Vanadous selenite lithium compound and vanadous selenite lithium birefringent crystal, and preparation method and use thereof

Abstract

The present application relates to a compound vanadium lithium selenite and vanadium lithium selenite birefringent crystal and preparation method and use, the chemical formula of the compound is LiV3Se2O 12 , the molecular weight is 509.68, is made by vacuum packaging method, the chemical formula of the crystal is LiV3Se2O 12 , the crystal belongs to triclinic system, and space group cell parameters are α=91.80 (4) °, β=93.15 (4) °, γ=106.24 (4) °. Z=2.At wavelength 546nm its birefringence Δn=0.5, the light transmission band 0.5 μm to 7 μm.Prepared by chemical vapor deposition method, high temperature melt method or crucible descending method, the size of LiV3Se2O 12 Birefringent crystal obtained by the method is centimeter level, moderate mechanical hardness, easy to cut, polish, process and preserve, insoluble in water, not deliquescent, stable in air;It is suitable for making optical communication components or polarizing prism of various purposes, and these devices utilize the refractive index characteristics of the crystal, especially the larger birefringence.

Description

TECHNICAL FIELD

[0001] The present application relates to a compound vanadium lithium selenite and a vanadium lithium selenite birefringent crystal and a preparation method and use. BACKGROUND

[0002] Birefringence is one of the important characteristics of light propagation in optically anisotropic medium crystals. When light propagates in an optically anisotropic medium (such as a crystal other than cubic system), except for a special direction (along the optical axis), the vibration characteristics of the light will change, and the light will be decomposed into two polarized lights with perpendicular vibration directions and different propagation speeds and refractive indices. This phenomenon is called birefringence, and such a crystal is called a birefringent crystal. One of the two lights follows the general refraction law and is called ordinary light (o light), and its refractive index is represented by n o . The other light does not follow the general refraction law and is called extraordinary light (e light), and its refractive index is represented by n e . The characteristics of birefringent crystals can be used to obtain linearly polarized light and to realize displacement of a light beam, etc. Thus, birefringent crystals become key materials for manufacturing optical elements such as optical isolators, circulators, optical beam displacers, optical polarizers, and optical modulators.

[0003] Commonly used birefringent materials mainly include calcite, rutile, LiNbO3, YVO4, and α-BaB2O4 crystals. However, calcite crystals mainly exist in a natural form, and it is difficult to artificially synthesize them. The crystals have a small size, a high impurity content, and cannot meet the requirements of large-size optical polarizing elements. In addition, the crystals are easy to dissociate and difficult to process, and the utilization rate of the crystals is low. Rutile also mainly exists in a natural form, and it is difficult to artificially synthesize and has a small size and a large hardness, which makes it difficult to process. LiNbO3 crystals can easily obtain large-size crystals, but have a too small birefringence. YVO4 is a kind of artificial birefringent crystal with good performance. However, because YVO4 has a high melting point, it must be grown by using an iridium crucible and in a weak oxygen atmosphere, and thus there is a problem of valence change of iridium elements during growth, and it is not easy to obtain high-quality crystals. α-BaB2O4 is easy to crack during crystal growth because of a solid phase transition. Therefore, it is necessary to find a birefringent crystal that is easy to grow, has stable performance, and has a large birefringence. SUMMARY

[0004] The present application aims to provide a vanadium lithium selenite compound, which has a chemical formula of LiV3Se2O 12 and a molecular weight of 509.68 and is prepared by using a vacuum packaging method.

[0005] Another object of the present application is to provide a vanadium lithium selenite birefringent crystal, which has a chemical formula of LiV3Se2O 12 and belongs to a triclinic crystal system and has a unit cell parameter of α = 91.80(4)°, β = 93.15(4)°, γ = 106.24(4)°,

[0006] Another object of the present application is to provide a preparation method of the vanadium lithium selenite birefringent crystal, which is prepared by chemical vapor deposition method, high temperature melt method or crucible lowering method.

[0007] Still another object of the present application is to provide a use of the vanadium lithium selenite birefringent crystal, which is used to make optical communication elements, i.e. optical isolators, circulators, optical beam displacers, optical polarizers and optical modulators. It is particularly suitable for making polarizing prisms, phase delay devices and electro-optical modulator devices for various purposes.

[0008] The vanadium lithium selenite compound has a chemical formula of LiV3Se2O 12 , a molecular weight of 509.68 and is prepared by vacuum packaging method.

[0009] The vanadium lithium selenite birefringent crystal has a chemical formula of LiV3Se2O 12 , belongs to triclinic crystal system, space group The cell parameters are α = 91.80(4)°, β = 93.15(4)°, γ = 106.24(4)°, a molecular weight of 509.68 and is prepared by chemical vapor deposition method, high temperature melt method or crucible lowering method.

[0010] The preparation method of the vanadium lithium selenite birefringent crystal is prepared by chemical vapor deposition method, high temperature melt method or crucible lowering method:

[0011] The chemical vapor deposition method for preparing the LiV3Se2O 12 birefringent crystal is specifically performed as follows:

[0012] a. A Li-containing compound, a V-containing compound and a Se-containing compound are mixed uniformly according to a molar ratio of Li:V:Se = 1:3:2, and are loaded into a quartz tube. The quartz tube is vacuumized, and after the vacuum degree reaches 10 -3 Pa, it is fused and sealed. The sealed quartz tube is placed in a muffle furnace, and is heated to 250-450°C at a rate of 10-30°C / h, and is kept at constant temperature for 12 hours. Then, it is cooled to room temperature at a cooling rate of 10-20°C / h, and after cooling, the quartz tube is opened to obtain the LiV3Se2O 12 compound. The Li-containing compound is Li2SO4, LiOH, LiNO3, Li2O, Li2CO3 or LiF, the V-containing compound is V2O5 and the Se-containing compound is SeO2 or H2SeO4.

[0013] b. The LiV3Se2O obtained in step a 12 The compound was transferred into a quartz tube and evacuated to 10°C. -3 Pa;

[0014] c. Place the quartz tube from step b in a tube furnace with a temperature gradient, with the end of the quartz tube containing the material in the high-temperature zone and the other end in the low-temperature zone. Heat the quartz tube to 200-350℃ at a rate of 5-10℃ / h, hold it at that temperature for 1-3 days, and then cool it to room temperature at a rate of 0.5-1℃ / d. Open the quartz tube to obtain a birefringent crystal of lithium vanadium selenite with a size in the centimeter range.

[0015] The high-temperature melt method for preparing LiV3Se2O 12 For birefringent crystals, the specific procedures are as follows:

[0016] a. Mix the Li-containing compound, the V-containing compound, and the Se-containing compound evenly in a molar ratio of Li∶V∶Se=1∶3∶2. The Li-containing compound is Li2SO4, LiOH, LiNO3, Li2O, Li2CO3, or LiF, and the V-containing compound is V2O5 and the Se-containing compound is SeO2 or H2SeO4.

[0017] b. Place the mixed sample from step a into a quartz tube, and evacuate the quartz tube to a vacuum level of 10. -3 After Pa, perform melt sealing;

[0018] c. Place the quartz tube from step b in a muffle furnace and heat it to 250-450℃ at a rate of 10-30℃ / h, hold it at that temperature for 12 hours, and then cool it down to room temperature at a rate of 10-20℃ / h. After cooling, open the quartz tube to obtain LiV3Se2O. 12 Birefringent crystal;

[0019] LiV3Se2O was prepared by the crucible lowering method. 12 For birefringent crystals, the specific procedures are as follows:

[0020] a. Mix the Li-containing compound, V-containing compound, and Se-containing compound evenly in a molar ratio of Li∶V∶Se=1∶3∶2, and fill the mixture into a quartz tube. Evacuate the quartz tube to a vacuum degree of 10. -3 After Pa, the quartz tube is melt-sealed, then placed in a muffle furnace and heated to 250-450℃ at a rate of 10-30℃ / h, held at that temperature for 12 hours, and then cooled to room temperature at a rate of 10-20℃ / h. After cooling, the quartz tube is opened to obtain LiV3Se2O. 12The Li-containing compound is Li2SO4, LiOH, LiNO3, Li2O, Li2CO3 or LiF, the V-containing compound is V2O5 and the Se-containing compound is SeO2 or H2SeO4;

[0021] b. The quartz tube in step a is placed in a muffle furnace or oven, the furnace temperature is raised at a rate of 5-10℃ / h and controlled at 450-500℃, and then kept at this temperature for 12 hours, and then slowly cooled to room temperature at a rate of 1-5℃ / h to obtain a seed crystal of LiV3Se2O 12 ;

[0022] c. The seed crystal obtained in step b is placed at the bottom of a quartz tube, a platinum crucible, a gold crucible, an iridium crucible or a ceramic crucible, and then the pure phase compound obtained in step a is placed in the crucible, and then the crucible is sealed;

[0023] d. The crucible in step c is placed in a crucible lowering furnace, the furnace temperature is raised to 450-500℃ at a rate of 5-10℃ / h, and then kept at this temperature for 10-20 hours, the position of the crucible is adjusted so that the inoculation temperature is 350-425℃, and then the crucible is lowered at a rate of 1-10mm / day while keeping the growth temperature unchanged, and after the growth is completed, the growth furnace temperature is lowered to 30℃, the crucible is taken out, and a birefringent crystal of LiV3Se2O 12 is obtained.

[0024] The use of the vanadium lithium selenite birefringent crystal in the preparation of a polarizing prism, a phase delay device and an electro-optical modulation device.

[0025] The use of the vanadium lithium selenite birefringent crystal in the preparation of a polarizing prism, a phase delay device and an electro-optical modulation device.

[0026] The vanadium lithium selenite birefringent crystal obtained by the method of the present application has moderate mechanical hardness, is easy to cut, polish, process and store, is insoluble in water, does not deliquesce, is stable in air, and is suitable for making optical communication elements such as optical isolators, circulators, optical beam displacers, optical polarizers and optical modulators. It is particularly suitable for making polarizing prisms, phase delay devices and electro-optical modulation devices for various purposes. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The x-ray diffraction pattern of the LiV3Se2O 12 powder of the present application;

[0028] Figure 2 The photograph of the LiV3Se2O 12 crystal of the present application;

[0029] Figure 3 The photograph of the LiV3Se2O12 Crystal structure diagram;

[0030] Figure 4 LiV3Se2O 12 Birefringence curve;

[0031] Figure 5 Schematic diagram of the wedge-shaped birefringent crystal polarizing beam splitter of the present application, wherein 1 is incident light, 2 is o light, 3 is e light, 4 is an optical axis, and 5 is LiV3Se2O 12 Crystal;

[0032] Figure 6 Schematic diagram of the optical isolator of the present application, wherein 6 is a light transmission direction;

[0033] Figure 7 Schematic diagram of the optical beam displacer of the present application, wherein 1 is incident light, 2 is o light, 3 is e light LiV3Se2O 12 Crystal, 4 is an optical axis, and 5 is LiV3Se2O 12 Crystal, 6 is a light transmission direction, and 7 is an optical axis plane. DETAILED DESCRIPTION

[0034] The present application is further described below in conjunction with examples. It should be noted that the following examples do not limit the scope of the present application, and any improvement made on the basis of the present application does not deviate from the spirit of the present application. The raw materials or equipment used in the present application are commercially available unless otherwise specified.

[0035] Example 1

[0036] According to the reaction formula: Li2SO4+ 3V2O5+ 4SeO2→ 2LiV3Se2O 12 + SO3↑, the compound LiV3Se2O is prepared by a vacuum sealing method. 12 The specific operation is performed according to the following steps:

[0037] a. According to the proportion in the reaction formula, Li2SO4, V2O5 and SeO2 are mixed uniformly and then ground for 20 minutes;

[0038] b. The mixture in step a is loaded into a quartz tube, vacuumed to 10 -3 Pa, and then subjected to melt sealing;

[0039] c. The quartz tube in step b is placed in a muffle furnace, heated to 270°C at a rate of 5°C / hour, and kept at a constant temperature for 12 hours. After being cooled to room temperature, the muffle furnace is turned off, and the sample is taken out after cooling to obtain the compound LiV3Se2O 12 .

[0040] Example 2

[0041] LiV3Se2O by vacuum encapsulation method according to the reaction formula: 2LiOH + 3V2O5 + 4SeO2→ 2LiV3Se2O + H2O↑ 12 The compound LiV3Se2O is prepared by vacuum encapsulation method according to the reaction formula: 2LiOH + 3V2O5 + 4SeO2→ 2LiV3Se2O + H2O↑ 12 The specific operation is carried out according to the following steps:

[0042] a. According to the proportion in the reaction formula, LiOH, V2O5 and SeO2 are uniformly mixed and ground for 25 minutes;

[0043] b. The mixture in step a is transferred into a quartz tube, and the vacuum degree is 10 -3 Pa, and then the quartz tube is sealed with a flame spray gun;

[0044] c. The quartz tube in step b is placed in a muffle furnace, and the temperature is raised to 220°C at a rate of 10°C / h, and then the temperature is kept for 3 days, and then it is cooled to room temperature, to obtain the compound LiV3Se2O 12 .

[0045] Example 3

[0046] The compound LiV3Se2O is prepared by vacuum encapsulation method according to the reaction formula: 4LiNO3 + 6V2O5 + 8SeO2→ 4LiV3Se2O + 4NO2↑ + O2↑ 12 The compound LiV3Se2O is prepared by vacuum encapsulation method according to the reaction formula: 4LiNO3 + 6V2O5 + 8SeO2→ 4LiV3Se2O + 4NO2↑ + O2↑ 12 The specific operation is carried out according to the following steps:

[0047] a. According to the proportion in the reaction formula, LiNO3, V2O5 and SeO2 are uniformly mixed and ground for 20 minutes;

[0048] b. The mixture in step a is transferred into a quartz tube, and the vacuum degree is 10 -3 Pa, and then the quartz tube is sealed with a flame spray gun;

[0049] c. The quartz tube in step b is placed in a muffle furnace, and the temperature is controlled at 240°C, and then the temperature is kept for 2 days, and then it is cooled to room temperature, to obtain the compound LiV3Se2O 12 .

[0050] Example 4

[0051] The compound LiV3Se2O is prepared by vacuum encapsulation method according to the reaction formula: Li2O + 3V2O5 + 4SeO2→ 2LiV3Se2O 12 The compound LiV3Se2O is prepared by vacuum encapsulation method according to the reaction formula: Li2O + 3V2O5 + 4SeO2→ 2LiV3Se2O 12 The specific operation is carried out according to the following steps:

[0052] a. According to the proportion in the reaction formula, Li2O, V2O5 and SeO2 are uniformly mixed and ground for 20 minutes;

[0053] b. The mixture in step a is transferred into a quartz tube, and the vacuum degree is 10-3 Pa, and then the quartz tube is sealed with a flame gun;

[0054] c. The quartz tube in step b is placed in a muffle furnace, the furnace temperature is controlled at 260°C, and the temperature is kept for 2 days, and then the temperature is decreased to room temperature to obtain compound LiV3Se2O 12 .

[0055] Example 5

[0056] According to the reaction formula: 4Li2SO4+6V2O5+8H2SeO4→4LiV3Se2O 12 +16H2O↑+O2↑+4SO3↑, the compound LiV3Se2O 12 is prepared by a vacuum packaging method, and the specific operation is performed according to the following steps:

[0057] a. According to the proportion in the reaction formula, Li2SO4, V2O5 and H2SeO4 are uniformly mixed and ground for 25 minutes;

[0058] b. The mixture in step a is transferred into a quartz tube, and the vacuum degree is 10 -3 Pa, and then the quartz tube is sealed with a flame gun;

[0059] c. The quartz tube in step b is placed in a muffle furnace, the furnace temperature is controlled at 260°C, and the temperature is kept for 2 days, and then the temperature is decreased to room temperature to obtain compound LiV3Se2O 12 .

[0060] Example 6

[0061] According to the reaction formula: Li2CO3+3V2O5+4SeO2→2LiV3Se2O 12 +CO2↑, the compound LiV3Se2O 12 is prepared by a vacuum packaging method, and the specific operation is performed according to the following steps:

[0062] a. According to the proportion in the reaction formula, Li2CO3, V2O5 and SeO2 are uniformly mixed and ground for 30 minutes;

[0063] b. The mixture in step a is transferred into a quartz tube, and the vacuum degree is 10 -3 Pa, and then the quartz tube is sealed with a flame gun;

[0064] c. The quartz tube in step b is placed in a muffle furnace, the furnace temperature is controlled at 260°C, and the temperature is kept for 2 days, and then the temperature is decreased to room temperature to obtain compound LiV3Se2O 12 .

[0065] Example 7

[0066] Li2O + 3V2O5+ 4H2SeO4→ 2LiV3Se2O + 4H2O + 2O2 12 LiV3Se2O was prepared by vacuum encapsulation method according to the reaction formula: Li2O + 3V2O5+ 4H2SeO4→ 2LiV3Se2O + 4H2O + 2O2 12 The specific operation was carried out according to the following steps:

[0067] a. According to the proportion in the reaction formula, Li2O, V2O5 and H2SeO4 were mixed uniformly and ground for 20 minutes;

[0068] b. The mixture in step a was transferred into a quartz tube, vacuum degree was 10 -3 Pa, and the quartz tube was sealed by a flame spray gun;

[0069] c. The quartz tube in step b was placed in a muffle furnace, the furnace temperature was controlled at 250°C, and the temperature was kept for 2 days, and then it was reduced to room temperature, to obtain the compound LiV3Se2O 12 .

[0070] Example 8

[0071] LiV3Se2O was prepared by vacuum encapsulation method according to the reaction formula: LiF + 3V2O5+ 4H2SeO4→ 2LiV3Se2O + 3H2O + 2HF + 2O2 12 LiV3Se2O was prepared by vacuum encapsulation method according to the reaction formula: LiF + 3V2O5+ 4H2SeO4→ 2LiV3Se2O + 3H2O + 2HF + 2O2 12 The specific operation was carried out according to the following steps:

[0072] a. According to the proportion in the reaction formula, LiF, V2O5 and H2SeO4 were mixed uniformly and ground for 20 minutes;

[0073] b. The mixture in step a was transferred into a quartz tube, vacuum degree was 10 -3 Pa, and the quartz tube was sealed by a flame spray gun;

[0074] c. The quartz tube in step b was placed in a muffle furnace, the furnace temperature was controlled at 250°C, and the temperature was kept for 2 days, and then it was reduced to room temperature, to obtain the compound LiV3Se2O 12 .

[0075] Example 9

[0076] LiV3Se2O birefringent crystal was grown by chemical vapor deposition method 12 The specific operation was carried out according to the following steps:

[0077] The compound LiV3Se2O 12 obtained in Example 1 was transferred into a quartz tube, vacuum was extracted to 10 -3 Pa, and the quartz tube was sealed by a flame spray gun;

[0078] The quartz tube is placed in a tube furnace with a temperature gradient, one end of the quartz tube with the material is in the high temperature zone, and the other end is in the low temperature zone. The temperature is raised from room temperature to 400°C at a rate of 5°C / h in the high temperature zone, and then kept for 2 days. Then the temperature is lowered to room temperature at a rate of 1°C / d. The quartz tube is opened to obtain LiV3Se2O 12 birefringent crystal.

[0079] Example 10

[0080] LiV3Se2O 12 birefringent crystal, and the specific operation is carried out according to the following steps:

[0081] The compound LiV3Se2O 12 pure phase is obtained, which is transferred into a quartz tube, and vacuumized to 10 -3 Pa, and then the quartz tube is sealed by a flame spray gun;

[0082] The quartz tube is placed in a tube furnace with a temperature gradient, one end of the quartz tube with the material is in the high temperature zone, and the other end is in the low temperature zone. The temperature is raised from room temperature to 350°C at a rate of 6°C / h in the high temperature zone, and then kept for 12 hours. Then the temperature is lowered to room temperature at a rate of 1.5°C / d. The quartz tube is opened to obtain LiV3Se2O 12 crystal.

[0083] Example 11

[0084] LiV3Se2O 12 crystal, and the specific operation is carried out according to the following steps:

[0085] The compound LiV3Se2O 12 pure phase is obtained, which is transferred into a quartz tube, and vacuumized to 10 -3 Pa, and then the quartz tube is sealed by a flame spray gun;

[0086] The quartz tube is placed in a tube furnace with a temperature gradient, one end of the quartz tube with the material is in the high temperature zone, and the other end is in the low temperature zone. The temperature is raised from room temperature to 360°C at a rate of 10°C / h in the high temperature zone, and then kept for 2 days. Then the temperature is lowered to room temperature at a rate of 1.5°C / d. The quartz tube is opened to obtain LiV3Se2O 12 birefringent crystal.

[0087] Example 12

[0088] LiV3Se2O 12 birefringent crystal, and the specific operation is carried out according to the following steps:

[0089] The compound LiV3Se2O 12 The pure phase was put into a quartz tube, the quartz tube was vacuumized to a vacuum degree of 10 -3 Pa, and then was melt sealed;

[0090] The quartz tube was placed in a muffle furnace, and was heated to 250°C at a rate of 10°C / h, and was kept at 250°C for 12 hours, and then was cooled to room temperature at a rate of 10°C / h, and after cooling, the quartz tube was opened, and thus LiV3Se2O 12 birefringent crystal.

[0091] Example 13

[0092] LiV3Se2O 12 birefringent crystal, and the specific operation was performed according to the following steps:

[0093] The compound LiV3Se2O 12 The pure phase was put into a quartz tube, the quartz tube was vacuumized to a vacuum degree of 10 -3 Pa, and then was melt sealed;

[0094] The quartz tube was placed in a muffle furnace, and was heated to 300°C at a rate of 20°C / h, and was kept at 300°C for 12 hours, and then was cooled to room temperature at a rate of 15°C / h, and after cooling, the quartz tube was opened, and thus LiV3Se2O 12 birefringent crystal.

[0095] Example 14

[0096] LiV3Se2O 12 birefringent crystal, and the specific operation was performed according to the following steps:

[0097] The compound LiV3Se2O 12 The pure phase was put into a quartz tube, the quartz tube was vacuumized to a vacuum degree of 10 -3 Pa, and then was melt sealed;

[0098] The quartz tube was placed in a muffle furnace, and was kept at 450°C for 12 hours, and then was cooled to room temperature at a rate of 12°C / h, and after cooling, the quartz tube was opened, and thus LiV3Se2O 12 birefringent crystal.

[0099] Example 15

[0100] LiV3Se2O 12A birefringent crystal is prepared according to the following steps:

[0101] The compound LiV3Se2O 12 The pure phase is put into a quartz tube, the quartz tube is vacuumized, and the vacuum degree is 10 -3 Pa, and then is fused and sealed;

[0102] The quartz tube is placed in a muffle furnace, and is heated at a rate of 30°C / h to 350°C, and is kept at this temperature for 12 hours, and then is cooled at a rate of 20°C / h to room temperature. After cooling, the quartz tube is opened, and a large-size LiV3Se2O 12 birefringent crystal is obtained.

[0103] Example 16

[0104] The compound LiV3Se2O 12 A birefringent crystal is prepared according to the following steps:

[0105] The compound obtained in Example 8 is put into a quartz tube, and is placed in a muffle furnace, and is heated at a rate of 5°C / h to 450°C, and is kept at this temperature for 12 hours, and then is slowly cooled at a rate of 1°C / h to room temperature, and a seed crystal of LiV3Se2O 12 is obtained.

[0106] The obtained seed crystal is placed at the bottom of a quartz tube, and the obtained pure phase compound is put into a crucible, and then the crucible is sealed;

[0107] The crucible is placed in a crucible lowering furnace, and is heated at a rate of 5°C / h to 450°C, and is kept at this temperature for 10 hours. The position of the crucible is adjusted so that the inoculation temperature is 350°C, and then the crucible is lowered at a rate of 1mm / day, and the growth temperature is kept unchanged. After the growth is completed, the growth furnace temperature is lowered to 30°C, and the crucible is taken out, and a LiV3Se2O 12 birefringent crystal with a size of Ф11mmx0.5mmx0.2mm is obtained.

[0108] Example 17

[0109] The compound LiV3Se2O 12 A birefringent crystal is prepared according to the following steps:

[0110] The compound obtained in Example 1 is put into a quartz tube, and is placed in a muffle furnace, and is heated at a rate of 8°C / h to 480°C, and is kept at this temperature for 12 hours, and then is slowly cooled at a rate of 3°C / h to room temperature, and a seed crystal of LiV3Se2O 12 is obtained.

[0111] The obtained seed crystal is placed at the bottom of a gold crucible, and the obtained compound pure phase is placed in the crucible, and then the crucible is sealed;

[0112] The crucible is placed in a crucible lowering furnace, and the temperature is raised to 480℃ at a rate of 8℃ / h, and the temperature is kept for 15 hours. The position of the crucible is adjusted so that the inoculation temperature is 400℃, and then the crucible is lowered at a speed of 5mm / day, and the growth temperature is kept unchanged. After the growth is completed, the growth furnace temperature is lowered to 30℃, and the crucible is taken out, and a LiV3Se2O 12 Birefringent crystal.

[0113] Example 18

[0114] The LiV3Se2O 12 Birefringent crystal, and the specific operation is carried out according to the following steps:

[0115] b. The compound obtained in Example 2 is placed in a quartz tube and placed in an oven, and the temperature is raised at a rate of 10℃ / h and the furnace temperature is controlled at 500℃, and the temperature is kept for 12 hours. Then slowly cool to room temperature at a rate of 5℃ / h to obtain a LiV3Se2O 12 seed crystal;

[0116] The obtained seed crystal is placed at the bottom of a gold crucible, and the obtained compound pure phase is placed in the crucible, and then the crucible is sealed;

[0117] The crucible is placed in a crucible lowering furnace, and the temperature is raised to 480℃ at a rate of 8℃ / h, and the temperature is kept for 15 hours. The position of the crucible is adjusted so that the inoculation temperature is 400℃, and then the crucible is lowered at a speed of 5mm / day, and the growth temperature is kept unchanged. After the growth is completed, the growth furnace temperature is lowered to 30℃, and the crucible is taken out, and a LiV3Se2O 12 Birefringent crystal.

[0118] Example 19

[0119] The LiV3Se2O 12 Birefringent crystal, and the specific operation is carried out according to the following steps:

[0120] The compound obtained in Example 3 is placed in a quartz tube and placed in a muffle furnace, and the temperature is raised at a rate of 7℃ / h and the furnace temperature is controlled at 460℃, and the temperature is kept for 12 hours. Then slowly cool to room temperature at a rate of 2℃ / h to obtain a LiV3Se2O 12 seed crystal;

[0121] The obtained seed crystal is placed at the bottom of a gold crucible, and the obtained compound pure phase is placed in the crucible, and then the crucible is sealed;

[0122] The crucible is placed in a crucible lowering furnace, and heated to 460°C at a rate of 6°C / h, and kept for 13 hours. The position of the crucible is adjusted so that the seeding temperature is 370°C. The crucible is lowered at a rate of 10 mm / day, and the growth temperature is kept constant. After the growth is completed, the growth furnace temperature is lowered to 30°C, and the crucible is removed. LiV3Se2O 12 birefringent crystal.

[0123] Example 20

[0124] The LiV3Se2O 12 birefringent crystal is prepared by the crucible lowering method according to the following steps:

[0125] The compound obtained in Example 4 is placed in a quartz tube, and placed in an oven. The temperature is raised at a rate of 9°C / h, and the oven temperature is controlled at 47°C. The temperature is kept constant for 12 hours, and then slowly lowered to room temperature at a rate of 4°C / h. LiV3Se2O 12 seed crystal is obtained.

[0126] The obtained seed crystal is placed at the bottom of a ceramic crucible, and the obtained compound is placed in the crucible. The crucible is sealed.

[0127] The crucible is placed in a crucible lowering furnace, and heated to 490°C at a rate of 7°C / h, and kept for 13 hours. The position of the crucible is adjusted so that the seeding temperature is 410°C. The crucible is lowered at a rate of 4 mm / day, and the growth temperature is kept constant. After the growth is completed, the growth furnace temperature is lowered to 30°C, and the crucible is removed. LiV3Se2O 12 birefringent crystal is obtained.

[0128] Example 21

[0129] Any LiV3Se2O 12 birefringent crystal obtained in Examples 9-20 is used to prepare a wedge-shaped birefringent crystal polarizing beam splitter (as shown in Figure 5 , a wedge-shaped birefringent crystal, the orientation of the optical axis is as shown in Figure 5 . After a beam of natural light is incident, it can be divided into two beams of linearly polarized light. The greater the birefringence, the farther apart the two beams of light can be separated, facilitating the separation of the light beams.

[0130] Example 22

[0131] Any LiV3Se2O 12Birefringent crystals are used to fabricate optical isolators. An optical isolator is constructed 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. This isolator allows only 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.

[0132] Example 23

[0133] Any LiV3Se2O obtained in Examples 9-20 12 Birefringent crystals are used to fabricate beam shifters. A birefringent crystal is fabricated such that its optical axis plane forms an angle θ with the edge (e.g., ...). Figure 7 As 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 vanadous selenite lithium birefringent crystal characterized by The chemical formula of the crystal is LiV3Se2O 12 The crystal belongs to triclinic system, space group The cell parameters are α = 91.80(4)°, β = 93.15(4)°, γ = 106.24(4)°, The molecular weight is 509.68, and the crystal is prepared by chemical vapor deposition method, high-temperature melt method or crucible lowering method.

2. The method of claim 1, wherein the vanadium lithium selenite birefringent crystal is prepared by the steps of: The vanadium lithium selenite birefringent crystal is prepared by chemical vapor deposition, high temperature melt method or crucible descending method: ​ The chemical vapor deposition method for preparing LiV3Se2O 12 Birefringent crystals, the specific operational steps are as follows: a) mixing the Li-containing compound, the V-containing compound and the Se-containing compound uniformly in a molar ratio of Li:V:Se = 1:3:2, loading the quartz tube, vacuumizing the quartz tube, vacuumizing to 10 -3 Pa, and then melt-sealing; placing the sealed quartz tube in a muffle furnace, heating to 250-450°C at a rate of 10-30°C / h, and keeping the temperature constant for 12 hours; then decreasing the temperature to room temperature at a rate of 10-20°C / h, opening the quartz tube after cooling, and obtaining LiV3Se2O 12 The Li-containing compound is Li2SO4, LiOH, LiNO3, Li2O, Li2CO3 or LiF, the V-containing compound is V2O5, and the Se-containing compound is SeO2 or H2SeO4. b. The LiV3Se20 obtained in step a is converted into LiV3Se20 12 The compound is transferred into a quartz tube, evacuated to 10 -3 Pa; c. The quartz tube in step b is placed in a tube furnace with temperature gradient, one end of the quartz tube with material is in high temperature zone and the other end is in low temperature zone, the temperature is raised to 200-350℃ at a rate of 5-10℃ / h, and then kept for 1-3 days, and then decreased to room temperature at a rate of 0.5-1℃ / d, and then the quartz tube is opened to obtain the vanadium lithium selenite birefringent crystal with centimeter size; Preparation of LiV3Se2O by the high temperature melt method 12 Birefringent crystals are produced in accordance with the following procedure: a. The Li-containing compound, V-containing compound and Se-containing compound are mixed uniformly according to the molar ratio of Li:V:Se=1:3:2, the Li-containing compound is Li2SO4, LiOH, LiNO3, Li2O, Li2CO3 or LiF, the V-containing compound is V2O5 and the Se-containing compound is SeO2 or H2SeO4; b. The mixed sample in step a is loaded into a quartz tube, the quartz tube is vacuumized, the vacuum degree reaches 10 -3 Pa, and then is fusion sealed; c. The quartz tube in step b is placed in a muffle furnace, heated to 250-450 °C at a rate of 10-30 °C / h, kept constant for 12 hours, and then cooled to room temperature at a rate of 10-20 °C / h. After cooling, the quartz tube is opened to obtain LiV3Se2O 12 Birefringent crystal Preparation of LiV3Se2O by the crucible lowering method 12 Birefringent crystals are produced in accordance with the following procedure: a. mixing Li-containing compound, V-containing compound and Se-containing compound uniformly in a molar ratio of Li:V:Se = 1:3:2, loading into quartz tube, vacuumizing the quartz tube, vacuum degree reaching 10 -3 Pa, then melt sealing, then placing the sealed quartz tube in muffle furnace, heating to 250-450°C at a rate of 10-30°C / h, keeping constant temperature for 12 hours, then decreasing to room temperature at a rate of 10-20°C / h, opening the quartz tube after cooling, obtaining LiV3Se2O 12 compound; the Li-containing compound is Li2SO4, LiOH, LiNO3, Li2O, Li2CO3 or LiF, the V-containing compound is V2O5 and the Se-containing compound is SeO2 or H2SeO4; b. The quartz tube in step a is placed in a muffle furnace or oven, the temperature is raised at a rate of 5-10 °C / h and the furnace temperature is controlled at 450-500 °C, and kept constant for 12 hours, then slowly cooled to room temperature at a rate of 1-5 °C / h, to obtain the seed crystal of LiV3Se2O 12 ; c. The seed crystal obtained in step b is placed at the bottom of a quartz tube, platinum crucible, gold crucible, iridium crucible or ceramic crucible, and then the pure phase compound obtained in step a is placed in the crucible, and then the crucible is sealed; d. The crucible in step c is placed in a crucible lowering furnace, and heated to 450-500°C at a rate of 5-10°C / h, and kept for 10-20 hours. The position of the crucible is adjusted so that the inoculation temperature is 350-425°C, and the crucible is lowered at a rate of 1-10 mm / day, while keeping the growth temperature unchanged. After the growth is completed, the growth furnace temperature is lowered to 30°C, and the crucible is taken out, to obtain LiV3Se2O 12 Birefringent crystal.

3. The use of the vanadium lithium selenite birefringent crystal according to claim 1 in the preparation of optical communication elements, i.e. optical isolators, circulators, optical beam displacers, optical polarizers or optical modulators.

4. The use of the vanadium lithium selenite birefringent crystal according to claim 3 in the preparation of polarizing prisms, i.e. phase delay devices and electro-optical modulation devices.

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