WO2019047822A1

WO2019047822A1 - Fluorescent ceramic having characteristic micro-structure, preparation method therefor and application thereof

Info

Publication number: WO2019047822A1
Application number: PCT/CN2018/103938
Authority: WO
Inventors: 刘学建; 李淑星; 姚秀敏; 黄政仁
Original assignee: 中国科学院上海硅酸盐研究所
Priority date: 2017-09-07
Filing date: 2018-09-04
Publication date: 2019-03-14
Also published as: CN109467453A; CN109467453B

Abstract

Disclosed are a fluorescent ceramic having a characteristic micro-structure, a preparation method therefor and application thereof. The fluorescent ceramic is rich in micropores, and the air holes are uniformly distributed in a thickness direction or are gradiently distributed in the thickness direction. The probability of incident light being absorbed by fluorescent crystal particles is increased by means of the scattering action of the pores on light so as to improve the light emission efficiency of the fluorescent crystal particles; also, the light out rate of light at a fluorescent ceramic transmissive face is reduced by means of the design of the uniform distribution or gradient distribution of the pores, so that light is emitted from a reflection face as much as possible and is collected by a detector, thereby improving the light extraction rate.

Description

Fluorescent ceramic with characteristic microstructure and preparation method and application thereof

Technical field

The invention relates to a design and preparation method of a microporous structure inside a fluorescent ceramic, and its application in the field of solid state lighting.

Background technique

Solid-state lighting technology is considered to be a new type of green energy in the 21st century with high efficiency, energy saving, environmental protection and long life. It is mainly used to stimulate the conversion of fluorescent materials into other visible light by using ultraviolet or blue semiconductor chips. The realization of the light mixing technology. In the face of high-power, high-brightness high-end products such as automotive headlamps, aerospace lighting, portable high-brightness projectors, cinema projectors, large-size multimedia public displays, fluorescent materials in solid-state lighting devices are exposed to high incident power density. The problem of heat radiation caused by strong radiation energy. Because organic silica gel is prone to yellowing and even carbonization under long-term heat radiation environment, causing problems such as light decay and color shift, the conventional dispensing package, that is, the phosphor is mixed with the organic silica gel and uniformly coated on the surface of the chip. The way to achieve solid-state lighting seriously reduces the reliability and service life of the device.

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. It has the dual role of packaging material and luminescent material for remote packaging. Fluorescent glass is usually 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 matrix requires extra caution, and it is required not only to be close to the refractive index of the phosphor Moreover, the inevitable interface reaction between the glass substrate and the fluorescent particles during the sintering process often causes destruction of luminescent properties (see Non-Patent Document 1). Compared with fluorescent glass, the fluorescent ceramic obtained by directly sintering the phosphor has obvious advantages in optical properties, thermal properties, mechanical properties, etc., and has become the most promising new fluorescent material form for high-power solid-state illumination. Non-patent document 2).

In addition to reliability, lumen efficiency is another critical technical parameter for solid state lighting. The lumen efficiency of the device is not only related to the luminous efficiency of the fluorescent material itself, but also directly related to its microstructure. This is because the microstructure of the fluorescent ceramic affects the scattering and propagation of light therein, which in turn affects the light extraction efficiency. Zhou Shengming, research team of Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, studied the influence of the second phase of dispersed dispersion in fluorescent ceramics such as Al ₂ O ₃ and MgAl ₂ O ₄ on the lumen efficiency of fluorescent ceramics. The presence of the second phase in the middle can increase the probability that the incident light is absorbed by the illuminating center, and increase the output luminous flux, that is, the lumen efficiency is improved (see Non-Patent Documents 3 and 4).

However, there have been no reports on the microstructure design and preparation methods of 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] Y. Tang, et al " Opt. Express "2015; 23(14): 17923-17928.;

[Non-Patent Document 4] YR Tang, et al. “ Opt. Express ” 2015; 40(23): 5479-5481.;

[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 method and a method for preparing a fluorescent ceramic rich in microporous structure.

Technical solution

From the perspective of optimizing lumen efficiency, the microstructure design of fluorescent ceramics is particularly important. The inventors have studied to introduce pores in the microstructure, and it is expected to produce the following effects: on the one hand, the scattering effect of light by the pores is increased to increase the incident light by fluorescence crystallization. The probability of particle absorption increases the luminous efficiency; on the other hand, through the uniform distribution of the pores or the gradient distribution design, the light emission rate of the light on the transmitting surface of the fluorescent ceramic is reduced, so that the light is emitted as far as possible on the reflecting surface, and is collected by the detector, thereby improving The light extraction rate ultimately achieves the goal of improving device lumen efficiency.

Here, the present invention provides a fluorescent ceramic rich in micropores (specifically, micropores rich in enhanced light scattering), and the pores are uniformly distributed in the thickness direction or distributed in a gradient in the thickness direction.

Preferably, the fluorescent ceramic has a porosity of 1 to 30 vol%, preferably 5 to 20 vol%, and a pore size ranging from 50 to 2,000 nm, preferably from 100 to 1,000 nm.

Preferably, the chemical composition of the fluorescent ceramic is Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ : b wt% Al ₂ O ₃ , where 0 < x < 0.3, 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a < 0.1, x + y + z ≤ 3, 0 ≤ b ≤ 70, preferably 40 ≤ b ≤ 70.

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, and is uniformly distributed or gradiently distributed in the thickness direction through the pores as compared with the completely dense sample. The design of the fluorescent ceramics has improved the light extraction rate and luminous efficiency by more than 110%.

In the present invention, the fluorescent ceramic may be a single-phase or multi-phase fluorescent ceramic, the microstructure of the fluorescent ceramic is rich in micro-pores which enhance light scattering, and the pores have a uniform distribution or a gradient distribution characteristic structure, wherein The single-phase fluorescent ceramic contains only one phase of fluorescent crystal particles, and the complex phase fluorescent ceramic includes a second phase of Al ₂ O ₃ which does not emit light and the above-mentioned fluorescent crystal particles. The invention improves the solid-state illumination by improving the luminous efficiency of the solid-state lighting, by using the pore design in the microstructure of the fluorescent ceramic, and utilizing the scattering effect of the pores on the light to improve the luminous efficiency (>110%) and the light extraction rate (>110%). The efficiency of the device. Specifically, on the one hand, the scattering effect of light by the pores increases the probability that the incident light is absorbed by the fluorescent crystal particles, and improves the luminous efficiency of the fluorescent crystal particles; on the other hand, the light is reduced by the uniform distribution of the pores or the gradient distribution design. The light-emitting rate of the transmissive surface of the fluorescent ceramic causes the light to exit as far as possible on the reflecting surface and is collected by the detector to increase the light extraction rate.

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

Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor powder, Al ₂ O ₃ powder, pore former are mixed and preformed into a green body, wherein 0<x<0.3 , 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a < 0.1, x + y + z ≤ 3, 0 ≤ b ≤ 70, the amount of the pore former accounts for 0.1 to the total mass of the raw material powder 5wt%;

The green body is sintered at 1000 to 1600 ° C to obtain the fluorescent ceramic.

Preferably, the pore former is at least one of polyvinyl alcohol, starch, and dextrin.

In the present invention, the particle diameter of the Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor may be on the order of micrometers, and the particle size of the Al ₂ O ₃ powder may be sub- Micron or nanoscale. As an example, the Y _{3 - x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor may have a particle diameter of 1 to 20 μm, and the particles of the Al ₂ O ₃ powder The diameter can be from 0.1 to 0.7 μm.

Preferably, the preform is preformed by dry forming or wet forming; the dry forming is direct dry forming and/or cold isostatic pressing, and the wet forming is grout molding and / or cast molding and / or 3D printing. Wherein, the pressure of the direct dry press molding may be 10 to 40 MPa, and the pressure of the cold isostatic pressing may be 150 to 250 MPa. Moreover, as an example, the wet forming may include, for example, Y _{3 - x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor powder, Al ₂ O ₃ powder as a raw material, Adding a certain amount of pore-forming agent, after uniformly mixing, adding a dispersing agent and/or a binder and/or a plastic agent, and uniformly grinding the ball to obtain a slurry, which is prepared by grouting, casting, or 3D printing. Forming a green body.

In a preferred embodiment, the sintering is hot press sintering, and the temperature of the hot press sintering is 1000 to 1400 ° C, preferably 1050 to 1300 ° C, the holding time is 0.5 to 5 hours, and the sintering pressure is 10 to 50 MPa. The porosity can be increased by lowering the sintering temperature or the sintering pressure or the holding time.

Moreover, in a preferred embodiment, the sintering is rapid sintering by a discharge plasma, and the temperature of the discharge plasma sintering is 1000 to 1300 ° C, preferably 1000 to 1250 ° C, the holding time is 3 to 10 minutes, and the uniaxial pressure is 20 to 50 MPa. Wherein, the temperature rising rate of the spark plasma sintering may be 100 to 400 ° C / min, and the cooling rate may be 10 to 300 ° C / min after the sintering is completed. The porosity can be increased by lowering the sintering temperature or the sintering pressure.

Moreover, in a preferred embodiment, the sintering is atmospheric pressure sintering, comprising: calcining the obtained green body in an air atmosphere at 400 to 600 ° C, and then in a protective atmosphere or vacuum condition, 1200 to 1600 ° C, preferably 1300 to 1550. Incubate at °C for 1 to 10 hours. Here, the calcination may be carried out at a temperature increase rate of 2 to 10 ° C /min to a temperature of 400 to 600 ° C and to be kept for 1 to 15 hours. The porosity can be increased by lowering the sintering temperature or holding time.

In the present invention, the fluorescent ceramics may be appropriately machined to obtain a desired thickness, or the fluorescent ceramics after mechanical processing (before machining) may be kept at a temperature of 1000 to 1200 ° C in an air or oxygen atmosphere. The heat treatment was performed for 20 h to remove the oxygen vacancies inside the fluorescent ceramic and the graphite were equal, and the optical properties were improved.

In the present invention, Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor is used as the fluorescent crystal particles, a pore former is added, no Al ₂ O _{3 is used} , or an appropriate amount of Al is used. ₂ O _{3 is} used as a matrix material, and after mixing, it is molded, and after sintering, a single-phase or multi-phase fluorescent ceramic having a characteristic microstructure is obtained. The invention makes the pore-forming agent uniformly distributed in the thickness direction or the gradient distribution in the thickness direction when the green body is made, that is, the mass of the pore-forming agent is fixed in the thickness direction or maintains a gradient change in the thickness direction, thereby The pores in the obtained fluorescent ceramic are uniformly distributed in the thickness direction or in a gradient direction in the thickness direction. Moreover, the present invention increases the porosity by reducing the sintering temperature or the sintering pressure or the holding time. The microporous structure-rich fluorescent ceramic designed by the invention not only has the excellent reliability of the fluorescent ceramic, but also has a high light extraction rate, that is, a high lumen efficiency, due to its characteristic microstructure. The sintering method provided by the invention has simple and rapid process, low sintering temperature and easy mass production. The fluorescent ceramic with special microstructure designed by the invention and the synthetic method thereof have important significance for improving the lumen efficiency of high-power solid-state lighting and promoting its industrial development.

In addition, the present invention also provides a lighting fixture comprising the above fluorescent ceramic, specifically comprising an excitation light source, and the above fluorescent 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 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 ceramic of the invention utilizes the scattering effect of the pores on the light to increase the probability that the incident light is absorbed by the fluorescent crystal particles, and improve the luminous efficiency of the fluorescent crystal particles; on the other hand, the uniform distribution of the pores or the gradient distribution design reduces The light extraction rate of the light on the transmissive surface of the fluorescent ceramic causes the light to exit as far as possible on the reflective surface and is collected by the detector to increase the light extraction rate. The fluorescent ceramic is combined with a blue light excitation element, and a high-efficiency, high-brightness white light can be realized by a light mixing technique. The preparation method of the invention has the advantages of low synthesis temperature, simple and rapid process, and easy mass production.

DRAWINGS

1 is an SEM spectrum of a fluorescent ceramic prepared in Example 1;

2 is an SEM spectrum of a fluorescent ceramic prepared in Example 2;

3 is an SEM spectrum of a fluorescent ceramic prepared in Example 3;

4 is an SEM spectrum of a fluorescent ceramic prepared in a comparative example;

Figure 5 is a schematic view showing the flux of reflected light of a fluorescent ceramic;

Figure 6 is a schematic view showing the transmitted light flux of the fluorescent ceramic;

Figure 7 is a schematic view showing the sum of reflected and transmitted light fluxes of a fluorescent ceramic;

Figure 8 is a schematic view showing the distribution of micropores in the thickness direction in the fluorescent ceramic (the circle in the figure represents the distribution of the pores in the thickness direction of the cross section, uniform distribution or gradient distribution);

Figure 9 shows Table 1.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is further described in the following with reference to the accompanying drawings and the accompanying drawings.

The invention relates to a design and a preparation method of a microporous structure inside a fluorescent ceramic. Specifically, the invention adopts a Y3 _{- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor (wherein 0<x<0.3, 0≤y<3, 0≤z<1, 0≤a<0.1) as a fluorescent crystal particle, adding a pore former without adding Al ₂ O ₃ or adding an appropriate amount of Al ₂ O ₃ as a matrix The material, after mixing, is formed, and after sintering, a single-phase or multi-phase fluorescent ceramic having a characteristic microstructure is obtained. The single-phase or multi-phase fluorescent ceramic has a characteristic microporous-rich microstructure, wherein the single-phase fluorescent ceramic contains only one phase of fluorescent crystal particles, and the multi-phase fluorescent ceramic includes non-emitting Al _{2 .} O ₃ second phase and the above-mentioned fluorescent crystal particles. Wherein, the fluorescent crystal particles are formed by doping rare earth elements Ce and Lu, Gd, Ga in the same crystal structure as yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ), and the chemical formula is Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ , where x reflects the doping concentration of rare earth element Ce, y reflects the concentration of Lu substituted Y, z reflects the concentration of Gd substituted Y, and a reflects Ga The concentration of Al is substituted; by adjusting the chemical composition of the functional elements of the fluorescent crystalline particles, fluorescent ceramics having different emission wavelengths can be obtained. The fluorescent ceramic prepared by the invention has more excellent light extraction rate than the conventional fluorescent material, and has great application potential for improving the lumen efficiency of the high-power solid-state lighting device.

In the present invention, the Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor may be either commercially available or self-made. For example, in order to ensure excellent optical properties of the fluorescent ceramic, the present invention can directly use commercial yttrium aluminum garnet-based phosphors having different emission wavelengths (520 to 580 nm) as fluorescent crystal particles. In addition, in the case of using a self-made Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor, the preparation process may include, for example, Y ₂ O ₃ , CeO ₂ , Lu ₂ O _3. Al ₂ O ₃ is used as a raw material, and a yellow phosphor powder of Y _2.1 Ce _0.03 Lu _0.87 Al ₅ O ₁₂ is prepared by a high-temperature solid phase sintering method.

Hereinafter, a method of producing a fluorescent ceramic of the present invention will be specifically described.

First, Y _{3- x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor, Al ₂ O ₃ powder, and pore former are uniformly mixed according to a certain mass ratio, wherein 0<x <0.3, 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a < 0.1, x + y + z ≤ 3, 0 ≤ b ≤ 70, the amount of the pore former accounts for the total mass of the raw material powder 0.1 to 5 wt%. In a preferred embodiment, y+z+a>0. The mixing method may be a dry method or a wet method (such as ball milling, rotary evaporation) mixing or the like.

In the present invention, the content of the Al ₂ O ₃ powder may be from 0 to 70% by weight, preferably from 40 to 70% by weight. The pore forming agent may be polyvinyl alcohol, starch, dextrin or the like, and has a molecular weight of 31,000 to 205,000. The content of the pore former in the raw material mixture may be from 0.1 to 5 wt%.

Next, the mixed raw materials are preformed into a green body. In the present invention, the method of pre-forming the green body may be dry molding, wet molding or the like. Dry forming can be carried out by direct dry pressing, cold isostatic pressing or the like. Wet forming can be carried out by grouting, casting, 3D printing, etc., to obtain a relatively thin blank. Specifically, the pressure of the direct dry press molding may be 10 to 40 MPa, and the pressure of the cold isostatic pressing may be 150 to 250 MPa. Moreover, as an example, the wet forming may include, for example, Y _{3 - x - y - z} Ce _x Lu _y Gd _z Al _{5- a} Ga _a O ₁₂ phosphor powder, Al ₂ O ₃ powder as a raw material, Adding a certain amount of pore-forming agent, after uniformly mixing, adding a dispersant and/or a binder and/or a plastic agent, and uniformly grinding the slurry to obtain a slurry, which is formed by injection molding, casting molding, and 3D printing molding. Wait for the formation of a green 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.

Since the presence of pores enhances light scattering, in order to obtain an optimum light extraction rate, the porosity, pore size range, and pore distribution need to be further optimized. In a preferred embodiment, in order to make the pores in the obtained fluorescent ceramic uniformly distributed in the thickness direction or to exhibit a gradient distribution in the thickness direction, in the green body, the pore former is uniformly distributed in the thickness direction or has a gradient distribution in the thickness direction, that is, The mass of the pore former is fixed in the thickness direction or maintains a gradient change in the thickness direction. As an example, in order to prepare a micro-pores with a gradient distribution of the fluorescent ceramics in the thickness direction, a casting film obtained by casting a slurry of a different pore-forming agent (such as polyvinyl alcohol) is superposed in the thickness direction.

Next, the green body is sintered at 1000 to 1600 °C. In the present invention, a sintering process such as hot press sintering, rapid discharge by discharge plasma, or atmospheric pressure sintering may be employed. Further, the formed green body may be debonded before sintering, and the debonding is carried out by raising the temperature at 450 to 650 ° C at a temperature increase rate of 2 to 5 ° C /min for 5 to 15 hours.

In the case of hot press sintering, the sintering is carried out, for example, in a hot press furnace, and the formed block or unformed powder is placed in a mold, and the uniaxial pressure is 10 to 50 MPa in an inert atmosphere or a vacuum state. The sintering temperature is 1000 to 1400 ° C, preferably 1050 to 1300 ° C, and the holding time of the hot press sintering is 0.5 to 5 h, respectively, and then the furnace is cooled to prepare a fluorescent ceramic. Among them, the heating rate of the hot press sintering may be 5 to 20 ° C / min. The porosity can be increased by lowering the sintering temperature or the sintering pressure or the holding time.

In the case of rapid sintering by discharge plasma, the sintering is carried out, for example, in a discharge plasma rapid sintering furnace, and the formed block or unformed powder is loaded into a mold, and the single axis is under an inert atmosphere or a vacuum state. The pressure is 20 to 50 MPa, the sintering temperature is 1000 to 1300 ° C, preferably 1000 to 1250 ° C, and the holding time of the rapid sintering of the discharge plasma is 3 to 10 min, and then the furnace is cooled to prepare a fluorescent ceramic. 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 10 to 300 ° C / min. The porosity can be increased by lowering the sintering temperature or the sintering pressure.

In the case of atmospheric pressure sintering, the sintering is carried out, for example, in a high-temperature sintering furnace, and the obtained green body is pre-fired in an air atmosphere at 400 to 600 ° C, in an inert atmosphere (protective atmosphere such as argon gas, nitrogen gas, etc.) or vacuum. In the state, the green body obtained after calcination is placed in a crucible, and then placed in a sintering furnace at a sintering temperature of 1200 to 1600 ° C, preferably 1300 to 1550 ° C, and the heating rate may be 10 to 20 ° C / min. The time is 1 to 10 h, and then the furnace is cooled to obtain a fluorescent ceramic. Here, the calcination may be carried out at a temperature increase rate of 2 to 10 ° C /min to a temperature of 400 to 600 ° C and to be kept for 1 to 15 hours. The porosity can be increased by lowering the sintering temperature or holding time. From the viewpoint of industrial application and mass production, it is preferred to use a sintering method of atmospheric pressure sintering.

The fluorescent ceramic prepared by the invention emits a broad-band emission spectrum with a peak wavelength in the range of 520-580 nm under blue light excitation of 440-470 nm. In a preferred embodiment, the peak wavelength is between 540 and 560. Wideband emission spectrum in the nm range. The porosity in the fluorescent ceramic ranges from 1 to 30 vol%, preferably from 5 to 20 vol%; the pore size ranges from 50 to 2000 nm, preferably from 100 to 1000 nm, and the porosity is measured by a mercury intrusion method. Through the pore design in the microstructure of the fluorescent ceramic, the scattering effect of light by the pores is used to improve the luminous efficiency and the light extraction rate. The fluorescent ceramic of the present invention has an excellent light extraction rate (>110%), which is superior to a dense fluorescent ceramic containing no pores.

In the present invention, the fluorescent ceramic can be appropriately machined to obtain a desired thickness. In practical applications, the thickness of the fluorescent ceramic sheet is generally about 0.1 to 0.2 mm. The ceramic sheets prepared by wet grouting or casting or 3D printing combined with atmospheric pressure sintering can meet the practical application needs without or with a small amount of mechanical processing, mainly by grinding, polishing, etc. The treatment method adjusts the thickness and surface roughness of the obtained fluorescent ceramic. In addition, the fluorescent ceramics after mechanical processing (before machining) can be heat-treated at 1000-1200 ° C for 5-20 h in air or oxygen atmosphere to remove oxygen vacancies and graphite in the fluorescent ceramics. Its optical properties.

The above-described fluorescent ceramics designed by the present invention can be used as a luminescent material in solid-state illumination, for example, 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 may be 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.

Advantages of the invention:

Microstructure and performance characterization of fluorescent ceramics: Field-scanning scanning electron microscopy (SEM, S-4800, Hitachi) was used to detect the characteristic microporous structure inside the fluorescent ceramics; laboratory-built equipment was used to test the transmitted light flux of fluorescent ceramics under blue laser excitation. And reflected light flux.

Embodiments of the invention

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 following specific process parameters and the like are also only one example of a suitable range, and those skilled in the art can make a suitable range selection by the description herein, and are not limited to the specific numerical values exemplified below.

实施例Example 11

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (100 g) and 2 g of polyvinyl alcohol were placed in a high-purity alumina ball mill, and high-purity alumina balls (75 g) having a diameter of 5 mm were respectively added. Anhydrous ethanol (80 g) was 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 in a reagent bottle for use.

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 30 MPa, the heating rate was 300 °Cmin ^-1 , the highest sintering temperature was 1000 °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 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 sample. The SEM spectrum of the sintered fluorescent ceramics is shown in Fig. 1. The ceramic microstructure contains many micropores with a porosity of 18%.

Under the excitation of the incident blue laser, the luminous flux of the fluorescent ceramic on the reflecting surface is 242.97 lumens (lm), the outgoing light flux on the transmitting surface is 113.32 lm, and the total luminous flux of the reflecting surface and the transmitting surface is 356.29. Lm. Obviously, due to the scattering effect of the micro-pores, the emitted light is concentrated on the reflecting surface and collected by the detector, thereby improving the light extraction rate of the outgoing light on the reflecting surface.

实施例Example 22

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (39 g), Al ₂ O ₃ raw material (61 g), 0.1 g dextrin were placed in an alumina ball mill jar, and high purity oxidation of 5 mm in diameter was added respectively. After the aluminum ball (75 g) and absolute ethanol (80 g) were placed in a planetary ball mill for 24 h, the slurry was placed in an oven at 80 ° C for 12 h to be fully dried, then ground, passed through a 100 mesh sieve, and placed. Spare in the reagent bottle.

After the powder is directly dry-formed (10 MPa) and cold isostatically pressed (200 MPa), it is heated to 1400 ° C at a heating rate of 10 ° C min ^-1 by a hot pressing sintering process, under 40 MPa sintering pressure. A composite phase fluorescent ceramic is prepared.

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 microstructure of the fluorescent ceramics is shown in Fig. 2. Due to the higher sintering temperature and longer holding time, the fluorescent crystal particles and Al ₂ O ₃ in the microstructure have larger particle diameters and are substantially completely dense.

Under the excitation of the incident blue laser, the luminous flux of the fluorescent ceramic on the reflecting surface is 167.82 lm, and the outgoing luminous flux on the transmitting surface is 178.83. The total luminous flux of lm, reflective and transmissive surfaces is 346.65 lm. Obviously, due to the weak scattering effect in the microstructure, the exiting flux of the outgoing light on the transmitting surface and the reflecting surface is substantially equivalent (the transmissive surface is even higher than the reflecting surface), which is not conducive to the improvement of the light extraction rate of the emitted light at a certain fixed surface.

实施例Example 3 3

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (100 g), 0.1 g of starch were placed in an alumina ball mill jar, and high-purity alumina spheres (75 g) with a diameter of 5 mm were added, respectively, and high-purity without The water ethanol (80 g) was ball milled on a planetary ball mill for 24 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 in a reagent bottle for use.

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 45 MPa, the heating rate was 300 ° Cmin ^-1 , the highest sintering temperature was 1300 ° 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 a cooling rate of 300 ° C min ^-1 .

The processed sample was placed in a muffle furnace at 1000 ° C for 10 h for heat treatment to obtain a fluorescent ceramic sample. The SEM image of the sintered fluorescent ceramic is shown in Fig. 3. The fluorescent particles in the ceramic are closely packed, and the morphology of the initial fluorescent crystal particles is basically maintained.

实施例Example 44

Y _2.2 Ce _0.05 Lu _0.75 Al _4.8 Ga _0.2 O ₁₂ phosphor (100 g) and 2 g of polyvinyl alcohol were placed in a high-purity alumina ball mill jar, and high-purity alumina balls (75 g) having a diameter of 5 mm were respectively added. Anhydrous ethanol (80 g) was placed in a planetary ball mill for 24 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 in a reagent bottle for use.

The uniformly mixed raw material powder was sintered by the rapid plasma sintering technique, and 0.7 g of the raw material powder was weighed each time, and placed in a graphite mold having an inner diameter of 15 mm, and a graphite paper was 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 30 MPa, the heating rate was 300 °Cmin ^-1 , the highest sintering temperature was 1000 ° 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 a cooling rate of 300 ° C min ^-1 .

The processed sample was placed in a muffle furnace at 1000 ° C for 10 h for heat treatment to obtain a fluorescent ceramic sample.

Under the excitation of the incident blue laser, the luminous flux of the fluorescent ceramic on the reflecting surface is 230.23 lumens (lm), the outgoing light flux on the transmitting surface is 110.54 lm, and the total luminous flux of the reflecting surface and the transmitting surface is 340.77. Lm. Obviously, due to the scattering effect of the micro-pores, the emitted light is concentrated on the reflecting surface and collected by the detector, thereby improving the light extraction rate of the outgoing light on the reflecting surface.

实施例Example 55

Y _2.2 Ce _0.05 Gd _0.75 Al _4.8 Ga _0.2 O ₁₂ phosphor (100 g) and 2.5 g of starch were placed in a high-purity alumina ball mill jar, respectively, and high-purity alumina balls (75 g) having a diameter of 5 mm were added and anhydrous. Ethanol (80 g) was placed in a planetary ball mill for 24 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 in a reagent bottle for use.

The uniformly mixed raw material powder was sintered by the rapid plasma sintering technique, and 0.7 g of the raw material powder was weighed each time, and placed in a graphite mold having an inner diameter of 15 mm, and a graphite paper was 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 30 MPa, the heating rate was 200 ° Cmin ^-1 , the highest sintering temperature was 1050 ° 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 a cooling rate of 300 ° C min ^-1 .

Under the excitation of the incident blue laser, the luminous flux of the fluorescent ceramic on the reflecting surface is 236.78 lumens (lm), the outgoing light flux on the transmitting surface is 130.11 lm, and the total luminous flux of the reflecting surface and the transmitting surface is 366.89. Lm. Obviously, due to the scattering effect of the micro-pores, the emitted light is concentrated on the reflecting surface and collected by the detector, thereby improving the light extraction rate of the outgoing light on the reflecting surface.

对比例Comparative example

Commercial Y ₃ Al ₅ O ₁₂ :Ce yellow phosphor (100 g) was placed in an alumina ball mill jar, and high-purity alumina spheres (75 g) and high-purity absolute ethanol (80 mm) were added, respectively. g) Placed on a planetary ball mill for 24 h, the slurry was placed in an oven at 80 ° C for 12 h, then ground, then ground, passed through a 100 mesh nylon screen, and placed in a reagent bottle for use.

The powder after mixing is directly dry-formed (40 MPa) and cold isostatically pressed (200 MPa) to obtain a green body.

The formed green body was heated to 1000 ° C at a heating rate of 10 ° C / min and calcined for 4 hours, placed in a normal pressure sintering furnace, and raised to 1600 at a heating rate of 10 ° C min ^-1 under a vacuum atmosphere. After incubating at °C for 10 h, after the end of the heat preservation, the fluorescent ceramic was obtained by cooling with the furnace.

The upper and lower surfaces of the sample obtained by sintering 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 1 h for heat treatment to obtain a fluorescent ceramic sample.

The microstructure of the fluorescent ceramics is shown in Fig. 4. Since the pore-forming agent is not added and the sintering temperature and the long holding time are high, the particle size of the fluorescent crystal particles in the microstructure is extremely large, and the grain boundary of the light scattering can be promoted. Very low stomatal content.

Under the excitation of the incident blue laser, the luminous flux of the fluorescent ceramic on the reflecting surface is 122.83 lm, and the outgoing luminous flux on the transmitting surface is 135.42. The total luminous flux of lm, reflective and transmissive surfaces is 258.25 lm. Since the size of the fluorescent crystal particles is extremely large, the grain boundaries are extremely small, the outgoing lumens of the emitted light on the transmitting surface and the reflecting surface are reduced, and the number of outgoing lumens of the transmitting surface and the reflecting surface is equivalent, which is not conducive to the improvement of the overall light lumen. It is not conducive to the improvement of the light extraction rate of the emitted light at a certain fixed surface.

Table 1 shows the optical performance parameters of the fluorescent ceramics prepared by the present invention.

Industrial applicability:

The invention designs and manufactures a fluorescent ceramic rich in microporous structure, which not only has excellent reliability of the fluorescent ceramic, but also the design of the microporous structure promotes the improvement of the light extraction rate. The preparation method is simple and rapid, and in particular, the method of casting molding or grouting molding or 3D printing molding combined with atmospheric pressure sintering is expected to realize mass production of fluorescent ceramic sheets. The designed fluorescent ceramic can be combined with a blue light emitting element to achieve high lumen solid state illumination with high lumen efficiency. It is expected that this fluorescent ceramic and its preparation method will be widely used to promote the rapid development of the solid-state lighting industry.

Claims

A single-phase or multi-phase fluorescent ceramic characterized in that the fluorescent ceramic is rich in micropores, and the pores are uniformly distributed in the thickness direction or distributed in a gradient along the thickness direction.
The fluorescent ceramic according to claim 1, wherein the fluorescent ceramic has a porosity of 1 to 30 vol%, preferably 5 to 20 vol%, and a pore size of 50 to 2,000 nm, preferably 100 to 1,000 nm.
The fluorescent ceramic according to claim 1 or 2, wherein the chemical composition of the fluorescent ceramic is Y 3- x - y - z Ce x Lu y Gd z Al 5- a Ga a O 12 : b wt% Al 2 O 3 , where 0<x<0.3, 0≤y< 3 , 0≤z<1, 0≤a<0.1, x+y+z≤3, 0≤b≤70, preferably 40≤b≤70 .
The method for preparing a fluorescent ceramic according to any one of claims 1 to 3, characterized by comprising:

Y 3- x - y - z Ce x Lu y Gd z Al 5- a Ga a O 12 phosphor, Al 2 O 3 powder, pore former are mixed and preformed into a green body, wherein 0<x<0.3 , 0 ≤ y < 3, 0 ≤ z < 1, 0 ≤ a < 0.1, x + y + z ≤ 3, 0 ≤ b ≤ 70, the amount of the pore former accounts for 0.1 to the total mass of the raw material powder 5wt%;

The green body is sintered at 1000 to 1600 ° C to obtain the fluorescent ceramic.
The method according to claim 4, wherein the pore forming agent is at least one of polyvinyl alcohol, starch, and dextrin.
The preparation method according to claim 4 or 5, wherein the preform is preformed by dry molding or wet molding;

The dry molding is direct dry press molding and/or cold isostatic pressing, and the wet molding is at least one of slip casting, tape casting, and 3D printing.
The preparation method according to any one of claims 4 to 6, wherein the sintering is hot press sintering, the temperature of the hot press sintering is 1000 to 1400 ° C, the holding time is 0.5 to 5 hours, and sintering is performed. The pressure is 10 to 50 MPa.
The preparation method according to any one of claims 4 to 6, wherein the sintering is rapid sintering by a discharge plasma, and the temperature of the discharge plasma sintering is 1000 to 1300 ° C, and the holding time is 3 to 10 minutes. The uniaxial pressure is 20 to 50 MPa.
The preparation method according to any one of claims 4 to 6, wherein the sintering is atmospheric pressure sintering, comprising: pre-sintering the obtained green body in an air atmosphere at 400 to 600 ° C, in a protective atmosphere or The temperature is maintained at 1200 to 1600 ° C for 1 to 10 hours under vacuum.
A lighting fixture comprising an excitation light source and the fluorescent ceramic according to any one of claims 1 to 3.