Preparation method of red fluorescent powder
By treating potassium permanganate and potassium fluorosilicate in an autoclave, a red phosphor that meets the requirements of LED absorption peak was prepared, which solved the problem of insufficient light effect and resistance of red phosphors in the prior art, and achieved high brightness and The improvement of aging resistance has significantly improved the market promotion advantages of filament lamps.
Patent Information
- Application Number
- CN202411328855.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-24
- Publication Date
- 2024-12-27
AI Technical Summary
The prior art is difficult to provide a red phosphor that can meet the absorption peak requirements of LED light conversion materials, resulting in insufficient light efficiency, color rendering index and resistance of the filament lamp, and cannot be promoted quickly.
Using a preparation method of red phosphor, potassium permanganate is dissolved in hydrofluoric acid, potassium fluoride and hydrogen peroxide are added to reduce it to form potassium fluoromanganate, and then with potassium fluorosilicate and crystals in an autoclave The type control agent reacts, controls cooling and decompression, and obtains a red phosphor with high particle size, dispersion and crystallinity.
The prepared red phosphor has strong excitation in the range of 450nm to 500nm, and sharp-line emission in the range of 600nm to 640nm, which meets the absorption peak requirements of LED light conversion materials. It has low cost, simple process, high color rendering index and high brightness. It also has excellent aging resistance, which significantly enhances the market promotion advantages of filament lamps.
Smart Images
Figure CN119193148A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of LED luminescent materials, and in particular relates to a method for preparing red fluorescent powder. Background Art
[0002] At present, the lighting industry is constantly upgrading, LED lighting is the trend of lighting now and in the future, LED ball lamps have also replaced traditional lighting fixtures, filament lamps, as one of the LED lighting categories, have the brightness and clarity of tungsten filament lamps, and the energy-saving and longevity characteristics of LED lamps, and have gradually been recognized and loved by consumers. With the EU draft regulations proposing that the use of tungsten halogen lamps and compact fluorescent lamps as light sources will be banned in 2020, filament lamps will be the LED lighting product with the fastest growth rate.
[0003] Tungsten halogen lamps are banned from sale, and LED filament lamps have become the most ideal and perfect substitute. Filament lamps can emit light at 360 degrees, with a large angle and without the need for lenses, to achieve a three-dimensional light source with uniform light transmission and non-glare, creating the effect of tungsten filament lamps. This new light vision, original incandescent light environment, varied style designs, and strong decorative features are suitable for homes, bars, restaurants and other occasions.
[0004] Retro is an element and an attitude. For the popular retro style, the retro light bulbs make the lighting environment nostalgic and tasteful. The nostalgic shape and the color temperature that is almost close to natural light, the filament lamp always reminds people of the good times in the past.
[0005] Now, there is a need for a red phosphor that can meet the absorption peak requirements of LED-based light conversion materials, so that the produced filament lamps have the characteristics of high luminous efficiency, high color rendering index, good reliability, etc., so that filament lamps can be quickly promoted in the market. Summary of the invention
[0006] In view of the current status of the above-mentioned prior art, the present invention provides a method for preparing red phosphor, and the specific technical scheme is as follows:
[0007] A method for preparing a red phosphor, wherein the red phosphor has a general formula of M2SiF6:Mn 4+ , M is K or Na, and the preparation method of the red phosphor comprises the following steps:
[0008] S1. Potassium permanganate is dissolved in a hydrofluoric acid solution, potassium fluoride is added, and then hydrogen peroxide is added for reduction to form potassium fluoromanganate, which is then washed with pure water and ethanol and dried;
[0009] S2. The dried potassium fluoromanganate is crushed;
[0010] S3. Add hydrofluoric acid solution to the autoclave, then add potassium fluorosilicate or sodium fluorosilicate, stir thoroughly to dissolve;
[0011] S4. The potassium fluoromanganate crushed in step S2 is added to the solution obtained in step S3 as a seed crystal;
[0012] S5. Then add the crystal control agent, heat and pressurize the reaction, stir, and then cool and reduce pressure for recrystallization;
[0013] S6. Filter the recrystallization liquid from step S5 to obtain a pink product, wash it repeatedly with water and ethanol, dry it, and sieve it to obtain a red fluorescent powder.
[0014] The invention has the advantages of simple process, low cost, safety and non-toxicity, and prepares a manganese-doped fluorosilicate red phosphor with a particle size D50 ranging from 50 μm to 150 μm. The invention has stable chemical properties, is easy to store for a long time, has good fluorescence performance, and can provide a source of red light emission for LED lighting filament lamps.
[0015] Furthermore, in step S1, the concentration of the hydrogen peroxide solution is 20-40 wt %.
[0016] Furthermore, in step S2, the potassium fluoromanganate is crushed to a particle size of 1 to 3 microns.
[0017] Furthermore, in step S5, the crystal form controlling agent is one or both of potassium bifluoride and potassium fluoride.
[0018] Furthermore, in step S5, the reaction pressure is 0.5-2 MPa, the reaction temperature is 120-240° C., and the reaction time is 1-2 h.
[0019] Furthermore, in step S5, the time for cooling and reducing pressure is 10 to 24 hours.
[0020] Furthermore, in step S2, the equipment for crushing potassium fluoromanganate is a combination of one or more of a jet mill, a ball mill, a quick oscillator, and a roller mill.
[0021] Furthermore, in step S1 and step S3, the concentration of the hydrofluoric acid is 38-50 wt %.
[0022] Furthermore, in step S1, the mass ratio of potassium permanganate, hydrofluoric acid, potassium fluoride and hydrogen peroxide is 10:(300-1000):(2-10):(2-8).
[0023] Furthermore, the mass ratio of hydrofluoric acid to potassium fluorosilicate in step S3 is (5-20):1.
[0024] Furthermore, the mass ratio of the potassium fluoromanganate added in the step S4 to the potassium fluorosilicate is (0.5-2.0):10.
[0025] Furthermore, the mass ratio of the crystal form controlling agent in step S5 to the potassium fluorosilicate is (0.2-2.0):1.
[0026] The beneficial effects of the present invention are:
[0027] The present invention obtains red fluorescent powder with large particle size, good dispersibility and high crystallinity by adding appropriate crystal seeds, controlling the concentration of acid and controlling appropriate cooling and decompression speed in an autoclave. The red fluorescent powder has strong excitation in the range of 450nm to 500nm and strong sharp line emission in the range of 600nm to 640nm, which fully meets the absorption peak requirements of light conversion materials based on LEDs, and has low cost and simple process. The red fluorescent powder prepared by the present invention is matched with appropriate yellow-green powder and blue-green powder to prepare a filament lamp with significant advantages such as high light efficiency and high color rendering index compared with the use of traditional nitride red powder; the filament lamp has higher brightness and better aging resistance than the same type of fluorescent powder currently on the market, so the filament lamp prepared by the red fluorescent powder of the present invention has obvious advantages in market promotion. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 The fluorescence spectra of the red phosphor prepared in Examples 1-4 of the present invention;
[0029] Figure 2 The particle size test distribution diagram of the red phosphor prepared in Examples 1-4 of the present invention;
[0030] Figure 3 This is a SEM image of the red phosphor prepared in Examples 1-4 of the present invention magnified 200 times;
[0031] Figure 4 XRD patterns of the color phosphors prepared in Examples 1-4 of the present invention;
[0032] Figure 5 This is a SEM image of the red phosphor prepared in Comparative Example 1 of the present invention, magnified 200 times. DETAILED DESCRIPTION
[0033] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.
[0034] Example 1-1:
[0035] A method for preparing red phosphor, the specific steps are as follows:
[0036] 1) Mix 100g potassium permanganate and 5000g 48% hydrofluoric acid solution and stir for 30min, add 45g potassium fluoride, drop 60g 30% hydrogen peroxide to react and generate potassium fluoromanganate, wash with pure water and ethanol, and dry at 105 degrees;
[0037] 2) crushing the prepared dried potassium fluoromanganate with a jet mill to control the particle size D50 to 1 micron;
[0038] 3) Add 10kg of 50% hydrofluoric acid to a steel autoclave lined with polytetrafluoroethylene, then slowly add 1kg of potassium fluorosilicate and stir thoroughly for 30 minutes to completely dissolve the potassium fluorosilicate;
[0039] 4) taking 100 g of the potassium fluoromanganate crushed in step 2) above and adding it into the solution in step 3) as seed crystals;
[0040] 5) Add 0.1 kg potassium bifluoride and 1.2 kg potassium fluoride as crystal form control agents to the solution in step 4) respectively, and stir thoroughly for 30 minutes; then control the reaction temperature to 120°C, the reactor pressure to 0.5 MPa, and stir the reaction for 1 hour; after the reaction is completed, control the temperature to slowly decrease to 30 degrees at a uniform speed for 24 hours and reduce to normal pressure. During this process, potassium fluorosilicate in the solution will slowly grow on the basis of the seed crystals;
[0041] 6) The solution after the reaction in step 5) is centrifuged and the filtrate is removed to obtain a pink solid precipitate, which is repeatedly washed with water and ethanol, dried at 110 degrees, and then sieved to obtain a red phosphor product.
[0042] In Example 1-2 to Example 1-6:
[0043] In the step 4), the amounts of the crystal form control agent added are 0.3 kg potassium bifluoride and 1.0 kg potassium fluoride, 0.5 kg potassium bifluoride and 0.8 kg potassium fluoride, 0.7 kg potassium bifluoride and 0.6 kg potassium fluoride, 0.9 kg potassium bifluoride and 0.4 kg potassium fluoride, 1.1 kg potassium bifluoride and 0.2 kg potassium fluoride, respectively, and the mixture is stirred for 30 min; the other steps are the same as those in Example 1-1 and will not be repeated here.
[0044] Example 2-1 to Example 2-5:
[0045] A method for preparing red phosphor, the specific steps are as follows:
[0046] In the step 2), the particle sizes D50 of the potassium fluoromanganate crushed are 5, 3, 2, 0.8, and 0.5 μm, respectively; the other steps are the same as those in Examples 1-4 and will not be repeated here.
[0047] Example 3-1 to Example 3-5:
[0048] A method for preparing red phosphor, the specific steps are as follows:
[0049] In the step 5), after the reaction is completed, the temperature is slowly cooled to 30 degrees at a uniform speed and then reduced to normal pressure for 4, 8, 12, 16, and 20 hours respectively; the other steps are the same as those in Examples 1-4 and will not be repeated here.
[0050] Comparative Example 1
[0051] A method for preparing red phosphor, the specific steps are as follows:
[0052] 1) Mix 100g potassium permanganate and 5000g 48% hydrofluoric acid solution and stir for 30min, add 45g potassium fluoride, drop 60g 30% hydrogen peroxide to react and generate potassium fluoromanganate, wash with pure water and ethanol, and dry at 105 degrees;
[0053] 2) Add 10 kg of 50% hydrofluoric acid to a polytetrafluoroethylene-lined steel reactor, and then add 100 g of the dried potassium fluoromanganate and 1 kg of potassium fluorosilicate prepared in step 1) respectively, and stir for 30 min to completely dissolve them. This is solution A;
[0054] 3) Weigh 2 kg of potassium bifluoride and dissolve it in 10 kg of pure water to obtain solution B;
[0055] 4) Add the prepared solution A to solution B at an injection rate of 15 mL / s, stir for 4 h at 50 °C, and allow to stand for stratification;
[0056] 5) The solution after the reaction in step 5) is centrifuged and the filtrate is removed to obtain a pink solid precipitate, which is repeatedly washed with water and ethanol, dried at 110 degrees, and then sieved to obtain a red phosphor product.
[0057] test
[0058] 1. The red phosphors obtained in Examples 1-4 were subjected to fluorescence spectrum analysis, particle size test, SEM spectrum analysis, and X-ray diffraction analysis:
[0059] The fluorescence spectrum of the manganese-doped potassium fluorosilicate red phosphor prepared in Example 1-4 is as follows: Figure 1 As shown by Figure 1 It can be seen that the excitation wavelength is 455nm; the emission wavelength is 633nm; the fluorescence spectrum shows that Mn 4+ The doping of Mn 4+ of 4 A2→ 4 T1 and 4 A2→ 4T2 transition, emission peak at 630nm 2 E g → 4 A 2g Conversion, proved to be Mn 4+ Successfully doped.
[0060] Figure 2 The particle size distribution diagram of the manganese-doped fluorosilicate red phosphor prepared in Example 1-4 shows that the particle size is about 100 μm;
[0061] Figure 3 This is a SEM image of the manganese-doped fluorosilicate red phosphor prepared in Example 1-4. It can be seen that the powder is well crystallized.
[0062] Figure 4 The X-ray diffraction diagram of the manganese-doped fluorosilicate red phosphor prepared in Example 1-4 shows that the peak position of the KSF phosphor prepared in this example completely corresponds to that of potassium fluorosilicate, and manganese doping does not change the structure of potassium fluorosilicate.
[0063] Figure 5 This is the SEM image of the manganese-doped fluorosilicate red phosphor prepared in Comparative Example 1. It can be seen that the powder particles are small and have many aggregates.
[0064] The red phosphors prepared in Example 1 and Comparative Example 1 and the conventional nitride red phosphors were tested for luminescence performance and package aging performance. The specific test materials and equipment are as follows:
[0065] Phosphor: Yantai Bright Optoelectronic Materials Co., Ltd.
[0066] Chip: Epistar Corporation, Taiwan, China;
[0067] Glue: Shin-Etsu Chemical Co., Ltd., Japan;
[0068] Optical performance test: Hangzhou Yuanfang Optoelectronic Information Co., Ltd.
[0069] High and low temperature humidity and heat aging chamber: Shanghai Yishuo Experimental Instrument Factory;
[0070] Dispensing machine: MUSASHI;
[0071] Dispensing test method:
[0072] Tc:2700K If:21.9mA Ra>90
[0073] Aging conditions: Temperature: 85°C RH=85%.
[0074] The test results are shown in Table 1 and Table 2.
[0075] Table 1. Luminescence performance data of phosphor and nitride red powder prepared in Example and Comparative Example 1
[0076]
[0077]
[0078] Table 2. Package aging data of phosphor and nitride red powder prepared in Example and Comparative Example 1
[0079]
[0080]
[0081] As can be seen from Table 1, the addition amount of potassium bifluoride and potassium fluoride in different proportions, the particle size of potassium fluoromanganate, and the control of crystal precipitation time have a relatively obvious effect on the luminous flux and light efficiency of the phosphor. In the dual-crystal control agent, as the amount of potassium bifluoride added gradually increases, the brightness first rises and then decreases, and the brightness of Examples 1-4 is the highest; the change in the proportion of different crystal control agents may change the growth and precipitation environment of potassium fluorosilicate, and the appropriate balance point of the ratio of potassium bifluoride to potassium fluoride is found in Examples 1-4. Different potassium fluoromanganate seed particle sizes have an impact on the brightness of the phosphor. Too large or too small a particle size is not good, and Examples 1-4 have the highest brightness; too large a particle size will result in too high a manganese ion concentration in a single phosphor particle, which is prone to quenching of the exciter concentration and affects the brightness. If the particle size is too small, it may be severely broken, which may bring in too many impurities and damage the original crystal form, which is not conducive to the subsequent growth of potassium fluorosilicate crystals. As the crystallization time increases, the brightness gradually increases. The brightness of Example 1-4 is the highest, but it grows slowly after 16 hours. Analysis shows that the crystallization speed is slow and the crystal growth is better, but when the speed slows down to a certain extent, the effect of the crystallization time on the brightness becomes smaller.
[0082] From the test data of Examples 1-4 and Comparative Example 1 after optimizing the conditions, it can be seen that the red phosphor prepared by the present invention is superior to the potassium fluorosilicate phosphor prepared by normal pressure reaction in terms of luminous efficiency and package aging. At the same time, the efficiency of the red phosphor used in the present invention is more than 10% higher than that of the traditional nitride phosphor, and the overall performance is better. It can be seen that adding seed crystals to the autoclave and selecting appropriate conditions for pressurized reaction can effectively improve the luminous performance of the phosphor of the present invention. As can be seen from Table 2, after the 1000h aging test, the phosphors prepared by Examples 1-4 after optimizing the conditions have lower light decay and color drift than the potassium fluorosilicate phosphor prepared by normal pressure, and have better aging resistance.
[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for preparing a red phosphor, characterized in that: The red phosphor has the general formula of M2SiF6:Mn 4+ , M is K or Na, and the preparation method of the red phosphor comprises the following steps: S1. Potassium permanganate is dissolved in a hydrofluoric acid solution, potassium fluoride is added, and then hydrogen peroxide is added for reduction to form potassium fluoromanganate, which is then washed with pure water and ethanol and dried; S2. The dried potassium fluoromanganate is crushed; S3. Add hydrofluoric acid solution to the autoclave, then add potassium fluorosilicate or sodium fluorosilicate, stir thoroughly to dissolve; S4. The potassium fluoromanganate crushed in step S2 is added to the solution obtained in step S3 as a seed crystal; S5. Then add the crystal control agent, heat and pressurize the reaction, stir, and then cool and reduce pressure for recrystallization; S6. Filter the recrystallization liquid from step S5 to obtain a pink product, wash it repeatedly with water and ethanol, dry it, and sieve it to obtain a red fluorescent powder.
2. The method for preparing red phosphor according to claim 1, characterized in that: In the step S1, the concentration of the hydrogen peroxide solution is 20-40 wt %.
3. The method for preparing red phosphor according to claim 1, characterized in that: In the step S2, the potassium fluoromanganate is crushed to a particle size of 1 to 3 microns.
4. The method for preparing red phosphor according to claim 1, characterized in that: In the step S5, the crystal form controlling agent is one or both of potassium bifluoride and potassium fluoride.
5. The method for preparing red phosphor according to claim 1, characterized in that: In the step S5, the reaction pressure is 0.5-2 MPa, the reaction temperature is 120-240° C., and the reaction time is 1-2 h; the time for cooling and reducing pressure is 10-24 h.
6. The method for preparing red phosphor according to claim 1, characterized in that: In the step S1 and the step S3, the concentration of the hydrofluoric acid is 38-50 wt %.
7. The method for preparing red phosphor according to claim 1, characterized in that: In step S1, the mass ratio of potassium permanganate, hydrofluoric acid, potassium fluoride and hydrogen peroxide is 10:(300-1000):(2-10):(2-8).
8. The method for preparing red phosphor according to claim 1, characterized in that: The mass ratio of hydrofluoric acid to potassium fluorosilicate in step S3 is (5-20):
1.
9. The method for preparing red phosphor according to claim 1, characterized in that: The mass ratio of the potassium fluoromanganate added in the step S4 to the potassium fluorosilicate is (0.5-2.0):
10.
10. The method for preparing red phosphor according to claim 1, characterized in that: The mass ratio of the crystal form controlling agent in step S5 to the potassium fluorosilicate is (0.2-2.0):1.