A barium borate crystal, its preparation method and application

Abstract

This invention discloses a barium borate crystal, its preparation method, and its applications. The barium borate crystal has the chemical formula Ba₂BeB₂O₆, a non-centrosymmetric structure, belongs to the orthorhombic crystal system, has the space group Pca₂₁, and its cell parameters are α = 90°, β = 90°, and γ = 90°. This barium borate crystal exhibits extremely low birefringence from the ultraviolet to the infrared band, and its extremely low birefringence supports its application on zero-order glass slides.

Description

Technical Field

[0001] This invention relates to the field of crystal preparation technology. More specifically, it relates to a barium borate crystal, its preparation method, and its applications. Background Technology

[0002] Waveplates, as commonly used phase retarders, can be used to change the vibration direction of linearly polarized light and to convert between linearly polarized and elliptically polarized light. Generally, crystal waveplates can be divided into zero-order waveplates (including true zero-order and composite zero-order waveplates) and multi-order waveplates. The difference lies in the optical path difference (OPD) introduced: multi-order waveplates introduce an OPD > λ, where λ is the incident wavelength, while zero-order waveplates introduce an OPD < λ. Taking a true zero-order waveplate as an example, since a smaller OPD (OPD < λ) is required, under perpendicular incidence, OPD can be simply calculated as OPD = d·Δn, where d is the plate thickness and Δn is the birefringence of the plate in the incident direction. With a fixed OPD, the smaller the birefringence, the larger the required plate thickness. For true zero-order waveplates, quartz crystals or magnesium fluoride crystals with low birefringence are generally used, and their thickness is limited to 0.01-0.1 mm. Currently, the most commonly used commercial zero-order glass slide material is quartz crystal (Δn ~ 0.009@visible spectrum). Zero-order glass slides made from quartz crystal are only 15 μm thick, making them extremely difficult to manufacture and resulting in poor mechanical strength. Calculations show that for a 532nm zero-order waveplate made from quartz crystal, a thickness error of 0.5 μm can produce a phase retardation deviation of 3.0°, which can significantly impact precision optical applications.

[0003] With the development of science and technology, people have higher and higher requirements for zero-order glass slides. Therefore, it is of great significance to find materials with lower birefringence that can be used to manufacture thicker zero-order glass slides. Summary of the Invention

[0004] Based on the above facts, the purpose of this invention is to provide a barium boroberylate crystal, its preparation method, and its applications. This barium boroberylate crystal exhibits extremely low birefringence from the ultraviolet to the infrared band, and its extremely low birefringence supports its application on zero-order glass slides.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] On one hand, this invention provides a barium borate crystal with the chemical formula Ba₂BeB₂O₆, exhibiting a non-centrosymmetric structure, belonging to the orthorhombic crystal system, space group Pca₂₁, and cell parameters of [missing information]. α=90°, β=90°, γ=90°.

[0007] In another aspect, the present invention provides a method for preparing barium borate crystals, which uses a melt method to prepare the barium borate crystals, specifically including the following steps:

[0008] The Ba2BeB2O6 compound or a mixture of BaCO3, BeO, and H3BO3 is mixed with an optional flux, heated to a melting point to obtain a high-temperature melt, held at that temperature, and then cooled to room temperature to obtain the barium borate crystals.

[0009] Furthermore, in the technical solution of this invention, "optionally present" means that it can be added or not. That is, flux can be added or not.

[0010] Furthermore, the heating rate is 1-35℃ / h, the temperature after heating is 1100-1200℃, and the holding time is 12-72h, preferably 12-36h.

[0011] Furthermore, the cooling method is as follows: the temperature is reduced to 1050-1100℃ at a cooling rate of 0.5-10℃ / h, then reduced to 950-1000℃ at a cooling rate of 0.1-1℃ / h, and then naturally cooled to room temperature.

[0012] Furthermore, the method also includes the step of further growing the barium borate crystal using the Czochralski method or the Czochralski method. These methods enable the preparation of large-sized crystals.

[0013] For example, the lifting method includes the following steps:

[0014] The barium borate crystal (seed crystal) prepared above is fixed on a seed crystal rod. The seed crystal is slowly lowered from the top of the crystal growth furnace to a position 5-10 mm above the liquid surface and preheated for 30-120 minutes. Then, the seed crystal is inserted 2-5 mm below the liquid surface and rotated at 10-30 rpm. The temperature is controlled to ensure that the melt at the seed crystal is saturated. The seed crystal is raised at a rate of 0.1-10 mm / h. Initially, the temperature is slightly lowered to allow the seed crystal to gradually thicken (i.e., shoulder formation). After shoulder formation, the temperature is kept constant. As the seed crystal continues to be raised, crystal growth occurs on the seed crystal until the crystal growth is complete. The seed crystal is then lifted to separate it from the liquid surface along with the grown crystal. The temperature is then lowered to room temperature at a rate of 10-30 °C / h to obtain a large-sized barium borate crystal.

[0015] For example, the bubble-forming method includes the following steps:

[0016] The barium borate crystal (seed crystal) prepared above is fixed on a seed crystal rod. The seed crystal is slowly lowered from the top of the crystal growth furnace to a position 5-10 mm above the liquid surface and preheated for 30-120 minutes. Then, the seed crystal is inserted 2-20 mm below the liquid surface and rotated at 10-30 rpm. The temperature is controlled to ensure that the melt at the seed crystal is saturated. The temperature is reduced at a rate of 0.1-1℃ / h, and the melt around the seed crystal gradually becomes supercooled. The melt crystallizes directionally onto the seed crystal, and the seed crystal grows slowly. Once the crystal growth is complete, the seed crystal is lifted to separate it from the liquid surface along with the grown crystal. Then, the temperature is reduced to room temperature at a rate of 10-30℃ / h to obtain a large-sized barium borate crystal.

[0017] In another aspect, the present invention provides yet another method for preparing barium borate crystals, which uses a crucible lowering method to prepare the barium borate crystals, specifically including the following steps:

[0018] The mixture of Ba2BeB2O6 compound or BaCO3, BeO, and H3BO3 with an optional flux is placed in a crystal growth apparatus, heated until all the material is melted, held at the temperature, and then the crystal growth apparatus is lowered vertically to obtain the barium borate crystal.

[0019] Furthermore, during the heating process, the heating rate is 1-35℃ / h, the temperature after heating is 1100-1200℃, and the holding time is 24-72h, more preferably 24-60h.

[0020] Furthermore, the descent rate of the crystal growth apparatus is 0.01 mm-25 mm / h, preferably 0.01 mm-20 mm / h. If the descent rate of the crystal growth apparatus is too fast, incomplete crystallization or inclusions and defects may occur.

[0021] An exemplary method for preparing the barium borate crystal using the crucible lowering method includes the following steps:

[0022] The mixture of Ba2BeB2O6 compound or BaCO3, BeO, and H3BO3 with an optional flux is placed in a crystal growth apparatus, heated until all the materials are melted, and held at the temperature to obtain a high-temperature solution.

[0023] The high-temperature solution is placed in a platinum crucible specifically designed for the descent method. The crucible is fixed on a crystal growth apparatus, and the temperature is controlled so that the bottom of the crucible is at the lowest point of the temperature field. This temperature is maintained for a certain period of time, and then the crystal growth apparatus is vertically lowered at a rate of 0.01 mm to 25 mm / h. As the crucible descends, the temperature at the bottom of the crucible first drops below the melting point, thus initiating crystallization. The crystal gradually grows as the crucible continues to descend. Once the apparatus reaches its lowest point, it is then cooled to room temperature at a rate of 10-30 °C / h to obtain a large-sized barium borate crystal.

[0024] In another aspect, the present invention provides yet another method for preparing barium borate crystals, the method comprising the following steps:

[0025] The mixture of Ba2BeB2O6 compound or BaCO3, BeO, H3BO3 and optional flux is placed in a platinum crucible, placed in a crystal growth furnace, heated to 850-900℃, and held at this temperature to obtain a high-temperature solution.

[0026] The high-temperature solution is cooled to 750-800℃ at a cooling rate of 0.5-10℃ / h, and then cooled to 650-700℃ at a cooling rate of 0.1-1℃ / h to obtain the barium borate crystals.

[0027] Furthermore, the heat preservation time is 12-36 hours. Heat preservation ensures a more uniform high-temperature solution.

[0028] Furthermore, the method also includes the step of further growing the barium borate crystal using a top seed method or a bubble-growth method.

[0029] For example, the top seed crystal method includes the following steps:

[0030] The barium borate crystal (seed crystal) prepared above is fixed on a seed crystal rod. The seed crystal is slowly lowered from the top of the crystal growth furnace to a position 5-10 mm above the liquid surface and preheated for 30-120 minutes. Then, the seed crystal is lowered further to contact the liquid surface, rotating at 10-30 rpm. The temperature is controlled to ensure that the melt at the seed crystal is saturated. The temperature is lowered to 650-700℃ at a rate of 0.1-1℃ / h. The high-temperature solution around the seed crystal gradually becomes supersaturated, and Ba2BeB2O6 gradually precipitates and crystallizes directionally on the seed crystal. The seed crystal grows slowly. After the crystal growth is complete, the seed crystal is lifted to separate it from the liquid surface along with the grown crystal. Then, it is cooled to room temperature at a rate of 10-30℃ / h to obtain a large-sized barium borate crystal.

[0031] For example, the bubble-forming method includes the following steps:

[0032] The barium borate crystal (seed crystal) prepared above is fixed on a seed crystal rod. The seed crystal is slowly lowered from the top of the crystal growth furnace to a position 5-10 mm above the liquid surface and preheated for 30-120 minutes. Then, the seed crystal is inserted 2-30 mm below the liquid surface and rotated at 10-30 rpm. The temperature is controlled so that the melt at the seed crystal is saturated. The temperature is reduced at a rate of 0.1-1℃ / h, and the melt around the seed crystal gradually becomes supercooled. The melt crystallizes directionally onto the seed crystal, and the seed crystal slowly grows. When the crystal growth is complete, the seed crystal is lifted so that it, along with the grown crystal, is separated from the liquid surface. Then, the temperature is reduced to room temperature at a rate of 10-30℃ / h to obtain a large-sized barium borate crystal.

[0033] Furthermore, in the preparation process of the above crystals, the molar ratio of BaCO3, BeO, and H3BO3 is 2:1:2.

[0034] Furthermore, in the preparation process of the above crystals, the molar ratio of the Ba2BeB2O6 compound or the mixture of BaCO3, BeO, and H3BO3 to the flux is 1:(0.5-6). For example, the molar ratio may include, but is not limited to, 1:(0.5-3), 1:(1-4), 1:(1.5-5), 1:(2-3), 1:(2.5-5.5), 1:(3-6), or 1:(4-5).

[0035] Furthermore, in the preparation process of the above crystals, the flux is selected from one or more of halides, alkali metal carbonates, and alkaline earth metal carbonates. For example, the halide is selected from one or more of NaF and BaF2.

[0036] For example, the molar ratio of NaF, BaF2, and H3BO3 is 1-2:2-3:4-7.

[0037] Furthermore, when the flux simultaneously contains halides, alkali metal carbonates, and alkaline earth metal carbonates, the total molar ratio of halides to alkali metal carbonates and alkaline earth metal carbonates is (1-2):(2-9). Preferably, it is (1-2):(1-3), (1-4):(1.5-4), (1.5-2.5):(1.5-5), (1.5-3.5):(2-7), (2-7.5):(2-5), (2-4.5):(2-9), etc.

[0038] Furthermore, in the preparation process of the above crystals, the Ba2BeB2O6 compound is prepared by a high-temperature solid-state metathesis reaction method, specifically including the following steps:

[0039] BaCO3, BeO and H3BO3 were mixed and heated to a constant temperature to obtain the borate compound.

[0040] Furthermore, the Ba2BeB2O6 compound is a pure phase.

[0041] Furthermore, the Ba2BeB2O6 compound can be prepared according to the following chemical equation:

[0042] 2BaCO3+BeO+2H3BO3=Ba2BeB2O6+2CO2+3H2O.

[0043] Furthermore, in the preparation process of the Ba2BeB2O6 compound, the molar ratio of BaCO3, BeO, and H3BO3 is 2-3:1-1.5:2-3, more preferably 2:1:2.

[0044] Furthermore, in the preparation process of the Ba2BeB2O6 compound, the heating temperature is 900℃-1100℃, more preferably 950-1050℃.

[0045] Furthermore, in the preparation process of the Ba2BeB2O6 compound, the heat preservation time is 24-72 hours, more preferably 24-48 hours.

[0046] Furthermore, in the technical solution of the present invention, the purity of BaCO3 is 90% or higher, preferably 95% or higher, and even more preferably 99% or higher.

[0047] Furthermore, in the technical solution of the present invention, the purity of BeO is 90% or higher, preferably 95% or higher, and even more preferably 99% or higher.

[0048] Furthermore, in the technical solution of the present invention, the purity of H3BO3 is 90% or higher, preferably 95% or higher, and even more preferably 99% or higher.

[0049] Furthermore, in one specific method, the preparation of the Ba2BeB2O6 compound includes the following steps:

[0050] BaCO3 (99.9% purity), BeO (99.9% purity), and H3BO3 (99.9% purity) were weighed in a molar ratio of 2:1:2 and ground in a mortar. The reaction mixture was then placed in a heating device and slowly heated at 950℃~1050℃ for 48~72 hours. The muffle furnace was then turned off and allowed to cool naturally. The resulting product was then placed in a mortar and ground thoroughly. After grinding, the product was placed back in the heating device for another heating, holding, and natural cooling to obtain the Ba2BeB2O6 compound.

[0051] In another aspect, the present invention provides the application of barium boroberyllate crystals as described above in the fields of optics and communication micromachining.

[0052] Furthermore, the barium borate crystal is used in the fabrication of a phase delayer.

[0053] Furthermore, the barium boroberylate crystal is used in the preparation of zero-order glass slides.

[0054] The beneficial effects of this invention are as follows:

[0055] The barium borate crystal described in this invention belongs to the orthorhombic crystal system, is a biaxial crystal, and has a wide transmission range, from ultraviolet to mid-far infrared. XRD tests before and after melting show that the compound is uniformly molten. The crystal has extremely low birefringence, with a birefringence of approximately 0.0024 at 532 nm. This birefringence value supports the application of this crystal on zero-order glass slides. Attached Figure Description

[0056] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0057] Figure 1 The polycrystalline XRD pattern of Ba2BeB2O6 powder in Example 1 is shown.

[0058] Figure 2 The XRD patterns of the Ba2BeB2O6 powder prepared in Example 1 before and after polycrystalline melting are shown.

[0059] Figure 3 A schematic diagram of the Ba2BeB2O6 crystal structure in Example 2 is shown.

[0060] Figure 4 A schematic diagram of a polarizing prism made from Ba2BeB2O6 crystals in Example 5 is shown. Detailed Implementation

[0061] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0062] Unless otherwise stated, all raw materials and reagents described in the examples are commercially available products.

[0063] Example 1

[0064] Synthetic compound barium borate pure phase

[0065] According to the reaction equation:

[0066] 2BaCO3+BeO+2H3BO3=Ba2BeB2O6+2CO2+3H2O

[0067] BaCO3, BeO, and H3BO3 were weighed in appropriate amounts according to the stoichiometric ratio of 2:1:2 as shown in the above reaction chemical equation. The mixture was then ground evenly in a mortar, placed in a platinum crucible, and placed in a muffle furnace. The furnace was slowly heated to 1000℃ and held at that temperature for 24 hours. The temperature was then lowered to room temperature at a rate of 5℃ / h. The furnace was then turned off, the crucible was removed, and the sample was ground thoroughly in the mortar. This process was repeated three times to obtain the pure phase of the compound Ba2BeB2O6, i.e., Ba2BeB2O6 polycrystalline powder. X-ray diffraction (XRD) analysis was then performed on this pure phase polycrystalline powder. The obtained XRD pattern was compared with the theoretically simulated XRD pattern of Ba2BeB2O6 (wherein, the theoretically simulated XRD result is as follows). Figure 1 as well as Figure 2 It is consistent with curve 1 in the figure.

[0068] Take an appropriate amount of the Ba2BeB2O6 polycrystalline powder from Example 1 (its XRD pattern is shown in Figure 1). Figure 2 The polycrystalline powder (as shown in curve 2) was placed in a platinum crucible and then placed in a muffle furnace, heated to 1120°C, held at that temperature for one day, then cooled to 1000°C over a week, and finally cooled to room temperature over two days. The XRD pattern of the treated polycrystalline powder is shown below. Figure 2 As shown in curve 3, this compound is a homogeneous melt (uniform melt) compound.

[0069] Example 2

[0070] Growth of barium borate crystals

[0071] The Ba2BeB2O6 compound synthesized in Example 1 was placed in a platinum crucible and then placed in a muffle furnace. The temperature was slowly raised to 1100°C and held for 24 hours. Then, the temperature was lowered to 950°C at a rate of 0.5°C / h. The muffle furnace was then turned off and allowed to cool naturally to room temperature to obtain colorless crystals of Ba2BeB2O6.

[0072] Figure 3 A schematic diagram of the obtained Ba2BeB2O6 crystal structure is shown. The structure was obtained by using an X-ray single-crystal diffractometer to collect data from the crystal and then solving it using OLEX2 software.

[0073] Example 3

[0074] Barium borate crystals grown by crucible descent method

[0075] The Ba2BeB2O6 compound synthesized in Example 1 above was loaded into... The material is placed in a platinum crucible, covered, and then placed in a crystal growth furnace. The temperature is slowly raised to 1100℃ to completely melt the material. After the material is completely melted, the growth apparatus is lowered vertically at a speed of 0.05 mm / h. After the growth is completed, the crystal growth apparatus is lowered to room temperature at a speed of 100℃ / h, and the furnace is turned off to obtain colorless crystal Ba2BeB2O6 with a size of φ40mm*10mm.

[0076] Example 4

[0077] Flux method for growing barium borate crystals

[0078] BaCO3, BeO, H3BO3, and flux BaF2 were mixed and ground in a molar ratio of 4:2:6:1, placed in a platinum crucible, and then placed in a muffle furnace. The mixture was heated to 980°C to obtain a high-temperature melt, which was then held at this temperature for a certain period of time. Subsequently, the melt was cooled to room temperature at a cooling rate of 1°C / h to obtain the crystal with dimensions of 10*10*2mm. 3 .

[0079] Example 5

[0080] Preparation of barium boroberyllate crystals for fabrication of zero-order glass slides

[0081] After orienting the Ba2BeB2O6 crystal from Example 4, an easily machinable direction was selected, the magnitude of birefringence in that direction was determined, and then it was cut and polished to produce a shape as shown. Figure 4 The polarizing prism shown is an example. In this embodiment, the selected direction is (001), corresponding to birefringences of 0.0024@532nm, 0.0030@285nm, and 0.0025@1064nm, with corresponding dimensions of 10*20*0.1mm. 3 10*20*0.05mm 3 10*20*0.2mm 3 The corresponding true zero-order glass slides are half-glass slides with wavelengths of 532nm, 283nm, and 1064nm, respectively.

[0082] Comparative Example

[0083] In this embodiment of the invention, attempts were made to replace Ba with Sr, Ca or Mg, and high-temperature solid-phase synthesis experiments were conducted, but the target compounds such as Sr2BeB2O6, Ca2BeB2O6 and Mg2BeB2O6 were not successfully synthesized.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A barium oxybororberyllate crystal, characterized in that, The chemical formula of the crystal is Ba2BeB2O6, the structure is non-central symmetric, belongs to the orthorhombic system, and the space group is , the cell parameter is , .

2. The method of producing barium boryl-beryllate crystal according to claim 1, wherein The barium boron beryllate crystal is prepared by a melt method, which comprises the following steps: The Ba2BeB2O6 compound or a mixture of BaCO3, BeO and H3BO3 is mixed with an optional fluxing agent, heated to melt to obtain a high-temperature melt, and then cooled to room temperature to obtain the barium boron beryllate crystal.

3. The production method according to claim 2, characterized by, The heating rate is 1-35 ℃ / h, the temperature after heating is 1100-1200 ℃, and the holding time is 12-72 h.

4. The production method according to claim 2, characterized by, The holding time is 12-36 h.

5. The preparation method according to claim 2, characterized in that, The cooling rate is 0.5-10 ℃ / h to 1050-1100 ℃, then 0.1-1 ℃ / h to 950-1000 ℃, and then naturally cooled to room temperature.

6. The preparation method according to claim 2, characterized in that, The method further comprises the step of further growing the barium boron beryllate crystal by using a Czochralski method or a Kyropoulos method.

7. The method of producing barium boryl-beryllate crystal as claimed in claim 1, wherein The method further comprises the step of further growing the barium boron beryllate crystal by using a Czochralski method or a Kyropoulos method. The Ba2BeB2O6 compound or a mixture of BaCO3, BeO and H3BO3 is mixed with an optional fluxing agent, heated to melt to obtain a high-temperature melt, and then cooled to room temperature to obtain the barium boron beryllate crystal.

8. The method of claim 7, wherein, The heating rate is 1-35 ℃ / h, the temperature after heating is 1100-1200 ℃, and the holding time is 12-72 h.

9. The production method according to claim 8, characterized by, The holding time is 12-36 h.

10. The method of claim 7, wherein, The cooling rate is 0.5-10 ℃ / h to 1050-1100 ℃, then 0.1-1 ℃ / h to 950-1000 ℃, and then naturally cooled to room temperature.

11. The preparation method according to claim 7, characterized in that, The method further comprises the step of further growing the barium boron beryllate crystal by using a Czochralski method or a Kyropoulos method.

12. The method of producing barium boryl-beryllate crystal as claimed in claim 1, wherein The method further comprises the step of further growing the barium boron beryllate crystal by using a Czochralski method or a Kyropoulos method. The method further comprises the step of further growing the barium boron beryllate crystal by using a Czochralski method or a Kyropoulos method. The Ba2BeB2O6 compound or a mixture of BaCO3, BeO and H3BO3 is mixed with an optional fluxing agent, heated to melt to obtain a high-temperature melt, and then cooled to room temperature to obtain the barium boron beryllate crystal.

13. The method of claim 12, wherein, The heating rate is 1-35 ℃ / h, the temperature after heating is 1100-1200 ℃, and the holding time is 12-72 h.

14. The method of any one of claims 2-12, wherein, The holding time is 12-36 h. The cooling rate is 0.5-10 ℃ / h to 1050-1100 ℃, then 0.1-1 ℃ / h to 950-1000 ℃, and then naturally cooled to room temperature. The method further comprises the step of further growing the barium boron beryllate crystal by using a Czochralski method or a Kyropoulos method.

15. The method of any one of claims 2-12, wherein, The molar ratio of BaCO3, BeO and H3BO3 is 2:1:2; and / or The molar ratio of the Ba2BeB2O6 compound and the fluxing agent is 1:(0.5-6); and / or 16. The method of claim 15, wherein, The fluxing agent is selected from one or more of alkali metal carbonates and alkaline earth metal carbonates.

17. The preparation method according to claim 15, characterized in that, The Ba2BeB2O6 compound is prepared by a high-temperature solid-phase re-crystallization method, which comprises the following steps:

18. The method of claim 15, wherein, The Ba2BeB2O6 compound is prepared by a high-temperature solid-phase re-crystallization method, which comprises the following steps:

19. The method of claim 15, wherein, The molar ratio of BaCO3, BeO and H3BO3 is 2-3:1-1.5:2-3.

20. The method of claim 15, wherein, The molar ratio of BaCO3, BeO and H3BO3 is 2:1:

2. The heating temperature is 900-1100 ℃. The heating temperature is 950-1050 ℃. The holding time is 24-72 h.

21. The method of claim 15, wherein, The time for the heat preservation is 24-48 hours.

22. The use of the barium oxyboron beryllate crystal of claim 1 in the field of optics and communication micro-processing.

23. The use according to claim 22, characterized in that, The barium oxyboron beryllate crystal is used in the preparation of a phase retarder.

24. The use according to claim 23, characterized in that, The barium oxyboron beryllate crystal is used in the preparation of a zero-order glass sheet.

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