Gallium aluminate green fluorescent material, preparation method and white light LED light-emitting device

Abstract

The invention discloses a gallium aluminate green fluorescent material, a preparation method and a white light LED light-emitting device. The general chemical formula of the luminescent material is Y2-xLuAl4GaO12: xCe < 3 + > (x is greater than or equal to 0.003 and less than or equal to 0.08), the luminescent material has strong absorption in an excitation region of 300-500nm, can be effectively excited by blue light and emits green light with the dominant wavelength of about 530nm, and the green light fluorescent material has the advantages of high luminescent intensity, good thermal stability and good chemical stability, and can be widely applied to the field of luminescent materials. And the warm white LED luminescent device manufactured by combining the red fluorescent material with the existing commercial red fluorescent material has the advantages of high brightness, good color rendering performance, high energy conversion rate, good color stability and wide application potential. The preparation method of the green fluorescent material is simple, easy to operate, low in raw material cost, low in equipment cost, free of pollution and suitable for industrial production, and products are easy to collect.

Description

Technical Field

[0001] The invention belongs to the technical field of luminescent materials, and in particular relates to a gallium aluminate green light fluorescent material and a preparation method thereof, and a white light LED luminescent device. Background Art

[0002] At present, the dual pressures of global ecological environment and energy supply have prompted the concepts of low carbon, environmental protection and sustainable development to become the core of development strategies of various countries. In this context, LED semiconductor lighting technology, with its outstanding energy-saving and environmental protection advantages, accurately meets the urgent needs of the times for green transformation and has become a key force in promoting the green revolution in the global lighting industry. The Chinese government attaches great importance to the development of the white light LED lighting industry and is accelerating the vigorous rise of this green lighting industry through policy support and technological innovation.

[0003] The traditional construction of white light LEDs mainly relies on the combination of blue light LED chips and yellow light YAG:Ce fluorescent materials, but this solution has significant defects: the lack of red light components leads to a low color rendering index (<80) and a high color temperature (>4500K), which affects the lighting quality. More seriously, the thermal stability of fluorescent materials makes it difficult to ensure color stability and easily produces color difference, further reducing the lighting quality. Therefore, improving the color rendering index of white light LEDs to >80, optimizing lumen efficiency, and adjusting the color temperature within a more comfortable range of 2700-4500K have become important goals for achieving high-quality healthy lighting.

[0004] At present, commercial white light LEDs can also be prepared by blue light LED chips and red and green fluorescent materials, or by near-ultraviolet LED chips and red, green and blue primary color fluorescent materials. In the field of lighting, the red, green and blue primary color fluorescent materials required for the synthesis of white light LEDs are mostly doped with rare earth or transition metals, such as rare earth Ce 3+ 、Eu 2+ 、Eu 3+ 、Bi 3+ Doping and transition metal Cr 3 + 、Ni 2+ , Mn 2+ , Mn 4+ Doping. Rare earth doped fluorescent materials, especially Ce3+ doped fluorescent materials, show excellent luminescence performance. Their unique wide absorption range enables these materials to efficiently match blue light chips, and then emit light covering the ultraviolet to red light region, opening up a broad application space and prospects for white light LED lighting technology. 3+ Doped fluorescent materials are currently highly anticipated candidates.

[0005] At present, green fluorescent materials still face two major bottlenecks in practical applications: low luminous efficiency and poor thermal stability. The research and development of green fluorescent materials that can efficiently match blue LEDs and have high quantum efficiency and excellent thermal stability has become a key issue in the field of white LED luminescent materials. Breakthroughs in this field are not only crucial to improving the overall performance of LED devices, but also the only way to promote the popularization of LED lighting, promote energy conservation and emission reduction, and protect the environment and ecology. Therefore, in-depth exploration and optimization of green fluorescent materials with high efficiency and thermal stability are of far-reaching and significant significance. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a high-efficiency green light fluorescent material that can match the blue light chip, and to provide a preparation method thereof and a corresponding white light LED light-emitting device. The green light fluorescent material in the present invention has the advantages of stable chemical properties, high quantum efficiency and excellent thermal stability.

[0007] Specifically:

[0008] The gallium aluminate green light fluorescent material provided by the present invention is a new type of green light fluorescent material, which uses gallium aluminate as a matrix and trivalent Ce as an activator. Its chemical formula is Y 2-x LuAl4GaO 12 :xCe 3+ ,0.003≤x≤0.08; preferably, the value of x is 0.04.

[0009] The present invention also provides a green fluorescent material Y 2-x LuAl4GaO 12 :xCe 3+ The preparation method adopts a high temperature solid phase method, comprising the following steps:

[0010] 1) Weighing of raw materials: according to the general formula Y 2-x LuAl4GaO 12 :xCe 3+ The raw materials of yttrium source, lutetium source, gallium source, aluminum source and cerium source are accurately weighed in a stoichiometric ratio; all the weighed raw materials are mixed in an agate mortar; wherein the yttrium source can be yttrium oxide, yttrium carbonate or yttrium nitrate; the lutetium source can be lutetium oxide, lutetium carbonate or lutetium nitrate; the gallium source can be gallium oxide; the aluminum source can be aluminum oxide, aluminum carbonate or aluminum nitrate; the cerium source can be cerium nitrate, cerium oxide or cerium chloride;

[0011] 2) grinding and mixing: adding an appropriate amount of ethanol to the powdered raw materials weighed in step 1) and grinding to uniformly mix the raw materials to obtain a raw material mixture; wherein the amount of ethanol added may be 10-20 mL, and the grinding time may be 30-60 minutes;

[0012] 3) Calcination: Transfer the raw material mixture obtained in step 2) into a corundum crucible, place the crucible in a tube furnace or a box furnace, and calcine for 4-10 hours in an air atmosphere at a temperature range of 1500-1700° C. and a heating rate of 1-10° C. / min;

[0013] 4) Collecting samples: The sintered body obtained in step 3) is naturally cooled to room temperature, and then placed in an agate mortar and ground to reduce the particle size of the sample. Usually, grinding for 5-30 minutes can obtain a green fluorescent material with regular particle morphology, small particle size and uniform particle size distribution.

[0014] The present invention also provides a white light LED lighting device, comprising an InGaN semiconductor chip and a green light fluorescent material and a red light fluorescent material covering the chip; wherein the green light fluorescent material adopts the gallium aluminate green light fluorescent material that can be excited by blue light as described above in the present invention, and the red light fluorescent material can be any commercial red light fluorescent material that can be excited by blue light.

[0015] Preferably, the InGaN semiconductor chip is a blue LED chip, and its peak emission wavelength is 420-455nm; the red fluorescent material can be Sr2Si5N8:Eu 2+ .

[0016] The two fluorescent materials are uniformly dispersed in UV quick-drying resin glue, covered on the InGaN semiconductor chip by coating or dispensing, and cured to obtain a white light LED light-emitting device.

[0017] The present invention has the following beneficial effects:

[0018] The gallium aluminate green light fluorescent material of the present invention has strong absorption in the 300-500nm excitation region, can be effectively excited by blue light, and emits green light with a main wavelength of about 530nm. The green light fluorescent material has high luminous intensity, good thermal stability and chemical stability, and the internal quantum efficiency under 440nm wavelength excitation can reach 99.68%, and the emission intensity at 150°C is still maintained at more than 95.77% of the emission intensity at room temperature. The green light fluorescent material for white light LED of the present invention is combined with the red light fluorescent material in the prior art, and high-quality white light can be obtained under the excitation of the InGaN blue light LED chip, which can meet the needs of the general lighting field for different types of light sources. At the same time, the white light LED device has the advantages of higher color rendering index and lower color temperature. The preparation method of the present invention is simple, easy to operate, low in raw material cost, low in equipment cost and pollution-free, and the product is easy to collect, which is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is an X-ray diffraction (XRD) diagram of the green fluorescent material of the present invention;

[0020] Figure 2 is the excitation and emission spectra of the green fluorescent material of the present invention;

[0021] Figure 3 The green light fluorescent material of the present invention is in different Ce 3+ Emission spectra at different ion doping concentrations;

[0022] Figure 4 This is a quantum efficiency spectrum diagram of the green fluorescent material of the present invention;

[0023] Figure 5 This is a graph showing the variation of the emission intensity of the gallium aluminate fluorescent material excited by blue light with temperature, with the excitation wavelength being 440nm;

[0024] Figure 6 It is a schematic diagram of the white light LED lighting device of the present invention and its spectrum diagram. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below in conjunction with examples, which are merely illustrative and are not intended to limit the scope of application of the present invention. The present invention is not limited to the following embodiments or examples, and any modifications and variations that do not violate the spirit of the present invention should be included within the scope of the present invention.

[0026] Example 1 Preparation of green fluorescent material

[0027] The chemical composition formula of the green fluorescent material in this embodiment is Y 2-x LuAl4GaO 12 :xCe 3+ (0.003≤x≤0.08), x takes values ​​of 0.003, 0.005, 0.01, 0.02, 0.04, 0.06 and 0.08. According to the stoichiometric ratio of each element in the chemical formula, accurately weigh the powder raw materials Y2O3, Lu2O3, Ga2O3, Al2O3 and Ce2O3, put them in an agate mortar, add appropriate amount of ethanol and grind until the raw materials are fully mixed and evenly transferred to an alumina crucible, placed in a tube furnace, sintered at 1600℃ for 6 hours in an air atmosphere, taken out after natural cooling, and ground again to obtain the fluorescent material. Figure 1 The XRD diagram shown is the result when x is 0.04. The results show that Y 1.96 LuAl4GaO 12 :0.04Ce 3+ It can match the standard card well, and no obvious impurity phase appears, indicating that the phase is pure. The XRD patterns of the other values ​​of 0.003, 0.005, 0.01, 0.02, 0.06 and 0.08 are the same as when x is 0.04, and are not repeated, indicating that the values ​​of x in the present invention can obtain a single-phase green fluorescent material.

[0028] Example 2 Excitation and emission wavelength detection

[0029] The excitation and emission spectra of the green fluorescent material prepared in Example 1 were tested using a fluorescence spectrometer. Figure 2 The spectrum of the fluorescent material when x is 0.04 shows that the fluorescent material has a wide excitation and emission range, the excitation peak range is 300-500nm, and there is a wide strong excitation in the blue light band, indicating that it can match the InGaN blue light chip well; its optimal emission peak is located at ~530nm, and the emission peak range is 460-750nm. The excitation peak range, emission peak range and optimal emission peak of the fluorescent material with other values ​​of x are the same as those when x is 0.04, and will not be repeated. It shows that the fluorescent material of the present invention is a green light fluorescent material.

[0030] Example 3 Comparison of emission wavelengths of different fluorescent materials

[0031] The emission spectra of the seven green fluorescent materials prepared in Example 1 were measured using a fluorescence spectrometer. Figure 3 As shown, with Ce 3+ As the Ce ion doping content increases, the shape and position of the emission peak in the emission spectrum are similar, but the emission peak intensity at ~530nm increases with the Ce 3+ The doping concentration of Ce ions gradually increases. 3+ When the ion doping concentration reaches 0.04, the luminescence intensity begins to decrease.

[0032] Example 4 Quantum efficiency detection of fluorescent materials

[0033] Generally, fluorescence quantum efficiency refers to the ratio of the number of photons emitted by fluorescence, n2, to the number of photons absorbed by the excited substance from the pump source, n1. The calculation principle of quantum efficiency is: Among them, ∫L S is the integral of the emission spectrum of the sample measured in the integrating sphere, ∫E R is the integral of the excitation spectrum obtained under the integrating sphere when the blank sample is tested, ∫E s The integral of the excitation spectrum of the sample tested in the integrating sphere. Therefore, we monitor the optimal excitation wavelength of the green fluorescent material prepared when x is 0.04 according to the implementation case 1, and can obtain the excitation spectrum of the blank sample, the excitation spectrum of the sample and the emission spectrum when no sample is placed and when the sample is placed, respectively, as shown in FIG. Figure 4 According to the above calculation formula, we can get Y 1.96 LuAl4GaO 12 :0.04Ce 3+ The quantum efficiency of the green fluorescent material can reach 99.68%, indicating that it has excellent luminescence quantum efficiency.

[0034] Example 5: Luminous intensity detection of fluorescent materials at different temperatures

[0035] The thermal stability of phosphors is a key technical parameter to measure the practical application potential of phosphors. By testing the emission spectra of commercial green fluorescent materials and the fluorescent materials of the present invention at different temperatures, the integrated luminous intensity of different fluorescent materials at different temperatures can be obtained by integrating the emission spectra. Taking the integrated luminous intensity at room temperature as a benchmark, the subsequent temperature points are normalized to obtain the relative percentage of the luminous intensity at different temperatures to the luminous intensity at room temperature. The luminous intensity of the green fluorescent material prepared when x is 0.04 as described in Example 1 at different temperatures is compared with the currently commonly used commercial green phosphors, as shown in FIG. Figure 5 As shown, the luminous intensity of the material of the present invention at 150 degrees Celsius is still 95.77% of that at room temperature, and as the temperature increases, the luminous intensity of the material of the present invention is better than that of other materials, and is still around 80% at 250 degrees Celsius, indicating that the thermal stability of the fluorescent material of the present invention is better than that of the currently commonly used commercial green phosphors, and has excellent thermal stability.

[0036] Example 6 Preparation of white light LED luminescent device

[0037] A white light LED luminescent device: The white light LED luminescent device comprises an InGaN semiconductor chip, a UV quick-drying resin glue, and two fluorescent materials that can effectively absorb the blue light emitted by the LED chip and release green and red light; wherein the green light fluorescent powder is the fluorescent material synthesized in the above embodiment 1 with x being 0.04, and its chemical composition formula is Y 2-x LuAl4GaO 12 :xCe 3+ , where x = 0.04. The peak wavelength of the InGaN semiconductor core is ~440nm, and the red phosphor is Sr2Si5N8:Eu 2+ (Purchased from Shenzhen Zhanwanglong Technology Co., Ltd.) The two phosphors are evenly dispersed in UV quick-drying resin glue, covered on the chip by coating or dispensing, and the circuit is connected to obtain the white light LED lighting device of the present invention.

[0038] The electroluminescence spectrum of LED light-emitting devices is as follows Figure 6 As shown, the color coordinate position is (0.4008, 0.3340), achieving warm white light emission. At 30 mA current, its color rendering index is 91.7, lumen efficiency is 39.18 lm / W, and color temperature is 3052 K, indicating that the fluorescent material of the present invention is a promising candidate material that can be applied to high-quality healthy lighting.

[0039] The conventional techniques and schemes not described in detail in the above embodiments are well known in the art, so they will not be described in detail here. The above embodiments and / or experimental examples describe the preferred embodiments of the present invention in detail, but 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, the technical scheme of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A gallium aluminate green light fluorescent material, characterized in that: The chemical composition formula of the luminescent material is Y 2- x LuAl4GaO 12 :xCe 3+ , where 0.003≤x≤0.

08.

2. The green fluorescent material according to claim 1, characterized in that: x＝0.04。 3. The method for preparing the green fluorescent material according to claim 1, characterized in that: The following steps are involved: 1) According to the general formula Y 2-x LuAl4GaO 12 :xCe 3+ The raw materials of yttrium source, lutetium source, gallium source, aluminum source and cerium source are accurately weighed according to the stoichiometric ratio; 2) grinding and mixing the raw materials of step 1) in ethanol to obtain a raw material mixture; 3) calcining the raw material mixture in step 2) at high temperature in an air atmosphere, and grinding to obtain a green fluorescent material; the high temperature calcination temperature is 1500-1700° C., the heating rate is 1-10° C. / min, and the insulation time is 4-10 hours.

4. The preparation method according to claim 3, characterized in that: The sources of the raw materials described in step 1) are specifically as follows: The yttrium source is yttrium oxide, yttrium carbonate or yttrium nitrate; the lutetium source is lutetium oxide, lutetium carbonate or lutetium nitrate; the gallium source is gallium oxide; the aluminum source is aluminum oxide, aluminum carbonate or aluminum nitrate; the cerium source is cerium nitrate, cerium oxide or cerium chloride.

5. The preparation method according to claim 3, characterized in that: The grinding time in step 2) is 30-60 minutes, and 10-20 mL of ethanol needs to be added during the grinding process; the grinding time in step 3) is 5-30 minutes.

6. The preparation method according to claim 3, characterized in that: The calcination in step 3) is to place the raw material mixture in an alumina crucible and calcine it in a tube furnace or a box furnace.

7. A white light LED lighting device, characterized in that: The invention comprises an InGaN semiconductor chip, a red fluorescent material and the green fluorescent material as claimed in claim 1, wherein the red fluorescent material and the green fluorescent material are covered on the LED chip.

8. The light emitting device according to claim 7, characterized in that: The peak wavelength of light emission of the InGaN semiconductor chip is 420-455nm.

9. The light emitting device according to claim 8, characterized in that: The red fluorescent material is Sr2Si5N8:Eu 2+ .

10. The light emitting device according to claim 8 or 9, characterized in that: The fluorescent material is evenly dispersed in UV quick-drying resin glue and then covered on the InGaN semiconductor chip by coating or dispensing.

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