Nonlinear optical crystal with fluorescent magnetism as well as preparation method and application of nonlinear optical crystal

Abstract

The invention belongs to the field of nonlinear optical crystal materials, and particularly relates to a nonlinear optical crystal and a preparation method and application thereof. The chemical formula of the nonlinear optical crystal is Zn4EuO (BO3) 3, the nonlinear optical crystal belongs to a monoclinic system, the space group is Cm, and the cell parameters are that alpha is equal to 90 degrees, beta is equal to 100.193 degrees, and gamma is equal to 90 degrees. The crystal disclosed by the invention has good SHG performance and fluorescence performance at the same time; a frequency doubling signal of the crystal is about 4 times that of a KDP sample; the fluorescent material emits red light, the service life of the Eu (5D0) state of the fluorescent material is about 1.43 milliseconds under the conditions that lambda ex and um are equal to 464 and 610 nm, and the fluorescent material is a potential luminescent material emitting red light. In addition, the optical band gap of the crystal is 3.46 eV, and the crystal has extremely high thermal stability which can reach 1100 DEG C.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nonlinear optical crystal materials, and particularly relates to a nonlinear optical crystal with fluorescent magnetism and a preparation method and application thereof. BACKGROUND

[0002] Nonlinear optical crystal materials (NLO) as an important class of optoelectronic information functional materials have attracted more and more research attention in material science. However, how to obtain NLO materials with large nonlinear optical coefficient, wide transmission band and high laser damage threshold is still a major challenge. Among numerous candidate materials, borate crystals are considered as ideal NLO systems due to their wide band gap, low two-photon absorption probability and high laser damage threshold, which are conducive to realizing strong nonlinear optical effect. Boron atoms can form linear [BO2], triangular [BO3] and tetrahedral [BO4] groups, and connect them in different ways to form a boron-oxygen anion skeleton with rich structures. Further introducing structural units with non-centrosymmetric characteristics, such as d 0 transition metal, high-polar d 10 cation, and cation containing stereochemically active lone pair of electrons into the skeleton can significantly enhance the second-order nonlinear optical response of the material, and excellent second harmonic generation (SHG) performance can be obtained. Representative crystals include KBe2BO3F2 (KBBF), Sr2Be2B2O7 (SBBO), LiB3O5 (LBO) and β-BaB2O4 (β-BBO).

[0003] In practical applications, nonlinear optical materials are often in a high-power laser environment. The fluorescence performance of the material not only reflects the electronic structure and defect state of the material, but also is closely related to the laser damage threshold. Excellent fluorescence characteristics often mean high radiation recombination efficiency and low non-radiative quenching, which helps to improve the optical-thermal stability and laser tolerance of the material. Therefore, developing new NLO materials with strong SHG effect and good fluorescence performance at the same time has important practical significance for promoting the development of high-performance integrated photonics devices and solid-state laser technology. SUMMARY

[0004] The purpose of the present application is to provide a nonlinear optical crystal with fluorescent magnetism and a preparation method and application thereof, which has good SHG performance and fluorescence performance at the same time.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The application provides a nonlinear optical crystal with fluorescent magnetism, the chemical formula of the nonlinear optical crystal with fluorescent magnetism is Zn4EuO(BO3)3, belongs to a monoclinic system, a space group is Cm, and cell parameters are Alpha is 90 degrees, beta is 100.193 degrees, and gamma is 90 degrees.

[0007] The asymmetric unit of the nonlinear optical crystal with fluorescent magnetism provided by the application comprises one Eu atom, two Zn atoms, two BO3 groups and one oxygen anion, wherein the Eu atom, the oxygen anion and one BO3 group are located on a mirror surface.

[0008] Further, in the nonlinear optical crystal with fluorescent magnetism, Zn, Eu, B and O are coordinated to form ZnO8 polyhedron, ZnO6 octahedron, EuO6 octahedron and BO3 triangular plane structure; the ZnO8 polyhedron and the ZnO6 octahedron are connected with each other through a shared edge and a vertex, to form a three-dimensional anion skeleton with 4-membered ring and 7-membered ring channels; the 7-membered ring channel is connected with the BO3 triangular plane, to form a Zn4B3 seven-membered ring, and the Eu 3+ is filled in the Zn4B3 seven-membered ring channel; the 4-membered ring channel contains the BO3 group; and all the BO3 triangular planes are arranged in the ab plane.

[0009] Further, the ZnO8 polyhedron is formed by coordination of the Zn atom and five BO3 groups, wherein three BO3 groups are coordinated in a bidentate chelation manner; the ZnO6 octahedron is formed by coordination of the Zn atom and five BO3 groups and one oxygen anion; and the EuO6 octahedron is formed by coordination of the Eu atom and four BO3 groups and two oxygen anions.

[0010] Further, the bond length of the Zn-O bond in the ZnO8 polyhedron and the ZnO6 octahedron is the bond length of the Eu-O bond in the EuO6 octahedron is the bond length of the B-O bond in the BO3 triangular plane is the bond angle of the O-B-O bond is 117.9-122.4 degrees.

[0011] Further, the nonlinear optical crystal with fluorescent magnetism has a significant endothermic peak at 1133 DEG C, indicating that the nonlinear optical crystal with fluorescent magnetism has a high thermal stability of up to 1100 DEG C. The crystal is a wide-bandgap semiconductor, and the optical band gap is 3.46 eV. The effective magnetic distance (mu e ff ) of the crystal is 3.47 mu B , and the shortest Eu···Eu distance is indicating that the magnetic exchange interaction is very weak. The nonlinear optical crystal of the present application shows a series of characteristic emission peaks between 550-750 nm by Eu doping. These emission peaks are mainly derived from Eu 3+ ions 5 D0→ 7 F 0-4 transition: 578 nm( 5 D0→ 7 F0), 587, 592 and 596 nm( 5 D0→ 7 F1), 610, 620, 626 and 629 nm( 5 D0→ 7 F2), 647 and 651 nm( 5 D0→ 7 F3), 691, 706 and 709 nm( 5 D0→ 7 F4), wherein the emission peaks near 647 and 651 nm are weak. The strongest emission peak is at 610 nm( 5 D0→ 7 F2), which belongs to an electric dipole transition, and theoretically, 5 D0→ 7 F 0,2,4 the electric dipole transition of D0→ F should be strictly forbidden, and only low-symmetry point groups can realize the electric dipole transition, and the Cm space group is a low-symmetry space group, so the crystal emits red light, and under the test conditions of λex,em= 464, 610 nm, the fluorescence lifetime of Eu( 5 D0) state is 1.43 ms.

[0012] The present application also provides a preparation method of the nonlinear optical crystal with fluorescent magnetism, comprising the following steps:

[0013] The zinc source, the boron source and the europium source are prepared according to the molar ratio (6-8) : (10-14) : 1, mixed and ground, the mixed and ground mixture is put into a crucible for one-time heating, and after being kept warm for 24 h, the mixture is subjected to two-time heating, and after the mixture is melted to be transparent, the mixture is cooled, the mixture spontaneously crystallizes during the cooling process, and after the crystallization is completed, the mixture is naturally cooled to room temperature, and the nonlinear optical crystal with fluorescent magnetism is obtained.

[0014] Further, the zinc source is selected from any one of zinc oxides and zinc carbonates; the boron source is selected from boric acid and boron oxide; and the europium source is Eu2O3.

[0015] Further, the specific process of the one-time heating is to heat to 450-500℃ at a rate of 60-65℃ / h.

[0016] Furthermore, the specific process of the secondary heating is as follows: heating to 1170-1200℃ at a rate of 50-70℃ / h.

[0017] Furthermore, the specific cooling process is as follows: cooling to 1000℃ at a rate of 3-5℃ / h.

[0018] The present invention also provides the application of the above-described nonlinear optical crystal with fluorescent magnetism or the nonlinear optical crystal with fluorescent magnetism prepared by the above-described preparation method in the preparation of nonlinear optical devices.

[0019] Compared with the prior art, the main advantages of the present invention are as follows:

[0020] The nonlinear optical crystal with fluorescent magnetism of this invention is a wide-bandgap semiconductor with an optical bandgap of 3.46 eV and extremely high thermal stability, reaching 1100℃; its harmonic harmonic signal is approximately four times that of the KDP sample. Furthermore, the crystal emits a red color, and under the condition λex,em = 464,610 nm, its Eu( 5 The lifetime of the D0 state is about 1.43 milliseconds, making it a potential luminescent material that emits red light. Attached Figure Description

[0021] Figure 1 The crystal structure diagram of the compound Zn4EuO(BO3)3 is shown.

[0022] Figure 2 The TG and DSC spectra of sample 1 are shown.

[0023] Figure 3 The infrared absorption spectrum of sample 1 is shown below.

[0024] Figure 4 The image shows the UV-Vis-NIR diffuse reflectance spectrum of sample 1.

[0025] Figure 5 The fluorescence emission spectrum of sample 1 at 10K (λex = 464 nm);

[0026] Figure 6 Eu( for sample 1) 5 Fluorescence lifetime diagram of the D0 state at λex,em = 464,610 nm;

[0027] Figure 7 The image shows the SHG signal of sample 1 at 1064nm.

[0028] Figure 8 The graph shows the relationship between the first harmonic effect and particle size of the sample.

[0029] Figure 9 The graph shows the χ² and χ⁻¹ vs. T values ​​for sample 1.

[0030] Figure 10 The effective magnetic moment (μ) of sample 1 e ff Curve showing the change with temperature. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0032] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0033] The sample crystals in this embodiment of the invention were synthesized using a high-temperature solid-state method.

[0034] Example 1

[0035] The preparation process of Sample 1 is as follows:

[0036] ZnCO3 (0.502 g, 4.0 mmol), H3BO3 (0.371 g, 6.0 mmol), and Eu2O3 (0.176 g, 0.5 mmol) were thoroughly ground and placed in a platinum crucible. The platinum crucible was then placed in a temperature-controlled muffle furnace and heated to 450 °C at a rate of 60 °C / h and maintained for 1 day. The muffle furnace was then heated to 1170 °C at a rate of 60 °C / h. When the muffle furnace was opened and a transparent melt was observed, the temperature was cooled to 1000 °C at a rate of 3 °C / h. The muffle furnace was then closed and allowed to cool naturally to room temperature to obtain a colorless, blocky compound.

[0037] Example 2

[0038] The preparation process of Sample 2 is as follows:

[0039] ZnO (0.244 g, 3.0 mmol), H3BO3 (0.432 g, 7.0 mmol), and Eu2O3 (0.176 g, 0.5 mmol) were thoroughly ground and placed in a platinum crucible. The platinum crucible was then placed in a temperature-controlled muffle furnace and heated to 470 °C at a rate of 65 °C / h and maintained for 1 day. The muffle furnace was then heated to 1175 °C at a rate of 60 °C / h. When the muffle furnace was opened and a transparent melt was observed, the temperature was cooled to 990 °C at a rate of 3 °C / h. The muffle furnace was then closed and allowed to cool naturally to room temperature to obtain a colorless, blocky compound.

[0040] Example 3

[0041] The preparation process of sample 3 is as follows:

[0042] ZnCO3 (0.439 g, 3.5 mmol), B2O3 (0.350 g, 5.0 mmol), and Eu2O3 (0.176 g, 0.5 mmol) were thoroughly ground and placed in a platinum crucible. The platinum crucible was then placed in a temperature-controlled muffle furnace and heated to 500°C at a rate of 65°C / h and maintained for 1 day. The muffle furnace was then heated to 1200°C at a rate of 60°C / h. When the muffle furnace was opened and a transparent melt was observed, the temperature was cooled to 1000°C at a rate of 3°C / h. The muffle furnace was then closed and allowed to cool naturally to room temperature to obtain a colorless, blocky compound.

[0043] Crystal structure analysis of samples 1-3

[0044] The structure of the sample crystal was analyzed using single-crystal X-ray diffraction.

[0045] Single-crystal X-ray diffraction tests were performed on a SuperNova diffractometer. The crystal was attached to the end of a flat glass wire with AB glue. Crystal diffraction data were obtained using Mo-Kα rays. Diffraction data were collected at 293 K using a SuperNova CCD with ω-2θ detection. After processing with CrysAlisPro reduction software, absorption correction was performed using Multi-Scan, and single-crystal analysis was conducted using SHELXTL-2017 or Olex2. Traditional crystal structure analysis methods were used to determine the types and positions of atoms in the crystal. F... 2 The full matrix least squares plane is used to refine all atomic coordinates and anisotropic parameters.

[0046] Single-crystal X-ray diffraction results show that the sample crystal has the chemical formula Zn4EuO(BO3)3, belongs to the monoclinic crystal system, and has the space group Cm; its unit cell parameters are... α = 90°, β = 100.193°, γ = 90°, its crystal structure is as follows: Figure 1 As shown. The compound Zn4EuO(BO3)3 has a complex three-dimensional anionic framework formed by the interconnection of metal cations, oxygen ions, and borate groups. The asymmetric unit of Zn4EuO(BO3)3 contains one Eu atom in the mirror position, two Zn atoms in the normal position, one BO3 group in the normal position, one BO3 group in the mirror position, and one oxygen anion in the mirror position. Two Zn atoms... 2+ Using different coordination modes, the octahedral Zn(1)O8 is formed by three BO3 groups in a bidentate chelate manner and two BO3 groups in a monodentate manner. Zn(2) forms a six-coordinate Zn(2)O6 octahedron with five BO3 groups and one oxygen anion. The bond length of the Zn-O bond ranges from [missing information]. Eu3+ It forms a six-coordinate octahedron by connecting the four O atoms and two oxygen anions on the four BO3 groups. The bond length of the Eu-O bond ranges from [value missing]. Both B(1) and B(2) atoms have a BO3 planar triangular configuration, and the bond length of the BO bond ranges from [value missing]. The bond angles of the OBO bonds range from 117.9(16) to 122.4(17)°. These bond lengths and angles are similar to those reported in related metal borates. Zn(1)O8 and Zn(2)O6 polyhedra are interconnected by sharing edges and vertices to form a three-dimensional anionic framework with 4-membered and 7-membered ring channels. The B(1)O3 group is located in the 4-membered ring channel, and the B(2)O3 group is interconnected with the 7-membered ring to form a new Zn4B3 7-membered ring. Eu 3+ It fills the pores of the Zn4B3 seven-membered ring. Furthermore, all BO3 groups are uniformly arranged in the ab plane.

[0047] Performance testing

[0048] (1) Thermogravimetric test

[0049] Thermogravimetric and differential scanning calorimetric analyses of sample 1 were performed on a STA-449F3 thermogravimetric analyzer, and the results are as follows: Figure 2 As shown. By Figure 2 It can be seen that the compound has a significant endothermic peak at 1133℃, indicating that the compound has thermal stability up to 1100℃.

[0050] (2) Infrared spectroscopy test

[0051] The infrared spectrum of sample 1 was measured on a VERTEX 70 Fourier transform infrared spectrometer, and the results are as follows: Figure 3 As shown. Figure 3 1170 and 916cm -1 The absorption peaks at 714, 589, and 473 cm⁻¹ are attributed to the asymmetric and symmetric stretching vibrations of the BO₃ group. -1 The absorption peak at that point is attributed to the bending vibration of the BO3 group.

[0052] (3) Ultraviolet-Visible-NearInfrared Diffuse Reflectance Spectroscopy Test

[0053] The UV-Vis-NIR diffuse reflectance spectra of sample 1 were measured using a Lambda 950 spectrophotometer, and the results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the compound is a wide bandgap semiconductor with an optical bandgap of 3.46 eV.

[0054] (4) Fluorescence spectroscopy test

[0055] Fluorescence spectroscopy of sample 1 was performed on an Edinburgh FLS-920 at a temperature of 10 K and an excitation wavelength of 464 nm. The results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the compound exhibits a series of characteristic emission peaks in the 550-750 nm range, and these emission peaks mainly originate from Eu. 3+ ion 5 D0→ 7 F 0-4 The leap: 578nm ( 5 D0→ 7 F0), 587, 592 and 596nm ( 5 D0→ 7 F1), 610, 620, 626 and 629nm 5 D0→ 7 F2), 647 and 651nm 5 D0→ 7 F3), 691, 706 and 709nm 5 D0→ 7 F4), with weaker emission peaks near 647 and 651 nm. 5 D0→ 7 The emission peak observed by F0 and in 5 D0→ 7 F 1-4 The observed split emission peaks prove Eu 3+ The ion occupies a site with low symmetry, consistent with the results of X-ray diffraction studies. The strongest emission peak is located at 610 nm. 5 D0→ 7 At point F2), it is an electric dipole transition, theoretically... 5 D0→ 7 F 0,2,4 Electric dipole transitions should be strictly prohibited; only low-symmetry point groups can achieve them. The Cm space group is a low-symmetry space group, therefore this compound emits red light. Under the test conditions of λex,em = 464,610 nm, Eu( 5 The fluorescence lifetime of the D0 state is 1.43 ms (e.g., Figure 6 (As shown). Therefore, this compound is a potential luminescent material that emits red light.

[0056] (5) Frequency doubling test experiment and results

[0057] The frequency harmonic testing experiment for sample 1 is as follows:

[0058] The powder second-order NLO effect test is based on the method summarized by Kurtz and Perry et al.: A 1064nm laser is generated using an Nd:YAG laser to irradiate the sample, and the resulting second harmonic intensity is compared with the second harmonic intensity of KDP or KTP samples tested under the same conditions. Furthermore, clean crystals of different particle sizes are screened, and the trend of their second harmonic intensity is tested to analyze whether the crystals can achieve phase matching, and finally, their actual SHG coefficients are determined.

[0059] Test results are as follows Figure 7 As shown, under 1064 nm wavelength laser irradiation, the overtone signal intensity of this compound is four times that of the KDP sample. Following the rules proposed by Kurtz and Perry, powders of different particle sizes sieved through a standard sieve were irradiated with a tunable Nd:YAG laser at a wavelength of 1064 nm. The trend of SHG signal variation with particle size was observed, and the resulting curves (as shown in the figure) were obtained. Figure 8 The characteristics shown are very consistent with the phase-matching behavior, indicating that the compound belongs to the type I phase-matching class.

[0060] (6) Temperature-dependent magnetic susceptibility test

[0061] The temperature-dependent magnetic susceptibility of sample 1 was tested on an MPMS-XL magnetic analyzer under the following conditions: field strength of 1000 Oe and temperature of 2-300 K.

[0062] Since the magnetism of rare earth cation compounds mainly originates from Eu 3+ The first-order orbital angular momentum of Eu. 3+ 4f of ions n The electronic configuration splits due to the repulsion between electrons and the spin-orbit coupling. 2S+1 L J Spectral terms, under the influence of a crystal field, further split into Stark levels. At room temperature, the number of Stark levels is relatively large, and as the temperature decreases, the effective magnetic moment changes with the decrease in the number of Stark levels. Due to the temperature dependence of the Stark levels, their magnetic susceptibility deviates from the Curie-Weiss law. This phenomenon is an inherent property of lanthanides and is related to the symmetry of the crystal field and the position of the lanthanide ions.

[0063] Molar magnetic susceptibility (χ) and the reciprocal of molar magnetic susceptibility (χ) -1 The relationship between ) and temperature T is as follows Figure 9 As shown, this compound obeys the Curie-Weiss law in the range of 150-300 K. At 300 K, the effective magnetic moment (μ) of this compound was calculated. e ff The value is 3.47μ BThis is very close to the standard value of 3.40-3.51 μ derived from the Van Vleck formula. B .

[0064] Figure 10 The effective magnetic moment (μ) of this compound e ff ) as a function of temperature. (From...) Figure 10 It can be seen that the effective magnetic moment (μ) of this compound e ff The value continued to decrease, reaching 0.45 μ at 2K. B This indicates the existence of antiferromagnetic exchange interactions between the magnetic center ions in the compound. The molar magnetic susceptibility χ of this compound increases slowly with decreasing temperature, then plateaus in the low-temperature region. However, with further decreases in temperature, the molar magnetic susceptibility χ begins to increase slowly again. This is due to the presence of a few rare-earth ions with a paramagnetic ground state in the compound. At the lowest temperature, the value of χT is close to 0 (T = 2K, χT = 0.018), which is consistent with Eu... 3+ The ion in the ground state at J=0 ( 7 F0). Due to [BO3] 3- and [ZnO6] 10- The anions are all diamagnetic; the paramagnetic contribution of this compound comes solely from Eu. 3+ Ions. The shortest Eu·.·Eu distance of this compound is Therefore, the magnetic exchange interaction in this compound is very weak.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A nonlinear optical crystal with fluorescent magnetism, characterized in that, The nonlinear optical crystal with fluorescent magnetism has the chemical formula Zn4EuO(BO3)3, belongs to the monoclinic crystal system, has a space group of Cm, and has a unit cell parameter of [missing information]. α=90°, β=100.193°, γ=90°.

2. A method for preparing a nonlinear optical crystal with fluorescent magnetism as described in claim 1, characterized in that, Includes the following steps: Zinc source, boron source and europium source are prepared in a molar ratio of (6-8):(10-14):1, mixed and ground. The ground mixture is placed in a crucible and heated once, kept at the temperature for 24 hours and then heated a second time. After the mixture melts and becomes transparent, it is cooled down. The mixture spontaneously crystallizes during the cooling process. After crystallization is completed, it is naturally cooled to room temperature to obtain the final product.

3. The method for preparing a nonlinear optical crystal with fluorescent magnetism according to claim 2, characterized in that, The zinc source is selected from any one of zinc oxide and zinc carbonate; the boron source is selected from boric acid and boron oxide; and the europium source is Eu2O3.

4. The method for preparing a nonlinear optical crystal with fluorescent magnetism according to claim 2, characterized in that, The specific process of the first heating is as follows: the temperature is increased to 450-500℃ at a rate of 60-65℃ / h.

5. The method for preparing a nonlinear optical crystal with fluorescent magnetism according to claim 2, characterized in that, The specific process of the secondary heating is as follows: the temperature is increased to 1170-1200℃ at a rate of 50-70℃ / h.

6. The method for preparing a nonlinear optical crystal with fluorescent magnetism according to claim 2, characterized in that, The specific cooling process is as follows: the temperature is reduced to 1000℃ at a rate of 3-5℃ / h.

7. The application of the fluorescent magnetic nonlinear optical crystal as described in claim 1 or the fluorescent magnetic nonlinear optical crystal prepared by the preparation method described in any one of claims 2-6 in the preparation of nonlinear optical devices.

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