A symmetrical low-temperature phase barium metaborate (β-BBO) crystal, its preparation method and application

Abstract

This application discloses a symmetrical low-temperature phase barium metaborate (β-BBO) crystal, its preparation method, and its application. The symmetrical β-BBO crystal is trigonal symmetrical and includes three trigonal pyramidal facets S and three hexagonal prismatic facets P. The symmetrical β-BBO crystal prepared in this application is trigonal symmetrical and has complete crystal faces at constant diameter, making it easy to mass-produce large-size, high-quality β-BBO crystals.

Description

Technical Field

[0001] This application relates to a symmetrical low-temperature phase barium metaborate (β-BBO) crystal, its preparation method, and its application, belonging to the field of crystal material technology. Background Technology

[0002] Low-temperature phase barium metaborate (β-BBO) crystal is a very important nonlinear optical crystal with many important properties, such as a wide transmission band (200-2500 nm), a large effective frequency doubling factor (deff = 6deffKDP, @1.06 μm), a high birefringence (no-ne = 0.115, @1.06 μm), and a high resistance to optical damage threshold (approximately 10 GW / cm at 1064 nm). 2 Therefore, it is widely used in laser frequency doubling and third harmonicization. In recent years, with the development of laser technology, the application of β-BBO crystals in electro-optic Q-switches has also greatly developed, thus β-BBO has broad application prospects and good economic value.

[0003] After more than 30 years of exploration and research in crystal growth, many methods have been developed for growing β-BBO crystals, such as the Czochralski method, molten salt method, and moving zone melting method. However, due to the phase transition in BBO crystals, the growth of β-BBO crystals still presents many challenges, making it relatively difficult to obtain large-size, high-quality β-BBO crystals. Summary of the Invention

[0004] This application analyzes the structure and symmetry of BBO crystals, and calculates the Ba-O bonds and [B3O6] in the β-BBO structure. 3- The binding energy of the BO bond in the ring was investigated using the periodic bond chain (PBC) theory and the crystal growth group theory to study the crystallization habit and growth kinetics of β-BBO crystal. According to the calculation and analysis based on the PBC theory and the crystal growth group theory, the crystal exhibits the crystal facet characteristics of a trigonal crystal system. The three trigonal pyramidal faces S at the constant diameter have an angle of 60° with the (0001) face (where the (0001) face is the bottom horizontal plane of the grown crystal). The hexagonal prism face P is perpendicular to the (0001) face, where S corresponds to the (1-102)(-1012)(01-12) crystal faces and P corresponds to the (11-20)(1-210)(-2110) crystal faces.

[0005] The molten salt Czochralski method was employed for growth, with fluxes including BaF2, LiF, Na2O, NaF, NaBaBO3, and Ba2Na3[B3O6]F. By setting a symmetric temperature field and adjusting the molten salt Czochralski growth process, a φ80×50mm crystal with a complete crystal plane was obtained. 3Large-size, high-quality β-BBO crystals were grown using this method. The resulting β-BBO crystals exhibited trigonal symmetry, with three very smooth and complete trigonal pyramidal surfaces S and three hexagonal prismatic surfaces P observed along the c-axis. The angle between the S-face and the base was 60°, and the P-face was perpendicular to the base. By utilizing the inherent crystal structure of BBO, trigonal symmetric β-BBO crystals can be grown, resulting in large-size, high-quality β-BBO crystals.

[0006] According to one aspect of this application, a symmetrical β-BBO crystal is provided, wherein the symmetrical β-BBO crystal is trigonal symmetrical;

[0007] The symmetrical β-BBO crystal comprises three trigonal pyramidal faces S and three hexagonal prismatic faces P.

[0008] Optionally, the trigonal pyramidal surface S forms an angle of 60° with the bottom horizontal plane of the crystal, and the hexagonal prism surface P is perpendicular to the bottom horizontal plane of the crystal.

[0009] Optionally, the trigonal pyramidal surface S corresponds to the (1-102)(-1012)(01-12) crystal plane, and the hexagonal prism surface P corresponds to the (11-20)(1-210)(-2110) crystal plane.

[0010] Optionally, the symmetrical β-BBO crystal has a dimension of 30 mm to 50 mm along the c-axis.

[0011] Optionally, the dimensions of the symmetrical β-BBO crystal along the c-axis are selected from any value among 30mm, 35mm, 40mm, 45mm, and 50mm, or the range between any two of the above points.

[0012] Optionally, the symmetric β-BBO crystal has a size of φ50×30mm. 3 ~φ110×50mm 3 .

[0013] Optionally, the size of the symmetric β-BBO crystal is selected from φ50×30mm. 3 φ60×30mm 3 φ80×30mm 3 φ80×50mm 3 φ100×30mm 3 φ110×30mm 3 φ110×50mm 3 Any value in the range or any two points mentioned above.

[0014] According to another aspect of this application, a method for preparing the above-described symmetric β-BBO crystal is provided, the method comprising the following steps:

[0015] (1) Using a solid-phase synthesis method, barium metaborate compound polycrystalline powder is obtained from raw materials containing barium carbonate and boric acid.

[0016] (2) The raw material containing barium borate compound polycrystalline powder and flux is melted and crystal grown in a trigonal symmetric temperature field by the Czochralski method to obtain the symmetric β-BBO crystal.

[0017] Optionally, during crystal growth, seed crystals are grown along the c-axis. When the crystal reaches the shoulder formation stage, the β-BBO crystal is controlled to grow into a triangular trigonal symmetrical shape. Then, based on the triangle, the symmetrical β-BBO crystal is cultivated in the constant diameter stage.

[0018] Optionally, the trigonal symmetric temperature field is a trigonal symmetric heat insulation cover, and the material of the trigonal symmetric heat insulation cover is selected from at least one of alumina and zirconium oxide.

[0019] Optionally, the molar ratio of barium carbonate to boric acid is 1:2, wherein the molar amount of barium carbonate is expressed in terms of the molar amount of barium element, and the molar amount of boric acid is expressed in terms of the molar amount of boron element.

[0020] Optionally, the molar ratio of the barium metaborate compound polycrystalline powder to the flux is 4:1 to 1:1.

[0021] Optionally, the flux is selected from at least one of BaF2, BaCl2, LiF, Na2O, NaF, CaF2, NaBaBO3, and Ba2Na3[B3O6]F.

[0022] Optionally, the growth conditions for the lifting method are: a growth temperature of 800℃~920℃, a cooling rate of 0.01~1℃ / day, and a lifting speed of 0.01~2 mm / hour.

[0023] Optionally, the growth temperature is selected from any value of 800℃, 820℃, 850℃, 880℃, 900℃, 920℃ or a range between any two of the above points.

[0024] Optionally, the cooling rate is selected from any value among 0.01℃ / day, 0.05℃ / day, 0.1℃ / day, 0.5℃ / day, and 1℃ / day, or a range between any two of the above points.

[0025] Optionally, the lifting speed is selected from any value among 0.01 mm / h, 0.1 mm / h, 0.2 mm / h, 0.5 mm / h, 1 mm / h, 1.5 mm / h, 2 mm / h, or a range between any two of the above points.

[0026] Optionally, the crystal growth rotation speed is 1 to 20 revolutions per minute, and the crystal growth time is 15 to 120 days.

[0027] Optionally, the rotational speed of the crystal growth is selected from any value among 1 rpm, 2 rpm, 3 rpm, 5 rpm, 7 rpm, 10 rpm, and 20 rpm, or a range between any two of the above points.

[0028] Optionally, the crystal growth time is selected from any value of 15 days, 30 days, 40 days, 50 days, 60 days, 70 days, 80 days, 90 days, 100 days, 110 days, or 120 days, or a range between any two of the above points.

[0029] Optionally, the crystal growth further includes a cooling process, wherein the cooling rate is 5–20 °C / h.

[0030] Optionally, the cooling rate of the cooling process is selected from any value among 5℃ / h, 7℃ / h, 10℃ / h, 12℃ / h, 15℃ / h, 18℃ / h, and 20℃ / h, or a range between any two of the above points.

[0031] Optionally, the active atmosphere for the Czochralski growth process is an air atmosphere or a mixed atmosphere containing 1-5% oxygen in a flowing atmosphere.

[0032] According to another aspect of this application, at least one of the above-described symmetric β-BBO crystal and the symmetric β-BBO crystal prepared by the above-described preparation method is provided for use in laser frequency doubling, third harmonication, and electro-optic Q-switching.

[0033] In this application, the structure of BBO crystal was analyzed using the periodic bond chain (PBC) theory and the crystal growth group theory. It was found that the β-BBO crystal exhibits a trigonal crystal system along the c-axis, with the trigonal pyramidal surface S and the (0001) plane (where the (0001) plane should be the bottom horizontal plane of the grown crystal) having an angle of 60°, and the hexagonal prism surface P being perpendicular to the (0001) plane.

[0034] In the flux-molten salt Czochralski method for growing β-BBO crystals, a symmetric temperature field was designed, a seed crystal was used along the c-axis, and a suitable crystal growth process was studied. During the constant-diameter stage of crystal growth, three trigonal pyramidal faces S (S corresponding to the (1-102)(-1012)(01-12) crystal planes) and three hexagonal prismatic faces P (P corresponding to the (11-20)(1-210)(-2110) crystal planes) were forcibly grown to obtain large-size, high-quality β-BBO crystals.

[0035] As a specific implementation method, this application is achieved through the following technical solution:

[0036] The specific growth process of the molten salt lifting method is as follows:

[0037] Synthesis of crystal growth raw materials: Traditional solid-state synthesis methods were employed. The initial raw materials were BaCO3 and H3BO3. Based on the molecular formula BaB2O4, the raw materials were accurately weighed according to the molar ratio of each substance in the formula (Ba:B = 1:2), with a slight excess of H3BO3 (0.01–2 at%). The mixture was ground and mixed evenly in a ball mill and pressed into blocks. The blocks were placed in a corundum cup and heated to 600℃ in a muffle furnace at a heating rate of 150℃ / h, and held at 600℃ for 24 hours. The mixture was then removed, ground and mixed again, pressed into tablets, and heated to 850℃ at a heating rate of 200℃ / h. The tablets were held at 850℃ for 24 hours. After cooling, polycrystalline powder of barium metaborate was obtained. X-ray analysis showed that the obtained X-ray spectrum was consistent with that of barium metaborate single crystal powder, indicating that this polycrystalline powder raw material is suitable for crystal growth.

[0038] The molten salt Czochralski process requires the selection of a suitable flux. Several fluxes can be selected, such as Na2O, NaF, NaBaBO3, and Ba2Na3[B3O6]F.

[0039] The molten salt Czochralski method is used to grow low-temperature barium metaborate (β-BBO) crystals. The main growth conditions are as follows: A platinum crucible is used to prepare the β-BBO crystal polycrystalline raw material and the flux NaF in a 4:1 ratio. The molten salt Czochralski furnace is slowly heated to approximately 1100℃ to completely melt and homogenize the polycrystalline raw material, then cooled to approximately 920℃ for crystal growth. Crystal growth is carried out in an air atmosphere, or in a mixed atmosphere containing 1-5% oxygen. First, a trigonal symmetric heat preservation hood is designed to obtain a symmetric temperature field. Second, a seed crystal in the c-direction (i.e., the

[0001] direction) is selected for crystal growth. During the shoulder-forming stage of crystal growth, the β-BBO crystal was controlled to grow into a triangular triangular shape with trigonal symmetry. Then, during the constant-diameter stage, based on the triangular shape, three trigonal pyramidal faces S (S corresponding to the (1-102)(-1012)(01-12) crystal planes) and three hexagonal prismatic faces P (P corresponding to the (11-20)(1-210)(-2110) crystal planes) were forcibly grown. The crystal growth parameters were: growth temperature 920℃, cooling rate 0.01~1℃ / day, pulling speed 0.1~2 mm / day, crystal rotation speed 1~20 rpm. After 30~120 days of growth, once the crystal reached the desired size, it was removed from the liquid surface and cooled to room temperature at a rate of 5~20℃ / h to obtain a crystal with a size of φ80×50mm. 3 High-quality β-BBO crystals.

[0040] The beneficial effects that this application can produce include:

[0041] 1) The symmetrical β-BBO crystal prepared in this application is trigonal symmetric and has complete crystal planes at constant diameter. The β-BBO crystal can be easily mass-produced to obtain large-size, high-quality β-BBO crystals.

[0042] 2) The symmetrical β-BBO crystal prepared in this application has a size of φ80×50mm. 3 High-quality β-BBO crystals. Attached Figure Description

[0043] Figure 1 This is a top view of the symmetrical β-BBO crystal prepared in Example 1 of this application.

[0044] Figure 2 This is a side view of the symmetrical β-BBO crystal prepared in Example 1 of this application.

[0045] Figure 3 This is a side view of the symmetrical β-BBO crystal prepared in Example 1 of this application.

[0046] Figure 4 Interference fringe pattern of the symmetrical β-BBO crystal prepared in Example 1 of this application. Detailed Implementation

[0047] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0048] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0049] The lifting furnace adopts either the DJL-400 from Xi'an Bairui Company or the automatic lifting furnace of Wuxi Lande, etc.

[0050] This application uses the ZYGO VeriFIne XPZ laser interferometer to test the optical uniformity of a symmetric β-BBO crystal.

[0051] Specific chemical reaction formula:

[0052] BaCO3+2H3BO3=BaB2O4+CO2+3H2O

[0053] Purity and manufacturers of the raw materials used:

[0054] Drug Name purity factory <![CDATA[H3BO3]]> 99.9％ China National Pharmaceutical Group Shanghai Chemical Reagent Company, Aladdin Company <![CDATA[BaCO3]]> 99.9％ China National Pharmaceutical Group Shanghai Chemical Reagent Company, Aladdin Company

[0055] Example 1

[0056] The specific growth process of the molten salt lifting method is as follows:

[0057] Synthesis of crystal growth raw materials: A traditional solid-state synthesis method was adopted. The initial raw materials were BaCO3 and H3BO3. Based on the molecular formula BaB2O4, 1973.4 g of BaCO3 and 1239.5 g of H3BO3 were accurately weighed according to the molar ratio of each substance in the molecular formula (Ba:B = 1:2). The raw material, H3BO3, is prepared by grinding and mixing it evenly in a ball mill (0.01–2 at%), and then pressing it into blocks. The blocks are placed in a corundum cup and heated to 600℃ in a muffle furnace at a heating rate of 150℃ / h, and held at 600℃ for 24 hours. The mixture is then removed, ground, and mixed again until homogeneous. The mixture is pressed into tablets, heated to 850℃ at a heating rate of 200℃ / h, and held at 850℃ for 24 hours. After cooling, a polycrystalline powder of barium metaborate is obtained. X-ray analysis shows that the obtained X-ray spectrum is consistent with that of barium metaborate single crystal powder. The polycrystalline powder prepared by solid-state synthesis is used for the growth of symmetric β-BBO crystals. NaF is selected as the co-solvent, and 105.1 g of NaF is weighed according to a BBO:NaF molar ratio of 4:1.

[0058] Low-temperature barium metaborate (β-BBO) crystals were grown using the molten salt Czochralski method. The growth conditions were as follows: In a Czochralski furnace, polycrystalline powder raw materials prepared by solid-state synthesis and flux NaF were placed in a platinum crucible at a ratio of 4:1. The molten salt Czochralski furnace was slowly heated to approximately 1100°C to completely melt and homogenize the polycrystalline raw materials, and then cooled to approximately 920°C for crystal growth. Crystal growth was carried out in an air atmosphere. First, a trigonal symmetric heat insulation hood was designed to obtain a symmetric temperature field. Second, a seed crystal in the c-direction (i.e., the

[0001] direction) was selected for crystal growth. During the shoulder formation stage of crystal growth, the β-BBO crystal was controlled to grow into a triangular triangular shape with trigonal symmetry. Then, during the constant diameter stage, forced growth was performed based on the triangular shape to obtain three trigonal pyramidal faces S (S corresponding to the (1-102)(-1012)(01-12) crystal planes) and three hexagonal prismatic faces P (P corresponding to the (11-20)(1-210)(-2110) crystal planes). The crystal growth parameters were: growth temperature 920℃, cooling rate 0.01~1℃ / day, pulling speed 0.1~2 mm / day, and crystal rotation speed 5 rpm. After 30 days of growth, once the crystal reached the desired size, it was removed from the liquid surface and cooled to room temperature at a rate of 20℃ / h to obtain a size of φ80×50mm. 3 High-quality β-BBO crystals.

[0059] like Figure 1-3As shown in the figure, a symmetrical β-BBO crystal with complete crystal faces was prepared. The crystal is trigonal symmetric, with three trigonal pyramidal faces S at the constant diameter section. The angle between the S and the (0001) plane (where the (0001) plane is the bottom horizontal plane of the grown crystal) is 60°. The hexagonal prism face P is perpendicular to the (0001) plane, where S corresponds to the (1-102)(-1012)(01-12) crystal faces and P corresponds to the (11-20)(1-210)(-2110) crystal faces. Based on the crystal structure of BBO itself, a trigonal symmetric β-BBO crystal was grown, resulting in a large-size, high-quality β-BBO crystal.

[0060] like Figure 4 As shown in the figure, the interference fringes of the crystal are parallel and identical, indicating that the crystal is of good quality. The measured optical homogeneity is 1.3 × 10⁻⁶. -6 / mm.

[0061] 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 symmetrical β-BBO crystal, characterized in that, The preparation method includes the following steps: (1) Using a solid-phase synthesis method, barium metaborate compound polycrystalline powder is obtained from raw materials containing barium carbonate and boric acid; (2) Using the Czochralski method in a trigonal symmetric temperature field, raw materials containing barium borate compound polycrystalline powder and flux are melted and crystal grown to obtain the symmetric β-BBO crystal; wherein, the trigonal symmetric temperature field is achieved by a trigonal symmetric heat insulation cover, and the material of the trigonal symmetric heat insulation cover is selected from at least one of alumina and zirconium oxide; during crystal growth, seed crystal growth is carried out in the c-axis direction, and when the growth reaches the shoulder stage, the β-BBO crystal is controlled to grow into a trigonal symmetric triangular shape, and then the symmetric β-BBO crystal is obtained by relying on the triangle in the constant diameter stage; The symmetrical β-BBO crystal is trigonal symmetric, with its side surface along the c-axis consisting of three trigonal pyramidal surfaces S and three hexagonal prismatic surfaces P. The angle between the trigonal pyramidal surfaces S and the bottom horizontal plane of the crystal is 60°, and the hexagonal prismatic surfaces P are perpendicular to the bottom horizontal plane of the crystal. The trigonal pyramidal surfaces S correspond to the (1-102)(-1012)(01-12) crystal plane, and the hexagonal prismatic surfaces P correspond to the (11-20)(1-210)(-2110) crystal plane. The crystal's dimensions along the c-axis are 30mm to 50mm, and its optical uniformity is better than 1.5×10⁻⁶. -6 / mm, the size of the symmetrical β-BBO crystal is φ50×30mm. 3 ~φ110×50mm 3 .

2. The preparation method according to claim 1, characterized in that, The molar ratio of barium carbonate to boric acid is 1:2, wherein the molar amount of barium carbonate is expressed in terms of the molar amount of barium element, and the molar amount of boric acid is expressed in terms of the molar amount of boron element. The molar ratio of the barium metaborate compound polycrystalline powder to the flux is 4:1 to 1:1; The flux is selected from at least one of BaF2, BaCl2, LiF, Na2O, NaF, CaF2, NaBaBO3, and Ba2Na3[B3O6]F.

3. The preparation method according to claim 1, characterized in that, The growth conditions for the lifting method are: growth temperature of 800 ℃~920 ℃, cooling rate of 0.01~1 ℃ / day, and lifting speed of 0.01~2 mm / hour; The crystal growth rotation speed is 1~20 rpm, and the crystal growth time is 15~120 days.

4. The preparation method according to claim 1, characterized in that, The crystal growth process also includes a cooling process, wherein the cooling rate is 5~20℃ / h.

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