Yellow fluorescent powder with high thermal quenching performance

Abstract

The invention discloses yellow fluorescent powder with high thermal quenching performance and belongs to the field of fluorescent materials. The fluorescent powder is prepared by adopting a Ce permeation process and can be represented by a chemical formula of 3Y2O3. 5Al2O3. 0.02 CeO2. Under the excitation of 450 nm blue light, the main peak of the emission spectrum of the fluorescent powder is 545 nm, the luminous intensity at 150 DEG C is 92.5% of that at room temperature and is increased by about 4% compared with that of the conventional Y3Al5O12: Ce < 3 + > fluorescent powder, and meanwhile, the use amount of rare earth Ce is reduced; and the external quantum efficiency is about 82.6%, so that the fluorescent powder can be applied to packaging of white light LEDs.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials, and more particularly to a yellow phosphor with high thermal quenching performance. Background Technology

[0002] Solid-state white lighting based on blue LED-excited phosphors has become the most popular lighting method. In this method, blue LEDs emit blue light under the influence of an electric current. The light emitted by the phosphor excited by the blue light recombines with the blue light that is not absorbed by the phosphor to produce white light.

[0003] Currently, the most widely used phosphor is Y3Al5O. 12 :Ce 3+ Yellow phosphor. The chemical composition of this phosphor was publicly reported as early as 1967 (Non-Patent Literature 1, A new phosphor for flying-spot cathod-raytubes for color television: yellow-emitting Y3Al5O). 12 :Ce 3+ (Appl. Phys. Lett., 1967, 11:2:53-55). This phosphor has advantages such as chemical stability, high quantum efficiency, and good thermal quenching performance. Under blue light excitation, it can emit yellow light, and the combination of yellow and blue light can produce (cool) white light. Therefore, most white solid-state lighting sources currently use this type of phosphor to varying degrees.

[0004] With technological advancements, the excitation density of blue LEDs is increasing, leading to a rise in the temperature of white LED lighting devices. At these higher temperatures, phosphors undergo thermal quenching. For example, under blue light excitation, Y3Al5O... 12 :Ce 3+ The luminescence intensity at 150℃ is only ~89% of that at room temperature. How to improve the luminescence intensity of Y3Al5O 12 :Ce 3+ The thermal quenching properties of Si have become a research hotspot in this field. Non-patent literature 2 (Anant A. Setlur, William J. Heward, Mark E. Hannah, Uwe Happek, Incorporation of Si) 4+ -N 3- into Ce 3+-Doped Garnets for Warm White LED Phosphors, Chemistry of Materials, 2008, 20, 19:6277-6283) reported on the synthesis of Y3Al5O 12 :Ce 3+ In phosphors, doping with Si3N4 material can enhance their high-temperature thermal quenching properties. (Non-Patent Literature 3 (V Bachmann, Cronda, A Meijerink, Temperature quenching of yellow Ce...)) 3+ (The study on luminescence in YAG:Ce, Chemistry of Materials, 2009, 21, 10: 2077-2084) suggests that reducing Ce doping... 3+ The concentration of Y3Al5O can enhance the effect. 12 :Ce 3+ It exhibits thermal quenching properties, but it significantly reduces the luminescence intensity of the material.

[0005] However, regardless of the technical approach used to enhance Y3Al5O 12 :Ce 3+ The thermal quenching properties in the synthesis of Y3Al5O 12 :Ce 3 + The common method involves uniformly mixing raw materials containing Y, Al, and Ce, and then synthesizing Y3Al5O under high temperature conditions. 12 :Ce 3+ All Ce 3+ Through high-temperature mass transfer, it is evenly distributed inside and on the outer surface of each phosphor particle.

[0006] However, it should be noted that in the actual luminescence process, when excitation light shines on the phosphor particles, only the luminescent centers contained in the surface layer of the phosphor particles actually contribute to luminescence. The numerous luminescent centers existing within the particles do not participate in luminescence; instead, due to energy transfer between them, they become luminescence quenching centers. In other words, the luminescent centers inside the phosphor particles are not necessary, and may even be harmful. However, current phosphor synthesis technologies cannot eliminate the presence of luminescent centers within the phosphor particles.

[0007] From the above, the following conclusions can be drawn: (1) Due to limitations in synthesis methods, existing phosphor particles contain a large number of ineffective or even harmful luminescent centers; (2) Low-concentration Ce doping can enhance Y3Al5O 12 :Ce 3+It has thermal quenching properties, but it will reduce the luminescence intensity of the phosphor. Summary of the Invention

[0008] The purpose of this invention is to solve the aforementioned problems in the prior art and provide a yellow phosphor with high thermal quenching performance, represented by the chemical formula 3Y₂O₃·5Al₂O₃·0.02CeO₂. This phosphor is synthesized using a Ce-infiltration process in Y₃Al₅O₂. 12 Ce is infiltrated onto the surface of the particles, achieving Ce deposition on Y3Al5O 12 The doping process ultimately yielded a yellow phosphor with high thermal quenching performance, represented by the chemical formula 3Y₂O₃·5Al₂O₃·0.02CeO₂. Under 450 nm blue light excitation, the main peak of the phosphor's emission spectrum was located at 545 nm, and its luminescence intensity at 150 °C was 92.5% of that at room temperature, which is higher than that of conventional Y₃Al₅O₂. 12 :Ce 3+ The phosphor efficiency was improved by ~4%, and the external quantum efficiency was ~82.6%. At the same time, this method also greatly reduced the amount of rare earth Ce used, realizing the efficient application of rare earth with reduced usage.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] Step (A). Mix 0.3 mol of Y2O3, 0.5 mol of Al2O3 and 0.01 mol of NaF evenly, and then carry out a high-temperature solid-state reaction in a muffle furnace under an air atmosphere for a certain period of time. After natural cooling, intermediate X is obtained.

[0011] In step (A), the objective is to synthesize a substance with the chemical formula Y3Al5O 12 granules.

[0012] Step (B). Take the intermediate X obtained in step (A) out of the muffle furnace, wash it several times with deionized water, and then dry it in an oven. After drying, pass the powder through a 300-mesh / 800-mesh standard sieve. Take the powder with a particle size range of 22 μm to 50 μm from the middle section of the 300-mesh / 800-mesh standard sieve and mix it evenly with 1 mol of CeO2 with a D95 particle size of 1.5 μm. Perform high-temperature heat treatment in a tube furnace under a reducing atmosphere for a certain period of time. After natural cooling, pass the powder through an 800-mesh standard sieve. Finally, what remains on the 800-mesh standard sieve is the yellow phosphor with high thermal quenching performance represented by the chemical formula 3Y2O3·5Al2O3·0.02CeO2.

[0013] In step (B), the purpose of washing with deionized water is to remove the NaF (flux) that was not completely volatilized in step (A). The so-called 300-mesh / 800-mesh standard sieve setup involves placing a 300-mesh standard sieve on top of an 800-mesh standard sieve, then placing the dried powder on top of the 300-mesh standard sieve to begin sieving. The final particle size range is 22 μm to 50 μm (Y3Al5O). 12 The particles will remain between a 300-mesh standard sieve and an 800-mesh standard sieve (on the 800-mesh standard sieve). Powder with a particle size range of 22 μm to 50 μm is mixed evenly with 1 mol of CeO2 (D95 particle size 1.5 μm) and subjected to high-temperature heat treatment to implement the Ce infiltration process. Ultimately, Ce permeates into Y3Al5O through high-temperature mass transfer. 12 The particles were then screened again to remove the unpenetrated CeO2, resulting in a yellow phosphor with high thermal quenching performance, represented by the chemical formula 3Y2O3·5Al2O3·0.02CeO2.

[0014] Preferably, in step (A), the temperature of the high-temperature solid-phase reaction is 1500-1600°C, and the reaction time is between 4 and 8 hours.

[0015] Preferably, in step (B), during high-temperature heat treatment, the reducing atmosphere is a mixture of 75% N2 and 25% H2 (volume ratio).

[0016] Preferably, in step (B), the high-temperature heat treatment temperature is 1600-1700℃ and the heat treatment time is between 12 and 24 hours.

[0017] Preferably, the purity of Y2O3, Al2O3, NaF, and CeO2 is not less than 99.5%.

[0018] The second objective of this invention is to provide a light-emitting device comprising an LED chip and a phosphor, wherein the LED chip can emit light in the wavelength range of 380 nm to 480 nm; and the phosphor includes at least the yellow phosphor with high thermal quenching performance synthesized in the above steps, which can be represented by the chemical formula 3Y2O3·5Al2O3·0.02CeO2.

[0019] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:

[0020] This invention provides a yellow phosphor with high thermal quenching properties. The phosphor is prepared using a Ce-doping process and can be represented by a chemical formula such as 3Y₂O₃·5Al₂O₃·0.02CeO₂. Under 450 nm blue light excitation, the phosphor exhibits an emission spectrum with a main peak at 545 nm, and its luminescence intensity at 150 °C is 92.5% of that at room temperature, which is higher than that of conventional Y₃Al₅O₂. 12 :Ce 3+ The phosphor efficiency is improved by ~4%, while saving on the amount of rare earth Ce used; the external quantum efficiency is ~82.6%, which makes the phosphor applicable to the packaging of white LEDs. Attached Figure Description

[0021] Figure 1 The X-ray diffraction pattern of the sample obtained in Comparative Example 1;

[0022] Figure 2 X-ray diffraction patterns for commercial products;

[0023] Figure 3 The emission spectrum of the sample obtained in Comparative Example 1 is shown.

[0024] Figure 4 The emission spectrum of commercial products;

[0025] Figure 5 The fluorescence lifetime curve of the sample obtained in Comparative Example 1 is shown.

[0026] Figure 6 Results of thermal quenching characteristics of commercial products and Comparative Example 1 and Example 1;

[0027] Figure 7 The X-ray diffraction pattern of the sample obtained in Example 1;

[0028] Figure 8 The emission spectrum of the sample obtained in Example 1;

[0029] Figure 9 The fluorescence lifetime curve of the sample obtained in Example 1;

[0030] Figure 10 The image shows the lighting effect of the device obtained in Example 2. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. To facilitate understanding of the present invention, embodiments are listed below. Those skilled in the art should understand that the embodiments are merely for the purpose of helping to understand the present invention and should not be considered as specific limitations on the present invention. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0032] This invention proposes a yellow phosphor with high thermal quenching performance and its preparation method, which can be represented by the chemical formula 3Y₂O₃·5Al₂O₃·0.02CeO₂. Under 450 nm blue light excitation, the phosphor exhibits a main peak in its emission spectrum at 545 nm, and its luminescence intensity at 150 °C is 92.5% of that at room temperature, which is higher than that of conventional Y₃Al₅O₂. 12 :Ce 3+ The phosphor efficiency was improved by approximately 4%; the external quantum efficiency was approximately 82.6%.

[0033] To obtain the yellow phosphor with the above-mentioned high thermal quenching performance, the following steps are taken:

[0034] Step (A). Mix 0.3 mol of Y2O3, 0.5 mol of Al2O3 and 0.01 mol of NaF evenly, and then carry out a high-temperature solid-state reaction in a muffle furnace under an air atmosphere for a certain period of time. After natural cooling, intermediate X is obtained.

[0035] Step (B). Take the intermediate X obtained in step (A) out of the muffle furnace, wash it three times with deionized water, and then dry it in an oven. After drying, pass the powder through a 300-mesh / 800-mesh standard sieve. Take the powder with a particle size range of 22 μm to 50 μm from the middle section of the 300-mesh / 800-mesh standard sieve and mix it evenly with 1 mol of CeO2 with a D95 particle size of 1.5 μm. Perform high-temperature heat treatment in a tube furnace under a reducing atmosphere for a certain period of time. After natural cooling, pass the powder through an 800-mesh standard sieve. Finally, what remains on the 800-mesh standard sieve is a yellow phosphor with high thermal quenching performance represented by the chemical formula 3Y2O3·5Al2O3·0.02CeO2.

[0036] In the above steps, the purity of Y2O3, Al2O3, NaF, and CeO2 is not less than 99.5%.

[0037] In step (A) above, during the high-temperature solid-phase reaction, the reaction temperature is 1500–1600℃ and the heat treatment time is between 4 and 8 hours.

[0038] In step (A) above, the reaction temperature is preferably 1550°C and the heat treatment time is preferably 4-6 hours during the high-temperature solid-phase reaction; in one embodiment provided by the present invention, the heat treatment time is preferably 5 hours.

[0039] In step (B) above, during high-temperature heat treatment, a reducing atmosphere is used, the heat treatment temperature is 1600–1700°C, and the heat treatment time is between 12 and 24 hours. The reducing atmosphere is preferably 75% N2–25% H2 (volume ratio). In some embodiments provided by this invention, the heat treatment temperature is preferably 1650°C.

[0040] In step (B) above, the heat treatment time is preferably 12 to 18 hours; in some embodiments provided by the present invention, the heat treatment time is preferably 16 hours.

[0041] After undergoing the reaction in steps (A) and (B), a yellow phosphor with high thermal quenching performance, represented by the chemical formula 3Y2O3·5Al2O3·0.02CeO2, can be obtained.

[0042] The light-emitting device comprises an LED chip and a phosphor, wherein the LED chip can emit light in the wavelength range of 380 nm to 480 nm, and the phosphor includes at least the yellow phosphor with high thermal quenching performance synthesized in the above steps, represented by the chemical formula 3Y2O3·5Al2O3·0.02CeO2.

[0043] All raw materials used in the following comparative examples and embodiments are commercially available.

[0044] Comparative Example 1

[0045] 0.298 mol Y₂O₃, 0.5 mol Al₂O₃, 0.01 mol NaF, and 0.002 mol CeO₂ were mixed thoroughly and then reacted in a tube furnace at 1650 °C for 16 h under a 75% N₂-25% H₂ (volume ratio) atmosphere. After cooling in the furnace, the mixture was removed, washed three times with deionized water, and dried to obtain the final product with the chemical formula Y. 2.98 Ce 0.02 Al5O 12 Yellow fluorescent powder.

[0046] The crystal structure of the obtained sample was measured using an X-ray diffractometer, confirming the acquisition of a pure phase. The diffraction pattern is shown below. Figure 1 For comparison, Y3Al5O was also measured. 12 :Ce 3+ The crystal structure of the commercial product was determined to be the same as that of Comparative Example 1, and its diffraction pattern is shown in [reference needed]. Figure 2 .

[0047] The emission spectra of the obtained samples were measured using a fluorescence spectrometer (450 nm excitation), and the emission spectra of commercial products were also measured, as shown below. Figure 3 and Figure 4 As shown, the two are similar in shape, but their strengths differ, with the one in Comparative Example 1 being slightly weaker.

[0048] The fluorescence lifetime of the obtained samples was measured using a fluorescence spectrometer (450 nm excitation), such as... Figure 5 As shown.

[0049] Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze Y3Al5O 12 :Ce 3+ The specific chemical composition of the commercial product was analyzed, and Y3Al5O was ultimately determined. 12 :Ce 3+ The general chemical composition of the commercial product is Y 2.94 Ce 0.06 Al5O 12 .

[0050] The external quantum efficiencies of the commercial product and the sample obtained in Comparative Example 1 were tested using a quantum efficiency meter, and the values ​​were 93.5% and 80.4%, respectively. Obviously, the lower doping concentration of Comparative Example 1 resulted in a lower quantum efficiency than that of the commercial product.

[0051] The thermal quenching characteristics of the commercial product and the sample obtained from Comparative Example 1 were measured using a phosphor thermal quenching test system. The results are as follows: Figure 6 As shown, it is clear that Comparative Example 1 with low Ce doping concentration has better thermal quenching characteristics than the commercial product (high doping concentration).

[0052] Example 1

[0053] Follow these steps to make it:

[0054] Step (A). Mix 0.3 mol Y2O3, 0.5 mol Al2O3 and 0.01 mol NaF evenly, and then carry out a high-temperature solid-state reaction in a muffle furnace under an air atmosphere for a certain period of time. The reaction temperature is 1550℃ and the reaction time is 5h. After natural cooling, intermediate X is obtained.

[0055] Step (B). Remove intermediate X obtained in step (A) from the muffle furnace, wash three times with deionized water, and then dry in an oven. The dried powder is then sieved through a 300-mesh / 800-mesh standard sieve. Powder with a particle size range of 22 μm to 50 μm (middle section of the 300-mesh / 800-mesh standard sieve) is mixed evenly with 1 mol of CeO2 (D95 particle size 1.5 μm). The mixture is then subjected to high-temperature heat treatment in a tube furnace under a reducing atmosphere of 75% N2-25% H2 (volume ratio) at 1650℃ for 16 hours. After natural cooling, the resulting powder is sieved through an 800-mesh standard sieve. Finally, a yellow powder remains on the 800-mesh standard sieve.

[0056] The specific chemical composition of the yellow phosphor obtained in Example 1 was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES), and its approximate chemical composition was finally determined to be 3Y2O3·5Al2O3·0.02CeO2.

[0057] The crystal structure of the obtained sample was measured using an X-ray diffractometer, confirming the acquisition of a pure phase. The diffraction pattern is shown below. Figure 7 .

[0058] The emission spectra of the material obtained in Example 1 were measured using a fluorescence spectrometer, and the results are as follows: Figure 8 As shown. Clearly, its emission spectrum is basically consistent with that of the commercial product and Comparative Example 1, only the intensity is higher than that of Comparative Example 1.

[0059] The fluorescence lifetime of the obtained samples was measured using a fluorescence spectrometer (450 nm excitation), such as... Figure 9 As shown, the results are not significantly different from those of Comparative Example 1.

[0060] The external quantum efficiency of the sample obtained in Comparative Example 1 was tested using a quantum efficiency meter, and the value was ~82.6%, which is lower than that of commercial products but slightly higher than that of Comparative Example 1.

[0061] The thermal quenching characteristics of the sample obtained in Example 1 were measured using a phosphor thermal quenching test system, and the results are as follows: Figure 6 As shown, it was finally determined that the main peak of the emission spectrum of this phosphor under 450 nm blue light excitation is located at 545 nm, and the luminescence intensity at 150 °C is 92.5% of that at room temperature, which is higher than that of conventional Y3Al5O. 12 :Ce 3+ The phosphor content was increased by approximately 4%.

[0062] Obviously, the present invention uses Ce infiltration technology to synthesize yellow phosphors with excellent luminescence properties and high thermal quenching characteristics.

[0063] Example 2

[0064] The yellow phosphor with high thermal quenching performance (chemical formula 3Y2O3·5Al2O3·0.02CeO2) obtained in Example 1 was encapsulated with a blue LED with an emission wavelength of 450 nm. The specific encapsulation process was as follows: the phosphor and epoxy resin were mixed at a mass ratio of 1:4.11, then coated onto the LED surface, and cured at 150°C for 30 minutes to obtain a white LED device. Figure 10 The effect of lighting up the device.

[0065] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0066] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0067] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A yellow phosphor with high thermal quenching performance, characterized in that: The phosphor is represented by the chemical formula 3Y₂O₃·5Al₂O₃·0.02CeO₂; under 450 nm blue light excitation, the main peak of the emission spectrum of the phosphor is located at 545 nm, the luminescence intensity at 150 °C is 92.5% of that at room temperature, and the external quantum efficiency is ~82.6%; the phosphor is prepared by the following method: Step (A). Y2O3, Al2O3 and NaF are mixed evenly, and then a high-temperature solid-state reaction is carried out in a muffle furnace under an air atmosphere. After natural cooling, intermediate X is obtained. Step (B). The intermediate X obtained in step (A) is taken out of the muffle furnace, washed several times with deionized water, and then dried in an oven. The dried powder is then sieved through a 300-mesh / 800-mesh standard sieve group. The powder with a particle size range in the middle section of the 300-mesh / 800-mesh standard sieve group is mixed evenly with CeO2 with a D95 particle size of 1.5 μm. The mixture is then subjected to high-temperature heat treatment in a tube furnace under a reducing atmosphere. After natural cooling, the resulting powder is sieved through an 800-mesh standard sieve. Finally, the powder remaining on the 800-mesh standard sieve is a yellow phosphor with high thermal quenching performance represented by the chemical formula 3Y2O3·5Al2O3·0.02CeO2. The molar ratio of Y2O3, Al2O3, NaF, and CeO2 in the raw materials is 0.3:0.5:0.01:

1.

2. The yellow phosphor with high thermal quenching performance as described in claim 1, characterized in that: In step (A), the temperature of the high-temperature solid-phase reaction is 1500-1600℃, and the reaction time is between 4 and 8 hours.

3. The yellow phosphor with high thermal quenching performance as described in claim 1, characterized in that: In step (B), during high-temperature heat treatment, the reducing atmosphere is a mixture of 75% N2 and 25% H2 by volume.

4. The yellow phosphor with high thermal quenching performance as described in claim 1, characterized in that: In step (B), the high-temperature heat treatment is performed at a temperature of 1600–1700°C for a duration of 12–24 hours.

5. The yellow phosphor with high thermal quenching performance as described in claim 1, characterized in that: The purity of Y2O3, Al2O3, NaF, and CeO2 is not less than 99.5%.

6. A light-emitting device, comprising an LED chip and phosphor, characterized in that: The phosphor includes a yellow phosphor with high thermal quenching performance as described in any one of claims 1 to 5.

7. The light-emitting device as described in claim 6, characterized in that: The LED chip emits wavelengths in the range of 380 nm to 480 nm.

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