WO2018205710A1 - Fluorescent composite ceramic and preparation method therefor and use thereof - Google Patents

Abstract

Disclosed are a fluorescent composite ceramic and a preparation method therefor and use thereof. The fluorescent composite ceramic comprises a continuous matrix Al2O3, and at least one fluorescent crystalline particle dispersedly distributed in the continuous matrix Al2O3, wherein the chemical formula of the fluorescent crystalline particle is Y3-x-y-zCexLuyGdzAl5-aGaaO12, wherein 0＜x＜0.3，0 ≤ y＜3，0 ≤ z＜1，and 0 ≤ a＜0.1. A sintering method for the fluorescent composite ceramic has a simple process and is quick, has a low sintering temperature, and is easily applied to mass production.

Description

Fluorescent composite ceramic and preparation method and application thereof Technical field

The invention relates to a high thermal conductivity fluorescent composite ceramic and a preparation method thereof, and the application thereof in the field of high power and high brightness solid state illumination.

Background technique

Solid-state lighting technology is considered to be a new type of green energy in the 21st century with the advantages of energy saving, environmental protection and all solid state, and it shows a rapid development trend. Solid-state lighting technology mainly uses ultraviolet or blue semiconductor chips to excite fluorescent materials to be converted into other visible light, and is realized by appropriate light mixing technology. In order to apply this technology to high-end products such as automotive headlamps, aerospace lighting, portable high-brightness projectors, cinema projectors, large-size multimedia public displays, high-power, high-brightness solid-state lighting has become the technology field. The development trend, this undoubtedly puts higher requirements on the thermal properties of fluorescent materials. At present, the commercial solid-state lighting is mainly realized by a dispensing package, wherein the phosphor needs to be mixed with the organic silica gel and uniformly coated on the surface of the chip. However, the organic silica gel is liable to yellowing or even carbonization under the long-term heat radiation environment. Problems such as light decay and color shift have seriously affected the reliability and service life of the device. For high-power and high-brightness lighting devices, the incident power density is greater, the radiant energy is stronger, and the fluorescent material will undoubtedly face more severe heat radiation problems.

In order to solve the problem of poor working ability of organic silica gel in high temperature environment, remote packaging technology emerged, that is, the packaging technology that keeps the semiconductor chip and fluorescent material at a certain distance, and then the research boom of fluorescent glass and fluorescent ceramics has been set up at home and abroad. A dual role of both encapsulating materials and luminescent materials for remote packaging of solid state lighting. Fluorescent glass is usually a transparent glass formed by co-firing a mixture of a phosphor powder and a glass powder at a relatively low temperature (for example, 600 to 800 ° C); wherein the selection of the glass substrate requires great care, not only the glass substrate and the phosphor are required. The refractive index is close, and the interface between the fluorescent particles and the glass matrix during the sintering process is avoided, and the surface of the luminescent particles is destroyed. In addition, harmful elements in the glass matrix are minimized to enter the luminescent particle lattice, thereby generating luminescence. Quenching (see Non-Patent Document 1). Compared with fluorescent glass, by directly sintering the phosphor into a dense fluorescent ceramic, not only the above problems can be solved, but also the thermal conductivity of the ceramic is greatly improved compared with glass, and it is more promising for application to high power. High-intensity solid-state lighting (see Non-Patent Document 2).

Although there have been many reports on Ce-activated yttrium aluminum garnet (YAG) and yttrium aluminum garnet (LuAG) fluorescent ceramics, the theoretical thermal conductivity of the oxide ceramic system is only 9-14 Wm ^{. 1} K ^-1 (see Non-Patent Documents 3 to 4), therefore, the thermal conductivity of the ceramic obtained by direct sintering is not very satisfactory, and there is still a gap between the practical application of high-power, high-brightness solid-state lighting. For example, Ji of Sungkyunkwan University in Korea has prepared a dense LuAG:Ce green fluorescent ceramic by using MgO as a sintering aid, and its thermal conductivity is only 4 to 5 Wm ^-1 K ^-1 (see Non-Patent Document 5).

According to the Maxwell-Garnet model, the thermal conductivity of the composite increases as the thermal conductivity of the continuous phase increases (see Non-Patent Document 6), and therefore, it is expected that the thermal conductivity of the fluorescent ceramic can be improved by preparing the composite ceramic. On the other hand, by directly selecting a special molding method to obtain a thinner fluorescent ceramic, the heat dissipation problem of the fluorescent material in practical applications can be maximized. However, there are few reports on the microstructure design of high thermal conductivity fluorescent ceramics and the preparation method of thin fluorescent ceramics (see Patent Documents 1-6), which is also a key technical problem to be solved by the present invention.

Prior art literature:

[Non-Patent Document 1] DQ Chen, et al " J. Eur. Ceram. Soc. " 2015; 35: 859-869.;

[Non-Patent Document 2] M. Raukas, et al " ECS J. Solid State Sci. Tech. "2013; 2(2): R3168-3176.;

[Non-Patent Document 3] NP Padture, et al " J. Am. Ceram. Soc. " 1997; 20: 1018-1020.;

[Non-Patent Document 4] PH Klein, et al " J. Appl. Phys. "1967; 38: 1603-1607.

[Non-Patent Document 5] EK Ji, et al. " J. Mater. Chem. C "2015; 3: 12390-12393.

[Non-Patent Document 6] JP Angle, et al. " J. Am. Ceram. Soc. " 2013; 1-8.;

[Non-Patent Document 7] I. Pricha, et al. “ J. Ceram. Sci. Tech. ” 2015; 06(01): 63-68.

[Patent Document 1] PCT/US2015/036256;

[Patent Document 2] PCT/US2014/029092;

[Patent Document 3] PCT/US2011/023026;

[Patent Document 4] US 20150078010A1;

[Patent Document 5] US 20130280520A1;

[Patent Document 6] US 20100207065 A1.

technical problem

In view of the above problems, an object of the present invention is to provide a fluorescent ceramic and a preparation method and application thereof.

Technical solution

In one aspect, the present invention provides a fluorescent composite ceramic comprising a continuous matrix of Al ₂ O ₃ and at least one fluorescent crystalline particle dispersed in the continuous matrix Al ₂ O ₃ , the fluorescent The chemical formula of the crystal grain is Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ , where 0 < x < 0.3, 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a < 0.1.

The invention is directed to a high-power, high-brightness solid-state lighting technology, and at least one Ce-doped yttrium aluminum garnet-based fluorescent particle (fluorescent crystalline particle) is dispersed in a highly thermally conductive Al ₂ O ₃ by a fluorescent ceramic microstructure design. In a continuous matrix, thereby improving the thermal properties of the fluorescent ceramic. Specifically, the fluorescent crystal particles are formed by doping a rare earth element Ce in a crystal structure identical to that of yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ), and have a chemical formula of Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ , wherein 0 < x < 0.3, 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a <0.1; the non-luminescent Al ₂ O ₃ continuous matrix acts as a carrier for the fluorescent crystal particles, The fluorescent crystalline particles are dispersed in a continuous Al ₂ O ₃ matrix. Since the thermal conductivity of the composite increases with the increase of the thermal conductivity of the continuous phase, it is considered that the Al ₂ O ₃ phase (32-35 Wm ^-1 K ^-1 ) has a phase than the YAG phase (9-14 Wm ^-1 K). ^-1 ) Higher thermal conductivity, and the thermal expansion coefficients of the two are close to each other, and no chemical reaction occurs. Therefore, the fluorescent particles dispersed in the Al ₂ O ₃ matrix maintain the excellent optical properties of the initial powder, and the overall composite ceramics will be The Al ₂ O ₃ matrix has a large thermal conductivity.

Preferably, the content of the fluorescent crystal particles in the fluorescent composite ceramic is 23 to 60. Wt%, specifically, from the viewpoint of increasing the luminous intensity per unit area of the fluorescent ceramic, the content of the fluorescent crystalline particles in the fluorescent composite ceramic should be greater than 40 Wwt%; from the perspective of improving the thermal conductivity of composite ceramics, the content of fluorescent crystal particles in fluorescent composite ceramics should be less than 40 The content of the fluorescent crystal particles in the composite ceramic of the present invention is preferably in the range of 23 to 60 wt%, considering the thermal conductivity and the luminescent property. Preferably, the fluorescent crystal particles have a particle diameter of from 1 to 20 μm.

Preferably, the fluorescent composite ceramic emits a broadband emission spectrum having a peak wavelength in the range of 520 to 580 nm under blue light excitation of 440 to 470 nm.

Preferably, the fluorescent composite ceramic has a relative density greater than 80%.

Preferably, the content of the fluorescent crystal particles in the fluorescent composite ceramic is 23 to 39 wt%, and the thermal conductivity of the fluorescent composite ceramic is 15 to 33 Wm ^-1 K ^-1 .

Preferably, the content of the fluorescent crystal particles in the fluorescent composite ceramic is 41 to 60. The wt%, the luminous intensity of the fluorescent composite ceramic is maintained at 90% or more of the original powder.

In a second aspect, the present invention also provides a method for preparing a fluorescent composite ceramic as described above, comprising:

The Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor powder and the Al ₂ O ₃ powder are used as raw materials, and are uniformly mixed according to a mass ratio, and then preformed to form a green body;

The obtained green body is rapidly sintered by a discharge plasma to obtain the fluorescent composite ceramic;

The discharge plasma sintering temperature is 1300 to 1600 ° C, the holding time is 3 to 10 minutes, and the uniaxial pressure is 20 to 80 MPa.

Preferably, the rate of temperature rise of the spark plasma sintering is 100 to 400 ° C / min, and the rate of temperature drop after sintering is 10 to 300 ° C / min.

In a third aspect, the present invention also provides a method for preparing the above fluorescent composite ceramic, comprising:

The Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor powder and the Al ₂ O ₃ powder are used as raw materials, and are uniformly mixed according to a mass ratio, and then preformed to form a green body;

The obtained green body is subjected to hot press sintering to obtain the fluorescent composite ceramic;

The hot pressing sintering temperature is 1300 to 1600 ° C, the holding time is 1 to 10 hours, and the sintering pressure is 20 to 80 MPa.

In a fourth aspect, the present invention provides a method for preparing a fluorescent composite ceramic as described above, comprising:

The Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor powder and the Al ₂ O ₃ powder are used as raw materials, and are uniformly mixed according to a mass ratio, and then preformed to form a green body;

The obtained green body is subjected to debonding, and then calcined at 1300 to 1600 ° C for 1 to 10 hours in a protective atmosphere or under vacuum to obtain the fluorescent composite ceramic.

Preferably, the preform is preformed by dry molding or wet molding;

The dry forming is dry press forming and/or cold isostatic pressing, and the wet forming is grout molding and/or tape casting.

Moreover, preferably, the pressure of the dry press molding is 10-40 MPa, the pressure of the cold isostatic pressing is 150 to 250 MPa.

Moreover, preferably, the wet molding comprises: using Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor powder and Al ₂ O ₃ powder as raw materials, and uniformly mixing according to a mass ratio. , adding a dispersant, a binder and a plastic agent, and preforming to form a green body;

The dispersing agent is at least one of a phosphate ester, a castor oil, and a castor oil phosphate, and is added in an amount of Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor and Al ₂ O ₃ powder. 2 to 5 wt% of the total mass of the body;

The plasticizer is at least one of benzyl phthalate, polyethylene glycol and ethylene glycol, and is added in an amount of Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor and Al. 5 to 8 wt% of the total mass of ₂ O ₃ powder;

The binder is at least one of polyvinyl butyral, polyacrylic acid methyl ester and ethyl cellulose, and is added in an amount of Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor And 5 to 8 wt% of the total mass of the Al ₂ O ₃ powder.

Further, preferably, the obtained green body is debonded before calcination, and the debonding is carried out by raising the temperature by 450 to 650 ° C at a temperature increase rate of 2 to 5 ° C /min and holding it for 5 to 15 hours.

In the above method, preferably, the Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor has a particle size of the order of micrometers, and the particle size of the Al ₂ O ₃ powder is sub- Micron or nanoscale. The Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor has a particle diameter of 1 to 20 μm, and the Al ₂ O ₃ powder has a particle diameter of 0.1 to 0.7 μm.

In the above method, preferably, the obtained fluorescent composite ceramic is placed in an air or oxygen atmosphere and heat-treated at 1000 to 1200 ° C for 5 to 20 hours.

In a fifth aspect, the present invention also provides a lighting fixture comprising the above fluorescent composite ceramic, specifically comprising an excitation light source and the above fluorescent composite ceramic. The excitation light source is a blue light emitting element having an emission wavelength of 440 to 470 nm. That is to say, the lighting fixture further includes a fluorescent composite ceramic having an emission peak in a wavelength range of 520 to 580 nm by excitation light of 440 to 470 nm, and high-intensity white light by a light mixing technique.

Beneficial effect

The fluorescent composite ceramic (fluorescent ceramic) provided by the invention has excellent thermal stability, high thermal conductivity and external quantum efficiency. The sintering method provided by the invention has simple and rapid process, low sintering temperature and easy mass production. The fluorescent ceramic designed and prepared by the invention and the synthetic method thereof are of great significance for promoting the industrial development of high-power, high-brightness solid-state lighting.

DRAWINGS

1 is an XRD pattern of a fluorescent ceramic prepared in Example 1;

2 is a thermal quenching performance of the fluorescent ceramic prepared in Example 2;

3 is a microstructure of a polished surface of a fluorescent ceramic prepared in Example 3;

4 is an emission spectrum of a fluorescent ceramic prepared in Example 4;

5 is a thermal conductivity data of a fluorescent ceramic prepared in Example 5;

6 is a schematic view of a fluorescent ceramic prepared in Examples 1-5 for high power white LED illumination or laser illumination;

Table 1 in Fig. 7 is a performance parameter of the fluorescent suit ceramic prepared by the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is further illustrated by the following examples, which are not to be construed as limiting the invention.

The fluorescent composite ceramic prepared by the invention has higher thermal conductivity than the conventional fluorescent materials, and has important application potential in the field of high-power, high-brightness solid-state lighting. The fluorescent ceramic has a characteristic composite microstructure in which the fluorescent crystalline particles are dispersed in a continuous matrix that does not emit light. Wherein, the fluorescent crystal particles are formed by doping a rare earth element Ce in a crystal structure identical to that of yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ), and the chemical formula thereof is Y _3-xyz Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ , wherein 0 < x < 0.3, 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a < 0.1, and the non-luminescent substrate is Al ₂ O ₃ . That is to say, the fluorescent crystal particles formed by doping the rare earth element Ce in the same crystal structure as the yttrium aluminum garnet are dispersed in the non-luminescent Al ₂ O ₃ continuous matrix. The fluorescent composite ceramic comprises one or more fluorescent crystal particles in a range of from 23 to 60% by weight, preferably from 23 to 39% by weight or from 41 to 60% by weight. The chemical formula of the fluorescent crystal particles in the fluorescent composite ceramic is Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ , where 0 <x<0.3, 0 ≤ y<3, 0 ≤ z<1, 0 ≤ a<0.1, for Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ fluorescent crystal particles, x reflects the doping concentration of rare earth element Ce, and y reflects the concentration of Lu substituted Y , z reflects the concentration of Gd substituted Y, a reflects the concentration of Ga substituted Al; by adjusting the chemical composition of the functional elements of the fluorescent crystalline particles, fluorescent ceramics with different emission wavelengths can be obtained. In addition, the fluorescent ceramic is combined with a blue light excitation element, and high brightness white light can be realized by a light mixing technique.

In the present invention, the fluorescent ceramic emits a broadband emission spectrum having a peak wavelength in the range of 520 to 580 nm under blue light excitation of 440 to 470 nm. Preferably, the peak wavelength is emitted at 540-560 Wideband emission spectrum in the nm range.

In the present invention, the fluorescent ceramic is a mixture of fluorescent crystal particles and a non-luminescent substrate, and the content of the fluorescent crystal particles in the mixture is in the range of 23 to 39 wt% or 41 to 60 wt%; From the viewpoint of obtaining a high thermal conductivity fluorescent ceramic, the content of the fluorescent crystal particles should be less than 40% by weight; from the viewpoint of obtaining a high luminous intensity fluorescent ceramic, the content of the fluorescent crystalline particles should be higher than 40% by weight. The content of the fluorescent crystal particles in the fluorescent composite ceramic is 23 wt% or more and less than 40 wt%, preferably 23 to 39 wt%, and the thermal conductivity of the fluorescent composite ceramic is 15 to 33 Wm ^-1 K ^-1 . The content of the fluorescent crystal particles in the fluorescent composite ceramic is more than 40% by weight and less than or equal to 60% by weight, preferably 41% to 60% by weight, and the fluorescent composite ceramic has an illuminating intensity of 90% or more of the original powder. The fluorescent crystal particles may have a particle diameter of 1 to 20 μm.

In the present invention, the relative density of the fluorescent ceramics should be greater than 80%, the presence of a certain porosity and a certain pore distribution can enhance the scattering of incident light, increase the probability of incident light being absorbed by the fluorescent particles, and thereby increase the output of the fluorescent ceramic. Lumens, the relative density of fluorescent ceramics should be less than 98% from the perspective of achieving high lumen efficiency. On the other hand, the presence of pores hinders the improvement of the thermal conductivity of the fluorescent ceramic. The relative density of the fluorescent ceramics should be greater than 95% from the viewpoint of thermal conductivity.

In the present invention, the fluorescent ceramic has excellent heat quenching performance; compared with the original powder, the thermal stability of the fluorescent ceramic is increased by 5 to 20% at a temperature of 300 ° C than the corresponding powder.

In the present invention, the fluorescent ceramic has excellent thermal conductivity, and the thermal conductivity is closely related to the degree of compactness of the ceramic sintering, the content of Al ₂ O ₃ in the microstructure, and the grain size thereof. Generally, the composite fluorescent ceramic prepared by the present invention has a thermal conductivity of 10 to 32 Wm ^-1 K ^-1 .

The method of the invention combines a method for preparing a composite fluorescent ceramic sheet with low temperature, simple and rapid process, and easy mass production. Further, as the ultimate goal of the present invention, the high thermal conductive composite fluorescent ceramic composite prepared in the present invention is used for realizing high power, high brightness solid state illumination. In the present invention, a raw material mixture is obtained by uniformly mixing raw material powders of the above two kinds of phases (fluorescent crystal particles and non-light-emitting matrix is Al ₂ O ₃ ), and a fluorescent ceramic composite is obtained by sintering at a relatively low temperature through a suitable molding process. The preparation method of the fluorescent composite ceramic provided by the present invention is exemplarily described below. Mixing: In order to ensure the excellent optical properties of the fluorescent ceramics, the present invention directly uses commercial yttrium aluminum garnet-based phosphors of different emission wavelengths (520-580 nm) as fluorescent crystal particles, preferably having a particle size ranging from 1 to 20 μm. Meanwhile, Al ₂ O _{3 is selected} as the host material, and preferably has a particle diameter ranging from 0.1 to 0.7 μm. The two are weighed according to a certain mass ratio and uniformly mixed, and may be mixed by a dry method or a wet method (such as ball milling or rotary evaporation).

Molding: The present invention employs dry molding or wet molding. Dry forming includes dry press forming and/or cold isostatic pressing. The pressure of the dry press molding may be 10 to 40 MPa, and the pressure of the cold isostatic pressing may be 150 to 250 MPa. The wet forming is a slip casting and/or tape casting. Specifically, the wet forming may be carried out by grouting or tape casting to obtain a thinner blank. The Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor and the Al ₂ O ₃ powder are used as raw materials, and uniformly mixed according to the mass ratio, and then a dispersant, a binder and a plastic agent are added. After the preform is preformed, a green body is obtained. The plasticizer used may be at least one of benzyl phthalate, polyethylene glycol and ethylene glycol, and may be added in an amount of Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor and The total mass of the Al ₂ O ₃ powder is 5 to 8 wt%. The binder used is at least one of polyvinyl butyral, polyacrylic acid methyl ester and ethyl cellulose, and may be added in an amount of Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor And 5 to 8 wt% of the total mass of the Al ₂ O ₃ powder. The dispersing agent used is at least one of phosphate ester, castor oil and castor oil phosphate, and may be added in an amount of Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor and Al ₂ O ₃ powder. 2 to 5 wt% of the total mass of the body. As an example, tape casting mainly includes three steps of preparation, casting and green drying of ceramic slurry, first adding a dispersing agent for the first stage of ball milling, and then adding a binder and a plastic agent for the second stage of ball milling. Then, it is cast-molded on a cast film forming machine, and finally dried under certain conditions. Before the calcination, the obtained green body was subjected to debonding, and the debonding was carried out by raising the temperature at 450 to 650 ° C at a heating rate of 2 to 5 ° C /min and holding it for 5 to 15 hours.

Sintering: The present invention employs a sintering process such as hot press sintering, rapid discharge by discharge plasma, and normal pressure sintering. The hot press sintering and the rapid sintering of the discharge plasma are respectively performed in a hot press furnace and a discharge plasma rapid sintering furnace, and the formed block or unformed powder is loaded into a mold under an inert atmosphere or a vacuum state. The axial pressure is 20-80 MPa, the sintering temperature is 1300-1600 °C (preferably 1300-1500 °C), and the holding time of hot-sintering and discharge plasma rapid sintering is 1 to 10 h and 3 to 10 min, respectively, and then cooled with the furnace. A composite fluorescent ceramic is prepared. The rate of temperature rise of the spark plasma sintering may be 100 to 400 ° C / min, and the rate of cooling after sintering may be 50 to 300 ° C / min. From the viewpoint of industrial application and mass production, a sintering method of atmospheric pressure sintering is preferred, and normal pressure sintering is carried out in a high-temperature sintering furnace, and the formed pigment is formed in an inert atmosphere (protective atmosphere such as argon gas, nitrogen gas, etc.) or under vacuum. The billet is placed in a crucible and then placed in a sintering furnace at a sintering temperature of 1300 to 1600 ° C (preferably 1450 to 1600 ° C, which can be heated at a rate of 10 to 20 ° C / min), and the holding time is 2 to 10 h, followed by furnace Cooling gives a ceramic flake.

Machining. The samples prepared by hot pressing sintering and rapid sintering of discharge plasma need to be machined to the required thickness. In practical applications, the thickness of the ceramic sheets is generally about 0.1. Mm. The ceramic flakes prepared by wet grouting or casting molding combined with atmospheric pressure sintering can meet the practical application needs without or with only a small amount of mechanical processing. The thickness and surface roughness of the obtained fluorescent composite ceramic are mainly adjusted by at least one treatment method such as grinding, polishing, or the like.

The above preparation method further comprises heat-treating the fluorescent ceramics after mechanical processing (before machining) at 1000 to 1200 ° C for 5 to 20 hours in an air or oxygen atmosphere to remove oxygen vacancies and graphite equivalent inside the fluorescent ceramics. To improve its optical performance.

As an example of a method of preparing a fluorescent composite ceramic, the preparation method includes the following steps:

(1) Mixing: Commercial yttrium aluminum garnet-based phosphors with different emission wavelengths (520-580 nm) are used as fluorescent crystal particles, and alumina is used as a matrix material, and the two are weighed and mixed according to a certain mass ratio;

(2) Molding: preforming of the green body by dry pressing and/or cold isostatic pressing, wet grouting or casting molding;

(3) Sintering: High-temperature sintering is performed by hot press sintering, rapid sintering by discharge plasma, and atmospheric pressure sintering in a protective atmosphere or vacuum, and the sintering temperature is 1300 to 1600 °C.

The present invention provides the above-described fluorescent ceramics useful as luminescent materials in solid state lighting, preferably in high power, high brightness lighting fixtures. The lighting fixture includes an excitation light source and any of the above-described fluorescent ceramics. The excitation light source is a blue light emitting element having an emission wavelength of 440 to 470 nm. Specifically, the high-power, high-brightness lighting fixture further includes a fluorescent ceramic that has an emission peak in a wavelength range of 520 to 580 nm by excitation of blue light of 440 to 470 nm, and passes the emitted light of the incident blue light and the fluorescent ceramic through appropriate The light mixing technique gets white light.

Characterization and composition characterization of fluorescent composite ceramics

Characterization of external quantum efficiency: The absorption spectrum and emission spectrum of the sample were tested using a multi-channel spectrometer (MCPD-7000, Otsuka Electronics, Japan), and the reflectance spectra were calibrated by a standard white plate (BaSO ₄ ) to calculate the quantum efficiency of the sample.

Thermal quenching performance characterization: The high-temperature fluorescence controller is used to test the thermal quenching performance of the original powder and fluorescent ceramic composite. The sample is heated to a specific temperature (30 °C, 50 °C, 100 °C, 150 °C...) and then incubated for 5 min. Ensure that the surface temperature of the sample and the internal temperature are consistent, then test the luminescence spectrum of the sample at a specific temperature, and finally plot the luminescence intensity of the sample as a function of temperature.

Phase composition characterization: X-ray powder diffractometer (XRD) was used to detect the initial phase mixture and the phase composition of the fluorescent ceramic composite sintered under different process conditions; the test conditions were: room temperature, the radiation source was Cu target Kα ₁ ray, λ = 0.15406 nm, operating voltage 40 kV, operating current 200 mA, step scan 5 ° min ^-1 , step size 0.02 °.

Microstructural characterization: The characteristic microstructure of the fluorescent ceramic composite was detected by field emission scanning electron microscopy (SEM, S-4800, Hitachi) and cathode ray illuminating system (MP32S/M, Hitachi).

Characterization of fluorescence performance: The emission spectrum of the prepared fluorescent ceramic composite was measured by fluorescence spectrometer (F-4500, Hitachi, Japan), and the excitation source was a 200 W xenon lamp; the quantum efficiency test system (QE-2100, Otsuka) was used. Electronics) Tests the quantum efficiency of the composite of the original powder and the fluorescent ceramic.

Thermal conductivity test: The thermal conductivity of the fluorescent ceramic composite was measured using a laser flasher (LFA447, Netzsch, Germany) and using alumina ceramics (thermal conductivity 30 Wm ^-1 K ^-1 ) as standard sample.

The embodiments are further exemplified below to explain the present invention in detail. It is to be understood that the following examples are only intended to illustrate the invention and are not to be construed as limiting the scope of the invention, and that some non-essential improvements and modifications made by those skilled in the art in light of the The scope of protection. The specific process parameters (eg, specific temperature, pressure, time, charge amount, etc.) and the like described below are also only one example of a suitable range, that is, those skilled in the art can make a suitable range selection by the description herein. It is not intended to be limited to the specific values exemplified below. Unless otherwise specified, the Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor used in the following examples has a particle diameter of 1 to 20 μm, and the particle size of the Al ₂ O ₃ powder. It is 0.1 to 0.7 μm.

Example 1

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (39 g) and Al ₂ O ₃ raw material powder (61 g) were placed in a high-purity alumina ball mill jar, and high-purity alumina with a diameter of 5 mm was separately added. The ball (75 g) and absolute ethanol (80 g) were placed in a planetary ball mill for 12 h, and the slurry was placed in an oven at 80 ° C for 12 h to be fully dried, then ground, passed through a 100 mesh nylon sieve, and placed. Spare in the reagent bottle.

The uniformly mixed raw material powder is sintered by the rapid plasma sintering technique, 0.65 g of raw material powder is weighed each time, and a graphite mold having an inner diameter of 15 mm is placed, and a layer of graphite paper is placed inside the graphite mold to isolate the raw material. Powder and graphite molds. The outer side of the mold is covered with a layer of insulating carbon felt to prevent the heat from spreading on the surface of the mold. During the sintering process, the uniaxial pressure applied to the upper and lower indenters was 60 MPa, the heating rate was 300 °Cmin ^-1 , the highest sintering temperature was 1360 °C, and the holding time was 5 min. During the sintering process, the surface temperature of the graphite mold was measured by an infrared thermometer to monitor the temperature of the sample. After the sintering, the sample was rapidly cooled to room temperature at a cooling rate of 300 ° C min ^-1 .

The upper and lower surfaces of the sintered sample were separately machined and then thrown to a thickness of 0.1 mm on a polishing machine.

The processed sample was placed in a muffle furnace at 1000 ° C for 10 h for heat treatment to obtain a fluorescent ceramic composite sample. The XRD pattern of the composite fluorescent ceramic composite obtained by sintering is shown in Fig. 1. As in the initial mixture, the fluorescent ceramic prepared by high-temperature sintering of the discharge plasma contains only YAG:Ce and Al ₂ O ₃ phases, indicating the sintering process. No reaction occurs between the two phases, and no other heterogeneous phases are formed.

The external quantum efficiency of the sample obtained by sintering is consistent with the initial powder, up to 76%. The prepared fluorescent ceramic emits high-intensity yellow light under the excitation of the blue laser, and the incident light of the incident blue laser and the fluorescent ceramic is obtained by a suitable light mixing technique to obtain high-intensity white light. Among them, at the maximum input power density of 50 Wmm ^-2 , as the input current increases from 0.4 A to 1.6 A, the output lumen of the fluorescent ceramic increases linearly, and no significant luminescence saturation is observed. At 45 W input blue laser illumination, the output of the fluorescent ceramics is as high as 2000 lm.

Example 2

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (25 g) and Al ₂ O ₃ raw material (75 g) were placed in an alumina ball mill jar and high-purity alumina balls of 5 mm in diameter were added respectively (75 g And anhydrous ethanol (80 g), placed in a planetary ball mill for 24 h, the slurry was placed in an oven at 80 ° C for 12 h, dried, then ground, passed through a 100 mesh sieve, placed in a reagent bottle .

After the powder was dry-formed (10 MPa) and cold isostatically pressed (200 MPa), it was heated to a temperature of 10 ° C min ^-1 to 1550 ° C and kept for 4 h, 40 MPa by hot pressing sintering process. A composite fluorescent ceramic with a relative density greater than 99% was prepared under sintering pressure, and the thermal conductivity reached 20 Wm ^-1 K ^-1 or more.

The upper and lower surfaces of the sintered sample were separately machined and then thrown to a thickness of 0.1 mm on a polishing machine.

The processed sample was placed in a muffle furnace and kept at 1000 ° C for 15 h for heat treatment to obtain a fluorescent ceramic sample.

The fluorescent composite ceramic of the present invention exhibits excellent heat quenching performance by the design of the composite microstructure. Figure 2 compares the thermal quenching properties of the original powder and the fluorescent ceramic prepared by hot pressing sintering. When the temperature is raised from 30 ° C to 300 ° C, the luminous intensity of the original powder decreases linearly. Compared with the powder, the thermal quenching performance of the fluorescent ceramic at 250 ° C is improved by more than 10%, showing a clear advantage.

Example 3

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (45 g) and Al ₂ O ₃ raw material (55 g) were placed in an alumina ball mill jar and high-purity alumina balls of 5 mm in diameter were added respectively (75 g And high purity anhydrous ethanol (80 g) and castor oil phosphate (5 g) were ball milled on a planetary ball mill for 24 h, then polyvinyl butyral (7 g) and butyl benzyl phthalate were added. (6.8 g) The second stage of ball milling was carried out, followed by casting on a cast film forming machine, and finally dried in a closed casting chamber for 6 h, then the casting film was removed against the casting direction, and the reel was to be use.

Before the sintering, the cast film was subjected to debonding treatment in a normal pressure sintering furnace, and the temperature was raised to 600 ° C at a heating rate of 3 ° C min ^-1 for 4 h, and then cooled with the furnace.

The debonded cast film was placed in a corundum crucible, placed in a normal pressure sintering furnace, and raised to 1550 ° C at a heating rate of 20 ° C min ^-1 under a vacuum atmosphere for 8 h. The ceramic sheet was dried to a thickness of 0.1 mm.

The sintered ceramic flakes were placed in a muffle furnace and kept at 1100 ° C for 2 h for heat treatment without mechanical processing and polishing to obtain a fluorescent ceramic sample. Figure 3 shows the microstructure of cast molding process with the use of vacuum sintering and pressure to obtain a phosphor preparation of a ceramic sheet, consistent with intended design, large size of the Y ₃ Al ₅ O _12: Ce luminescent particles dispersed in a continuous Al ₂ In the O ₃ non-luminescent substrate, the particle diameter of the Y ₃ Al ₅ O ₁₂ :Ce luminescent particles is 1-20 μm, and the particle size of the luminescent particles before and after sintering does not change significantly.

Example 4

Commercially available Lu ₃ Al ₅ O ₁₂ :Ce green phosphor (10 g, peak of emission spectrum at 535 nm), Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (30 g, peak of emission spectrum at 565 Nm) and Al ₂ O ₃ raw materials (60 g) were placed in an alumina ball mill jar, respectively, with high-purity alumina spheres (75 g) and high-purity absolute ethanol (80 g) with a diameter of 5 mm, and castor oil. Phosphate (2.5 g) was ball milled on a planetary ball mill for 24 h, then polyvinyl butyral (5.9 g) and butyl benzyl phthalate (5.9 g) were added for the second stage of ball milling, followed by casting. The film forming machine was subjected to tape casting, and finally, after drying in a closed casting chamber for 8 hours, the casting film was removed against the casting direction, and the reel was used.

Before the sintering, the cast film was subjected to debonding treatment in a normal pressure sintering furnace, and the temperature was raised to 600 ° C at a heating rate of 3 ° C min ^-1 for 4 h, and then cooled with the furnace.

The debonded cast film was placed in a corundum crucible and placed in a normal pressure sintering furnace. The temperature was raised to 1600 ° C at a heating rate of 10 ° C min ^-1 under vacuum atmosphere for 2 h. The ceramic sheet was dried to a thickness of 0.1 mm.

The sintered ceramic flakes were placed in a muffle furnace at 1200 ° C for 4 h without heat treatment to obtain a fluorescent ceramic sample. Figure 4 shows the emission spectrum of a fluorescent ceramic prepared by casting and atmospheric pressure vacuum sintering. It is not difficult to find that the emission spectrum of the composite fluorescent ceramic is two kinds of fluorescent crystal particles (Lu ₃ Al ₅ O ₁₂ : Ce and Y _{The combination of 3} Al ₅ O ₁₂ :Ce) emission spectra with a half-value width of up to 140 nm is very advantageous for encapsulating white light with a high color rendering index.

Example 5

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (58 g) and Al ₂ O ₃ raw material (42 g) were placed in an alumina ball mill jar and high-purity alumina balls of 5 mm in diameter were added respectively (75 g And high-purity anhydrous ethanol (80 g), placed in a planetary ball mill for 10 h, the slurry was placed in an oven at 80 ° C for 12 h, dried, then ground, passed through a 100 mesh sieve, placed in the reagent Spare in the bottle.

The uniformly mixed raw material powder is sintered by the rapid plasma sintering technique, 0.65 g of raw material powder is weighed each time, and a graphite mold having an inner diameter of 15 mm is placed, and a layer of graphite paper is placed inside the graphite mold to isolate the raw material. Powder and graphite molds. The outer side of the mold is covered with a layer of insulating carbon felt to prevent the heat from spreading on the surface of the mold. During the sintering process, the uniaxial pressures applied to the upper and lower indenters were 40, 80 MPa, the heating rate was 300 ° C min ^-1 , the highest sintering temperature was 1400 ° C, and the holding time was 3 min. During the sintering process, the surface temperature of the graphite mold was measured by an infrared thermometer to monitor the temperature of the sample. After the sintering, the sample was rapidly cooled to room temperature at an average temperature drop rate of 300 ° C min ^-1 .

The upper and lower surfaces of the sintered sample were separately machined and then thrown to a thickness of 0.1 mm on a polishing machine. The processed sample was placed in a muffle furnace and kept at 1000 ° C for 15 h for heat treatment to obtain a fluorescent ceramic sample.

Figure 5 compares the thermal conductivity data of the original powder and the fluorescent ceramics prepared at different sintering pressures (40 MPa, 80 MPa), which are 0.5, 9, 15 Wm ^-1 K ^-1 , in other words, 80 MPa. The thermal conductivity of the prepared fluorescent ceramic under pressure is about 30 times that of the original powder. It is also stated that the thermal conductivity of the fluorescent ceramic is directly related to the content of Al ₂ O ₃ and the relative density.

Example 6

Commercial Lu ₃ Al ₅ O ₁₂ :Ce green phosphor (16 g), Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (25 g) and Al ₂ O ₃ raw material (59 g) were placed in an alumina ball mill jar Adding high-purity alumina spheres (75 g) with a diameter of 5 mm and high-purity absolute ethanol (80 g) and castor oil phosphate (4 g) to a planetary ball mill for 24 h, adding polyethylene Alcohol butyral (8 g) and butyl benzyl phthalate (7 g) were subjected to a second stage of ball milling, followed by cast molding on a cast film forming machine, and finally dried naturally in a closed casting chamber for 12 h. Thereafter, the cast film is removed against the casting direction, and the reel is ready for use.

Before the sintering, the cast film was subjected to debonding treatment in a normal pressure sintering furnace, and the temperature was raised to 600 ° C at a heating rate of 3 ° C min ^-1 for 4 h, and then cooled with the furnace.

The debonded cast film was placed in a corundum crucible and placed in a normal pressure sintering furnace. The temperature was raised to 1570 °C at a heating rate of 15 °C min ^-1 for 8 h under vacuum atmosphere. The ceramic sheet was dried to a thickness of 0.1 mm.

The sintered ceramic flakes are placed in a muffle furnace and kept at 1000 ° C for 20 h for heat treatment without mechanical processing and polishing to obtain a fluorescent ceramic sample.

Finally, the present invention provides a high power, high brightness lighting fixture comprising an excitation source and a highly thermally conductive fluorescent composite ceramic of the present invention.

As the light-emitting source, a blue light-emitting element of 440 to 470 nm is preferable.

6 is a schematic view showing the application of the high thermal conductivity fluorescent ceramic designed in the present invention to high-power, high-brightness solid-state illumination, wherein (a) of FIG. 6 shows a combination of a fluorescent ceramic and a blue LED chip to realize high-power LED illumination. (b) in FIG. 6 shows that the fluorescent ceramic is combined with the blue laser chip to realize high-power laser illumination in the reflective operation mode.

Comparative example 1

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (20 g) and Al ₂ O ₃ raw material powder (80 g) were placed in a high-purity alumina ball mill jar, respectively, and high-purity alumina with a diameter of 5 mm was added. The ball (75 g) and absolute ethanol (80 g) were placed in a planetary ball mill for 12 h, and the slurry was placed in an oven at 80 ° C for 12 h to be fully dried, then ground, passed through a 100 mesh nylon sieve, and placed. Spare in the reagent bottle;

The uniformly mixed raw material powder is sintered by the rapid plasma sintering technique, 0.65 g of raw material powder is weighed each time, and a graphite mold having an inner diameter of 15 mm is placed, and a layer of graphite paper is placed inside the graphite mold to isolate the raw material. Powder and graphite molds. The outer side of the mold is covered with a layer of insulating carbon felt to prevent the heat from spreading on the surface of the mold. During the sintering process, the uniaxial pressure applied to the upper and lower indenters was 80 MPa, the heating rate was 300 ° Cmin ^-1 , the highest sintering temperature was 1320 ° C, and the holding time was 5 min. During the sintering process, the surface temperature of the graphite mold is measured by an infrared thermometer to monitor the temperature of the sample. After the sintering is finished, the sample is rapidly cooled to room temperature at a cooling rate of 300 ° C min ^-1 ;

The upper and lower surfaces of the sintered sample were separately machined and then thrown to a thickness of 0.1 mm on a polishing machine. The processed sample was placed in a muffle furnace at 1000 ° C for 12 h for heat treatment to obtain a fluorescent ceramic composite sample having a relative density of more than 99% and an external quantum efficiency of only 65%.

Comparative example 2

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (65 g) and Al ₂ O ₃ raw material (35 g) were placed in an alumina ball mill jar and high-purity alumina spheres of 5 mm in diameter were added respectively (75 g And high purity anhydrous ethanol (80 g) and castor oil phosphate (4 g) were ball milled on a planetary ball mill for 24 h, then polyvinyl butyral (8 g) and butyl benzyl phthalate were added. (7 g) The second stage of ball milling was carried out, followed by casting on a cast film forming machine, and finally dried in a closed casting chamber for 12 h, then the casting film was removed against the casting direction, and the reel was to be use;

Before the sintering, the cast film is subjected to debonding treatment in a normal pressure sintering furnace, and is heated to 600 ° C at a heating rate of 3 ° C min ^-1 for 4 h, and then cooled with the furnace;

The debonded cast film was placed in a corundum crucible and placed in a normal pressure sintering furnace. Under a vacuum atmosphere, the temperature was raised to 1600 ° C at a heating rate of 15 ° C min ^-1 and held for 10 h. , cooling with a furnace to obtain a ceramic sheet having a thickness of 0.1 mm;

The ceramic sheet obtained by sintering is placed in a muffle furnace and kept at 1000 ° C for 20 h for heat treatment to obtain a fluorescent ceramic sample with a thermal conductivity of 5 Wm ^-1 K ^-1 and external quantum efficiency without mechanical processing and polishing treatment. It is 75%.

Table 1 shows the performance parameters of the fluorescent suit ceramics prepared in the present invention.

Industrial applicability

The invention designs and manufactures a fluorescent composite ceramic with excellent luminescence performance, good thermal stability and high quantum efficiency. The preparation method is simple and rapid, and in particular, casting or grouting molding combined with atmospheric pressure sintering is expected to realize mass production of fluorescent ceramic sheets. The designed high thermal conductivity fluorescent composite ceramic can be combined with blue light emitting elements to realize high-power, high-brightness solid-state illumination. It is expected that this fluorescent composite ceramic and its preparation method will be widely used to promote the prosperity of high-power, high-brightness solid-state lighting.

Claims (14)

1. A fluorescent composite ceramic, characterized in that the fluorescent composite ceramic comprises a continuous matrix Al ₂ O ₃ and at least one fluorescent crystalline particle dispersed in the continuous matrix Al ₂ O ₃ , the fluorescent crystalline particle The chemical formula is Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ , where 0<x<0.3, 0≤y<3, 0≤z<1, 0≤a<0.1.
2. The fluorescent composite ceramic according to claim 1, wherein the fluorescent composite ceramic has a content of fluorescent crystal particles of 23 to 60% by weight, and the fluorescent crystal particles have a particle diameter of 1 to 20 μm.
3. The fluorescent composite ceramic according to claim 1 or 2, wherein the fluorescent composite ceramic emits a broadband emission spectrum having a peak wavelength in the range of 520 to 580 nm under blue light excitation of 440 to 470 nm.
4. The fluorescent composite ceramic according to any one of claims 1 to 3, wherein the fluorescent composite ceramic has a relative density of more than 80%.
5. The fluorescent composite ceramic according to any one of claims 1 to 4, wherein a content of the fluorescent crystal particles in the fluorescent composite ceramic is 23 to 39 wt%, and a thermal conductivity of the fluorescent composite ceramic is 15 ~33 Wm ^-1 K ^-1 .
6. The fluorescent composite ceramic according to any one of claims 1 to 4, wherein a content of the fluorescent crystal particles in the fluorescent composite ceramic is 41 to 60% by weight, and the luminous intensity of the fluorescent composite ceramic is the original powder. More than 90%.
7. A method for preparing a fluorescent composite ceramic according to any one of claims 1 to 6, which comprises:

   Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor powder and Al ₂ O ₃ powder are used as raw materials, and uniformly mixed according to mass ratio, and then preformed to form a green body, wherein 0<x<0.3 , 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a <0.1;

   The obtained green body is rapidly sintered by a discharge plasma to obtain the fluorescent composite ceramic;

   The temperature of the discharge plasma sintering is 1300 to 1600 ° C, the holding time is 3 to 10 minutes, and the uniaxial pressure is 20 to 80 MPa.
8. The preparation method according to claim 7, wherein the rate of temperature rise of the discharge plasma sintering is 100 to 400 ° C / min, and the rate of temperature reduction after sintering is 10 to 300 ° C / min.
9. A method for preparing a fluorescent composite ceramic according to any one of claims 1 to 6, which comprises:

   Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor powder and Al ₂ O ₃ powder are used as raw materials, and uniformly mixed according to mass ratio, and then preformed to form a green body, wherein 0<x<0.3 , 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a <0.1;

   The obtained green body is subjected to hot press sintering to obtain the fluorescent composite ceramic;

   The hot press sintering temperature is 1300 to 1600 ° C, the time is 1 to 10 hours, and the sintering pressure is 20 to 80 MPa.
10. A method for preparing a fluorescent composite ceramic according to any one of claims 1 to 6, which comprises:

    Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor powder and Al ₂ O ₃ powder are used as raw materials, and uniformly mixed according to mass ratio, and then preformed to form a green body, wherein 0<x<0.3 , 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a <0.1;

    The obtained green body is placed in a protective atmosphere or a vacuum condition, and calcined at 1300 to 1600 ° C for 2 to 10 hours to obtain the fluorescent composite ceramic.
11. The preparation method according to any one of claims 7 to 10, wherein the preform is preformed by dry molding or wet molding;

    The dry forming is dry press forming and/or cold isostatic pressing, and the wet forming is grout molding and/or tape casting.
12. The preparation method according to any one of claims 7-11, wherein the Y _3-xyz Ce _x Lu _y Gd _z Al _5-a Ga _a O ₁₂ phosphor has a particle diameter of 1 to 20 μm. The Al ₂ O ₃ powder has a particle diameter of 0.1 to 0.7 μm.
13. The preparation method according to any one of claims 7 to 12, wherein the obtained fluorescent composite ceramic is placed in an air or oxygen atmosphere and heat-treated at 1000 to 1200 ° C for 5 to 20 hours.
14. A lighting fixture comprising an excitation light source, and the fluorescent composite ceramic according to any one of claims 1-6.