Doped single crystal material green synthesis method based on rapid Joule thermal method and application

Abstract

The invention discloses a green synthesis method and application of a doped single crystal material based on a rapid Joule thermal method, and the green synthesis method comprises the following steps: S1, pretreating an initial single crystal to obtain a pretreated initial single crystal, the initial single crystal being selected from a lithium niobate single crystal or a lithium tantalate single crystal; s2, performing all-directional coating on the initial single crystal pretreated in the step S1 by using a metal foil to obtain the initial single crystal coated with the metal foil; and S3, placing the initial single crystal coated with the metal foil obtained in the step S2 on a clamp connected with a pulse power supply system, placing the clamp in a vacuum environment or an oxygen environment, applying current and voltage to the clamp through the pulse power supply system to enable the metal foil to generate Joule heat, keeping the temperature for a certain time, and cooling to prepare the metal-doped single crystal material. According to the technical scheme, the limitation of a traditional synthesis method in the aspects of energy consumption and doping uniformity is broken through, and high-efficiency and low-energy-consumption synthesis of the single crystal material with a controllable doping effect is realized.

Description

Technical Field

[0001] This invention belongs to the field of functional crystal material preparation technology, and in particular relates to a green synthesis method and application of doped single crystal materials based on rapid Joule heating. Background Technology

[0002] Lithium niobate and lithium tantalate single crystals are important optoelectronic functional materials, widely used in integrated optics, surface acoustic wave devices, and nonlinear optics. Their optoelectronic properties, ferroelectric properties, and damage threshold can be effectively tuned through metal element doping, thereby expanding their application range. Traditional doping methods (such as high-temperature solid-state reactions, ion implantation, and thermal diffusion) typically suffer from problems such as complex processes, high energy consumption, long production cycles, and limitations on the single dopant element or doping concentration and depth. Therefore, developing a rapid, efficient, and green synthesis method capable of multi-element doping has significant scientific and industrial value.

[0003] In existing technologies, the doping of single-crystal materials usually relies on methods such as high-temperature sintering or solid-state reaction, which have problems such as long synthesis cycle, high energy consumption, and poor doping uniformity. Summary of the Invention

[0004] In view of this, the present invention aims to propose a green synthesis method and application of doped single-crystal materials based on rapid Joule heating, in order to solve at least one technical problem in the background art. Compared with the traditional high-temperature sintering method and sol-gel method, the present invention achieves material synthesis in a short time through rapid Joule heating technology, avoiding the problems of high energy consumption and uneven doping in traditional methods.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A green synthesis method for doped single-crystal materials based on rapid Joule heating includes the following steps: S1: Pre-treat the initial single crystal to obtain a pre-treated initial single crystal, wherein the initial single crystal is selected from lithium niobate single crystal or lithium tantalate single crystal; S2: Use metal foil to fully coat the initial single crystal after pretreatment in step S1 to obtain the initial single crystal coated with metal foil. S3: Place the initial single crystal coated with metal foil obtained in step S2 on a fixture connected to a pulse power supply system and place it in a vacuum or oxygen environment. Apply current and voltage to the fixture through the pulse power supply system to generate Joule heating in the metal foil. After holding it at this temperature for a certain period of time, cool it to prepare a single crystal material doped with metal.

[0006] Furthermore, the pretreatment of the initial single crystal in step S1 includes the following steps: A1: trimming the initial single crystal according to the fixture dimensions in step S3; A2: The initial single crystal after cutting in step S1 is cleaned with acetone, ethanol and deionized water in sequence, and then subjected to ultrasonic treatment to obtain the cleaned initial single crystal. A3: Dry the initial single crystal after cleaning in step S2 to obtain the pretreated initial single crystal.

[0007] Furthermore, the initial single crystal cutting size described in step A1 matches the size of the fixture in step S3; In step A2, the total time for cleaning with acetone, ethanol, and deionized water in sequence is 10-20 minutes. In step A3, the drying temperature is 75-85℃ and the drying time is 1.8-2.2 hours.

[0008] Furthermore, the metal foil in step S2 is selected from one of copper foil, iron foil, and nickel foil.

[0009] Furthermore, in step S2, the thickness of the metal foil is 5 μm–200 μm.

[0010] Furthermore, in step S2, the thickness of the metal foil is 10–50 μm. Furthermore, the fixture in step S2 includes two symmetrically arranged clamping components, and the initial single crystal covered with metal foil is placed between the two clamping components through graphite paper; the two ends of the two clamping components are respectively connected to the positive and negative terminals of the pulse power supply system. The mounting components include a lower base and an upper base, with the upper base fixed to the lower base by locking bolts; The initial single crystal covered with metal foil is placed between the lower and upper bases using graphite paper on both the top and bottom sides. The thickness of graphite paper is 0.02-0.04 cm.

[0011] Furthermore, in step S3, the pulse power system supplies a current of 16-18A to the metal foil through the fixture and applies a voltage of 20-30V. The heat preservation time in step S3 is 1-2 minutes.

[0012] The doped material was prepared using the above-mentioned green synthesis method for doped single-crystal materials based on the rapid Joule heating process.

[0013] The aforementioned doped single-crystal materials are used in optoelectronic devices.

[0014] Compared with existing technologies, the green synthesis method and application of doped single-crystal materials based on the rapid Joule heating method described in this invention have the following advantages: This invention overcomes the limitations of traditional synthesis methods in terms of energy consumption and doping uniformity, achieving efficient, low-energy-consumption, and controllable doping effects in the synthesis of single-crystal materials. It combines rapid Joule heating technology with single-crystal doping processes, completing the synthesis in a short time. By combining Joule heating technology with the synthesis process of single-crystal materials, it achieves for the first time efficient and uniform doping of multiple elements in a short time. Compared to traditional methods, this invention can complete material synthesis at lower temperatures and in a shorter time, avoiding the long-term problems of high energy consumption and uneven doping. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The XPS spectrum of Cu-doped LiNbO3 in Example 1 of this invention is shown (A is Li 1s, B is Cu 2p, C is Nb 3d, and D is O 1s). Figure 2 The OH groups of Cu-doped LiNbO3 (Cu-LN) and LiNbO3 (LN) in Example 1 of this invention - difference spectrum; Figure 3 The images show the Raman spectra of monovalent copper-doped lithium niobate single crystals after Joule heat treatment of LiNbO3 (LN) in Examples 1, 7, and 8 of this invention. Figure 4 The XRD patterns are of LiNbO3 (LN) and Cu-doped LiNbO3 (Cu-LN) as described in Embodiment 1 of the present invention; Figure 5 The images show the cross-sectional view and EDS diagram of Cu-doped LiNbO3 as described in Example 1 of this invention (A is the cross-sectional view, B is the EDS diagram, and C is the elemental content table). Figure 6 The images shown are cross-sectional views and EDS diagrams of Fe-doped LiNbO3 as described in Example 1 of this invention (A is a cross-sectional view, B is an EDS diagram, and C is an elemental composition table). Figure 7 The images shown are cross-sectional views and EDS diagrams of Ti-doped LiNbO3 as described in Example 1 of this invention (A is a cross-sectional view, B is an EDS diagram, and C is an elemental composition table). Figure 8 This is a schematic diagram of the clamping component of the fixture described in Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the clamp described in Embodiment 1 of the present invention; Figure 10The images show Cu-doped LiNbO3 prepared in Examples 1 and 4 of this invention (Example 4 is on the left, and Example 1 is on the right). Figure 11 The images show Cu-doped LiNbO3 prepared in Examples 1 and 4 of this invention (Left side is Example 1, right side is Example 5). Figure 12 UV-Vis images of Cu-doped LiNbO3 prepared in Comparative Examples 1 and 6 of this invention.

[0016] Figure 13 The image shows Cu-doped LiNbO3 prepared in Comparative Example 12 of this invention.

[0017] Explanation of reference numerals in the attached figures: 1. Lower base; 2. Upper base; 3. Locking bolts; 4. Graphite paper; 5. Pulse power supply system. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] Example 1; For sample pretreatment, a lithium niobate / lithium tantalate single crystal substrate with dimensions of 20mm×10mm×0.5mm was selected and ultrasonically cleaned sequentially with acetone, 95% ethanol, and deionized water for 15 minutes to remove surface oil and impurities. It was then dried in a vacuum drying oven (80℃) for 2 hours. A 10μm thick Cu foil was used to cover the lithium niobate single crystal substrate, which was then placed on a fixture (with self-made 7*2*0.03cm graphite paper placed on both sides of the fixture). Under vacuum / oxygen conditions, the voltage was set to 25V, the current to 17A, and the holding time to 1-2 minutes to prepare copper-doped lithium niobate single crystals. After the experiment, the samples were allowed to cool naturally to room temperature, removed, cleaned and dried again, and the surface morphology was observed using an optical microscope. Samples with surface cracks or damage were discarded for subsequent characterization and testing.

[0021] like Figure 1 As shown, Cu-doped LiNbO3 single crystals were characterized by XPS in this application. Figure 1 As shown in (a), the binding energy of Li1s is located at 55.6 eV, corresponding to a typical Li... + The state indicates that the doping process did not change the chemical valence state of lithium. Figure 1 (b) is the high-resolution XPS spectrum of Cu 2p, where Cu 2p 3 / 2 and Cu 2p 1 / 2The peaks are located at 932.6 eV and 952.8 eV, respectively, indicating that copper mainly exists in the lattice in the +1 valence state. Figure 1 (c) shows the high-resolution XPS spectrum of Nb 3d. In the spectrum, the Nb 3d region is located at 208.3 eV (3d). 5 / 2 ) and 211.48 eV (3d 3 / 2 The peak of ) belongs to Nb 4+ This indicates the presence of partially reduced niobium ions in the crystal; while those located at 207.1 eV (3d) 5 / 2 )) and 209.68 eV (3d 3 / 2 The peak of ) corresponds to Nb 5+ , representing the main valence state in lithium niobate crystals. Figure 1 (d) shows the XPS spectrum of O1s. The three peaks are located at 529.8 eV, 530.7 eV, and 532.2 eV. The peak at 529.58 eV corresponds to defect oxygen, lattice oxygen, and adsorbed oxygen in lithium niobate, respectively. Based on the above results, it can be confirmed that Cu... + Successful entry into the LiNbO3 lattice, accompanied by valence state modulation of some Nb elements, further proves the successful preparation of monovalent copper-doped lithium niobate single crystals.

[0022] Cu + In XPS analysis of doped lithium niobate single crystals, Cu only showed a +1 value; Step 1: The Cu metal surface is ionized into Cu + ; Under the influence of vacuum, voltage, current, and Joule heating, the surface of Cu metal undergoes thermal activation and electric field-induced ionization, transforming into Cu. + As shown in equation (1): (1); An electric field enhances the surface ion migration tendency of Cu, and Joule heating increases the probability of energy barrier transitions. Step 2: Cu + Migrate and replace Li + Cu + Driven by an electric field and temperature, it migrates to the Li site and undergoes an equivalent substitution reaction: (2) The substitution reaction has a high energy barrier, but ΔG‡ decreases significantly under the combined effect of Joule heating and electric field, as shown in equation (2). Local lattice relaxation occurs in Cu. + Successfully occupied Li + Site.

[0023] like Figure 2 As shown, the OH groups of Cu:LiNbO3 are exhibited. - Difference spectrum. With Mg 2+ In 3+The mid-wavenumber difference spectral enhancement phenomenon exhibited by samples doped with multiple ions differs from that of Cu. + OH formed by doping - The difference spectra exhibit significant differences in wavenumber distribution, peak shape, and vibrational origin, reflecting the unique mechanism by which monovalent ions introduce defects into the crystal. The difference spectra are shown at 3480 cm⁻¹. -1 Significant absorption enhancement is observed in the low wavenumber region below, while absorption is enhanced above 3480 cm⁻¹. -1 The absorption signal weakens in the high wavenumber region, exhibiting a "low wavenumber increase, high wavenumber decrease" spectral characteristic. This characteristic differs from that of Mg. 2+ or In 3+ Plasma-doped samples at ~3483-3485 cm⁻¹ -1 The mid-wavenumber peak enhancement behavior of Cu indicates + Doping methods in the crystal lattice and their induced OH - The defect complex structures differ. (Cu) + The infrared difference spectrum shape of doped LiNbO3 single crystals and Na + The doped samples exhibited a high degree of similarity, suggesting that the site-occupancy behavior of these two monovalent ions in the crystal and the defect structures they induce may share commonalities. + With Li + With similar charge states and ionic radii, it preferentially and equivalently substitutes for Li sites, and does not introduce additional charge imbalances during doping, thus eliminating the need to rely on V_Li. - Or Nb_Li 4+ Charge compensation is performed on defects such as Nb_Li. This mechanism suppresses typical Nb_Li 4+ -3V_Li - -OH - The formation of the complex promotes H + Preferred combination in normal Li + OH- is formed at the site. - This enhances the 3466cm -1 Low wavenumber intrinsic absorption peaks.

[0024] like Figure 3As shown in the figure, the Raman spectra of monovalent copper-doped lithium niobate single crystals treated with Joule heat at different temperatures are presented. Untreated LiNbO3 single crystals (LN) exhibit clear and sharp characteristic peaks, indicating a high degree of lattice order. With increasing temperature, the Raman peak intensity and full width at half maximum (FWHM) of the samples show significant changes. The sample treated at 700℃ exhibits the highest peak intensity, and the FWHM of some characteristic peaks narrows, indicating that copper ions effectively enter the lithium niobate lattice at this temperature, promoting local structural ordering and enhancing lattice vibration modes. Further heating to 800℃ results in a significant decrease in peak intensity and broadening of spectral lines, indicating that excessively high temperatures introduce more defects and disordered structures, leading to enhanced lattice distortion. Overall, 700℃ is the optimal temperature for achieving a balance between copper doping and lattice stability, which is beneficial for obtaining strong phonon responses and good crystal quality.

[0025] like Figure 5 The image shown is a cross-sectional view and EDS diagram of Cu-doped lithium niobate according to Embodiment 1 of the present invention.

[0026] Example 2; For sample pretreatment, a lithium niobate / lithium tantalate single crystal substrate with dimensions of 20mm×10mm×0.5mm was selected and ultrasonically cleaned sequentially with acetone, 95% ethanol, and deionized water for 15 minutes to remove surface oil and impurities. It was then dried in a vacuum drying oven (80℃) for 2 hours. Iron foil (10μm thick) was used to cover the lithium niobate single crystal substrate, which was then placed on a fixture (with self-made 7*2*0.03cm graphite paper placed on both sides of the fixture). Under vacuum / oxygen conditions, the voltage was set to 25V, the current to 17A, and the holding time to 1-2 minutes to prepare iron-doped lithium niobate single crystals. After the experiment, the samples were allowed to cool naturally to room temperature, removed, cleaned and dried again, and the surface morphology was observed using an optical microscope. Samples with surface cracks or damage were discarded for subsequent characterization and testing.

[0027] like Figure 6 The image shown is a cross-sectional view and EDS diagram of the iron-doped lithium niobate described in Embodiment 2 of the present invention.

[0028] Example 3; For sample pretreatment, a lithium niobate / lithium tantalate single crystal substrate with dimensions of 20mm × 10mm × 0.5mm was selected and ultrasonically cleaned sequentially with acetone, 95% ethanol, and deionized water for 15 minutes to remove surface oil and impurities. It was then dried in a vacuum drying oven (80℃) for 2 hours. A nickel foil (10μm thick) was used to cover the lithium niobate single crystal substrate, which was then placed on a fixture (with self-made 7*2*0.03cm graphite paper placed on both sides). Under vacuum / oxygen conditions, the voltage was set to 25V, the current to 17A, and the holding time to 1-2 minutes to prepare nickel-doped lithium niobate single crystals. After the experiment, the samples were allowed to cool naturally to room temperature, removed, cleaned and dried again, and the surface morphology was observed using an optical microscope. Samples with surface cracks or damage were discarded for subsequent characterization and testing. Figure 7 The image shown is a cross-sectional view and EDS diagram of nickel-doped lithium niobate according to Embodiment 3 of the present invention.

[0029] Example 4; The difference from Example 1 is that the thickness of the Cu foil is 5 μm.

[0030] like Figure 10 As shown, the sample in Example 4 was not uniformly doped.

[0031] Example 5; The difference from Example 1 is that the thickness of the Cu foil is 50 μm.

[0032] like Figure 11 As shown, the sample in Example 5 was not uniformly doped.

[0033] Example 6; The difference from Example 1 is that the current is 14A.

[0034] Example 7; The difference from Example 1 is that the current is 16A.

[0035] Example 8; The difference from Example 1 is that the current is 18A.

[0036] like Figure 3As shown in the figure, the Raman spectra of monovalent copper-doped lithium niobate single crystals treated with Joule heat at different temperatures are presented. Untreated LiNbO3 single crystals (LN) exhibit clear and sharp characteristic peaks, indicating a high degree of lattice order. With increasing temperature, the Raman peak intensity and full width at half maximum (FWHM) of the samples show significant changes. The sample treated at 700℃ exhibits the highest peak intensity, and the FWHM of some characteristic peaks narrows, indicating that copper ions effectively enter the lithium niobate lattice at this temperature, promoting local structural ordering and enhancing lattice vibration modes. Further heating to 800℃ results in a significant decrease in peak intensity and broadening of spectral lines, indicating that excessively high temperatures introduce more defects and disordered structures, leading to enhanced lattice distortion. Overall, 700℃ is the optimal temperature for achieving a balance between copper doping and lattice stability, which is beneficial for obtaining strong phonon responses and good crystal quality.

[0037] Comparative Example 1; The difference from Example 1 is that the current is 14A.

[0038] like Figure 12 As shown, the low current results in a low temperature during the preparation process. The copper doping content of the copper-doped lithium niobate single crystal prepared at 14A is low, resulting in the absence of a copper ultraviolet absorption peak.

[0039] Comparative Example 2; The difference from Example 1 is that the current is 20A.

[0040] like Figure 13 As shown, the copper-doped lithium niobate single crystals obtained by the 20A Joule heating process do not achieve the desired crystal uniformity due to the uneven temperature distribution caused by Joule heating.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A green synthesis method of doped single crystal material based on fast Joule heating method, characterized in that: The method comprises the following steps: S1: pretreating an initial single crystal to obtain a pretreated initial single crystal, wherein the initial single crystal is selected from a lithium niobate single crystal or a lithium tantalate single crystal; S2: using a metal foil to fully coat the pretreated initial single crystal in step S1 to obtain a metal foil-coated initial single crystal; S3: placing the metal foil-coated initial single crystal obtained in step S2 on a clamp connected to a pulse power system, and placing it in a vacuum environment or an oxygen environment, applying current and voltage to the clamp through the pulse power system to generate Joule heat in the metal foil, and cooling after a certain holding time to prepare a metal-doped single crystal material.

2. A green synthesis method of doped single crystal material based on fast Joule heating method according to claim 1, characterized in that: The pretreatment of the initial single crystal in step S1 comprises the following steps: A1: cutting the initial single crystal according to the size of the clamp in step S3; A2: sequentially cleaning the cut initial single crystal in step S1 with acetone, ethanol, and deionized water, and treating it with ultrasonic waves to obtain a cleaned initial single crystal; A3: drying the cleaned initial single crystal in step S2 to obtain a pretreated initial single crystal.

3. A green synthesis method of doped single crystal material based on fast Joule heating method according to claim 2, characterized in that: In step A1, the cutting size of the initial single crystal matches the size of the clamp in step S3; In step A2, the total time for sequentially cleaning with acetone, cleaning with ethanol, and ultrasonic cleaning with deionized water is 10-20 minutes; In step A3, the drying temperature is 75-85℃, and the drying time is 1.8-2.2 hours.

4. The green synthesis of doped single crystal material based on fast Joule heating method according to claim 1, characterized in that: The metal foil in step S2 is selected from one of a copper foil, an iron foil, and a nickel foil.

5. The green synthesis of doped single crystal material based on fast Joule heating method according to claim 1, characterized in that: The thickness of the metal foil in step S2 is 5μm–200μm.

6. The green synthesis of doped single crystal materials based on the fast Joule heating method according to claim 1, characterized in that: The thickness of the metal foil in step S2 is 10–50μm.

7. The green synthesis of doped single crystal material based on fast Joule heating method according to claim 1, characterized in that: The clamp in step S2 comprises two symmetrical holding assemblies, and the metal foil-coated initial single crystal is arranged between the two holding assemblies through graphite paper; the two ends of the two holding assemblies are respectively connected to the positive and negative poles of the pulse power system; The holding assembly comprises a lower base and an upper base, and the upper base is fixed to the lower base by locking bolts; The metal foil-coated initial single crystal is arranged between the lower base and the upper base through graphite paper on the upper and lower sides; The thickness of the graphite paper is 0.02-0.04cm.

8. The green synthesis of doped single crystal material based on fast Joule heating method according to claim 1, characterized in that: In step S3, the pulse power system applies a current of 16-18A to the metal foil through the clamp, and applies a voltage of 20-30V; In step S3, the holding time is 1-2min.

9. A metal-doped single crystal material prepared by the method of claim 1-8.

10. The metal-doped single crystal material of claim 9 is applied to optoelectronic devices.

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