High-efficiency nitride oxide fluorescent ceramic for solid-state lighting and method for manufacturing the same

Abstract

This invention discloses a high color rendering index (CRI) oxide fluorescent ceramic for solid-state lighting and its preparation method. The general chemical formula of the fluorescent ceramic is: (Ca... 1‑x Ce x )3Sc2Si3O 12‑6y N 4y , where x is Ce 3+ Replace Ca 2+ The molar percentage of the position, 0.0001≤x≤0.005, y is N 3‑ Replace O 2‑ The molar percentage of O in the garnet matrix is ​​0.01≤y≤0.05; it is prepared by solid-state sintering. This invention uses Si3N4 doped fluorescent ceramics to remove O from the garnet matrix. 2‑ Replacement, with Ce 3+ It forms a new dodecahedron, with a new luminescent center at 570nm, achieving high-brightness white light emission with a color rendering index of 85-92. Moreover, the preparation process is simple and easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, specifically to a high color rendering index (CRI) oxynitride fluorescent ceramic for solid-state lighting and its preparation method. Background Technology

[0002] LED is a common solid-state lighting technology. Its working principle is that when an electric current passes through a semiconductor material, electrons and holes combine, releasing energy and producing photons. LEDs are widely used in lighting, displays, indicator lights, and automotive lighting. Current pcWLEDs often combine yellow-emitting Ce:YAG phosphor ceramics with blue LEDs. Garnet-based ceramic phosphors have advantages such as good thermal stability, high heat load capacity, high designability of chemical composition, and stable fluorescence performance. Ce is commonly used... 3+ A significant problem with doped garnet-based fluorescent ceramics is the lack of sufficient red light component, resulting in a relatively low color rendering index (CRI) of approximately 60. This leads to several drawbacks, including emission color shift and reduced visual comfort for the human eye. The literature (X. Liu, H. Zhou, Z. Hu, et al. Transparent Ce:GdYAG ceramic color converters for high-brightness white LEDs and LDs, Opt. Mater. 2019, 88: 97-102.) reports the use of Gd... 3+ Ion-doped YAG:Ce fluorescent ceramics effectively improve the color rendering index (CRI) of the ceramics, reaching a maximum of 67.2. Therefore, exploring a high CRI fluorescent ceramic material is crucial for achieving higher quality and more practical light sources.

[0003] Ca3Sc2Si3O 12 Ce fluorescent ceramics have an emission peak at 505 nm, which effectively solves the "blue light valley" problem. Secondly, the bluish-green emission peak reduces the Stokes shift, which helps reduce heat generation during emission. However, Ca3Sc2Si3O... 12 Ce fluorescent ceramics can only cover the emission peak of 490–600 nm, which cannot achieve a high color rendering index. Summary of the Invention

[0004] One objective of this invention is to provide a high color rendering index (CRI) oxynitride fluorescent ceramic for solid-state lighting, which has the advantage of a high CRI as a luminescent material.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned high color rendering index oxynitride fluorescent ceramic for solid-state lighting, which is easy to industrialize.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a high color rendering index (CRI) oxynitride fluorescent ceramic for solid-state lighting, wherein the general chemical formula of the fluorescent ceramic is:

[0007] (Ca 1-x Ce x )3Sc2Si3O 12-6y N 4y

[0008] Where x is Ce 3+ Replace Ca 2+ The molar percentage of the position, 0.0001≤x≤0.005, y is N 3- Replace O 2- The molar percentage of the position, 0.01≤y≤0.05.

[0009] The high color rendering index (CRI) oxynitride fluorescent ceramic provided by this invention emits deep red light under 455nm blue light excitation, with an emission wavelength range of 490–750 nm.

[0010] On the other hand, the present invention provides a method for preparing the above-mentioned high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting, specifically including the following steps:

[0011] (1) According to the chemical formula (Ca 1-x Ce x )3Sc2Si3O 12-6y N 4y The stoichiometric ratios of each element in the formula are as follows: Calcium oxide, scandium oxide, silicon dioxide, cerium oxide, and α-Si3N4 with a purity greater than 99.99% are weighed as raw material powders, where x represents Ce. 3+ Replace Ca 2 + The molar percentage of the position, 0.0001≤x≤0.005, y is N 3- Replace O 2- The molar percentage of the position is 0.01≤y≤0.05; the raw material powder and the ball milling media are mixed and ball milled in proportion to obtain a mixed slurry;

[0012] (2) Place the mixed slurry obtained in step (1) in a drying oven to dry, and then sieve the dried mixed powder;

[0013] (3) Place the powder after sieving in step (2) into a mold and dry press it into shape, and then perform cold isostatic pressing to obtain a green body with a relative density of 50% to 55%.

[0014] (4) Place the green blank obtained in step (3) in a vacuum furnace for sintering. First, raise the temperature to a sintering temperature of 1450℃~1550℃, then lower the temperature to 1400℃~1500℃ and hold for 8h~24h. The sintering vacuum degree should not be lower than 10. -3Pa, after heat preservation, is slowly cooled to room temperature to obtain fluorescent ceramics;

[0015] (5) Anneal the fluorescent ceramic obtained in step (4) in air to obtain a fluorescent ceramic with a relative density of 99.5% to 99.9%.

[0016] Preferably, in step (1), the ball milling medium is anhydrous ethanol, and the mass-to-volume ratio of the raw material powder to the ball milling medium is 1g:(2-4)mL.

[0017] Preferably, in step (1), the ball milling speed is 180 r / min to 220 r / min, and the ball milling time is 12 h to 18 h.

[0018] Preferably, in step (2), the drying temperature is 75℃~85℃ and the drying time is 20h~25h.

[0019] Preferably, in step (2), the mesh size of the sieve is 50 to 200 mesh, and the number of sieve passes is 1 to 3.

[0020] Preferably, in step (3), the cold isostatic pressing pressure is 150-200 MPa and the holding time is 200-400 s.

[0021] Preferably, in step (4), the heating rate during the vacuum sintering stage is 1 to 10 °C / min, the cooling rate from vacuum sintering to the heat preservation stage is 1 to 5 °C / min, and the cooling rate after the heat preservation is completed is 5 to 10 °C / min.

[0022] Preferably, in step (5), the annealing temperature is 1300-1450℃ and the holding time is 8h-24h.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The composite fluorescent material prepared by this invention achieves high-brightness white light emission when excited by a blue LED chip with a wavelength of 455nm, and its color rendering index is 85-92.

[0025] 2. In this invention, the addition of Si3N4 to the fluorescent ceramic can remove the O in the garnet matrix. 2- Replacement, with Ce 3+ A new dodecahedron is formed, and a new luminescent center appears at 570nm, effectively supplementing red light and improving the color rendering index.

[0026] 3. The Si3N4 doped fluorescent ceramic used in this invention helps to improve the crystal structure of the fluorescent ceramic, thereby enabling more excitation energy to be converted into visible light emission and enhancing the brightness of the fluorescent ceramic.

[0027] 4. The present invention has few process steps, the process conditions are not harsh and are easy to achieve; the resulting luminescent material is of high quality and can be widely used in the preparation of luminescent materials. Attached Figure Description

[0028] Figure 1 The images show the XRD patterns of the fluorescent ceramics prepared in Examples 1 to 3 of this invention.

[0029] Figure 2 The fluorescence spectra of the fluorescent ceramics prepared in Examples 1 to 3 of this invention are shown.

[0030] Figure 3 The electroluminescence spectrum of the fluorescent ceramic prepared in Example 1 of this invention is shown. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] The raw material powders used in the following examples are all commercially available products with a particle size of 60-80 nm and a purity of 99.99%.

[0033] Example 1: Preparation of a chemical formula (Ca) 0.999 Ce 0.001 )3Sc2Si3O 11.94 N 0.04 Fluorescent ceramics.

[0034] (1) According to the chemical formula (Ca 0.999 Ce 0.001 )3Sc2Si3O 11.94 N 0.04 The stoichiometric ratio of each element was determined by weighing out 60g of calcium oxide (CaO), scandium oxide (Sc2O3), silicon dioxide (SiO2), cerium oxide (CeO2), and α-Si3N4 as raw material powders. The raw material powders were mixed with 120mL of anhydrous ethanol and ball-milled for 12h at a speed of 180r / min to obtain a mixed slurry.

[0035] (2) Place the mixed slurry obtained in step (1) in an 80℃ drying oven and dry for 24 hours. Then, sieve the dried mixed powder through a 100-mesh sieve three times.

[0036] (3) Place the sieved powder from step (2) into a mold and dry press it into shape, then perform cold isostatic pressing at 200 MPa for 200 seconds.

[0037] (4) Place the green blank obtained in step (3) in a vacuum furnace for sintering. The temperature is increased at a rate of 10℃ / min to a sintering temperature of 1500℃, and then decreased to 1450℃ at a rate of 5℃ / min. The holding time is 10h, and the sintering vacuum degree is not less than 10. -3Pa, after the heat preservation is completed, slowly reduced to room temperature at a rate of 10℃ / min to obtain fluorescent ceramics; the first step of high-temperature sintering is conducive to rapid densification and grain growth, and the second step of reducing the temperature and heat preservation is conducive to grain boundary migration, eliminating pores and making the ceramic more dense.

[0038] (5) The fluorescent ceramic obtained in step (4) is annealed in air at a temperature of 1450°C for 10 hours to obtain a fluorescent ceramic with a relative density of 99.5% to 99.9%.

[0039] like Figure 1 As shown in the XRD pattern, no impurity phases were observed in the prepared fluorescent ceramic; as Figure 2 As shown in the fluorescence spectrum, the prepared fluorescent ceramic has two emission centers at 500 nm and 570 nm, covering the red and yellow light regions respectively; Figure 3 The electroluminescence spectrum was obtained by using a blue LED to excite the fluorescent ceramic. When the output power was 2W, the color rendering index reached as high as 92.

[0040] Example 2: Preparation of a chemical formula (Ca) 0.999 Ce 0.002 )3Sc2Si3O 11.88 N 0.08 Fluorescent ceramics.

[0041] (1) According to the chemical formula (Ca 0.999 Ce 0.002 )3Sc2Si3O 11.88 N 0.08 The stoichiometric ratio of each element was determined by weighing out 60g of calcium oxide (CaO), scandium oxide (Sc2O3), silicon dioxide (SiO2), cerium oxide (CeO2), and α-Si3N4 as raw material powders. The raw material powders were mixed with 180mL of anhydrous ethanol and ball-milled for 15h at a speed of 200r / min to obtain a mixed slurry.

[0042] (2) Place the mixed slurry obtained in step (1) in an 80℃ drying oven and dry for 24 hours. Then, sieve the dried mixed powder through a 100-mesh sieve three times.

[0043] (3) Place the powder after sieving in step (2) into a mold and dry press it into shape, then perform cold isostatic pressing at 200 MPa for 200 seconds.

[0044] (4) Place the green blank obtained in step (3) in a vacuum furnace for sintering. The temperature is increased at a rate of 10℃ / min to a sintering temperature of 1550℃, and then decreased to 1500℃ at a rate of 5℃ / min. The holding time is 10h, and the sintering vacuum degree is not less than 10. -3Pa, after the heat preservation is completed, slowly reduced to room temperature at a rate of 10℃ / min to obtain fluorescent ceramics; the first step of high-temperature sintering is conducive to rapid densification and grain growth, and the second step of reducing the temperature and heat preservation is conducive to grain boundary migration, eliminating pores and making the ceramic more dense.

[0045] (5) The fluorescent ceramic obtained in step (4) is annealed in air at a temperature of 1450°C for 10 hours to obtain a fluorescent ceramic with a relative density of 99.5% to 99.9%.

[0046] like Figure 1 As shown in the XRD pattern, no impurity phases appeared in the prepared fluorescent ceramic. Figure 2 As shown in the fluorescence spectrum, the prepared fluorescent ceramic has two emission centers at 500nm and 570nm, covering the red and yellow light regions respectively. When the fluorescent conversion composite material is excited by a blue LED, the color rendering index is as high as 90 when the output power is 2W.

[0047] Example 3: Preparation of a chemical formula (Ca) 0.999 Ce 0.003 )3Sc2Si3O 11.82 N 0.12 Fluorescent ceramics.

[0048] (1) According to the chemical formula (Ca 0.999 Ce 0.003 )3Sc2Si3O 11.82 N 0.12 The stoichiometric ratio of each element was determined by weighing out calcium oxide (CaO), scandium oxide (Sc2O3), silicon dioxide (SiO2), cerium oxide (CeO2), and α-Si3N4 as raw material powders, totaling 60g. The raw material powders were mixed with 240mL of anhydrous ethanol and ball-milled for 18h at a ball milling speed of 220r / min to obtain a mixed slurry.

[0049] (2) Place the mixed slurry obtained in step (1) in an 80℃ drying oven and dry for 24 hours. Then, sieve the dried mixed powder through a 100-mesh sieve three times.

[0050] (3) Place the sieved powder from step (2) into a mold and dry press it into shape, then perform cold isostatic pressing at 200 MPa for 200 seconds.

[0051] (4) Place the green blank obtained in step (3) in a vacuum furnace for sintering. The temperature is increased at a rate of 10℃ / min to a sintering temperature of 1450℃, and then decreased to 1400℃ at a rate of 5℃ / min. The holding time is 10h, and the sintering vacuum degree is not less than 10. -3Pa, after the heat preservation is completed, slowly reduced to room temperature at a rate of 10℃ / min to obtain fluorescent ceramics; the first step of high-temperature sintering is conducive to rapid densification and grain growth, and the second step of reducing the temperature and heat preservation is conducive to grain boundary migration, eliminating pores and making the ceramic more dense.

[0052] (5) Anneal the fluorescent ceramic obtained in step (4) in air at a temperature of 1450°C for 10 hours.

[0053] like Figure 1 As shown in the XRD pattern, no impurity phases appeared in the prepared fluorescent ceramic. Figure 2 As shown in the fluorescence spectrum, the prepared fluorescent ceramic has two emission centers at 500nm and 570nm, covering the red and yellow light regions respectively. When the fluorescent conversion composite material is excited by a blue LED, the color rendering index is as high as 88 when the output power is 2W.

[0054] 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 (CRI) oxide phosphor ceramic for solid-state lighting, characterized in that, The general chemical formula of this fluorescent ceramic is: (Ca 1-x Ce x )3Sc2Si3O 12-6y N 4y Where x is Ce 3+ Replace Ca 2+ The molar percentage of the position, 0.0001≤x≤0.002, y is N 3- Replace O 2- The molar percentage of the position, 0.01≤y≤0.02; The preparation of the fluorescent ceramic includes the following steps: (1) According to the chemical formula (Ca 1-x Ce x )3Sc2Si3O 12-6y N 4y The stoichiometric ratios of each element in the formula are as follows: Calcium oxide, scandium oxide, silicon dioxide, cerium oxide, and α-Si3N4 with a purity greater than 99.99% are weighed as raw material powders, where x represents Ce. 3+ Replace Ca 2+ The molar percentage of the position, 0.0001≤x≤0.002, y is N 3- Replace O 2- The molar percentage of the position is 0.01≤y≤0.02; the raw material powder and the ball milling media are mixed in proportion and ball milled to obtain a mixed slurry; (2) Place the mixed slurry obtained in step (1) in a drying oven to dry, and then sieve the dried mixed powder; (3) The powder after sieving in step (2) is placed in a mold and dry-pressed, and then cold isostatically pressed to obtain a green body with a relative density of 50% to 55%. (4) Place the green blank obtained in step (3) in a vacuum furnace for sintering. First, raise the temperature to the sintering temperature of 1450℃~1550℃ at a rate of 10℃ / min, and then lower the temperature to 1400℃~1500℃ at a rate of 5℃ / min. Hold the temperature for 8h~24h. The sintering vacuum degree shall not be lower than 10. -3 Pa, after heat preservation, is slowly cooled to room temperature to obtain fluorescent ceramics; (5) Anneal the fluorescent ceramic obtained in step (4) in air to obtain a fluorescent ceramic with a relative density of 99.5% to 99.9%.

2. The high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting according to claim 1, characterized in that, In step (1), the ball milling medium is anhydrous ethanol, and the mass-volume ratio of the raw material powder to the ball milling medium is 1 g: (2-4) mL.

3. The high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting according to claim 1, characterized in that, In step (1), the ball milling speed is 180 r / min to 220 r / min, and the ball milling time is 12 h to 18 h.

4. The high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting according to claim 1, characterized in that, In step (2), the drying temperature is 75℃~85℃ and the drying time is 20h~25h.

5. The high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting according to claim 1, characterized in that, In step (2), the mesh size of the sieve is 50 to 200 mesh, and the number of sieve passes is 1 to 3.

6. The high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting according to claim 1, characterized in that, In step (3), the cold isostatic pressing pressure is 150-200 MPa and the holding time is 200-400 s.

7. The high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting according to claim 1, characterized in that, In step (4), the cooling rate after the heat preservation is completed is 5-10℃ / min.

8. The high color rendering index (CRI) oxide nitride fluorescent ceramic for solid-state lighting according to claim 1, characterized in that, In step (5), the annealing temperature is 1300-1450℃ and the holding time is 8h-24h.

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