A long afterglow fluorescent material with uniform particle size distribution and preparation method thereof

Abstract

The present invention relates to a long afterglow fluorescent material with uniform particle size distribution and a preparation method thereof. The fluorescent material has a structural formula M 1‑x‑y Al2O4:xEu 2+ ,yR 3+ , wherein M is any one of Sr, Ca, or Ba, and R is any one of Dy, Sm, Tm, Nd, and La, and the D50 of the long afterglow luminescent material is 6.0-8.5μm, D10≥1μm, and D90≤9.5μm. Citric acid and ethylenediaminetetraacetic acid are used as double chelating agents, combined with the use of surfactants, to effectively control the agglomeration of particles in the solution and achieve excellent dispersibility of the product. Through a two-step heat treatment process of pre-calcination and roasting under a reducing atmosphere, and using an airflow crushing classifier instead of traditional ball milling, the damage to the luminescent center is avoided, the luminescent quality of the material is guaranteed, and a fluorescent material with uniform particle size distribution and high luminous efficiency is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of fluorescent materials, and in particular to a long afterglow fluorescent luminescent material with uniform particle size distribution and a preparation method thereof. Background Art

[0002] Long afterglow materials have attracted much attention because they can continue to glow for hours or even days after the external excitation light source disappears. The luminescence characteristics of these materials make them have wide application potential in many fields, such as night lighting, safety instructions, emergency evacuation route markings, and transportation and storage industries that require long-term marking. 2+ , Nd 3+ and SrAl2O4:Eu 2+ ,Dy 3+ For example, their blue light afterglow can last for more than 19 hours and 30 hours respectively, which demonstrates the excellent performance of long afterglow materials under specific conditions.

[0003] However, the luminescence performance of long afterglow materials is not only affected by their physical and chemical properties, but also by their preparation methods. Different preparation methods will lead to differences in the uniformity of the doping elements in the material, the particle size and the particle size distribution, which are directly related to the luminescence efficiency, brightness, attenuation characteristics and afterglow duration of the material. For example, uniform doping can ensure that the material emits more uniformly after excitation, while the appropriate particle size and particle size distribution can help improve the luminescence brightness of the material and reduce the scattering of light, thereby improving the overall luminescence performance. Therefore, optimizing the preparation process of long afterglow materials, such as precisely controlling the synthesis conditions, selecting appropriate doping elements and proportions, and using efficient crushing and grading techniques, is crucial to obtaining high-performance long afterglow materials.

[0004] As a traditional method for preparing rare earth long afterglow luminescent materials, the high temperature solid phase method has the advantages of simple operation and low cost, but its limitations cannot be ignored. During the high temperature sintering process, the raw materials are prone to agglomeration, resulting in uneven grain growth, which in turn affects the luminescent properties of the material. The unevenness of the grains will lead to a decrease in luminescent brightness, and long-term high temperature treatment may It will cause excessive growth of grains, forming larger grains, increasing the hardness of the material, which is not conducive to subsequent processing and application. In addition, the crystal shape of the materials prepared by the high-temperature solid-phase method may be destroyed after ball milling, affecting the microstructure and optical properties of the material. This will not only reduce the luminescence brightness of the material, but may also change its luminescence color and afterglow time. Therefore, in order to obtain higher quality long afterglow luminescent materials, it is necessary to explore more sophisticated synthesis methods, such as sol-gel method, co-precipitation method, etc. These methods can be carried out at lower temperatures, which help to obtain more uniform grain size and better luminescence performance. By continuously optimizing and improving the preparation process, the application potential and market competitiveness of long afterglow materials can be improved.

[0005] Therefore, how to improve the afterglow performance while maintaining the small particle size and uniform size of long afterglow nanomaterials is still a major challenge in the current application and development of long afterglow nanomaterials. By precisely controlling the distribution and concentration of doping elements, optimizing the lattice structure, and achieving uniform particle size distribution, it is expected to achieve breakthroughs in the luminous efficiency, brightness, and duration of the material, paving the way for the commercial application of long afterglow nanomaterials. Summary of the invention

[0006] The long afterglow fluorescent luminescent material and preparation method thereof of the present invention realize effective control of solution particle agglomeration by using citric acid and ethylenediaminetetraacetic acid as double chelating agents and a surfactant. The synergistic effect of the double chelating agents not only prevents the aggregation of nanoparticles, but also significantly improves the dispersibility of the product. Due to the uniform dispersion of the nanoparticles, the fluorescent material exhibits a more uniform particle size distribution, which helps to reduce light scattering and improve luminous efficiency, so that the fluorescent material performs well in terms of luminous brightness, afterglow time and stability.

[0007] The general structural formula of the long afterglow fluorescent material with uniform particle size distribution of the present invention is M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where M is any one of Sr, Ca, or Ba, R is any one of Dy, Sm, Tm, Nd, and La, and x and y represent Eu 2+ and R 3+ The molar ratio of 0.005≤x≤0.05, 0.005≤y≤0.05. The D50 of the long afterglow luminescent material is 6.0-8.5 μm, D10≥1 μm, and D90≤9.5 μm.

[0008] The present invention also relates to a method for preparing a long afterglow fluorescent material with uniform particle size distribution, which specifically comprises the following steps:

[0009] (1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , using M, Al, Eu, R soluble raw materials, using deionized water to dissolve the raw materials to prepare a mixed solution, the solid-liquid ratio of the mixed solution is 1:1-3; then adding chelating agent of 5-30% of the total mass of M, Al, Eu, R soluble raw materials to the mixed solution, stirring and mixing evenly to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:0.5-3.

[0010] (2) The premixed solution obtained in step 1) is stirred and mixed with a surfactant at 50 to 80° C., a pH adjuster is added until the pH of the solution is 5 to 7, stirring is continued, filtering, and drying to obtain a precursor powder; the mass ratio of the surfactant to the chelating agent is 1:1 to 5.

[0011] (3) The precursor powder is pre-calcined at 300°C to 600°C for 1 to 3 hours, then calcined at 900°C to 1200°C in a reducing atmosphere for 1 to 5 hours, cooled to room temperature, and crushed in an air flow pulverizing and classifying machine to obtain a long afterglow luminescent material.

[0012] In the step (1), the mass ratio of citric acid to ethylenediaminetetraacetic acid is preferably 1:1 to 2.5.

[0013] The pH regulator in step (2) is one or more of ammonia water, urea, and sodium bicarbonate.

[0014] In the step (2), the surfactant is one or more of polyethylene glycol, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate, and the polyethylene glycol includes one or more of polyethylene glycol 2000, polyethylene glycol 3000, polyethylene glycol 4000, polyethylene glycol 5000, and polyethylene glycol 6000.

[0015] The soluble raw materials of M, Al, Eu and R are nitrates.

[0016] The stirring and mixing time in step (2) is 0.5 to 3 hours at 50 to 80°C.

[0017] The drying in step (2) is carried out in a vacuum drying oven, and the temperature of the drying oven is 80 to 130°C.

[0018] Furthermore, the precursor powder of step (3) is preferably pre-calcined at 300°C to 400°C for 1 to 2 hours, and then calcined at 900°C to 1000°C in a reducing atmosphere for 1 to 3 hours.

[0019] In the present invention, the mass ratio of the surfactant to the chelating agent is 1:1-5. This ratio range helps to control the dispersion and stability of the solution, thereby affecting the particle size and luminescent properties of the final material.

[0020] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0021] 1) The present invention uses citric acid and ethylenediaminetetraacetic acid as double chelating agents, and can effectively prevent nanoparticles from agglomerating in combination with surfactants, thereby ensuring excellent dispersibility of the product, and making the particle size distribution range of the sample narrow and the particle size more uniform. Since the surfactant molecules have non-polar lipophilic groups and polar hydrophilic groups, the particles can be effectively prevented from approaching, and the surfactant will decompose into gas and release during the pre-burning process, which is also conducive to forming a loose powder without hard agglomeration.

[0022] 2) The present invention pre-sinters the precursor powder at 300°C to 600°C to remove organic impurities and promote initial crystallization, and then roasts it at 900°C to 1200°C in a reducing atmosphere. This step is crucial to the formation of the crystal phase and luminescence center of the fluorescent material, avoids secondary agglomeration of the afterglow material product, makes the particle size distribution of the fluorescent material more uniform, reduces the scattering of light caused by different particle sizes, and increases the fluorescent properties of the material.

[0023] 3) The present invention uses an air flow pulverizing classifier for pulverizing. Compared with the ball milling method, it can avoid the damage to the luminous center of the product caused by grinding, thereby ensuring the luminous quality of the product. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0025] The technical solution of the present invention is further described below through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0026] Example 1

[0027] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0028] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ Sm 3+First, weigh 11.640g of Sr(NO3)2, 41.264g of Al(NO3)3·9H2O, 0.491g of Eu(NO3)3·6H2O, and 0.369g of Sm(NO3)3, and dissolve them in deionized water with a solid-liquid ratio of 1:1.5; then add 10% of the total mass of Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Sm(NO3)3 (5.37g), stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:1;

[0029] 2) The premix obtained in step 1) was stirred with PEG2000 at 50° C. for 1 h, and aqueous ammonia was added until the pH of the solution was 6. The stirring was continued for 3 h, filtered, and vacuum dried at 100° C. for 2 h to obtain a precursor powder; the mass ratio of PEG2000 to the chelating agent was 1:1.

[0030] 3) The precursor powder was pre-calcined at 400°C for 2h, then calcined at 900°C in a reducing atmosphere for 4h, cooled to room temperature, and crushed in a jet mill classifier to obtain Sr 0.96 Al2O4:0.02Eu 2+ ,0.02Sm 3+ Long afterglow luminescent materials.

[0031] Example 2

[0032] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0033] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ Sm 3+ First, weigh 11.640g of Sr(NO3)2, 41.264g of Al(NO3)3·9H2O, 1.228g of Eu(NO3)3·6H2O, and 0.923g of Sm(NO3)3, and dissolve them in deionized water with a solid-liquid ratio of 1:2; then add 15% of the total mass of Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Sm(NO3)3 in a chelating agent (8.26g), stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:1.5;

[0034] 2) The premix obtained in step 1) was stirred with PEG4000 at 60° C. for 1 h, and aqueous ammonia was added until the pH of the solution was 5, and stirring was continued for 3 h. The mixture was filtered and vacuum dried at 110° C. for 2 h to obtain a precursor powder; the mass ratio of PEG4000 to the chelating agent was 1:1.2.

[0035] 3) The precursor powder was pre-calcined at 500°C for 1.5 h, then calcined at 1000°C in a reducing atmosphere for 3 h, cooled to room temperature, and crushed in a jet mill classifier to obtain Sr 0.9 Al2O4:0.05Eu 2+ ,0.05Sm 3+ Long afterglow luminescent materials.

[0036] Example 3

[0037] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0038] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ Sm 3+ First, weigh 9.025g of Ca(NO3)2, 41.264g of Al(NO3)3·9H2O, 0.123g of Eu(NO3)3·6H2O, and 0.093g of Sm(NO3)3, and dissolve them in deionized water with a solid-liquid ratio of 1:2; then add chelating agent (10.10g) with a total weight of 20% of Ca(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Sm(NO3)3, stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid with a mass ratio of 1:2;

[0039] 2) The premixed solution obtained in step 1) was stirred and mixed with sodium dodecylbenzene sulfonate at 70° C. for 1 h, urea was added until the pH of the solution was 5, stirring was continued for 2.5 h, filtered, and vacuum dried at 90° C. for 3 h to obtain a precursor powder; the mass ratio of sodium dodecylbenzene sulfonate to the chelating agent was 1:2.

[0040] 3) The precursor powder was pre-calcined at 400°C for 2 h, then calcined at 1100°C in a reducing atmosphere for 2.5 h, cooled to room temperature, and crushed in a jet mill classifier to obtain Ca 0.99 Al2O4:0.005Eu 2+ ,0.005Sm 3+ Long afterglow luminescent materials.

[0041] Example 4

[0042] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0043] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ Sm 3+ First, weigh 16.971g of Ba(NO3)2, 45.012g of Al(NO3)3·9H2O, 0.535g of Eu(NO3)3·6H2O, and 0.404g of Sm(NO3)3, and dissolve them in deionized water with a solid-liquid ratio of 1:3; then add chelating agent (23.96g) of 30% of the total mass of Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Sm(NO3)3, stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:2;

[0044] 2) The premixed solution obtained in step 1) was stirred and mixed with sodium dodecyl sulfate at 50° C. for 1 h, sodium bicarbonate was added until the pH of the solution was 5, stirring was continued for 3 h, filtered, and vacuum dried at 110° C. for 2 h to obtain a precursor powder; the mass ratio of sodium dodecyl sulfate to the chelating agent was 1:2.5.

[0045] 3) The precursor powder was pre-calcined at 600°C for 2h, then calcined at 900°C in a reducing atmosphere for 4h, cooled to room temperature, and crushed in a jet mill classifier to obtain Ba 0.96 Al2O4:0.02Eu 2+ ,0.02Sm 3+ Long afterglow luminescent materials.

[0046] Example 5

[0047] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0048] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ For Dy 3+First, weigh 10.582g of Sr(NO3)2, 37.512g of Al(NO3)3·9H2O, 0.446g of Eu(NO3)3·6H2O, and 0.349g of Dy(NO3)3, and dissolve them in deionized water with a solid-liquid ratio of 1:1.5; then add 10% of the total mass of Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Dy(NO3)3 (4.89g), stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:1;

[0049] 2) The premix obtained in step 1) was stirred with PEG2000 at 50° C. for 1 h, and aqueous ammonia was added until the pH of the solution was 6. The stirring was continued for 3 h, filtered, and vacuum dried at 100° C. for 2 h to obtain a precursor powder; the mass ratio of PEG2000 to the chelating agent was 1:1.

[0050] 3) The precursor powder was pre-calcined at 400°C for 2h, then calcined at 900°C in a reducing atmosphere for 4h, cooled to room temperature, and crushed in a jet mill classifier to obtain Sr 0.96 Al2O4:0.02Eu 2+ ,0.02Dy 3+ Long afterglow luminescent materials.

[0051] Example 6

[0052] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0053] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ For Dy 3+ First, weigh 10.582g of Sr(NO3)2, 37.512g of Al(NO3)3·9H2O, 1.115g of Eu(NO3)3·6H2O, and 0.873g of Dy(NO3)3, and dissolve them in deionized water with a solid-liquid ratio of 1:1.5; then add 15% of the total mass of Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Dy(NO3)3 in a chelating agent (7.51g), stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:1.5;

[0054] 2) The premix obtained in step 1) was stirred with PEG2000 at 50° C. for 1 h, and aqueous ammonia was added until the pH of the solution was 6. The stirring was continued for 3 h, filtered, and vacuum dried at 100° C. for 2 h to obtain a precursor powder; the mass ratio of PEG2000 to the chelating agent was 1:1.

[0055] 3) The precursor powder was pre-calcined at 400°C for 2h, then calcined at 900°C in a reducing atmosphere for 4h, cooled to room temperature, and crushed in a jet mill classifier to obtain Sr 0.9 Al2O4:0.05Eu 2+ ,0.05Dy 3+ Long afterglow luminescent materials.

[0056] Example 7

[0057] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0058] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ Tm 3+ First, weigh 12.698g of Sr(NO3)2, 45.016g of Al(NO3)3·9H2O, 0.552g of Eu(NO3)3·6H2O, and 0.556g of Tm(NO3)3·6H2O, and dissolve them in deionized water with a solid-liquid ratio of 1:2; then add chelating agent (11.76g) of 20% of the total mass of Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Tm(NO3)3·6H2O, stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:1.2;

[0059] 2) The premix obtained in step 1) was stirred with PEG4000 at 45° C. for 1 h, aqueous ammonia was added until the pH of the solution was 6, stirring was continued for 2 h, filtered, and vacuum dried at 100° C. for 2 h to obtain a precursor powder; the mass ratio of PEG2000 to the chelating agent was 1:1.1.

[0060] 3) The precursor powder was pre-calcined at 450°C for 2h, then calcined at 1000°C in a reducing atmosphere for 4h, cooled to room temperature, and crushed in a jet mill classifier to obtain Sr 0.96 Al2O4:0.02Eu 2+ ,0.02Tm 3+ Long afterglow luminescent materials.

[0061] Example 8

[0062] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0063] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,yR 3+ , where R 3+ Nd 3+ First, weigh 13.754g of Sr(NO3)2, 48.763g of Al(NO3)3·9H2O, 0.598g of Eu(NO3)3·6H2O, and 0.569g of Nd(NO3)3·6H2O, and dissolve them in deionized water with a solid-liquid ratio of 1:2; then add 15% of the total mass of Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Nd(NO3)3·6H2O in a chelating agent (9.55g), stir and mix well to obtain a premixed solution; the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:1.3;

[0064] 2) The premix obtained in step 1) was stirred with PEG2000 at 60° C. for 1 h, and aqueous ammonia was added until the pH of the solution was 5, and stirring was continued for 2.5 h. The mixture was filtered and vacuum dried at 100° C. for 2 h to obtain a precursor powder; the mass ratio of PEG2000 to the chelating agent was 1:1.1.

[0065] 3) The precursor powder was pre-calcined at 450°C for 2h, then calcined at 1000°C in a reducing atmosphere for 4h, cooled to room temperature, and crushed in a jet mill classifier to obtain Sr 0.96 Al2O4:0.02Eu 2+ ,0.02Nd 3+ Long afterglow luminescent materials.

[0066] Example 9

[0067] The difference from Example 5 is that in step 1), the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:0.5, and the rest is the same as Example 5.

[0068] Example 10

[0069] The difference from Example 5 is that in step 1), the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:1.5, and the rest is the same as Example 5.

[0070] Embodiment 11

[0071] The difference from Example 5 is that in step 1), the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:2, and the rest is the same as Example 5.

[0072] Example 12

[0073] The difference from Example 5 is that in step 1), the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:2.5, and the rest is the same as Example 5.

[0074] Example 13

[0075] The difference from Example 5 is that in step 1), the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:3, and the rest is the same as Example 5.

[0076] Comparative Example 1

[0077] The difference from Example 5 is that no chelating agent is added in step 1), and the rest is the same as Example 5.

[0078] Comparative Example 2

[0079] The difference from Example 5 is that no surfactant is added in step 2), and the rest is the same as Example 5.

[0080] Comparative Example 3

[0081] The difference from Example 5 is that in step 1), the chelating agent is all citric acid, that is, an equal amount of citric acid is used instead of ethylenediaminetetraacetic acid, and the rest is the same as Example 5.

[0082] Comparative Example 4

[0083] The difference from Example 5 is that in step 1), the chelating agent is all ethylenediaminetetraacetic acid, that is, an equal amount of ethylenediaminetetraacetic acid is used instead of citric acid, and the rest is the same as Example 5.

[0084] Comparative Example 5

[0085] The difference from Example 5 is that the step of pre-calcining the precursor powder at 400° C. for 2 h is omitted, and the precursor powder is directly calcined at 900° C. for 4 h in a reducing atmosphere. The rest is the same as Example 5.

[0086] Comparative Example 6

[0087] A method for preparing a long afterglow fluorescent material with uniform particle size distribution, specifically comprising the following steps:

[0088] 1) According to the general formula M 1-x-y Al2O4:xEu 2+ ,ySm 3+First, weigh Sr(NO3)211.640g, Al(NO3)3·9H2O41.264g, Eu(NO3)3·6H2O 0.491g, and Sm(NO3)30.369g, mix the above Sr(NO3)2, Al(NO3)3·9H2O, Eu(NO3)3·6H2O, and Sm(NO3)3 in an agate mortar, add a certain amount of boric acid and ethanol, mix thoroughly, and dry to prepare a precursor powder.

[0089] 3) The precursor powder was pre-calcined at 400°C for 2h, then calcined at 900°C in a reducing atmosphere for 4h, cooled to room temperature, and crushed in a jet mill classifier to obtain Sr 0.96 Al2O4:0.02Eu 2+ ,0.02Sm 3+ Long afterglow luminescent materials.

[0090] Test result analysis:

[0091] Afterglow time: First, place the sample in a dark environment for at least 24 hours, then irradiate it under a D65 light source for 60 minutes, and then test its continuous luminescence time.

[0092] Afterglow decay rate: Calculate the afterglow decay rate by testing the initial luminous intensity of the afterglow and the afterglow luminous intensity at 60 minutes.

[0093] Particle size distribution of the product: The particle size of the sample is analyzed using a laser particle size analyzer.

[0094] Afterglow brightness of the product: Test the brightness of the material by irradiating it under sunlight for 30 minutes.

[0095] The particle size, specific afterglow time, afterglow decay rate and afterglow brightness of the long afterglow materials prepared in the above-mentioned embodiments and comparative examples are compared, as shown in Table 1 below.

[0096] Table 1 Performance of long afterglow luminescent materials in different embodiments and comparative examples

[0097]

[0098] According to the performance test results in Table 1, the long afterglow luminescent material prepared by the embodiment of the present invention exhibits excellent particle size distribution characteristics, wherein the D50 particle size range is 6.0-8.5 μm, D10 ≥ 1 μm, and D90 ≤ 9.5 μm, indicating that the particle size distribution of the material is very uniform. This uniform particle size distribution is crucial to the optical properties of the material because it can ensure that the material has consistent brightness and attenuation characteristics when emitting light. Further comparative experiments in Examples 5, 9-13 show that the mass ratio of citric acid and ethylenediaminetetraacetic acid has a significant effect on the particle size distribution of the long afterglow luminescent material and the optical properties such as afterglow luminescence time and afterglow decay rate. When the mass ratio of the two compounds is controlled between 1:1 and 2.5, long afterglow luminescent materials with more uniform particle size distribution can be prepared, and these materials exhibit better afterglow luminescence time and lower afterglow decay rate. The excellent performance of this material makes it have potential application value in a variety of application fields, such as safety signs, emergency lighting, and occasions requiring long-term luminous indication.

[0099] After an in-depth comparison between Example 5 and Comparative Examples 1, 3-4, it can be clearly observed that the dual chelating agent of citric acid and ethylenediaminetetraacetic acid has a significant synergistic effect in improving the particle size distribution and optical properties of the fluorescent material. Example 5 uses a combination of citric acid and ethylenediaminetetraacetic acid, which can obtain a more uniform particle size distribution compared to Comparative Examples 3-4 using any one of the citric acid and ethylenediaminetetraacetic acid alone. In addition, the use of the dual chelating agent composed of citric acid and ethylenediaminetetraacetic acid also helps to increase the afterglow luminescence time of the material and reduce the afterglow decay rate, thereby providing a more lasting and more stable luminescence effect in practical applications.

[0100] In the comparative analysis of Example 5 and Comparative Example 2, it can be found that the samples with added surfactants show more superior optical properties in terms of particle size distribution, afterglow luminescence time, afterglow decay rate and afterglow brightness. This improvement is mainly attributed to the amphiphilic characteristics of the surfactant molecules, that is, they have both non-polar lipophilic groups and polar hydrophilic groups. In the mixed solution system, the amphiphilic nature of the surfactant enables it to form a protective film on the surface of the particles, which effectively prevents the aggregation of particles through the steric hindrance effect, thereby maintaining the uniform dispersion of the particles. This uniform dispersion not only helps to obtain a narrower particle size distribution range, but also has a positive effect on the optical properties of the material. The decomposition of the surfactant during the pre-burning process further promotes the formation of loose, non-hard agglomerate powder, which helps to improve the luminous efficiency and stability of the material. In addition, the addition of the surfactant also enhances the luminous intensity of the phosphor, mainly because the uniformity of the particle size distribution reduces the light scattering caused by different particle sizes, thereby improving the luminous efficiency of the material.

[0101] When comparing Example 5 with Comparative Example 6, Comparative Example 6 uses a traditional high-temperature solid-phase method to prepare a rare earth long-lasting fluorescent material. This method usually leads to uneven particle size distribution, especially a high content of fine particle size products. This particle size distribution not only affects the uniformity of the material, but also leads to a decrease in the afterglow decay rate and afterglow brightness of the fluorescent material.

[0102] The comparative analysis of Example 5 and Comparative Example 5 reveals the important influence of the pre-sintering and roasting processes on the performance of the fluorescent material. In Example 1, the precursor powder is first pre-sintered at a temperature range of 300°C to 600°C. This step effectively removes organic impurities in the fluorescent material and promotes the initial crystallization of the material. Therefore, pre-sintering not only helps to improve the purity of the material, but also lays the foundation for subsequent high-temperature treatment, is conducive to the formation of the crystalline phase and luminescent center of the material during the reduction calcination process, and helps to maintain the crystalline structure of the active elements in the material, thereby optimizing its luminescent performance. The calcined material is further processed by airflow crushing and classification process, which ensures the uniformity of the particle size distribution of the final product.

[0103] In summary, the two-step heat treatment process adopted in the present invention, namely pre-calcination and roasting, and subsequent air flow crushing and classification, act together on the microstructure and macroscopic properties of the material, thereby achieving a more uniform particle size distribution and better luminescence performance.

[0104] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a long afterglow fluorescent material with uniform particle size distribution, characterized in that: The general structural formula of the fluorescent material is M 1-x-y Al2O4:xEu 2+ ,yR 3+ , wherein M is any one of Sr, Ca, or Ba, R is any one of Dy, Sm, Tm, Nd, and La, 0.005≤x≤0.05, 0.005≤y≤0.05; The preparation method of the fluorescent material comprises the following steps: (1) using M, Al, Eu, and R soluble raw materials, dissolving the raw materials in deionized water to prepare a mixed solution, wherein the solid-liquid ratio of the mixed solution is 1:1-3, then adding a chelating agent in an amount of 5-30% of the total mass of the M, Al, Eu, and R soluble raw materials, stirring and mixing uniformly to obtain a premixed solution, wherein the chelating agent is citric acid and ethylenediaminetetraacetic acid in a mass ratio of 1:0.5-3; (2) stirring the premix obtained in step 1 and a surfactant at 50 to 80° C., adding a pH adjuster until the pH of the solution is 5 to 7, continuing stirring, filtering, and drying to obtain a precursor powder, wherein the mass ratio of the surfactant to the chelating agent is 1:1 to 5; the surfactant is one or more of polyethylene glycol, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate; (3) The precursor powder obtained in step 2 is pre-calcined at 300°C to 600°C for 1 to 3 hours, then calcined at 900°C to 1200°C in a reducing atmosphere for 1 to 5 hours, cooled to room temperature, and crushed in an air flow pulverizing and classifying machine to obtain a long afterglow luminescent material.

2. The method for preparing a long afterglow fluorescent material with uniform particle size distribution as claimed in claim 1, characterized in that: The soluble raw materials of M, Al, Eu and R are nitrates.

3. The method for preparing a long afterglow fluorescent material with uniform particle size distribution as claimed in claim 1, characterized in that: In step (1), the mass ratio of citric acid to ethylenediaminetetraacetic acid is 1:1 to 2.

5.

4. The method for preparing a long afterglow fluorescent material with uniform particle size distribution as claimed in claim 1, characterized in that: In step (2), the pH adjusting agent is one or more of ammonia water, urea, and sodium bicarbonate.

5. The method for preparing a long afterglow fluorescent material with uniform particle size distribution as claimed in claim 1, characterized in that: The polyethylene glycol includes one or more of polyethylene glycol 2000, polyethylene glycol 3000, polyethylene glycol 4000, polyethylene glycol 5000, and polyethylene glycol 6000.

6. The method for preparing a long afterglow fluorescent material with uniform particle size distribution as claimed in claim 1, characterized in that: In step (2), the mixing time is 0.5 to 3 hours at 50 to 80°C.

7. The method for preparing a long afterglow fluorescent material with uniform particle size distribution as claimed in claim 1, characterized in that: The drying in step (2) is carried out in a vacuum drying oven at a temperature of 80 to 130°C.

8. The method for preparing a long afterglow fluorescent material with uniform particle size distribution as claimed in claim 1, characterized in that: Step (3) The precursor powder is pre-calcined at 300°C to 400°C for 1 to 2 hours, and then calcined at 900°C to 1000°C in a reducing atmosphere for 1 to 3 hours.

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