Ba3Sc2(BO3)4 ultraviolet birefringent crystals, preparation and applications

Abstract

The present invention provides a Ba3Sc2(BO3)4 ultraviolet birefringent crystal, preparation and application. The Ba3Sc2(BO3)4 ultraviolet birefringent crystal has a centrosymmetric structure, belongs to the trigonal crystal system, has a space group of P-3m1, and has unit cell parameters of #imgabs0##imgabs1#α=90°, β=90°, γ=120°, Z=1, #imgabs2#. The room temperature transmission spectrum shows that the ultraviolet birefringent crystal has a wide transmission range (0.2~3.5μm), a transmittance of more than 70%, a short ultraviolet cutoff edge (198nm) and a large birefringence (Δn=0.145), and has the advantages of stable physicochemical properties, good mechanical properties, not easy to deliquesce, easy to cut, polished and stored, and is expected to be widely used in the field of ultraviolet birefringent optical materials. In the present invention, a flux method is adopted to prepare the ultraviolet birefringent crystal, which is simple to operate, the raw materials are readily available, and the preparation conditions are easy to achieve.

Description

Technical Field

[0001] The present invention relates to the field of ultraviolet birefringence optical materials, and more specifically to a Ba3Sc2(BO3)4 ultraviolet birefringence crystal, its preparation and application. Background Art

[0002] Ultraviolet birefringent materials can modulate the polarization of ultraviolet light and have a wide range of applications in civil, industrial and scientific research fields. So far, a series of ultraviolet birefringent crystals include MgF2, α-BaB2O4, YBa3B9O 18 , Ca3(BO3)2, etc. have been reported and commercialized. However, their own shortcomings have seriously hindered their wider practical application: MgF2 is limited by its small birefringence (0.012@405nm); in addition to its large anisotropic thermal expansion coefficient and easy deliquescent properties, the phase transition between α phase and β phase makes it impossible to obtain high-quality bulk crystals of α-BaB2O4; for YBa3B9O 18 Due to severe absorption centered at 400nm, its transmittance drops sharply from 500nm to 220nm, leaving only 10%; Ca3(BO3)2 also exhibits small birefringence (0.0968@630nm) and low transmittance below 200nm. Therefore, finding a new ultraviolet birefringent material that can simultaneously meet the two key objectives of having a birefringence as large as that of α-BaB2O4 and high transmittance in the ultraviolet region remains a crucial research direction.

[0003] As the research deepened, in terms of birefringence, the researchers found that both anionic groups and cationic polyhedrons have significant contributions to birefringence. For anionic groups, planar π-conjugated groups with large anisotropic polarizability, especially BO3 and B3O6 groups, are ideal candidates for birefringent functional groups. For cations, cations with high coordination numbers, such as Ba, Zn and Mg, are conducive to forming MO with oxygen atoms and fluorine atoms. n F m Polyhedron; thus, the oxygen atoms on the equatorial plane connect the planar functional groups to form a layered structure. In each layer, due to the MO n F mThe uniform tension generated by the spatial effect of the polyhedron allows the planar anions to be arranged in the same layer in an optimal planar manner. In the overall layered structure, the anionic groups that contribute to birefringence are structurally maximized, resulting in a large refractive index. In addition, the BO bond exhibits strong covalency and highly localized valence electrons, which enable it to obtain a short UV cutoff wavelength and high transmittance in the ultraviolet region. Therefore, layered borates containing BO3 and B3O6 are considered to be a hot area for exploring ultraviolet birefringent materials with excellent optical properties, such as NaMgBO3, Ba2MgBO3, Ba2Zn(B3O6)2 and NH4B4O6F; and for the problem of how to obtain materials with shorter UV absorption cutoff edges and wide transmittance range, alkaline and alkaline earth metals without dd or ff electrons and materials with d 0 Electronic configuration of Sc 3+ / Y 3+ It is beneficial to obtain high transmittance and a shorter UV cutoff edge in the ultraviolet region. However, to date, there are relatively few studies on the preparation of perfect layered Ba-Sc-BO crystals with a short UV absorption cutoff edge, a wide transmittance range and a large birefringence effect.

[0004] Therefore, in order to solve the above problems, it is necessary to provide a new Ba-Sc-BO series ultraviolet birefringent crystal. Summary of the Invention

[0005] The first object of the present invention is to provide an ultraviolet birefringent crystal, which has the advantages of a wide transmission range (0.2 to 3.5 μm), high transmittance, a short ultraviolet cutoff edge (198 nm), a large birefringence (Δn=0.145), and is easy to grow.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned ultraviolet birefringent crystal.

[0007] The third object of the present invention is to provide a method for preparing the ultraviolet birefringent crystal.

[0008] A fourth object of the present invention is to provide a method for preparing the ultraviolet birefringent crystal.

[0009] A fifth object of the present invention is to provide an application of the ultraviolet birefringent crystal as described above.

[0010] To achieve the first object, the present invention provides a UV birefringent crystal having a chemical formula of Ba3Sc2(BO3)4, a centrosymmetric structure, a trigonal system, a space group of P-3m1, and unit cell parameters of α=90°, β=90°, γ=120°, Z=1,

[0011] According to a specific embodiment of the present invention, the size of the Ba3Sc2(BO3)4 crystal is at the millimeter level. Exemplarily, the size of the Ba3Sc2(BO3)4 crystal is (15-20) mm×(13-20) mm×(8-15) mm, for example, 18 mm×16 mm×10 mm.

[0012] According to a specific embodiment of the present invention, the scandium borate barium compound Ba3Sc2(BO3)4 crystal has a transmittance of more than 70% in the wavelength range of 0.2 to 3.5 μm, an ultraviolet cutoff edge of 198 nm, and a large birefringence (Δn=0.145), which is verified by semi-empirical theoretical calculations (Δn=0.115).

[0013] To achieve the second object, the present invention provides a method for preparing the ultraviolet birefringent crystal, comprising the following steps:

[0014] The barium-containing compound, the scandium-containing compound and the boron-containing compound are mixed into raw material powder in proportion, heated in a platinum crucible, pre-sintered, cooled to room temperature, ground, sintered, and cooled to obtain Ba3Sc2(BO3)4 powder;

[0015] Ba3Sc2(BO3)4 powder is mixed evenly with a flux to obtain a crystal growth material, the crystal growth material is placed in a crystal growth furnace, heated to a molten state, and first cooled to the crystal growth temperature. After the growth is completed, the crystal is raised to above the melt liquid surface, and then cooled to room temperature for a second time to obtain Ba3Sc2(BO3)4 crystal.

[0016] Furthermore, the rate of the first cooling is 0.5-2°C / h, the rate of the second cooling is 5-15°C / h, and the crystal growth temperature is 850-950°C.

[0017] Furthermore, the pre-firing heating rate is 30-50°C / h; the pre-firing time is 8-24h; the pre-firing temperature is 400-600°C; the roasting heating rate is 30-50°C / h; the roasting temperature is 900-1000°C; and the roasting time is 8-24h.

[0018] Among them, the pre-burning process is to remove water and carbon dioxide in the raw material powder in preparation for subsequent calcination. The preheating heating rate can be arbitrarily selected within the range of 30 to 50°C / h, such as 30°C / h, 35°C / h, 40°C / h, 45°C / h, and 50°C / h.

[0019] Furthermore, the barium-containing compound is barium oxide, barium hydroxide, barium halide, barium carbonate, barium nitrate, barium sulfate, barium acetate or barium oxalate with a purity of not less than 99.9%; the scandium-containing compound is scandium oxide, scandium hydroxide, scandium halide or scandium nitrate with a purity of not less than 99.9%; the boron-containing compound is boric acid or boron oxide with a purity of not less than 99.9%.

[0020] Furthermore, the molar ratio of barium:scandium:boron in the raw material powder is 3:2:4.

[0021] Furthermore, the flux includes one or more of sodium fluoride, sodium oxide, barium fluoride, barium chloride, sodium chloride, lithium fluoride, lithium oxide, boron oxide or boric acid; and the molar ratio of the raw material powder to the flux is 0.8-1.2:3-7.

[0022] In the preparation process, the method first obtains polycrystalline Ba3Sc2(BO3)4 powder, and then prepares single crystal Ba3Sc2(BO3)4 crystal through a flux method.

[0023] To achieve the third object, the present invention further provides a method for preparing the ultraviolet birefringent crystal, comprising the following steps:

[0024] The barium-containing compound, the scandium-containing compound and the boron-containing compound are mixed into raw material powder according to a certain proportion, mixed with a flux, heated to a molten state in a platinum crucible, and cooled to room temperature to obtain a crystal growth material;

[0025] The crystal growth material is placed in a crystal growth furnace, heated to a molten state, stirred, cooled to the crystal growth temperature in one stage, and then a seed rod is placed in it. Then, a second stage of cooling is performed while the seed rod is rotated. After the crystal growth is completed, the seed rod is lifted and the crystal attached to the seed rod is lifted off the liquid surface. The Ba3Sc2(BO3)4 crystal is obtained by cooling to room temperature in three stages.

[0026] Furthermore, the barium-containing compound is barium oxide, barium hydroxide, barium halide, barium carbonate, barium nitrate, barium sulfate, barium acetate or barium oxalate with a purity of not less than 99.9%; the scandium-containing compound is scandium oxide, scandium hydroxide, scandium halide or scandium nitrate with a purity of not less than 99.9%; the boron-containing compound is boric acid or boron oxide with a purity of not less than 99.9%.

[0027] Furthermore, the molar ratio of barium:scandium:boron in the raw material powder is 3:2:4.

[0028] Furthermore, the flux includes one or more of sodium fluoride, sodium oxide, barium fluoride, barium chloride, sodium chloride, lithium fluoride, lithium oxide, boron oxide or boric acid; and the molar ratio of the raw material powder to the flux is 0.8-1.2:3-7.

[0029] Furthermore, the crystal growth temperature is 850-950°C; the second-stage cooling rate is 0.01-2°C / d; the rotation speed of the seed rod is 20-30rd / min; the crystal growth cycle is 10-30d; and the third-stage cooling rate is 5-15°C / h.

[0030] To achieve the fourth object, the present invention further provides a method for preparing the ultraviolet birefringent crystal, comprising the following steps:

[0031] The barium-containing compound, the scandium-containing compound and the boron-containing compound are mixed into raw material powder in a certain ratio, heated in a platinum crucible, pre-sintered, cooled to room temperature, ground, sintered, and cooled to obtain Ba3Sc2(BO3)4 powder;

[0032] Ba3Sc2(BO3)4 powder is mixed with a flux to obtain a crystal growth material, which is then placed in a crystal growth furnace, heated to a molten state, stirred, cooled to the crystal growth temperature in one stage, and then a seed rod is placed in it. Thereafter, a second stage of cooling is performed while the seed rod is rotated. After the crystal growth is completed, the seed rod is lifted, and the crystal attached to the seed rod is lifted off the liquid surface. The Ba3Sc2(BO3)4 crystal is obtained by cooling to room temperature in three stages.

[0033] In the preparation process, the method first obtains polycrystalline Ba3Sc2(BO3)4 powder, and then prepares single crystal Ba3Sc2(BO3)4 crystal through a flux method.

[0034] Furthermore, the pre-firing heating rate is 30-50°C / h; the pre-firing time is 8-24h; the pre-firing temperature is 400-600°C; the roasting heating rate is 30-50°C / h; the roasting temperature is 900-1000°C; and the roasting time is 8-24h.

[0035] Among them, the pre-burning process is to remove water and carbon dioxide in the raw material powder in preparation for subsequent calcination. The preheating heating rate can be arbitrarily selected within the range of 30 to 50°C / h, such as 30°C / h, 35°C / h, 40°C / h, 45°C / h, and 50°C / h.

[0036] Furthermore, the barium-containing compound is barium oxide, barium hydroxide, barium halide, barium carbonate, barium nitrate, barium sulfate, barium acetate or barium oxalate with a purity of not less than 99.9%; the scandium-containing compound is scandium oxide, scandium hydroxide, scandium halide or scandium nitrate with a purity of not less than 99.9%; the boron-containing compound is boric acid or boron oxide with a purity of not less than 99.9%; preferably, the molar ratio of barium:scandium:boron in the raw material powder is 3:2:4.

[0037] Furthermore, the flux includes but is not limited to one or more of sodium fluoride, sodium oxide, barium fluoride, barium chloride, sodium chloride, lithium fluoride, lithium oxide, boron oxide or boric acid; and the molar ratio of the raw material powder to the flux is 0.8-1.2:3-7.

[0038] Furthermore, the crystal growth temperature is 850-950°C; the second-stage cooling rate is 0.01-2°C / d; the rotation speed of the seed rod is 20-30rd / min; the crystal growth cycle is 10-30d; and the third-stage cooling rate is 5-15°C / h.

[0039] To achieve the fifth object, the present invention provides a use of the ultraviolet birefringent crystal as described above in the preparation of an optical polarizer, a beam displacer, a circulator, an optical isolator or an optical modulator.

[0040] The beneficial effects of the present invention are as follows:

[0041] The present invention provides a Ba3Sc2(BO3)4 ultraviolet birefringent crystal, its preparation and application. The Ba3Sc2(BO3)4 ultraviolet birefringent crystal has a centrosymmetric structure, belongs to the trigonal system, has a space group of P-3m1, and has a unit cell parameter of α=90°, β=90°, γ=120°, Z=1, Room-temperature transmission spectra show that the UV birefringent crystal has a wide transmission range (0.2 to 3.5 μm), a transmittance exceeding 70%, a short UV cutoff edge (198 nm), and a large birefringence index (Δn = 0.145). Furthermore, the crystal exhibits stable physical and chemical properties, good mechanical properties, resistance to deliquesce, and ease of cutting, polishing, and storage, making it promising for widespread application in the field of UV birefringent optical materials. The UV birefringent crystal is prepared using a flux method, which is simple to operate, uses readily available raw materials, and is easily achievable under the appropriate preparation conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] Figure 1 The powder X-ray diffraction spectrum (PXRD) of the scandium barium borate compound powder prepared in Example 1 of the present invention is shown.

[0044] Figure 2 A schematic structural diagram of the barium scandium borate crystal prepared in Example 1 of the present invention is shown.

[0045] Figure 3 The figure shows the room temperature transmission spectrum of the barium scandium borate crystal prepared in Example 2 of the present invention.

[0046] Figure 4Schematic diagram of the optical system showing a scandium barium borate crystal used as a Wollaston prism optical device.

[0047] Figure 5 Schematic diagram of the optical system showing a scandium barium borate crystal used as a polarizing prism optical device. DETAILED DESCRIPTION

[0048] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0050] Example 1

[0051] This example is to prepare and test the single crystal data parameter sample of Ba3Sc2(BO3)4 crystal, and the preparation sample is about 2g:

[0052] 1.816 g BaCO3, 0.423 g Sc2O3 and 0.757 g H3BO3 were mixed in a mortar and ground thoroughly, then placed in a platinum crucible and placed in a muffle furnace; the temperature was raised to 500°C at a rate of 50°C / h for pre-calcination, and the mixture was stirred at a constant temperature for 12 hours before cooling. After cooling, the sample was taken out and ground and mixed again, and the mixture was placed in a muffle furnace and raised to 960°C at the same temperature rate for calcination, and stirred at a constant temperature for 12 hours. After cooling to room temperature, Ba3Sc2(BO3)4 powder was obtained;

[0053] Then put 2.112g of Ba3Sc2(BO3)4 polycrystalline powder and 0.886g of H3BO3 flux into a mortar and mix them. Grind them thoroughly to obtain crystal growth material. In a platinum crucible;

[0054] The crucible containing the mixed material was then placed in a crystal growth furnace and heated to 1150°C until it was completely melted. The temperature was then lowered at a rate of 1°C / hour to 750°C, and then to room temperature at a rate of 10°C / hour, yielding a colorless, flake-like single crystal. Structural analysis of the resulting crystal confirmed it to be the target Ba3Sc2(BO3)4 crystal.

[0055] Example 2

[0056] Weigh 296.01g BaCO3, 67.00g Sc2O3, 123.66g H3BO3 and 154.58g flux H3BO3 into a mortar and grind them together. The platinum crucible is transferred to a muffle furnace for melting to obtain a mixed melt, which is then cooled to room temperature to obtain a crystal growth material;

[0057] The crucible containing the crystal growth material is placed in a crystal growth furnace, heated to 1150°C, and stirred at a constant temperature for 24 hours to completely melt it; when the temperature is cooled to 934°C in the first stage, a seed rod is placed and extended into the melt; the temperature is cooled in the second stage at a rate of 0.5°C / d, while the seed rod is rotated at a speed of 20rd / min. After the crystal growth is completed (growth cycle: 28 days), the seed rod is lifted and the crystal attached to the seed rod is lifted off the liquid surface, and then the temperature is cooled to room temperature in the third stage at a rate of 10°C / h to obtain a Ba3Sc2(BO3)4 crystal with a size of 18mm×16mm×10mm.

[0058] Example 3

[0059] 269.1g BaCO3, 62.69g Sc2O3 and 123.66g H3BO3 were mixed in a mortar and ground thoroughly. The mixture was then placed in a platinum crucible and placed in a muffle furnace. The temperature was raised to 500°C at a rate of 50°C / h, held at this temperature for 12 hours, and then cooled. After cooling, the sample was removed and ground and mixed again. The sample was placed in a muffle furnace and heated to 960°C at the same rate and held at this temperature for 12 hours. After cooling, the scandium barium borate compound Ba3Sc2(BO3)4 was obtained.

[0060] 433.65g of Ba3Sc2(BO3)4 polycrystalline powder and 181.85g of flux H3BO3 were mixed and ground in a mortar. Melt in a platinum crucible to obtain a mixed melt, which is then cooled to room temperature to obtain a crystal growth material;

[0061] The crucible containing the crystal growth material is placed in a crystal growth furnace, heated to 1180°C, and stirred at a constant temperature for 24 hours to completely melt it; when the temperature is cooled to 920.5°C in the first stage, a seed rod is placed and inserted into the melt; the temperature is cooled in the second stage at a rate of 0.5°C / d, while the seed rod is rotated at a speed of 26rd / min. After the crystal growth is completed (the growth cycle is 26 days), the seed rod is lifted, and the crystal attached to the seed rod is lifted off the liquid surface, and then the temperature is cooled to room temperature in the third stage at a rate of 10°C / h to obtain a 16mm×14mm×10mm Ba3Sc2(BO3)4 crystal.

[0062] Experimental Example 1

[0063] The Ba3Sc2(BO3)4 powder obtained in Example 1 was subjected to powder X-ray diffraction test, and the results are shown in FIG. Figure 1 The obtained spectrum is basically consistent with the standard XRD spectrum, which is a polycrystalline powder, proving that the polycrystalline powder of the target object Ba3Sc2(BO3)4 has been prepared.

[0064] The Ba3Sc2(BO3)4 crystal prepared in Example 1 was then structurally characterized. The test conditions were: a Mercury CCD single crystal diffractometer, a Mo target, a Kα radiation source (λ = 0.07107 nm), and a test temperature of 293 K. The structure was elucidated using Shelxtl software. The resulting crystallographic data are shown in Table 1.

[0065] Table 1 is the crystallographic data of Ba3Sc2(BO3)4 crystal prepared in Example 1

[0066]

[0067] Experimental Example 2

[0068] The Ba3Sc2(BO3)4 crystal prepared in Example 2 was cut in a directional manner to obtain a prism device with a cross-sectional size of 4×4 mm; the light-transmitting surfaces at both ends of the crystal device were precisely polished and coated. Figure 4 As shown in the figure, when a light beam is incident perpendicularly on the end face of the prism, in prism 1, the o-ray and e-ray travel in the same direction at different speeds. When the light passes from prism 1 to prism 2, the optical axis rotates 90 degrees. The o-ray becomes the e-ray, propagating away from the normal, while the e-ray becomes the o-ray, propagating closer to the normal. After both beams enter the air, they propagate from a denser medium to a less dense medium, resulting in further separation of the two linearly polarized beams.

[0069] Experimental Example 3

[0070] The Ba3Sc2(BO3)4 crystal prepared in Example 2 was cut in a directional manner to obtain a prism device with a cross-sectional size of 4×4 mm; the light-transmitting surfaces at both ends of the crystal device were precisely polished and coated. Figure 5 As shown, a polarizing prism is made by bonding with Canada gum (or air gap). When a beam of light is incident perpendicular to the prism end face, neither the o-ray nor the e-ray is deflected in the first prism. The o-ray is totally reflected at the bonding surface and absorbed by the absorbing coating on the right-angled surface of the prism, while the e-ray is emitted from the second prism without deflection.

[0071] Experimental Example 4

[0072] The Ba3Sc2(BO3)4 crystal prepared in Example 2 was placed on an Agilent Cary 7000 UV-vis-NIR spectrometer to test the optical transmission curve in the range of 200nm to 2500nm; and placed on an Excalibur 3100 Fourier transform infrared spectrometer to test the optical transmission curve in the range of 2500nm to 15μm. Figure 3 From the spectral transmittance curve, it can be seen that Ba3Sc2(BO3)4 has a wide transmittance range (0.2-3.5 μm, transmittance above 70%), an ultraviolet cutoff edge of 198 nm, and theoretical calculation shows that Δn=0.145.

[0073] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. An ultraviolet birefringent crystal, characterized in that: The chemical formula is Ba3Sc2(BO3)4, which has a centrosymmetric structure, belongs to the trigonal crystal system, and has a space group of P- 3m1 , the unit cell parameters are a = 5.2959(4)Å, b = 5.2959(4)Å, c = 11.0602(10)Å, α = 90°, β = 90°, γ = 120°, Z = 1, V = 268.64(5)Å 3 .

2. A method for preparing an ultraviolet birefringent crystal according to claim 1, characterized in that: The steps include: The barium-containing compound, the scandium-containing compound and the boron-containing compound are mixed into raw material powder in proportion, heated in a platinum crucible, pre-sintered, cooled to room temperature, ground, sintered, and cooled to obtain Ba3Sc2(BO3)4 powder; Ba3Sc2(BO3)4 powder is mixed evenly with a flux to obtain a crystal growth material, the crystal growth material is placed in a crystal growth furnace, heated to a molten state, and first cooled to the crystal growth temperature. After the growth is completed, the crystal is raised to above the melt liquid surface, and then cooled to room temperature for a second time to obtain Ba3Sc2(BO3)4 crystal.

3. The preparation method according to claim 2, characterized in that The rate of the first cooling is 0.5-2°C / h, and the rate of the second cooling is 5-15°C.

4. A method for preparing an ultraviolet birefringent crystal according to claim 1, characterized in that: The steps include: The barium-containing compound, the scandium-containing compound and the boron-containing compound are mixed into raw material powder according to a certain proportion, mixed with a flux, heated to a molten state in a platinum crucible, and cooled to room temperature to obtain a crystal growth material; The crystal growth material is placed in a crystal growth furnace, heated to a molten state, stirred, cooled to the crystal growth temperature in one stage, and then a seed rod is placed in it. Then, a second stage of cooling is performed while the seed rod is rotated. After the crystal growth is completed, the seed rod is lifted and the crystal attached to the seed rod is lifted off the liquid surface. The Ba3Sc2(BO3)4 crystal is obtained by cooling to room temperature in three stages.

5. A method for preparing an ultraviolet birefringent crystal according to claim 1, characterized in that: The steps include: The barium-containing compound, the scandium-containing compound and the boron-containing compound are mixed into raw material powder in a certain ratio, heated in a platinum crucible, pre-sintered, cooled to room temperature, ground, sintered, and cooled to obtain Ba3Sc2(BO3)4 powder; Ba3Sc2(BO3)4 powder is mixed with a flux to obtain a crystal growth material, which is then placed in a crystal growth furnace, heated to a molten state, stirred, cooled to the crystal growth temperature in one stage, and then a seed rod is placed in it. Thereafter, a second stage of cooling is performed while the seed rod is rotated. After the crystal growth is completed, the seed rod is lifted, and the crystal attached to the seed rod is lifted off the liquid surface. The Ba3Sc2(BO3)4 crystal is obtained by cooling to room temperature in three stages.

6. The preparation method according to claim 2 or 5, characterized in that The heating rate of the pre-firing is 30~50℃ / h; the pre-firing time is 8~24h; the pre-firing temperature is 400~600℃; the heating rate of the roasting is 30~50℃ / h; the roasting temperature is 900~1000℃; and the roasting time is 8~24h.

7. The preparation method according to any one of claims 2 to 5, characterized in that The barium-containing compound is barium oxide, barium hydroxide, barium halide, barium carbonate, barium nitrate, barium sulfate, barium acetate or barium oxalate with a purity of not less than 99.9%; the scandium-containing compound is scandium oxide, scandium hydroxide, scandium halide or scandium nitrate with a purity of not less than 99.9%; the boron-containing compound is boric acid or boron oxide with a purity of not less than 99.9%.

8. The preparation method according to any one of claims 2 to 5, characterized in that The molar ratio of barium:scandium:boron in the raw material powder is 3:2:

4.

9. The preparation method according to any one of claims 2 to 5, characterized in that The flux includes one or more of sodium fluoride, sodium oxide, barium fluoride, barium chloride, sodium chloride, lithium fluoride, lithium oxide, boron oxide or boric acid; the molar ratio of the raw material powder to the flux is 0.8-1.2:3-7.

10. The preparation method according to any one of claims 4 to 5, characterized in that The crystal growth temperature is 850-950°C; the second-stage cooling rate is 0.01-2°C / d; the rotation speed of the seed rod is 20-30 rd / min; the crystal growth cycle is 10-30 days; and the third-stage cooling rate is 5-15°C / h.

11. Use of the ultraviolet birefringent crystal according to claim 1 in preparing an optical polarizer, a beam displacer, a circulator, an optical isolator or an optical modulator.

Images