CN112979313A - Fluorescent ceramic and preparation method thereof - Google Patents

Abstract

The application discloses a fluorescent ceramic and a preparation method thereof, wherein the fluorescent ceramic is selected from at least one of substances in a chemical formula shown in a formula I. The fluorescent ceramic has excellent luminous thermal stability and mechanical property, and solves the problem of low color rendering index caused by the reduction of green light intensity at high temperature, so that a light source with higher brightness and more stable color quality is obtained.

Description

Fluorescent ceramic and preparation method thereof

Technical Field

The application relates to a fluorescent ceramic and a preparation method thereof, belonging to the technical field of functional ceramics.

Background

The fluorescent ceramic is an advanced luminescent material with high luminous efficiency, long service life, high temperature resistance and small volume under the excitation of high-power blue light sources such as laser, LED and the like, has excellent optical performance and stable chemical and mechanical properties, and can be widely applied to the fields of infrared, illumination, indication, display and the like. After a large number of people are tested according to the photometric sampling of the international commission on illumination, the drawn photopic curve shows that human eyes are most sensitive to green light wave bands, so that the preparation of the efficient green light fluorescent material is very important in the field of advanced display materials. The method is not only beneficial to improving the overall brightness of the picture, but also has important significance for improving the color quality by taking the green light as the three primary colors. In addition, especially for a laser display projector, the fluorescent wheel is used as a core light conversion device, the high-temperature luminescence stability of the fluorescent wheel is especially important, the high-temperature quenching performance is a great advantage of fluorescent ceramics, and the fluorescent wheel is expected to replace traditional materials such as fluorescent powder and the like. Meanwhile, annular fluorescent ceramic is needed during packaging and use, most of the actually prepared fluorescent ceramic is in a shape of a circular sheet, and a large part of materials are cut off during processing and cannot be utilized. Therefore, it is urgently needed to develop an advanced forming process and sintering approach to realize one-step forming and sintering preparation of the annular fluorescent ceramic, so as to improve the production efficiency and reduce the preparation cost of the fluorescent ceramic.

Disclosure of Invention

According to one aspect of the present application, a fluorescent ceramic is provided, which can be excited by a blue light emitting laser and an LED, can convert blue light into green light, and can be used as a fluorescent conversion material for a high-brightness, high-color-rendering, high-power large-screen display device. Can meet the continuous and stable use at high temperature, and can greatly improve the service life of the display equipment.

A fluorescent ceramic, wherein the fluorescent ceramic is at least one selected from substances in a chemical formula shown in a formula I;

Y_3-x-yLu_xCe_yAl₄GaO₁₂formula I

Wherein the value range of x is more than or equal to 0.01 and less than 3;

the value range of y is more than or equal to 0.0005 and less than or equal to 0.1.

Specifically, the application provides a fluorescent ceramic material capable of emitting green light.

Preferably, the value range of x is more than or equal to 0.3 and less than or equal to 1.5; the value range of y is more than or equal to 0.005 and less than or equal to 0.09.

Optionally, the fluorescent ceramic is a polycrystalline luminescent material with a garnet structure, and belongs to the cubic system, Ia3d space group.

Specifically, the fluorescent ceramic material is of a garnet structure, belongs to a cubic crystal system, and has a space group Ia3 d.

Optionally, the microstructure of the fluorescent ceramic is fully densified to form a single phase, and the number of pores inside and between grains is 0.

In particular, the microstructure of the fluorescent ceramics in the present application is capable of forming a fully densified, pore-free and secondary phase within and between the grains.

Optionally, the grain size of the fluorescent ceramic is 0.5-15 μm.

Optionally, the emission spectrum range of the fluorescent ceramic is 510-580 nm.

Specifically, the excitation wavelength of the fluorescent ceramic material is 330-490nm, preferably, the excitation wavelength is 430-470nm, which can be effectively excited by blue light, and the emission wavelength range under the excitation of blue light is 510-580 nm.

Preferably, the emission spectrum range of the fluorescent ceramic is 510-530 nm.

Optionally, the fluorescent ceramic is a ring-shaped fluorescent ceramic.

Specifically, the spectrum of the fluorescent ceramic material can be adjusted by adjusting the matrix components (Lu and Ga) and the concentration of luminescent ions (mainly Ce), so that the green light emission of high efficiency 515-530nm can be achieved optionally, and the thickness of the fluorescent ceramic is 1-15 mm.

Optionally, the intensity of the emission spectrum of the fluorescent ceramic at 550k is 90% or more of the intensity of the emission spectrum at room temperature.

Optionally, the intensity of the emission spectrum of the fluorescent ceramic at 550k is 90% or more of the intensity of the emission spectrum at 293 k.

According to another aspect of the present application, there is also provided a method of preparing the fluorescent ceramic of any one of the above, comprising at least the steps of:

a) calcining a mixture containing a Y source, a Lu source, a Ce source, an Al source and a Ga source to obtain a calcined material;

b) and putting the calcined material into a mold for sintering to obtain the fluorescent ceramic.

Specifically, in step a), first, according to Y_3-x-yLu_xCe_yAl₄GaO₁₂Calculating and weighing a Y source, a Lu source, a Ce source, an Al source and a Ga source respectively, then mixing or dissolving all materials, and drying to obtain powder; then, calcining the powder, removing organic matters and residual media or solvents in the powder, and grinding and sieving the calcined powder to obtain a calcined material;

in the step b), the calcined material is loaded into a mold and then sintered to prepare the compact fluorescent ceramic, and the compact fluorescent ceramic is obtained after high temperature and high pressure, heat preservation and pressure maintaining.

In a), the material mixing method is not limited, and comprises ball milling wet mixing, chemical coprecipitation mixing, sol-gel mixing, dry grinding mixing and the like; the powder drying method is not limited, and includes microwave drying, spray drying, oven heating drying, etc.

Optionally, in step a), the Y source is selected from any one of an oxide of Y, a salt compound containing Y;

the Lu source is selected from any one of oxides of Lu and Lu-containing salt compounds;

the Ce source is selected from any one of oxides of Ce and salt compounds containing Ce;

the Al source is selected from any one of oxide of Al and salt compound containing Al;

the Ga source is selected from any one of oxides of Ga and salt compounds containing Ga.

Specifically, the Y source is selected from Y₂O₃、Y(NO₃)₂、YF₃Any one of the above.

The Lu source is selected from Lu₂O₃、Lu(NO₃)₂、LuF₃·2H₂Any one of O.

The Ce source is selected from CeO₂、Ce(OH)CO₃、CeCl₃Any one of the above.

The Al source is selected from Al₂O₃、Al(OH)₃、AlCl₃Any one of the above.

The Ga source is selected from Ga₂O₃、Ga₂(SO₄)₃、GaCl₃Any one of the above.

Optionally, in step a), the mixture has an average particle size of less than 0.5 μm.

Optionally, in step a), the average particle size of the mixture is 20-500 nm.

Alternatively, in step a), the calcination conditions are: the calcination temperature is 800-1100 ℃; the calcination time is 2-6 h.

Optionally, in step b), the sintering comprises a first sintering phase and a second sintering phase:

conditions of the first sintering stage: the temperature is 900-1400 ℃; the time is 0.5-4 h;

conditions of the second sintering stage: the temperature is 1480-1900 ℃; the time is 15min to 50 h; pressure: 50 to 200 MPa.

Preferably, the conditions of the first sintering stage: the temperature is 900-1000 ℃; the time is 2-3 h;

conditions of the second sintering stage: the temperature is 1480-1700 ℃; the time is 15min to 6 h; pressure: 50 to 200 MPa.

Specifically, the high-temperature high-pressure sintering method in the present application is not limited, and includes vacuum sintering, and H₂Sintering in a mixed gas or other reducing atmosphere, hot isostatic pressing, spark plasma sintering, hot press sintering, and the like. Preferably, hot-pressing sintering is adopted, and the sintering process is divided into two sections: firstly heating to 1000-1400 ℃, preserving heat for 0.5-4 h, then heating to 1600-1900 ℃, preserving heat for 2-50 h, and simultaneously gradually increasing the pressure to 1 x 10^-3And keeping the pressure between Pa and 300 Mpa.

Optionally, the mold comprises an upper press head, a mold cavity and a lower press head in sequence from top to bottom; the die cavity is communicated along the vertical direction, and the die cavity is detachably fixed on the lower pressure head; a central core coaxial with the die cavity is arranged in the cavity of the die cavity; the central core is detachably fixed on the lower pressure head; the lower surface of the upper pressure head is provided with a blind hole along the vertical direction, one part of the upper pressure head is inserted in the cavity, and the upper part of the central core is inserted in the blind hole; the lower pressure head, the middle core, the die cavity and the upper pressure head are enclosed to form a closed annular material cavity.

Specifically, the mould comprises an upper pressure head, a mould cavity, a middle core and a lower pressure head, the mould structure can realize one-step sintering forming (namely sintering and forming are the same process) of a hollow structure ceramic biscuit, the upper pressure head is of a hollow structure with an opening at the lower part, and is matched with the mould cavity, the middle core and the lower pressure head for use, so that a closed hollow complex structure can be formed in a surrounding mode, and the annular ceramic wafer can be obtained by applying pressure to the upper mould head and the lower mould head.

The mold can be used at the temperature of 1900 ℃ below 1000-; the mold can be used in air, oxygen, and reducing atmosphere environments.

Optionally, the mold further includes an annular mold pad, the mold pad is sleeved on the central core, an inner annular wall of the mold pad abuts against a side wall of the central core, and an outer annular wall of the mold pad abuts against an inner wall of the mold cavity.

The die pad provided by the application can ensure that the biscuit and the sintered body can be easily demoulded.

The filling method of the die is described below, firstly, the middle core is fixed on the upper surface of the lower pressing head, then the die cavity is coaxially arranged outside the middle core, the lower end of the die cavity is also fixed on the upper surface of the lower pressing head, at the moment, an annular groove with the upper end externally communicated is formed among the middle core, the die cavity and the lower pressing head, the calcined material is added into the groove, the die pad is arranged on the material, then the upper pressing head is covered on the die pad, the upper part of the middle core is inserted into the blind hole of the upper pressing head, at the moment, the middle core, the die cavity, the lower pressing head and the upper pressing head are enclosed to form an enclosed annular material cavity, and the calcined material is placed in the material cavity. And then the packaged die and the calcined material are placed into a sintering furnace to be directly sintered at high pressure and high temperature, and a compact sintered body can be obtained.

Optionally, the material of the mold is selected from at least one of mold steel, stainless steel, graphite, zirconia, alumina and agate.

Optionally, the upper and lower pressing heads and the die cavity of the die can be cubic, rectangular, polygonal and oval except for cylinders or rings, and the shapes of the upper and lower pressing heads and the die cavity are not strictly limited as long as the material cavity can be annular; the die cavity of the die can be integrated or multi-petal combined according to the actual size of the die.

Optionally, before step b), further comprising:

c) molding the calcined material;

the molding process is at least one of dry pressing molding and cold isostatic pressing molding;

the dry pressing molding comprises the step of putting the calcined material into the die for dry pressing molding.

Specifically, a ring-type ceramic biscuit can be obtained by applying pressure to the upper and lower indenters. The mould in the dry pressing process is the same as the mould in the sintering process, only the size difference between the mould and the sintering process is different, the specific size difference is not strictly limited, and the biscuit passing through the forming mould can be placed into the sintering mould.

The use method of the annular transparent ceramic forming die comprises the following steps: the mold may be uniaxially press-molded; the pressure forming can also be applied to double shafts, the structure of the lower pressure head is the same as that of the upper pressure head, the mold cavity at the moment has no open groove, and the inner diameter of the mold cavity is consistent up and down.

Optionally, the pressure for molding in the mold is 4-6 Mpa, and the molding time is 2-5 min.

Optionally, in step b), after sintering, the method further includes:

d) annealing treatment;

the annealing conditions are as follows: temperature: 900-1500 ℃; the time is 2-50 h.

Specifically, the annealing method in the present application is not limited, and includes performing in air, in a reducing atmosphere, or in an oxygen atmosphere.

Preferably, the annealing temperature is 1100-1400 ℃, the heat preservation time is preferably 2-20 h, and then the fluorescent ceramic is obtained after cooling to room temperature.

Optionally, the annealing in step d) is followed by grinding and polishing.

As a specific embodiment, the preparation method of the fluorescent ceramic comprises the following steps:

(1) according to Y_3-x-yLu_xCe_yAl₄GaO₁₂Respectively weighing Y oxide or corresponding salt, Lu oxide or corresponding salt, Ce oxide or corresponding salt, Al oxide or corresponding salt and Ga oxide or corresponding salt, then ball-milling and mixing or dissolving all the oxides or salts, and drying to obtain powder with the particle size distribution of about 100 mu m;

(2) calcining the powder, removing organic matters and residual media or solvents in the powder, and grinding and sieving the calcined powder;

(3) loading the calcined powder into a die, then carrying out the processes of molding and sintering, and carrying out high temperature and high pressure, heat preservation and pressure maintaining to obtain compact fluorescent ceramic;

(4) annealing the sample sintered at high temperature to obtain completely compact pure-phase fluorescent ceramic;

(5) and grinding and polishing the fluorescent ceramic.

The beneficial effects that this application can produce include:

1) the fluorescent ceramic provided by the application can be excited by a laser and an LED which emit blue light, can convert the blue light into green light, can be used as a fluorescent conversion material of a large-screen display device with high brightness, high color development and high power, and has 99.99% of high-density microstructure and 9-14 W.m compared with fluorescent powder^-1K^-1The fluorescent ceramic can replace the fluorescent material prepared by mixing the prior fluorescent powder and organic silica gel or epoxy resin. The material can effectively solve the problems of heat accumulation, short service life, low light efficiency, color coordinate drift and the like caused by the traditional packaging mode, and can meet the requirement of continuous and stable use (emission spectrum at 550K) at the temperature of 373KThe strength retention ratio of (1) is high, so that the material can be continuously and stably used at 373 k), and the service life of the display device is greatly prolonged.

2) Compared with the traditional fluorescent powder, the fluorescent ceramic material is an all-inorganic and densified crystalline solid solution, has excellent luminous thermal stability and mechanical property, solves the problem of low color rendering index caused by reduction of green light intensity at high temperature, and thus obtains a light source with higher brightness and more stable color quality.

3) The preparation method provided by the application can be used for directly preparing the annular fluorescent ceramic chip, greatly shortening the preparation period, improving the production efficiency and reducing the preparation cost and the processing cost.

4) The mold provided by the application can be used in the molding process and the sintering process, and is greatly convenient for the preparation process of the fluorescent ceramic annular structure.

Drawings

FIG. 1 is an exploded view of a mold in one embodiment of the present application;

FIG. 2 is a front view and a cross-sectional view of an upper ram in one embodiment of the present application;

FIG. 3 is a front view and a cross-sectional view of a mold cavity in one embodiment of the present application;

FIG. 4 is a front and cross-sectional view of a lower ram in one embodiment of the present application;

FIG. 5 is an XDR map of sample # 6;

FIG. 6 is an SEM image of sample # 3, wherein 6(a) is a surface topography SEM image and 6(b) is a cross-sectional topography SEM image;

FIG. 7 is an excitation emission spectrum of sample # 1;

FIG. 8 is an excitation emission spectrum of sample # 5;

FIG. 9(a) is a thermal quenching spectrum of sample No. 1, and FIG. 9(b) is a graph showing a change in luminescence intensity versus temperature of sample No. 1;

FIG. 10 is a graph showing the emission spectrum of sample No. 4 when excited by a laser at 450 nm.

List of parts and reference numerals:

100, an upper pressure head; 200 of a die cavity; 201 a large diameter cavity;

202 a small-diameter cavity; 300, pressing head; 301 an annular boss;

400 a core; 500 die cushion.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are used only for convenience in describing the present invention and for simplification of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Specific embodiments are described below:

a chemical formula of Y_3-x-yLu_xCe_yAl₄GaO₁₂Fluorescent ceramic, which forms a polycrystalline luminescent material of garnet phase, wherein x is more than or equal to 0.01 and less than 3, and y is more than or equal to 0.0005 and less than or equal to 0.1; preferably, 0.3. ltoreq. x.ltoreq.1.5, 0.005. ltoreq. y.ltoreq.0.09; the emission spectrum of the green light emitting diode can realize high-efficiency green light emission within the range of 510-530 nm.

Further, its microstructure is capable of forming a fully densified, pore-free and secondary phase within and between the grains.

Furthermore, the grain size of the polycrystalline structure is about 10 mu m, and the size of the polycrystalline structure is uniform.

Further, the emission spectrum intensity is maintained above 90% of room temperature at 550K.

Y_3-x-yLu_xCe_yAl₄GaO₁₂Preparation method of fluorescent ceramic sheet according to Y_3-x-yLu_xCe_yAl₄GaO₁₂Calculating and weighing corresponding raw materials according to the chemical formula composition, and mixing to obtain uniform powder slurry; respectively drying and sieving the powder slurry, calcining the powder at a certain temperature, and preparing the fluorescent ceramic by a one-step forming and sintering method; then annealing to obtain Y_3-x-yLu_xCe_yAl₄GaO₁₂Fluorescent ceramic plate.

Further, the mixing is a ball milling method, a sol-gel method, a coprecipitation method, or the like.

Further, the calcination at a certain temperature is 900 ℃, 1000 ℃ or 1200 ℃ respectively.

Furthermore, the one-step forming and sintering mainly adopts pre-forming combined with cold isostatic pressing or direct forming in the sintering process.

Further, the one-step forming and sintering mainly adopts vacuum hot pressing sintering, SPS, hot isostatic pressing and other sintering modes.

Further, the sintering atmosphere conditions comprise vacuum and H₂\N₂And an Ar atmosphere.

Further, the annealing treatment is performed in air, a reducing atmosphere, or an oxygen atmosphere.

Further, the annealing temperature is not more than 1100-1500 ℃ in the air, and the heat preservation time is not more than 50 hours, so as to eliminate the residual internal stress.

In the application, an XRD test adopts a German BRUKER-D8 ADVANCE instrument;

the SEM test adopts a Hitachi S4800 instrument;

the excitation emission spectrum test adopts a HORIBA FL3-111 instrument;

the thermal quenching test was conducted using a HORIBA FL3-111 apparatus.

The purity of the starting material used in the present application was 99.99%.

Example 1:

fluorescent ceramic piece Y_2.488Lu_0.5Ce_0.012Al₄GaO₁₂The preparation method comprises the following steps:

(1) weighing Y according to stoichiometric ratio₂O₃:16.5239g，Lu₂O₃:5.8519g，CeO₂：0.1215g，Al₂O₃:11.9954g，Ga₂O₃5.5130 g. Adding alumina balls into a grinding tank, and grinding and mixing by taking absolute ethyl alcohol as a grinding medium, wherein the ball-milling rotation speed is 350rap/min, the ball-milling time is 10 hours, and the average particle size of the obtained powder is about 300 nm;

(2) drying and sieving the obtained slurry, and calcining the sieved powder at 850 ℃ in the air for 2h to remove organic matters in the powder; sieving the obtained powder for sintering;

(3) directly putting the obtained powder into a die shown in figure 1, and sintering in a vacuum hot-pressing furnace, wherein the die structure is shown in figures 1-4; the temperature rise rate is 10 ℃/min, the temperature is kept at 900 ℃ for 3h, then the temperature is raised at the rate of 5 ℃/min, the temperature is kept at 1680 ℃ for 6h, meanwhile, the pressure is kept at 150MPa, the solid phase reaction is completed, and the densification is achieved by removing air holes;

(4) the sample after vacuum sintering is put in the air, the temperature is kept at 1400 ℃ for 6h for annealing, the obtained fluorescent ceramic is polished to obtain Y_2.488Lu_0.5Ce_0.012Al₄GaO₁₂The thickness of the fluorescent ceramic sheet is 1mm, and the fluorescent ceramic sheet is recorded as sample No. 1.

Example 2:

fluorescent ceramic piece Y_0.488Lu_2.5Ce_0.012Al₄GaO₁₂The preparation method comprises the following steps:

(1) weighing Y according to stoichiometric ratio₂O₃:2.5864g，Lu₂O₃:23.3494g，CeO₂：0.0970g，Al₂O₃:9.5724g，Ga₂O₃4.3994 g. Adding alumina balls into a grinding tank, and grinding and mixing by taking absolute ethyl alcohol as a grinding medium, wherein the ball-milling rotation speed is 300rap/min, and the ball-milling time is 12 hours until the average particle size of powder is less than 1 mu m;

(2) drying and sieving the obtained slurry, and calcining the sieved powder at 1000 ℃ in the air for 2h to remove organic matters in the powder; sieving the obtained powder and sintering;

(3) directly putting the obtained powder into a die shown in figure 1, and sintering in a Spark Plasma Sintering (SPS) furnace, wherein the die has a structure shown in figures 1-4; the temperature rise rate is 5 ℃/min, the temperature is kept at 1000 ℃ for 2h, then the temperature is raised at the rate of 2 ℃/min, the temperature is raised to 1700 ℃, the temperature is kept for 4h, the temperature is kept at 80MPa, the solid phase reaction is completed, and part of air holes are removed to achieve relative compactness;

(4) carrying out heat treatment on the ceramic obtained in the step (3) in hot isostatic pressing at 1500 ℃ and 200MPa for 2h to obtain fully densified fluorescent ceramic, and carrying out in-air annealing to obtain Y_0.488Lu_2.5Ce_0.012Al₄GaO₁₂The thickness of the fluorescent ceramic sheet was 2mm, and it was designated as sample # 2.

Example 3:

fluorescent ceramic piece Y_1.95LuCe_0.05Al₄GaO₁₂The preparation method comprises the following steps:

(1) weighing Y according to stoichiometric ratio₂O₃:12.1473g，Lu₂O₃:10.9777g，CeO₂：0.4748g，Al₂O₃:11.2512g，Ga₂O₃5.1710 g. Adding alumina balls into a grinding tank, and grinding and mixing by taking absolute ethyl alcohol as a grinding medium, wherein the ball-milling rotation speed is 350rap/min, and the ball-milling time is 10 hours until the average particle size of the powder is less than 1 mu m;

(2) drying and sieving the obtained slurry, and calcining the sieved powder at 1000 ℃ in the air for 2h to remove organic matters in the powder;

(3) sieving the obtained powder, performing with a mold designed as shown in FIG. 1, applying 4MPa pressure with a single shaft, maintaining for 2min, relieving pressure, plastic packaging, and pressing again in cold isostatic pressing equipment to obtain biscuit with pressure of 200MPa and pressure maintaining time of 5 min;

(4) sintering the obtained ceramic biscuit in a vacuum hot pressing furnace, and loading the biscuit into a mold shown in figure 1, wherein the mold has a structure shown in figures 1-4 and is slightly different from the size in the step (2) in the embodiment; the temperature rise rate is 10 ℃/min, the temperature is kept at 900 ℃ for 3h, then the temperature is raised at the rate of 2 ℃/min, the temperature is kept at 1680 ℃ for 4h, meanwhile, the pressure is kept at 200MPa, the solid phase reaction is completed, and the densification is achieved by removing air holes;

(5) the sintered sample is put in the air, the temperature is kept at 1100 ℃ for 6h for annealing, the obtained fluorescent ceramic is polished to obtain Y_1.95LuCe_0.05Al₄GaO₁₂The thickness of the fluorescent ceramic plate is 3mm, and the fluorescent ceramic plate is marked as a sample No. 3.

Example 4:

fluorescent ceramic piece Y_2.485Lu_0.5Ce_0.015Al₄GaO₁₂The preparation method comprises the following steps:

(1) weighing Y according to stoichiometric ratio₂O₃:16.5002g，Lu₂O₃:5.8506g，CeO₂：0.1518g，Al₂O₃:11.9926g，Ga₂O₃5.5118 g. Adding alumina balls into a grinding tank, and grinding and mixing by taking absolute ethyl alcohol as a grinding medium, wherein the ball-milling rotation speed is 400rap/min, and the ball-milling time is 8 hours until the average particle size of the powder is less than 1 mu m;

(2) drying and sieving the obtained slurry, and calcining the sieved powder at 1000 ℃ in the air for 2h to remove organic matters in the powder;

(3) sieving the obtained powder, performing with a mold designed as shown in FIG. 1, applying 4MPa pressure with a single shaft, maintaining for 2min, relieving pressure, plastic packaging, and pressing again in cold isostatic pressing equipment to obtain biscuit with pressure of 200MPa and pressure maintaining time of 30 s;

(4) sintering the obtained ceramic biscuit in SPS, and loading the biscuit after cold waiting into a mould shown in figure 1, wherein the structure of the mould is shown in figures 1-4, and the size of the mould is slightly different from that of the mould in the step (3) in the embodiment; the temperature rise rate is 5 ℃/min, the temperature is kept at 900 ℃ for 3h, then the temperature is raised at the rate of 3 ℃/min, the temperature is kept at 1680 ℃ for 15min, meanwhile, the pressure is kept at 200MPa, the solid phase reaction is completed, and the compact fluorescent ceramic is obtained;

(5) carrying out heat treatment on the ceramic obtained in the step (3) in hot isostatic pressing at 1500 ℃, 200MPa and 2 ℃ of heat preservationh, annealing in air to obtain the fully densified fluorescent ceramic to obtain Y_0.488Lu_2.5Ce_0.012Al₄GaO₁₂The thickness of the fluorescent ceramic plate is 2mm, and the fluorescent ceramic plate is marked as a sample No. 4.

Example 5:

fluorescent ceramic piece Y_1.488Lu_1.5Ce_0.012Al₄GaO₁₂The preparation method comprises the following steps:

(1) weighing Y according to stoichiometric ratio₂O₃:8.7722g,Lu₂O₃:15.5835g,CeO₂：0.1078g，Al₂O₃:10.6478g，Ga₂O₃4.8937 g; adding alumina balls into a grinding tank, and grinding and mixing by taking absolute ethyl alcohol as a grinding medium, wherein the ball-milling rotation speed is 350rap/min, and the ball-milling time is 10 hours until the average particle size of the powder is less than 1 mu m;

(2) drying and sieving the obtained slurry, and calcining the sieved powder at 900 ℃ in the air for 4 hours to remove organic matters in the powder;

(3) sieving the obtained powder, performing with a mold designed as shown in FIG. 1, applying 3MPa pressure in isometric direction for 1min, dry-pressing, and pressing in cold isostatic pressing equipment to obtain biscuit with pressure of 250MPa and pressure maintaining time of 1 min;

(3) the obtained biscuit was directly loaded into a mold shown in fig. 1 and then sintered in a Spark Plasma Sintering (SPS) furnace, the mold structure being shown in fig. 1-4; the temperature rise rate is 20 ℃/min, the temperature is kept at 1000 ℃ for 2, the temperature rise rate is 5 ℃/min, the temperature is kept at 1480 ℃ for 20min, meanwhile, the pressure is kept at 200MPa, the solid phase reaction is completed, and the densification is achieved by removing air holes;

(4) keeping the SPS sample in the air at 1300 ℃ for 20h for annealing, and polishing the obtained fluorescent ceramic to obtain Y_1.488Lu_1.5Ce_0.012Al₄GaO₁₂The thickness of the fluorescent ceramic sheet is 1mm, and the fluorescent ceramic sheet is marked as sample No. 5.

Example 6

Mixing 99.99 mol% of Y₂O₃、99.99mol％Lu₂O₃And 0.1 mol% Ce (OH) CO₃Is dissolved inConcentrated nitric acid is prepared into 0.4mol/L yttrium nitrate-lutetium-cerium solution, and Ga (NO) is added₃)₃And Al (NO)₃)₃·9H₂O is added according to a molar ratio of 1: dissolving 1 proportion in deionized water to prepare 0.4mol/L aluminum nitrate-gallium solution, and adding NH₄HCO₃Dissolving in deionized water to prepare 2mol/L precipitator solution. The aluminum-gallium nitrate solution and the yttrium-lutetium-cerium nitrate solution are mixed according to the formula (Al)³⁺+Ga³⁺):(Y³⁺+Lu³⁺+Ce³⁺) Preparing a mixed solution with the ion ratio of 5:3, and fully stirring and uniformly mixing. 2 g (NH) per 100mL ammonium bicarbonate solution₄)₂SO₄In proportion of (NH) to the ammonium bicarbonate solution₄)₂SO₄. Preparation of Y by direct dropping_0.988Lu₂Ce_0.012Al₄GaO₁₂And (3) dripping an ammonium bicarbonate solution into the vigorously stirred yttrium aluminum gallium mixed solution at the speed of 10mL/min, extracting 2mL of reaction solution every 15min, and simultaneously testing the pH value of a sample by using a pH meter until the pH value is 8. And finally, after a large amount of precipitation products are aged for 8 hours, rinsing the precipitation products for 3 times by using deionized water, and drying the precipitation products in an oven at the temperature of 80 ℃ for 12 hours. And sieving the completely dried precursor by using a 200-mesh nylon sieve, and calcining at 950 ℃ for 2h to obtain ceramic powder (namely calcined material).

(2) Sieving the obtained powder, performing with a mold designed as shown in FIG. 1, maintaining at 3Mpa for 1min under equiaxial unidirectional pressure, dry pressing, directly placing the biscuit into the mold shown in FIG. 1, and sintering in a Spark Plasma Sintering (SPS) furnace, wherein the SPS sintering mold has a structure shown in FIGS. 1-4; the heating rate is 15 ℃/min, the temperature is kept at 1200 ℃ for 2h, the heating rate is 5 ℃/min, the temperature is kept at 1550 ℃ for 20min, the pressure is kept at 60MPa, the solid-phase reaction is completed, and the densification is achieved by removing air holes;

(3) keeping the SPS sample in the air at 1300 ℃ for 10h for annealing, and polishing the obtained fluorescent ceramic to obtain Y_0.988Lu₂Ce_0.012Al₄GaO₁₂The thickness of the fluorescent ceramic sheet is 1mm, and the fluorescent ceramic sheet is recorded as sample No. 6.

Example 7 fluorescent ceramic wafer Structure and topography testing

And respectively carrying out XDR (X digital radiography) tests on samples 1# to 5# to obtain test results, wherein the samples 1# to 5# are all single phases, the test results show that the samples 1# to 5# are compared with Y3Al5O12 and Lu3Al5O12 standard cards, the diffraction peak positions of the samples correspond to the standard cards one by one, and no second-phase mixed peak appears, so that the obtained samples are garnet structure pure phases.

As shown in fig. 5, the typical example of sample 6# is a single garnet phase, and as can be seen from fig. 5, part of the diffraction peaks are shifted in a small angle direction, and the peak positions are shifted in a low angle direction mainly due to the increase of the unit cell by replacing the lattice positions of Al with part of Ga.

And respectively testing the surface morphology and the section morphology of the samples 1# to 5#, wherein the test results show that the samples 1# to 5# form a completely densified polycrystalline structure, the number of pores in and among crystal grains is 0, the crystal grains are uniform in size, and the size of each crystal grain is 2-15 mu m.

Taking sample # 3 as a representative, as shown in fig. 6, 6(a) is a surface morphology SEM image, and 6(b) is a cross-sectional morphology SEM image, it can be seen from fig. 6 that sample # 3 forms a fully densified polycrystalline structure, and simultaneously obtains grains with a relatively uniform size, and the grain size is about 8 μm.

EXAMPLE 8 fluorescent ceramic wafer Performance testing

Excitation-emission spectroscopy test

And respectively carrying out excitation-emission spectrum tests on the samples 1# to 5#, wherein test results show that the excitation wavelength of the samples 1# to 5# is 330-470 nm, and the emission wavelength is 510-530 nm.

Typical representatives are sample # 1 and sample # 5. FIG. 7 is the excitation emission spectrum of sample No. 1, and it can be seen from FIG. 7 that the emission peak of sample No. 1 is located at about 520 nm; FIG. 8 is an excitation emission spectrum of sample No. 5, and it is shown in FIG. 8 that the ceramic material can realize high-efficiency excitation of 450nm blue light and 330nm ultraviolet light, and the emission peak is located in the green region of 510-530 nm.

Thermal quenching test and luminous intensity-temperature test

The samples 1# to 5# are respectively subjected to a thermal quenching test and a luminous intensity-temperature test, and the test results show that the intensities of the emission spectra of the samples 1# to 5# at 550k are more than 90% of the intensities of the emission spectra at 293 k.

Taking sample # 1 as a representative, the thermal quenching spectrum is shown in fig. 9(a), the luminescence intensity-temperature change curve is shown in fig. 9(b), and it can be seen from fig. 9 that the material has a higher thermal quenching temperature and still can maintain 91% of fluorescence intensity at 550K (compared with room temperature).

Emission spectrum testing

Emission spectrum tests are respectively carried out on the samples 1# to 5#, and test results show that the samples 1# to 5# can realize effective excitation of 510-530nm green light under the excitation of 440-460 nm laser.

Taking sample # 4 as a typical representative, fig. 10 is an emission spectrum diagram of 450nm laser excitation, and it can be seen from fig. 10 that under the excitation of 450nm blue light, the emission peak position is near 520nm, a strong emission peak intensity appears, the full width at half maximum of the spectrum is 82nm, a large color gamut range is provided, and a rich use space is provided for improving the laser display performance.

Compactness test

Respectively carrying out density tests on samples 1# to 5#, wherein a Metler-Toriledo precision balance and density accessories are used in a test instrument to carry out the tests by adopting an Archimedes drainage method, and the test results show that the density of the samples is 99.9

Thermal conductivity test

The heat conductivity of the samples 1# to 5# is respectively tested, the tester is a German relaxation-resistant laser thermal conductivity meter (LFA467), and the test result shows that the heat conductivity of the samples 1# to 5# can reach 9-14 W.m^-1K^-1。

Mechanical Property test

The mechanical property of the sample 1# to 5# is tested respectively, the testing instruments are a dynamic elastic modulus tester and a nano indentation tester of American MTS, and the testing result shows that the Young modulus of the sample 1# to 5# is 270 GPa to 295GPa, and the hardness is 21.1 GPa to 24.3 GPa.

Example 9

Fig. 1 is an exploded view of a mold according to the present embodiment, fig. 2 is a front view and a sectional view of an upper ram according to the present embodiment, fig. 3 is a front view and a sectional view of a mold cavity according to the present embodiment, and fig. 4 is a front view and a sectional view of a lower ram according to the present embodiment. The present embodiment will be specifically described with reference to fig. 1 to 4.

The die comprises an upper pressure head 100, a die cavity 200 and a lower pressure head 300 from top to bottom in sequence, wherein an annular boss 301 extending outwards along the vertical direction is arranged on the upper surface of the lower pressure head 300. The cavity of the mold cavity 200 is stepped, and as shown in fig. 3, includes a large diameter cavity 201 having a larger diameter and a small diameter cavity 202 having a smaller diameter.

The large-diameter cavity 201 is matched with the annular boss 301, namely the diameter of the large-diameter cavity 201 is equal to the outer diameter of the annular boss 301, and the height of the large-diameter cavity 201 is equal to that of the annular boss 301, so that the mold cavity 200 can be fixed on the lower pressure head 300. The inner diameter of the annular boss 301 is equal to the diameter of the core 400 so that the core is fixed to the lower ram 300. The annular boss 301 can achieve the effect of forming a closed material cavity.

The core 400 is disposed in the mold cavity 200 coaxially with the mold cavity 200, and the diameter of the core 400 is smaller than the inner diameter of the mold cavity 200. The die pad 500 is a sheet structure, the annular die pad 500 is sleeved on the central core 400, the inner annular wall of the die pad 500 is in contact with the side wall of the central core 400, the outer annular wall of the die pad 500 is in contact with the inner wall of the die cavity 200, and the sealing effect is also achieved.

The upper ram 100 is inserted into the cavity 200 and contacts both the upper surface of the die pad 500 and the inner wall of the cavity 200, the upper portion of the core 400 is inserted into the blind hole of the upper ram 100, and the side wall of the core 400 also contacts the side wall of the blind hole, thus realizing a closed material cavity.

When in use, the middle core 400 is firstly arranged on the lower pressure head 300, then the die cavity 200 is arranged, materials are put in, the annular die cushion 500 is sleeved on the middle core 400, and finally the upper pressure head 100 is covered on the die cavity 200.

The mold provided by the embodiment can be used for preparing the densified annular fluorescent ceramic sheet, so that the performance of the fluorescent ceramic sheet is improved, the preparation process is simplified, and the application range is expanded.

In this application, the structure of the mold in the sintering process is the same as the structure of the mold in the molding process, and both can be the molds provided by this embodiment.

Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

Claims (10)

1. A fluorescent ceramic is characterized in that the fluorescent ceramic is at least one selected from substances in a chemical formula shown in a formula I;

Y_3-x-yLu_xCe_yAl₄GaO₁₂formula I

Wherein the value range of x is more than or equal to 0.01 and less than 3;

the value range of y is more than or equal to 0.0005 and less than or equal to 0.1.

2. The fluorescent ceramic of claim 1, wherein x is in the range of 0.3. ltoreq. x.ltoreq.1.5; the value range of y is more than or equal to 0.005 and less than or equal to 0.09.

3. The fluorescent ceramic of claim 1, wherein the fluorescent ceramic is a polycrystalline luminescent material having a garnet structure and belongs to the cubic system, Ia3d space group.

4. The fluorescent ceramic of claim 1, wherein the grain size of the fluorescent ceramic is 0.5 to 15 μm.

5. The fluorescent ceramic of claim 1, wherein the fluorescent ceramic has an emission spectrum ranging from 510 to 580 nm.

6. The fluorescent ceramic of claim 1, wherein the fluorescent ceramic has an emission spectrum ranging from 510 to 530 nm.

7. The fluorescent ceramic of claim 1, wherein the fluorescent ceramic is a ring-shaped fluorescent ceramic.

8. The fluorescent ceramic of claim 1 or 7, wherein the thickness of the fluorescent ceramic is 1-15 mm.

9. A method for preparing a fluorescent ceramic according to any one of claims 1 to 8, characterized in that it comprises at least the steps of:

a) calcining a mixture containing a Y source, a Lu source, a Ce source, an Al source and a Ga source to obtain a calcined material;

b) and putting the calcined material into a mold for sintering to obtain the fluorescent ceramic.

10. The method according to claim 9, wherein in step a), the Y source is selected from any one of an oxide of Y, a salt compound containing Y;

the Lu source is selected from any one of oxides of Lu and Lu-containing salt compounds;

the Ce source is selected from any one of oxides of Ce and salt compounds containing Ce;

the Al source is selected from any one of oxide of Al and salt compound containing Al;

the Ga source is selected from any one of oxides of Ga and salt compounds containing Ga;

preferably, in step a), the mixture has an average particle size of less than 0.5 μm;

preferably, in step a), the average particle size of the mixture is 20-500 nm;

preferably, in step a), the calcination conditions are: the calcination temperature is 800-1100 ℃; calcining for 2-6 h;

preferably, in step b), the sintering comprises a first sintering phase and a second sintering phase:

conditions of the first sintering stage: the temperature is 900-1400 ℃; the time is 0.5-4 h;

conditions of the second sintering stage: the temperature is 1480-1900 ℃; the time is 15min to 50 h; pressure: 50-200 MPa;

preferably, the die comprises an upper pressing head, a die cavity and a lower pressing head from top to bottom in sequence;

the die cavity is communicated along the vertical direction, and the die cavity is detachably fixed on the lower pressure head;

a central core coaxial with the die cavity is arranged in the cavity of the die cavity; the central core is detachably fixed on the lower pressure head;

the lower surface of the upper pressure head is provided with a blind hole along the vertical direction, one part of the upper pressure head is inserted in the cavity, and the upper part of the central core is inserted in the blind hole;

the lower pressure head, the middle core, the die cavity and the upper pressure head are enclosed to form a closed annular material cavity;

preferably, the mold further comprises an annular mold pad, the mold pad is sleeved on the central core, an inner annular wall of the mold pad abuts against a side wall of the central core, and an outer annular wall of the mold pad abuts against an inner wall of the mold cavity;

preferably, the material of the mould is selected from at least one of mould steel, stainless steel, graphite, zirconia, alumina and agate;

preferably, before step b), the method further comprises:

c) molding the calcined material;

the molding process is at least one of dry pressing molding and cold isostatic pressing molding;

the dry pressing molding comprises the step of putting the calcined material into the die for dry pressing molding;

preferably, the dry-pressing is performed in the mold;

preferably, in step b), after sintering, the method further comprises:

d) annealing treatment;

the annealing conditions are as follows: temperature: 900-1500 ℃; the time is 2-50 h.

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