A double-core-shell structure K2TiF6:Mn 4+ Preparation of @K2(Ti / Sn)F6@PPG red phosphor and its application in warm white LEDs

Abstract

This invention discloses a double-layer core-shell structure K2TiF6:Mn 4+ The preparation of @K2(Ti / Sn)F6@PPG red phosphor and its application in encapsulating warm white LEDs were disclosed. This phosphor effectively absorbs ultraviolet and blue light and emits bright red light with a wavelength between 590 and 650 nm, with the strongest emission peak at 631 nm. The obtained red light has a color purity of 92.45% and a relative color temperature of 3994 K. At a test temperature of 423 K, the relative fluorescence intensity of this phosphor is 56.71% of that at 298 K. After immersion in water for 60 minutes, its relative fluorescence intensity remains at 61.30% of its initial value. This invention requires low-level equipment and processes, has a simple preparation method, and the synthesized fluorescent material exhibits excellent photoluminescence properties and can significantly improve the optical performance of white LEDs.

Description

Technical Field

[0001] This invention relates to the field of warm white LEDs for indoor lighting, and describes the fabrication of a K2TiF6:Mn double-layer core-shell structure with excellent photoluminescence performance, water stability, and thermal stability by combining surface passivation and coating strategies. 4+ @K2(Ti / Sn)F6@PPG red phosphor. Using this phosphor to encapsulate white LEDs can significantly improve the optical performance of white LEDs, making them suitable for indoor lighting applications. Background Technology

[0002] White light-emitting diodes (WLEDs), as a new type of solid-state light source, offer advantages such as energy saving, environmental friendliness, long lifespan, and high reliability. Therefore, they have wide applications in healthcare and lighting. Furthermore, they are gradually replacing traditional light sources such as incandescent and fluorescent lamps. In commercial production, InGaN blue LED chips are commonly used as excitation sources to excite Y3Al5O4. 12 :Ce 3+ (YAG:Ce) 3+ The phosphor emits yellow light. Then, the residual blue light is combined with the emitted yellow light to achieve white light emission. However, the emission spectrum of this WLED lacks a red component, resulting in white light with a high color temperature (CCT>4000 K) and a low color rendering index (Ra<90). Therefore, this white light is not conducive to eye comfort and does not meet the application requirements of high-resolution scenarios, especially in indoor lighting and background displays, which is considered a significant application limitation. 4+ Activated fluoride phosphors, such as A2MF6:Mn 4+ (Where A represents K, Na, Li, Cs, Rb, and M represents Si, Ge, Ti, etc.) [MnF6] is a novel, environmentally friendly, low-cost material with excellent optical properties. It exhibits effective absorption of blue light and the ability to emit narrowband red light easily perceptible to the human eye. Therefore, these materials have been successfully commercialized for use in warm WLEDs excited by blue light. However, regrettably, this phosphor exhibits poor moisture resistance, mainly due to [MnF6]. 2- This is caused by the instability of the functional groups. This instability makes it very easy to hydrolyze in humid environments, generating MnO2. Besides reducing the number of fluorescent centers, this black MnO2 also hinders the absorption of blue light by the phosphor, leading to a significant decrease in luminous intensity. Simultaneously, the hydrolysis process also produces hydrofluoric acid (HF), which not only shortens the lifespan of LED devices but can also cause serious damage in severe cases. Therefore, Mn... 4+ The use of activated fluoride phosphors in high humidity environments is limited, which has become an urgent problem to be solved in order to promote the development of warm WLEDs.

[0003] In recent years, many researchers have proposed enhancing the Mn content by constructing core-shell structures. 4+ The idea is to activate the water stability of fluoride phosphors. Currently, researchers have prepared K2SiF6:Mn phosphors using surface passivation and coating strategies, respectively. 4+ @K2SiF6 and K2SiF6:Mn 4+ @OA Two new types of Mn 4+ Activate fluoride phosphors. This is achieved through Mn... 4+ Activating the surface of fluoride phosphors to form a protective layer can enhance the Mn content within the phosphor. 4+ To avoid water erosion, leading to Mn 4+ The presence of phosphors within the matrix material becomes more stable. However, these two preparation strategies have limitations in improving the water stability and luminescence intensity of fluoride phosphors, and cannot meet the practical application requirements of warm white LEDs for indoor lighting. Therefore, against this research background, we prepared a novel double-layer core-shell structure K2TiF6:Mn by combining surface passivation and coating strategies. 4+ @K2(Ti / Sn)F6@PPG red phosphor is used in the packaging of warm white LEDs for indoor lighting. Summary of the Invention

[0004] The purpose of this invention is to provide a double-layer core-shell structure K2TiF6:Mn with good water stability, prepared by combining surface passivation and coating strategies. 4+ A method for using @K2(Ti / Sn)F6@PPG red phosphor and its application in warm white LEDs. This red phosphor can produce bright red light emission under near-ultraviolet or blue light excitation, with an emission peak located near 631 nm, and can be used to improve the optical performance of white LEDs.

[0005] The technical solution of the present invention is as follows: A double-core-shell structure K2TiF6:Mn 4+ The preparation method of @K2(Ti / Sn)F6@PPG red phosphor includes the following steps: Step 1: In an ice-water bath, dissolve solid KMnO4 in HF solution and stir magnetically for 5-10 minutes. Then add solid KF and continue stirring for another 5-10 minutes. Next, add H2O2 solution dropwise to the solution; the solution color will gradually change from dark purple to yellow. Let the solution stand for 10-20 minutes to obtain a yellow solid. Wash the solid, dry the precipitate, and finally obtain K2MnF6 solid particles.

[0006] Furthermore, the ratio of KMnO4 solid, HF solution, KF solid and H2O2 solution is 0.9 g : 60 mL : 13.4 g : 0.8 mL.

[0007] Furthermore, the concentration of the HF solution is 40 wt%, and the mass fraction of the H2O2 solution is 30%.

[0008] Furthermore, the addition is done drop by drop.

[0009] Furthermore, the washing process involves first washing with water, followed by washing with ethanol.

[0010] Furthermore, the drying conditions are: drying at 60-80 ℃ for 2-3 hours.

[0011] Specifically, the yellow solid was washed once with deionized water and twice with ethanol. The obtained precipitate was dried at 60 °C for 2 h to finally obtain K2MnF6 solid powder.

[0012] Step 2: Weigh the raw materials. The molar ratio of HNO3 to NH4F is 1:1. KF and C 16 H 36 The molar ratio of O4Ti and K2MnF6 is 4:1:0.08, C 16 H 36 The molar ratio of O4Ti to SnCl2·2H2O is 1:0.1, and the molar ratio of SnCl2·2H2O to PPG (polypropylene glycol, molecular weight 2000) is 0.5:1.25-2.25, for example 0.5:1.25, 0.5:1.5, 1.75, 0.5:2.0, 0.5:2.25.

[0013] Step 3: At room temperature, dilute the HNO3 solution (concentration of 65-68%) weighed in Step 2 with deionized water to obtain a diluted HNO3 solution. Add NH4F to the deionized water and stir with a magnetic stirrer for 10-15 minutes at room temperature to obtain an NH4F solution. Add the NH4F solution to the diluted HNO3 solution and continue stirring for 10-15 minutes to obtain an HNO3 / NH4F mixed solution.

[0014] Furthermore, during the HNO3 dilution process, the volume ratio of HNO3 to deionized water was 5:10-15, the ratio of NH4F to deionized water in the NH4F solution was 1.1112 g:5 mL, and the molar ratio of HNO3 to NH4F in the HNO3 / NH4F mixed solution was 1:1.

[0015] Step 4: Weigh out C from Step 2 16 H 36O4Ti was added to the HNO3 / NH4F mixed solution prepared in step 3, and the mixture was stirred with a magnetic stirrer at room temperature for 10-15 minutes to form [TiF6]. 2- Solution; Furthermore, C 16 H 36 The mass ratio of O4Ti to NH4F is 1.7016 : 1.1112.

[0016] Step 5: Dissolve the KF weighed in Step 2 in deionized water to obtain a KF solution; add the KF solution to the solution prepared in Step 4, stir for 10-30 minutes, then add the K2MnF6 weighed in Step 2, and continue stirring for 30-40 minutes to obtain a solution containing Mn. 4+ A mixture doped with K2TiF6 phosphor.

[0017] Furthermore, the ratio of KF to deionized water in the KF solution is 1.1620 g: 10 mL.

[0018] Further, the KF weighed in step 2 is added to deionized water and stirred for 10-15 minutes to obtain a KF solution.

[0019] Step 6: Dissolve the SnCl2·2H2O weighed in Step 2 in deionized water to obtain a SnCl2·2H2O solution; add the SnCl2·2H2O solution to the mixture obtained in Step 5 and stir for 30-40 minutes. After standing, a pale yellow precipitate is obtained. Centrifuge, wash, and obtain a single-layer core-shell structure K2TiF6:Mn. 4+ @K2(Ti / Sn)F6 red phosphor.

[0020] Furthermore, the ratio of SnCl2·2H2O to deionized water in the SnCl2·2H2O solution is 0.1129 g : 10 mL.

[0021] Further, the SnCl2·2H2O weighed in step 2 is dissolved in deionized water and stirred with a magnetic stirrer at room temperature for 30-40 minutes to obtain a SnCl2·2H2O solution.

[0022] Furthermore, the settling time is 10-20 minutes.

[0023] Furthermore, the washing is performed with ethanol.

[0024] Step 7: Dissolve the PPG weighed in Step 2 in anhydrous ethanol to obtain a PPG solution; dissolve the single-layer core-shell structure K2TiF6:Mn obtained in Step 6... 4+@K2(Ti / Sn)F6 red phosphor was added to the PPG solution, and stirring was continued for 60-90 minutes. After standing, a pale yellow precipitate was obtained. The supernatant was discarded, and the precipitate was dried in a constant temperature oven to obtain K2TiF6:Mn. 4+ @K2(Ti / Sn)F6@PPG red phosphor.

[0025] Furthermore, the ratio of PPG to anhydrous ethanol in the PPG solution is 2.5-4.5 g : 20 mL, for example, 2.5 g : 20 mL, 3.0 g : 20 mL, 3.5 g : 20 mL, 4.0 g : 20 mL, and 4.5 g : 20 mL.

[0026] Further, the PPG weighed in step 2 is dissolved in anhydrous ethanol and stirred with a magnetic stirrer for 10-15 minutes at room temperature to obtain a PPG solution.

[0027] Furthermore, the settling time is 10-20 minutes.

[0028] Furthermore, the drying conditions are: drying at 60-80 ℃ for 2-3 h.

[0029] The double-layer core-shell structure K2TiF6:Mn prepared by the above method 4+ @K2(Ti / Sn)F6@PPG red phosphor can be excited by ultraviolet and blue light at 360 nm and 460 nm, respectively, and produces bright red light emission with wavelengths between 590 and 650 nm, and a strongest emission peak near 631 nm. The red light has a color purity of 92.45% and a relative color temperature of 3994 K. At a test temperature of 423 K, the relative fluorescence intensity of this phosphor is 56.71% of that at 298 K. After immersion in water for 60 minutes, its relative fluorescence intensity retains 61.30% of its initial value. Furthermore, K2TiF6:Mn... 4+ @K2(Ti / Sn)F6@PPG red phosphor can be used in warm white LEDs for indoor lighting.

[0030] The above-mentioned double core-shell structure K2TiF6:Mn 4+ @K2(Ti / Sn)F6@PPG red phosphor can be used to encapsulate warm white LEDs and can be applied in indoor lighting.

[0031] A packaging method for a warm white LED includes the following steps: Step 1: Add yellow fluorescent powder (YAG:Ce) 3+ ) and the above K2TiF6:Mn 4+@K2(Ti / Sn)F6@PPG red phosphor and epoxy resin were mixed in a mass ratio of yellow phosphor and red phosphor to epoxy resin of 1:3:25 to obtain the mixed epoxy resin. Step 2: Coat the surface of the blue LED chip (InGaN) with the mixed epoxy resin and dry at room temperature for 1 day.

[0032] The white LED has a relative color temperature of 3966 K and a color rendering index of 90.2 at a driving current of 20 mA. When the driving current is increased to 150 mA, the relative color temperature is 4420 K and the color rendering index is 90.6.

[0033] The red phosphor of this invention enables warm white light emission from LEDs, and is expected to become a novel red phosphor material for warm white LEDs. This red phosphor can be excited by blue light, making it suitable for current blue LED chips. Under blue light excitation, it exhibits red light emission properties in the 590-650 nm range, with the emission center near 631 nm. The red light color purity is 92.45%, and the relative color temperature is 3994 K. At a test temperature of 423 K, the relative fluorescence intensity of this phosphor is 56.71% of that at 298 K. After immersion in water for 60 minutes, the fluorescence intensity retains 61.30% of its initial value. Mn treated with passivation and coating strategies... 4+ Fluoride-doped phosphor materials are easy to prepare, with low requirements for equipment and processes, no need for high-temperature and high-pressure treatment, and a short synthesis cycle. Under a driving current of 20 mA, K₂TiF₆:Mn 4+ @K2(Ti / Sn)F6@PPG red phosphor can produce warm white LEDs with a relative color temperature of 3966 K and a color rendering index of 90.2. This invention requires low-level equipment and processes, has a simple preparation method, and the synthesized fluorescent material exhibits excellent photoluminescence properties and can significantly improve the optical performance of white LEDs. Attached Figure Description

[0034] Figure 1 The image shows the X-ray diffraction pattern of the phosphor prepared in Example 3. As can be seen from the image, all diffraction peaks of the phosphor are consistent with the trigonal K₂TiF₆ (PDF#73-2110) standard card. The absence of other impurity peaks indicates the successful preparation of the single-phase red phosphor K₂TiF₆:Mn. 4+ @K2(Ti / Sn)F6@PPG.

[0035] Figure 2 This is a scanning electron microscope image of the phosphor prepared in Example 3; it can be seen from the image that K2TiF6:Mn 4+The @K2(Ti / Sn)F6@PPG red phosphor exhibits a columnar structure with an average length and diameter of 16.68 ± 1.32 μm and 7.83 ± 0.16 μm, respectively.

[0036] Figure 3 The excitation and emission spectra of the phosphor prepared in Example 3 are shown. When 631 nm is used as the monitoring wavelength, the phosphor exhibits two broad and strong excitation peaks in the ultraviolet and blue light regions, with the strongest excitation peak located at 364 nm. Under 468 nm blue light excitation, K2TiF6:Mn 4+ The @K2(Ti / Sn)F6@PPG red phosphor exhibits narrow-band red light emission in the 580-680 nm range, with the strongest emission peak at 631 nm.

[0037] Figure 4 The image shows the CIE chromaticity diagram of the phosphor prepared in Example 3; under blue light excitation, the CIE chromaticity coordinates of the sample are located in the red light region at (0.6842, 0.3157).

[0038] Figure 5 Electroluminescence spectra of the blue LED chip, the cool white LED, and the warm white LED prepared in Example 3 are shown. It can be seen from the figures that the blue light emission peak in the 430 nm to 480 nm range in the electroluminescence spectrum originates from the blue LED chip, which is related to the prepared K2TiF6:Mn... 4+ The excitation spectrum of the red phosphor (@K2(Ti / Sn)F6@PPG) matches that of the yellow phosphor (YAG:Ce). 3+ The emission wavelength range of K2TiF6:Mn extends from 490 nm to 590 nm. 4+ The @K2(Ti / Sn)F6@PPG red phosphor provides a red emission peak in the wavelength range of 590 nm to 650 nm.

[0039] Figure 6 The image shows the CIE chromaticity diagram of the warm white LED encapsulated with the red phosphor prepared in Example 3. It can be seen from the image that the emitted color is located in the white light region, and the corresponding CIE color coordinates are (0.3440, 0.3359). Detailed Implementation

[0040] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0041] Example 1 In an ice-water bath, 0.9 g of KMnO4 solid was completely dissolved in 60 mL of HF (40%) solution. After magnetic stirring for 5 minutes, 13.4 g of KF was added and stirring continued for another 5 minutes. Subsequently, H2O2 (30%) solution was added dropwise to the above solution, and the color of the solution gradually changed from dark purple to yellow. The solution was then allowed to stand for 10 minutes to obtain a yellow solid, which was then washed once with deionized water and twice with ethanol. The obtained precipitate was dried at 60 °C for 2 h to finally obtain K2MnF6 solid powder.

[0042] At room temperature, dilute 5 mL of HNO3 solution (concentration 65-68%) to 20 mL, and dissolve 1.1112 g of NH4F in 5 mL of deionized water. After stirring for 10 minutes, add the solution to the HNO3 solution and continue stirring for another 10 minutes to obtain an HNO3 / NH4F mixed solution. Add 1.7016 g of C... 16 H 36 O4Ti was added to the mixed solution and stirred for 10 minutes. Simultaneously, 1.1620 g of KF was dissolved in 10 mL of deionized water, stirred for 10 minutes, and then added to the mixed solution, with stirring continued for another 10 minutes. 0.0988 g of K2MnF6 was added to the mixed solution and stirred for 30 minutes. 0.1129 g of SnCl2·2H2O was dissolved in 10 mL of deionized water, stirred for 30 minutes, and then added to the mixed solution. After standing for 10 minutes, a pale yellow precipitate was obtained. The precipitate was centrifuged at 8000 rpm for 3 minutes and washed three times with ethanol. Simultaneously, 2.5 g of PPG (molecular weight 2000) was dissolved in 20 mL of anhydrous ethanol and stirred for 10 minutes. The washed precipitate was transferred to the PPG solution and stirred for 60 minutes. After standing for 10 minutes, the supernatant was discarded, the precipitate was collected, and dried in a constant temperature oven at 60 °C for 2 h to obtain a pale yellow powder, which is K2TiF6:Mn. 4+ @K2(Ti / Sn)F6@PPG red phosphor.

[0043] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) The yellow phosphor is mixed with epoxy resin (HE-200) at a mass ratio of 1:25 to obtain the mixed epoxy resin. Then, the mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a cool white LED.

[0044] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) and the K2TiF6:Mn prepared above 4+A mixture of K2(Ti / Sn)F6@PPG red phosphor and yellow phosphor at a mass ratio of 1:3 yields a mixed phosphor. This mixed phosphor is then mixed with epoxy resin (HE-200) at a mass ratio of 4:25 to obtain a mixed epoxy resin. Finally, this mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a warm white LED.

[0045] Example 2 In an ice-water bath, 0.9 g of KMnO4 solid was completely dissolved in 60 mL of HF (40%) solution. After magnetic stirring for 5 minutes, 13.4 g of KF was added and stirring continued for another 5 minutes. Subsequently, H2O2 (30%) solution was added dropwise to the above solution, and the color of the solution gradually changed from dark purple to yellow. The solution was then allowed to stand for 10 minutes to obtain a yellow solid, which was then washed once with deionized water and twice with ethanol. The obtained precipitate was dried at 60 °C for 2 h to finally obtain K2MnF6 solid powder.

[0046] At room temperature, dilute 5 mL of HNO3 solution (concentration 65-68%) to 20 mL, and dissolve 1.1112 g of NH4F in 5 mL of deionized water. After stirring for 10 minutes, add the solution to the HNO3 solution and continue stirring for another 10 minutes to obtain an HNO3 / NH4F mixed solution. Add 1.7016 g of C... 16 H 36 O4Ti was added to the mixed solution and stirred for 10 minutes. Simultaneously, 1.1620 g of KF was dissolved in 10 mL of deionized water, stirred for 10 minutes, and then added to the mixed solution, with stirring continued for another 10 minutes. 0.0988 g of K2MnF6 was added to the mixed solution and stirred for 30 minutes. 0.1129 g of SnCl2·2H2O was dissolved in 10 mL of deionized water, stirred for 30 minutes, and then added to the mixed solution. After standing for 10 minutes, a pale yellow precipitate was obtained. The precipitate was centrifuged at 8000 rpm for 3 minutes and washed three times with ethanol. Simultaneously, 3.0 g of PPG (molecular weight 2000) was dissolved in 20 mL of anhydrous ethanol and stirred for 10 minutes. The washed precipitate was transferred to the PPG solution and stirred for 60 minutes. After standing for 10 minutes, the supernatant was discarded, the precipitate was collected, and dried in a constant temperature oven at 60 °C for 2 h to obtain a pale yellow powder, which is K2TiF6:Mn. 4+ @K2(Ti / Sn)F6@PPG red phosphor.

[0047] Yellow fluorescent powder YAG:Ce 3+(Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) The yellow phosphor is mixed with epoxy resin (HE-200) at a mass ratio of 1:25 to obtain the mixed epoxy resin. Then, the mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a cool white LED.

[0048] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) and the K2TiF6:Mn prepared above 4+ A mixture of K2(Ti / Sn)F6@PPG red phosphor and yellow phosphor at a mass ratio of 1:3 yields a mixed phosphor. This mixed phosphor is then mixed with epoxy resin (HE-200) at a mass ratio of 4:25 to obtain a mixed epoxy resin. Finally, this mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a warm white LED.

[0049] Example 3 In an ice-water bath, 0.9 g of KMnO4 solid was completely dissolved in 60 mL of HF (40%) solution. After magnetic stirring for 5 minutes, 13.4 g of KF was added and stirring continued for another 5 minutes. Subsequently, H2O2 (30%) solution was added dropwise to the above solution, and the color of the solution gradually changed from dark purple to yellow. The solution was then allowed to stand for 10 minutes to obtain a yellow solid, which was then washed once with deionized water and twice with ethanol. The obtained precipitate was dried at 60 °C for 2 h to finally obtain K2MnF6 solid powder.

[0050] At room temperature, dilute 5 mL of HNO3 solution (concentration 65-68%) to 20 mL, and dissolve 1.1112 g of NH4F in 5 mL of deionized water. After stirring for 10 minutes, add the solution to the HNO3 solution and continue stirring for another 10 minutes to obtain an HNO3 / NH4F mixed solution. Add 1.7016 g of C... 16 H 36O4Ti was added to the mixed solution and stirred for 10 minutes. Simultaneously, 1.1620 g of KF was dissolved in 10 mL of deionized water, stirred for 10 minutes, and then added to the mixed solution, with stirring continued for another 10 minutes. 0.0988 g of K2MnF6 was added to the mixed solution and stirred for 30 minutes. 0.1129 g of SnCl2·2H2O was dissolved in 10 mL of deionized water, stirred for 30 minutes, and then added to the mixed solution. After standing for 10 minutes, a pale yellow precipitate was obtained. The precipitate was centrifuged at 8000 rpm for 3 minutes and washed three times with ethanol. Simultaneously, 3.5 g of PPG (molecular weight 2000) was dissolved in 20 mL of anhydrous ethanol and stirred for 10 minutes. The washed precipitate was transferred to the PPG solution and stirred for 60 minutes. After standing for 10 minutes, the supernatant was discarded, the precipitate was collected, and dried in a constant temperature oven at 60 °C for 2 h to obtain a pale yellow powder, which is K2TiF6:Mn. 4+ @K2(Ti / Sn)F6@PPG red phosphor.

[0051] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) The yellow phosphor is mixed with epoxy resin (HE-200) at a mass ratio of 1:25 to obtain the mixed epoxy resin. Then, the mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a cool white LED.

[0052] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) and the K2TiF6:Mn prepared above 4+ A mixture of K2(Ti / Sn)F6@PPG red phosphor and yellow phosphor at a mass ratio of 1:3 yields a mixed phosphor. This mixed phosphor is then mixed with epoxy resin (HE-200) at a mass ratio of 4:25 to obtain a mixed epoxy resin. Finally, this mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a warm white LED.

[0053] Example 4 In an ice-water bath, 0.9 g of KMnO4 solid was completely dissolved in 60 mL of HF (40%) solution. After magnetic stirring for 5 minutes, 13.4 g of KF was added and stirring continued for another 5 minutes. Subsequently, H2O2 (30%) solution was added dropwise to the above solution, and the color of the solution gradually changed from dark purple to yellow. The solution was then allowed to stand for 10 minutes to obtain a yellow solid, which was then washed once with deionized water and twice with ethanol. The obtained precipitate was dried at 60 °C for 2 h to finally obtain K2MnF6 solid powder.

[0054] At room temperature, dilute 5 mL of HNO3 solution (concentration 65-68%) to 20 mL, and dissolve 1.1112 g of NH4F in 5 mL of deionized water. After stirring for 10 minutes, add the solution to the HNO3 solution and continue stirring for another 10 minutes to obtain an HNO3 / NH4F mixed solution. Add 1.7016 g of C... 16 H 36 O4Ti was added to the mixed solution and stirred for 10 minutes. Simultaneously, 1.1620 g of KF was dissolved in 10 mL of deionized water, stirred for 10 minutes, and then added to the mixed solution, with stirring continued for another 10 minutes. 0.0988 g of K2MnF6 was added to the mixed solution and stirred for 30 minutes. 0.1129 g of SnCl2·2H2O was dissolved in 10 mL of deionized water, stirred for 30 minutes, and then added to the mixed solution. After standing for 10 minutes, a pale yellow precipitate was obtained. The precipitate was centrifuged at 8000 rpm for 3 minutes and washed three times with ethanol. Simultaneously, 4.0 g of PPG (molecular weight 2000) was dissolved in 20 mL of anhydrous ethanol and stirred for 10 minutes. The washed precipitate was transferred to the PPG solution and stirred for 60 minutes. After standing for 10 minutes, the supernatant was discarded, the precipitate was collected, and dried in a constant temperature oven at 60 °C for 2 h to obtain a pale yellow powder, which is K2TiF6:Mn. 4+ @K2(Ti / Sn)F6@PPG red phosphor.

[0055] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) The yellow phosphor is mixed with epoxy resin (HE-200) at a mass ratio of 1:25 to obtain the mixed epoxy resin. Then, the mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a cool white LED.

[0056] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) and the K2TiF6:Mn prepared above 4+A mixture of K2(Ti / Sn)F6@PPG red phosphor and yellow phosphor at a mass ratio of 1:3 yields a mixed phosphor. This mixed phosphor is then mixed with epoxy resin (HE-200) at a mass ratio of 4:25 to obtain a mixed epoxy resin. Finally, this mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a warm white LED.

[0057] Example 5 In an ice-water bath, 0.9 g of KMnO4 solid was completely dissolved in 60 mL of HF (40%) solution. After magnetic stirring for 5 minutes, 13.4 g of KF was added and stirring continued for another 5 minutes. Subsequently, H2O2 (30%) solution was added dropwise to the above solution, and the color of the solution gradually changed from dark purple to yellow. The solution was then allowed to stand for 10 minutes to obtain a yellow solid, which was then washed once with deionized water and twice with ethanol. The obtained precipitate was dried at 60 °C for 2 h to finally obtain K2MnF6 solid powder.

[0058] At room temperature, dilute 5 mL of HNO3 solution (concentration 65-68%) to 20 mL, and dissolve 1.1112 g of NH4F in 5 mL of deionized water. After stirring for 10 minutes, add the solution to the HNO3 solution and continue stirring for another 10 minutes to obtain an HNO3 / NH4F mixed solution. Add 1.7016 g of C... 16 H 36 O4Ti was added to the mixed solution and stirred for 10 minutes. Simultaneously, 1.1620 g of KF was dissolved in 10 mL of deionized water, stirred for 10 minutes, and then added to the mixed solution, with stirring continued for another 10 minutes. 0.0988 g of K2MnF6 was added to the mixed solution and stirred for 30 minutes. 0.1129 g of SnCl2·2H2O was dissolved in 10 mL of deionized water, stirred for 30 minutes, and then added to the mixed solution. After standing for 10 minutes, a pale yellow precipitate was obtained. The precipitate was centrifuged at 8000 rpm for 3 minutes and washed three times with ethanol. Simultaneously, 4.5 g of PPG (molecular weight 2000) was dissolved in 20 mL of anhydrous ethanol and stirred for 10 minutes. The washed precipitate was transferred to the PPG solution and stirred for 60 minutes. After standing for 10 minutes, the supernatant was discarded, the precipitate was collected, and dried in a constant temperature oven at 60 °C for 2 h to obtain a pale yellow powder, which is K2TiF6:Mn. 4+ @K2(Ti / Sn)F6@PPG red phosphor.

[0059] Yellow fluorescent powder YAG:Ce 3+(Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) The yellow phosphor is mixed with epoxy resin (HE-200) at a mass ratio of 1:25 to obtain the mixed epoxy resin. Then, the mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a cool white LED.

[0060] Yellow fluorescent powder YAG:Ce 3+ (Manufacturer: Dongguan Kemai New Materials Co., Ltd., Model: KM-5366) and the K2TiF6:Mn prepared above 4+ A mixture of K2(Ti / Sn)F6@PPG red phosphor and yellow phosphor at a mass ratio of 1:3 yields a mixed phosphor. This mixed phosphor is then mixed with epoxy resin (HE-200) at a mass ratio of 4:25 to obtain a mixed epoxy resin. Finally, this mixed epoxy resin is coated onto the surface of a blue LED chip (InGaN) and dried at room temperature for one day to obtain a warm white LED.

Claims

1. A double-core-shell structure K2TiF6:Mn 4+ The method for preparing @K2(Ti / Sn)F6@PPG red phosphor is characterized by, Includes the following steps: Step 1: In an ice-water bath, dissolve solid KMnO4 in HF solution and stir magnetically for 5-10 minutes. Then add solid KF and continue stirring for another 5-10 minutes. Subsequently, add H2O2 solution dropwise to the above solution. The color of the solution will gradually change from dark purple to yellow. Then let the solution stand for 10-20 minutes to obtain a yellow solid. Wash the solid, dry the precipitate, and finally obtain K2MnF6 solid particles. Step 2: Place C 16 H 36 O4Ti is added to a mixed solution of HNO3 / NH4F and stirred with a magnetic stirrer at room temperature for 10-15 minutes to form [TiF6]. 2- Solution; Step 3: Dissolve KF in water to obtain a KF solution; then add the KF solution to the solution prepared in Step 2, stir for 10-30 minutes, then add the K2MnF6 solid particles prepared in Step 1, and continue stirring for 30-40 minutes to obtain a solution containing Mn. 4+ A mixture doped with K2TiF6 phosphor; Step 4: Dissolve SnCl2·2H2O in water to obtain a SnCl2·2H2O solution; add SnCl2·2H2O to the mixture obtained in Step 3, stir for 30-40 minutes, allow the solution to stand to obtain a pale yellow precipitate, centrifuge, wash, and dry to obtain a single-layer core-shell structure K2TiF6:Mn 4+ @K2(Ti / Sn)F6 red phosphor; Step 5: Dissolve PPG in anhydrous ethanol to obtain a PPG solution; add the monolayer core-shell structure K2TiF6:Mn prepared in step 4 to the PPG solution. 4+ @K2(Ti / Sn)F6 red phosphor, then stirred for 60-90 minutes, and after standing, a pale yellow precipitate was obtained. The supernatant was discarded, and the precipitate was dried to obtain a double core-shell structure K2TiF6:Mn. 4+ @K2(Ti / Sn)F6@PPG red phosphor.

2. The preparation method according to claim 1, characterized in that, In step 1, the ratio of KMnO4 solid, HF solution, KF solid, and H2O2 solution is 0.9 g : 60 mL : 13.4 g : 0.8 mL; the concentration of HF solution is 40 wt%, and the mass fraction of H2O2 solution is 30%. The addition is done drop by drop; the washing is done by first washing with water and then washing with ethanol; the drying conditions are: drying at 60-80 ℃ for 2-3 h.

3. The preparation method according to claim 1, characterized in that, In step 2, the C 16 H 36 The mass ratio of O4Ti to NH4F is 1.7016:1.1112; the molar ratio of HNO3 to NH4F in the HNO3 / NH4F mixed solution is 1:

1.

4. The preparation method according to claim 1, characterized in that, In step 2, at room temperature, the HNO3 solution is diluted with water to obtain a diluted HNO3 solution, and NH4F is added to the water. The mixture is stirred with a magnetic stirrer for 10-15 minutes at room temperature to obtain an NH4F solution. The NH4F solution is then added to the diluted HNO3 solution, and the mixture is stirred for another 10-15 minutes to obtain an HNO3 / NH4F mixed solution. The concentration of the HNO3 solution before dilution is 65-68%, the volume ratio of HNO3 to water during the dilution process is 5:10-15, and the ratio of NH4F to water in the NH4F solution is 1.1112 g:5 mL.

5. The preparation method according to claim 1, characterized in that, In step 3, KF, C 16 H 36 The molar ratio of O4Ti and K2MnF6 is 4:1:0.08; the ratio of KF to water in the KF solution is 1.1620 g:10 mL.

6. The preparation method according to claim 1, characterized in that, In step 4, C 16 H 36 The molar ratio of O4Ti to SnCl2·2H2O is 1:0.1; the ratio of SnCl2·2H2O to water in the SnCl2·2H2O solution is 0.1129 g:10 mL; The settling time is 10-20 minutes; the washing is done with ethanol.

7. The preparation method according to claim 1, characterized in that, In step 5, the molar ratio of SnCl2·2H2O to PPG is 0.5:1.25-2.25; the ratio of PPG to anhydrous ethanol in the PPG solution is 2.5-4.5 g:20 mL; and the molecular weight of PPG is 2000. The settling time is 10-20 minutes; the drying conditions are: drying at 60-80 ℃ for 2-3 hours.

8. The double-layered core-shell structure K2TiF6:Mn prepared by the method according to any one of claims 1-7 4+ @K2(Ti / Sn)F6@PPG red phosphor.

9. The double-layered core-shell structure K2TiF6:Mn as described in claim 8 4+ Application of @K2(Ti / Sn)F6@PPG red phosphor in warm white LEDs.

10. A packaging method for warm white LEDs, characterized in that, Includes the following steps: Step 1: Add yellow fluorescent powder YAG:Ce 3+ And the double-layered core-shell structure K2TiF6:Mn as described in claim 8 4+ @K2(Ti / Sn)F6@PPG red phosphor is mixed with epoxy resin to obtain a mixed epoxy resin; wherein the mass ratio of yellow phosphor, red phosphor and epoxy resin is 1:3:

25. Step 2: Coat the mixed epoxy resin onto the surface of the blue LED chip InGaN and dry it at room temperature for 1 day.

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