Compound sodium vanadous selenite and compound sodium vanadous selenite birefringent crystal and preparation method and use

Abstract

This invention relates to a compound sodium vanadium selenite and a sodium vanadium selenite optical crystal, as well as their preparation methods and uses. The compound has the chemical formula NaVSeO5 and a molecular weight of 232.89, and is prepared using a vacuum encapsulation method. The crystal has the chemical formula NaVSeO5 and a molecular weight of 232.89. The crystal belongs to the monoclinic crystal system and has a space group of [space group missing]. C 2 / c The unit cell parameters are a =18.234(3)Å, b= 3.8381(6)Å, c= 12.416(2)Å, α =90°, β =112.421(7)°, γ = 0.5 90°, V=803.2(2)Å 3 Z=8. The crystal is grown using the sealed molten salt method, the high-temperature melt method, or the vacuum tube sealing method. At a wavelength of 1064 nm, the crystal has a birefringence Δn=0.12, good chemical stability, moderate mechanical hardness, and is easy to cut, polish, process, and store. It is insoluble in water and does not deliquesce, making it suitable for fabricating optical communication components or various polarizing prisms, phase delay devices, and electro-optic modulation devices, such as Glan prisms, polarization beam splitters, compensators, optical isolators, circulators, and optical modulators. It plays an important role in the fields of optics and communications.

Description

Technical Field

[0001] This invention relates to compounds with the chemical formula NaVSeO5, NaVSeO5 birefringent crystals, methods for preparing the crystals, and their uses. Background Technology

[0002] Birefringence is one of the important properties of light propagating in optically inhomogeneous crystal media. The fundamental reason for this phenomenon is the anisotropy of the crystal material, which can be explained by the transverse wave nature of light. When light propagates in an optically inhomogeneous medium (such as crystals other than cubic systems), except in a few special directions (along the optical axis), its vibrational characteristics change, decomposing into two polarized beams with mutually perpendicular electric field vector vibrations, different propagation speeds, and unequal refractive indices. This phenomenon is called birefringence, and such crystals are called birefringent crystals. One of the beams obeys the general law of refraction and is called the ordinary ray (o-ray), whose refractive index is denoted by n. o This indicates that another beam does not follow the general law of refraction, called the extraordinary ray (e-ray), and its refractive index is expressed in n. e This indicates that the properties of birefringent crystals can be used to obtain linearly polarized light and achieve beam displacement, making birefringent crystals a key material for fabricating optical components such as optical isolators, circulators, beam shifters, optical polarizers, and optical modulators.

[0003] Commonly used birefringent materials include calcite, rutile, LiNbO3, YVO4, and α-BaB2O4 crystals. However, calcite crystals mainly exist in natural forms, making artificial synthesis difficult; they are generally small in size, have high impurity content, cannot meet the requirements of large-size optical polarizing elements, and are prone to dissociation, making processing difficult and resulting in low crystal utilization. Rutile also mainly exists in natural forms, making artificial synthesis difficult, and it is small in size, hard, and difficult to process. LiNbO3 crystals are easy to obtain in large sizes, but its birefringence is too low. YVO4 is a high-performance artificial birefringent crystal, but due to its high melting point, it must be grown using an iridium crucible in a weak oxygen atmosphere, which leads to iridium valence changes during growth, making it difficult to obtain high-quality crystals. α-BaB2O4 is prone to cracking during crystal growth due to solid-state phase transitions. Therefore, it is essential to find a birefringent crystal that is easy to grow, has stable performance, and possesses a high birefringence. Summary of the Invention

[0004] The purpose of this invention is to provide a sodium vanadium selenite compound with the chemical formula NaVSeO5 and a molecular weight of 232.89, which is prepared by vacuum encapsulation.

[0005] Another objective of this invention is to provide a sodium vanadium selenite birefringent crystal with the chemical formula NaVSeO5, a molecular weight of 232.89, belonging to the monoclinic crystal system, space group C2 / c, and cell parameters of [missing information]. α=90°, β=112.421(7)°, γ=90°, Z = 8.

[0006] Another objective of this invention is to provide a method for preparing sodium vanadium selenite birefringent crystals, which uses a sealed molten salt method, a high-temperature melt growth method, or a vacuum encapsulation method to grow the crystals.

[0007] Another object of the present invention is to provide an application of sodium vanadium selenite optical birefringent crystal, which is used to manufacture optical communication components, namely optical isolators, circulators, beam shifters, optical polarizers and optical modulators, and is particularly suitable for manufacturing polarizing prisms, phase delay devices and electro-optic modulators for various purposes.

[0008] The present invention discloses a compound, sodium vanadium selenite, with the chemical formula NaVSeO5 and a molecular weight of 232.89, which is prepared by vacuum encapsulation.

[0009] The compound sodium vanadium selenite is prepared by vacuum encapsulation, and the specific operation is carried out according to the following steps:

[0010] Mix the Na-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Na∶V∶Se=1∶1∶1, and fill the mixture into a quartz tube. Evacuate the quartz tube to a vacuum level of 10. -3 Pa, after being sealed at high temperature, is placed in a muffle furnace and heated to 200-550℃ at a rate of 5-10℃ / h, and held at the temperature for 24-100 hours to obtain compound NaVSeO5. The Na-containing compound is Na2CO3, Na2O, Na2SO4, NaNO3 or NaVO3, the V-containing compound is V2O5 or NaVO3 and the Se-containing compound is SeO2 or H2SeO4.

[0011] A sodium vanadium selenite birefringent crystal with the chemical formula NaVSeO5 and a molecular weight of 232.89, belongs to the monoclinic crystal system, space group C2 / c, and has the following cell parameters. α=90°, β=112.421(7)°, γ=90°, Z = 8.

[0012] The method for preparing the sodium vanadium selenite birefringent crystal employs a sealed molten salt method, a high-temperature melt growth method, or a vacuum encapsulation method to grow the crystal, wherein:

[0013] The preparation of NaVSeO5 birefringent crystals by the sealed molten salt method is carried out according to the following steps:

[0014] a. Mix the Na-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Na∶V∶Se=1∶1∶1, transfer the mixture into the lining of a high-pressure hydrothermal reactor, and seal the high-pressure hydrothermal reactor. The Na-containing compound is Na2CO3, Na2O, Na2SO4, NaNO3, or NaVO3, the V-containing compound is V2O5 or NaVO3, and the Se-containing compound is SeO2 or H2SeO4.

[0015] b. Heat to 300-550℃ at a rate of 5-10℃ / h, hold at the temperature for 2-3 days, and then slowly cool to room temperature at a rate of 1-5℃ / d. Open the high-pressure hydrothermal reactor to obtain NaVSeO5 birefringent crystals.

[0016] The preparation of NaVSeO5 birefringent crystals by the high-temperature melt method is carried out according to the following steps:

[0017] a. Mix the Na-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Na∶V∶Se=1∶1∶1, and fill the mixture into a quartz tube. Evacuate the quartz tube to a vacuum degree of 10. -3 The mixture is sealed at high temperature and placed in a muffle furnace. The temperature is increased to 200-550℃ at a rate of 5-10℃ / h and held at the temperature for 24-100 hours to obtain compound NaVSeO5. The Na-containing compound is Na2CO3, Na2O, Na2SO4, NaNO3 or NaVO3, the V-containing compound is V2O5 or NaVO3, and the Se-containing compound is SeO2 or H2SeO4.

[0018] b. The compound NaVSeO5 obtained in step a is placed into an alumina crucible, heated to 450-600℃, and kept at that temperature for 5-100 hours to obtain a mixed melt.

[0019] c. Preparation of seed crystals: The mixed melt obtained in step b is placed in a single crystal furnace and slowly reduced to 220°C at a rate of 0.1-2°C / h, and then rapidly reduced to room temperature at a rate of 5-10°C / h to obtain NaVSeO5 seed crystals.

[0020] d. Crystal growth: Fix the seed crystal obtained in step c on the seed crystal rod, lower the seed crystal from above the mixed melt obtained in step b, apply a crystal rotation of 2-20 rpm through the crystal growth controller, and cool down at a rate of 0.1-3℃ / h. After the crystal growth stops, NaVSeO5 birefringent crystal is obtained.

[0021] The vacuum encapsulation method for preparing NaVSeO5 birefringent crystals is carried out according to the following steps:

[0022] a. Mix the Na-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Na∶V∶Se=1∶1∶1, and fill the mixture into a quartz tube. Evacuate the quartz tube to a vacuum degree of 10. -3 The mixture is sealed at high temperature and placed in a muffle furnace. The temperature is increased to 200-550℃ at a rate of 5-10℃ / h and held at the temperature for 24-100 hours to obtain compound NaVSeO5. The Na-containing compound is Na2CO3, Na2O, Na2SO4, NaNO3 or NaVO3, the V-containing compound is V2O5 or NaVO3, and the Se-containing compound is SeO2 or H2SeO4.

[0023] b. The NaVSeO5 polycrystalline powder obtained in step a is loaded into a quartz tube, sealed at high temperature, and placed in a muffle furnace. The temperature is raised to 450-600℃ and held for 50-100 hours. Then, the temperature is lowered to 220℃ at a rate of 0.1-3℃ / h, and then rapidly lowered to room temperature at a rate of 5-10℃ / h to obtain NaVSeO5 birefringent crystal.

[0024] The sodium vanadium selenite birefringent crystal is used in the fabrication of optical communication components, namely optical isolators, circulators, beam shifters, optical polarizers, or optical modulators.

[0025] The sodium vanadium selenite optical crystal is used in the fabrication of various polarizing prisms, namely phase delay devices and electro-optic modulation devices.

[0026] The sodium vanadium selenite birefringent crystal obtained by the method described in this invention has moderate mechanical hardness and is easy to cut, polish, process, and store. It is insoluble in water, non-hygroscopic, and stable in air, making it suitable for manufacturing optical communication components, such as optical isolators, circulators, beam shifters, optical polarizers, and optical modulators. It is particularly suitable for manufacturing polarizing prisms, phase delay devices, and electro-optic modulators for various applications. Attached Figure Description

[0027] Figure 1 This is the X-ray diffraction pattern of the NaVSeO5 powder of this invention;

[0028] Figure 2 This is a photograph of the NaVSeO5 crystal of the present invention;

[0029] Figure 3 This is a crystal structure diagram of NaVSeO5 according to the present invention;

[0030] Figure 4 This is a birefringence curve of NaVSeO5 according to the present invention;

[0031] Figure 5This is a schematic diagram of the wedge-shaped birefringent crystal polarization beam splitter of the present invention, where 1 is the incident light, 2 is the o-ray, 3 is the e-ray, 4 is the optical axis, and 5 is the NaVSeO5 crystal.

[0032] Figure 6 This is a schematic diagram of the optical isolator of the present invention, where 6 represents the light transmission direction;

[0033] Figure 7 This is a schematic diagram of the beam shifter of the present invention, wherein 1 is the incident light, 2 is the o-light, 3 is the e-light NaVSeO5 crystal, 4 is the optical axis, 5 is the NaVSeO5 crystal, 6 is the light transmission direction, and 7 is the optical axis plane. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments. It should be noted that the following embodiments are not intended to limit the scope of protection of the present invention, and any improvements made based on the present invention do not depart from the spirit of the present invention. Unless otherwise specified, the raw materials or equipment used in the present invention are commercially available.

[0035] Example 1

[0036] According to the reaction formula: Na₂SO₄ + V₂O₅ + 2SeO₂ → 2NaVSeO₅ + SO₃↑, the specific steps for preparing compound NaVSeO₅ using the vacuum encapsulation method are as follows:

[0037] a. According to the proportions in the reaction formula, mix Na2SO4, V2O5 and SeO2 evenly, grind them in a mortar for 15 minutes to obtain a mixture;

[0038] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. - 3 After Pa, high-temperature sealing is performed;

[0039] c. Place the quartz tube from step b into a muffle furnace and heat it to 400°C at a rate of 10°C / hour. Maintain the temperature for 25 hours, then turn off the muffle furnace after cooling to room temperature. After cooling, remove the sample to obtain the compound NaVSeO5.

[0040] Example 2

[0041] According to the reaction formula: 2NaOH + V₂O₅ + 2SeO₂ → 2NaVSeO₅ + H₂O↑, the specific steps for preparing compound NaVSeO₅ using the vacuum encapsulation method are as follows:

[0042] a. According to the proportions in the reaction formula, mix NaOH, V2O5 and SeO2 evenly and place them in a mortar. Grind for 15 minutes to obtain a mixture.

[0043] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. - 3 After Pa, high-temperature sealing is performed;

[0044] c. Place the quartz tube from step b into a muffle furnace, heat it to 350°C at a rate of 5°C / h, hold it at that temperature for 72 days, and then cool it to room temperature to obtain the compound NaVSeO5.

[0045] Example 3

[0046] According to the reaction formula: 4NaNO3 + 2V2O5 + 4SeO2 → 4NaVSeO5 + 4NO2↑ + O2↑, the specific operation for preparing compound NaVSeO5 using the vacuum encapsulation method is as follows:

[0047] a. According to the proportions in the reaction formula, mix NaNO3, V2O5 and SeO2 evenly, grind them in a mortar for 13 minutes to obtain a mixture;

[0048] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. - 3 After Pa, high-temperature sealing is performed;

[0049] c. Place the quartz tube from step b into a muffle furnace and heat it to 330°C at a rate of 7°C / h; hold it at this temperature for 72 hours, and then cool it to room temperature to obtain the compound NaVSeO5.

[0050] Example 4:

[0051] According to the reaction formula: 4Na₂O + 2V₂O₅ + 4SeO₂ → 4NaVSeO₅ + O₂↑, the specific steps for preparing compound NaVSeO₅ using the vacuum encapsulation method are as follows:

[0052] a. According to the proportions in the reaction formula, mix Na2O, V2O5 and SeO2 evenly and place them in a mortar. Grind for 20 minutes to obtain a mixture.

[0053] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. - 3 After Pa, high-temperature sealing is performed;

[0054] c. Place the quartz tube from step b into a muffle furnace, heat it to 350°C at a rate of 6°C / h, hold it at that temperature for 40 hours, and then cool it to room temperature to obtain the compound NaVSeO5.

[0055] Example 5

[0056] According to the reaction formula: NaVO3 + SeO2 → NaVSeO5, the specific steps for preparing compound NaVSeO5 using the vacuum encapsulation method are as follows:

[0057] a. According to the ratio in the reaction formula, mix NaVO3 and SeO2 evenly and place them in a mortar. Grind for 20 minutes to obtain a mixture.

[0058] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. - 3 After Pa, high-temperature sealing is performed;

[0059] c. Place the quartz tube from step b into a muffle furnace, heat it to 400°C at a rate of 10°C / h, hold it at that temperature for 72 hours, and then cool it to room temperature to obtain the compound NaVSeO5.

[0060] Example 6

[0061] According to the reaction formula: Na₂CO₃ + V₂O₅ + 2SeO₂ → 2NaVSeO₅ + CO₂↑, the specific steps for preparing compound NaVSeO₅ using the vacuum encapsulation method are as follows:

[0062] a. According to the proportions in the reaction formula, mix Na2CO3, V2O5 and SeO2 evenly and place them in a mortar. Grind for 20 minutes to obtain a mixture.

[0063] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. - 3 After Pa, high-temperature sealing is performed;

[0064] c. Place the quartz tube from step b into a muffle furnace, heat it to 390°C at a rate of 10°C / h, hold it at that temperature for 25 hours, and then cool it to room temperature to obtain the compound NaVSeO5.

[0065] Example 7

[0066] According to the reaction formula: Na₂CO₃ + V₂O₅ + 2H₂SeO₄ → 2NaVSeO₅ + 2H₂O↑ + CO₂↑ + O₂↑, the specific operation for preparing compound NaVSeO₅ using the vacuum encapsulation method is as follows:

[0067] a. According to the proportions in the reaction formula, mix Na2CO3, V2O5 and H2SeO4 evenly and place them in a mortar. Grind for 20 minutes to obtain a mixture.

[0068] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. -3 After Pa, high-temperature sealing is performed;

[0069] c. Place the quartz tube from step b into a muffle furnace, heat it to 380°C at a rate of 10°C / h, hold it at that temperature for 30 hours, and then cool it to room temperature to obtain the compound NaVSeO5.

[0070] Example 8

[0071] According to the reaction formula: 4NaNO3 + 2V2O5 + 4H2SeO4 → 4NaVSeO5 + 4H2O↑ + 4NO3↑ + O2↑, the specific operation for preparing compound NaVSeO5 using the vacuum encapsulation method is as follows:

[0072] a. According to the proportions in the reaction formula, mix NaNO3, V2O5 and H2SeO4 evenly and place them in a mortar. Grind for 20 minutes to obtain a mixture.

[0073] b. Place the mixture from step a into a Ф40mm quartz tube, and evacuate the quartz tube to a vacuum level of 10. - 3 After Pa, high-temperature sealing is performed;

[0074] c. Place the quartz tube from step b into a muffle furnace, heat it to 360°C at a rate of 10°C / h, hold it at that temperature for 50 hours, and then cool it to room temperature to obtain the compound NaVSeO5.

[0075] Example 9

[0076] NaVSeO5 birefringent crystals were grown using the sealed molten salt method, and the specific operation was carried out according to the following steps:

[0077] The pure phase of compound NaVSeO5 obtained in Example 1 was transferred into the lining of a high-pressure hydrothermal reactor, and the high-pressure hydrothermal reactor was sealed.

[0078] The high-pressure hydrothermal reactor was placed in an oven and heated to 550℃ at a rate of 5℃ / h, held at that temperature for 24 hours, and then cooled to room temperature at a rate of 2℃ / d. The high-pressure hydrothermal reactor was then opened, and a NaVSeO5 birefringent crystal with a diameter of Ф6mm×0.2mm×0.3mm was obtained.

[0079] Example 10

[0080] NaVSeO5 birefringent crystals were grown using the sealed molten salt method, and the specific operation was carried out according to the following steps:

[0081] The pure phase of compound NaVSeO5 obtained in Example 2 was transferred into the lining of a high-pressure hydrothermal reactor, and the high-pressure hydrothermal reactor was sealed.

[0082] The high-pressure hydrothermal reactor was placed in an oven and heated to 600℃ at a rate of 6℃ / h. The furnace temperature was then controlled at 600℃ and held for 44 hours. The temperature was then lowered to room temperature at a rate of 5℃ / d. The high-pressure hydrothermal reactor was then opened, and a NaVSeO5 birefringent crystal with a diameter of Ф5mm×0.2mm×0.3mm was obtained.

[0083] Example 11

[0084] NaVSeO5 birefringent crystals were grown using the sealed molten salt method, and the specific operation was carried out according to the following steps:

[0085] The pure phase of compound NaVSeO5 obtained in Example 3 was transferred into the lining of a high-pressure hydrothermal reactor, and the high-pressure hydrothermal reactor was sealed.

[0086] The high-pressure hydrothermal reactor was placed in an oven and heated to 470°C at a rate of 10°C / h. The furnace temperature was then controlled at 470°C and held for 24 hours. The temperature was then lowered to room temperature at a rate of 2°C / d. The high-pressure hydrothermal reactor was then opened, and a NaVSeO5 birefringent crystal with a diameter of Ф5mm×0.5mm×0.4mm was obtained.

[0087] Example 12

[0088] NaVSeO5 birefringent crystals were grown using a high-temperature melt method, and the specific operation was carried out according to the following steps:

[0089] The pure phase of compound NaVSeO5 obtained in Example 4 was placed in an alumina crucible, heated to 550°C, and kept at that temperature for 50 hours to obtain a mixed melt.

[0090] Preparation of seed crystals: The obtained mixed melt is placed in a single crystal furnace and cooled to 220°C at a rate of 0.1°C / h, and then rapidly cooled to room temperature at a rate of 5°C / h to obtain NaVSeO5 seed crystals;

[0091] Crystal growth: The obtained seed crystal is fixed on the seed crystal rod and lowered from above the prepared mixed melt. The crystal rotation is applied at 2 rpm through the crystal growth controller, and the temperature is reduced at a rate of 0.1℃ / h. After the crystal growth stops, a NaVSeO5 birefringent crystal with dimensions of Ф3mm×0.4mm×1mm is obtained.

[0092] Example 13

[0093] NaVSeO5 birefringent crystals were grown using a high-temperature melt method, and the specific operation was carried out according to the following steps:

[0094] The pure phase of compound NaVSeO5 obtained in Example 5 was placed in an alumina crucible, heated to 450°C, and held at that temperature for 100 hours to obtain a mixed melt.

[0095] Preparation of seed crystals: The obtained mixed melt is placed in a single crystal furnace and cooled to 220°C at a rate of 1°C / h, and then rapidly cooled to room temperature at a rate of 8°C / h to obtain NaVSeO5 seed crystals.

[0096] Crystal growth: The obtained seed crystal is fixed on the seed crystal rod and lowered from above the prepared mixed melt. The crystal rotation is applied at 20 rpm through the crystal growth controller, and the temperature is reduced at a rate of 3℃ / h. After the crystal growth stops, a NaVSeO5 birefringent crystal with dimensions of Ф4mm×0.2mm×1mm is obtained.

[0097] Example 14

[0098] NaVSeO5 birefringent crystals were grown using a high-temperature melt method, and the specific operation was carried out according to the following steps:

[0099] The pure phase of compound NaVSeO5 obtained in Example 5 was placed in an alumina crucible, heated to 600°C, and held at that temperature for 5 hours to obtain a mixed melt.

[0100] Preparation of seed crystals: The obtained mixed melt is placed in a single crystal furnace and slowly cooled to 220°C at a rate of 2°C / h, and then rapidly cooled to room temperature at a rate of 10°C / h to obtain NaVSeO5 seed crystals.

[0101] Crystal growth: The seed crystal is fixed on the seed crystal rod and lowered from above the prepared mixed melt. The crystal rotation is applied at 10 rpm through the crystal growth controller, and the temperature is reduced at a rate of 1℃ / h. After the crystal growth stops, a NaVSeO5 birefringent crystal with dimensions of Ф5mm×0.3mm×0.4mm is obtained.

[0102] Example 15

[0103] NaVSeO5 birefringent crystals were grown using a vacuum encapsulation method, and the specific operation was carried out according to the following steps:

[0104] The pure phase of compound NaVSeO5 obtained in Example 6 was placed into a 40mm quartz tube, and the quartz tube was evacuated to a vacuum level of 10. -3 After being sealed at high temperature, the sample was placed in a muffle furnace and heated to 500℃. It was kept at this temperature for 72 hours, then cooled to 200℃ at a rate of 1℃ / h, and then rapidly cooled to room temperature at a rate of 8℃ / h. This yielded a NaVSeO5 birefringent crystal with dimensions of Ф3mm×0.5mm×1mm.

[0105] Example 16

[0106] NaVSeO5 birefringent crystals were grown using a vacuum encapsulation method, and the specific operation was carried out according to the following steps:

[0107] The pure phase of compound NaVSeO5 obtained in Example 7 was placed into a 40mm quartz tube, and the quartz tube was evacuated to a vacuum level of 10. -3 After Pa, the sample was sealed at high temperature and placed in a furnace. The temperature was raised to 450℃ and held for 100 hours. The temperature was then lowered to 200℃ at a rate of 0.1℃ / h and then rapidly cooled to room temperature at a rate of 10℃ / h, resulting in a NaVSeO5 birefringent crystal with dimensions of Ф4mm×0.3mm×0.8mm.

[0108] Example 17

[0109] NaVSeO5 birefringent crystals were grown using a vacuum encapsulation method, and the specific operation was carried out according to the following steps:

[0110] The pure phase of compound NaVSeO5 obtained in Example 8 was placed into a 40mm quartz tube, and the quartz tube was evacuated to a vacuum level of 10. -3 After Pa, the sample is sealed at high temperature and placed in a muffle furnace. The temperature is raised to 600℃ and held for 50 hours. Then, it is cooled to 220℃ at a rate of 3℃ / h and then rapidly cooled to room temperature at a rate of 5℃ / h. This yields a NaVSeO5 birefringent crystal with dimensions of Ф4mm×0.5mm×2mm.

[0111] Example 18

[0112] Any NaVSeO5 birefringent crystal obtained in Examples 9-17 was used to prepare a wedge-shaped birefringent crystal polarization beam splitter (e.g. Figure 4 As shown), a wedge-shaped birefringent crystal, with its optical axis oriented as follows. Figure 4 As shown, a beam of natural light can be split into two linearly polarized beams after passing through a crystal. The greater the birefringence, the farther the two beams can be separated, which facilitates the separation of the beams.

[0113] Example 19

[0114] Any NaVSeO5 crystal obtained in Examples 9-17 can be used to prepare an optical isolator. By placing a Faraday rotator with its incident beam polarization plane rotated by 45° between a pair of birefringent crystal deflectors placed at 45° angles to each other, an optical isolator can be constructed. This isolator only allows forward-propagating beams to pass through the system while blocking backward-propagating beams. Figure 6 'a' indicates that the incident light beam can pass through. Figure 6 b indicates that the reflected light is blocked.

[0115] Example 20

[0116] Any NaVSeO5 crystal obtained in Examples 9-17 was used to fabricate a beam shifter. A birefringent crystal was fabricated such that its optical axis plane forms an angle θ with the edge (e.g., ...). Figure 7As shown in a), when natural light is incident perpendicularly, it can be split into two beams of linearly polarized light with mutually perpendicular vibration directions (as shown in a). Figure 7 (As shown in b), these are the o-ray and e-ray, respectively. The greater the birefringence, the farther the two beams can be separated, which facilitates beam separation.

Claims

1. A sodium vanadium selenite birefringent crystal, characterized in that... The crystal has the chemical formula NaVSeO5, a molecular weight of 232.89, belongs to the monoclinic crystal system, and its space group is [space group number missing]. C 2 / c The unit cell parameters are a =18.234(3)Å, b= 3.8381(6)Å, c= 12.416(2)Å, α =90°, β =112.421(7)°, γ= 90°, V=803.2(2)Å 3 Z=8.

2. The method for preparing sodium vanadium selenite birefringent crystal according to claim 1, characterized in that... Crystals are grown using the sealed molten salt method, high-temperature melt fermentation, or vacuum encapsulation method, wherein: The preparation of NaVSeO5 birefringent crystals by the sealed molten salt method is carried out according to the following steps: a. Mix the Na-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Na∶V∶Se=1∶1∶1, transfer the mixture into the lining of a high-pressure hydrothermal reactor, and seal the high-pressure hydrothermal reactor. The Na-containing compound is Na2CO3, Na2O, Na2SO4, NaNO3, or NaVO3, the V-containing compound is V2O5 or NaVO3, and the Se-containing compound is SeO2 or H2SeO4. b. Heat to 300-550℃ at a rate of 5-10℃ / h, hold at the temperature for 2-3 days, and then slowly cool to room temperature at a rate of 1-5℃ / d. Open the high-pressure hydrothermal reactor to obtain NaVSeO5 birefringent crystals. The preparation of NaVSeO5 birefringent crystals by the high-temperature melt method is carried out according to the following steps: a. Mix the Na-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Na∶V∶Se=1∶1∶1, and fill the mixture into a quartz tube. Evacuate the quartz tube to a vacuum degree of 10. -3 The mixture is sealed at high temperature and placed in a muffle furnace. The temperature is increased to 200-550℃ at a rate of 5-10℃ / h and held at the temperature for 24-100 hours to obtain compound NaVSeO5. The Na-containing compound is Na2CO3, Na2O, Na2SO4, NaNO3 or NaVO3, the V-containing compound is V2O5 or NaVO3, and the Se-containing compound is SeO2 or H2SeO4. b. The compound NaVSeO5 obtained in step a is placed into an alumina crucible, heated to 450-600℃, and kept at that temperature for 5-100 hours to obtain a mixed melt. c. Preparation of seed crystals: The mixed melt obtained in step b is placed in a single crystal furnace and slowly reduced to 220°C at a rate of 0.1-2°C / h, and then rapidly reduced to room temperature at a rate of 5-10°C / h to obtain NaVSeO5 seed crystals. d. Crystal growth: Fix the seed crystal obtained in step c on the seed crystal rod, lower the seed crystal from above the mixed melt obtained in step b, apply a crystal rotation of 2-20 rpm through the crystal growth controller, and cool down at a rate of 0.1-3℃ / h. After the crystal growth stops, NaVSeO5 birefringent crystal is obtained. The vacuum encapsulation method for preparing NaVSeO5 birefringent crystals is carried out according to the following steps: a. Mix the Na-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Na∶V∶Se=1∶1∶1, and fill the mixture into a quartz tube. Evacuate the quartz tube to a vacuum degree of 10. -3 The mixture is sealed at high temperature and placed in a muffle furnace. The temperature is increased to 200-550℃ at a rate of 5-10℃ / h and held at the temperature for 24-100 hours to obtain compound NaVSeO5. The Na-containing compound is Na2CO3, Na2O, Na2SO4, NaNO3 or NaVO3, the V-containing compound is V2O5 or NaVO3, and the Se-containing compound is SeO2 or H2SeO4. b. The NaVSeO5 polycrystalline powder obtained in step a is loaded into a quartz tube, sealed at high temperature, and placed in a muffle furnace. The temperature is raised to 450-600℃ and held for 50-100 hours. Then, the temperature is lowered to 220℃ at a rate of 0.1-3℃ / h, and then rapidly lowered to room temperature at a rate of 5-10℃ / h to obtain NaVSeO5 birefringent crystal.

3. The use of the sodium vanadium selenite birefringent crystal according to claim 1 in the preparation of optical communication elements, namely optical isolators, circulators, beam shifters, optical polarizers or optical modulators.

4. The use according to claim 3, characterized in that... The sodium vanadium selenite birefringent crystal is used in the fabrication of various polarizing prisms, namely phase delay devices and electro-optic modulation devices.

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