A tellurium molybdate birefringent crystal material and its preparation and application

Abstract

The present invention relates to a tellurium molybdate birefringent crystal material and its preparation and application. The chemical formula of the material is Mo(H2O)Te2O7, which belongs to the tetragonal system, has a space group of I‑4, unit cell parameters of #imgabs0##imgabs1#α=β=γ=90°, Z=8, and a unit cell volume of #imgabs2##imgabs3#. The birefringence value of the Mo(H2O)Te2O7 crystal of the present invention reaches 0.53 at 546nm, which is significantly greater than the birefringence efficiency of the existing commercial birefringent crystal. Under 1064nm laser irradiation, the frequency doubling effect of the Mo(H2O)Te2O7 crystal powder is 5.4 times that of KH2PO4 (KDP), and phase matching can be achieved. The Mo(H2O)Te2O7 crystal has broad application prospects in the fields of laser frequency conversion, photoelectric modulation, laser signal holographic storage, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of linear and nonlinear optical crystal materials, and relates to a tellurium molybdate birefringent crystal material and a preparation method and application thereof. Background Art

[0002] Birefringent materials that can modulate polarized light are an important part of modern optoelectronic technology and are widely used in linear optical devices, fiber optic sensors, and advanced optical communication systems. Several well-known inorganic birefringent materials have been discovered, such as natural crystalline CaCO 3 (birefringence is 0.172 at 532nm), TiO 2 (birefringence is 0.256 at 546nm), and artificial lens α-BaB 2 O 4 (birefringence is 0.122 at 546nm), YVO 4 (birefringence 0.204 at 532nm) and LiNbO 3 (Birefringence is 0.074 at 546nm). However, defects and impurities in natural crystals result in low crystal quality. 2 O 4 There is obvious anisotropic thermal expansion, YVO 4 The UV transmittance of LiNbO is weak. 3 The inherent defects of birefringent materials such as relatively low birefringence greatly limit their application in high-tech needs. Therefore, the development of new birefringent materials with strong optical anisotropy is of great significance in both academia and business. Summary of the invention

[0003] The purpose of the present invention is to provide a tellurium molybdate birefringent crystal material and its preparation and application. The crystal exhibits strong optical anisotropy, with a birefringence index of 0.53 at 546nm and a powder frequency doubling effect of KH at 1064nm. 2 PO 4 The molybdate tellurium salt is a functional crystal with double refraction and double frequency response and has potential application value.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] One of the technical solutions of the present invention provides a tellurium molybdate birefringent crystal material, the chemical formula of which is Mo(H 2 O)Te 2 O 7 , belongs to the tetragonal system, its space group is I-4, and the unit cell parameters are α=β=γ=90°,Z=8,the unit cell volume is

[0006] Furthermore, the unit cell parameters of the crystal material are α=β=γ=90°,Z=8,the unit cell volume is

[0007] The crystal structure of the tellurium molybdate oxide of the present invention is as follows: In the tellurium molybdate crystal, the main building block - polytellurium oxide anion [Te 8 O 20 ] is composed of four triangular pyramidal [Te(1)O 3 ] groups and four seesaw-like [Te(2)O 4 ] groups are connected by corner-shared oxygen atoms [O(3) and O(5)]. Adjacent polytellurate anions [Te 8 O 20 ]The distance between the structural unit planes is Each [Te 8 O 20 ] 8- The structural unit is [MoO 6 ] octahedron further connects with eight adjacent polytellurate anions [Te 8 O 20 ] 8- connection, ultimately forming a three-dimensional covalent framework with a twelve-membered ring channel on the ab plane.

[0008] The second technical solution of the present invention provides a method for preparing a tellurium molybdate birefringent crystal material, which firstly takes a cerium source, a tellurium source, a molybdenum source, a fluorine source and water and mixes them to form an initial mixed raw material, wherein the cerium source serves as a mineralizer and the fluorine source provides an acidic environment, which is more conducive to the growth of the crystal material, and then places it under sealed hydrothermal conditions for reaction and crystallization to obtain the target product.

[0009] Furthermore, the cerium source is cerium dioxide; the tellurium source is tellurium dioxide; the molybdenum source is molybdenum trioxide; and the fluorine source is hydrofluoric acid.

[0010] Furthermore, in the initial mixed raw material, the molar ratio of cerium element, tellurium element, molybdenum element and fluorine element is 1: (0.5-50): (0.5-20): (0.5-50).

[0011] Furthermore, in the initial mixed raw material, the molar ratio of cerium element, iodine element, fluorine element and sulfuric acid is 1:(1-20):(1-10):(2-20).

[0012] Further, the hydrothermal temperature is 150-230°C, and the crystallization time is not less than 24 hours. Preferably, the hydrothermal temperature is 180-230°C, and the crystallization time is not less than 48 hours. At the same time, after the crystallization is completed, the temperature is cooled to room temperature at a cooling rate of 0.5-15°C / h, and preferably, the cooling rate is 0.5-6°C / h.

[0013] A third technical solution of the present invention provides an application of a tellurium molybdate birefringent crystal material, which is used in a frequency doubling generator, an optical parametric oscillator, an optical parametric amplifier and a photoelectric rectifier.

[0014] A fourth technical solution of the present invention provides the application of tellurium molybdate birefringent crystal material, which is used for modulation of polarized light.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention provides a new inorganic crystal material, tellurium molybdate compound, which exhibits strong optical anisotropy and a birefringence index of 0.53 at 546nm. Under 1064nm laser irradiation, the crystal material has a large powder frequency doubling effect, about KH 2 PO 4 The crystal frequency doubling intensity is 5.4 times that of the original material, and type I phase matching can be achieved. In addition, the crystal material has a wide light transmission range in both the ultraviolet-visible light region and the infrared light region, a band gap of 3.39 eV, and a thermal stability temperature of 240°C. It has broad application prospects in the fields of laser frequency conversion, optoelectronic modulation, and holographic storage of laser signals.

[0017] (2) The present invention provides a method for preparing the tellurium molybdate crystal material, which adopts a hydrothermal method with mild reaction conditions. At a temperature of 150 to 230° C., a high-purity crystalline sample can be obtained in high yield through hydrothermal crystallization. The method is simple, the conditions are mild, and it is conducive to large-scale industrial production.

[0018] (3) The tellurium molybdate crystal material of the present invention can be applied to the modulation of polarized light and laser frequency converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the crystal structure of tellurium molybdate;

[0020] Figure 2 : It is a comparison diagram of powder X-ray diffraction, where (a) is the simulated powder X-ray diffraction pattern of sample 1# based on the crystal structure analyzed according to the single crystal X-ray diffraction data; (b) is the pattern obtained by X-ray diffraction test after sample 1# is ground into powder;

[0021] Figure 3is the UV-Vis-NIR absorption spectrum of sample 1#;

[0022] Figure 4 It is the infrared spectrum (2.5-25 μm) spectrum of sample 1#;

[0023] Figure 5 This is the thermogravimetric analysis spectrum of sample 1#;

[0024] Figure 6 Sample 1# and KH 2 PO 4 Second harmonic signal diagram for samples in the range of 105 to 150 μm;

[0025] Figure 7 This is the second harmonic phase matching diagram of sample 1# in the 1.064μm band.

[0026] Figure 8 This is the birefringence test chart of sample 1# in the 546nm band. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0028] In the following examples, unless otherwise specified, raw materials, products or process technologies are all conventional commercial products or conventional processing technologies in the art.

[0029] Embodiment 1:

[0030] Hydrothermal synthesis of samples

[0031] A cerium source, a tellurium source, a molybdenum source, a fluorine source (using 40wt% hydrofluoric acid) and water are mixed in a certain proportion to form a starting raw material, and the mixture is sealed in a hydrothermal reactor with a polytetrafluoroethylene liner, and the temperature is raised to the crystallization temperature. After a period of constant temperature, the temperature of the reaction system is slowly lowered to room temperature at a certain rate, and the mixture is filtered and washed to obtain transparent block-shaped tellurium molybdate crystals.

[0032] The relationship between the type and ratio of raw materials in the initial mixture, crystallization temperature, crystallization time and sample number is shown in Table 1.

[0033] Table 1 Correspondence between samples, raw materials and synthesis conditions

[0034]

[0035] Example 2

[0036] Crystal structure analysis

[0037] The structures of samples 1# to 6# prepared in the above Example 1 were analyzed by single crystal X-ray diffraction and powder X-ray diffraction methods.

[0038] The single crystal X-ray diffraction test was carried out on a D8 VENTURE CMOS X-ray single crystal diffractometer from Bruker, Germany. The crystal size is 0.12×0.07×0.06mm 3 ; The data collection temperature is 293K, and the diffraction light source is graphite monochromatized Mo-Kα rays The scanning mode was ω; the data were processed for absorption correction using the Multi-Scan method. The structure analysis was completed using the SHELXTL-97 program package; the positions of heavy atoms were determined using the direct method, and the coordinates of the remaining atoms were obtained using the difference Fourier synthesis method; the F-based 2 The full-matrix least-squares method was used to refine the coordinates of all atoms and the anisotropic thermal parameters.

[0039] The powder X-ray diffraction test was carried out on a Bruker D8 X-ray powder diffractometer from Bruker, Germany. The test conditions were a fixed target monochromatic light source Cu-Kα, a wavelength The voltage and current are 40 kV / 20 A, the slits DivSlit / RecSlit / SctSlit are 2.00 deg / 0.3 mm / 2.00 deg respectively, the scanning range is 5 to 70°, and the scanning step is 0.02°.

[0040] Among them, the single crystal X-ray diffraction test results show that samples 1# to 6# have the same chemical formula and crystal structure, and the chemical formula is Mo(H 2 O)Te 2 O 7 , molecular weight is 481.16, belongs to tetragonal system, its space group is I-4, unit cell parameters are α=β=γ=90°,Z=8,the unit cell volume is

[0041] Take sample 1# as a typical example, its crystal structure data is α=β=γ=90°,Z=8,the unit cell volume is Its crystal structure is Figure 1 shown.

[0042] The powder X-ray diffraction test results show that in the powder X-ray diffraction spectra of samples 1# to 6#, the peak positions of each sample are exactly the same, but the peak intensities are slightly different.

[0043] Take sample 1# as a typical example. Figure 2 shown. Figure 2The spectrum obtained by X-ray diffraction test after sample 1# in (a) was ground into powder is similar to Figure 2 In (b), the X-ray diffraction pattern obtained by crystal structure simulation is analyzed based on its single crystal X-ray diffraction data. The peak position and peak intensity are consistent, indicating that the obtained sample is of high purity.

[0044] Example 3

[0045] UV diffuse reflectance spectrum test

[0046] The diffuse reflectance absorption spectrum test of sample 1# was conducted on a Cary 5000 UV-visible-near infrared spectrophotometer from Agilent Technologies, USA. Figure 3 As shown, the compound has a wide optical transmission range and an optical band gap of 3.39 eV.

[0047] Example 4

[0048] Infrared spectrum test

[0049] The infrared spectrum test of sample 1# was conducted on a Nicolet iS10 Fourier infrared spectrometer from Thermo Fisher Scientific Inc., USA. The results are as follows Figure 4 As shown, the compound has a wide optical transmittance range.

[0050] Example 5

[0051] Thermogravimetric testing

[0052] The thermogravimetric test of sample 1# was conducted on a Netzsch STA 409PC thermogravimetric analyzer manufactured by Netzsch Equipment Manufacturing Co., Ltd., Germany. The results are shown in the figure below. Figure 5 As shown, the compound can be stable up to 240°C and has good thermal stability.

[0053] Example 6

[0054] Powder frequency doubling test experiment and results

[0055] The specific experiment of powder frequency doubling test of sample 1# is as follows: the laser with a wavelength of 1064nm generated by Q-switched Nd:YAG solid laser is used as the fundamental frequency light to irradiate the tested crystal powder, the generated second harmonic is detected by photomultiplier tube, and the harmonic intensity is displayed by oscilloscope. 2 PO 4 The crystals were ground separately and sieved with standard sieves to obtain crystals of different particle sizes, with the particle size ranges being less than 26, 26-50, 50-74, 74-105, 105-150, 150-200, and 200-280 μm. The trend of the frequency-doubled signal intensity changing with the particle size was observed to determine whether phase matching could be achieved. Under the same test conditions, the sample was compared with KH2 PO 4 The second harmonic intensity generated by the sample can be used to obtain the relative size of the sample's frequency doubling effect.

[0056] The test results show that the compound tellurium molybdate crystal has a large frequency doubling effect. Under 1064nm wavelength laser irradiation, the frequency doubling signal intensity is higher than that of the control sample KH 2 PO 4 5.4 times of the crystal (such as Figure 6 ), which can achieve type I phase matching (such as Figure 7 ).

[0057] Example 7

[0058] Birefringence test experiment and results

[0059] Crystal Mo(H 2 O)Te 2 O 7 The birefringence was measured using a polarizing microscope (ZEISS AxioScope.A1) equipped with a Berek compensator. The wavelength of the light source was 546 nm. The birefringence was calculated using the following formula:

[0060] ΔR=|Ne–No|×T=Δn×T

[0061] Where ΔR represents the optical path difference, Δn represents the birefringence, and T is the crystal thickness. The positive and negative rotations of the compensation will produce relative delays. The boundaries between the first-order, second-order, and third-order interference colors are clear, so the relative error is small. In order to improve the accuracy of birefringence, the present invention selects transparent flake Mo (H 2 O)Te 2 O 7 Crystals are measured.

[0062] The test results show that the compound tellurium molybdate crystal exhibits strong optical anisotropy, and the birefringence at 546nm reaches 0.53 (such as Figure 8 ), which is significantly larger than the birefringence value of all commercially available birefringent crystals.

[0063] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A tellurium molybdate birefringent crystal material, characterized in that: Its chemical formula is Mo(H2O)Te2O7, it belongs to the tetragonal system, its space group is I-4, and its unit cell parameters are α=β=γ=90°,Z=8,the unit cell volume is 2. The tellurium molybdate birefringent crystal material according to claim 1, characterized in that: The unit cell parameters of the crystal material are α=β=γ=90°,Z=8,the unit cell volume is 3. The method for preparing the tellurium molybdate birefringent crystal material according to claim 1 or 2, characterized in that: Firstly, a cerium source, a tellurium source, a molybdenum source, a fluorine source and water are mixed to form an initial mixed raw material, and then placed under sealed hydrothermal conditions for reaction and crystallization to finally obtain the target product.

4. The method for preparing the tellurium molybdate birefringent crystal material according to claim 3, characterized in that: The cerium source is cerium dioxide; the tellurium source is tellurium dioxide; and the molybdenum source is molybdenum trioxide.

5. The method for preparing the tellurium molybdate birefringent crystal material according to claim 3, characterized in that: The fluorine source is hydrofluoric acid.

6. The method for preparing the tellurium molybdate birefringent crystal material according to claim 3, characterized in that: In the initial mixed raw materials, the molar ratio of cerium element, tellurium element, molybdenum element and fluorine element is 1: (0.5-50): (0.5-20): (0.5-50).

7. The method for preparing the tellurium molybdate birefringent crystal material according to claim 6, characterized in that: In the initial mixed raw materials, the molar ratio of cerium element, iodine element, fluorine element and sulfuric acid is 1:(1-20):(1-10):(2-20).

8. The method for preparing the tellurium molybdate birefringent crystal material according to claim 3, characterized in that: The hydrothermal temperature is 150-230°C and the crystallization time is not less than 24 hours.

9. The use of the tellurium molybdate birefringent crystal material according to claim 1 or 2, characterized in that: The crystal material is used in frequency doubling generators, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

10. The use of the tellurium molybdate birefringent crystal material according to claim 1 or 2, characterized in that: This crystal material is used for modulation of polarized light.

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