A method for preparing lithium niobate microcrystal powder
The preparation of lithium niobate microcrystalline powder by solid-state assisted molten salt method solves the problems of low crystallinity and poor chemical stability of lithium niobate powder, and realizes the efficient preparation of high-performance lithium niobate ceramic materials, which are suitable for optoelectronic fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TAIYUAN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2026-01-15
- Publication Date
- 2026-05-12
AI Technical Summary
Existing lithium niobate powder has low crystallinity and poor chemical stability, making it difficult to prepare high-performance lithium niobate ceramic materials.
Lithium niobate microcrystalline powder was prepared by solid-state assisted molten salt method. Lithium ions were stabilized by doping with potassium and sodium ions, and the growth of lithium niobate nuclei was controlled by the Oswald ripening mechanism to form highly crystalline lithium niobate microcrystalline powder.
Highly crystalline lithium niobate microcrystalline powder with good chemical stability was obtained, which is suitable for large-scale mass production, has low mechanical pollution, and stable product composition, thus promoting the development of lithium niobate ceramics in the optoelectronic field.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional ceramic material powder preparation technology, specifically relating to a method for preparing lithium niobate microcrystalline powder. Background Technology
[0002] Lithium niobate (LiNbO3) crystals have attracted significant attention due to their combination of ferroelectric, piezoelectric, electro-optic, acousto-optic, strong photorefractive, and photovoltaic effects, earning them the reputation of "silicon in photonics." They are among the most widely used materials in modern optics and electronics. However, the preparation of single crystals is costly, has a long production cycle, and is limited in size and shape, especially in controlling compositional uniformity during doping modification. Therefore, there is an urgent need for a method to prepare lithium niobate ceramic materials that is highly designable, easily achieves complex shapes and doping, and is cost-effective. Based on the manufacturing process of functional ceramics, the synthesis of lithium niobate powder with high crystallinity, uniform particle size, and good dispersion is a core technology in ceramic preparation.
[0003] Currently, the main methods for preparing lithium niobate powder are wet chemical method, solid-state sintering method, and molten salt method. While the wet chemical method can control the crystal growth rate and morphology, it suffers from complex operation and waste liquid treatment issues. The solid-state sintering method, although simple to operate and suitable for large-scale production, faces practical problems such as lithium volatilization at high temperatures, uneven chemical composition and low crystallinity of the product, and the presence of numerous impurity phases (such as Li3NbO4 and LiNb3O8). The molten salt method is considered an effective method for preparing highly crystalline powders. Studies have shown that niobate microcrystals prepared using the molten salt method exhibit significantly improved sintering activity (L. Liu, ...). et al . Oriented and ultrafine-grain potassium sodium niobate piezoelectricceramics prepared by heterogeneous microcrystalline transformation. Ceram. Int. 49 (2023) 30897; L. Liu, et al Dense KSr2Nb5O 15 ceramics with uniform grain size prepared by molten salt synthesis, J. Alloys Compd.616 (2014)293), further promoting the densification process of related ceramics. However, the lithium source materials (Li2CO3 or LiNbO3) inevitably undergo heterogeneous phase reactions and phase separation in molten salts, making it difficult to synthesize lithium niobate microcrystals. Therefore, there are no reports on the preparation of lithium niobate microcrystals. It is evident that developing a preparation technology for lithium niobate microcrystal powder with high crystallinity and good chemical stability is key to the development of lithium niobate ceramic materials. Summary of the Invention
[0004] To address the problems of low crystallinity and poor chemical stability in existing lithium niobate powders and to provide ideal raw materials for the preparation of high-performance lithium niobate ceramics, this invention provides a method for preparing lithium niobate microcrystalline powder with high crystallinity and chemical stability.
[0005] This invention proposes a method for preparing lithium niobate microcrystalline powder, which employs a solid-state assisted molten salt method. First, lithium niobate powder doped with potassium and sodium ions is prepared using a solid-state method. Due to the effect of potassium and sodium ions, the lithium ions in the raw material are stabilized within the ilmenite (distorted perovskite) phase particles, preventing them from transforming into other impurity phases. Then, the obtained lithium niobate powder is placed in a mixed molten salt of sodium chloride and potassium chloride. Lithium niobate precipitates from the ilmenite phase particles, forming lithium niobate nuclei. Under the control of the Ostwald ripening mechanism (driven by a concentration gradient), these nuclei continuously absorb lithium niobate from the ilmenite phase, gradually growing into lithium niobate microcrystals. The precipitation of lithium niobate causes the ilmenite phase particles to break down into perovskite-structured potassium sodium niobate nanoparticles, which are then removed during desalination and washing, suspended in water, yielding the final product—lithium niobate microcrystalline powder.
[0006] This invention provides a method for preparing lithium niobate microcrystalline powder, wherein the lithium niobate is composed of LiNbO3; the method includes the following steps:
[0007] Step 1: Preparation of lithium niobate powder doped with potassium and sodium ions (K 0.5 Na 0.5 ) 1-x Li x NbO3 x=0.5~0.9, the specific process is as follows: Analytical grade potassium carbonate, sodium carbonate, lithium carbonate, and niobium pentoxide powder are weighed and mixed according to a stoichiometric ratio of (0.5-0.5x):(0.5-0.5x):x:1, and then placed in a polytetrafluoroethylene ball mill jar. Anhydrous ethanol is added, and the mixture is ball-milled for 8h~24h; the weight ratio of the anhydrous ethanol to the raw material mixture is 1~2:1. The ball-milled wet material is placed in an oven and dried at 60℃~90℃ for 5h~10h. The dried powder is then ground. The ground powder is placed in a corundum crucible and heated to 850℃~1050℃ at a heating rate of 5℃ / min, and held at that temperature for 1h~6h. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder doped with potassium and sodium ions.
[0008] Step 2: The raw material mixture for preparing lithium niobate microcrystals is prepared as follows: Weigh analytical grade potassium chloride, sodium chloride, and the lithium niobate powder doped with potassium and sodium ions obtained in Step 1; place the potassium chloride powder, sodium chloride powder, and lithium niobate powder doped with potassium and sodium ions into a polyethylene ball mill jar, add anhydrous ethanol, and ball mill for 8-24 hours; place the ball-milled wet material in an oven and dry it at 60-90℃ for 5-10 hours to obtain a dry powder; grind the dry powder into powder using an agate mortar and pestle to obtain the raw material mixture for preparing lithium niobate microcrystals;
[0009] The molar ratio of potassium chloride to sodium chloride is 1:1; the mass ratio of the sum of the masses of potassium chloride and sodium chloride to the mass of lithium niobate powder doped with potassium and sodium ions is 1 to 5:1. The mass ratio of the amount of anhydrous ethanol added to the mass ratio of the raw material mixture placed in the polyethylene ball mill jar is 1 to 2:1.
[0010] Step 3: Preparation of lithium niobate microcrystalline powder:
[0011] The specific process is as follows: The raw material mixture of lithium niobate microcrystals obtained in step two is placed in an alumina crucible and calcined at 750℃~1000℃ for 0.5h~4h; after calcination, it is repeatedly washed and filtered in distilled water at 100℃ until Cl is not detectable in the filtrate. - The powder was dried and washed at 80°C to obtain lithium niobate (LiNbO3) microcrystalline powder.
[0012] The beneficial effects of this invention are:
[0013] (1) The lithium niobate microcrystalline particles prepared in this invention maintain a regular morphology, indicating that the crystallinity is high, the microcrystalline powder particles are uniform and well dispersed; combined with the XRD analysis results, it is found that the particles have high crystallinity and are pure lithium niobate phase;
[0014] (2) The steps of the present invention are simple, the product obtained meets the requirements of lithium niobate ceramic raw materials, the mechanical pollution is small, the formula deviation is small, the process is easy to control, and the chemical composition of the product has small deviation and good stability, which can be mass-produced on a large scale. The present invention can accelerate the development of lithium niobate ceramics in the optoelectronic field. Attached Figure Description
[0015] Figure 1 The lithium niobate ((K) doped with potassium and sodium ions prepared in Examples 1 and 4) 0.5 Na 0.5 ) 1-x Li x NbO3 x =0.5 、x =0.8) XRD patterns of powder and powder prepared in the comparative experiment.
[0016] Figure 2 It is the lithium niobate ((K) doped with potassium and sodium ions prepared in Example 4) 0.5 Na 0.5 ) 1-x Li x NbO3 x =0.8) SEM image of the powder.
[0017] Figure 3 These are the XRD patterns of lithium niobate (LiNbO3) microcrystalline powders from Examples 2, 4, and 5 at different calcination temperatures.
[0018] Figure 4 This is a SEM image of the lithium niobate (LiNbO3) microcrystalline powder prepared in Example 4.
[0019] Figure 5 This is a SEM image of the lithium niobate (LiNbO3) microcrystalline particles prepared in Example 4.
[0020] Figure 6 This is a SEM image of the lithium niobate (LiNbO3) microcrystalline powder prepared in Example 5. Detailed Implementation
[0021] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments. Example 1
[0022] This embodiment describes a method for preparing lithium niobate microcrystalline powder, the specific process of which is as follows:
[0023] Step 1: Preparation of lithium niobate ((K) doped with potassium and sodium ions) 0.5 Na 0.5 ) 1-x Li x NbO3, x=0.5) powder. The specific process for preparing lithium niobate powder doped with potassium and sodium ions is as follows: Analytical grade potassium carbonate, sodium carbonate, lithium carbonate, and niobium pentoxide powders are weighed and mixed according to stoichiometric ratio, placed in a polytetrafluoroethylene ball mill jar, and anhydrous ethanol is added. The mixture is ball-milled for 8 hours. The weight ratio of anhydrous ethanol to the raw material mixture is 1:1. The ball-milled wet material is placed in an oven and dried at 60°C for 10 hours. The dried powder is then ground. The ground powder is placed in a corundum crucible and heated to 850°C at a heating rate of 5°C / min, and held at that temperature for 6 hours. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder doped with potassium and sodium ions.
[0024] To verify the importance of potassium and sodium doping, a comparative experiment was conducted, preparing lithium niobate powder without potassium and sodium doping, corresponding to (K... 0.5 Na 0.5 ) 1-x Li x NbO3, x =1. The specific process is as follows: Analytical grade lithium carbonate and niobium pentoxide powder are weighed and mixed according to the stoichiometric ratio, placed in a polytetrafluoroethylene ball mill jar, and anhydrous ethanol is added. The mixture is ball-milled for 8 hours. The weight ratio of anhydrous ethanol to the raw material mixture is 1:1. The ball-milled wet material is placed in an oven and dried at 60°C for 10 hours. The dried powder is then ground. The ground powder is placed in a corundum crucible and heated to 850°C at a heating rate of 5°C / min, and held at that temperature for 6 hours. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder without potassium and sodium ions. The XRD pattern of the lithium niobate powder without potassium and sodium ions is shown in the comparative experiment. Figure 1 As shown, a comparison with the standard spectral lines of lithium niobate reveals that the XRD patterns are completely inconsistent with those of the standard spectral lines, indicating that LiNbO3 phase cannot be synthesized without potassium and sodium ions under the aforementioned conditions. This demonstrates that lithium niobate microcrystalline powder cannot be prepared using conventional methods.
[0025] The XRD pattern of the lithium niobate powder doped with potassium and sodium ions in this embodiment is as follows: Figure 1 As shown, a comparison with the standard spectral lines of lithium niobate reveals that the main crystalline phase of lithium niobate with small amounts of potassium and sodium ions is the LiNbO3 phase. x The principal phase obtained when K = 0.5 can be represented as (K 0.5 Na 0.5 ) 0.5 Li 0.5 NbO3, and the product also contains some impurities; through x =0.5 and xCompared to the case where the value is 1, it can be seen that the doping of potassium and sodium ions plays a key role in the preparation of lithium niobate crystal structure phase.
[0026] Step 2: Preparation of the raw material mixture for lithium niobate microcrystals. The specific process for preparing the raw material mixture for lithium niobate microcrystals is as follows: Weigh analytically pure potassium chloride and sodium chloride, and the obtained lithium niobate powder doped with potassium and sodium ions. Place the potassium chloride and sodium chloride powder and the obtained lithium niobate powder doped with potassium and sodium ions sequentially into a polyethylene ball mill jar, add anhydrous ethanol, and ball mill for 12 hours. Place the ball-milled wet material in an oven and dry it at 60°C for 10 hours to obtain a dry powder. Grind the dry powder into a powder using an agate mortar to obtain the raw material mixture for preparing lithium niobate microcrystals. The molar ratio of potassium chloride to sodium chloride is 1:1. The mass ratio of the sum of the masses of potassium chloride and sodium chloride to the mass ratio of the lithium niobate powder doped with potassium and sodium ions is 1:1. The mass ratio of the amount of anhydrous ethanol added to the mass ratio of the raw material mixture placed in the polyethylene ball mill jar is 1:1.
[0027] Step 3: Preparation of lithium niobate microcrystalline powder. The specific process for preparing lithium niobate microcrystalline powder is as follows: The raw material mixture of the obtained lithium niobate microcrystals is placed in an alumina crucible and calcined at 750℃ for 4 hours. After calcination, it is repeatedly washed and filtered in distilled water at 100℃ until Cl is undetectable in the filtrate. - The powder was dried and washed at 80°C to obtain lithium niobate (LiNbO3) microcrystalline powder. Example 2
[0028] This embodiment describes a method for preparing lithium niobate microcrystalline powder, the specific process of which is as follows:
[0029] Step 1: Preparation of lithium niobate ((K) doped with potassium and sodium ions) 0.5 Na 0.5 ) 1-x Li x NbO3, x =0.6) powder. The specific process for preparing lithium niobate powder doped with potassium and sodium ions is as follows: analytically pure potassium carbonate, sodium carbonate, lithium carbonate, and niobium pentoxide powders are weighed and mixed according to the stoichiometric ratio, placed in a polytetrafluoroethylene ball mill jar, and anhydrous ethanol is added. The mixture is ball-milled for 12 hours. The weight ratio of anhydrous ethanol to the raw material mixture is 1:1. The ball-milled wet material is placed in an oven and dried at 70°C for 8 hours. The dried powder is then ground. The ground powder is placed in a corundum crucible and heated to 900°C at a heating rate of 5°C / min, and held at that temperature for 4 hours. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder doped with potassium and sodium ions.
[0030] Step 2: Preparation of the raw material mixture for lithium niobate microcrystals. The specific process for preparing the raw material mixture for lithium niobate microcrystals is as follows: Weigh analytically pure potassium chloride and sodium chloride, and the obtained lithium niobate powder doped with potassium and sodium ions. Place the potassium chloride and sodium chloride powder and the obtained lithium niobate powder doped with potassium and sodium ions sequentially into a polyethylene ball mill jar, add anhydrous ethanol, and ball mill for 12 hours. Place the ball-milled wet material in an oven and dry it at 70°C for 8 hours to obtain a dry powder. Grind the dry powder into a powder using an agate mortar to obtain the raw material mixture for preparing lithium niobate microcrystals. The molar ratio of potassium chloride to sodium chloride is 1:1. The mass ratio of the sum of the masses of potassium chloride and sodium chloride to the mass ratio of the lithium niobate powder doped with potassium and sodium ions is 2:1. The mass ratio of the amount of anhydrous ethanol added to the mass ratio of the raw material mixture placed in the polyethylene ball mill jar is 1.5:1.
[0031] Step 3: Preparation of lithium niobate microcrystalline powder. The specific process for preparing lithium niobate microcrystalline powder is as follows: The raw material mixture of the obtained lithium niobate microcrystals is placed in an alumina crucible and calcined at 800℃ for 3 hours. After calcination, it is repeatedly washed and filtered in distilled water at 100℃ until Cl is undetectable in the filtrate. - The powder was dried and washed at 80°C to obtain lithium niobate (LiNbO3) microcrystalline powder.
[0032] The XRD pattern of the lithium niobate microcrystalline powder obtained in this embodiment is as follows: Figure 3 As shown in the figure, when the calcination temperature is 800℃, the main crystalline phase of the lithium niobate powder doped with potassium and sodium ions, after being subjected to molten salt environment, completely matches the spectral lines of the lithium niobate standard card. Example 3
[0033] This embodiment describes a method for preparing lithium niobate microcrystalline powder, the specific process of which is as follows:
[0034] Step 1: Preparation of lithium niobate ((K) doped with potassium and sodium ions) 0.5 Na 0.5 ) 1-x Li x NbO3, x=0.7) powder. The specific process for preparing lithium niobate powder doped with potassium and sodium ions is as follows: Analytical grade potassium carbonate, sodium carbonate, lithium carbonate, and niobium pentoxide powders are weighed and mixed according to stoichiometric ratio, placed in a polytetrafluoroethylene ball mill jar, and anhydrous ethanol is added. The mixture is ball-milled for 16 hours. The weight ratio of anhydrous ethanol to the raw material mixture is 1:1. The ball-milled wet material is placed in an oven and dried at 80°C for 6 hours. The dried powder is then ground. The ground powder is placed in a corundum crucible and heated to 1000°C at a heating rate of 5°C / min, and held at that temperature for 2 hours. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder doped with potassium and sodium ions.
[0035] Step 2: Preparation of the raw material mixture for lithium niobate microcrystals. The specific process for preparing the raw material mixture for lithium niobate microcrystals is as follows: Weigh analytically pure potassium chloride and sodium chloride, and the obtained lithium niobate powder doped with potassium and sodium ions. Place the potassium chloride and sodium chloride powder and the obtained lithium niobate powder doped with potassium and sodium ions sequentially into a polyethylene ball mill jar, add anhydrous ethanol, and ball mill for 16 hours. Place the ball-milled wet material in an oven and dry it at 80°C for 6 hours to obtain a dry powder. Grind the dry powder into a powder using an agate mortar to obtain the raw material mixture for preparing lithium niobate microcrystals. The molar ratio of potassium chloride to sodium chloride is 1:1. The mass ratio of the sum of the masses of potassium chloride and sodium chloride to the mass ratio of the lithium niobate powder doped with potassium and sodium ions is 3:1. The mass ratio of the amount of anhydrous ethanol added to the mass ratio of the raw material mixture placed in the polyethylene ball mill jar is 1.5:1.
[0036] Step 3: Preparation of lithium niobate microcrystalline powder. The specific process for preparing lithium niobate microcrystalline powder is as follows: The raw material mixture of the obtained lithium niobate microcrystals is placed in an alumina crucible and calcined at 850℃ for 2 hours. After calcination, it is repeatedly washed and filtered in distilled water at 100℃ until Cl is not detectable in the filtrate. - The powder was dried and washed at 80°C to obtain lithium niobate (LiNbO3) microcrystalline powder. Example 4
[0037] This embodiment describes a method for preparing lithium niobate microcrystalline powder, the specific process of which is as follows:
[0038] Step 1: Preparation of lithium niobate ((K) doped with potassium and sodium ions) 0.5 Na 0.5 ) 1-x Li x NbO3, x=0.8) powder. The specific process for preparing lithium niobate powder doped with potassium and sodium ions is as follows: Analytical grade potassium carbonate, sodium carbonate, lithium carbonate, and niobium pentoxide powders are weighed and mixed according to stoichiometric ratio, placed in a polytetrafluoroethylene ball mill jar, and anhydrous ethanol is added. The mixture is ball-milled for 20 hours. The weight ratio of anhydrous ethanol to the raw material mixture is 1:1. The ball-milled wet material is placed in an oven and dried at 90°C for 5 hours. The dried powder is then ground. The ground powder is placed in a corundum crucible and heated to 900°C at a heating rate of 5°C / min, and held at that temperature for 2 hours. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder doped with potassium and sodium ions.
[0039] The XRD pattern of the lithium niobate powder doped with potassium and sodium ions in this embodiment is as follows: Figure 1 As shown, a comparison with the standard spectral lines of lithium niobate reveals that the main crystalline phase of lithium niobate doped with small amounts of potassium and sodium ions is the LiNbO3 phase. x The principal phase obtained when K = 0.8 can be represented as (K 0.5 Na 0.5 ) 0.2 Li 0.8 NbO3, no other second phase is produced; through x =0.8 and x Compared to the case where the concentration is 1, it can be seen that doping with small amounts of potassium and sodium ions plays a crucial role in the preparation of lithium niobate crystal structures. Lithium niobate doped with potassium and sodium ions (K... 0.5 Na 0.5 ) 0.2 Li 0.8 SEM images of NbO3 powder are as follows: Figure 2 As shown in the figure. It can be seen from the figure that (K) 0.5 Na 0.5 ) 0.2 Li 0.8 NbO3 exhibits the typical characteristics of powders synthesized by solid-phase methods, namely, amorphous particles with severe agglomeration and poor dispersibility.
[0040] Step 2: Preparation of the raw material mixture for lithium niobate microcrystals. The specific process for preparing the raw material mixture for lithium niobate microcrystals is as follows: Weigh analytically pure potassium chloride and sodium chloride, and the obtained lithium niobate powder doped with potassium and sodium ions. Place the potassium chloride and sodium chloride powder and the obtained lithium niobate powder doped with potassium and sodium ions sequentially into a polyethylene ball mill jar, add anhydrous ethanol, and ball mill for 20 hours. Place the ball-milled wet material in an oven and dry it at 90°C for 5 hours to obtain a dry powder. Grind the dry powder into a powder using an agate mortar to obtain the raw material mixture for preparing lithium niobate microcrystals. The molar ratio of potassium chloride to sodium chloride is 1:1. The mass ratio of the sum of the masses of potassium chloride and sodium chloride to the mass ratio of the lithium niobate powder doped with potassium and sodium ions is 1:1. The mass ratio of the amount of anhydrous ethanol added to the mass ratio of the raw material mixture placed in the polyethylene ball mill jar is 1:1.
[0041] Step 3: Preparation of lithium niobate microcrystalline powder. The specific process for preparing lithium niobate microcrystalline powder is as follows: The raw material mixture of the obtained lithium niobate microcrystals is placed in an alumina crucible and calcined at 900℃ for 2 hours. After calcination, it is repeatedly washed and filtered in distilled water at 100℃ until Cl is not detectable in the filtrate. - The powder was dried and washed at 80°C to obtain lithium niobate (LiNbO3) microcrystalline powder.
[0042] The XRD pattern of the lithium niobate microcrystalline powder obtained in this embodiment is as follows: Figure 3 As shown in the figure, when calcined at 900℃, the main crystalline phase of the lithium niobate powder doped with potassium and sodium ions, after being subjected to molten salt conditions, perfectly matches the spectral lines of the lithium niobate standard card. The SEM image of the lithium niobate (LiNbO3) microcrystalline powder obtained in this embodiment is shown below. Figure 4 As shown in the figure, the microcrystalline powder particles have good dispersion and uniform size distribution (diameter 0.5μm~3μm). Figure 5 The image shows SEM images of lithium niobate (LiNbO3) microcrystalline particles. As can be seen from the images, the particles exhibit the typical morphology of LiNbO3 crystals. This indicates that the lithium niobate powder doped with potassium and sodium ions, in a molten salt environment, nucleates and grows according to the growth habits of LiNbO3 crystals under the control of the Oswald ripening mechanism. Based on the above characterization data (combining particle morphology and XRD peaks), it can be concluded that this embodiment yielded lithium niobate microcrystalline powder with high crystallinity. Example 5
[0043] This embodiment describes a method for preparing lithium niobate microcrystalline powder, the specific process of which is as follows:
[0044] Step 1: Preparation of lithium niobate ((K) doped with potassium and sodium ions) 0.5 Na0.5 ) 1-x Li x NbO3, x =0.9) powder. The specific process for preparing lithium niobate powder doped with potassium and sodium ions is as follows: Analytical grade potassium carbonate, sodium carbonate, lithium carbonate, and niobium pentoxide powders are weighed and mixed according to stoichiometric ratio, placed in a polytetrafluoroethylene ball mill jar, and anhydrous ethanol is added. The mixture is ball-milled for 24 hours. The weight ratio of anhydrous ethanol to the raw material mixture is 2:1. The ball-milled wet material is placed in an oven and dried at 90°C for 8 hours. The dried powder is then ground. The ground powder is placed in a corundum crucible and heated to 1050°C at a heating rate of 5°C / min, and held at that temperature for 30 minutes. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder doped with potassium and sodium ions.
[0045] Step 2: Preparation of the raw material mixture for lithium niobate microcrystals. The specific process for preparing the raw material mixture for lithium niobate microcrystals is as follows: Weigh analytically pure potassium chloride and sodium chloride, and the obtained lithium niobate powder doped with potassium and sodium ions. Place the potassium chloride and sodium chloride powder and the obtained lithium niobate powder doped with potassium and sodium ions sequentially into a polyethylene ball mill jar, add anhydrous ethanol, and ball mill for 24 hours. Place the ball-milled wet material in an oven and dry it at 90°C for 8 hours to obtain a dry powder. Grind the dry powder into a powder using an agate mortar to obtain the raw material mixture for preparing lithium niobate microcrystals. The molar ratio of potassium chloride to sodium chloride is 1:1. The mass ratio of the sum of the masses of potassium chloride and sodium chloride to the mass ratio of the lithium niobate powder doped with potassium and sodium ions is 5:1. The mass ratio of the amount of anhydrous ethanol added to the mass ratio of the raw material mixture placed in the polyethylene ball mill jar is 2:1.
[0046] Step 3: Preparation of lithium niobate microcrystalline powder. The specific process for preparing lithium niobate microcrystalline powder is as follows: The raw material mixture of the obtained lithium niobate microcrystals is placed in an alumina crucible and calcined at 1000℃ for 30 min. After calcination, it is repeatedly washed and filtered in distilled water at 100℃ until Cl is undetectable in the filtrate. - The powder was dried and washed at 80°C to obtain lithium niobate (LiNbO3) microcrystalline powder.
[0047] The XRD pattern of the lithium niobate microcrystalline powder obtained in this embodiment is as follows: Figure 3 As shown in the figure, when the calcination temperature is 1000℃, the lithium niobate powder doped with potassium and sodium ions exhibits a small number of impurity peaks after being subjected to molten salt conditions. The main crystalline phase basically matches the spectral lines of the lithium niobate standard card. The SEM image of the lithium niobate (LiNbO3) microcrystalline powder obtained in this embodiment is shown in the figure. Figure 6As shown in the figure, the microcrystalline powder particles exhibit good dispersion and uniform size distribution (diameter 1μm~4μm). The particles possess the typical morphology of LiNbO3 crystals, indicating that the lithium niobate powder doped with potassium and sodium ions, in a molten salt environment, nucleates and grows according to the growth habits of LiNbO3 crystals under the control of the Oswald ripening mechanism. Based on the above characterization data, it can be concluded that this embodiment yielded lithium niobate microcrystalline powder with regular morphological characteristics.
Claims
1. A method for preparing lithium niobate microcrystalline powder, characterized in that... Includes the following steps: Step 1: Preparation of lithium niobate powder doped with potassium and sodium ions (K 0.5 Na 0.5 ) 1-x Li x NbO3 x =0.5~0.9, the specific process is as follows: analytical grade potassium carbonate, sodium carbonate, lithium carbonate and niobium pentoxide powder are weighed and mixed in a stoichiometric ratio of (0.5-0.5x):(0.5-0.5x):x:1, and then placed in a polytetrafluoroethylene ball mill jar. Anhydrous ethanol is added and the mixture is ball-milled in a ball mill. The ball-milled wet material is placed in an oven to dry. The dried powder is then ground. The ground powder is placed in an alumina crucible and heated to 850℃~1050℃ at a heating rate of 5℃ / min, and held at that temperature for 1h~6h. The ground powder is then calcined. After calcination, the powder is cooled to room temperature in the furnace to obtain lithium niobate powder doped with potassium and sodium ions. Step 2: The raw material mixture for preparing lithium niobate microcrystals is prepared as follows: Weigh analytically pure potassium chloride, sodium chloride, and the lithium niobate powder doped with potassium and sodium ions obtained in Step 1; place the potassium chloride powder, sodium chloride powder, and lithium niobate powder doped with potassium and sodium ions into a polyethylene ball mill jar in sequence, add anhydrous ethanol, and ball mill; dry the ball-milled wet material in an oven to obtain a dry powder; grind the dry powder into a powder using an agate mortar and pestle to obtain the raw material mixture for preparing lithium niobate microcrystals; the molar ratio of potassium chloride to sodium chloride is 1:1; the mass ratio of the sum of the masses of potassium chloride and sodium chloride to the mass ratio of the lithium niobate powder doped with potassium and sodium ions is 1 to 5:1; Step 3: Preparation of lithium niobate microcrystalline powder. The specific process is as follows: The raw material mixture of lithium niobate microcrystals obtained in Step 2 is placed in an alumina crucible and calcined; after calcination, it is repeatedly washed and filtered in distilled water at 100℃ until Cl is undetectable in the filtrate. - The powder was dried and washed at 80℃ to obtain lithium niobate microcrystalline powder; the calcination process conditions were: calcination at 750℃~1000℃ for 0.5h~4h.
2. The method for preparing lithium niobate microcrystalline powder according to claim 1, characterized in that: In step one, anhydrous ethanol is added and the mixture is ball-milled for 8 to 24 hours; the weight ratio of the anhydrous ethanol to the raw material mixture is 1 to 2:1; the wet material after ball milling is dried at 60°C to 90°C for 5 to 10 hours.
3. The method for preparing lithium niobate microcrystalline powder according to claim 1, characterized in that: In step two, the mass ratio of anhydrous ethanol added to the raw material mixture placed in the polyethylene ball mill jar is 1~2:1, and the ball milling time is 8h~24h; the wet material after ball milling is dried at 60℃~90℃ for 5h~10h.