-phase polycrystalline powder, characterized in that, The firing temperature can be above 700℃, for example 700~800℃, such as 800~850℃; the firing time can be 1~3h, for example 1.5~2.5h, such as 2h.

7. The Na₂ZnB₆O according to any one of claims 3 to 6 11 A method for preparing crystals, characterized in that, The molar ratio of the pure phase polycrystalline powder to the flux can be 1:(1-20).

8. The Na2ZnB6O according to any one of claims 3 to 7 11 A method for preparing crystals, characterized in that, The flux is a mixture of Na2CO3 and B2O3 and / or H3BO3, wherein the molar ratio of Na2CO3 to B2O3 and / or H3BO3 can be (1-8):1, such as (1-6):1, such as (1-5):

1.

9. The Na₂ZnB₆O according to any one of claims 4 to 8 11 A method for preparing crystals, characterized in that, The heating refers to raising the temperature to 800-1000℃, for example, 800-900℃, such as 900-1000℃; The insulation time is 0.5 to 4 days, such as 1 to 3 days; The cooling refers to reducing the temperature to 10-50°C, such as 20-25°C; The rates of heating and cooling can be the same or different, and can be independently selected from 5 to 100°C / h, for example 30 to 60°C / h, such as 40 to 50°C / h.

10. The Na₂ZnB₆O as described in claim 1 or 2 11 A crystal, which has applications in optical modulation devices. The Na₂ZnB₆O 11 Birefringent crystals exhibit excellent birefringence properties, including but not limited to photoelectric modulators made from them. By utilizing the electro-optic effect, they can precisely control the intensity and changes of an applied electric field, thereby achieving precise modulation of parameters such as the amplitude and phase of light waves. This modulation method has important applications in optical communication, optical sensing, and optical computing. These properties of birefringent optical crystals can be used to fabricate birefringent optical devices.

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