Preparation methods and applications of cubic phase barium strontium niobate electro-optic crystals

Abstract

This invention belongs to the field of nonlinear artificial crystal material preparation, and provides a method for preparing cubic phase barium strontium niobate electro-optic crystals and their applications. The Fe of this invention... 3+ Ni 2+ :Sr x Ba 1‑x Nb₂O₆ crystals belong to the cubic crystal system, in which Fe 3+ Ni 2+ As a doping ion, Fe 3+ The doping concentration is 0.03%wt to 0.09%wt, Ni 2+ The doping concentration is 0.8% wt to 1.0% wt. The preparation method includes: mixing and pressing barium source, strontium source, niobium source, iron salt, and nickel salt to obtain a crystal; subjecting the crystal to two pre-sintering processes to obtain an Fe-containing material. 3+ Ni 2+ Polycrystalline material; the Fe-containing material 3+ Ni 2+ The polycrystalline material is grown by pulling in an inert atmosphere and then annealed to obtain the crystal. By using ion doping technology, the Curie temperature of the crystal can be controlled to near room temperature, which can effectively improve the secondary electro-optic properties of the crystal and broaden its application range.

Description

Technical Field

[0001] This invention belongs to the field of nonlinear artificial crystal material preparation, and specifically relates to the preparation and application of an electro-optic crystal material with secondary electro-optic effect. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Electro-optic crystal materials, under the influence of an applied voltage, can modulate the intensity, phase, and propagation direction of light, making them core materials in important electro-optic devices such as electro-optic modulators, electro-optic switches, and electro-optic deflectors. Based on the relationship between the refractive index change of the electro-optic crystal and the applied electric field strength, the electro-optic effect can be divided into linear electro-optic effect (Polkhausen effect) and secondary electro-optic effect (Kerr effect). The linear electro-optic effect is more pronounced than the secondary electro-optic effect in most crystals; therefore, linear electro-optic modulators are often used in practical applications to modulate light waves. Commonly used linear electro-optic crystal materials include DKDP, ADP, LN, and LT. However, linear electro-optic crystal materials typically exhibit birefringence, which places strict requirements on the incident angle. When the beam deviates from the normal direction of the incident plane, the modulation efficiency decreases significantly, resulting in a relatively small field of view when these materials are used as bulk electro-optic modulators, limiting their application in certain specialized fields (such as three-dimensional lidar scanning imaging in aerospace).

[0004] Strontium barium niobate crystal (Sr x Ba 1-x Nb₂O₆ (SBN) is a high-performance, multifunctional crystal with excellent electro-optic and photorefractive properties. Its optical properties can be tuned by adjusting its Sr / Ba composition. SBN crystals with a composition of x = 0.61 can achieve iso-solid-liquid growth, easily yielding high-quality, large-size crystals. This composition has a Curie temperature of 83℃, exhibits a tetragonal phase near room temperature, and achieves a linear electro-optic coefficient of 1400 pm / V, which is 10 to 100 times that of commonly used electro-optic materials like lithium niobate crystals. When the crystal temperature exceeds its Curie point, it exhibits a cubic phase structure, with a second-order electro-optic coefficient reaching the level of 10⁻¹⁵ m² / V². Therefore, cubic SBN crystals possess both excellent electro-optic properties and a large field of view, making their bulk electro-optic modulation devices particularly suitable for free-space optical modulation applications.

[0005] However, since the Curie temperature of SBN crystal with a composition of 0.61 is 83℃, the secondary electro-optic properties of cubic SBN crystal must be utilized above the Curie point, which limits its application. Although the Curie point can be lowered by adjusting the Sr / Ba composition, this will increase the difficulty of crystal growth and introduce growth streaks. If the Curie temperature can be adjusted to near room temperature without reducing the electro-optic properties of the crystal, the application range of the crystal will be greatly expanded.

[0006] Patent CN105195130B discloses a strontium barium niobate system photocatalyst, but it does not possess a secondary electro-optic effect. Summary of the Invention

[0007] Cubic SBN crystals possess excellent secondary electro-optic properties, but their applications are limited by their high operating temperature. This invention addresses this issue by providing a method for preparing cubic barium strontium niobate electro-optic crystals. Through ion doping technology, the Curie temperature of the crystal can be controlled to near room temperature, while effectively improving the secondary electro-optic properties of the crystal and broadening its application range.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] Fe 3+ Ni 2+ :Sr x Ba 1-x Nb₂O₆ crystals belong to the cubic crystal system, in which Fe 3+ Ni 2+ As a doping ion, Fe 3+ The doping concentration is 0.03%wt to 0.09%wt, Ni 2+ The doping concentration is 0.8%wt to 1.0%wt.

[0010] In a first aspect, the present invention provides a method for preparing a cubic phase barium strontium niobate electro-optic crystal, the specific preparation method comprising:

[0011] Barium source, strontium source, niobium source, iron salt, and nickel salt are mixed and pressed to obtain crystal material;

[0012] The crystal material is pre-fired twice to obtain Fe-containing material. 3+ Ni 2+ Polycrystalline materials;

[0013] The Fe-containing 3+ Ni 2+ The polycrystalline material is grown by pulling in an inert atmosphere and then annealed to obtain the desired product.

[0014] After the first pre-firing, the crystal material needs to be re-ground before the second pre-firing.

[0015] Fe 3+ Ni 2+ :Sr x Ba 1-x Nb₂O₆ crystals belong to the cubic crystal system. The crystals were grown in a nitrogen atmosphere using an iridium pot. After obtaining the crystals, they were thermally annealed in an oxygen environment to obtain cubic barium strontium niobate electro-optic crystals.

[0016] The specific implementation involves uniformly mixing the raw materials in a mixer, then pressing them in a press, and finally burning them in a muffle furnace. The resulting polycrystalline material is then used to grow barium strontium niobate electro-optic crystals via the Czochralski method. During the growth of the barium strontium niobate crystal, the seed crystal is positioned at a distance from the center of the temperature field, and the crystal growth environment is in a nitrogen atmosphere. In addition, Fe2O3 and NiO are doped into the growth material to further alter its crystal composition and structure, thereby changing some of its properties. The material is then cooled and thermally annealed in an oxygen environment to prepare a cubic phase barium strontium niobate electro-optic crystal.

[0017] In some embodiments, the strontium source is SrCO3 and the barium source is BaCO3; the molar ratio of SrCO3 to BaCO3 is 0.4-0.8:0.6-0.2.

[0018] In some embodiments, the niobium source is Nb2O5, and the molar ratio of the total molar amount of SrCO3 and BaCO3 to that of Nb2O5 is 1.0 to 1.1:1.0.

[0019] In some embodiments, the iron salt is Fe2O3, Fe 3+ The concentration is 0.03%wt to 0.09%wt.

[0020] In some embodiments, the nickel salt is NiO, Ni 2+ The concentration is 0.4%wt to 1.0%wt.

[0021] In some embodiments, the first firing temperature is 900℃~950℃ and the firing time is 780~800min. The second firing temperature is controlled at 1100℃~1150℃ and the firing time is 840~850min.

[0022] In some embodiments, the crystal growth temperature is 1480–1530°C;

[0023] In some embodiments, the inert atmosphere is nitrogen, and the pressure range is 0.09. <P<0.1Mpa;

[0024] In some embodiments, the lifting speed is 0.5 to 10 mm / h, and the required crystal rotation speed is 5 to 40 rpm;

[0025] In some embodiments, the crystal cooling rate is 15°C to 20°C / hour.

[0026] In some embodiments, the annealing temperature is 1000–1100°C, and the annealing is carried out in an oxygen environment.

[0027] A second aspect of the present invention provides a cubic phase barium strontium niobate electro-optic crystal prepared by the above-described method, wherein the crystal has the chemical formula Fe. 3+ Ni 2+ :Sr x Ba 1-x Nb2O6.

[0028] A third aspect of the present invention provides the application of the above-described cubic phase barium strontium niobate electro-optic crystal in the fabrication of electro-optic devices, which exhibit a secondary photoelectric effect at room temperature.

[0029] Beneficial effects of the present invention

[0030] (1) This invention uses Fe 3+ Ion doping technology can adjust the Curie point of a crystal to near room temperature without changing the Sr / Ba ratio in the raw materials. This solves the problem that the Curie point cannot be adjusted to near room temperature by simply changing the Sr / Ba ratio, and avoids the crystal growth streaks caused by controlling the Curie point through Sr / Ba composition.

[0031] (2) This invention uses Ni 2+ Ion doping technology increases the secondary electro-optic coefficient of cubic SBN crystals by 3 to 5 times, effectively enhancing the electro-optic performance of the crystals.

[0032] (3) This invention utilizes Fe 3+ Ni 2+ The co-doping technique with two ions expands the application of the electro-optic properties of SBN crystals from the original tetragonal phase to the cubic phase, and from applications based on linear electro-optic properties to applications based on secondary electro-optic properties. Bulk electro-optic modulation devices based on the secondary electro-optic effect of cubic phase SBN crystals have the advantages of high modulation efficiency and large field of view, and are expected to be widely used in the field of free space light modulation.

[0033] (4) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0035] Figure 1 It is the cubic phase barium strontium niobate electro-optic crystal grown as described in this invention;

[0036] Figure 2 The Fe doping described in this invention 3+ Curie temperature comparison chart of barium strontium niobate;

[0037] Figure 3 The Ni-doped material described in this invention 2+ Comparison of secondary electro-optic coefficients of barium strontium niobate;

[0038] Figure 4 This is an extinction ratio diagram of barium strontium niobate and lithium niobate in an application example of the present invention. Detailed Implementation

[0039] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0041] Example 1

[0042] 0.05wt% Fe was grown. 2+ and 0.5wt% Ni 2+ Fe 2+ Ni 2+ :Sr x Ba 1-x Cubic phase barium strontium niobate electro-optic crystal of Nb2O6.

[0043] SrCO3, BaCO3 and Nb2O5 with a purity of 4N were selected as raw materials and prepared into powder in a molar ratio of 0.61:0.39:1, and then doped with 0.05wt% Fe2O3 and 0.5wt% NiO. After being mixed for 24 hours in a mixer, the mixture was pressed into blocks using a press and placed in a platinum crucible. It underwent two sintering processes. The first sintering was performed in a muffle furnace at 900℃ for 780 minutes to obtain barium strontium niobate polycrystalline material. After the first sintering, the material was ground into powder using zirconium oxide to ensure thorough mixing. The second sintering was then performed in a muffle furnace at 1100℃ for 840 minutes to obtain the final barium strontium niobate polycrystalline material. The reacted polycrystalline material was then placed in an iridium pot and grown in a Czochralski furnace using the Czochralski method in a 0.1 MPa nitrogen atmosphere. The growth temperature was 1500℃, the crystal rotation speed was 20 rpm, the crystal lifting speed was 0.5 mm / h, the crystal cooling rate was 15℃ / h, and the annealing temperature in an oxygen environment was 1100℃, resulting in a 25×20×25 mm crystal. 3 The cubic phase barium strontium niobate electro-optic crystal, its grown morphology is as follows Figure 1 As shown.

[0044] In this embodiment, Fe is also included. 3+ Ni 2+ Comparing the performance of crystals grown after doping the system with two different ions (0.05 wt% Fe₂O₃ and 0.5 wt% NiO) with that of crystals without any doping, the performance of the crystals grown with Fe₂O₃ is significantly better. 3+ Afterwards, as Figure 2 As shown, its Curie temperature decreased significantly, dropping to near room temperature, but its dielectric properties were not affected; doping with Ni... 2+ Afterwards, as Figure 3 As shown, its secondary electro-optic coefficient has been greatly improved, which makes it possible to apply the secondary electro-optic effect of crystals.

[0045] Example 2

[0046] 0.03wt% Fe was grown. 2+ and 0.4wt% Ni 2+ Fe 2+ Ni 2+ :Sr x Ba 1-x Cubic phase barium strontium niobate electro-optic crystal of Nb2O6.

[0047] SrCO3, BaCO3, and Nb2O5 with a purity of 4N were selected as raw materials and prepared into powder in a molar ratio of 0.75:0.25:1. 0.03wt% Fe2O3 and 0.4wt% NiO were also added. After mixing for 24 hours in a mixer, the mixture was pressed into blocks using a press and placed in a platinum crucible. The mixture underwent two firing processes. The first firing was performed in a muffle furnace at 900℃ for 780 minutes to obtain polycrystalline barium strontium niobate. After the first firing, the material was ground into powder using zirconium oxide to ensure thorough mixing. The reaction was then carried out in a muffle furnace at 1100℃ for 840 min to obtain the final barium strontium niobate polycrystalline material. The reacted polycrystalline material was then placed in an iridium pot and grown in a Czochralski furnace using the Czochralski method under a 0.2 MPa nitrogen atmosphere. The growth temperature was 1480℃, the crystal rotation speed was 30 rpm, the crystal lifting speed was 1 mm / h, the crystal cooling rate was 18℃ / h, and the annealing temperature in an oxygen environment was 1000℃, resulting in a 20×23×24 mm crystal. 3 Cubic phase barium strontium niobate electro-optic crystal.

[0048] Example 3

[0049] 0.09wt% Fe was grown. 2+ and 1.0wt%Ni 2+ Fe 2+ Ni 2+ :Sr x Ba 1-x Cubic phase barium strontium niobate electro-optic crystal of Nb2O6.

[0050] SrCO3, BaCO3, and Nb2O5 with a purity of 4N were selected as raw materials and prepared into powder in a molar ratio of 0.8:0.2:1. 0.09 wt% Fe2O3 and 1.0 wt% NiO were also added. After mixing for 24 hours in a mixer, the mixture was pressed into blocks using a press and placed in a platinum crucible. The mixture underwent two firing processes. The first firing was performed in a muffle furnace at 900℃ for 780 min to obtain polycrystalline barium strontium niobate. After the first firing, the material was ground into powder using zirconium oxide to ensure thorough mixing. The reaction was carried out a second time in a muffle furnace at 1100℃ for 840 min to obtain the final barium strontium niobate polycrystalline material. Then, the reacted polycrystalline material was placed in an iridium pot and grown in a Czochralski furnace using the Czochralski method in a 0.09 MPa nitrogen atmosphere. The growth temperature was 1510℃, the crystal rotation speed was 35 rpm, the crystal lifting speed was 3 mm / h, the crystal cooling rate was 20℃ / h, and the annealing temperature in an oxygen environment was 1080℃, resulting in a 27×22×24 mm crystal. 3 Cubic phase barium strontium niobate electro-optic crystal.

[0051] Application Example 1

[0052] SBN crystals (Fe) grown using Example 1 2+ Ni 2+ :Sr x Ba 1-x Nb₂O₆ was fabricated into a bulk electro-optic modulation element with a pair of apertures of 1.2 mm × 1.2 mm and a transmission length of 5 mm. Based on the refractive index ellipsoid equation, the change in induced refractive index when incident light enters the crystal at angles of 0–40° was calculated using the coordinate transformation method. Furthermore, based on the relationship between induced refractive index and phase difference, and between phase difference and extinction ratio, the extinction ratios of potassium tantalate and lithium niobate at different incident angles were calculated. Figure 4 Since cubic SBN does not exhibit natural birefringence, its extinction ratio decreases much more slowly than that of lithium niobate as the incident angle increases. This allows it to achieve efficient electro-optic modulation over a larger receiving field of view. Based on the principles of electro-optic modulation and photoelectric mixing, calculations show that when the incident angle is 15°, the mixing efficiency of barium strontium niobate crystal decreases from 50% to approximately 32%, while the field of view of lithium niobate is only 2°. This demonstrates that electro-optic modulation devices designed based on the secondary electro-optic effect of barium strontium niobate can achieve a larger field of view.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a cubic phase barium strontium niobate electro-optic crystal, characterized in that, include: Barium source, strontium source, niobium source, iron salt, and nickel salt are mixed and pressed to obtain crystal material; The crystal material is pre-fired twice to obtain Fe-containing material. 3+ Ni 2+ Polycrystalline materials; The Fe-containing 3+ Ni 2+ The polycrystalline material is grown by pulling in an inert atmosphere and then annealed to obtain the desired product. After the first pre-firing is completed, the crystal material needs to be re-ground before the second pre-firing is carried out. The chemical formula of the crystal is Fe. 3+ Ni 2+ Sr x Ba 1-x Nb2O6.

2. The method for preparing the cubic phase barium strontium niobate electro-optic crystal as described in claim 1, characterized in that, The strontium source is SrCO3, and the barium source is BaCO3; the molar ratio of SrCO3 to BaCO3 is 0.4~0.8:0.6~0.

2.

3. The method for preparing the cubic phase barium strontium niobate electro-optic crystal as described in claim 1, characterized in that, The niobium source is Nb2O5, and the total molar amount of SrCO3 and BaCO3 to the molar ratio of Nb2O5 is 1.0~1.1:1.

0.

4. The method for preparing the cubic phase barium strontium niobate electro-optic crystal as described in claim 1, characterized in that, The iron salt is Fe2O3, Fe 3+ The concentration is 0.03%wt~0.09%wt.

5. The method for preparing the cubic phase barium strontium niobate electro-optic crystal as described in claim 1, characterized in that, The nickel salt is NiO, Ni 2+ The concentration is 0.4%wt~1.0%wt.

6. The method for preparing the cubic phase barium strontium niobate electro-optic crystal as described in claim 1, characterized in that, The first firing temperature is 900℃~950℃ and the firing time is 780~800min. The second firing temperature is 1100℃~1150℃ and the firing time is 840~850min.

7. The method for preparing the cubic phase barium strontium niobate electro-optic crystal as described in claim 1, characterized in that, The crystal growth temperature is 1480~1530℃; Alternatively, the inert atmosphere is nitrogen, with a pressure range of 0.

09. <P<0.1Mpa; Alternatively, the lifting speed is 0.5~10 mm / h, and the required crystal rotation speed is 5~40 rpm; Alternatively, the cooling rate of the crystal is 15℃~20℃ / hour.

8. The method for preparing the cubic phase barium strontium niobate electro-optic crystal as described in claim 1, characterized in that, The annealing temperature is 1000~1100℃, and it is carried out in an oxygen environment.

9. The cubic phase barium strontium niobate electro-optic crystal prepared by the method according to any one of claims 1-8, characterized in that, The chemical formula of the crystal is Fe. 3+ Ni 2+ Sr x Ba 1-x Nb2O6.

10. The application of the cubic phase barium strontium niobate electro-optic crystal according to claim 9 in the fabrication of electro-optic devices, characterized in that, The electro-optical device exhibits a secondary photoelectric effect at room temperature.

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