WO2019169868A1 - Fluorescent ceramic and preparation method therefor - Google Patents

Abstract

A fluorescent ceramic and a preparation method therefor, the fluorescent ceramic comprising a MgO·nAl2O3 matrix (100) and fluorescent particles (200) distributed in the MgO·nAl2O3 matrix; the molar ratio of Al2O3 to MgO in the MgO·nAl2O3matrix is 1: n, wherein 0.9 ≤ n < 1, or, 1 < n ≤ 2. The fluorescent particles are encapsulated at the interior of the MgO·nAl2O3 ceramic by means of secondary sintering.

Description

Fluorescent ceramic and preparation method thereof Technical field

The invention relates to a fluorescent ceramic and a preparation method thereof, and belongs to the technical field of fluorescent ceramic manufacturing.

Background technique

The laser illumination display technology mainly converts the blue laser into other wavelength light through a fluorescent material, thereby obtaining white light. With the continuous development of laser display and illumination technology, the requirements for fluorescent materials are more stringent. Fluorescent materials need to meet the requirements of high luminance, high light conversion efficiency, high power laser excitation and high thermal conductivity.

Nowadays, common fluorescent materials are mostly prepared by encapsulating fluorescent particles with organic silica gel, organic resin or inorganic glass. In the process of exciting the fluorescent material, the blue laser generates a large amount of heat in addition to the visible light of other wavelengths. If the thermal conductivity of the fluorescent material is poor, under the excitation of the high-power blue laser, the fluorescent particles will cause instability of the light conversion efficiency due to the temperature rise, thereby causing a series of problems such as low luminance. The above fluorescent materials all have the problem of relatively poor thermal conductivity. Therefore, the further development of laser illumination display technology requires a fluorescent material with high thermal conductivity.

Summary of the invention

The technical problem to be solved by the present invention is to provide a fluorescent ceramic and a preparation method thereof by using a secondary sintering to prepare a MgO·nAl ₂ O ₃ ceramic in which fluorescent particles are encapsulated, wherein 0.9≤ n<1 or 1<n≤2, which improves the sintering performance of the fluorescent ceramics, facilitates the densification of the ceramics, reduces the number of pores in the fluorescent ceramics, reduces the scattering of visible light by the fluorescent ceramics, and makes the fluorescent particles more capable. Stable, fluorescent particles do not exhibit degradation due to excessive temperature.

The technical problem to be solved by the present invention is achieved by the following technical solutions:

The present invention provides a fluorescent ceramic comprising a MgO·nAl ₂ O ₃ matrix and fluorescent particles distributed in a MgO·nAl ₂ O ₃ matrix, the Al ₂ O ₃ and the MgO·nAl ₂ O ₃ matrix The molar ratio of MgO is 1:n; wherein 0.9≤n<1, or 1<n≤2.

Specifically, the MgO·nAl ₂ O ₃ matrix is a MgO·nAl ₂ O ₃ ceramic. The fluorescent particles are YAG:Ce fluorescent particles.

Preferably, the fluorescent particles have an average particle diameter of from 5 μm to 40 μm.

In order to ensure the light effect and densification of the fluorescent ceramic, the content of the fluorescent particles in the fluorescent ceramic is 20% by weight to 80% by weight.

In order to promote the densification of the fluorescent ceramic, the fluorescent ceramic further includes a sintering aid, and the sintering aid is a composite doping of one or more of lithium fluoride, calcium fluoride and cerium oxide.

Preferably, the range of n is: 0.9 ≤ n < 1, or, 1 < n ≤ 1.5.

The invention also provides a preparation method of a fluorescent ceramic, comprising the following steps:

S10: preparing a MgO·nAl ₂ O ₃ ceramic precursor powder, the molar ratio of Al ₂ O ₃ powder to MgO powder is 1:n, wherein 0.9≤n<1, or 1<n≤2;

S20: mixing the MgO·nAl ₂ O ₃ ceramic precursor powder with the fluorescent particles to form a fluorescent ceramic powder; S30: pressing the fluorescent ceramic powder into the formed green body; S40: removing the green body; S50: cold isostatic pressing After the rubber is discharged; S60: hot pressing the cold isostatic pressed green body to form a fluorescent ceramic; S70: high temperature annealing fluorescent ceramic.

The S10 is specifically: ball milling the Al ₂ O ₃ powder and the MgO powder together with the ball milling medium, drying, grinding, sieving and calcining the ball milled powder, and ball milling and baking the calcined powder and the ball milling medium. After drying and sieving, MgO·nAl ₂ O ₃ ceramic precursor powder is obtained.

The S20 is specifically: the MgO·nAl ₂ O ₃ ceramic precursor powder, the fluorescent particles, the sintering aid and the binder are ball-milled, and after ball milling, vacuum drying is performed at 50° C.-80° C., and the sieve is ground. After that, a fluorescent ceramic powder is obtained.

In summary, the present invention uses a secondary sintering to prepare a MgO·nAl ₂ O ₃ ceramic in which fluorescent particles are encapsulated, wherein 0.9≤n<1 or 1<n≤2, so that the sintering performance of the fluorescent ceramic is somewhat The improvement is beneficial to the densification of the ceramic, the number of pores in the fluorescent ceramic is reduced, the scattering of visible light by the fluorescent ceramic is reduced, the performance of the fluorescent particles is more stable, and the fluorescent particles do not exhibit degradation due to excessive temperature.

The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

DRAWINGS

Figure 1 is a schematic view showing the structure of a fluorescent ceramic of the present invention.

Detailed ways

Figure 1 is a schematic view showing the structure of a fluorescent ceramic of the present invention. As shown in FIG. 1, the present invention provides a fluorescent ceramic comprising a MgO.nAl ₂ O ₃ matrix 100 and fluorescent particles 200 distributed in a MgO·nAl ₂ O ₃ matrix, the MgO·nAl ₂ O ₃ The molar ratio of Al ₂ O _{3 to} MgO in the matrix 100 is 1:n; wherein 0.9≤n<1, or 1<n≤2.

The fluorescent particles 200 may be made of existing fluorescent particles such as YAG:Ce fluorescent particles or the like.

In the present invention, the MgO·nAl ₂ O ₃ matrix 100 is a MgO·nAl ₂ O ₃ ceramic which is different from the common magnesium aluminum spinel, wherein n is not 1, and as such, the MgO·nAl ₂ O ₃ ceramics are still Is a spinel structure, but due to the change of the ratio, two different valence cations in the MgO·nAl ₂ O ₃ ceramic form a partial cationic vacancy defect in order to satisfy the charge balance, that is, the MgO·nAl ₂ O _{3 of the} present invention. The structure of the matrix 100 is such that part of MgO or Al ₂ O _{3 is} dissolved in the magnesium aluminum spinel. The defect will inevitably lead to change their properties, such as improved sintering properties, and these changes are more conducive to MgO · nAl ₂ O ₃ ceramic densification, reducing the number of MgO · nAl ₂ O ₃ in the ceramic pores is reduced Scattering of visible light by ceramic MgO·nAl ₂ O ₃ . Conventional ceramics have relatively low light transmittance in the visible short-wavelength range and relatively high wavelength in the long-wavelength range. Low-wavelength transmittance will affect the transmission of blue light and reduce the absorption of blue light by fluorescent particles, thereby reducing The blue light conversion efficiency, while the MgO·nAl ₂ O ₃ ceramics have a more uniform transmittance throughout the visible light band.

In addition, MgO·nAl ₂ O ₃ ceramics have the same excellent optical properties as sapphire and quartz glass, and have high optical transmittance, and have chemical stability compared with conventional silica gel and glass. Meanwhile, MgO· nAl ₂ O ₃ has higher thermal conductivity than organic silica gel and organic resin, and can better conduct heat generated by fluorescent particles under blue laser excitation, so that the performance of fluorescent particles is more stable, and fluorescent particles do not cause The phenomenon that the temperature is too high and the performance is degraded.

The MgO · nAl ₂ O ₃ by the ceramic sintered Al ₂ O ₃ powder and MgO powder form wherein the average particle size of Al ₂ O ₃ powder and MgO powder is 0.05μm-1μm. Preferably, the secondary sintering method is adopted, that is, the Al ₂ O ₃ powder and the MgO powder are first prepared into a MgO·nAl ₂ O ₃ ceramic precursor powder, and then the MgO·nAl ₂ O ₃ ceramic precursor powder and the fluorescent particles are further prepared. After being mixed into a fluorescent ceramic powder, the average particle diameter of the MgO·nAl ₂ O ₃ ceramic precursor powder is 0.1 μm to 10 μm, the average particle diameter of the fluorescent particles is 5 μm to 40 μm, and the content of the fluorescent particles in the fluorescent ceramic is 20 wt. %-80wt%.

Further, the fluorescent ceramic powder further comprises a sintering aid and a binder, the content of the binder in the fluorescent ceramic is 0.5 wt% to 5 wt%, and the content of the sintering aid in the fluorescent ceramic is 0.05 wt%. -1wt%.

The invention also provides a preparation method of the above fluorescent ceramic, comprising the following steps:

S10: preparing a MgO·nAl ₂ O ₃ ceramic precursor powder, the molar ratio of Al ₂ O ₃ powder to MgO powder is 1:n, wherein 0.9≤n<1, or 1<n≤2;

S20: mixing the MgO·nAl ₂ O ₃ ceramic precursor powder with the fluorescent particles to form a fluorescent ceramic powder;

S30: pressing the fluorescent ceramic powder into a shaped green body;

S40: the green body is discharged;

S50: a blank after cold isostatic pressing;

S60: cold pressing the isostatically pressed green body to form a fluorescent ceramic.

Further, in order to remove residual carbon during the hot press sintering process, after the S60, the fluorescent ceramic may be annealed, that is, after S60, there is also S70: high temperature annealed fluorescent ceramic.

Specifically, in S10, the average particle diameter of the Al ₂ O ₃ powder and the MgO powder is 0.05 μm to 1 μm. First, the Al ₂ O ₃ powder and the MgO powder are ball-milled with a ball milling medium (anhydrous ethanol), and the ball-milled powder is dried, ground, and sieved, and then the powder is calcined in a muffle furnace, and the calcination temperature is performed. The temperature is from 1000 ° C to 1300 ° C, the holding time is from 1 h to 8 h, and the calcined powder and the ball milling medium (anhydrous ethanol) are ball milled, dried and sieved to obtain a MgO·nAl ₂ O ₃ ceramic precursor powder. The average particle diameter of the ball-milled MgO·nAl ₂ O ₃ ceramic precursor powder is from 0.1 μm to 10 μm.

It should be noted that, when tested, when n<0.9 or n>2, a second phase will be precipitated in the ceramic during calcination: MgO or Al ₂ O ₃ , and the second phase will scatter and absorb light, affecting Transparency of ceramics.

In S20, the prepared MgO·nAl ₂ O ₃ ceramic precursor powder, the fluorescent particles, the sintering aid and the binder are ball-milled and mixed, wherein the content of the fluorescent particles in the fluorescent ceramic is 20% by weight to 80% by weight, and the viscosity is The content of the binder is from 0.5% by weight to 5% by weight, and the content of the sintering aid is from 0.05% by weight to 1% by weight. It has been experimentally found that when the content of the fluorescent particles is less than 20% by weight, less fluorescent particles can be excited and the light effect is poor; and when the content of the fluorescent particles is >80% by weight, the ceramic is difficult to be densified. Preferably, the ball milling time is from 20 min to 90 min. Specifically, the fluorescent particles are YAG:Ce fluorescent particles having an average particle diameter of 5 μm to 40 μm; and the sintering aid has an average particle diameter of 0.05 μm to 1 μm, which is lithium fluoride, calcium fluoride, One or more composite dopings in cerium oxide; the binder is a solution of polyvinyl butyral (PVB) in ethanol. The ball-milled fluorescent ceramic powder is vacuum dried at 50 ° C to 80 ° C and sieved to obtain a fluorescent ceramic powder.

In S30, the dried fluorescent ceramic powder is weighed and weighed to a predetermined shape, and the molding pressure is 40 MPa to 100 MPa. The certain amount and certain shape can be selected by those skilled in the art according to actual needs, and the invention is not limited.

In S40, the glue is specifically placed in a muffle furnace at 400 ° C -600 ° C for 1 h - 4 h, 800 ° C - 1200 ° C for 1 h - 6 h.

In S50, the above-mentioned green body is cold isostatically pressed at 150 MPa to 300 MPa to further increase the relative bulk density of the ceramic.

In S60, the cold isostatically pressed green body is subjected to hot press sintering, wherein the sintering temperature is 1400 ° C - 1700 ° C, the holding time is 1 h - 4 h, and the pressure is 20 MPa - 100 MPa. It should be noted that, during the sintering process, the fluorescent particles do not react with MgO·nAl ₂ O ₃ , and the sintering process is specifically coating the fluorescent particles during sintering of MgO·nAl ₂ O ₃ into porcelain.

In S70, the annealing temperature is 1200 ° C - 1400 ° C, and the annealing time is 5 h - 20 h.

The method for preparing the MgO·nAl ₂ O ₃ ceramic precursor powder by adding the sintering aid and the hot pressing sintering method greatly reduces the sintering temperature and the density of the MgO·nAl ₂ O ₃ ceramic. Specifically, the secondary sintering method of the present invention can greatly increase the density of the fluorescent ceramic: the MgO·nAl ₂ O ₃ ceramic precursor powder 100 is prepared in advance, and then sintered into porcelain, which is formed by the reaction of aluminum oxide and magnesium oxide. In the process of MgO·nAl ₂ O ₃ , the change of powder density is large, which is not conducive to ceramic densification. Secondary sintering can solve this problem, and at the same time, the uniformity of ceramic powder can be improved, and hot press sintering can make ceramic reach its Theoretical density.

The fluorescent ceramics and the preparation method thereof are further described below in conjunction with specific embodiments.

Embodiment 1

High-purity nano-scale alumina powder and magnesia powder are selected, both of which have a purity of more than 99%. The two are poured into a ball mill tank together with the ball mill medium anhydrous ethanol, wherein the molar ratio of alumina powder to magnesium oxide powder is 1:1.1, a high-purity alumina ball was selected for ball milling, and the ball milling time was 8 h. After drying, grinding and sieving, the powder was calcined in a muffle furnace at 1200 ° C for 2 h; the calcined powder was further subjected to 24 h. The ball was ground to an average particle size of 4 μm and bottled for use. It can be understood that the ball milling medium can also be a common ball milling medium such as stearic acid, cetane, dodecane, methanol, n-butanol, ethylene glycol, isopropanol, water, carbon tetrachloride and N-methylpyrrolidone. Any one or combination of them.

Weigh a certain amount of YAG:Ce fluorescent particles, which account for 50wt% of the fluorescent ceramics, and add a 2% concentration of PVB ethanol solution, which accounts for 2wt% of the fluorescent ceramics. The nano-fluorinated lithium is selected as a sintering aid, and its purity is 99% or more, which accounts for 0.5wt% of the fluorescent ceramics; YAG:Ce fluorescent particles, MgO·1.1Al ₂ O ₃ ceramic powder, sintering aid, PVB ethanol solution are ball milled for 1 hour, and then vacuum dried at 60 ° C Then, it is ground, sieved, and bottled for use.

The fluorescent ceramic powder was pressed into a pellet under a pressure of 80 MPa. Then, the formed green body is subjected to a debinding process, and the debinding process is performed at 500 ° C for 2 h and at 900 ° C for 4 h. After the glue is discharged, cold isostatic pressing treatment is performed under a pressure of 200 MPa to reduce the pores between the ceramic aggregates in the green body.

The green body was placed in a hot press sintering furnace under a argon atmosphere at a pressure of 50 MPa and sintered at 1700 ° C for 2 h. After hot pressing and sintering, the ceramic was annealed at 1300 ° C for 10 h in an air atmosphere; finally, the ceramic was subjected to coarse grinding, fine grinding and polishing to obtain YAG-MgO·1.1Al ₂ O ₃ fluorescent ceramic.

YAG-MgO·Al ₂ O ₃ fluorescent ceramics with a molar ratio of MgO and Al ₂ O ₃ of 1:1.0 were prepared by the same process; the relative bulk density of the two luminescent ceramics was determined by Archimedes drainage method, and simultaneously The light effect is tested, and the light effect in the present invention specifically refers to the fluorescence excited by the blue laser per watt. The test results are shown in Table 1. It can be seen from the results that the MgO·1.1Al ₂ O ₃ luminescent ceramics are better in both density and luminous efficiency.

Table 1

Embodiment 2

High-purity nano-scale alumina powder and magnesia powder are selected, both of which have a purity of more than 99%; the two are poured into a ball-milling tank together with the ball mill medium anhydrous ethanol, wherein the molar ratio of alumina powder to magnesium oxide powder is 1:1.3; High-purity alumina ball was selected for ball milling, ball milling time was 6h. After drying, grinding and sieving treatment, the powder was calcined in a muffle furnace at 1100 ° C for 3 h; the calcined powder was further subjected to 24 h. The ball was ground to an average particle size of 5 μm and bottled for use.

Weigh a certain amount of YAG:Ce fluorescent particles, which account for 30wt% of the fluorescent ceramics, and add a concentration of 3% of PVB ethanol solution, which accounts for 3wt% of the fluorescent ceramics; and select nano-lithium fluoride as a sintering aid, the purity of which is 99% or more, which accounts for 0.5wt% of the fluorescent ceramics; the YAG:Ce fluorescent particles, the MgO·1.3Al ₂ O ₃ ceramic powder, the sintering aid, and the PVB ethanol solution are ball milled for 40 minutes, and then vacuum dried at 80 ° C. Then, it is ground, sieved, and bottled for use.

The fluorescent ceramic powder was pressed into a pellet under a pressure of 60 MPa. Then, the formed green body is subjected to debinding treatment, and the debinding process is kept at 600 ° C for 3 h and at 1000 ° C for 6 h. After the glue is discharged, cold isostatic pressing treatment is performed under a pressure of 300 MPa to reduce the pores between the ceramic aggregates in the green body.

The green body was placed in a hot press sintering furnace under a argon atmosphere at a pressure of 80 MPa and sintered at 1650 ° C for 3 hours. After hot pressing and sintering, the ceramic is annealed at 1350 ° C for 15 h in an air atmosphere; finally, the ceramic is subjected to coarse grinding, fine grinding and polishing to obtain YAG-MgO·1.3Al ₂ O ₃ fluorescent ceramic.

YAG-MgO·Al ₂ O ₃ fluorescent ceramics with a molar ratio of MgO and Al ₂ O ₃ of 1:1.0 were prepared by the same process; the relative bulk density of the two luminescent ceramics was determined by Archimedes drainage method, and simultaneously The light effect is tested, and the light effect in the present invention specifically refers to the fluorescence excited by the blue laser per watt. The test results are shown in Table 2. It can be seen from the results that the MgO·1.3Al ₂ O ₃ luminescent ceramics have good density and luminous efficiency.

Table 2

Embodiment 3

High-purity nano-scale alumina powder and magnesia powder are selected, both of which have a purity of more than 99%; the two are poured into a ball-milling tank together with the ball mill medium anhydrous ethanol, wherein the molar ratio of alumina powder to magnesium oxide powder is 1:1.5; High-purity alumina ball was selected for ball milling, ball milling time was 5h. After drying, grinding and sieving treatment, the powder was calcined in a muffle furnace at 1000 ° C for 4 h; the calcined powder was further subjected to 24 h. The ball was ground to an average particle size of 5 μm and bottled for use.

Weigh a certain amount of YAG:Ce fluorescent particles, which account for 60wt% of the fluorescent ceramics, and add a concentration of 3% PVB ethanol solution, which accounts for 4wt% of the fluorescent ceramics; YAG:Ce fluorescent particles, MgO·1.5Al ₂ O ₃ ceramic powder, PVB ethanol solution ball milling for 60min, vacuum drying at 80 ° C, then grinding, sieving treatment, bottling for use.

The fluorescent ceramic powder was pressed into a pellet under a pressure of 80 MPa. Then, the formed green body is subjected to debinding treatment, and the debinding process is 550 ° C for 3 h, and 950 ° C for 6 h. After the glue is discharged, cold isostatic pressing treatment is performed under a pressure of 250 MPa to reduce the pores between the ceramic aggregates in the green body.

The green body was placed in a hot press sintering furnace under a argon atmosphere at a pressure of 100 MPa and sintered at 1600 ° C for 2 h. After hot pressing and sintering, the ceramic is annealed at 1300 ° C for 20 h in an air atmosphere; finally, the ceramic is subjected to coarse grinding, fine grinding and polishing to obtain YAG-MgO·1.5Al ₂ O ₃ fluorescent ceramic.

YAG-MgO·Al ₂ O ₃ fluorescent ceramics with a molar ratio of MgO and Al ₂ O ₃ of 1:1.0 were prepared by the same process; the relative bulk density of the two luminescent ceramics was determined by Archimedes drainage method, and simultaneously The light effect is tested, and the light effect in the present invention specifically refers to the fluorescence excited by the blue laser per watt. The test results are shown in Table 3. From the results, it can be seen that the MgO·1.5Al ₂ O ₃ luminescent ceramics have good density and luminous efficiency.

table 3

Embodiment 4

High-purity nano-scale alumina powder and magnesia powder are selected, both of which have a purity of more than 99%; the two are poured into a ball-milling tank together with the ball mill medium anhydrous ethanol, wherein the molar ratio of alumina powder to magnesium oxide powder is 1:0.9; High-purity alumina ball was selected for ball milling, the ball milling time was 5h. After drying, grinding and sieving, the powder was calcined in a muffle furnace at 1100 ° C for 3 h; the calcined powder was further subjected to 24 h. The ball was ground to an average particle size of 5 μm and bottled for use.

Weigh a certain amount of YAG:Ce fluorescent particles, which account for 50wt% of the fluorescent ceramics, and add a 2% concentration of PVB ethanol solution, which accounts for 3wt% of the fluorescent ceramics; YAG:Ce fluorescent particles, MgO·0.9Al ₂ O ₃ ceramic powder, PVB ethanol solution ball milling for 40min, vacuum drying at 80 ° C, then grinding, sieving treatment, bottling for use.

The fluorescent ceramic powder was pressed into a pellet under a pressure of 80 MPa. Then, the formed green body is subjected to a debinding process, and the debinding process is performed at 500 ° C for 2 h and at 900 ° C for 6 h. After the glue is discharged, cold isostatic pressing treatment is performed under a pressure of 200 MPa to reduce the pores between the ceramic aggregates in the green body.

The green body was placed in a hot press sintering furnace under a argon atmosphere at a pressure of 100 MPa and sintered at 1650 ° C for 2 h. After hot pressing sintering, the fluorescent ceramics were annealed at 1250 ° C for 20 h in an air atmosphere; finally, the ceramic was subjected to coarse grinding, fine grinding and polishing to obtain YAG-MgO·0.9Al ₂ O ₃ fluorescent ceramics.

YAG-MgO·Al ₂ O ₃ fluorescent ceramics with a molar ratio of MgO and Al ₂ O ₃ of 1:1.0 were prepared by the same process; the relative bulk density of the two luminescent ceramics was determined by Archimedes drainage method, and simultaneously The light effect is tested, and the light effect in the present invention specifically refers to the fluorescence excited by the blue laser per watt. The test results are shown in Table 4. From the results, it can be seen that the MgO·0.9Al ₂ O ₃ luminescent ceramics have relatively good density and luminous efficiency.

Table 4

In summary, the present invention uses a secondary sintering to prepare a MgO·nAl ₂ O ₃ ceramic in which fluorescent particles are encapsulated, wherein 0.9≤n<1 or 1<n≤2, so that the sintering performance of the fluorescent ceramic is somewhat The improvement is beneficial to the densification of the ceramic, the number of pores in the fluorescent ceramic is reduced, the scattering of visible light by the fluorescent ceramic is reduced, the performance of the fluorescent particles is more stable, and the fluorescent particles do not exhibit degradation due to excessive temperature.

Claims (10)

1. A fluorescent ceramic, characterized in that the fluorescent ceramic comprises a MgO·nAl ₂ O ₃ matrix (100) and fluorescent particles (200) distributed in a MgO·nAl ₂ O ₃ matrix, the MgO·nAl ₂ O ₃ The molar ratio of Al ₂ O _{3 to} MgO in the matrix is 1:n; wherein 0.9≤n<1, or 1<n≤2.
2. The fluorescent ceramic according to claim 1, wherein the MgO·nAl ₂ O ₃ matrix (210) is a MgO·nAl ₂ O ₃ ceramic.
3. The fluorescent ceramic according to claim 1, wherein the fluorescent particles are YAG:Ce fluorescent particles.
4. The fluorescent ceramic according to claim 1, wherein the fluorescent particles have an average particle diameter of from 5 μm to 40 μm.
5. The fluorescent ceramic according to claim 1, wherein the fluorescent ceramics have a content of fluorescent particles of from 20% by weight to 80% by weight.
6. The fluorescent ceramic according to claim 1, wherein the fluorescent ceramic further comprises a sintering aid, and the sintering aid is one or more of lithium fluoride, calcium fluoride and cerium oxide. .
7. The fluorescent ceramic according to claim 1, wherein the range of n is 0.9 ≤ n < 1, or 1 < n ≤ 1.5.
8. A method for preparing a fluorescent ceramic, characterized in that the preparation method comprises the following steps:

   S10: preparing a MgO·nAl ₂ O ₃ ceramic precursor powder, the molar ratio of Al ₂ O ₃ powder to MgO powder is 1:n, wherein 0.9≤n<1, or 1<n≤2;

   S20: mixing the MgO·nAl ₂ O ₃ ceramic precursor powder with the fluorescent particles to form a fluorescent ceramic powder;

   S30: pressing the fluorescent ceramic powder into a shaped green body;

   S40: the green body is discharged;

   S50: a blank after cold isostatic pressing;

   S60: hot pressing the cold isostatically pressed green body to form a fluorescent ceramic;

   S70: High temperature annealed fluorescent ceramics.
9. The preparation method according to claim 8, wherein the S10 is specifically: ball milling the Al ₂ O ₃ powder and the MgO powder together with the ball milling medium, and drying, grinding, sieving, and calcining the ball-milled powder. The calcined powder and the ball milling medium are ball milled, dried, and sieved to obtain a MgO·nAl ₂ O ₃ ceramic precursor powder.
10. The preparation method according to claim 8, wherein the S20 is specifically: ball milling and mixing the MgO·nAl ₂ O ₃ ceramic precursor powder, fluorescent particles, sintering aid and binder, after ball milling Vacuum drying was carried out at 50 ° C to 80 ° C, and after sieving, a fluorescent ceramic powder was obtained.

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