Method for improving stability of spherical fluoride-coated aluminate luminescent powder

Abstract

This invention discloses a method for improving the stability of aluminate luminescent powder by coating it with spherical fluorides, belonging to the field of optoelectronic materials. The method includes: drying and dispersing the aluminate luminescent powder; introducing spherical fluoride particles into the dispersion system, allowing them to be generated, deposited, adsorbed, and bonded in situ on the surface of the aluminate luminescent powder particles; and obtaining spherical fluoride-coated aluminate luminescent powder through separation, washing, drying, and optional heat treatment. The coating layer does not require continuous dense coverage, but rather forms a dotted, island-like, cluster-like, semi-continuous, or continuous spherical particle coating structure on the surface of the aluminate luminescent powder. This invention can reduce the direct contact between the aluminate luminescent powder and moisture and humid environments, reduce the risk of powder agglomeration and surface hydrolysis, and maintain or improve its luminescence intensity, stability, and storage stability, thus broadening its application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials, specifically relating to a method for improving the hydrolysis resistance, damp heat resistance, anti-agglomeration, and luminescence stability of aluminate luminescent powder by constructing a protective coating structure on the surface of aluminate luminescent powder with spherical fluorides. Background Technology

[0002] Aluminate luminescent powders are an important class of inorganic luminescent materials, among which rare-earth ion-doped alkaline earth metal aluminate luminescent powders are widely used. For example, SrAl₂O₄:Eu 2+ ,Dy 3+ Luminescent powders, represented by these, have advantages such as high luminous brightness, adjustable chemical composition, obvious visible light response, and high visual recognition. They can be used in the fields of luminescent signs, luminescent coatings, safety warnings, decorative materials, anti-counterfeiting materials, and related optoelectronic functional materials.

[0003] However, aluminate luminescent powders still suffer from insufficient stability during actual storage, processing, and application. Because these materials contain an alkaline earth metal aluminate matrix, their surfaces are prone to hydrolysis, ion migration, or interfacial corrosion under the influence of moisture, humid and hot environments, and acidic or alkaline media. This leads to the formation of hydroxylation, carbonation, or other deterioration products on the powder surface. These changes disrupt the local coordination environment around the luminescent centers, resulting in decreased luminescent performance and reduced storage stability, thus limiting their application in aqueous systems, humid environments, and long-term outdoor applications.

[0004] To address the aforementioned issues, existing technologies typically employ methods such as coupling agent treatment, organic resin coating, or inorganic shell coating to modify the surface of aluminate luminescent powders. Coupling agent treatment can improve powder surface compatibility to some extent, but the resulting modified layer is usually thin and has limited durability under water immersion, humid heat, or long-term storage conditions. Organic resin coating can reduce direct contact between the external medium and the luminescent powder, but the resin layer may suffer from insufficient heat resistance, yellowing due to aging, decreased light transmittance, or unstable interfacial bonding with the inorganic powder. Furthermore, an excessively thick organic layer may affect the light output efficiency of the luminescent powder. Inorganic coatings generally offer better heat resistance and chemical stability compared to organic coatings; for example, inorganic layers such as silica, alumina, and titanium dioxide can be used to improve the environmental stability of the powder. However, traditional continuous and dense inorganic shells often require high-level process control, necessitating consideration of shell integrity, thickness uniformity, and interfacial bonding strength. When the shell layer is too thin or the coverage is incomplete, it is difficult to effectively block moisture and corrosive media; when the shell layer is too thick, too dense, or unevenly distributed, it may block the luminescent center, hinder the transmission of excitation or emission light, and induce secondary agglomeration of powder, thus leading to a decrease in luminescence performance. It can be seen that there is still a certain contradiction between "improving environmental stability" and "maintaining luminescence performance" in traditional surface coating technology.

[0005] Therefore, it is necessary to provide a surface modification method for aluminate luminescent powder that is mild and widely applicable, so that it can construct an effective protective interface on the powder surface without relying on a thick, continuous, and dense shell layer, reduce the direct erosion of the aluminate matrix by moisture and humid and hot environments, reduce powder agglomeration, and maintain good luminescence output performance, thereby improving the long-term stability of aluminate luminescent powder in storage, processing, and complex application environments. Summary of the Invention

[0006] I. Purpose of the invention: The purpose of this invention is to provide a method for improving the stability of aluminate luminescent powder by coating it with spherical fluorides. This method uses aluminate luminescent powder as the core particle and constructs a coating layer composed of spherical or near-spherical fluorides on its surface, thereby reducing the direct contact between the aluminate luminescent powder and moisture, humid and hot environments, or chemical media, and improving the luminescent stability of the powder.

[0007] II. Technical Solution:

[0008] To achieve the above objectives, the present invention provides a method for improving the stability of spherical fluoride-coated aluminate luminescent powder, comprising the following steps: Powder pretreatment: The aluminate luminescent powder is dried to remove adsorbed water from the particle surface; then the dried aluminate luminescent powder is dispersed in a solvent to obtain a luminescent powder dispersion. The dispersion can be achieved by mechanical stirring, magnetic stirring, ultrasonic dispersion, grinding dispersion, or a combination thereof.

[0009] Coating layer construction: A dispersion solution containing spherical fluorides is added to the luminescent powder dispersion to allow the spherical fluorides to be generated, deposited, adsorbed, or bonded and fixed in situ on the surface of the aluminate luminescent powder particles, forming a particle-stacking coating layer.

[0010] Post-processing: The reaction system is separated by centrifugation or filtration, and washed with a solvent compatible with the reaction system to remove free spherical fluoride particles not attached to the surface of the aluminate luminescent powder, unreacted metal salt precursors and fluorine source precursors, as well as soluble byproducts generated during the reaction; the washing solvent is selected from ethanol, toluene, isopropanol, ethyl acetate, or combinations thereof. In the system for preparing spherical MgF2 using MgCl2 and NH4F, the unreacted precursors include residual magnesium salts, fluorine sources, or their ionic forms, and the byproducts include soluble salts such as ammonium chloride; the washing solvent is preferably toluene and ethyl acetate. Subsequently, drying is performed, and if necessary, heat treatment, vacuum treatment, or inert atmosphere treatment is carried out to obtain spherical fluoride-coated aluminate luminescent powder.

[0011] The aluminate luminescent powder may be a rare-earth ion-doped alkaline earth metal aluminate luminescent powder, wherein the alkaline earth metal aluminate may include SrAl2O4, Sr4Al 14O 25 CaAl₂O₄, BaAl₂O₄, or combinations thereof. The rare earth ions may include Eu. 2+ Eu 3+ Dy 3+ Ce 3+ 、Tb 3+ 、Sm 3+ Pr 3+ 、Nd 3+ Er 3+ Tm 3+ Yb 3+ One or more of the following. Preferably, the aluminate luminescent powder is SrAl2O4:Eu. 2+ ,Dy 3+ .

[0012] The spherical fluoride particles are selected from MgF2, CaF2, BaF2, SrF2, AlF3, or combinations thereof. Preferably, the spherical fluoride particles are spherical MgF2 particles.

[0013] The spherical fluoride coating layer does not need to completely and densely cover the surface of the aluminate luminescent powder. The spherical fluoride can form a dotted, island-like, clustered, semi-continuous, or continuously distributed particle-stacking coating layer on the surface of the aluminate luminescent powder. This particle-stacking coating layer can form a nanoscale protective interface on the surface of the aluminate luminescent powder, reducing direct contact between moisture, humid and hot environments and the powder surface, while avoiding significant light shading caused by a thick, dense shell.

[0014] In a preferred embodiment, a magnesium source solution and a fluorine source solution are mixed to form a magnesium fluoride nanoparticle dispersion solution. The magnesium source can be magnesium chloride, magnesium nitrate, magnesium acetate, magnesium sulfate, magnesium alkoxide, or a combination thereof; preferably, magnesium chloride is used as the magnesium source. The fluorine source can be ammonium fluoride, sodium fluoride, potassium fluoride, fluoroborate, fluorosilicate, or a combination thereof. Preferably, ammonium fluoride is used as the fluorine source to reduce the risk of using highly corrosive reagents.

[0015] Spherical magnesium fluoride nanoparticles can be formed through controlled precipitation. Specifically, a magnesium source and a fluorine source are reacted in an alcohol-water system or a non-aqueous system to form Mg... 2+ With F − Magnesium fluoride nanoparticles were generated. This was achieved by controlling the concentrations of the magnesium source, fluorine source, and F... − / Mg 2+ The spherical morphology and particle size of magnesium fluoride particles can be adjusted by the molar ratio, solvent composition, pH, dropping rate, stirring speed, type of dispersant, and reaction time.

[0016] The average particle size of the spherical magnesium fluoride nanoparticles is 0.005 μm to 10 μm, preferably 0.02 μm to 2 μm, and more preferably 0.2 μm. If the particle size is too small, it may be difficult to form a stable particle-stabilized protective interface; if the particle size is too large, it may increase additional scattering or cause uneven surface coverage. Therefore, the particle size and deposition amount of the spherical magnesium fluoride can be adjusted according to the particle size of the aluminate luminescent powder itself, the target stability, and the requirements for luminescence retention.

[0017] The solvent may be selected from deionized water, ethanol, methanol, isopropanol, ethylene glycol, toluene, acetone, ethyl acetate, or mixtures thereof.

[0018] The separation method can be centrifugation, filtration, sedimentation, or a combination thereof. The washing solvent can be selected according to the reaction system, such as ethanol, water, toluene, isopropanol, or a combination thereof. The drying temperature can be 30℃ to 120℃, and the drying time can be 1h to 24h. After drying, heat treatment at 100℃ to 600℃, vacuum treatment, or inert atmosphere treatment can be performed as needed to further improve the stability of the coating layer and the storage stability of the powder.

[0019] In this invention, the spherical fluoride particles are not simply mixed into the powder system as fillers, but rather form a stable particle-stacking protective interface on the surface of the aluminate luminescent powder particles. For the spherical magnesium fluoride nanoparticles, they can be fixed to the surface of the aluminate luminescent powder through deposition, adsorption, coordination, or interfacial interactions. Due to the good chemical stability and low water solubility of magnesium fluoride, the distribution of spherical magnesium fluoride nanoparticles on the powder surface reduces the direct contact between moisture, humid and hot environments, and the aluminate matrix, thereby inhibiting surface hydrolysis and interfacial corrosion. Simultaneously, the nano-rough structure and interparticle gaps formed by the spherical particle stacking reduce the tight contact between powder particles, which is beneficial for improving the uniformity of powder dispersion. Since this coating layer does not require the formation of a thick, continuous, dense shell, it can provide protection while reducing the obstruction of the luminescent center and light output path, which is beneficial for maintaining or improving the luminescent stability of the aluminate luminescent powder.

[0020] III. Beneficial Effects:

[0021] Compared with the prior art, the present invention has at least the following beneficial effects.

[0022] First, the present invention uses spherical fluorides as coating units, which can form a stable nano-protective interface on the surface of aluminate luminescent powder, thereby improving hydrolysis resistance and storage stability.

[0023] Secondly, the coating layer of the present invention does not require a continuous and dense shell layer as a necessary condition, which can enhance surface protection while avoiding the obscuring of the light-emitting center, thus helping to maintain or improve the luminescence intensity of aluminates.

[0024] Third, the spherical fluorides form interparticle gaps and nano-rough structures on the powder surface, which helps to reduce the close contact between powder particles and improve the long-term reliability of the powder.

[0025] Fourth, the process of this invention is mild and the raw materials are readily available. It can be adapted to various aluminate luminescent powders by adjusting the type, size, amount, deposition sequence and post-treatment conditions of spherical particles, and has good process adaptability and promotion value. Attached Figure Description

[0026] Figure 1 SrAl2O4:Eu spherical MgF2 particles coated with SrAl2O4:Eu as described in Example 1 2+ ,Dy 3+ The flowchart.

[0027] Figure 2 SrAl2O4:Eu coated with spherical MgF2 particles, as described in Example 1 2+ ,Dy 3+ Scanning electron microscope images.

[0028] Figure 3 SrAl2O4:Eu from Example 1 2+ ,Dy 3+ SrAl2O4:Eu coated with spherical MgF2 particles 2+ ,Dy 3+ Fourier infrared spectrum.

[0029] Figure 4 SrAl2O4:Eu from Example 1 2+ ,Dy 3+ SrAl2O4:Eu coated with spherical MgF2 particles 2+ ,Dy 3+ X-ray photoelectron energy spectrum.

[0030] Figure 5 SrAl2O4:Eu from Example 1 2+ ,Dy 3+ SrAl2O4:Eu coated with spherical MgF2 particles 2+ ,Dy 3+ Photoluminescence spectrum.

[0031] Figure 6 SrAl2O4:Eu from Example 1 2+ ,Dy 3+ SrAl2O4:Eu coated with spherical MgF2 particles 2+ ,Dy 3+ A schematic diagram of the contact angle.

[0032] Figure 7SrAl2O4:Eu from Example 1 2+ ,Dy 3+ SrAl2O4:Eu coated with spherical MgF2 particles 2+ ,Dy 3+ The change in luminescence intensity when the sample is left to stand in water for different durations. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical concept, composition structure, preparation process and application effect of the present invention, and do not constitute a limitation on the scope of protection of the present invention. For those skilled in the art, any equivalent substitution, conventional adjustment or optimized combination of raw material types, proportion ranges, process parameters, hierarchical structure and post-processing methods made without departing from the spirit and substance of the present invention should be considered as falling within the scope of protection of the present invention.

[0034] The "spherical fluoride" described in this invention includes spherical and near-spherical particles. The "coating" is not limited to a completely continuous and dense shell coating, but also includes the dotted, island-like, clustered, semi-continuous, or continuous distribution of spherical fluorides on the surface of aluminate luminescent powder. As long as the spherical fluorides can be fixed to the surface of aluminate luminescent powder through adhesion, deposition, adsorption, bonding, or other means, and can improve the hydrolytic stability, damp heat stability, luminous intensity retention, or storage stability of the aluminate luminescent powder, it belongs to the coating structure described in this invention.

[0035] Example 1:

[0036] With SrAl2O4:Eu 2+ ,Dy 3+ The luminescent powder, as an aluminate luminescent powder matrix, uses magnesium chloride as the magnesium source and ammonium fluoride as the fluorine source. A spherical magnesium fluoride nanoparticle coating layer is constructed on the surface of the luminescent powder through a controlled precipitation process. The preparation process is as follows: Figure 1 As shown.

[0037] S1. Powder drying and dispersion: Weigh 2.0 g of SrAl2O4:Eu 2+ ,Dy 3+ The luminescent powder was dried in a vacuum drying oven at 60℃ for 2 hours to remove adsorbed water from its surface. The dried luminescent powder was then added to 20 mL of toluene solvent and treated with a combination of mechanical stirring and ultrasonic dispersion for 30 minutes to obtain a uniform luminescent powder dispersion.

[0038] S2. Preparation of magnesium source solution: Weigh 0.50 g of magnesium chloride and add it to a mixed solvent consisting of 10 mL of anhydrous ethanol and 0.5 mL of deionized water. Stir until dissolved to obtain the magnesium source solution.

[0039] Preparation of S3 ammonium fluoride solution: Measure 30 mL of anhydrous ethanol and 10 mL of deionized water into a clean PTFE container (avoid using glass containers to prevent HF corrosion). Stir until well mixed. Weigh 1.85 g of NH4F solid and slowly add it to the above solution in batches to prevent clumping. Stir until completely clear. Adjust the pH of the solution to 7.5-8.5 using dilute ammonia (1-5 wt%). Adjusting the pH to a slightly alkaline state can inhibit HF formation and prevent F... - Drastic concentration fluctuations lead to explosive nucleation. Allow to stand at room temperature for 10-15 minutes, then filter using a 0.22 μm membrane to remove any trace amounts of insoluble matter.

[0040] S4. Preparation of spherical magnesium fluoride nanoparticle dispersion: Ammonia water was added to the magnesium source solution in S2 to adjust the pH of the system to 7-9, and then 10 mL of the ammonium fluoride solution obtained in S3 was slowly added dropwise to make F... - With Mg 2+ A controlled precipitation reaction occurs in an ethanol-water system to generate a dispersion of spherical MgF2 nanoparticles. This is achieved by controlling the concentrations of magnesium salt and fluorine source, as well as the F... - / Mg 2+ The molar ratio, ammonia concentration, reaction temperature, dropping rate, stirring speed, and dispersant dosage are adjusted to control the average particle size of the spherical MgF2 particles to be between 0.02 μm and 2 μm, preferably 0.2 μm. After the reaction is complete, stirring at room temperature can continue for 6 h to promote particle crystallization and spheroidization.

[0041] S5, Spherical magnesium fluoride nanoparticles coated with SrAl2O4:Eu 2+ ,Dy 3+ Slowly add 1 mL of the spherical magnesium fluoride nanoparticle dispersion solution obtained in S4 to the powder dispersion solution in S1. During the addition, control the reaction temperature at 40℃ and the stirring speed at 1000 rpm. After the addition is completed, continue stirring at room temperature for 6 h to allow the generated spherical magnesium fluoride nanoparticles to form in the SrAl2O4:Eu 2+ ,Dy 3+ The luminescent powder particles are deposited and adhered to the surface.

[0042] S6. Separation, Washing, and Drying: After the reaction, the solid powder from the S5 system was collected by centrifugation and washed sequentially with toluene and ethyl acetate to remove unreacted precursors, soluble byproducts, and free nanoparticles. The centrifuge parameters were 10,000 rpm and 10 min. The obtained powder was then vacuum-dried at 60 °C for 6 h to obtain SrAl2O4:Eu coated with spherical magnesium fluoride nanoparticles. 2+ ,Dy 3+ Luminescent powder (SrAl2O4:Eu) 2+ ,Dy3+ @MgF2).

[0043] To verify the SrAl2O4:Eu obtained in Example 1 2+ ,Dy 3+ MgF2 powder can be used for morphological characterization. Observation using a scanning electron microscope, such as... Figure 2 As shown, spherical magnesium fluoride nanoparticles can adhere to SrAl2O4:Eu 2+ ,Dy 3+ On the surface of the luminescent powder particles, this coating layer constructs a nanoscale protective interface without completely covering the luminescent powder surface.

[0044] To verify the SrAl2O4:Eu obtained in Example 1 2+ ,Dy 3+ @MgF2 nanoparticles in SrAl2O4:Eu 2+ ,Dy 3+ The surface coating effect and its influence on the local structure of powder can affect SrAl2O4:Eu 2+ ,Dy 3+ SrAl2O4:Eu coated with MgF2 2+ ,Dy 3+ Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were performed on MgF2 powder. Figure 3 It can be seen that SrAl2O4:Eu 2+ ,Dy 3+ A distinct Al–O–Al bond vibration peak appears at 769 cm⁻¹; after coating with MgF₂, this characteristic peak shifts to 786 cm⁻¹, indicating that the introduction of spherical MgF₂ nanoparticles alters the SrAl₂O₄:Eu 2+ ,Dy 3+ The local chemical environment. This peak shift indicates that the MgF2 coating layer is not a simple physical mixture, but may interact with SrAl2O4:Eu through surface adsorption, ionic interactions, or weak coordination. 2+ ,Dy 3+ Surface interactions alter the vibrational environment of Al-O-Al bonds on the powder surface. Further bonding... Figure 4 XPS spectral analysis shows that, compared with SrAl2O4:Eu 2+ ,Dy 3+ Compared to Al2, the Al2 in the MgF2-coated powder pThe binding energy underwent a significant shift (from 73.76 eV in the uncoated sample to 74.02 eV in the coated sample), indicating a change in the electron cloud density and coordination environment around the aluminum element. The peak broadened and exhibited slight asymmetry, consistent with the electronegativity difference-induced electron cloud transfer characteristics during Al-F bond formation. This demonstrates that MgF2 nanoparticles are not simply adsorbed onto SrAl2O4:Eu 2+ ,Dy 3+ Instead of reacting on the surface, the MgF2 coating forms a stable interface with the aluminate matrix through chemical bonding. The blue shift of the FTIR peaks and the shift in the XPS binding energy corroborate each other, indicating that the MgF2 coating can effectively modulate the SrAl2O4:Eu... 2+ ,Dy 3+ The local chemical environment of the surface provides a structural basis for improving its hydrolysis resistance, damp heat resistance, and luminescence retention stability.

[0045] To verify the effect of the MgF2 coating layer in the powder obtained in Example 1 on SrAl2O4:Eu 2+ ,Dy 3+ The effect of luminescence properties on SrAl2O4:Eu 2+ ,Dy 3+ With SrAl2O4:Eu 2+ ,Dy 3+ PL testing was performed on MgF2 powder, and the results are as follows: Figure 5 As shown in the figure. From the figure, it can be seen that SrAl2O4:Eu 2+ ,Dy 3+ @MgF2 and SrAl2O4:Eu 2+ ,Dy 3+ All samples exhibited a significant green emission peak at approximately 520 nm, indicating that the powder retained good luminescent activity after being coated with MgF2 nanoparticles. Furthermore, the luminescence intensity of the coated sample was more than double that of the uncoated sample. This is attributed to the combined effect of the MgF2 coating layer's passivation of surface defects and the interparticle light scattering effect, which improved the luminescence efficiency. These phenomena demonstrate that the MgF2 coating layer not only did not quench the luminescence centers but also effectively enhanced the luminescence efficiency, reflecting the coating layer's enhancing effect on luminescence performance and the structure-performance synergistic optimization mechanism.

[0046] To verify the regulatory effect of the MgF2 coating layer in the powder obtained in Example 1 on the surface wettability of the aluminate luminescent powder, its contact angle can be tested, and the results are as follows: Figure 6As shown in the figure, the contact angle of the uncoated aluminate powder is 8°, exhibiting extremely strong hydrophilicity; while the contact angle of the powder coated with MgF2 increases significantly to 126°, transforming into a typical hydrophobic surface. This indicates that the MgF2 coating layer successfully alters the surface energy of the aluminate powder, effectively reducing surface polarity. Simultaneously, the accumulation of spherical particles forms a nanoscale dual-scale rough structure, making the surface more consistent with the Cassie-Baxter wetting model. Therefore, the coating layer plays a crucial role in regulating the interfacial wettability of powders and enhancing their hydrophobicity to ensure long-term stability.

[0047] To verify the effect of the MgF2 coating obtained in Example 1 on improving the chemical stability and hydrolysis resistance of aluminate luminescent powder in an aqueous environment, SrAl2O4:Eu 2+ ,Dy 3+ With SrAl2O4:Eu 2+ ,Dy 3+ The photoluminescence (PL) spectrum of MgF2 powder after immersion in water was measured, and the results were analyzed in conjunction with contact angle data. Figure 7 As shown. By Figure 7 It is known that the luminescence intensity of uncoated aluminate powder completely quenches after immersion in water for 15 hours, which is closely related to its extremely low contact angle (8°). The superhydrophilic surface allows water molecules to easily penetrate the powder interior, disrupting the coordination environment of the luminescent centers or causing hydrolytic degradation of the aluminate lattice. In contrast, the powder coated with MgF2 can still maintain a high luminescence intensity after immersion in water for up to 360 hours (although there is a certain degree of reduction, it is still far superior to the uncoated sample). This significant hydrophobic property effectively blocks water penetration, avoiding direct contact between the aluminate matrix and water molecules, thereby greatly improving the material's water resistance and long-term stability, demonstrating the excellent protective effect of the coating layer on the luminescent powder in harsh aquatic environments.

[0048] Example 2: The preparation method in this embodiment is the same as in Example 1, except that the mass of magnesium chloride in step S2 is adjusted from 0.5g to 1g; and the volume of ammonium fluoride solution added in step S4 is adjusted from 10 mL to 30 mL. Additionally, the stirring at room temperature for 6 h in step S4 is changed to stirring at 80°C for 6 h, while all other conditions remain unchanged. The remaining steps are the same as in Example 1.

[0049] Example 3: The preparation method in this embodiment is the same as in Embodiment 1, except that: the SrAl2O4:Eu in step S1 is... 2+ ,Dy 3 + Adjusted to BaAl2O4:Eu 2+ ,Dy 3+ .

[0050] Example 4: The preparation method in this embodiment is the same as in Example 1, except that step S2 is replaced by weighing 0.55 g of calcium chloride and adding it to a mixed solvent consisting of 10 mL of anhydrous ethanol and 0.5 mL of deionized water, stirring until completely dissolved to obtain a calcium source solution. The remaining steps are the same as in Example 1.

[0051] Example 5: The preparation method in this embodiment is the same as in Embodiment 4, except that: the SrAl2O4:Eu in step S1 is... 2+ ,Dy 3+ Adjusted to BaAl2O4:Eu 2+ ,Dy 3+ .

[0052] Comparative Example 1: Take SrAl2O4:Eu without any coating treatment 2+ ,Dy 3+ The powder was used as Comparative Example 1.

[0053] Comparative Example 2: Take BaAl2O4:Eu without any coating treatment 2+ ,Dy 3+ The powder was used as comparative example 2.

[0054] The powders from Examples 1-5 and Comparative Examples 1-2 were tested as follows: Table 1 Contact angle 126° 124° 117° 110° 114° 8° 10° PL strength 18806 15744 5012 14858 3469 9324 2645 It glows after being immersed in water for 360 hours. have have have have have none none As shown in Table 1, the samples obtained in Examples 1-5 all have larger water contact angles, which are higher than those in Comparative Examples 1 and 2. This indicates that after coating with the spherical fluoride particles of the present invention, the hydrophobicity of the aluminate luminescent powder surface is significantly improved, which can effectively reduce the direct contact between water and the surface of the luminescent powder, thereby mitigating the adverse effects of hydrolysis or humid and hot environments on luminescence performance. Meanwhile, the PL intensities in Examples 1-5 are 18806, 15744, 5012, 14858, and 3469, respectively, all higher than the corresponding comparative examples, indicating that the coating structure of the present invention can not only improve the surface stability of the powder, but also maintain or enhance the luminescence intensity to a certain extent. Furthermore, the samples in Examples 1-5 still showed luminescence after immersion in water for 360 h, while no luminescence was observed in Comparative Examples 1 and 2 under the same conditions, indicating that the coated aluminate luminescent powder obtained by the present invention has excellent water immersion stability and long-term luminescence retention capability. Based on the combined contact angle, PL intensity, and luminescence results after immersion in water for 360 hours, it can be seen that the present invention effectively improves the hydrophobicity, luminescence intensity, and water resistance of the aluminate luminescent powder by constructing a spherical fluoride coating layer on the surface of the aluminate luminescent powder. It can significantly improve the problems of easy hydrolysis and rapid luminescence decay of aluminate luminescent powder in humid or water-contact environments, and can effectively improve the hydrolysis resistance, damp heat resistance, and luminescence retention stability of aluminate luminescent powder.

[0055] It should be emphasized that the spherical MgF2 in the embodiments is a preferred embodiment of the spherical fluoride coating structure of the present invention, and is not a limitation on the scope of protection of the present invention. Other materials that can form spherical or near-spherical fluoride coating layers and can improve luminous efficiency, enhance environmental adaptability and stability can be used as equivalent or alternative embodiments of the present invention.

[0056] Supplementary Explanation of Implementation Steps To further meet the requirements of full disclosure in the patent text, the types of raw materials, concentration ranges, time conditions, temperature conditions, equipment types, process sequences, and post-processing methods in the above embodiments can be adaptively adjusted according to the specific types of luminescent powders, spherical particles, and application scenarios.

[0057] The terms "preferred," "further preferred," "optional," and "in some embodiments" used in this specification are only used to describe different implementation levels of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0058] Without altering the core technical concept of "a method for improving the stability of spherical fluoride-coated aluminate luminescent powder," the above embodiments can be implemented individually or in combination. All combinations, substitutions, modifications, and improvements based on the concept of this invention should be considered to fall within the scope of disclosure and protection of this invention.

Claims

1. A method for improving the stability of spherical fluoride-coated aluminate luminescent powder, characterized in that, Includes the following steps: Aluminate luminescent powder is dispersed in a solvent to obtain a luminescent powder dispersion. The weight ratio of aluminate luminescent powder to solvent can be 1:5 to 1:

20. Subsequently, a dispersion solution containing spherical fluorides is added to the luminescent powder dispersion to allow the spherical fluorides to be deposited, adsorbed, and bonded to the surface of the aluminate luminescent powder particles. The amount of spherical fluoride dispersion added is 1% to 20% of the aluminate luminescent powder dispersion, which is adjusted according to the particle size of the luminescent powder and the target coating thickness. After separation, washing, and drying, spherical fluoride-coated aluminate luminescent powder is obtained. The spherical fluorides form dot-like, island-like, cluster-like, semi-continuous, or continuous coating layers on the surface of the aluminate luminescent powder. These coating layers improve the aluminate luminescent powder's hydrolytic stability, damp heat stability, or luminescence retention stability. The spherical fluoride coating layer does not require continuous and dense coverage.

2. The method according to claim 1, characterized in that, The aluminate luminescent powder is a rare-earth ion-doped alkaline earth metal aluminate luminescent powder, wherein the aluminate is selected from strontium aluminate (chemical formula SrAl2O4) and tetrastrontium aluminate (chemical formula Sr4Al). 14 O 25 ), calcium aluminate (chemical formula CaAl2O4), barium aluminate (chemical formula BaAl2O4), or combinations thereof; the activating ions or co-activating ions in the rare earth ion-doped alkaline earth metal aluminate luminescent powder include europium(II) ions (chemical formula Eu). 2+ Europium(III) ions (chemical formula represented as Eu) 3+ ), dysprosium ion (chemical formula represented as Dy) 3+ ), cerium ions (chemical formula represented as Ce) 3+ ), terbium ions (chemical formula represented as Tb) 3+ Samarium ions (chemical formula represented as Sm) 3+ ), praseodymium ion (chemical formula represented as Pr) 3+ Neodymium ions (chemical formula Nd) 3+ Erbium ion (chemical formula represented as Er) 3+ Thulium ion (chemical formula represented as Tm) 3+ Ytterbium ion (chemical formula represented as Yb) 3+ One or more of the following: SrAl2O4:Eu 2+ ,Dy 3+ .

3. The spherical fluoride coating method according to claim 1, characterized in that, The spherical fluoride particles are selected from magnesium fluoride (chemical formula MgF2), calcium fluoride (chemical formula CaF2), barium fluoride (chemical formula BaF2), strontium fluoride (chemical formula SrF2), aluminum fluoride (chemical formula AlF3), or combinations thereof. Preferably, the spherical fluoride particles are spherical MgF2 particles.

4. The method according to claim 3, characterized in that, The average particle size of the spherical fluoride particles is 0.005 μm to 10 μm, preferably 0.02 μm to 2 μm, and more preferably 0.2 μm.

5. The method according to any one of claims 1 to 4, characterized in that, When the spherical fluoride is spherical MgF2, the magnesium salt and fluorine source are subjected to controlled precipitation in an alcohol-water system or a non-aqueous system to obtain a dispersion containing spherical MgF2; the magnesium salt is selected from magnesium chloride (chemical formula MgCl2), magnesium nitrate (chemical formula Mg(NO3)2), magnesium acetate (chemical formula Mg(OAc)2), magnesium sulfate (chemical formula MgSO4) or magnesium alkoxide, and the fluorine source is selected from ammonium fluoride (chemical formula NH4F), sodium fluoride (chemical formula NaF), potassium fluoride (chemical formula KF), fluorosilicate or fluoroborate.

6. The method according to claim 5, characterized in that, In the controlled precipitation reaction, the molar ratio of fluoride ions to magnesium ions is 1.5:1 to 3.0:1, preferably 1.8:1 to 2.4:1; the concentration of the magnesium source in the reaction system is 0.005 mol / L to 1.0 mol / L, preferably 0.02 mol / L to 0.3 mol / L.

7. The method according to claims 1 to 6, characterized in that, The solvent is selected from deionized water, ethanol, methanol, isopropanol, ethylene glycol, toluene, acetone, ethyl acetate, or mixtures thereof.

8. The method according to any one of claims 1 to 7, characterized in that, The drying temperature is 30℃~120℃, and the drying time is 1 h~24 h; after drying, it can also be optionally subjected to heat treatment at 100℃~600℃, vacuum treatment or inert atmosphere treatment.

9. A spherical fluoride-coated aluminate luminescent powder prepared by the method according to any one of claims 1 to 8, characterized in that, The aluminate luminescent powder particles have a spherical fluoride coating layer on their surface, and the spherical fluoride coating layer forms a protective interface structure through the accumulation of spherical particles and the gaps between particles.

10. The spherical fluoride-coated aluminate luminescent powder according to claim 9, characterized in that, The luminescence intensity retention rate of the spherical fluoride-coated aluminate luminescent powder after water contact, damp heat aging, or long-term storage at room temperature is higher than that of the uncoated aluminate luminescent powder, and its contact angle, wettability, or luminescence brightness are better than those of the uncoated aluminate luminescent powder.

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