High-efficiency low-quenching nitroxide fluorescent ceramic for white LED and preparation method thereof

Abstract

The application discloses a high-color-rendering-index low-quenching nitride fluorescent ceramic for a white LED and a preparation method thereof. The fluorescent ceramic has a general chemical formula of (Lu 0.98‑x La x )3(Al 1‑y Si y )5(O 1‑ y N y ) 12 :0.06Ce, wherein x is the molar percentage of La 3+ doping Lu 3+ , y is the molar percentage of Si 4+ doping Al 3+ , or the molar percentage of N 3‑ doping O 2‑ , 0.001<=x<=0.12, 0.001<=y<=0.02. The preparation method comprises the following steps: firstly, weighing raw material powders; secondly, adding sintering aids and dispersants to prepare mixed slurry; thirdly, drying, sieving and calcining the mixed slurry to obtain a green body through dry pressing and cold isostatic pressing; and finally, high-temperature sintering and double-side polishing are sequentially performed to obtain the fluorescent ceramic. The method is simple in process, can reduce energy consumption and cost, and the obtained fluorescent ceramic has the advantages of high color rendering index, low concentration quenching and low heat quenching.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials for laser lighting, specifically to a high color rendering index and low quenching nitrogen oxide fluorescent ceramic for white LEDs and its preparation method. Background Technology

[0002] White light-emitting diodes (WLEDs) have been widely used in lighting and display fields due to their advantages such as long lifespan, high luminous efficiency, and environmental friendliness, and have replaced traditional incandescent or fluorescent lamps in many applications. However, high power and high color rendering index (CRI) remain obstacles in the development of WLEDs. There are generally two methods to improve the CRI of WLEDs. One simple, effective, and practical method is to add a red component to the yellow fluorescent conversion material to obtain high-quality white light. However, due to the interaction and performance differences between the two fluorescent conversion ions, this method may lead to reabsorption and color shift. Therefore, self-modification of fluorescent conversion materials has always been an attractive method to obtain materials with a single matrix, strong resistance to thermal quenching, and high color rendering performance.

[0003] Ce:YAG phosphor ceramics, due to their advantages such as high thermal conductivity, good thermal shock resistance, and low light decay, can effectively replace the traditional "Ce:YAG phosphor + organic resin" technology, and avoid the dispensing and mixing processes. Generally, several methods have been designed based on crystal field theory to realize YAG:Ce... 3+ The emission spectrum redshifts. These measures include increasing Ce... 3+ The concentration of Y partially replaces Y 3+ Gd 3+ , using Mg 2+ -Si 4+ / Ge 4+ For replacing Al 3+ -Al 3+ Or Y 3+ -Al 3+ , using Si 4+ -N 3- For replacing Al 3+ -O 2- However, none of these strategies help prevent the deterioration of emission efficiency or thermal stability. (Reference: Shao Q, et al., Temperature-dependent photoluminescence studies on Y...) 2.93-x Ln x Al5O 12 :Ce 0.07 The paper "(Ln=Gd,La)phosphors for white LEDs application" in J. Alloy. Compd. reports on La... 3+and Gd 3+ Co-doped YAG:Ce 3+ Compared to Gd doping alone 3+ It has better thermal stability.

[0004] In addition, Ce doping 3+ Lu3Al5O 12 (LuAG:Ce 3+ LuAG and YAG have the same structure, and LuAG:Ce 3+ It has a higher density than YAG:Ce 3+ Higher luminescence intensity, quantum yield, and thermal stability. CN106242539A describes a method for preparing nitride phosphor ceramics using secondary sintering. This process results in significant energy consumption and low efficiency, making it difficult to meet the needs of industrial production and market applications. Furthermore, since the luminescent ions in nitride phosphor preparation have high requirements for the crystal matrix structure, using a mature phosphor ceramic preparation process, combined with vacuum sintering and atmosphere sintering, allows for prolonged high-temperature holding, promoting the entry of more substitution ions into the crystal lattice. Summary of the Invention

[0005] The purpose of this invention is to provide a high color rendering index and low quenching nitrogen oxide fluorescent ceramic for white LEDs and its preparation method. The method is simple, can reduce energy consumption and lower costs, and the prepared fluorescent ceramic can have the advantages of high color rendering index, low concentration quenching and low thermal quenching.

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

[0007] A high color rendering index and low quenching nitrogen oxide fluorescent ceramic for white LEDs has the general chemical formula: (Lu 0.98-x La x )3(Al 1-y Si y )5(O 1-y N y ) 12 :0.06Ce, where x is La 3+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ mole percentage or 3- O doping 2- The mole percentage of the place, 0.001≤x≤0.12, 0.001≤y≤0.02.

[0008] The present invention also provides a method for preparing the above-mentioned high color rendering index and low quenching nitride fluorescent ceramic for white LEDs, the specific steps of which are as follows:

[0009] (1) Using Lu2O3, La2O3, Al2O3, CeO2 and Si3N4 as initial raw material powders, according to the chemical formula (Lu 0.98-x La x )3(Al 1-y Si y )5(O 1-y N y ) 12 Weigh each raw material according to the stoichiometric ratio of the corresponding elements in 0.06Ce, where x is La. 3+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ mole percentage or N 3- O doping 2- The mole percentage of each position, 0.001≤x≤0.12, 0.001≤y0.02;

[0010] (2) After mixing the weighed initial raw material powder, add sintering aid, dispersant and anhydrous ethanol as medium, and then place it in a ball mill jar for planetary ball milling to obtain a mixed slurry;

[0011] (3) Dry and sieve the mixed slurry, and then calcine the powder in a muffle furnace;

[0012] (4) The calcined powder is dry-pressed and then sealed in plastic. The green blank is then cold-isostatically pressed to obtain a green blank with a relative density of 50% to 55%.

[0013] (5) The green blank obtained in step (4) is placed in a reducing atmosphere at high temperature for sintering, cooled to room temperature and then polished on both sides to obtain the nitrogen oxide fluorescent ceramic.

[0014] Preferably, in step (1), the sintering aid is NaF and TEOS, and the amount added is 0.2-0.7 wt.% and 0.4-0.6 wt.% of the total mass of the raw material powder, respectively; the dispersant is PEI, and the amount added is 0.2-0.5 wt.% of the total mass of the raw material powder.

[0015] Preferably, in step (2), the ball milling time is 15-20 hours and the rotation speed is 120-160 r / min.

[0016] Preferably, in step (3), the calcination temperature is 400-900℃, the heating rate is 2-6℃ / min, the holding time is 3-6h, and then the temperature is reduced to room temperature at a cooling rate of 10-30℃ / min.

[0017] Preferably, in step (3), the drying temperature is 45-50℃ and the time is 8-12h.

[0018] Preferably, in step (4), the pressure of the dry pressing is 15-25 MPa and the time is 20-40 s; the pressure of the cold isostatic pressing is 180-240 MPa and the holding time is 300-360 s.

[0019] Preferably, in step (5), the sintering temperature is 1760-1800℃, the sintering time is 5-12h, the sintering atmosphere is a mixture of hydrogen and nitrogen, and the volume ratio of hydrogen to nitrogen is 1:(1-2).

[0020] Compared with existing technical solutions, the present invention has the following advantages:

[0021] (1) The present invention incorporates Si into the LuAG matrix. 4+ -N 3- The fluorescent ceramics not only achieve a wide range of redshift in the spectrum, but also give the prepared fluorescent ceramics the characteristics of high color rendering index, low concentration quenching and low thermal quenching.

[0022] (2) This invention controls La within a small range in the LuAG body. 3+ Concentration, its photoluminescence spectrum can exhibit obvious tunable characteristics, which is consistent with N 3- It is related to the selective coordination of nitrogen redistribution;

[0023] (3) The present invention adopts dry pressing combined with atmosphere sintering, which not only ensures the stability of the nitrogen oxide crystal field structure, but also shortens the preparation time, reduces energy consumption, and lowers costs.

[0024] (4) The white LED device prepared by the present invention, after being packaged with a high color rendering index and low quenching nitrogen oxide fluorescent ceramic and a blue LED chip, has a luminous efficiency of 150-200 lm / W, a color rendering index of 80-90, a color temperature of 3500-4500K, and an emission intensity loss of only 2.3-4.1% at 150℃. Attached Figure Description

[0025] Figure 1 The XRD pattern of the sample prepared in Example 3 of this invention;

[0026] Figure 2 The electroluminescence spectrum of the sample prepared in Example 3 of this invention under 455nm blue LED excitation;

[0027] Figure 3 The graph shows the change in luminescence intensity of the sample prepared in Example 3 of this invention and LuAG:0.06Ce as a function of temperature. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The silicon nitride used in the following examples is the α phase, with a purity greater than 99.9% and an average particle size of 20-100 nm. The purity of the other raw materials used is greater than 99.9%.

[0030] Example 1

[0031] Nitrogen oxide fluorescent ceramics (Lu 0.979 La 0.001 )3(Al 0.999 Si 0.001 )5(O 0.999 N 0.001 ) 12 The preparation method of 0.06Ce is as follows:

[0032] (1) According to the chemical formula (Lu 0.979 La 0.001 )3(Al 0.999 Si 0.001 )5(O 0.999 N 0.001 ) 12 The stoichiometric ratio of each element in 0.06Ce was as follows: 60.048g of raw material powder consisting of Lu2O3 (41.268g), La2O3 (0.057g), Al2O3 (17.983g), CeO2 (0.729g), and Si3N4 (0.011g).

[0033] (2) After mixing the weighed initial raw material powder, add sintering aid (0.14g NaF and 0.27g TEOS), dispersant (0.14g PEI) and anhydrous ethanol as medium, and then place it in a nylon ball mill jar and perform planetary ball milling at 120r / min for 15h to obtain a mixed slurry.

[0034] (3) The mixed slurry is dried in an oven at 45°C for 8 hours. Then it is passed through an 80-mesh sieve. The powder is then placed in a muffle furnace for calcination at 400°C at a heating rate of 2°C / min and a holding time of 6 hours. The powder is then cooled to room temperature at a cooling rate of 10°C / min.

[0035] (4) Pour the calcined powder into the mold, press it under 15MPa pressure for 20s, seal it, and then cold isostatically press the blank under 180MPa pressure for 300s to obtain a blank with a relative density of 50%.

[0036] (5) The green blank obtained in step (4) is placed in a reducing atmosphere at high temperature for sintering, cooled to room temperature and then polished on both sides to obtain the nitrogen oxide fluorescent ceramic; the sintering regime is: sintering temperature is 1760℃, sintering time is 5h, sintering atmosphere is a mixed atmosphere of hydrogen and nitrogen, and the volume ratio between hydrogen and nitrogen is 1:2.

[0037] The white LED device prepared by the fluorescent ceramic encapsulation in this embodiment has a luminous efficiency of 152 lm / W, a color rendering index of 82, a color temperature of 4400K, and an emission intensity loss of only 3.9% at 150℃.

[0038] Example 2

[0039] Nitrogen oxide fluorescent ceramics (Lu 0.97 La 0.01 )3(Al 0.99 Si 0.01 )5(O 0.99 N 0.01 ) 12 The preparation method of 0.06Ce is as follows:

[0040] (1) According to the chemical formula (Lu 0.97 La 0.01 )3(Al 0.99 Si 0.01 )5(O 0.99 N 0.01 ) 12 The stoichiometric ratio of each element in 0.06Ce was as follows: 60.192g of raw material powder consisting of Lu2O3 (40.935g), La2O3 (0.576g), Al2O3 (17.841g), CeO2 (0.730g), and Si3N4 (0.110g).

[0041] (2) After mixing the weighed initial raw material powder, add sintering aid (0.325g NaF and 0.325g TEOS), dispersant (0.18g PEI) and anhydrous ethanol as a medium, and then place it in a nylon ball mill jar and perform planetary ball milling at 140r / min for 18h to obtain a mixed slurry.

[0042] (3) The mixed slurry is dried in an oven at 47°C for 10 hours. Then it is passed through an 80-mesh sieve. The powder is then placed in a muffle furnace for calcination at 600°C at a heating rate of 4°C / min and a holding time of 4 hours. The powder is then cooled to room temperature at a cooling rate of 20°C / min.

[0043] (4) Pour the calcined powder into the mold, press it under 20MPa pressure for 30s, seal it, and then cold isostatically press the green blank under 200MPa pressure for 320s to obtain a green blank with a relative density of 53%.

[0044] (5) The green blank obtained in step (4) is placed in a reducing atmosphere at high temperature for sintering, cooled to room temperature and then polished on both sides to obtain the nitrogen oxide fluorescent ceramic; the sintering regime is: sintering temperature is 1780℃, sintering time is 8h, sintering atmosphere is a mixed atmosphere of hydrogen and nitrogen, and the volume ratio between hydrogen and nitrogen is 1:2.

[0045] The white LED device prepared by the fluorescent ceramic encapsulation in this embodiment has a luminous efficiency of 176 lm / W, a color rendering index of 85, a color temperature of 3900K, and an emission intensity loss of only 3.1% at 150℃.

[0046] Example 3

[0047] Nitrogen oxide fluorescent ceramics (Lu 0.86 La 0.12 )3(Al 0.98 Si 0.02 )5(O 0.98 N 0.02 ) 12 The preparation method of 0.06Ce is as follows:

[0048] (1) According to the chemical formula (Lu 0.97 La 0.01 )3(Al 0.99 Si 0.01 )5(O 0.98 N 0.01 ) 12 The stoichiometric ratio of each element in 0.06Ce was as follows: 62.69g of raw material powder consisting of Lu2O3 (36.807g), La2O3 (7.008g), Al2O3 (17.911g), CeO2 (0.740g), and Si3N4 (0.224g).

[0049] (2) After mixing the weighed initial raw material powder, add sintering aid (0.4g NaF and 0.35g TEOS), dispersant (0.3g PEI) and anhydrous ethanol as medium, and then place it in a nylon ball mill jar and perform planetary ball milling at 160r / min for 20h to obtain a mixed slurry.

[0050] (3) The mixed slurry is dried in an oven at 50°C for 12 hours. Then it is passed through an 80-mesh sieve. The powder is then placed in a muffle furnace for calcination at 900°C at a heating rate of 6°C / min and a holding time of 3 hours. The powder is then cooled to room temperature at a cooling rate of 30°C / min.

[0051] (4) Pour the calcined powder into the mold, press it under 25MPa pressure for 40s, seal it, and then cold isostatically press the green blank under 240MPa pressure for 360s to obtain a green blank with a relative density of 55%.

[0052] (5) The green blank obtained in step (4) is placed in a reducing atmosphere at high temperature for sintering, cooled to room temperature and then polished on both sides to obtain the nitrogen oxide fluorescent ceramic; the sintering regime is: sintering temperature is 1800℃, sintering time is 12h, sintering atmosphere is a mixed atmosphere of hydrogen and nitrogen, and the volume ratio between hydrogen and nitrogen is 1:1.

[0053] See attached Figure 1 The X-ray diffraction pattern of the sample prepared in this embodiment, and the XRD test results show that the X-rays of the prepared sample are consistent with the standard card of lutetium aluminum garnet (PDF#18-0761), proving that Al 3+ -N 3- and La 3+ The bonds successfully replaced Al. 3+ -O 2- and Lu 3+ The bonds enter the crystal lattice without causing the lattice to be destroyed.

[0054] See attached Figure 2 The electroluminescence spectrum of the sample prepared in Example 3 of this invention under 455nm blue LED excitation shows that the central wavelength range of the yellow light region is located at 585nm, which is 65nm redshifted compared to the traditional Ce:LuAG fluorescent ceramic material (520nm), effectively supplementing the red part of the spectrum. The color rendering index is 88 and the luminous efficiency is 198lm / W.

[0055] See attached Figure 3 The graph shows the change in luminescence intensity of the sample prepared in this embodiment and LuAG:0.06Ce as a function of temperature. It can be seen from the graph that the luminescence intensity of the La-doped sample... 3+ The Ce:LuAG fluorescent ceramic exhibited an emission intensity of 97.7% of its original intensity at 150°C, which was lower than that of the undoped La. 3+ The Ce:LuAG fluorescent ceramic showed a 95% increase in purity (2.7%), with only a 2.3% loss due to weakened thermal quenching. This indicates that the introduction of La... 3+ It is beneficial to improve the thermal stability of lutetium aluminum garnet.

[0056] The white LED device prepared by the fluorescent ceramic encapsulation in this embodiment has a luminous efficiency of 198 lm / W, a color rendering index of 88, a color temperature of 3600K, and an emission intensity loss of only 2.3% at 150℃.

[0057] 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 color rendering index, low quenching oxide phosphor ceramic for white LEDs, characterized in that, Its general chemical formula is: (Lu 0.98-x La x )3(Al 1-y Si y )5(O 1-y N y ) 12 :0.06Ce, where x is La 3+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ mole percentage or N 3- O doping 2- The mole percentage of the place, 0.001≤x≤0.12, 0.001≤y≤0.

02.

2. A method for preparing the high color rendering index and low quenching nitride fluorescent ceramic for white LEDs as described in claim 1, characterized in that, The specific steps are as follows: (1) Using Lu2O3, La2O3, Al2O3, CeO2 and Si3N4 as initial raw material powders, according to the chemical formula (Lu 0.98-x La x )3(Al 1- y Si y )5(O 1-y N y ) 12 Weigh each raw material according to the stoichiometric ratio of the corresponding elements in 0.06Ce, where x is La. 3+ Lu-doped 3+ The mole percentage of Si, y is Si 4+ Doped Al 3+ mole percentage or N 3- O doping 2- The percentage of moles in each place, 0.001≤x≤0.12, 0.001≤y≤0.02; (2) After mixing the weighed initial raw material powder, add sintering aid, dispersant and anhydrous ethanol as medium, and then place it in a ball mill jar for planetary ball milling to obtain a mixed slurry; (3) Dry and sieve the mixed slurry, and then calcine the powder in a muffle furnace; (4) The calcined powder is dry-pressed and then sealed in plastic before being cold-isostatically pressed to obtain a green blank with a relative density of 50%~55%. (5) The green blank obtained in step (4) is placed in a reducing atmosphere at high temperature for sintering, cooled to room temperature and then polished on both sides to obtain the nitrogen oxide fluorescent ceramic.

3. The method for preparing a high color rendering index and low quenching nitride fluorescent ceramic for white LEDs according to claim 2, characterized in that, In step (2), the sintering aids are NaF and TEOS, and the amounts added are 0.2~0.7wt.% and 0.4~0.6wt.% of the total mass of the raw material powder, respectively; the dispersant is PEI, and the amount added is 0.2~0.5wt.% of the total mass of the raw material powder.

4. A method for preparing a high color rendering index, low quenching nitride fluorescent ceramic for white LEDs according to claim 2 or 3, characterized in that, In step (2), the ball milling time is 15~20h and the rotation speed is 120~160r / min.

5. A method for preparing a high color rendering index, low quenching nitride fluorescent ceramic for white LEDs according to claim 2 or 3, characterized in that, In step (3), the calcination temperature is 400~900℃, the heating rate is 2~6℃ / min, the holding time is 3~6h, and then the temperature is reduced to room temperature at a cooling rate of 10~30℃ / min.

6. A method for preparing a high color rendering index, low quenching nitride fluorescent ceramic for white LEDs according to claim 2 or 3, characterized in that, In step (3), the drying temperature is 45~50℃ and the time is 8~12h.

7. A method for preparing a high color rendering index, low quenching nitride fluorescent ceramic for white LEDs according to claim 2 or 3, characterized in that, In step (4), the pressure of dry pressing is 15~25 MPa and the time is 20~40 s; the pressure of cold isostatic pressing is 180~240 MPa and the holding time is 300~360 s.

8. A method for preparing a high color rendering index, low quenching nitride fluorescent ceramic for white LEDs according to claim 2 or 3, characterized in that, In step (5), the sintering temperature is 1760~1800℃, the sintering time is 5~12h, the sintering atmosphere is a mixture of hydrogen and nitrogen, and the volume ratio between hydrogen and nitrogen is 1:(1~2).

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