A birefringent crystal and its preparation method

Abstract

The present invention discloses a birefringent crystal and a preparation method thereof, belonging to the technical field of optical materials. The chemical formula of the birefringent crystal is (C 12 H8N2)SbF2(H2PO3); The space group of the birefringent crystal is the P-1 space group of the triclinic system; the unit cell parameters are α=106.324°, β=90.246°, γ=105.428°, and Z=2. The present invention adopts o-phenanthroline phosphite ionic liquid to synthesize birefringent crystals by an ionothermal method, which effectively solves the problem that Sb(III) is easily hydrolyzed. In the birefringent crystals prepared by the present invention, the N atoms on the o-phenanthroline ring chelate with the Sb atoms to form a coordination bond so that the lone pair of electrons of Sb always maintains a certain angle with the b-plane, which significantly improves the birefringence of the obtained birefringent crystals.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical materials, and in particular relates to a birefringent crystal and a preparation method thereof. Background Art

[0002] Birefringent crystals play an important role in linear optics due to their ability to modulate light polarization. Commercial birefringent crystals have been widely used as polarization devices over the past few decades. Birefringence is a linear optical property that occurs in anisotropic crystals. In anisotropic crystals, birefringence occurs when the refractive index of light varies with the direction of light.

[0003] Existing commercial birefringent crystals include TiO2 (exp. 0.256 @ 546 nm), YVO4 (exp. 0.204 @ 532 nm), CaCO3 (exp. 0.172 @ 532 nm), LiNbO3 (exp. 0.074 @ 532 nm), and α-BaB2O4 (α-BBO, exp. 0.122 @ 546 nm). However, natural birefringent crystals such as CaCO3 and TiO2 suffer from poor quality and numerous defects, limiting their application. On the other hand, artificial birefringent crystals, such as YVO4, α-BBO, and LiNbO3, are relatively expensive. Among all commercially available birefringent crystals, α-BBO is the most widely used UV-transparent crystal (λ < 400 nm) and exhibits a high birefringence (Δn = 0.122 @ 546 nm). However, the birefringence of α-BBO (Δn=0.122@546nm) is relatively small, and its application in practice is also limited. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides a birefringent crystal and a preparation method thereof, so as to solve the technical problems of the prior art such as difficulty in preparing birefringent crystals and low birefringence.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is to provide a birefringent crystal, the chemical formula of the birefringent crystal is (C 12 H8N2)SbF2(H2PO3); the space group of the birefringent crystal is the P-1 space group of the triclinic system; the unit cell parameters are α=106.324°, β=90.246°, γ=105.428°, Z=2.

[0006] The present invention also provides a method for preparing the above-mentioned birefringent crystal, comprising the following steps:

[0007] S1: dissolving o-phenanthroline and phosphorous acid in a solvent, and then evaporating the solvent to obtain o-phenanthroline phosphorous acid ionic liquid;

[0008] S2: mixing o-phenanthroline phosphite ionic liquid and antimony-containing compound, reacting the mixture under sealed conditions at 80-90° C. for 4-6 days, and then air-cooling to room temperature to obtain a precursor solution;

[0009] S3: The precursor solution is allowed to stand at room temperature for 4 to 6 days, and the precipitated crystals are collected, washed, and dried to obtain the product.

[0010] On the basis of the above technical solution, the present invention can also be improved as follows.

[0011] Furthermore, the solvent is deionized water.

[0012] Furthermore, the molar ratio of o-phenanthroline to phosphorous acid is 1:1.

[0013] Furthermore, the mass ratio of the o-phenanthroline phosphite ionic liquid to the antimony-containing compound is 25-30:8-12.

[0014] Furthermore, the antimony-containing compound is SbF3.

[0015] Furthermore, the reaction temperature in S2 is 80° C. and the reaction time is 5 days.

[0016] Furthermore, the cleaning method in S3 is to rinse with DMF 1 to 3 times.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention adopts o-phenanthroline phosphite ionic liquid to synthesize birefringent crystal (C 12 H8N2)SbF2(H2PO3), in which the ionic liquid is both a reactant and a solvent, effectively solving the problem of easy hydrolysis of Sb(III) and achieving innovation in the preparation method.

[0019] 2. The birefringent crystal prepared by the present invention (C 12 H8N2)SbF2(H2PO3) has a special unit cell structure. The nitrogen atom on the o-phenanthroline ring chelates with the Sb atom to form a coordination bond, which makes the lone pair of electrons of Sb always maintain a certain angle with the b plane, which makes the birefringent crystal (C 12 The birefringence of H8N2)SbF2(H2PO3) is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 For birefringent crystals (C 12The formation mechanism diagram of H8N2)SbF2(H2PO3); Among them, (a) is the structure diagram of o-phenanthroline ring; (b) is the structure diagram of SbF3 after removing one Sb-F bond; (c) is the structure diagram of H2PO3; (d) is the structure diagram of SbN2OF2 with three impurities and five coordination; (e) is the structure diagram of birefringent crystal (C 12 H8N2)SbF2(H2PO3) structure diagram;

[0021] Figure 2 For birefringent crystals (C 12 X-ray powder diffraction pattern of H8N2)SbF2(H2PO3);

[0022] Figure 3 For birefringent crystals (C 12 H8N2)SbF2(H2PO3) thermogravimetric spectrum;

[0023] Figure 4 For birefringent crystals (C 12 Infrared spectrum of H8N2)SbF2(H2PO3);

[0024] Figure 5 For birefringent crystals (C 12 Theoretical calculated birefringence values ​​of H8N2)SbF2(H2PO3);

[0025] Figure 6 For birefringent crystals (C 12 Birefringence test chart of H8N2)SbF2(H2PO3). DETAILED DESCRIPTION

[0026] The specific implementation methods of the present invention are described in detail below with reference to the embodiments.

[0027] Example 1

[0028] A birefringent crystal, the chemical formula of the birefringent crystal is (C 12 H8N2)SbF2(H2PO3); which is prepared by the following steps:

[0029] S1: o-phenanthroline and phosphorous acid are mixed in a molar ratio of 1:1, and the mixture is dissolved in deionized water, and then slowly stirred at 100° C. to evaporate and remove water to obtain o-phenanthroline phosphorous acid ionic liquid;

[0030] S2: o-phenanthroline phosphite ionic liquid and SbF3 were mixed in a mass ratio of 26:9, and the mixture was sealed in a polytetrafluoroethylene liner at room temperature and pressure, and placed in a forced air drying oven at 85°C. The reaction was carried out at this temperature for 5 days, and then the mixture was taken out and naturally cooled to room temperature to obtain a precursor solution;

[0031] S3: The precursor solution was allowed to stand at room temperature for 5 days, the precipitated crystals were collected, washed twice with N,N-dimethylformamide (DMF), and then dried at 50°C to obtain.

[0032] Example 2

[0033] A birefringent crystal, the chemical formula of the birefringent crystal is (C 12 H8N2)SbF2(H2PO3); which is prepared by the following steps:

[0034] S1: o-phenanthroline and phosphorous acid are mixed in a molar ratio of 1:1, and the mixture is dissolved in deionized water, and then slowly stirred at 100° C. to evaporate and remove water to obtain o-phenanthroline phosphorous acid ionic liquid;

[0035] S2: o-Phenanthroline phosphite ionic liquid and SbF3 were mixed in a mass ratio of 25:8, and the mixture was sealed in a polytetrafluoroethylene liner at room temperature and pressure, and placed in a forced air drying oven at 80°C. The reaction was carried out at this temperature for 6 days, and then the mixture was taken out and naturally cooled to room temperature to obtain a precursor solution;

[0036] S3: The precursor solution was allowed to stand at room temperature for 4 days, the precipitated crystals were collected, washed once with N,N-dimethylformamide (DMF), and then dried at 50°C to obtain.

[0037] Example 3

[0038] A birefringent crystal, the chemical formula of the birefringent crystal is (C 12 H8N2)SbF2(H2PO3); which is prepared by the following steps:

[0039] S1: o-phenanthroline and phosphorous acid are mixed in a molar ratio of 1:1, and the mixture is dissolved in deionized water, and then slowly stirred at 100° C. to evaporate and remove water to obtain o-phenanthroline phosphorous acid ionic liquid;

[0040] S2: o-phenanthroline phosphite ionic liquid and SbF3 were mixed in a mass ratio of 30:12, and the mixture was sealed in a polytetrafluoroethylene liner at room temperature and pressure, and placed in a forced air drying oven at 90°C. The reaction was carried out at this temperature for 4 days, and then the mixture was taken out and naturally cooled to room temperature to obtain a precursor solution;

[0041] S3: The precursor solution was allowed to stand at room temperature for 6 days, the precipitated crystals were collected, washed with N,N-dimethylformamide (DMF) 3 times, and then dried at 50°C to obtain.

[0042] Experimental example

[0043] The performance of the birefringent crystals prepared in Examples 1 to 3 is similar, and the performance of the birefringent crystal in Example 1 is described below by taking it as an example.

[0044] 1. Birefringent crystal (C 12 Structural Analysis of H8N2)SbF2(H2PO3)

[0045] Birefringent crystal (C 12 The formation mechanism of H8N2)SbF2(H2PO3) is as follows Figure 1 As shown in the figure, it can be seen that when forming a birefringent crystal (C 12 H8N2)SbF2(H2PO3), the o-phenanthroline ring ( Figure 1 a) The two N atoms on the top chelate with the Sb atoms in SbF3 to form coordination bonds, and SbF3 removes one Sb-F bond ( Figure 1 b) with H2PO3( Figure 1 c) Through the shared oxygen atom bridge, a distorted polyhedron of SbN2OF2 with three heterogeneous pieces and five coordinations is formed ( Figure 1 d), overlap in three-dimensional space to form a zero-dimensional structure ( Figure 1 e), namely birefringent crystal (C 12 H8N2)SbF2(H2PO3). Birefringent crystal (C 12 The structure of H8N2)SbF2(H2PO3) is centrosymmetric and crystallizes in the P-1 space group of the triclinic system. The unit cell parameters are α=106.324°,β=90.246°,γ=105.428°,Z=2. An asymmetric structural unit is composed of 1 Sb, 2 F, 1 P, 3 O, 2 N, 9 H, and 12 C atoms.

[0046] 2. Birefringent crystal (C 12 Characterization of H8N2)SbF2(H2PO3)

[0047] (1) Birefringent crystal (C 12 X-ray Powder Diffraction Analysis of H8N2)SbF2(H2PO3)

[0048] Figure 2 For birefringent crystals (C 12 X-ray powder diffraction patterns of SbF2(H2PO3) experimental test (red line) and software fitting (black line); through careful comparison of each diffraction peak, it is found that the birefringent crystal (C 12 The peak positions of the experimental spectrum of H8N2)SbF2(H2PO3) and the fitting spectrum are in good agreement, which shows that pure phase crystals are synthesized.

[0049] (2) Birefringent crystal (C 12 Thermogravimetric Analysis of H8N2)SbF2(H2PO3)

[0050] Figure 3 For birefringent crystals (C 12 H8N2)SbF2(H2PO3) thermogravimetric analysis diagram; It can be seen from the figure that the birefringent crystal (C 12 H8N2)SbF2(H2PO3) starts to lose weight when heated to about 250℃, indicating that the prepared crystal has good thermal stability.

[0051] (3) Birefringent crystal (C 12 Infrared Spectrum Analysis of H8N2)SbF2(H2PO3)

[0052] Birefringent crystal (C 12 The infrared spectrum of H8N2)SbF2(H2PO3) is as follows Figure 4 As shown. In the infrared spectrum, 3400 cm -1 The absorption peak at 1600~700cm belongs to the stretching vibration of the parent tertiary amine of o-phenanthroline. -1 The absorption peaks in the range belong to the stretching vibration of the carbon-carbon double bond skeleton of the o-phenanthroline parent and the bending vibration of CH, 1200 cm -1 The absorption peaks around 1000cm are affected by the stretching vibration of the PH bond. -1 The absorption peaks on the left and right are the stretching vibrations of the HPO3 group, located at 720 / 560 / 460 cm -1 The absorption peaks at 590 / 520 / 420 cm are the asymmetric stretching vibrations of the Sb-O bond. -1 The absorption peak at belongs to the bending vibration of Sb-O / Sb-F bond.

[0053] (4) Birefringent crystal (C 12 Birefringence test of H8N2)SbF2(H2PO3)

[0054] Birefringent crystal (C 12 The theoretical calculated value of birefringence of H8N2)SbF2(H2PO3) is as follows Figure 5 As shown; it can be seen from the figure that the birefringent crystal (C 12 The theoretical calculated value of birefringence of H8N2)SbF2(H2PO3) is 0.317@546nm.

[0055] Zeiss Axio A5 polarizing microscope is used to measure birefringent crystals (C 12 H8N2)SbF2(H2PO3) birefringence. Figure 6 As shown, the birefringent crystal (C 12The birefringence of H8N2)SbF2(H2PO3) is 0.34@546nm, which is the highest birefringence among the published antimony-based oxygen-containing acid birefringence materials. In addition, due to the bidentate nature of the o-phenanthroline ligand, two N atoms are chelated with the Sb atom. This coordination mode fixes the orientation of the lone pair electrons in the Sb atom, so that the lone pair electrons of the Sb atom maintain a certain angle with the b plane. This unique coordination mode significantly contributes to the enhancement of birefringence. Based on the influence of the above two factors, the birefringent crystal (C 12 The birefringence of H8N2)SbF2(H2PO3) is significantly improved compared with other antimony-based tetrahedral groups.

[0056] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A birefringent crystal, characterized in that: The chemical formula of the birefringent crystal is (C 12 H8N2)SbF2(H2PO3), among which C 12 H8N2 is o-phenanthroline; the space group of the birefringent crystal is triclinic. P -1 space group; unit cell parameters are a=8.5079(4)Å, b=8.8463(4)Å, c=9.8913(5)Å, α=106.324°, β=90.246°, γ=105.428°, Z=2.

2. The method for preparing a birefringent crystal according to claim 1, wherein The following steps are involved: S1: dissolving o-phenanthroline and phosphorous acid in a solvent, and then evaporating the solvent to obtain an o-phenanthroline-phosphorous acid ionic liquid; wherein the molar ratio of o-phenanthroline to phosphorous acid is 1:1; S2: mixing an o-phenanthroline phosphite ionic liquid and an antimony-containing compound, reacting the mixture under a sealed condition at 80-90° C. for 4-6 days, and then air-cooling to room temperature to obtain a precursor solution; the mass ratio of the o-phenanthroline phosphite ionic liquid to the antimony-containing compound is 25-30:8-12; S3: The precursor solution is allowed to stand at room temperature for 4 to 6 days, and the precipitated crystals are collected, washed, and dried.

3. The preparation method according to claim 2, wherein: The solvent is deionized water.

4. The preparation method according to claim 2, wherein: The antimony-containing compound is SbF3.

5. The preparation method according to claim 2, wherein: The reaction temperature in S2 is 80° C. and the reaction time is 5 days.

6. The preparation method according to claim 2, wherein: The cleaning method in S3 is to rinse with DMF 1 to 3 times.

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