Antiferroelectric electro-optic crystal and preparation method and application thereof

Abstract

The application discloses a kind of antiferroelectric electro-optic crystal and its preparation method and application, the chemical formula of the antiferroelectric electro-optic crystal is K3Ta x Nb 3‑x B2O 12 Wherein, x The value range of 0.15~0.6 is 0.15~0.6.The antiferroelectric electro-optic crystal of the application has the characteristics of wide transmission range, high transmittance and large electro-optic coefficient, with the optical transmittance of 350-2500nm wavelength range being greater than or equal to 80%, and the effective electro-optic coefficient being not less than 15.0pm / V@632.8nm.Compared with the same structure of potassium boron niobate crystal, the electro-optic coefficient of the KTNB antiferroelectric electro-optic crystal of the application is increased by about 5 times, with large polarization intensity (about 9 times of potassium boron niobate crystal) and smaller phase transition electric field (about half of potassium boron niobate crystal).Meanwhile, the KTNB antiferroelectric electro-optic crystal of the application has stable physical and chemical properties, thermal properties, is not easy to deliquesce, has good mechanical properties, is easy to process and other excellent characteristics.

Description

Technical Field

[0001] This invention belongs to the field of functional crystal materials, and relates to an antiferroelectric electro-optic crystal, its preparation method and application. Background Technology

[0002] The electro-optic effect refers to the phenomenon where the refractive index of a crystalline material changes with an applied electric field. Optical devices based on this effect, such as electro-optic switches, electro-optic modulators, and electro-optic deflectors, have been widely used in lasers, optical communications, and other fields. However, electro-optic crystals are subject to various limitations in practical applications, particularly the limitation imposed by crystal symmetry, which significantly hinders their application. With the rapid iteration of high-end optoelectronic equipment, the market demand for high-performance electro-optic crystals is becoming increasingly urgent, making the development of novel electro-optic crystals with excellent overall performance a current research hotspot.

[0003] Although many crystals exhibit electro-optic effects, practical crystals with excellent overall performance are few and far between. Currently, commonly used electro-optic crystals include barium metaborate, potassium titanyl phosphate, potassium dihydrogen phosphate, and lithium niobate. However, these electro-optic crystals all have shortcomings: for example, barium metaborate crystals have a small electro-optic coefficient, and it is difficult to grow high-quality, large-size crystals; potassium titanyl phosphate crystals grown by the molten salt method are prone to breakdown under pressure during electro-optic applications, thus easily producing gray marks; potassium dihydrogen phosphate crystals have a high half-wave voltage; and lithium niobate crystals have a low laser damage threshold. Therefore, there is an urgent need to develop an electro-optic crystal with excellent overall performance that is easy to grow into large-size bulk crystals. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an antiferroelectric electro-optic crystal with the chemical formula K3Ta. x Nb 3-x B2O 12 (KTNB), where, x The value range is 0.15~0.6, preferably 0.2~0.5, for example. x =0.2, 0.3, 0.4 or 0.5.

[0005] According to an embodiment of the present invention, the doping content of Ta doping element in the antiferroelectric electro-optic crystal is: Ta / Nb molar ratio = 1:4-1:19.

[0006] According to an embodiment of the present invention, the transmission range of the antiferroelectric electro-optic crystal is 332-2500 nm, for example, 1000 nm, 1500 nm, or 2000 nm.

[0007] According to an embodiment of the present invention, the maximum polarization intensity of the antiferroelectric electro-optic crystal is 5-12 μC / cm. 2 For example, 11.76 μC / cm2 .

[0008] According to an embodiment of the present invention, the antiferroelectric to ferroelectric phase transition electric field of the antiferroelectric electro-optic crystal is 5-15 kV / cm, for example, 10.45 kV / cm.

[0009] According to an embodiment of the present invention, the transparent antiferroelectric crystal is on the centimeter scale, and the crystal size is greater than 1 cm in any direction of the antiferroelectric electro-optic crystal.

[0010] According to an embodiment of the present invention, the antiferroelectric electro-optic crystal is grown using a flux method.

[0011] The present invention also provides a method for growing the above-mentioned antiferroelectric electro-optic crystal, specifically a flux method.

[0012] According to an embodiment of the present invention, the fluxing method specifically includes: a. KTNB raw material and flux are mixed and completely melted to obtain a high-temperature solution; b. Cool the high-temperature solution from step a until KTNB crystals precipitate, and use the precipitated KTNB crystals as seed crystals; c. Fix the seed crystal from step b onto the seed crystal rod and determine the supersaturation temperature point of the high-temperature solution; at the supersaturation temperature point, make the seed crystal contact the surface of the high-temperature solution, and after the seed crystal reaches the growth equilibrium point, cool it down (for example, at a rate of 3-5℃ / day) and keep the seed crystal rotating (for example, at a rate of 15-60 revolutions / minute) to carry out crystal growth. d. After a certain growth cycle, centimeter-sized KTNB crystals are obtained.

[0013] According to an embodiment of the present invention, the "supersaturation temperature point" refers to the temperature at which the solution reaches a supersaturated state (i.e., the solute content has exceeded the solubility limit under the current temperature and pressure conditions, but has not yet precipitated). A supersaturated solution at this temperature point is unstable; any slight disturbance (such as the introduction of crystal nuclei or a slight drop in temperature) will trigger rapid precipitation of the solute, causing the solution to return to a saturated state.

[0014] According to an embodiment of the invention, in step a, mixing and melting are carried out in a platinum crucible.

[0015] According to an embodiment of the present invention, in step a, the KTNB raw material includes potassium-containing compounds, niobium-containing compounds, tantalum-containing compounds, and boron-containing compounds.

[0016] According to an embodiment of the present invention, the molar ratio of K, Ta, Nb and B elements in the KTNB raw material is 3:(0.15~0.6):(2.85~2.4):2. For example, the molar ratio of K in potassium-containing compounds, Ta in tantalum-containing compounds, Nb in niobium-containing compounds and B in boron-containing compounds in the KTNB raw material is 3:0.15:2.85:2.

[0017] According to an embodiment of the present invention, in step a, the potassium-containing compound is at least one of K2CO3, K2O and KOH.

[0018] According to an embodiment of the present invention, in step a, the tantalum-containing compound is Ta2O5.

[0019] According to an embodiment of the present invention, in step a, the niobium-containing compound is Nb2O5.

[0020] According to an embodiment of the present invention, in step a, the boron-containing compound is at least one of B2O3 and H3BO3.

[0021] According to an embodiment of the present invention, the flux is selected from at least one potassium-containing compound and at least one boron-containing compound: preferably a mixture of at least one of K2CO3, K2O, KCl, KOH, and KF with at least one of B2O3 and H3BO3.

[0022] According to an embodiment of the present invention, the flux comprises a potassium compound and a boron compound, wherein the molar ratio of the potassium compound and the boron compound is 1:0.5-5, for example 1:1.46.

[0023] In some embodiments, the flux is a mixture of KF and B2O3, wherein the molar ratio of KF to B2O3 is 1:0.5-5, for example 1:0.5, 1:1, 1:2, 1:3, 1:4 or 1:5.

[0024] In some embodiments, the flux is a mixture of K2CO3, KF, B2O3 and H3BO3, with a molar ratio of K2CO3, KF, B2O3 and H3BO3 of 1:(0.1~1):(0.4~2):(0.1~1), for example 1:0.5:1.88:0.5.

[0025] For example, the flux is a mixture of K2CO3 and B2O3, wherein the molar ratio of K2CO3 to B2O3 is 1:0.5-5, for example 1:1.46.

[0026] For example, the flux is a mixture of K2CO3, KF and B2O3, wherein the molar ratio of K2CO3, KF and B2O3 is 1:(0.2~0.8):(1~2), for example 1:0.615:1.46.

[0027] According to an embodiment of the present invention, in step b, the seed crystal refers to a high-quality, transparent, and large-sized KTNB crystal. The preferred size of the seed crystal is (5-20) mm × (2-10) mm × (1-5) mm; for example, 10 mm × 6 mm × 3 mm, 14 mm × 5 mm × 2 mm, or 10 mm × 4 mm × 3 mm.

[0028] According to an embodiment of the present invention, in step c, the supersaturation temperature point refers to the supersaturation temperature point of the high-temperature solution determined by contacting the seed crystal with the high-temperature solution of step a and observing the melting and growth of the seed crystal.

[0029] According to an embodiment of the present invention, in step c, the supersaturation temperature point is 900-950℃, for example, 900℃, 910℃, 920℃, 930℃, 940℃ or 950℃.

[0030] According to an embodiment of the present invention, in step d, the growth cycle is 14-20 days, for example, 14 days, 15 days or 20 days.

[0031] According to an embodiment of the present invention, in step d, after the growth cycle is completed, the KTNB crystal can be cooled to room temperature at a cooling rate of 10-50℃ / hour.

[0032] The present invention also provides the use of the above-mentioned KTNB crystal as an electro-optic crystal, for example, the use of the potassium boroniobate electro-optic crystal in electro-optic switching, electro-optic modulators and electro-optic deflectors and other electro-optic devices.

[0033] The invention also provides an electro-optic device containing or prepared from the above-mentioned KTNB crystal.

[0034] According to an embodiment of the present invention, the electro-optic device is at least one of an electro-optic switch, an electro-optic modulator, and an electro-optic deflector.

[0035] The beneficial effects of this invention are: The KTNB antiferroelectric electro-optic crystal of this invention exhibits a light transmittance ≥80% in the wavelength range of 350-2500 nm and an effective electro-optic coefficient of not less than 15.0 pm / V@632.8 nm, characterized by a wide transmission range, high transmittance, and large electro-optic coefficient. Compared to the isomorphic potassium boroniobate crystal (effective electro-optic coefficient of 3.3 pm / V@632.8 nm), the electro-optic coefficient of the KTNB antiferroelectric electro-optic crystal of this invention is increased by approximately 5 times. This is attributed to the crystal's larger polarization intensity (approximately 9 times that of potassium boroniobate crystal) and smaller phase transition electric field (approximately half that of potassium boroniobate crystal). Furthermore, the KTNB antiferroelectric electro-optic crystal of this invention possesses stable physicochemical properties, thermal properties, is not hygroscopic, has good mechanical properties, and is easy to process, making it a high-performance electro-optic crystal.

[0036] This invention uses a flux method to grow KTNB electro-optic crystals. Crystals grown by this method are of high quality, transparent and free of inclusions, and are easy to grow and obtain large-size crystals.

[0037] The KTNB electro-optic crystal grown using the flux method of this invention can be used as an electro-optic element such as an electro-optic switch, electro-optic modulator, and electro-optic deflector after the crystallographic data of the crystal is oriented, the crystal blank is cut according to the required angle, thickness and cross-sectional size, and the light-transmitting surface of the crystal is polished. Attached Figure Description

[0038] Figure 1 A photograph of the KTNB antiferroelectric electro-optic crystal prepared in Example 1 of this invention; Figure 2 The powder X-ray diffraction pattern of the KTNB antiferroelectric electro-optic crystal prepared in Example 1 of this invention; Figure 3 The hysteresis loop of the KTNB antiferroelectric electro-optic crystal prepared in Example 2 of this invention; Figure 4 Photograph of the KTNB antiferroelectric electro-optic crystal prepared in Example 2 of this invention after processing for electro-optic testing; Figure 5 The image shows the electro-optic performance test results of the KTNB antiferroelectric electro-optic crystal prepared in Example 2 of this invention. Figure 6 This is a crystal image of the KTNB antiferroelectric electro-optic crystal prepared in Example 3 of the present invention, after processing and used for transmission testing. Figure 7 The transmission spectrum of the KTNB antiferroelectric electro-optic crystal prepared in Example 3 of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection of the present invention.

[0040] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0041] Example 1 The specific steps for growing KTNB antiferroelectric electro-optic crystals using the flux method are as follows: a. KTNB raw materials (K2CO3, Ta2O5, Nb2O5, B2O3 in a molar ratio of 3:0.15:2.85:2) and flux (including K2CO3, KF, and B2O3 in a molar ratio of 1:0.615:1.46) are mixed in a molar ratio of 1:5. 217.19 g of K2CO3, 16.57 g of Ta2O5, 189.39 g of Nb2O5, 117.48 g of B2O3, and 29.05 g of KF are weighed and thoroughly mixed. The mixture is then heated to 960°C in a platinum crucible to melt, yielding a high-temperature solution.

[0042] b. The high-temperature solution from step a is slowly cooled at 10°C per hour to precipitate KTNB antiferroelectric electro-optic crystals. High-quality KTNB antiferroelectric electro-optic crystals are selected as seed crystals with a size of 10 mm × 6 mm × 3 mm. High quality means no obvious inclusions or cracks, high transparency, and high mechanical strength, which can improve the quality of crystals grown by the top seed crystal method.

[0043] c. Fix the seed crystal selected in step b onto the seed crystal rod, and then place the seed crystal above the high-temperature solution in step a; the seed crystal and the high-temperature solution are in contact, and the supersaturation temperature point of the high-temperature solution is found by observing the melting and growth of the seed crystal, which is 910℃; at the supersaturation temperature point, the seed crystal is in contact with the liquid surface, and after the seed crystal reaches the growth equilibrium point (i.e., the critical point where the seed crystal neither melts nor grows), the temperature is lowered at a rate of 3℃ / day, while the seed crystal rod is kept rotating at a rate of 20 revolutions / minute to carry out crystal growth.

[0044] d. After 20 days, the KTNB antiferroelectric electro-optic crystal was extracted from the high-temperature solution at 850℃ and cooled to room temperature at a rate of 10℃ / hour to obtain centimeter-sized KTNB antiferroelectric electro-optic crystals. Figure 1 ).

[0045] Example 2 The specific steps for growing KTNB antiferroelectric electro-optic crystals using the flux method are as follows: a. KTNB raw materials (K2CO3, Ta2O5, Nb2O5, B2O3 in a molar ratio of 3:0.3:2.7:2) and flux (including KF and B2O3 in a molar ratio of 1:0.5) are mixed in a molar ratio of 1:6. 82.92 g K2CO3, 26.51 g Ta2O5, 143.54 g Nb2O5, 83.54 g B2O3, and 92.95 g KF are weighed and thoroughly mixed. The mixture is then heated to 950°C in a platinum crucible to melt, yielding a high-temperature solution.

[0046] b. The high-temperature solution from step a is slowly cooled at 9°C per hour to precipitate KTNB antiferroelectric electro-optic crystals. High-quality KTNB antiferroelectric electro-optic crystals are selected as seed crystals with a size of 14 mm × 5 mm × 2 mm. High quality means no obvious inclusions or cracks, high transparency, and high mechanical strength, which can improve the quality of crystals grown by the top seed crystal method.

[0047] c. Fix the seed crystal selected in step b onto the seed crystal rod, and then place the seed crystal above the high-temperature solution in step a; the seed crystal and the high-temperature solution are in contact, and the supersaturation temperature point of the high-temperature solution is found by observing the melting and growth of the seed crystal, which is 920℃; at the supersaturation temperature point, the seed crystal is in contact with the liquid surface, and after the seed crystal reaches the growth equilibrium point, the temperature is reduced at a rate of 4℃ / day, while the seed crystal rod is kept rotating at a rate of 30 revolutions / minute to carry out crystal growth.

[0048] d. After 14 days, the KTNB antiferroelectric electro-optic crystals grown in the high-temperature solution were extracted by cooling to 864℃ and then cooled to room temperature at a rate of 30℃ / hour to obtain centimeter-sized KTNB antiferroelectric electro-optic crystals.

[0049] Example 3 The specific steps for growing KTNB antiferroelectric electro-optic crystals using the flux method are as follows: a. KTNB raw materials (K2CO3, Ta2O5, Nb2O5, B2O3 in a molar ratio of 3:0.6:2.4:2) and flux (including K2CO3, KF, B2O3, and H3BO3 in a molar ratio of 1:0.5:1.88:0.5) are mixed in a molar ratio of 1:3.875. 172.75 g of K2CO3, 66.28 g of Ta2O5, 159.48 g of Nb2O5, 100.25 g of B2O3, 14.52 g of KF, and 15.45 g of H3BO3 are weighed and thoroughly mixed. The mixture is then heated to 970°C in a platinum crucible to melt, yielding a high-temperature solution.

[0050] b. The high-temperature solution from step a is slowly cooled at 10°C per hour to precipitate KTNB antiferroelectric electro-optic crystals. High-quality KTNB antiferroelectric electro-optic crystals are selected as seed crystals with a size of 10 mm × 4 mm × 3 mm. High quality means no obvious inclusions or cracks, high transparency, and high mechanical strength, which can improve the quality of crystals grown by the top seed crystal method.

[0051] c. Fix the seed crystal selected in step b onto the seed crystal rod, and then place the seed crystal above the high-temperature solution in step a; the seed crystal and the high-temperature solution are in contact, and the supersaturation temperature point of the high-temperature solution is found to be 930℃ by observing the melting and growth of the seed crystal; at the supersaturation temperature point, the seed crystal is in contact with the liquid surface, and after the seed crystal reaches the growth equilibrium point, the temperature is reduced at a rate of 5℃ / day, while the seed crystal rod is kept rotating at a rate of 60 rpm to carry out crystal growth.

[0052] d. After 15 days, the KTNB antiferroelectric electro-optic crystals grown in the high-temperature solution were removed from the solution at a temperature of 855℃ and cooled to room temperature at a rate of 40℃ / hour to obtain centimeter-sized KTNB antiferroelectric electro-optic crystals.

[0053] Example 4 The structure of the KTNB antiferroelectric electro-optic crystal prepared in Example 1 was characterized as follows: The KTNB antiferroelectric electro-optic crystal grown in Example 1 was cut into small pieces and ground into powder in a corundum mortar. The powder X-ray diffraction pattern of the KTNB antiferroelectric electro-optic crystal was determined using a Rigaku Miniflex 600 powder diffractometer (Japan) and monochromatic Cu... Kα X-ray source and ω and 2 ω The data collection method used was linked scanning, with a measurement temperature of 25℃. The test results are as follows: Figure 2 As shown.

[0054] Tests showed that the crystal structure of the KTNB antiferroelectric electro-optic crystal grown in Example 1 was consistent with the antiferroelectric potassium boroniobate crystal structure.

[0055] Example 5 Ferroelectric properties of the invented KTNB antiferroelectric electro-optic crystal were tested: The KTNB antiferroelectric electro-optic crystal grown in Example 2 was cut into slices with dimensions of X×Y×Z = 4.00 mm × 2.50 mm × 0.80 mm, where X is the

[100] direction, Y is the

[110] direction, and Z is the

[001] direction. Silver electrodes were coated on both sides of the Z-axis. The hysteresis loop of the crystal under different electric fields was tested using a TF2000 ferroelectric analyzer manufactured by AixACCT GmbH, Germany. Figure 3As shown, the KTNB antiferroelectric electro-optic crystal exhibits antiferroelectric characteristics: the antiferroelectric to ferroelectric phase transition electric field is 10.45 kV / cm, and the maximum polarization intensity is 11.76 μC / cm. 2 .

[0056] The phase transition electric field and maximum polarization intensity of the KTNB antiferroelectric electro-optic crystals obtained in other embodiments are listed in Table 1.

[0057] Table 1. Phase transition electric field and maximum polarization intensity of KTNB antiferroelectric electro-optic crystal.

[0058] Example 6 Electro-optic performance tests were conducted on the invented KTNB antiferroelectric electro-optic crystal: The KTNB antiferroelectric electro-optic crystal grown in Example 2 was cut into blocks with dimensions of X×Y×Z = 6.55 mm × 2.03 mm × 3.73 mm, where X is the

[100] direction, Y is the

[110] direction, and Z is the

[001] direction. The X sides were polished, and the Z sides were coated with silver paste, as shown below. Figure 4 As shown. Using the half-wave voltage method, an optical path platform was independently constructed. By gradually increasing the applied voltage, the voltage difference as the light intensity changed from minimum to maximum was recorded. This difference is the half-wave voltage. The electro-optic coefficient value of the crystal was then calculated, as shown below. Figure 5 As shown, the KTNB antiferroelectric electro-optic crystal has an electro-optic coefficient of 20.63 pm / V. Compared to the pure potassium boroniobate electro-optic crystal with an electro-optic coefficient of only 3.3 pm / V, the KTNB antiferroelectric electro-optic crystal obtained in Example 2 has an electro-optic coefficient that is 6.3 times higher than that of the undoped crystal, which is superior to commercially available crystals. β -BBO and KDP. The electro-optic properties of the KTNB antiferroelectric electro-optic crystals obtained in other embodiments are also listed in Table 2.

[0059] Table 2 Electro-optic properties of KTNB antiferroelectric electro-optic crystal

[0060] Example 7 Transmittance test of the KTNB antiferroelectric electro-optic crystal prepared in Example 3: The KTNB antiferroelectric electro-optic crystal grown in Example 3 was cut into slices with dimensions of X×Y×Z=5mm×4mm×1mm, where X is the

[100] direction, Y is the

[110] direction, and Z is the

[001] direction. Both sides of the Z-axis were polished, as shown below. Figure 6 As shown. The transmission spectrum was measured using a Perkin-Elmer Lambda-950 UV-Vis-NIR spectrophotometer, as shown. Figure 7As shown, the transmittance of this crystal in the 332-2500 nm range is ≥80%.

[0061] The exemplary embodiments of the present invention have been described above. However, the scope of protection of this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An antiferroelectric electro-optic crystal, characterized in that, The chemical formula of the antiferroelectric electro-optic crystal is K3Ta. x Nb 3-x B2O 12 (KTNB), where, x The value range is 0.15~0.6, preferably 0.2~0.

5.

2. The antiferroelectric electro-optic crystal as described in claim 1, characterized in that, The doping content of Ta doping element in the antiferroelectric electro-optic crystal is: Ta / Nb molar ratio = 1:4-1:19; And / or, the transmission range of the antiferroelectric electro-optic crystal is 332-2500 nm; And / or, the maximum polarization intensity of the antiferroelectric electro-optic crystal is 5-12 μC / cm. 2 ; And / or, the antiferroelectric to ferroelectric phase transition electric field of the antiferroelectric electro-optic crystal is 5-15 kV / cm; And / or, the transparent antiferroelectric crystal is on the centimeter scale, and the crystal size is greater than 1 cm in any direction of the antiferroelectric electro-optic crystal.

3. The method for growing the antiferroelectric electro-optic crystal according to claim 1 or 2, characterized in that, The method includes: a. KTNB raw material and flux are mixed and completely melted to obtain a high-temperature solution; b. Cool the high-temperature solution from step a until KTNB crystals precipitate, and use the precipitated KTNB crystals as seed crystals; c. Fix the seed crystal from step b onto the seed crystal rod and determine the supersaturation temperature point of the high-temperature solution; at the supersaturation temperature point, make the seed crystal contact the surface of the high-temperature solution, and after the seed crystal reaches the growth equilibrium point, cool it down and keep the seed crystal rotating to carry out crystal growth; d. After a certain growth cycle, centimeter-sized KTNB crystals are obtained.

4. The method as described in claim 3, characterized in that, In step a, the KTNB raw material includes potassium-containing compounds, niobium-containing compounds, tantalum-containing compounds, and boron-containing compounds; And / or, the molar ratio of K, Ta, Nb and B in the KTNB raw material is 3:(0.15~0.6):(2.85~2.4):2; And / or, in step a, the potassium-containing compound is at least one of K2CO3, K2O and KOH; And / or, the tantalum-containing compound is Ta2O5; And / or, the niobium-containing compound is Nb2O5; And / or, the boron-containing compound is at least one of B2O3 and H3BO3.

5. The method as described in claim 3 or 4, characterized in that, The flux is selected from at least one potassium-containing compound and at least one boron-containing compound: preferably a mixture of at least one of K2CO3, K2O, KCl, KOH, and KF with at least one of B2O3 and H3BO3.

6. The method as described in claim 5, characterized in that, The flux comprises potassium compounds and boron compounds, wherein the molar ratio of potassium compounds to boron compounds is 1:0.5-5; And / or, the flux is a mixture of KF and B2O3, wherein the molar ratio of KF to B2O3 is 1:0.5-5; And / or, the flux is a mixture of K2CO3, KF, B2O3 and H3BO3, wherein the molar ratio of K2CO3, KF, B2O3 and H3BO3 is 1:(0.1~1):(0.4~2):(0.1~1); And / or, the flux is a mixture of K2CO3 and B2O3, wherein the molar ratio of K2CO3 to B2O3 is 1:0.5-5; And / or, the flux is a mixture of K2CO3, KF and B2O3, wherein the molar ratio of K2CO3, KF and B2O3 is 1:(0.2~0.8):(1~2).

7. The method according to any one of claims 3-6, characterized in that, In step c, the supersaturation temperature is 900-950℃.

8. The method according to any one of claims 3-7, characterized in that, In step d, the growth cycle is 14-20 days; And / or, in step d, after the growth cycle is completed, the KTNB crystal can be cooled to room temperature at a cooling rate of 10-50℃ / hour.

9. The use of the KTNB crystal according to any one of claims 1-2 as an electro-optic crystal, for example, the use of the potassium boroniobate electro-optic crystal in electro-optic switching, electro-optic modulators and electro-optic deflectors and other electro-optic devices.

10. An electro-optic device comprising or prepared from the KTNB crystal according to any one of claims 1-2.

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