CN117326858A - Garnet-based red fluorescent ceramic for high-power illumination and preparation method thereof - Google Patents

Abstract

The invention discloses a garnet-based red fluorescent ceramic for high-power lighting and a preparation method thereof. The chemical composition of red fluorescent ceramics is: (Sr _1‑x Eu _x ) ₃ (Al _1‑y Sc _y ) ₂ Si ₃ O ₁₂ , where x is the molar percentage of Eu ²⁺ doped Sr ³⁺ position, and y is The mole percentage of Sc ³⁺ doped Al ³⁺ position, 0.002≤x≤0.03, 0.1≤y≤0.5; is produced by solid-phase sintering using silica, alumina, strontium carbonate and europium oxide as raw material powders. The red fluorescent material provided by the present invention emits red light under blue light excitation, and the emission wavelength range is between 550 and 750 nm. When combined with the green light fluorescent ceramics Ce:YAG, Ce:LuAG, etc. in the prior art, it can emit red light under blue light excitation. Obtaining high-quality white light can meet the needs of different types of light sources in the field of general lighting.

Description

A garnet-based red fluorescent ceramic for high-power lighting and its preparation method

Technical field

The invention belongs to the technical field of luminescent materials, and specifically relates to a garnet-based red fluorescent ceramic for high-power lighting and a preparation method thereof.

Background technique

White light LEDs converted by fluorescent materials have many advantages such as energy saving, environmental protection, and long service life. They are considered to be the fourth generation of white light sources and are used in lighting and display fields. However, as the input current density increases, LED chips face the problem of "efficiency sudden drop" that has nothing to do with heat, which is not conducive to their application in high-brightness, high-power white light lighting and displays.

High-power WLEDs and laser lighting technology have the advantages of high efficiency, high brightness, long life, low energy consumption, and environmental protection, and are currently hot research topics in the field of solid-state lighting displays. Commercial WLEDs are obtained by combining blue LED chips and YAG:Ce yellow phosphors. The preparation technology is mature and the cost is relatively low. However, the phosphors need to be encapsulated in resin, and the resin is easy to age and has low thermal conductivity, which seriously affects its long-term use. Therefore, ceramic phosphors with high thermal conductivity and no need for packaging have emerged. The current mainstream Y/LuAG:Ce yellow/green fluorescent ceramics have achieved some results. However, the white light obtained by mixing blue light and yellow light still has the problem of high color temperature and low color rendering index due to the lack of red light component in the spectrum. Adding red phosphor is one of the effective ways to solve this problem, so we urgently need to prepare efficient and reliable red fluorescent ceramics.

Nitride/oxynitride phosphors based on Eu ²⁺ doping are representatives of red phosphors, but their production costs are high and their emission spectra are narrow, which largely limits their wide application; and due to the Due to its low diffusion coefficient, nitride is difficult to make into fluorescent ceramics. Researchers at Xiamen University performed SPS sintering of CaAlSiN ₃ :Eu ²⁺ nitride red phosphor to obtain ceramics, and introduced Si ₃ N ₄ and SiO ₂ as sintering aids to densify the ceramics. However, the luminescence performance has declined to a certain extent (Document: CaAlSiN ₃ :Eu ²⁺ translucent ceramic: a promising robust and efficient red color converter for solid state laser displays and lighting; doi.org/10.1039/C6TC02518H). The red phosphor of the oxide system has good stability, can optimize the luminous efficiency, has a simple and clear adjustment mechanism for luminous efficiency improvement, and has a simple preparation process. It is suitable for making fluorescent ceramic materials.

Contents of the invention

One of the purposes of the present invention is to provide a garnet-based red fluorescent ceramic for high-power lighting, so as to solve the high temperature, high pressure and other conditions required of nitride red fluorescent ceramics in the prior art;

The second object of the present invention is to provide the above-mentioned preparation method of garnet-based red fluorescent ceramics for high-power lighting. The method is simple, the economic cost is low, and it is suitable for general promotion and use.

In order to achieve the above objects, the present invention adopts the following technical solutions:

On the one hand, the present invention provides a garnet-based red fluorescent ceramic for high-power lighting. The chemical composition of the red fluorescent ceramic is:

(Sr _1-x Eu _x ) ₃ (Al _1-y Sc _y ) ₂ Si ₃ O ₁₂

Among them, x is the mole percentage of Eu ²⁺ doped with Sr ³⁺ site, y is the mole percentage of Sc ³⁺ doped with Al ³⁺ site, 0.002≤x≤0.03, 0.1≤y≤0.5.

The red fluorescent material provided by doping europium ions in the present invention emits red light under blue light excitation, and the emission wavelength range is between 550 and 750 nm.

On the other hand, the present invention also provides the above-mentioned preparation method for high-power lighting garnet-based red fluorescent ceramics, which specifically includes the following steps:

_{( 1} ) Weigh silica _, alumina _{, strontium carbonate ,} scandium _oxide and Europium oxide is used as raw material powder, and the sintering aid boric acid and ball milling medium are added for mixing and ball milling to obtain a mixed slurry; where x is the mole percentage of Eu ²⁺ doped Sr ³⁺ position, and y is Sc ³⁺ doped Al The molar percentage of ³⁺ position, 0.002≤x≤0.03, 0.1≤y≤0.5;

(2) Dry the mixed slurry obtained in step (1) in a drying box, and then sieve the dried mixed powder;

(3) Place the sieved powder in step (2) into a grinding tool for dry pressing, and then perform cold isostatic pressing to obtain a green body with a relative density of 50% to 55%;

(4) Place the green body obtained in step (3) for sintering in a vacuum furnace at a sintering temperature of 1200 to 1400°C, a holding time of 10 to 24 hours, and a sintering vacuum degree of not less than 10 ^-3 Pa to obtain fluorescent ceramics;

(5) Anneal the fluorescent ceramic obtained in step (4) in a reducing atmosphere at an annealing temperature of 1050-1200°C and a holding time of 8-24 hours to obtain the red fluorescent ceramic.

Preferably, the amount of boric acid added in step (1) is 1 to 3% of the total mass of the raw material powder; the ball milling speed is 160 to 200 r/min, and the ball milling time is 15 to 20 hours.

Preferably, the drying time in step (2) is 20 to 30 hours, and the drying temperature is 80 to 90°C.

Preferably, the cold isostatic pressing holding pressure described in step (3) is 150-300Mpa, and the holding time is 200-400s.

Preferably, the temperature rising rate during the vacuum sintering stage in step (4) is 2-10°C/min, and the temperature cooling rate after sintering is completed is 2-10°C/min.

Preferably, the reducing atmosphere described in step (5) is a mixed gas of 10-20% _H2 and 80-90% _N2 .

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

1. The present invention uses Eu ²⁺ and Sc ³⁺ to replace Sr ²⁺ and Al ³⁺ respectively. Here, Eu ²⁺ ions are incorporated into the Sr ₃ Al ₂ Si ₃ O ₁₂ matrix as luminescent ions to achieve red light emission, and Sc ³ The introduction of ⁺ enhances the rigidity of the crystal structure and improves the thermal stability of the material.

2. The garnet-based red fluorescent ceramic for high-power lighting of the present invention has a broad and strong excitation in the blue light band, and the emission spectrum is located between 550nm and 750nm. It can be adapted to blue LED/LD and can meet industrial needs to a large extent.

3. The preparation method of the garnet-based red fluorescent ceramic for high-power lighting of the present invention is simple and easy to operate. Compared with nitride ceramics, it does not require high-pressure experimental conditions. The economic cost is reduced and it is suitable for general promotion and use.

4. The combination of the garnet-based red fluorescent ceramic for high-power lighting of the present invention and the existing green fluorescent ceramics Ce:YAG, Ce:LuAG, etc. can obtain high-quality white light under blue light excitation, which can meet the general needs The demand for different types of light sources in the lighting field.

Description of drawings

Figure 1 is an XRD pattern of the fluorescent material prepared in Examples 1 to 3 of the present invention;

Figure 2 is the excitation spectrum of the fluorescent material prepared in Example 3 of the present invention;

Figure 3 is the emission spectrum of the fluorescent material prepared in Example 3 of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1: Preparation of a red fluorescent material with the chemical formula (Sr _0.998 Eu _0.002 ) ₃ (Al _0.9 Sc _0.1 ) ₂ Si ₃ O ₁₂ .

( ₁ ) Set _the target product mass _{to 20g} , weigh _silica ( _{4.315g ) ,} oxidation Aluminum (4.393g), strontium carbonate (10.580g), europium oxide (0.050g) and scandium oxide (0.660g) are used as raw material powders, and 1% of the total mass of raw material powders is added with boric acid (0.2g) as a sintering aid. , mix the raw material powder with 60mL of absolute ethanol, and conduct ball milling in a ball milling tank. The ball milling speed is 160r/min and the ball milling time is 15h;

(2) Dry the mixed slurry obtained in step (1) in a drying oven at 90°C for 20 hours, and then sieve the dried mixed powder three times through an 80-mesh screen;

(3) Put the sieved powder in step (2) into a grinding tool for dry pressing, and then perform cold isostatic pressing with a pressure of 150MPa and a holding time of 200s to obtain a blank with a relative density of 50.0%. ;

(4) Place the blank obtained in step (3) for sintering in a vacuum furnace, raise the temperature to a sintering temperature of 1200℃ at a rate of 2℃/min, hold the temperature for 10h, and sintering vacuum degree of 10 ^-3 Pa. After sintering is completed, continue with 2 The rate is reduced to room temperature at a rate of ℃/min to obtain fluorescent ceramics;

(5) Anneal the fluorescent ceramic obtained in step (4) in a reducing atmosphere of 10% H ₂ : 90% N ₂ at an annealing temperature of 1050°C and a holding time of 8 hours to obtain the final required sample.

The XRD measured for the fluorescent material of (Sr _0.998 Eu _0.002 ) ₃ (Al _0.9 Sc _0.1 ) ₂ Si ₃ O ₁₂ obtained in this example has no impurity peaks compared to the crystal phase of Sr ₃ Al ₂ Si ₃ O ₁₂ . This indicates that the doping ions have completely entered the crystal lattice. As shown in Figure 1; the excitation spectrum of the provided fluorescent material is between 350nm and 550nm; it emits red light under blue light excitation, and the emission wavelength range is between 550nm and 750nm.

Example 2: Preparation of a red fluorescent material with a chemical formula of (Sr _0.99 Eu _0.01 ) ₃ (Al _0.7 Sc _0.3 ) ₂ Si ₃ O ₁₂ .

(1) Set the target product mass to 20g. According to the stoichiometric ratio of each element of the chemical formula (Sr _0.99 Eu _0.01 ) ₃ (Al _0.7 Sc _0.3 ) ₂ Si ₃ O ₁₂ , weigh silica (4.217g) and oxidation respectively. Aluminum (3.340g), strontium carbonate (10.259g), europium oxide (0.247g) and scandium oxide (1.936g) are used as raw material powders, and boric acid (0.6g), which is 3% of the total mass of the raw material powders, is added as a sintering aid. , mix the raw material powder with 60mL of absolute ethanol, and conduct ball milling in a ball milling tank. The ball milling speed is 180r/min and the ball milling time is 18h;

(2) Dry the mixed slurry obtained in step (1) in a drying oven at 85°C for 25 hours, and then sieve the dried mixed powder through an 80-mesh screen;

(3) Put the sieved powder in step (2) into a grinding tool for dry pressing, and then perform cold isostatic pressing with a pressure of 250MPa and a holding time of 300s to obtain a blank with a relative density of 53.4%. ;

(4) Place the green body obtained in step (3) for sintering in a vacuum furnace, raise the temperature to a sintering temperature of 1300°C at a rate of 5°C/min, hold the temperature for 18 hours, and sintering vacuum degree of 10 ^-3 Pa. After sintering is completed, the temperature is increased to 5 The rate is reduced to room temperature at a rate of ℃/min to obtain fluorescent ceramics;

(5) Anneal the fluorescent ceramic obtained in step (4) in a reducing atmosphere of 15% H ₂ : 85% N ₂ at an annealing temperature of 1150°C and a holding time of 15 hours to obtain the final required sample.

The XRD measured on the fluorescent material of (Sr _0.99 Eu _0.01 ) ₃ (Al _0.7 Sc _0.3 ) ₂ Si ₃ O ₁₂ obtained in this example is compared with the crystal phase of Sr ₃ Al ₂ Si ₃ O ₁₂ . The generation of impurity peaks indicates that doping ions have completely entered the crystal lattice. As shown in Figure 1; the excitation spectrum of the provided fluorescent material is between 350nm and 550nm; it emits red light under blue light excitation, and the emission wavelength range is between 550nm and 750nm.

Example 3: Preparation of a red fluorescent material with a chemical formula of (Sr _0.97 Eu _0.03 ) ₃ (Al _0.5 Sc _0.5 ) ₂ Si ₃ O ₁₂ .

(1) Set the target product mass to 20g. According to the stoichiometric ratio of each element of the chemical formula (Sr _0.97 Eu _0.03 ) ₃ (Al _0.5 Sc _0.5 ) ₂ Si ₃ O ₁₂ , weigh silica (4.090g) and oxidation respectively. Aluminum (2.314g), strontium carbonate (9.748g), europium oxide (0.719g) and scandium oxide (3.129g) are used as raw material powders, and boric acid (0.6g), which is 3% of the total mass of the raw material powders, is added as a sintering aid. , Mix the raw material powder with 60mL of absolute ethanol, and conduct ball milling in a ball milling tank. The ball milling speed is 200r/min and the ball milling time is 20h;

(2) Dry the mixed slurry obtained in step (1) in a drying oven at 80°C for 30 hours, and then sieve the dried mixed powder through an 80-mesh screen;

(3) Put the sieved powder in step (2) into a grinding tool for dry pressing, and then perform cold isostatic pressing with a pressure of 300MPa and a holding time of 400s to obtain a blank with a relative density of 55.0%. ;

(4) Place the blank obtained in step (3) for sintering in a vacuum furnace, raise the temperature to a sintering temperature of 1400°C at a rate of 10°C/min, hold the temperature for 24 hours, and use a sintering vacuum degree of 10 ^-3 Pa. After sintering is completed, the temperature is increased to 10 The rate is reduced to room temperature at a rate of ℃/min to obtain fluorescent ceramics;

(5) Anneal the fluorescent ceramic obtained in step (4) in a reducing atmosphere of 20% H ₂ : 80% N ₂ at an annealing temperature of 1200°C and a holding time of 24 hours to obtain the final required sample.

The XRD measured for the fluorescent material of (Sr _0.97 Eu _0.03 ) ₃ (Al _0.5 Sc _0.5 ) ₂ Si ₃ O ₁₂ obtained in this example has no impurity peaks compared with the crystal phase of Sr ₃ Al ₂ Si ₃ O ₁₂ . This indicates that the doping ions have completely entered the crystal lattice. As shown in Figure 1; the excitation spectrum of the provided fluorescent material is between 350nm and 550nm, as shown in Figure 2; it emits red light under the excitation of 450nm blue light, and the emission wavelength range is between 550nm and 750nm, as shown in Figure 3.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field shall, within the technical scope disclosed in the present invention, be within the spirit and principles of the present invention. Any modifications, equivalent substitutions and improvements made within the above shall be included in the protection scope of the present invention.

Claims (7)

1. A garnet-based red fluorescent ceramic for high power illumination, characterized in that the red fluorescent ceramic has the chemical composition:

(Sr _1-x Eu _x ) ₃ (Al _1-y Sc _y ) ₂ Si ₃ O ₁₂

wherein x is Eu ²⁺ Sr doped ³⁺ Mole percent of bits, y is Sc ³⁺ Doping Al ³⁺ The mole percentage of the position is more than or equal to 0.002 and less than or equal to 0.03,0.1 and less than or equal to 0.5.

2. A method for preparing the garnet-based red fluorescent ceramic for high-power illumination according to claim 1, which is characterized by comprising the following steps:

(1) (1) according to formula (Sr) _1-x Eu _x ) ₃ (Al _1-y Sc _y ) ₂ Si ₃ O ₁₂ Respectively weighing silicon dioxide, aluminum oxide, strontium carbonate and europium oxide as raw material powder according to the stoichiometric ratio of each element, adding a sintering aid boric acid and a ball milling medium, and carrying out mixed ball milling to obtain mixed slurry; wherein x is Eu ²⁺ Sr doped ³⁺ Mole percent of bits, y is Sc ³⁺ Doping Al ³⁺ The mole percentage of the position is 0.002.ltoreq.x.ltoreq. 0.03,0.1.ltoreq.y.ltoreq.0.5;

(2) Drying the mixed slurry obtained in the step (1) in a drying oven, and sieving the dried mixed powder;

(3) Putting the powder sieved in the step (2) into a grinding tool for dry press molding, and then performing cold isostatic pressing molding to obtain a biscuit with the relative density of 50-55%;

(4) Sintering the biscuit obtained in the step (3) in a vacuum furnace at 1200-1400 ℃ for 10-24 h with the sintering vacuum degree not lower than 10 ^-3 Pa, obtaining fluorescent ceramics;

(5) And (3) annealing the fluorescent ceramic obtained in the step (4) in a reducing atmosphere, wherein the annealing temperature is 1050-1200 ℃, and the heat preservation time is 8-24 hours, so that the red fluorescent ceramic is obtained.

3. The method for preparing the garnet-based red fluorescent ceramic for high-power illumination according to claim 2, wherein the adding amount of the boric acid in the step (1) is 1-3% of the total mass of the raw material powder; the ball milling rotating speed is 160-200 r/min, and the ball milling time is 15-20 h.

4. The method for preparing a garnet-based red fluorescent ceramic for high-power illumination according to claim 2, wherein the drying time in step (2) is 20 to 30 hours and the drying temperature is 80 to 90 ℃.

5. The method for preparing a garnet-based red fluorescent ceramic for high power illumination according to claim 2, wherein the cold isostatic pressing dwell pressure in step (3) is 150 to 300Mpa and dwell time is 200 to 400s.

6. The method for preparing the garnet-based red fluorescent ceramic for high-power illumination according to claim 2, wherein the heating rate in the vacuum sintering stage in the step (4) is 2-10 ℃/min, and the cooling rate after sintering is 2-10 ℃/min.

7. The method for preparing garnet-based red fluorescent ceramic for high power illumination according to claim 2, wherein the reducing atmosphere in step (5) is 10 to 20% h ₂ With 80 to 90 percent of N ₂ Is a mixed gas of (a) and (b).