A high-efficiency, high-thermal-stability green fluorescent ceramic for laser illumination and its preparation method

Abstract

This invention discloses a high-efficiency, high-thermal-stability green fluorescent ceramic for laser illumination and its preparation method. The molecular formula of the fluorescent ceramic is (Ce 0.005 Lu 0.995‑x Sr x )3(Al 1‑y Si y )5O 12 , where x is Sr 2+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ The molar percentage of x is 0.0025 < x ≤ 0.01, and 0.0015 < y ≤ 0.006. It is prepared by solid-state reaction sintering. The fluorescent ceramic of this invention emits green light near 520 nm when excited by a blue LD chip with a wavelength of 460 nm. It maintains 89%–100% of its room-temperature luminescence intensity at 423 K, exhibiting good thermal stability. Furthermore, under blue LD chip excitation, it displays a luminescence intensity greater than 70 W / mm². 2 It has an ultra-high brightness saturation threshold and a luminous efficiency of up to 287.5 lm / W. The preparation method is simple and can be applied to the industrial production of LED / LD devices.

Description

Technical Field

[0001] This invention relates to the field of fluorescent ceramics technology, specifically to a high-efficiency, high-thermal-stability green fluorescent ceramic for laser illumination and its preparation method. Background Technology

[0002] White light-emitting diodes (WLEDs) or laser diodes (WLDs) are highly valued for their environmental friendliness, small size, and long lifespan. Currently, the main method for constructing WLEDs / WLDs is to combine a blue LED / LD chip or a blue laser source with a CeO2 laser. 3+ :Y3Al5O 12 (Ce:YAG) materials are combined. However, phosphors encapsulated with conventional organic resins have low thermal conductivity (0.1-0.4 W / m²). -1 K -1) Phosphors are prone to combustion or carbonization at high temperatures, making them unsuitable for high-power LED or LD lighting. Therefore, phosphor conversion materials still need to meet stringent requirements, necessitating the exploration of novel phosphor materials with high thermal conductivity. Ce:YAG transparent ceramics (TCs), as a new generation of inorganic color conversion materials to replace organic resins, possess superior thermal conductivity (~14 W / m²). -1 K -1 Its rapid development is due to its excellent mechanical properties. However, in laser lighting applications, the "green canyon" problem is often more pronounced, and among currently commercially available green phosphors, (Ba,Sr)₂SiO₄:Eu 2+ BaSi2O2N2 suffers from poor thermal stability, exhibits severe thermal quenching, and is relatively expensive. Developing green light materials with high thermal stability and high luminous efficiency is urgently needed; however, current research on this issue is still limited.

[0003] To obtain green fluorescent materials with better thermal stability and higher luminescence efficiency, LuAG is often used as a phosphor conversion material to achieve spectral tunability and weak thermal quenching. The literature (High Efficiency Green-Emitting LuAG: Ce Ceramic Phosphors for Laser Diode Lighting) by Liu et al. co-doped Ba in Ce:LuAG... 2+ / Si 4+ Ion pairs, Ba 2+ The introduction of [a specific ingredient] improves the thermal stability of Ce:LuAG ceramics; at a temperature of 150°C, when Ba [a specific ingredient]... 2+ -Si 4 +When the relative intensity increased from 0 to 0.01, it increased from 76.4% to 91%, and the luminous efficiency reached 216.9 lm / W, but the improvement in thermal stability and luminous efficiency was limited. CN113683407A discloses a method for preparing a high-brightness, high-thermal-stability yellow-green fluorescent ceramic, which uses Li... + and Gd 3+ Incorporated into Ce:LuAG, but Gd 3+ The introduction of this technology inevitably leads to a decrease in the thermal stability of matrix luminescence, limiting its practical application in white LED / LD devices. Summary of the Invention

[0004] One of the objectives of this invention is to provide a high-efficiency, high-thermal-stability green fluorescent ceramic for laser lighting, which has the advantages of high luminous efficiency and good thermal stability.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned high-efficiency, high-thermal-stability green fluorescent ceramic, which is simple, quick, low-cost, and suitable for industrial production.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a high-efficiency, high-thermal-stability green fluorescent ceramic for laser illumination, the molecular formula of which is (Ce 0.005 Lu 0.995-x Sr x )3(Al 1-y Si y )5O 12 , where x is Sr 2+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ The percentage of moles in each position, 0.0025 < x ≤ 0.01, 0.0015 < y ≤ 0.006.

[0008] The fluorescent ceramic emits green light around 520nm when excited by a blue LD chip with a wavelength of 460nm. 2 + / Si 4+ Co-doping, by altering the chemical composition, reduces the torsion rate, enhances the strength of chemical bonds, and improves the structural stiffness of LuAG, thereby improving its thermal quenching performance. The fluorescent ceramic retains 89%–100% of its room-temperature luminescence intensity at 423 K, exhibiting excellent thermal stability. When excited by a blue LD chip at a wavelength of 460 nm, it displays a luminescence intensity greater than 70 W / mm². 2 It has an ultra-high brightness saturation threshold and a luminous efficiency of up to 259-288 lm / W.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned high-efficiency and high-thermal-stability green fluorescent ceramic, which adopts a solid-state reaction sintering method and includes the following steps:

[0010] (1) Using Lu2O3, CeO2, Al2O3, SrCO3, and SiO2 as raw material powders, according to the molecular formula (Ce 0.005 Lu 0.995-x Sr x )3(Al 1-y Si y )5O 12 Weigh each raw material according to the stoichiometric ratio of the corresponding elements, where x is Sr 2+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ The percentage of moles in each position, 0.0025 < x ≤ 0.01, 0.0015 < y ≤ 0.006.

[0011] (2) After weighing the raw material powder and dispersant polyetherimide, add anhydrous ethanol, ball mill and mix, dry the resulting slurry, sieve it, and then place the mixed powder in a muffle furnace for calcination.

[0012] (3) The calcined powder is placed in a mold and dry-pressed, and then cold isostatically pressed to obtain a green blank with a relative density of 50% to 55%.

[0013] (4) Vacuum sinter the green blank pressed in step (3), cool it to room temperature, and then put the ceramic into a muffle furnace for annealing. Finally, cut and polish the ceramic to obtain the green fluorescent ceramic.

[0014] Preferably, in step (1), the particle size of Lu2O3, Al2O3, SrCO3 and CeO2 is 1μm to 2μm, the particle size of SiO2 is 4μm to 5μm, and the purity is above 99.99%.

[0015] Preferably, in step (2), the amount of the dispersant polyetherimide added is 0.8 to 1 wt.% of the total mass of the raw material powder, and the mass ratio of the total mass of the raw material powder to anhydrous ethanol is 1:1.5 to 3.

[0016] Preferably, the ball milling speed in step (2) is 180-250 rpm and the ball milling time is 15-30 h.

[0017] Preferably, the drying temperature in step (2) is 50-80°C and the drying time is 8-12 hours.

[0018] Preferably, the calcination heating regime in step (2) is to raise the temperature to 600-800°C at a heating rate of 2-10°C / min at room temperature and hold it for 5-7 hours.

[0019] Preferably, the cold isostatic pressing pressure in step (3) is 150-200 MPa and the holding time is 5-10 min.

[0020] Preferably, the vacuum sintering temperature in step (4) is 1700-1800℃ and the holding time is 10-12h.

[0021] Preferably, the annealing temperature in step (4) is 1400-1500℃ and the annealing time is 4-6h.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The fluorescent ceramic of the present invention emits green light around 520nm when excited by a blue LD chip with a wavelength of 460nm. 2+ / Si 4+ Co-doping reduces the torsion rate, enhances the strength of chemical bonds, and improves the structural stiffness of LuAG by changing the chemical composition, thereby improving the thermal quenching performance. The fluorescent ceramic can still maintain 89% to 100% of the room temperature luminescence intensity at a temperature of 423K, and has good thermal stability.

[0024] (2) This invention uses LuAG as the matrix material and employs Ce 2+ As the sole luminescent ion, it exhibited a W / mm² > 70 W when excited by a blue LD chip. 2 It has an ultra-high brightness saturation threshold and a luminous efficiency of up to 287.5 lm / W.

[0025] (3) The high-efficiency, high-thermal-stability green fluorescent ceramic prepared by this invention is simple to prepare, takes little time, is green and environmentally friendly, and can be applied to the industrial production of LED / LD devices. Attached Figure Description

[0026] Figure 1 This is the XRD pattern of the fluorescent ceramic prepared in Example 1 of this invention;

[0027] Figure 2 These are normalized temperature-varying spectra of the fluorescent ceramics prepared in Examples 1-3 and Comparative Examples 1-2 of this invention under 460nm blue light excitation;

[0028] Figure 3 The fluorescent ceramics prepared in Examples 1-3 and Comparative Examples 1-2 of this invention exhibit luminous efficiency varying with power density when excited by a 460nm blue LD chip. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Unless otherwise specified, the raw material powders used in the following examples are all commercially available products. The particle size of Lu2O3, Al2O3, SrCO3, and CeO2 is 1μm to 2μm, and the particle size of SiO2 is 4μm to 5μm.

[0031] Example 1: Preparation of (Ce) 0.005 Lu 0.99 Sr 0.005 )3(Al 0.997 Si 0.003 )5O 12

[0032] The target product is set at 60g, based on the chemical formula (Ce 0.005 Lu 0.99 Sr 0.005 )3(Al 0.997 Si 0.003 )5O 12 According to the stoichiometric ratio of the corresponding raw materials, 41.71338g of Lu2O3, 0.09112g of CeO2, 17.93950g of Al2O3, 0.07815g of SrCO3, and 0.03180g of SiO2, all with a purity of 99.99%, were weighed out and mixed with 400μL of polyetherimide dispersant. Anhydrous ethanol was then added, and the mixture was thoroughly mixed using a planetary ball mill at 180 rpm for 20 hours. The resulting slurry was dried in an oven at 80℃ for 13 hours to obtain a mixed powder, which was then sieved twice through a 200-mesh sieve. The mixed powder was then calcined at 800℃ for 5 hours. The powder was then dried and pressed into a green blank in a steel mold, and cold isostatically pressed at 200MPa for 5 minutes to obtain a green blank with a relative density of 50%. Vacuum sintering was then performed at 1750℃ for 10 hours. The sintered ceramic was then annealed in a high-temperature muffle furnace at 1450℃ for 4 hours. Finally, the ceramic was polished to obtain fluorescent ceramic. This fluorescent ceramic has a diameter of approximately 17 mm and a thickness of 2 mm.

[0033] The crystal structure was studied using X-ray diffraction (XRD, Model D5005, Siemens), with a scanning angle 2θ ranging from 10° to 80°. The XRD patterns of the samples were obtained. Figure 1 The results show that the sample is consistent with the standard card (JCPDS 73-1368), indicating that Sr 2+ / Si 4+ The doping did not significantly affect the crystal structure, and the resulting fluorescent ceramic was similar to Lu3Al5O.12 It is a pure phase substance with isomorphism.

[0034] The thermal stability of the fluorescent ceramic was tested using a fluorescence spectrophotometer (OmniFluo 900, Zolix instruments). The results showed that under 460 nm blue light excitation, when the temperature was increased to 423 K, the luminescence intensity of the fluorescent ceramic remained at 100% of its room temperature luminescence intensity. Figure 2 As shown.

[0035] The luminous efficiency of this fluorescent ceramic was tested using an integrating sphere (R98, Everfine, Hangzhou, China). The results showed that, under excitation by a 460nm blue LD chip, it exhibited a luminous efficiency greater than 70 W / mm². 2 It boasts an ultra-high brightness saturation threshold and a luminous efficiency as high as 287.5 lm / W, such as Figure 3 As shown.

[0036] Example 2: Preparation of (Ce) 0.005 Lu 0.9875 Sr 0.0075 )3(Al 0.9955 Si 0.0045 )5O 12

[0037] The target product is set at 60g, based on the chemical formula (Ce 0.005 Lu 0.9875 Sr 0.0075 )3(Al 0.9955 Si 0.0045 )5O 12 According to the stoichiometric ratio of the corresponding raw materials, 41.67147g of Lu2O3, 0.09126g of CeO2, 17.93981g of Al2O3, 0.11741g of SrCO3, and 0.04778g of SiO2, all with a purity of 99.99%, and 400μL of polyetherimide dispersant were weighed out. After blending, anhydrous ethanol was added, and the mixture was thoroughly mixed using a planetary ball mill at 180 rpm for 20 hours. The resulting slurry was dried in an oven at 80℃ for 13 hours to obtain a mixed powder, which was then sieved twice through a 200-mesh sieve. The mixed powder was then calcined at 800℃ for 5 hours. The powder was then dried and pressed into a green blank in a steel mold, and cold isostatically pressed at 200 MPa for 5 minutes to obtain a green blank with a relative density of 50%. Vacuum sintering was then performed at 1750℃ for 10 hours. The sintered ceramic was then annealed in a high-temperature muffle furnace at 1450℃ for 4 hours. Finally, the ceramic was polished to obtain fluorescent ceramic. This fluorescent ceramic has a diameter of approximately 17 mm and a thickness of 2 mm.

[0038] The XRD pattern of the sample in this embodiment is similar to... Figure 1 Similarity indicates a pure phase.

[0039] The temperature-varying spectroscopy test results of this example sample show that, under 460 nm blue light excitation, when the temperature is increased to 423 K, the luminescence intensity of the fluorescent ceramic can still maintain 96.7% of the room temperature luminescence intensity. Figure 2 As shown.

[0040] The EL test results of this example sample show that, under excitation by a 460nm blue LD chip, it exhibits a power output greater than 70W / mm². 2 It has an ultra-high brightness saturation threshold and a luminous efficiency of 272.9 lm / W, such as Figure 3 As shown.

[0041] Example 3: Preparation of (Ce) 0.005 Lu 0.985 Sr 0.01 )3(Al 0.994 Si 0.006 )5O 12

[0042] The target product is set at 60g, based on the chemical formula (Ce 0.005 Lu 0.985 Sr 0.01 )3(Al 0.994 Si 0.006 )5O 12 According to the stoichiometric ratio of the corresponding raw materials, 41.56598g of Lu2O3, 0.09126g of CeO2, 17.91278g of Al2O3, 0.15655g of SrCO3, and 0.06372g of SiO2 (all with a purity of 99.99%), and 400μL of polyetherimide dispersant were weighed out, mixed, and then anhydrous ethanol was added. The mixture was thoroughly mixed using a planetary ball mill at 180 rpm for 20 hours. The resulting slurry was dried in an oven at 80℃ for 13 hours to obtain a mixed powder, which was then sieved twice through a 200-mesh sieve. The mixed powder was calcined at 800℃ for 5 hours. Then, it was dried and pressed into a green blank in a steel mold, and subjected to cold isostatic pressing at 200MPa for 5 minutes to obtain a green blank with a relative density of 50%. Vacuum sintering was then performed at 1750℃ for 10 hours. The sintered ceramic was then annealed in a high-temperature muffle furnace at 1450℃ for 4 hours. Finally, the ceramic was polished to obtain fluorescent ceramic. This fluorescent ceramic has a diameter of approximately 17 mm and a thickness of 2 mm.

[0043] The XRD pattern of the sample in this embodiment is similar to... Figure 1 Similarity indicates a pure phase.

[0044] The temperature-varying spectroscopy test results of this example sample show that, under 460 nm blue light excitation, when the temperature is increased to 423 K, the luminescence intensity of the fluorescent ceramic can still maintain 96.2% of the room temperature luminescence intensity. Figure 2 As shown.

[0045] The EL test results of this example sample show that, under excitation by a 460nm blue LD chip, it exhibits a power output greater than 70W / mm². 2 It has an ultra-high brightness saturation threshold and a luminous efficiency of 258.5 lm / W, such as Figure 3 As shown.

[0046] Comparative Example 1: (Ce 0.005 Lu 0.995 )3Al5O 12

[0047] The target product is set at 60g, based on the chemical formula (Ce 0.005 Lu 0.995 )3Al5O 12 According to the stoichiometric ratio of the corresponding raw materials, 41.83466g of Lu2O3, 0.18185g of CeO2, and 17.95511g of Al2O3 (all with a purity of 99.99%) were weighed out and mixed with 400μL of polyetherimide dispersant. Anhydrous ethanol was then added, and the mixture was thoroughly mixed using a planetary ball mill at 180 rpm for 20 hours. The resulting slurry was dried in an oven at 80℃ for 13 hours to obtain a mixed powder. This powder was then sieved twice through a 200-mesh sieve and calcined at 800℃ for 5 hours. The powder was then dried and pressed into a green blank in a steel mold, followed by cold isostatic pressing at 200MPa for 5 minutes to obtain a green blank with a relative density of 50%. Vacuum sintering was then performed at 1750℃ for 10 hours. The sintered ceramic was then annealed in a high-temperature muffle furnace at 1450℃ for 4 hours. Finally, the ceramic was polished to obtain fluorescent ceramic. This fluorescent ceramic has a diameter of approximately 17 mm and a thickness of 2 mm.

[0048] The XRD pattern of the sample in this embodiment is similar to... Figure 1 Similarity indicates a pure phase.

[0049] The temperature-varying spectroscopy test results of this example sample show that, under 460 nm blue light excitation, when the temperature is increased to 423 K, the luminescence intensity of the fluorescent ceramic can still maintain 88.6% of the room temperature luminescence intensity. Figure 2 As shown.

[0050] The EL test results of this example sample show that, under excitation by a 460nm blue LD chip, it exhibits a power output greater than 50W / mm². 2 The saturation threshold for ultra-high brightness is 56W / mm².2 Luminous saturation occurred, with a luminous efficiency of 267.7 lm / W. Figure 3 As shown.

[0051] Comparative Example 2: Preparation of (Ce) 0.005 Lu 0.9925 Sr 0.0025 )3(Al 0.9985 Si 0.0015 )5O 12

[0052] The target product is set at 60g, according to (Ce 0.005 Lu 0.9925 Sr 0.0025 )3(Al 0.9985 Si 0.0015 )5O 12 According to the stoichiometric ratio of the corresponding raw materials, 41.78692g of Lu2O3, 0.09105g of CeO2, 17.95283g of Al2O3, 0.03905g of SrCO3, and 0.01589g of SiO2, all with a purity of 99.99%, and 400μL of polyetherimide dispersant were weighed out. After blending, anhydrous ethanol was added, and the mixture was thoroughly mixed using a planetary ball mill at 180 rpm for 20 hours. The resulting slurry was dried in an oven at 80℃ for 13 hours to obtain a mixed powder, which was then sieved twice through a 200-mesh sieve. The mixed powder was then calcined at 800℃ for 5 hours. The powder was then dried and pressed into a green blank in a steel mold, and cold isostatically pressed at 200 MPa for 5 minutes to obtain a green blank with a relative density of 50%. Vacuum sintering was then performed at 1750℃ for 10 hours. The sintered ceramic was then annealed in a high-temperature muffle furnace at 1450℃ for 4 hours. Finally, the ceramic was polished to obtain fluorescent ceramic. This fluorescent ceramic has a diameter of approximately 17 mm and a thickness of 2 mm.

[0053] The XRD pattern of the sample in this embodiment is similar to... Figure 1 Similarity indicates a pure phase.

[0054] The temperature-varying spectroscopy test results of this example sample show that, under 460 nm blue light excitation, when the temperature is increased to 423 K, the luminescence intensity of the fluorescent ceramic can still maintain 92.3% of the room temperature luminescence intensity. Figure 2 As shown.

[0055] The EL test results of this example sample show that, under excitation by a 460nm blue LD chip, it exhibits a power output greater than 60W / mm². 2 The saturation threshold for ultra-high brightness is 65W / mm. 2 Luminous saturation occurred, with a luminous efficiency of 255.2 lm / W. Figure 3As shown.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-efficiency, high-thermal-stability green fluorescent ceramic for laser illumination, characterized in that, The molecular formula of this fluorescent ceramic is (Ce 0.005 Lu 0.995-x Sr x )3(Al 1-y Si y )5O 12 , where x is Sr 2+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ The percentage of moles in each position, 0.0025 < x ≤ 0.01, 0.0015 < y ≤ 0.

006.

2. A method for preparing the high-efficiency, high-thermal-stability green fluorescent ceramic according to claim 1, characterized in that, The solid-state reaction sintering method includes the following steps: (1) Using Lu2O3, Al2O3, SrCO3, SiO2 and CeO2 as raw material powders, according to the molecular formula (Ce 0.005 Lu 0.995-x Sr x )3(Al 1- y Si y )5O 12 Weigh each raw material according to the stoichiometric ratio of the corresponding elements, where x is Sr. 2+ Lu doping 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ The percentage of moles in each position, 0.0025 < x ≤ 0.01, 0.0015 < y ≤ 0.006; (2) After weighing the raw material powder and dispersant organic polyethyleneimine, add anhydrous ethanol, ball mill and mix, dry the resulting slurry, sieve, and then place the mixed powder in a muffle furnace for calcination. (3) The calcined powder is placed in a mold and dry-pressed, and then cold isostatically pressed to obtain a green blank with a relative density of 50% to 55%. (4) Vacuum sinter the green blank, cool it to room temperature, and then anneal the ceramic in a muffle furnace. Finally, cut and polish the ceramic to obtain the green fluorescent ceramic.

3. The preparation method of the high-efficiency, high-thermal-stability green fluorescent ceramic according to claim 2, characterized in that, In step (1), the particle size of Lu2O3, Al2O3, SrCO3 and CeO2 is 1μm to 2μm, and the particle size of SiO2 is 4μm to 5μm. The purity of all of them is above 99.99%.

4. The preparation method of the high-efficiency, high-thermal-stability green ceramic according to claim 2, characterized in that, The sieve used in step (2) is 80 to 200 mesh.

5. The method for preparing high-efficiency, high-thermal-stability green fluorescent ceramics according to claim 2, characterized in that, The cold isostatic pressing pressure in step (3) is 150-200 MPa, and the holding time is 5-10 min.

6. The method for preparing high-efficiency, high-thermal-stability green fluorescent ceramics according to claim 2, characterized in that, The vacuum sintering temperature in step (4) is 1700-1800℃, and the holding time is 10-12h.

7. The method for preparing high-efficiency, high-thermal-stability green fluorescent ceramics according to claim 2, characterized in that, The annealing temperature in step (4) is 1400-1500℃ and the annealing time is 4-6h.

Images