A method for preparing a diamond-type halide mid-infrared nonlinear optical crystal
By controlling the high-temperature solid-state reaction of diamond-type halides under vacuum conditions, high-purity CuAlCl4 and CuAlBr4 crystals were prepared, solving the problem of low purity in existing technologies and achieving efficient mid- and far-infrared nonlinear optical performance.
Patent Information
- Application Number
- CN202510340612.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-21
- Publication Date
- 2025-12-16
- Estimated Expiration
- 2045-03-21
AI Technical Summary
Existing methods for preparing diamond-type halides require stringent conditions, result in low product purity, and make it difficult to obtain high-purity CuAlCl4 and CuAlBr4 crystals.
High-temperature solid-state spontaneous reaction was carried out under vacuum conditions. By controlling the reaction temperature and cooling rate and setting the reaction time, side reactions were avoided, and high-purity CuAlCl4 and CuAlBr4 crystals were prepared.
The prepared CuAlCl4 and CuAlBr4 crystals have a purity of over 99%, wide band gaps of 4.28 eV and 4.09 eV respectively, and their light transmission area covers the mid- and far-infrared atmospheric window, making them suitable for laser devices in the mid- and far-infrared range.
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Figure CN120138771B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a kind of far infrared nonlinear optical crystal of diamond type halide and preparation method, the field of infrared nonlinear optical crystal material. BACKGROUND
[0002] Mid-far infrared nonlinear optical material is widely used in military fields such as visual communication, laser blinding and laser guidance, and the demand for mid-far infrared material is increasing. Diamond type halide has become an ideal candidate material due to its excellent structural characteristics and nonlinear optical performance. Traditional nonlinear optical crystals are mostly two-dimensional materials, and the preparation process is complex and impurities are easily produced, which affects the performance of the crystal. In order to overcome this problem, researchers have begun to focus on CuAlX4 (X=Cl or Br) crystals in diamond type halide. This type of crystal has good light transmission performance, especially in the wide light transmission range from visible light to infrared band, which makes it have great potential in infrared laser applications. Traditional diamond type halide is synthesized by high temperature solid phase, and the reaction temperature is less than 250℃. However, the reaction conditions of the traditional method are harsh, and the product contains impurities from side reactions, so the purity is low. Therefore, it is very important to develop an efficient and controllable preparation method to obtain high-purity diamond type halide (CuAlCl4 and CuAlBr4) crystals for promoting the application of far infrared nonlinear optical crystals. SUMMARY
[0003] The present application is to solve the technical problems of harsh conditions and low product purity of the existing preparation method of diamond type halide, and to provide a preparation method of diamond type halide mid-far infrared nonlinear optical crystal.
[0004] The preparation method of diamond type halide mid-far infrared nonlinear optical crystal of the present application is carried out according to the following steps:
[0005] I. The Cu source, Al source and X source are weighed according to the stoichiometric ratio of diamond type halide CuAlX4, wherein X is Cl or Br; the Cu source, Al source and X source are ground and mixed to obtain raw powder;
[0006] II. The raw powder is placed in a crucible, and the crucible is placed in a tube furnace. The tube furnace is sealed, and vacuumed to a vacuum degree less than or equal to 0.1 MPa;
[0007] III. The tube furnace is heated at a heating rate of 0.3-1℃ / min to 90-190℃ for 45-50h for solid phase reaction, and then cooled at a cooling rate of 0.1-0.2℃ / min to obtain diamond type halide mid-far infrared nonlinear optical crystal.
[0008] Further, the particle size of the raw powder in step I is less than 50 microns.
[0009] Further, X in step one is Cl, the Cu source is cuprous chloride, the Al source is aluminum chloride, and the diamond type halide obtained is CuAlCl4.
[0010] Further, X in step one is Cl, and the solid phase reaction in step three is at 190-200℃. Too high or too low a temperature can easily result in impurities.
[0011] Further, X in step one is Br, the Cu source is cuprous bromide, the Al source is aluminum bromide, and the diamond type halide obtained is CuAlBr4.
[0012] Further, X in step one is Br, and the solid phase reaction in step three is at 90-100℃. Too high or too low a temperature can easily result in impurities.
[0013] Principles and advantages of the present application:
[0014] 1. The present application carries out high temperature solid phase spontaneous reaction under vacuum conditions, controls the thermodynamics of the solid phase reaction by changing the reaction temperature, makes CuAlCl4 and CuAlBr4 overcome the reaction energy barrier, controls the crystal growth kinetics by setting the reaction time and the cooling rate, makes the conversion rate of the reactants synthesizing CuAlCl4 and CuAlBr4 crystals high, thereby avoiding the generation of side reactions, and the obtained crystals have high purity. The purity of the CuAlCl4 and CuAlBr4 crystals synthesized by the present application reaches more than 99%.
[0015] 2. The infrared nonlinear optical crystals CuAlCl4 and CuAlBr4 prepared by the present application respectively have a wide band gap of 4.28 eV and 4.09 eV, and the light transmission region covers the two key mid-infrared atmospheric windows of 3-5 μm and 8-12 μm without strong absorption caused by chemical bond vibration, and is suitable for mid and far infrared range applications.
[0016] 3. The infrared nonlinear optical crystals CuAlCl4 and CuAlBr4 prepared by the present application also have a second harmonic generation effect, and the second harmonic response is 0.09×AGS and 0.38×AGS respectively, which provides a new material selection for atmospheric sensing, laser blinding, laser guidance, etc., and therefore can be applied to laser frequency converters, optical parametric oscillators, infrared communication and other types of devices with high power infrared laser devices. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 is a crystal structure diagram of CuAlCl4 prepared in Example 1.
[0018] Figure 2 is a whole structure diagram of CuAlCl4 prepared in Example 1.
[0019] Figure 3 CuAlCl4polycrystalline X-ray powder diffraction pattern prepared for Example 1 compared with the theoretical value.
[0020] Figure 4 Optical band gap of CuAlCl4crystal prepared for Example 1.
[0021] Figure 5 Nonlinear intensity of CuAlCl4crystal prepared for Example 1.
[0022] Figure 6 Infrared spectrum of CuAlCl4crystal prepared for Example 1.
[0023] Figure 7 XRD pattern of CuAlCl4mid-infrared nonlinear optical crystal prepared for Example 2.
[0024] Figure 8 CuAlCl4polycrystalline X-ray powder diffraction pattern prepared for Examples 1, 2 and Comparative Examples 1, 2 and 3.
[0025] Figure 9 Crystal structure of CuAlBr4prepared for Example 3.
[0026] Figure 10 Overall structure of CuAlBr4prepared for Example 3.
[0027] Figure 11 CuAlBr4polycrystalline X-ray powder diffraction pattern prepared for Example 3 compared with the theoretical value.
[0028] Figure 12 Optical band gap of CuAlBr4crystal prepared for Example 3.
[0029] Figure 13 Nonlinear intensity of CuAlBr4crystal prepared for Example 3.
[0030] Figure 14 Infrared spectrum of CuAlBr4crystal prepared for Example 3.
[0031] Figure 15 XRD pattern of CuAlBr4mid-infrared nonlinear optical crystal prepared for Example 4.
[0032] Figure 16 CuAlBr4polycrystalline X-ray powder diffraction pattern prepared for Examples 3, 4 and Comparative Examples 4, 5 and 6. DETAILED DESCRIPTION
[0033] The advantageous effects of the present application are verified with the following examples.
[0034] Example 1: The preparation method of the diamond type halide CuAlCl4 mid-infrared nonlinear optical crystal in this embodiment is carried out according to the following steps:
[0035] I. According to the stoichiometric ratio of the diamond type halide CuAlCl4, 1.9800 grams of cuprous chloride and 2.6668 grams of aluminum chloride are weighed; the cuprous chloride and the aluminum chloride are ground to a powder particle size of less than 50 microns, mixed, to obtain a raw material powder;
[0036] II. The raw material powder is placed in a crucible, and the crucible is placed in a tube furnace, the tube furnace is sealed, and vacuumized to a vacuum degree of 0.1 MPa;
[0037] III. The tube furnace is heated at a heating rate of 0.5 ℃ / min to 190 ℃ for 48 h for solid phase reaction, and then cooled at a cooling rate of 0.1 ℃ / min to 30 ℃, to obtain the diamond type halide CuAlCl4 mid-infrared nonlinear optical crystal.
[0038] Figure 1 is a crystal structure diagram of CuAlCl4 prepared in Example 1; Figure 2 is a whole structure diagram of CuAlCl4 prepared in Example 1. The CuAlCl4 mid-infrared nonlinear optical crystal prepared in this embodiment has a diamond-like structure, one Cu atom is coordinated with 4 Cl atoms to form a [CuCl4] tetrahedron, and one Al atom is also connected with 4 Cl atoms to form an [AlCl4] tetrahedron. Among them, each adjacent tetrahedron is connected by sharing Cl atoms, forming a bridge connecting two tetrahedral units together, forming a three-dimensional spatial network structure of pyramid stacking; adjacent [CuCl4] and [AlCl4] tetrahedrons form a considerable number of cation vacancies, and the vacancy number of the CuAlCl4 crystal is equal to the number of tetrahedrons; the Cl ion radius (Cl - ), and the vacancy radius is This causes the CuAlCl4 to form a diamond-like structure with defects. The chemical formula of the tetrachloroaluminum copper crystal is CuAlCl4, and the molecular weight is 228.33.
[0039] Figure 3 is a comparison diagram of the CuAlCl4 polycrystal X-ray powder diffraction pattern prepared in Example 1 and the theoretical value. From Figure 3It can be seen that the XRD pattern of the diamond type halide CuAlCl4 product prepared in Example 1 is basically consistent with the theoretically calculated pattern, and there is no impurity diffraction peak, and the purity reaches more than 99%. It shows that the purity of CuAlCl4 prepared in Example 1 is high, and the crystal system of the copper aluminum chloride crystal is tetragonal, non-central symmetric structure, space group is P-42c (No. 112), cell parameters α = β = γ = 90°, Z = 2, unit cell volume
[0040] Using ultraviolet-visible diffuse reflectance spectroscopy test, the light transmission wave band and the cut-off wavelength of the compound are judged, and Cary5000 instrument (wavelength accuracy: ± 0.08nm) is used to collect the diffuse reflectance data of the material in the wavelength range of 200-2500nm. With the help of Kubelka-Munk equation: F (R) = (1-R ∞ )2 / 2R ∞ = K / S (R ∞ is the reflectance, K is the absorption coefficient, and S is the scattering coefficient), the "integrating sphere" data is converted into absorption data, and the diffuse reflectance spectrum is drawn, so as to calculate the experimental band gap width of the material. Figure 4 is the optical band gap diagram of the CuAlCl4 crystal prepared in Example 1; from Figure 4 It can be seen that the crystal CuAlCl4 has a band gap of 4.28eV.
[0041] The powder frequency doubling effect test is implemented on the basis of the theory proposed by Kurtz-Perry. Since the second harmonic (SHG) response is strongly dependent on the sample size particle size, the powder sample is ground and then sieved to the same particle size. The frequency doubling effect measurement is completed by running an ultrashort pulse laser at a wavelength of 2090nm, and the frequency doubling signal is recorded by a photomultiplier tube. In order to compare, the standard AgGaS2 (AGS) powder is sieved to the same particle size range for reference comparison. Figure 5 is the nonlinear intensity diagram of the CuAlCl4 crystal prepared in Example 1; from Figure 5 It can be seen that the second harmonic response of the CuAlCl4 crystal is 0.09x AGS.
[0042] Figure 6 is the infrared spectrum of the CuAlCl4 crystal prepared in Example 1; from Figure 6 It can be seen that CuAlCl4 has a light transmission range of 2.5μm-16.10μm, and the light transmission region covers two key mid-infrared atmospheric windows of 3-5μm and 8-12μm without strong absorption caused by chemical bond vibration, which is suitable for mid-infrared range application.
[0043] Example 2: The difference between this example and Example 1 is that the solid phase reaction temperature in step three is 200°C, and other steps and parameters are the same as those in Example 1, to obtain a diamond type halide CuAlCl4 mid-infrared nonlinear optical crystal.
[0044] Figure 7 The X-ray powder diffraction pattern of CuAlCl4 polycrystal prepared in this example 2 is compared with the theoretical value. From Figure 7 It can be seen that when the solid phase reaction temperature is 200°C, the XRD pattern of the target product is basically consistent with the theoretical calculation pattern, and there is no impurity diffraction peak, which indicates that the purity is high, and the purity reaches more than 99%.
[0045] Comparative Example 1: The difference between this comparative example and Example 1 is that the solid phase reaction temperature in step three is 210°C, and other steps and parameters are the same as those in Example 1, to obtain a diamond type halide CuAlCl4 mid-infrared nonlinear optical crystal.
[0046] Comparative Example 2: The difference between this comparative example and Example 1 is that the solid phase reaction temperature in step three is 180°C, and other steps and parameters are the same as those in Example 1, to obtain a diamond type halide CuAlCl4 mid-infrared nonlinear optical crystal.
[0047] Comparative Example 3: The difference between this comparative example and Example 1 is that in step two, the operation of vacuumizing is omitted, and other steps and parameters are the same as those in Example 1, to obtain a diamond type halide CuAlCl4 mid-infrared nonlinear optical crystal.
[0048] Figure 8 The X-ray powder diffraction pattern of CuAlCl4 polycrystal prepared in this example 2 is compared with the theoretical value. From Figure 8It can be seen that when the temperature is lower than 190°C, the diffraction peak of the unreacted reactant CuCl appears; when the temperature is higher than 200°C, the diffraction peak of the oxidized impurity CuCl2 appears; when the vacuum operation is omitted, the diffraction peaks of the impurities CuCl and CuCl2 appear. The diamond type halide CuAlCl4 prepared in Comparative Examples 1 and 2 contains unreacted reactant CuCl or oxidized impurity CuCl2. Only the difference in temperature leads to a significant decrease in the purity of the product. It is said that the optimal reaction temperature range of the reaction is 190°C to 200°C. Below the optimal reaction temperature range, the reaction is incomplete, and the remaining portion is CuCl; above the optimal reaction temperature range, a new oxidation reaction occurs, generating the oxidized impurity CuCl2. Comparative Example 3 is carried out under normal pressure by solid phase reaction, the reaction is incomplete, and the remaining portion is CuCl, and the oxidation reaction also occurs under normal pressure, generating the oxidized impurity CuCl2, and the purity of the finally prepared CuAlCl4 is low. Through Comparative Examples 1, 2 and 3, it is shown that the key parameters for preparing the diamond type halide CuAlCl4 by solid phase reaction are temperature and vacuum conditions.
[0049] Example 3: The preparation method of the diamond type halide CuAlBr4 mid-infrared nonlinear optical crystal in this example is carried out according to the following steps:
[0050] I. According to the stoichiometric ratio of the diamond type halide CuAlBr4, 2.8690 grams of cuprous bromide and 5.3338 grams of aluminum bromide are weighed; the cuprous bromide and the aluminum bromide are ground to a powder particle size of less than 50 microns, mixed, and the raw material powder is obtained;
[0051] II. The raw material powder is placed in a crucible, and the crucible is placed in a tube furnace, the tube furnace is sealed, and vacuumized to a vacuum degree of 0.1 MPa;
[0052] III. The tube furnace is heated at a heating rate of 0.5°C / min to 90°C and kept for 48h for solid phase reaction, and then cooled at a cooling rate of 0.1°C / min to 30°C, to obtain the diamond type halide CuAlBr4 mid-infrared nonlinear optical crystal.
[0053] Figure 9 is the crystal structure diagram of CuAlBr4 prepared in Example 3; Figure 10The overall structure of CuAlBr4 prepared in Example 3 is shown in the figure. The structure of the far infrared nonlinear optical crystal in CuAlBr4 prepared in this example is that one Cu atom is coordinated with four Br atoms to form a [CuBr4] tetrahedron, and one Al atom is also connected with four Br atoms to form an [AlBr4] tetrahedron. Among them, each adjacent tetrahedron is connected by sharing Br atoms, forming a bridge that connects two tetrahedral units together, forming a three-dimensional spatial network structure of pyramid stacking; adjacent [[CuBr4] and [AlBr4] tetrahedrons form a considerable number of cation vacancies, and the vacancy number of CuAlBr4 crystal is equal to the number of tetrahedrons; Br ions (Br - ) have a radius of and a vacancy radius of This leads to the formation of a diamond-like structure with defects in CuAlBr4. The chemical formula of the tetrabromoaluminum copper crystal prepared in this example is CuAlBr4, and the molecular weight is 410.13.
[0054] Figure 11 The polycrystalline X-ray powder diffraction pattern of CuAlBr4 prepared in Example 3 is compared with the theoretical value as shown in the figure. As can be seen from the figure, the XRD pattern of the diamond-type halide CuAlBr4 product prepared in Example 3 is basically consistent with the theoretically calculated pattern, and there is no impurity diffraction peak, indicating that the purity of CuAlBr4 is high, and the purity reaches more than 99%. And the tetrabromoaluminum copper crystal prepared in this example belongs to tetragonal crystal system, non-centrosymmetric structure, space group P-42c (No. 112), cell parameters α = β = γ = 90°, Z = 2, unit cell volume
[0055] The optical band gap diagram of the CuAlBr4 crystal prepared in Example 3 is obtained by the same method as in Example 1, as shown in Figure 12 From Figure 12 it can be seen that the crystal CuAlBr4 has a band gap of 4.09 eV.
[0056] The nonlinear intensity diagram of the CuAlBr4 crystal prepared in Example 3 is obtained by the same method as in Example 1, as shown in Figure 13 From Figure 13 it can be seen that the second harmonic response of CuAlBr4 crystal is 0.38 x AGS.
[0057] Figure 14 is the infrared spectrum of the CuAlBr4 crystal prepared in Example 3; from Figure 14It can be seen that CuAlBr4 has a light transmission range of 2.5 μm to 20.38 μm. The light transmission range covers the two key mid-infrared atmospheric windows of 3-5 μm and 8-12 μm without strong absorption caused by chemical bond vibration, and is suitable for mid-infrared range application.
[0058] Example 4: This example is different from Example 3 in that the temperature of the solid phase reaction in step three is 100°C, and the other steps are the same as those of Example 3, to obtain the diamond type halide CuAlBr4 mid-infrared nonlinear optical crystal.
[0059] Figure 15 The X-ray powder diffraction pattern of the CuAlBr4 polycrystal prepared in Example 4 is compared with the theoretical value. It can be seen from Figure 15 It can be seen that when the temperature is 100°C, the XRD pattern of the diamond type halide CuAlBr4 product is basically consistent with the theoretically calculated pattern, without impurity diffraction peaks, and the purity reaches more than 99%.
[0060] Comparative Example 4: This comparative example is different from Example 3 in that the temperature of the solid phase reaction in step three is 110°C, and the other steps and parameters are the same as those of Example 3, to obtain the diamond type halide CuAlBr4 mid-infrared nonlinear optical crystal.
[0061] Comparative Example 5: This comparative example is different from Example 3 in that the temperature of the solid phase reaction in step three is 80°C, and the other steps and parameters are the same as those of Example 3, to obtain the diamond type halide CuAlBr4 mid-infrared nonlinear optical crystal.
[0062] Comparative Example 6: This comparative example is different from Example 1 in that the vacuum extraction operation in step two is omitted, and the other steps and parameters are the same as those of Example 3, to obtain the diamond type halide CuAlBr4 mid-infrared nonlinear optical crystal.
[0063] Figure 16 The X-ray powder diffraction pattern of the CuAlBr4 polycrystal prepared in Examples 3, 4 and Comparative Examples 4, 5 and 6 is compared. It can be seen from Figure 16It can be seen that when the temperature is below 90℃, the diffraction peak of unreacted CuBr appears; when the temperature is above 100℃, the diffraction peak of oxidized impurity CuBr2 appears; when the vacuum operation is omitted, the diffraction peaks of CuBr and CuBr2 impurities appear. The diamond type halide CuAlBr4 prepared in Comparative Examples 4 and 5 contains unreacted CuBr or oxidized impurity CuBr2. Only the difference in temperature leads to a significant decrease in the purity of the product. Therefore, the optimal reaction temperature range is 90-100℃. Below the optimal reaction temperature range, the reaction is incomplete, leaving a portion of CuBr; above the optimal reaction temperature range, a new oxidation reaction occurs, generating the oxidized impurity CuBr2. In Comparative Example 6, the solid phase reaction is carried out under normal pressure, the reaction is incomplete, leaving a portion of CuBr, and an oxidation reaction also occurs under normal pressure, generating the oxidized impurity CuBr2, resulting in a decrease in the purity of the finally prepared CuAlBr4. Comparative Examples 4, 5 and 6 show that in the preparation of the diamond type halide CuAlBr4, the vacuum condition and the solid phase reaction temperature are key parameters for synthesizing high-purity CuAlBr4.
Claims
1. A method for producing a diamond type halide mid-infrared nonlinear optical crystal, characterized by, The method is performed according to the following steps: I. According to the stoichiometric ratio of the diamond type halide CuAlX4, the Cu source, the Al source and the X source are weighed; wherein X is Cl or Br; the Cu source, the Al source and the X source are ground and mixed to obtain a raw material powder; II. The raw material powder is placed in a crucible, and the crucible is placed in a tube furnace; the tube furnace is sealed, and vacuumized to a vacuum degree less than or equal to 0.1 MPa; III. In step I, X is Cl; the tube furnace is heated to 190-200 DEG C at a heating rate of 0.3-1 DEG C / min for 45-50 h for solid phase reaction; then cooled at a cooling rate of 0.1-0.2 DEG C / min to obtain a diamond type halide mid-infrared nonlinear optical crystal; In step I, X is Br; the tube furnace is heated to 90-100 DEG C at a heating rate of 0.3-1 DEG C / min for 45-50 h for solid phase reaction; then cooled at a cooling rate of 0.1-0.2 DEG C / min to obtain a diamond type halide mid-infrared nonlinear optical crystal.
2. A method of preparing a diamond type halide mid-infrared nonlinear optical crystal according to claim 1, characterized in that, The particle size of the raw material powder is less than 50 microns.
3. A method of producing a diamond type halide mid-infrared nonlinear optical crystal according to claim 1 or 2, characterized in that, In step I, X is Cl, the Cu source is cuprous chloride, and the Al source is aluminum chloride.
4. A method for preparing a far-infrared nonlinear optical crystal of diamond-type halide according to claim 1 or 2, characterized in that, In step I, X is Br, the Cu source is cuprous bromide, and the Al source is aluminum bromide.