A birefringent crystal material and its preparation method and application

Abstract

The present invention relates to the technical field of artificial crystal materials, and more specifically to a birefringent crystal material, its preparation method, and its application. The present invention provides a new birefringent crystal material having the chemical formula [C(NH2)3][ICl4] and exhibiting a large birefringence. The preparation method for this birefringent crystal material utilizes raw materials with low human toxicity, a short crystal growth cycle, low cost, and high crystal purity. This birefringent crystal material can be used as a polarization optical device in the fields of optics and communications.

Description

Technical Field

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

[0002] Birefringent crystal materials are the core media for manipulating the polarization state of light waves in optoelectronic devices and are widely used in precision optical modulators, polarization sensors, and optical communication devices. Although inorganic birefringent materials have become commercially available, their inherent flaws, such as optical uniformity, processing difficulty, and environmental stability, severely restrict their application prospects in optical devices. For example, natural calcite (CaCO3) suffers from insufficient optical uniformity due to lattice defects; titanium dioxide (TiO2) is expensive to synthesize and difficult to process; the anisotropic thermal expansion of α-phase barium metaborate (α-BaB2O4) can easily lead to thermal stress mismatch in devices; the transmittance of yttrium vanadate (YVO4) drops sharply in the deep ultraviolet band; and the birefringence of lithium niobate (LiNbO3) is difficult to meet the requirements of high-precision control.

[0003] With the development of the times, people have higher and higher requirements for birefringent crystal materials. Therefore, the development of new birefringent crystal materials has become a key path to promote the performance leap of optoelectronic devices. Summary of the Invention

[0004] The object of the present invention is to provide a birefringent crystal material and a preparation method and application thereof, so as to solve at least one technical problem existing in the prior art.

[0005] The first aspect of the present invention provides a birefringent crystal material having the chemical formula [C(NH2)3][ICl4], belonging to the monoclinic system, and having a space group of P twenty one / c , the unit cell parameters are a = 14.96~15.78 Å, b = 3.99~4.00 Å, c = 15.00~15.75 Å, α = 90°, β = 95.10 ~ 95.18°, γ = 90°, V = 935.3~942.2 Å 3 , Z = 4.

[0006] The above-mentioned birefringent crystal material comprises [ICl4] - The polarizability anisotropy of the unit reaches a maximum value in the four-coordinate structural unit, so the birefringent crystal material has a significantly higher birefringence.

[0007] Furthermore, the unit cell parameters of the birefringent crystal material are a = 15.779(8) Å, b = 3.996(2)Å, c = 15.003(7) Å, α = 90°, β = 96.336°, γ = 90°, V = 942(8) Å 3 , Z = 4.

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned birefringent crystal material, which comprises the following steps:

[0009] Dissolve guanidine hydrochloride (CN3H6Cl) and iodine pentoxide (I2O5) in an acidic solution to obtain a mixed solution;

[0010] The mixed solution is stirred, and the viscous substance formed at the bottom of the mixed solution is removed. The mixed solution is stirred until it becomes clear, and then allowed to stand for crystallization to obtain the birefringent crystal material.

[0011] Furthermore, the molar ratio of the guanidine hydrochloride to the iodine pentoxide can be 6-8:1.

[0012] Furthermore, the acidic solution may be a hydrochloric acid solution, a sulfuric acid solution, a nitric acid solution or a phosphoric acid solution.

[0013] Furthermore, the concentration of the acidic solution may be in the range of 3 to 6 mol / L.

[0014] Furthermore, the standing crystallization time can be 6 to 15 days.

[0015] The third aspect of the present invention provides the use of the above-mentioned birefringent crystal material in the preparation of polarization optical devices.

[0016] A fourth aspect of the present invention provides a polarization optical device comprising a birefringent crystal formed from the above-mentioned birefringent crystal material.

[0017] Furthermore, the polarization optical device is a polarization sensor, a wide spectrum device or a polarization beam splitter.

[0018] Furthermore, the polarization optical device is an optical isolator.

[0019] The technical solution of the embodiment of the present invention has the following beneficial effects:

[0020] Provided is a new birefringent crystal material having a large birefringence; a method for preparing the birefringent crystal material uses raw materials with low human toxicity, a short crystal growth cycle, low cost, and high crystal purity; the birefringent crystal material can be used as a polarization optical device in the fields of optics and communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the crystal structure of the birefringent crystal material in an embodiment of the present invention.

[0022] Figure 2 It is the X-ray diffraction pattern of the birefringent crystal material in the embodiment of the present invention and the X-ray diffraction pattern simulated based on the [C(NH2)3][ICl4] crystal structure.

[0023] Figure 3 This is a UV projection spectrum of the birefringent crystal material in an embodiment of the present invention.

[0024] Figure 4 The refractive index and birefringence of the birefringent crystal material at different wavelengths are theoretically calculated in the embodiments of the present invention.

[0025] Figure 5 Schematic diagram of the working principle of the polarization optical device in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Birefringent crystal material samples 1# to 6# were prepared using an aqueous solution method. The steps are as follows: in a beaker, guanidine hydrochloride, iodine pentoxide, and an acidic solution were mixed in a certain proportion to obtain a mixed solution; the mixed solution was stirred, and the viscous material formed at the bottom was filtered. The solution was stirred until it became clear. The mixture was sealed with plastic wrap, and a hole was made in the plastic wrap. The mixture was allowed to stand at room temperature for a period of time. Yellow rod-shaped crystals grew at the bottom of the mixed solution, which was the birefringent crystal material.

[0028] The relationship between the types and ratios of the raw materials in the initial mixture, the concentration and volume of the acid solution, the crystallization time and the sample number is shown in Table 1.

[0029] Table 1 Correspondence between samples in each example and the raw materials and synthesis conditions

[0030]

[0031] Single crystal X-ray diffraction and powder X-ray diffraction methods were used to perform structural analysis and purity analysis on samples 1#~6#, respectively. The samples were tested in an Agilent SuperNova single crystal diffractometer equipped with a molybdenum target (λ=0.71073Å), and the diffraction data of the single crystals were collected at 293(2) K. After the data collection was completed, the collected single crystal data were processed using OLEX2 software; the crystal structure was refined using the full matrix least squares technique using the SHELXTL program suite, and the crystal structure was analyzed and refined; finally, PLATON software was used to check whether the single crystal structure had higher symmetry, and the crystal structure was finally obtained. The single crystal X-ray diffraction results showed that samples 1#~6# had the same chemical formula and crystal structure, with a chemical formula of [C(NH2)3][ICl4] and a molecular weight of 328.79; they belonged to the monoclinic system and the space group was P twenty one / c , the unit cell parameters are a = 14.96~15.78 Å, b = 3.99~4.00 Å, c = 15.00~15.75 Å, α = 90°, β = 95.10 ~ 95.18°, γ = 90°, V = 935.3~942.2 Å 3 , Z = 4.

[0032] Taking sample 1# as a typical representative, its crystallographic parameters are: unit cell parameters a = 15.779(8) Å, b = 3.996(2) Å, c = 15.003(7) Å, α = 90°, β = 96.336°, γ = 90°, V = 942(8) Å 3 , Z = 4. The crystal structure of sample 1# is as follows Figure 1 shown.

[0033] The powder X-ray diffraction test was performed using a Miniflex 600 powder X-ray diffractometer (λ=1.5418Å). The diffraction angle range was set to 5°~75°, the step width was 0.02°, and the rate was 0.01°s⁻¹. The powder X-ray diffraction test results showed that in the X-ray diffraction spectra of samples 1#~6#, the peak positions of each sample were the same, but the peak intensities were slightly different. Taking sample 1# as a typical example, Figure 2 As shown in the figure, the peak positions of the fitted X-ray diffraction pattern obtained based on the crystal structure analyzed by single crystal X-ray diffraction are exactly the same as those of the X-ray diffraction pattern measured after grinding into powder of Sample 1#, with slightly different peak intensities. This indicates that the obtained sample has a high purity.

[0034] The diffuse reflectance spectrum of sample 1# was measured on a PerkinElmer Lamda-950 UV / Vis / NIR spectrophotometer. The specific measurement process is as follows: First, a baseline is scanned using BaSO4 as a standard sample (100% reflectance). Then, pure sample 1# powder is evenly sprinkled on the BaSO4 surface and compacted with a quartz column before testing. The diffuse reflectance characteristics of sample 1# are recorded within the range of 200-800 nm. The results are shown in Figure 2. Figure 3 As shown, the diffuse reflectance spectrum of sample 1# shows that its absorption cutoff edge is around 243 nm. Based on the Kubelka-Munk function, the reflectivity can be used to calculate the experimental energy gap:

[0035] F(R)=(1-R) 2 / (2R)=K / S

[0036] Where R is reflectivity, K is absorption, and S is scattering. According to the above formula, the experimental band gap of sample 1# can be calculated to be 2.34 eV.

[0037] The optical properties of samples 1# - 6# were calculated based on first-principles density functional theory, and the calculation of refractive index showed obvious anisotropy. Figure 4 As shown, the birefringence reaches 0.95 at a wavelength of 550 nm.

[0038] Samples 1# - 6# can be used to prepare polarization optical devices. The polarization optical devices are optical isolators, such as Figure 5 As shown, the optical isolator core comprises a first birefringent crystal 2, an optical rotator 3, and a second birefringent crystal 4. Both the first and second birefringent crystals 2 and 4 are formed from the birefringent crystal material [C(NH2)3][ICl4]. The optical isolator is placed in the optical path. A laser emitter 1 emits a light beam, which passes through the first birefringent crystal 2 and is split into e-light and o-light. The beam then passes through the optical rotator 3 and enters the second birefringent crystal 4. The resulting outgoing light beam is collected by a collimator 5.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A birefringent crystal material, characterized in that: The chemical formula is [C(NH2)3][ICl4], belonging to the monoclinic system, space group is P21 / c, unit cell parameters are a = 14.96~15.78 Å, b = 3.99~4.00 Å, c = 15.00~15.75 Å, α = 90°, β = 95.10 ~ 95.18°, γ = 90°, V = 935.3~942.2 Å 3 , Z = 4.

2. The method for preparing a birefringent crystal material according to claim 1, wherein: The following steps are involved: Dissolve guanidine hydrochloride (CN3H6Cl) and iodine pentoxide (I2O5) in an acidic solution to obtain a mixed solution; The mixed solution is stirred, and the viscous substance formed at the bottom of the mixed solution is removed. The mixed solution is further stirred until it becomes clear, and then allowed to stand for crystallization to obtain the birefringent crystal material.

3. The method according to claim 2, characterized in that The molar ratio of CN3H6Cl and I2O5 is 6~8:

1.

4. The method according to claim 2, characterized in that The acidic solution is hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid.

5. The method according to claim 2, characterized in that The concentration range of the acidic solution is 3-6 mol / L.

6. The method according to claim 2, characterized in that The crystallization time is 6-15 days.

7. Use of the birefringent crystal material according to claim 1 in preparing polarization optical devices.

8. A polarization optical device, characterized in that: A birefringent crystal formed from the birefringent crystal material according to claim 1.

9. The polarization optical device according to claim 8, characterized in that The polarization optical device is a polarization sensor or a polarization beam splitter.

10. The polarization optical device according to claim 8, wherein The polarization optical device is an optical isolator.

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