High-thermal-stability white fluorescent powder for health-oriented lighting, and preparation method and application thereof

Abstract

The application provides a high-thermal-stability white fluorescent powder for health-oriented lighting and a preparation method and application thereof. The chemical formula of the high-thermal-stability white fluorescent powder is LiHf2(PO4)3:xEu 2+ yMn 2+ , wherein 0

Description

Technical Field

[0001] This invention relates to the field of phosphor preparation technology, and in particular to a high thermal stability white phosphor for health lighting, its preparation method and application. Background Technology

[0002] White light-emitting diodes (W-LEDs) have attracted much attention as a next-generation lighting source due to their outstanding characteristics such as high luminous efficiency, long lifespan, environmental friendliness, and good stability, and have been widely used in the field of solid-state lighting. Currently, commercial white LEDs are mainly produced by coating a blue LED chip (440-470nm) with yellow CeO2. 3+ Yttrium aluminum garnet (YAG:Ce) 3+ Phosphors are used to produce this light, such as NP1046 phosphor commercially available from Nichia Chemical Industries, Ltd., or YAG-04 phosphor commercially available from Intermay. However, due to the lack of sufficient red spectral components, the cool white light produced by this method suffers from high color temperature (CCT) and low color rendering index (CRI). Therefore, researchers have developed a near-ultraviolet light-emitting diode chip coated with red, green, and blue phosphors, which can be used in white LEDs (Qiao, J., Ning, L., Molokeev, MS, Chuang, YC, Liu, Q., & Xia, Z.. (2018). Eu 2+ Site Preferences in the Mixed CationK2BaCa(PO4)2 and Thermally Stable Luminescence. However, for these conventional near-ultraviolet white LEDs, the white gap in the 480-520nm region of their emission spectrum significantly reduces the color rendering index (CRI) value, thus greatly limiting their application in high-quality lighting.

[0003] Therefore, to overcome this shortcoming, there is an urgent need to develop highly efficient, thermally stable white phosphors with high response to ultraviolet light, in order to compensate for the whiteness gap of near-ultraviolet warm white LEDs and significantly improve their color rendering index. However, to date, research on such highly thermally stable white phosphors remains scarce. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a high thermal stability white phosphor for healthy lighting, its preparation method and application. The prepared high thermal stability white phosphor has the advantage of stable physicochemical properties and high response to ultraviolet light with strong emission intensity. It can be widely matched with commercial near-ultraviolet LED chips, avoid the blue light hazards caused by using blue light chips, and meet the requirements of healthy lighting.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] One of the technical solutions of this invention is to provide a high thermal stability white phosphor for health lighting, wherein the chemical formula of the high thermal stability white phosphor is LiHf2(PO4)3:xEu 2+ yMn 2+ , of which 0 <x≤0.03,0<y≤0.008。

[0007] Furthermore, the excitation wavelength of the high thermal stability white phosphor is 270–450 nm, which is located in the ultraviolet and violet light regions.

[0008] Furthermore, the emission wavelength of the high thermal stability white phosphor is 400–700 nm.

[0009] Furthermore, the center wavelength of the emission band of the high thermal stability white phosphor is 491 nm.

[0010] The second technical solution of the present invention provides a method for preparing a high thermal stability white phosphor for healthy lighting as described in the first technical solution, comprising the following steps:

[0011] S1. Grind and mix lithium (Li) compound, hafnium (Hf) compound, NH4H2PO4, europium (Eu) compound, and manganese (Mn) compound evenly, calcine in air atmosphere, and obtain the precursor after cooling;

[0012] S2. Grind the precursor obtained in step S1 until uniform, sinter it in a reducing atmosphere, and obtain the high thermal stability white phosphor after cooling.

[0013] Further, the lithium (Li) compound mentioned in step S1 is a lithium (Li) oxide, a lithium (Li) halide, or a lithium (Li) carbonate.

[0014] Further, the hafnium (Hf) compound mentioned in step S1 is an oxide of hafnium (Hf) or a hafnium (Hf) halide.

[0015] Further, the europium (Eu)-containing compound mentioned in step S1 is an oxide of europium (Eu) or a halide of europium (Eu).

[0016] Further, the manganese (Mn) compound mentioned in step S1 is an oxide of manganese (Mn) or a halide of manganese (Mn).

[0017] Furthermore, the lithium (Li) compound is preferably Li2O, LiCl, or Li2CO3.

[0018] Furthermore, the hafnium (Hf)-containing compound is preferably HfO2 or HfCl4.

[0019] Furthermore, the europium (Eu)-containing compound is preferably Eu2O3 or HfCl3.

[0020] Furthermore, the manganese (Mn) compound is preferably MnO2 or HfCl2.

[0021] Further, the mass ratio of the lithium (Li) compound, hafnium (Hf) compound, NH4H2PO4, europium (Eu) compound, and manganese (Mn) compound in step S1 is (0.1-1.9):(8-13):(7-10):(0.02-0.3):(0.01-0.08).

[0022] Furthermore, the calcination temperature in the air atmosphere described in step S1 is 300–1000°C, and more preferably 800–850°C.

[0023] Furthermore, the grinding time in step S2 is 20 to 50 minutes.

[0024] Further, the reducing atmosphere in step S2 is a hydrogen-nitrogen mixture. The nitrogen volume content in the hydrogen-nitrogen mixture is 5% to 95%.

[0025] Furthermore, the sintering temperature in the reducing atmosphere described in step S2 is 1100–1400°C.

[0026] In some specific embodiments of this application, in step S1, a lithium (Li) compound, a hafnium (Hf) compound, NH4H2PO4, a manganese (Mn) compound, and a europium (Eu) compound are ground and mixed evenly, placed in an alumina crucible, and transferred to a muffle furnace. The mixture is calcined at 300–1000°C in air for 5–20 hours, then calcined again in air and cooled to room temperature to obtain a precursor. In step S2, the precursor is ground evenly, placed in a hydrogen-nitrogen mixed reducing atmosphere, and sintered at 1100–1400°C for 8–20 hours. After cooling to room temperature, the high thermal stability white phosphor is obtained.

[0027] The third technical solution of the present invention is to provide an application of a high thermal stability white phosphor for health lighting in the field of lighting devices, wherein the high thermal stability white phosphor is assembled with a chip to form an LED lighting device.

[0028] Furthermore, the highly thermally stable white phosphor is coated on the surface of the chip.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) Innovative doping system design: The luminescence properties of phosphors largely depend on the crystal structure of the host material; changes in structure can easily affect energy transfer processes, crystal field strength, and covalent properties. Eu... 2+ Because of its 4f n-1 5d 1 The unique outer electron configuration results in a broadband emission spectrum with high intensity and a short fluorescence lifetime. This broadband emission property perfectly meets the requirements of white LEDs, solar-like LEDs, full-spectrum LEDs, and high color rendering white LEDs for spectral continuity and the absence of spectral gaps. Therefore, Eu... 2+ Eu ions are important candidate dopant ions for rare-earth doped phosphors. This invention selects Eu... 2+ Mn serves as the luminescent center of the phosphor. 2+ As a regulatory ion, a white phosphor with strong emission intensity, ultraviolet and violet light response, and high thermal stability was synthesized.

[0031] (2) Broad emission spectrum: This invention provides a novel, unreported, high-response Eu light emission spectrum. 2+ Mn 2+ Co-doped white phosphor. The phosphor described in this invention can emit white light with a spectral range covering 400–700 nm and a center wavelength of 490–499 nm under ultraviolet or violet light excitation.

[0032] (3) Advantages of industrial preparation: The phosphor provided by this invention is Eu 2+ Mn 2+ Co-doped phosphate-based white phosphors possess the advantage of stable physicochemical properties. Furthermore, these highly thermally stable white phosphors can be prepared using conventional solid-state reaction methods, which are characterized by simple preparation processes, ease of industrial production, and good performance, making them promising candidate materials for a wide range of applications.

[0033] (4) Wide commercial compatibility: The high thermal stability white phosphor described in this invention can be well matched with existing commercial near-ultraviolet LED chips, and is suitable for applications such as ultraviolet chip white LEDs, ultraviolet chip solar-like LEDs, ultraviolet chip full-spectrum LEDs and ultraviolet chip high-quality white LEDs. Attached Figure Description

[0034] Figure 1 This is the photoexcitation-emission spectrum of Embodiment 1 of the present invention;

[0035] Figure 2 These are the photoluminescence spectra of Embodiments 1-3 of the present invention;

[0036] Figure 3 These are the thermal stability spectra of Examples 1 to 3 of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0038] Unless otherwise specified, the raw materials used in this invention are not particularly limited in their source; they can be purchased from the market or prepared according to conventional methods known to those skilled in the art. The raw materials used in this invention are Li2CO3 (Aladdin, 99%), HfO2 (Titan, 99.99%), NH4H2PO4 (Titan, 99%), Eu2O3 (Adamas, 99.99%), and MnO2 (Adamas, AR). The instruments include a muffle furnace (Hefei Kejing), a tube furnace (Hefei Kejing, GSL-1750X), and a fluorescence spectrometer (Hitachi, F7000).

[0039] The n-UV LED chips used in the embodiments refer to LED chips with a light emission center wavelength below 400nm. However, sometimes LED chips with a light emission wavelength greater than 380nm are called near-ultraviolet LED chips, while those with a wavelength shorter than 300nm are called deep ultraviolet LED chips.

[0040] Example 1

[0041] 1. Li₂CO₃, HfO₂, NH₄H₂PO₄, Eu₂O₃, and MnO₂ were selected as starting materials in a mass ratio of 0.8831:10.4277:8.5476:0.1308:0.0108, corresponding to x = 0.03 and y = 0.005 (i.e., LiHf₂(PO₄)₃:0.03Eu). 2+ 0.005Mn 2+ Weigh out five raw materials separately, and control the total mass of the raw material mixture to be 20g.

[0042] 2. Grind the above raw material mixture in an agate mortar for 50 minutes. After the material is mixed evenly, load the mixture into an alumina crucible. Then, calcine the alumina crucible containing the raw material at 800°C for 5 hours in an air atmosphere, and then let it cool naturally to room temperature. After that, grind the obtained mixture evenly again, and then calcine (sinter) it at 1100°C for 8 hours in a reducing atmosphere of hydrogen-nitrogen mixture (nitrogen volume content of 95% and hydrogen volume content of 5%). Then, cool it to room temperature to obtain the target product, a high thermal stability white phosphor.

[0043] 3. Use a fluorescence spectrometer (HITACHI F-7000) to test the spectral properties of the phosphor in this system, such as... Figure 1 and Figure 2 As shown in the figure. The results indicate that the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions (270–450 nm), with a peak value near 361 nm. The high spectral peak value indicates that it can be effectively excited by ultraviolet and violet chips and is well matched with n-UV LED chips. Under excitation by a 400 nm violet light source, the phosphor emits bright white light, and the emission spectrum consists of a broad emission band (400–700 nm), of which the emission band in the wavelength range of 400–580 nm belongs to the Eu region. 2+ The highest peak value at the launch center is located at 490nm, while the emission band in the wavelength range of 580-700nm belongs to Mn. 2+ Launch center. The prepared high thermal stability white phosphor possesses the advantage of high thermal stability (see Table 1), such as... Figure 3 As shown, its luminous intensity can still maintain 80% of the room temperature luminous intensity at 150 degrees Celsius, and it has a high response to ultraviolet light with strong emission intensity. It can be widely matched with commercial near-ultraviolet LED chips, avoiding the blue light hazards caused by the use of blue light chips, and meeting the requirements of healthy lighting.

[0044] Example 2

[0045] 1. Li₂CO₃, HfO₂, NH₄H₂PO₄, Eu₂O₃, and MnO₂ were selected as starting materials in a mass ratio of 0.8821:10.4271:8.5471:0.1308:0.0129, corresponding to x = 0.03 and y = 0.006 (i.e., LiHf₂(PO₄)₃:0.03Eu). 2+ 0.006Mn 2+ Weigh out five raw materials separately, and control the total mass of the raw material mixture to be 20g.

[0046] 2. Grind the above raw material mixture in an agate mortar for 50 minutes. After the material is mixed evenly, load the mixture into an alumina crucible. Then, calcine the alumina crucible containing the raw material at 300°C for 5 hours in an air atmosphere, and then let it cool naturally to room temperature. After that, grind the obtained mixture evenly again, and then calcine (sinter) it at 1100°C for 8 hours in a reducing atmosphere of hydrogen-nitrogen mixture (nitrogen volume content of 95% and hydrogen volume content of 5%). Then, cool it to room temperature to obtain the target product.

[0047] 3. Use a fluorescence spectrometer (HITACHI F-7000) to test the spectral properties of the phosphor in this system, such as... Figure 2As shown in the figure. The results indicate that the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions (270–450 nm), with a peak value near 360 nm. The high spectral peak value indicates that it can be effectively excited by ultraviolet and violet chips and is well matched with n-UV LED chips. Under excitation by a 400 nm violet light source, the phosphor emits bright white light, and the emission spectrum consists of a broad emission band (400–700 nm), of which the emission band in the wavelength range of 400–580 nm belongs to the Eu region. 2+ The highest peak value at the launch center is located at 491nm, while the emission band in the wavelength range of 580-700nm belongs to Mn. 2+ Launch center. The prepared high thermal stability white phosphor possesses the advantage of high thermal stability (see Table 1), such as... Figure 3 As shown, its luminous intensity can still maintain 79% of the room temperature luminous intensity at 150 degrees Celsius, and it has a high response to ultraviolet light with strong emission intensity. It can be widely matched with commercial near-ultraviolet LED chips, avoiding the blue light hazards caused by the use of blue light chips, and meeting the requirements of healthy lighting.

[0048] Example 3

[0049] 1. Li₂CO₃, HfO₂, NH₄H₂PO₄, Eu₂O₃, and MnO₂ were selected as starting materials in a mass ratio of 0.8802:10.4258:8.5461:0.1307:0.0172, corresponding to x = 0.03 and y = 0.008 (i.e., LiHf₂(PO₄)₃:0.03Eu). 2+ 0.008Mn 2+ Weigh out five raw materials separately, and control the total mass of the raw material mixture to be 20g.

[0050] 2. Grind the above raw material mixture in an agate mortar for 50 minutes. After the material is mixed evenly, load the mixture into an alumina crucible. Then, calcine the alumina crucible containing the raw material at 800°C for 5 hours in an air atmosphere, and then let it cool naturally to room temperature. After that, grind the obtained mixture evenly again, and then calcine (sinter) it at 1100°C for 8 hours in a reducing atmosphere of hydrogen-nitrogen mixture (nitrogen volume content of 95% and hydrogen volume content of 5%). Then, cool it to room temperature to obtain the target product.

[0051] 3. Use a fluorescence spectrometer (HITACHI F-7000) to test the spectral properties of the phosphor in this system, such as... Figure 2As shown in the figure. The results indicate that the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions (270–450 nm), with a peak value near 359 nm. The high spectral peak value indicates that it can be effectively excited by ultraviolet and violet chips and is well matched with n-UV LED chips. Under excitation by a 400 nm violet light source, the phosphor emits bright white light, and the emission spectrum consists of a broad emission band (400–700 nm), of which the emission band in the wavelength range of 400–580 nm belongs to the Eu region. 2+ The highest peak value at the launch center is located at 491nm, while the emission band in the wavelength range of 580-700nm belongs to Mn. 2+ Launch center. The prepared high thermal stability white phosphor possesses the advantage of high thermal stability (see Table 1), such as... Figure 3 As shown, its luminous intensity can still maintain 78% of the room temperature luminous intensity at 150 degrees Celsius, and it has a high response to ultraviolet light with strong emission intensity. It can be widely matched with commercial near-ultraviolet LED chips, avoiding the blue light hazards caused by the use of blue light chips, and meeting the requirements of healthy lighting.

[0052] Example 4

[0053] 1. Li₂CO₃, HfO₂, NH₄H₂PO₄, Eu₂O₃, and MnO₂ were selected as starting materials in a mass ratio of 0.8831:10.4277:8.5476:0.1308:0.0108, corresponding to x = 0.03y = 0.005 (i.e., LiHf₂(PO₄)₃:0.03Eu). 2+ 0.005Mn 2 + Weigh out five raw materials separately, and control the total mass of the raw material mixture to be 20g.

[0054] 2. Grind the above raw material mixture in an agate mortar for 50 minutes. After the material is mixed evenly, load the mixture into an alumina crucible. Then, calcine the alumina crucible containing the raw material at 850°C for 4 hours in an air atmosphere, and then let it cool naturally to room temperature. After that, grind the obtained mixture evenly again, and then calcine (sinter) it at 1300°C for 6 hours in a reducing atmosphere of hydrogen-nitrogen mixture (nitrogen volume content of 95% and hydrogen volume content of 5%). Then, cool it to room temperature to obtain the target product. The fluorescence spectrum properties of the phosphor in this system are similar to those in Example 1.

[0055] Example 5

[0056] 1. Li₂CO₃, HfO₂, NH₄H₂PO₄, Eu₂O₃, and MnO₂ were selected as starting materials in a mass ratio of 0.8821:10.4271:8.5471:0.1308:0.0129, corresponding to x = 0.03 and y = 0.006 (i.e., LiHf₂(PO₄)₃:0.03Eu). 2+ 0.006Mn 2+ Weigh out five raw materials separately, and control the total mass of the raw material mixture to be 20g.

[0057] 2. Grind the above raw material mixture in an agate mortar for 50 minutes. After the material is mixed evenly, load the mixture into an alumina crucible. Then, calcine the alumina crucible containing the raw material at 1000°C for 3 hours in an air atmosphere, and then let it cool naturally to room temperature. After that, grind the obtained mixture evenly again, and then calcine (sinter) it at 1100°C for 12 hours in a reducing atmosphere of hydrogen and nitrogen mixture (nitrogen volume content of 95% and hydrogen volume content of 5%). Then, cool it to room temperature to obtain the target product. The fluorescence spectrum properties of the phosphor in this system are similar to those in Example 2.

[0058] Example 6

[0059] 1. Li₂CO₃, HfO₂, NH₄H₂PO₄, Eu₂O₃, and MnO₂ were selected as starting materials in a mass ratio of 0.8802:10.4258:8.5461:0.1307:0.0172, corresponding to x = 0.03 and y = 0.008 (i.e., LiHf₂(PO₄)₃:0.03Eu). 2+ 0.008Mn 2+ Weigh out five raw materials separately, and control the total mass of the raw material mixture to be 20g.

[0060] 2. Grind the above raw material mixture in an agate mortar for 50 minutes. After the material is mixed evenly, load the mixture into an alumina crucible. Then, calcine the alumina crucible containing the raw material at 1000°C for 3 hours in an air atmosphere, and then let it cool naturally to room temperature. After that, grind the obtained mixture evenly again, and then calcine (sinter) it at 1200°C for 6 hours in a reducing atmosphere of hydrogen and nitrogen mixture (nitrogen volume content of 95% and hydrogen volume content of 5%). Then, cool it to room temperature to obtain the target product. The fluorescence spectrum properties of the phosphor in this system are similar to those in Example 3.

[0061] Comparative Example

[0062] Commercial YAG:Ce was selected 3+ A phosphor (Vespol, YAP-4454-L) was used as a control sample for thermal stability testing. The test results are as follows: Figure 3As shown.

[0063] It can be seen that commercial powder maintains about 80% of its room temperature emission intensity at 150℃, while the implementation cases of this patent can all be compared with the thermal stability of commercial powder. At the same time, the patented product has a high response to ultraviolet light with strong emission intensity, which can be widely matched with commercial near-ultraviolet LED chips, avoiding the blue light hazards caused by using blue light chips, meeting the high thermal stability requirements of LED operation and conforming to healthy lighting.

[0064] Table 1. Preparation process parameters of Examples 1-6

[0065]

[0066]

[0067] The color coordinates in the table can be directly obtained from CIE measurement software, which is common knowledge in this field and will not be elaborated further here. CIE stands for International Commission on Illumination. CIE measurement software is mainly used for color-related measurements, analyses, and calculations to comply with the standards and specifications set by CIE. Common CIE measurement software includes: ColorThink Pro, SpectraMagic NX, i1Profiler, etc., and their specific usage will not be described in detail here.

[0068] As shown in Table 1, Eu 2+ Mn 2+ The co-doped phosphate-based white emitting phosphor can emit white light with a spectral range of 400–700 nm and a central wavelength of 490–499 nm under ultraviolet or violet light excitation. It has a strong violet light response with high emission intensity. Under 400 nm violet light excitation, the phosphor emits bright white light and has high thermal stability.

[0069] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A high thermal stability white phosphor for healthy lighting, characterized in that, The chemical formula of this high thermal stability white phosphor is LiHf2(PO4)3:xEu 2+ yMn 2+ , of which 0 <x≤0.03,0<y≤0.008。 2. The high thermal stability white phosphor for health lighting according to claim 1, characterized in that, The emission wavelength of the high thermal stability white phosphor is 400–700 nm; The excitation wavelength of the high thermal stability white phosphor is 270~450nm.

3. A method for preparing a high thermal stability white phosphor for health lighting as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Grind and mix the Li-containing compound, Hf-containing compound, NH4H2PO4, Eu-containing compound, and Mn-containing compound evenly, calcine them in air atmosphere, and obtain the precursor after cooling; S2. Grind the precursor obtained in step S1 until uniform, sinter it in a reducing atmosphere, and obtain the high thermal stability white phosphor after cooling.

4. The method for preparing a high thermal stability white phosphor for health lighting according to claim 3, characterized in that, The Li-containing compound mentioned in step S1 is an oxide of Li, a halide of Li, or a carbonate of Li; The Hf-containing compound is an oxide of Hf or a halide of Hf; The Eu-containing compound is an oxide of Eu or a halide of Eu; The Mn-containing compound is an oxide of Mn or a halide of Mn.

5. The method for preparing a high thermal stability white phosphor for health lighting according to claim 4, characterized in that, The Li-containing compound is Li₂O, LiCl, or Li₂CO₃; The Hf-containing compound is HfO2 or HfCl4; The Eu-containing compound is Eu2O3; The Mn-containing compound is MnO2.

6. The method for preparing a high thermal stability white phosphor for healthy lighting according to claim 3, characterized in that, The mass ratio of the Li-containing compound, Hf-containing compound, NH4H2PO4, Eu-containing compound, and Mn-containing compound in step S1 is (0.1~1.9):(8~13):(7~10):(0.02~0.3):(0.01~0.08).

7. The method for preparing a high thermal stability white phosphor for healthy lighting according to claim 3, characterized in that, The calcination temperature in step S1, in an air atmosphere, is 300~1000℃.

8. The method for preparing a high thermal stability white phosphor for health lighting according to claim 3, characterized in that, The reducing atmosphere in step S2 is a hydrogen-nitrogen mixture, wherein the nitrogen volume content in the hydrogen-nitrogen mixture is 5% to 95%.

9. The method for preparing a high thermal stability white phosphor for health lighting according to claim 3, characterized in that, The sintering temperature in the reducing atmosphere described in step S2 is 1100~1400℃.

10. The application of a high thermal stability white phosphor for health lighting as described in claim 1 or 2 in the field of lighting devices, characterized in that, The high thermal stability white phosphor is assembled with the chip to create an LED lighting device; the high thermal stability white phosphor is coated on the surface of the chip.

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