CN109020509B

CN109020509B - Luminescent ceramic and preparation method thereof

Info

Publication number: CN109020509B
Application number: CN201710433530.9A
Authority: CN
Inventors: 李乾; 陈雨叁; 许颜正
Original assignee: Appotronics Corp Ltd
Current assignee: Shenzhen Appotronics Corp Ltd
Priority date: 2017-06-09
Filing date: 2017-06-09
Publication date: 2021-07-06
Anticipated expiration: 2037-06-09
Also published as: WO2018223544A1; CN109020509A

Abstract

The invention relates to a luminescent ceramic and a preparation method thereof. The luminescent ceramic of the present invention comprises Al₂O₃Matrix, ZrO₂Particles and phosphor particles. The luminescent ceramic of the present invention can be obtained by a solid-phase method or a liquid-phase method.

Description

Luminescent ceramic and preparation method thereof

Technical Field

The invention relates to a luminescent ceramic and a preparation method thereof.

Background

The technology of exciting the fluorescent material by the blue laser to obtain the visible light is taken as a brand new light source technology, the application of the technology in the field of laser display is remarkably advanced and accepted by the market, and the related technology is continuously paid attention to. The hot spot and difficulty of the current research are mainly to develop novel fluorescent materials (wavelength conversion materials and luminescent materials) aiming at the characteristics of laser excited fluorescent powder, and these materials must have excellent properties, such as high optical conversion efficiency and high brightness, and the unit light-emitting area can bear the irradiation of laser with larger power, and has high heat-conducting property, long service life, and the like.

With the improvement of requirements, the traditional silica gel packaging fluorescent powder technology and the glass packaging fluorescent powder technology cannot meet the requirements of high-end products, the bearing temperature of silica gel cannot exceed 200-; the thermal conductivity of the materials for silica gel packaging and glass packaging is generally not more than 2W/(m.k), and the materials cannot bear the irradiation of high-power or even ultrahigh-power laser in a fixed excitation scheme (corresponding to a rotary excitation scheme).

Luminescent ceramics are an ideal choice because they have better properties of heat resistance and thermal conductivity than silica gel and glass encapsulated phosphors. However, conventional YAG (i.e., yttrium aluminum garnet (Y))₃Al₅O₁₂) Pure phase luminescent ceramics are also weaker in luminescent properties than silica gel and glass encapsulation; especially, in ultra-thin packaging, the light efficiency loss caused by the total reflection of the interface is very large. Therefore, other high thermal conductivity ceramic materials are used to encapsulate the phosphor, such as Al₂O₃YAG-Al prepared by packaging YAG fluorescent powder₂O₃(PIA, Phosphor In Alumina), which can obtain more excellent performance than pure phase YAG luminescent ceramics, is a direction worthy of intensive research.

Since the luminescent ceramics tend to be applied more precisely, Al is prepared₂O₃After the luminescent ceramic of the fluorescent powder is packaged, a series of processes such as cutting, grinding, polishing, cutting, coating, welding and the like are needed, so that the requirements on the mechanical properties of the luminescent ceramic, particularly the toughness of the luminescent ceramic, are high.

Therefore, how to obtain a luminescent ceramic having both optical and mechanical properties is an important issue to be studied.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above problems. It is therefore an object of the present invention to provide luminescent ceramics which simultaneously satisfy the requirement that the toughness of the luminescent ceramics is increased without significantly affecting the optical properties of the luminescent ceramics.

Means for solving the problems

The invention provides a luminescent ceramic, which is characterized by comprising Al₂O₃Matrix, ZrO₂Particles and phosphor particles.

The luminescent ceramic of the present invention, wherein the phosphor particles and the ZrO₂Particles are uniformly dispersed in the Al₂O₃In a matrix. Further, the ZrO₂Particles are dispersed in the Al₂O₃Between the grain boundaries of the matrix.

The luminescent ceramic according to the present invention, wherein the ZrO₂The content of the particles is Al₂O₃0.05 to 5 mass%, preferably 0.2 to 3 mass%, more preferably 0.5 to 1 mass% of the matrix mass.

The luminescent ceramic of the present invention, wherein the phosphor particles are in contact with the Al₂O₃The mass ratio of the matrix is 1: 4-9: 1, preferably 1: 4-3: 1, and more preferably 1: 3-1: 1.

The luminescent ceramic according to the present invention, wherein the ZrO₂The particle size of the particles is 0.05-1 μm, preferably 0.05-0.7 μm, particularly preferably 0.05-0.35 μm, the particle size of the phosphor particles is 10-50 μm, preferably 10-30 μm, particularly preferably 10-25 μm, and the Al is₂O₃The grain size of the crystal grains of the matrix is 0.05-5 μm, preferably 0.15-5 μm, and particularly preferably 0.15-3 μm; and/or, the ZrO₂The particle size of the raw material powder of the particles is 0.05-0.7 mu m, preferably 0.05-0.2 mu m, the particle size of the raw material powder of the fluorescent powder particles is 10-25 mu m, preferably 15-17 mu m, and the Al is₂O₃The particle size of the raw material powder is 0.05 to 1 μm, preferably 0.1 to 0.3 μm.

The luminescent ceramic further comprises a sintering aid, and the sintering aid is selected from Y₂O₃、MgO、CaO、SiO₂、TiO₂、BaO、CaF₂、BaF₂Preferably Y, is₂O₃And/or MgO, more preferably Y₂O₃。

In addition, the invention also provides a preparation method of the luminescent ceramic, which is characterized by comprising the following steps:

step 1: containing Al₂O₃Matrix, ZrO₂A step of preparing a mixed powder of the particles and the phosphor particles;

step 2: and pressing and sintering the mixed powder to obtain the luminescent ceramic.

The preparation method according to the present invention, wherein the step 1 comprises the steps of:

step a: the Al is₂O₃Matrix and the ZrO₂A step of preparing a mixed powder of the particles and optionally the sintering aid;

step b: and mixing the mixed powder with the fluorescent powder particles, ball-milling, drying and sieving.

The preparation method according to the present invention, wherein the step a may be replaced with a step a', which comprises: adding the Al₂O₃Suspension of starting powder of matrix with ZrO₂A step of mixing and co-precipitating a solution of the precursor of (a) and a solution of the precursor of the optional sintering aid; and the steps of centrifuging, washing, drying, calcining and sieving the obtained product.

step I: mixing Al₂O₃Mixed suspension of raw material powder and phosphor powder and ZrO₂A step of mixing the solution of the precursor of (a) and the solution of the precursor of the optional sintering aid, followed by coprecipitation;

step II: and (4) carrying out centrifugal separation, washing, drying, calcining and sieving on the product obtained in the step I.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, by adding Al to₂O₃Adding proper amount of small-grain-size ZrO into luminescent ceramic for packaging fluorescent powder₂So that the phosphor particles and ZrO₂The particles are uniformly dispersed in Al₂O₃In the matrix, not only the toughness of the luminescent ceramic can be increased, but also the optical properties of the luminescent ceramic are not adversely affected. And, ZrO₂And also acts as scattering particles, acting to homogenize incident light. Therefore, the luminescent ceramic has the excellent characteristics of high luminous efficiency, high thermal conductivity and adjustable blue light transmittance, and can be applied to high-performance laser light sources, in particular to precise laser light source systems.

Drawings

FIG. 1 is a schematic structural diagram of a luminescent ceramic according to the present invention.

Fig. 2 is a scanning electron micrograph of the sample obtained in example 1.

Detailed Description

The luminescent ceramic of the present invention and the method for preparing the same are explained in more detail by specific embodiments below.

The luminescent ceramic of the present invention comprises Al₂O₃Matrix, ZrO₂Particles and phosphor particles. Wherein the phosphor particles with large particle size are uniformly dispersed in Al₂O₃ZrO of small particle size in the matrix₂The particles are located in Al₂O₃Between the grain boundaries of the matrix.

FIG. 1 is a schematic structural diagram of a luminescent ceramic according to the present invention. Wherein 1 represents Al₂O₃Matrix, 2 represents ZrO₂Particles, 3 denotes phosphor particles. As shown in FIG. 1, the luminescent ceramic of the present invention is characterized by the fact that Al having fine crystal grains is used₂O₃Phase as matrix, larger phosphor particles uniformly dispersed in Al₂O₃In the matrix, smaller ZrO₂The particles are located in Al₂O₃Between the grain boundaries of the matrix. And, phosphor particles are coated with Al₂O₃The grains of the matrix are continuously surrounded. The fluorescent powder particles in the ceramic can absorb exciting light to emit excited light; specifically, the light can be excited by blue light to emit yellow visible light; dense and fine-grained Al₂O₃The matrix has good light transmission performance, and excited visible light can pass through Al₂O₃The matrix emerges outside the ceramic. Smaller ZrO₂The particles can act to increase the toughness of the luminescent ceramic without adversely affecting the luminescent properties of the luminescent ceramic. And, ZrO₂And also acts as scattering particles, acting to homogenize incident light.

The luminescent ceramic according to the present invention, wherein the ZrO₂The particle size of the particles is 0.05 to 1 μm, preferably 0.05 to 0.7 μm, and particularly preferably 0.05 to 0.35. mu.m.

The luminescent ceramic provided by the invention is characterized in that the particle size of the fluorescent powder particles is 10-50 μm, preferably 10-30 μm, and particularly preferably 10-25 μm.

The luminescent ceramic according to the present invention, wherein the Al₂O₃The grain size of the crystal grains of the matrix is 0.05 to 5 μm, preferably 0.15 to 5 μm, and particularly preferably 0.15 to 3 μm.

The mechanism of the optical and mechanical properties of the luminescent ceramic of the present invention will be described below. In the present invention, Al is produced₂O₃When the luminescent ceramic of the fluorescent powder is packaged, a proper amount of ZrO is added₂Nano-powder of ZrO using₂The tetragonal phase t-ZrO of the crystal grains in the processes of temperature rise and temperature drop₂And monoclinic phase m-ZrO₂The luminescent ceramic is toughened through the microcrack phase transformation toughening. I.e. m-ZrO when the temperature passes about 1200 ℃ during heating₂Conversion to t-ZrO₂The volume is contracted; t-ZrO at a temperature of about 1000 ℃ during cooling₂Conversion to m-ZrO₂And the volume expands. ZrO (ZrO)₂The process of volume contraction and expansion can generate tiny cracks or elastic after-effect stress in the ceramic matrix, and when the ceramic is broken under stress or is about to break, the microcracks or the stress can absorb or offset the stress causing the ceramic to break, so that the ceramic can bear larger stress and is not easy to break, and the toughness of the ceramic is enhanced. ZrO (ZrO)₂The small particle size and the dispersion of the particles are the key to the realization of the toughening effect. In addition, ZrO₂Is a light-transmitting Al₂O₃The white opaque component of the matrix, which normally affects Al₂O₃Light transmission of the substrate. In the present invention, surprisingly by reacting ZrO₂The particle size of (2) is small, the addition amount is small, and the influence on the incidence of blue light and the emergence of yellow light is small. In addition, ZrO₂As the white particles, they can function to scatter incident light to make the incident light uniform, and they do not substantially absorb light, causing no loss of light. Thus, the final effect is ZrO₂The addition of the particles does not significantly affect the optical properties of the luminescent ceramic, ZrO₂And can also significantly enhance the mechanical properties of luminescent ceramics and act as scattering particles to homogenize incident lightAnd (4) acting.

In the luminescent ceramic of the present invention, ZrO₂Is Al in an amount of₂O₃0.05 to 5 mass%, preferably 0.2 to 3 mass%, more preferably 0.5 to 1 mass% of the matrix mass. When ZrO₂When the content of (B) is less than 0.05% by mass, the toughening effect is not significant. When ZrO₂When the content of (3) is more than 5% by mass, ZrO in the luminescent ceramic₂The phase will be more obvious, the reflection of the incident blue light will be more obvious, at this time, the blue light content in the light emitted by the yellow luminescent ceramic will be increased, the yellow light content will be reduced, and the overall luminous efficiency of the luminescent ceramic will be reduced. When ZrO₂When the content of (a) is 0.05 to 5 mass%, preferably 0.2 to 3 mass%, not only can a toughening effect be achieved without adversely affecting the luminous efficiency of the luminescent ceramic, but also the luminescent ceramic can be used as scattering particles to homogenize incident light.

In addition, when a ceramic emitting uniform white light is required, ZrO may be increased₂To increase the number of white spots. At this time, ZrO₂The content of (b) may be a higher value within the above range, for example, 4 to 5 mass%. ZrO (ZrO)₂The light source plays a role of scattering particles, and the emergent white light can be more uniform.

The phosphor is not particularly limited, and phosphors commonly used in the field of luminescent ceramics can be used. In the present invention, the phosphor preferably used is selected from Ca₃(Al,Sc)₂Si₃O₁₂、(Gd,Tb,Y,Lu)₃(Al,Ga)₅O₁₂、Y₃Mg₂AlSi₂O₁₂And doped with Ce³⁺Wherein Y is preferred₃Al₅O₁₂Doping with Ce³⁺Ce as phosphor powder of (YAG)³⁺And (3) fluorescent powder.

Phosphor particles and Al₂O₃The mass ratio of the matrix is 1: 4-9: 1, preferably 1: 4-3: 1, and more preferably 1: 3-1: 1. In addition, the content of the phosphor particles is Al₂O₃Matrix, ZrO₂15 to 90 mass%, preferably 15 to 50 mass%, of the total amount of the particles, phosphor particles and sintering aid, if present.

As described above, ZrO₂The reduction of the particle size of the particles is one of the key factors for the realization of the toughening effect. In the present invention, ZrO₂The particle size of the raw material powder is 0.05 to 0.7 μm, preferably 0.05 to 0.2 μm, and particularly preferably 0.05 to 0.1. mu.m. If ZrO of₂The particle size of the raw material powder is too large, white spots can be formed in the luminescent ceramic, and the toughening effect is poor. Here, ZrO is to be noted₂The particle size range of the raw material powder is slightly smaller than ZrO in the luminescent ceramic₂The particle size range of (a); it can be understood that ZrO when used as a raw material₂Partial agglomeration of the raw material powder may occur during the entire preparation process, and partial ZrO may occur during the sintering process₂Abnormal growth of crystal grains without inhibition; thus, ZrO in luminescent ceramics₂May be slightly larger than ZrO₂The particle size of the raw material powder; but based on the uniformity of the dispersion, ZrO₂The variation in particle size is not too significant.

In addition, Al₂O₃The particle size of the raw material powder is 0.05 to 1 μm, preferably 0.1 to 0.3 μm. The particle size of the phosphor powder is 10-25 μm, preferably 15-17 μm. It should be noted that fine-grained Al₂O₃Has good mechanical property in luminescent ceramics, and the strength and the toughness of the luminescent ceramics are superior to those of Al with large crystal grains₂O₃A substrate. In general, part of Al is generated due to abnormal growth of grains during agglomeration and sintering₂O₃The particle size of the raw material powder is increased by 3 to 5 times. It will be appreciated that this phenomenon is equally applicable to the other components of the present invention. However, in the present invention, Al having a small particle size is used₂O₃ZrO added to the starting powder during the preparation₂Simultaneously play a role in inhibiting Al₂O₃Excessive (abnormal) growth, and thus has a positive effect on enhancing the strength and toughness of the luminescent ceramic.

When the alumina grain size falls within the scope of the present invention, sintering is facilitated at lower temperatures. For example, when YAG: Ce is used³⁺When the fluorescent powder is used as the fluorescent powder of the invention, the melting point of YAG is 1970 ℃, and Al₂O₃Has a melting point of 2000 ℃ and is intended to form the hair described aboveOptical ceramic material, requires Al₂O₃The YAG is not sintered or is sintered in a small amount in the liquid phase, and only a very small amount of phase migration is generated. Thus Al in the raw material₂O₃The powder is superfine powder with a nanometer-level high specific surface area, and the average particle size is 0.05-1 μm, preferably 0.1-0.3 μm. Selecting small-grain-size nano Al₂O₃The powder can be sintered into compact Al at 1500 ℃ under the condition of hot-pressing sintering₂O₃Ceramics, much lower than the melting point of large-grain YAG, can realize Al₂O₃The sintering is finished without the YAG participating in the sintering, so that the appearance of the main particles is not changed.

In addition, the luminescent ceramic of the present invention may comprise a sintering aid. Examples of the sintering aid are not particularly limited, and aids commonly used in the art may be used. For example, the sintering aid may be selected from Y₂O₃、MgO、CaO、SiO₂At least one of (1). Among them, Y is preferred₂O₃And/or MgO, more preferably Y₂O₃As a sintering aid in the present invention. The content of the sintering aid is Al₂O₃0.05 to 5 mass%, preferably 0.05 to 3 mass%, more preferably 0.5 to 1 mass% of the matrix mass.

When using Y₂O₃When the powder particles are used as an auxiliary agent, the powder particles can be used as a sintering auxiliary agent of luminescent ceramics to promote liquid phase sintering and can also be used as ZrO₂Stabilizer of (4) ZrO₂The phase change behavior of (a) is less drastic, being a relatively moderate volume change.

MgO and Y₂O₃Can be used as an auxiliary agent for sintering luminescent ceramics, can obviously improve liquid phase sintering and reduce sintering temperature. Y is₂O₃MgO are minor amounts of auxiliaries if their amounts are relative to Al₂O₃If the mass of the matrix is less than 0.05 mass%, the effect of the auxiliary agent is reduced; if their content is more than 5 mass%, Al is affected₂O₃The transparency of the matrix. ZrO (ZrO)₂、Y₂O₃MgO, and Al are required₂O₃Nano-powder particleThe particles are mixed well to function most effectively.

In addition, the relative compactness of the luminescent ceramic is 4.1-4.31 g/cm³. The higher the relative density is, the higher the thermal conductivity, the light efficiency and the mechanical property are, and particularly the thermal conductivity is greatly improved.

The preparation of the luminescent ceramic of the present invention is further described below.

As described above, it is necessary to use ZrO₂And sintering aid and Al, if present₂O₃The matrix powder is mixed sufficiently uniformly to function most effectively. Therefore, the method for producing the luminescent ceramic of the present invention is not particularly limited as long as the powders can be uniformly mixed.

Specifically, the preparation method of the luminescent ceramic comprises the following steps:

Step 1

In step 1, a solid phase method or a liquid phase method may be used. The liquid phase method further includes a sol-gel method, a coprecipitation method, an alkoxide hydrolysis method, etc., and among them, the coprecipitation method is particularly preferable.

The above step 1 will be described below by taking a solid phase method and a coprecipitation method as examples.

< solid phase method >

In the present invention, Al is contained by the solid phase method₂O₃Matrix, ZrO₂The method of mixing powder of particles and phosphor particles includes the steps of:

step a: al (Al)₂O₃Matrix and ZrO₂A step of preparing a mixed powder of the particles and optionally the sintering aid;

step b: mixing the mixed powder with fluorescent powder, ball-milling, drying and sieving.

Step a

Al₂O₃Matrix and ZrO₂The preparation of a mixed powder of particles and optionally a sintering aid can be obtained by a process comprising: mixing Al₂O₃Starting powder of matrix and ZrO₂A step of mixing and ball milling (referred to as first ball milling) powders of raw materials of the particles and raw materials of the optional sintering aid.

Specifically, Al is added₂O₃Starting powder of matrix and ZrO₂Putting powder of raw materials of the particles and raw materials of optional sintering aids into a polytetrafluoroethylene ball milling tank, adding a proper amount of ethanol as a grinding solvent, adding a proper amount of ceramic dispersant as a dispersant, and carrying out ball milling by using zirconia balls with ultralow attrition loss rate for 1-72 h, preferably 24-36 h. Thus, Al is obtained₂O₃Matrix and ZrO₂And optionally a sintering aid. The first ball milling is to make Al₂O₃Starting powder of matrix and ZrO₂The raw material powder of the particles and the raw material powder of the optional sintering aid are mixed and ground, and thus the rotation speed of the ball mill is not particularly limited.

The dispersant is not particularly limited, and a dispersant commonly used in the art may be used. Examples thereof include: inorganic salts such as sodium silicate, sodium tripolyphosphate, sodium hexametaphosphate, and the like; lower organic substances such as sodium stearate, sodium citrate, sodium alkylsulfonate and the like; polymers such as polyacrylic acid and its salts, polyvinyl alcohol, and the like.

Step b

Al to be obtained by the above step a₂O₃Matrix and ZrO₂The mixed powder of the particles and the optional sintering aid is mixed with the phosphor particles, and then ball milling is performed at a low speed (referred to as secondary ball milling), wherein the ball milling time is 10-120 min, preferably 30-50 min. The revolution of ball milling is 30-100 r/min. It should be noted that the main purpose of the low speed is to control the impact force on the phosphor particles during ball milling, so as to avoid the damage to the surface morphology of the phosphor particles.

The first ball milling time is longerTo mix Al thoroughly₂O₃Powder and ZrO₂Particles and optionally sintering aid powder, ZrO₂The powder of the particles and optionally the sintering aid must be mixed with Al₂O₃The powders are fully mixed to ensure even diffusion. The secondary ball milling time is shorter because the fluorescent powder has larger particles and is easier to disperse, and if the ball milling time is too long, the surface morphology of the crystal grains of the fluorescent powder is easy to damage, and the luminous performance is influenced.

After the ball milling is finished, drying at constant temperature in vacuum to obtain dry powder. And calcining the dry powder in a muffle furnace at 500-650 ℃ to remove organic components in the powder. Then, the calcined powder was sieved through 80 mesh, 150 mesh, and 200 mesh sieves to obtain a high-fluidity raw material powder.

Step a described above, i.e., Al₂O₃Matrix and ZrO₂The preparation of the mixed powder of particles and optionally sintering aid can also be obtained by coprecipitation. The method comprises the following steps (referred to as step a'): mixing Al₂O₃Suspension of starting powder of matrix with ZrO₂And optionally a sintering aid and Al₂O₃Matrix and ZrO₂And optionally a sintering aid; and the treatment steps of centrifuging, washing, drying, calcining and sieving the obtained product.

First, Al is prepared₂O₃A suspension of a raw powder of the substrate. Specifically, Al is added₂O₃Mixing the raw material powder of the matrix with a PEG (polyethylene glycol) aqueous solution, and then carrying out ultrasonic treatment for 1-3 h for later use. The ultrasound is used to break up the secondary agglomeration between the particles and to make the powder as dispersed as possible in the solution. Wherein the concentration of the PEG aqueous solution is 1-3% by mass.

Then, ZrO is oxidized₂Is formulated as a mixed salt solution with the precursors of the adjuvant, if present. The concentration of the solution can be 0.01-1 mol/L. Wherein, ZrO₂ZrOCl can be used as the precursor₂·8H₂And O. In the presence of Y as an auxiliary₂O₃When Y (NO) is used₃)₃·6H₂O as a promoter precursor; in the adjuvant bagWhen MgO is contained, an inorganic magnesium salt such as Mg (NO) can be used₃)₂·6H₂O、MgCl₂·6H₂O、MgSO₄·7H₂O, and the like. When MgO and Y are present₂O₃When used together as an aid in the sintering of luminescent ceramics, the MgO precursor is combined with Y₂O₃The mass percentage ratio of the precursor can be 1: 2-3: 1.

Further, Al is added₂O₃Suspension of starting powder of matrix with ZrO₂And a precursor solution of an auxiliary agent, if any, are mixed, stirred, and then the pH of the mixed solution is adjusted by using an aqueous ammonia or ammonium hydrogen carbonate solution to obtain a coprecipitated composite powder suspension. And then, centrifugally separating the obtained composite powder suspension, washing the obtained powder for 2-8 times, and drying the powder in vacuum at 50-150 ℃ for 1-10 hours. Then, calcining the obtained dry powder to remove impurities, then performing furnace air cooling, sieving with 80-mesh, 150-mesh and 200-mesh sieves and granulating to obtain the high-fluidity Al₂O₃Matrix and ZrO₂Mixed powders of granules and optionally auxiliaries. The calcination temperature and the calcination time are not particularly limited and can be selected according to different additives, but the calcination temperature is usually 200 to 500 ℃ and the calcination time is 1 to 5 hours.

The temperature during the stirring is set to be 20-80 ℃, preferably 40-60 ℃, and the rotating speed is 100-300 r/m, preferably 170-250 r/m.

The concentration of the ammonia water solution or ammonium bicarbonate solution used in the coprecipitation can be 0.01-0.1 mol/L. The pH value of the solution can be controlled to be about 8-10, and preferably 9-9.5. Suitable pH value for Al₂O₃The dispersion and deflocculation of ultrafine powder particles is very important. The stirring time can be 1-5 h, preferably 2-3 h after the proper pH value is kept.

In adjusting the pH of the solution, a forward titration method may be employed, in which an aqueous ammonia or ammonium hydrogen carbonate solution is dropped into the mixed solution to render ZrO₂And precipitating nanoparticles of the sintering aid. The nano particles will be partially attached to the surface of the phosphor particles and Al₂O₃The surface of the particles is stirred by magnetic force, and the precipitated suspended particles are mixed with the suspensionAl of (2)₂O₃The nanoparticles are mixed together very homogeneously. The addition of the auxiliary agent in the mode can be smaller, the mixing is more uniform, and the effect is more remarkable.

< coprecipitation method >

In the present invention, the method for preparing a luminescent ceramic by a coprecipitation method comprises the steps of:

step II: and (3) centrifugally separating, washing, drying, calcining and sieving the product obtained in the step.

Step I

Firstly, preparing citric acid-NaOH solution, then adding PEG4000, after ultrasonic dissolution, adding fluorescent powder and nano Al₂O₃The powder is placed on a magnetic stirrer for continuous stirring after being dispersed by ultrasonic waves, thereby obtaining the fluorescent powder-Al₂O₃The suspension is mixed. Wherein the fluorescent powder and Al₂O₃The mass ratio of the fluorescent powder to the Al is₂O₃＝1:4～9:1。

ZrO 2 is mixed with₂Is formulated as a mixed salt solution with precursors of the sintering aid, if present. The concentration of the solution can be 0.01-1 mol/L. Wherein, ZrO₂Examples of the precursor of (2) and the precursor of the sintering aid are the same as described above.

The phosphor-Al obtained above₂O₃Mixing the suspension with ZrO₂And optionally a sintering aid, and then adjusting the pH of the mixed solution by using an aqueous ammonia or ammonium bicarbonate solution to obtain a coprecipitated composite powder suspension. This step is the same as that in step a' described in the solid phase method.

Step II

The procedure of centrifuging, drying, calcining and sieving the product obtained in the above step I is the same as that in the step a' described in the above solid phase method. Thereby the device is provided withTo obtain phosphor particles, Al₂O₃Matrix, ZrO₂A mixed powder of particles and sintering aid, if present.

In addition, although in the above coprecipitation method, first, phosphor and Al are prepared₂O₃Mixing the suspension of the substrate with ZrO₂And the precursor of the sintering aid, if present, is mixed. However, the order of adding the raw materials is not limited to this, and Al may be added₂O₃Mixed suspension of matrix and ZrO₂After mixing the precursor of (a) and the precursor of the sintering aid, if present, with the suspension of the phosphor.

Step 2

Weighing appropriate amount of the fluorescent powder particles obtained in the step 1 and Al₂O₃Matrix, ZrO₂The mixed powder of the particles and the optional sintering aid is charged into a high-temperature resistant mold such as a graphite mold to be pressed, and then sintered, followed by furnace cooling, to obtain the luminescent ceramic composite of the present invention.

The sintering method may adopt a direct sintering method, a hot press sintering method or a Spark Plasma Sintering (SPS) method.

When a direct sintering method is adopted, the mixed powder obtained in the step 1 is filled into a die, tabletting is carried out under the pressure of 20-40 MPa, the obtained sample piece is subjected to cold isostatic pressing treatment under 200MPa, and then the sample piece is placed into a sintering furnace and sintered under the protective atmosphere of nitrogen, argon, hydrogen and the like. The sintering temperature can be 1450-1750 ℃, and 1550-1650 ℃ is preferable. The sintering time can be 30 min-20 h, preferably 60min-10 h.

The hot pressing sintering method can greatly reduce the sintering temperature of the material by applying pressure and sintering at the same time, and is an ideal process method for preparing the material. Meanwhile, the temperature rise speed of the hot pressing method is high, a vacuum atmosphere or a protective gas atmosphere can be used, and the method can be suitable for sintering various materials.

When a hot-pressing sintering method is adopted, the mixed powder obtained in the step 1 is filled into a die, pre-pressing is carried out under the pressure of 5-15MPa, then the die is placed into a hot-pressing sintering furnace, and sintering is carried out under the vacuum condition or the argon atmosphere. The sintering temperature can be 1250-1650 ℃, and is preferably 1350-1550 ℃; the sintering pressure is preferably 30-200 MPa, preferably 40-100 MPa, and more preferably 40-75 MPa; the sintering time can be 5min to 6h, preferably 30min to 3 h.

The spark plasma sintering SPS technology has the characteristics of hot-pressing sintering and self-heating, and can heat a sample through pulse current to rapidly sinter the sample. SPS, is generally recognized as having several densification pathways: (1) the discharge and ionization among crystal grains generate local high temperature to cause evaporation and melting on the surface of powder grains, thereby directly promoting the densification process; (2) under the action of pulse current, the surface of the powder particles is easily activated, and various diffusion effects are enhanced, so that the densification process is promoted. Each particle in the spark plasma sintering body is uniformly self-heated to activate the particle surface, thereby having high thermal efficiency, enabling the sintered body to be densified in a relatively short time, and enabling the sintering temperature of fine powder to be effectively lowered.

When sintering is carried out by adopting the SPS method, the mixed powder obtained in the step 1 is filled into a die, pre-pressing is carried out under the pressure of 5-15MPa, and then the die is placed into an SPS sintering furnace to be sintered in a vacuum atmosphere. The sintering temperature can be 1250-1550 ℃, and is preferably 1350-1450 ℃; the sintering time is 30 min-6 h, preferably 60 min-4 h; the sintering pressure is 30 to 200MPa, preferably 40 to 100 MPa.

As described above, by containing Al₂O₃ZrO addition to luminescent ceramics of substrates₂And ZrO is oxidized₂With Al₂O₃The substrate and the fluorescent powder are fully and uniformly mixed, so that the toughness of the luminescent ceramic can be improved, and the optical performance of the luminescent ceramic cannot be adversely affected. Therefore, the luminescent ceramic has the excellent characteristics of high luminous efficiency, high thermal conductivity and adjustable blue light transmittance, and can be applied to high-performance laser light sources, particularly precise laser light source systems.

Examples

The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to the following examples.

The structural features and characterization of the physical properties of the luminescent ceramics obtained in the examples are first described.

(1) Taking of scanning electron microscope photographs

A scanning electron micrograph of the luminescent ceramic of the present invention was taken with a Hitachi scanning electron microscope S-3400N (manufactured by Hitachi, Japan) at an acceleration voltage of 15.0 kv.

(2) Measurement of fracture toughness

In the invention, the fracture toughness of the obtained luminescent ceramic is measured by a single-side notched beam method. The sample size was 5mm × 2.5mm × 25mm in height × width × length. Cutting a sample into a notch with the depth of 2.5mm and the width of less than 0.2mm along the height direction, and performing a three-point bending test with the span of 20mm and the pressing rate of a pressure head of 0.05mm & min^-1. The test was carried out on a DCS-5000 Shimadzu Material testing machine. The breaking load P was recorded and the fracture toughness value Kic was calculated according to the following formula:

Kic＝PL/BW^3/2·f(a/W)

the value of f (a/W) was 2.665, with the specimen aspect ratio W/B being 2 and the span ratio W/L being 1/4.

Example 1：

High-purity superfine Al is selected as raw material₂O₃Nano powder with the particle size of 0.08-0.2 mu m; selecting high-purity superfine nano ZrO₂Powder with the particle size of 0.05-0.1 mu m; high-purity commercial YAG Ce is selected³⁺The particle size of the fluorescent powder is 15-17 mu m.

Weighing a certain amount of Al₂O₃Powder and ZrO₂Powder of ZrO so that₂The content of the powder is Al₂O₃1% by mass of the powder. And (2) putting the two kinds of powder into a polytetrafluoroethylene ball milling tank, adding a proper amount of ethanol as a grinding solvent, adding a proper amount of sodium silicate as a dispersing agent, and carrying out ball milling by using zirconia balls with ultra-low attrition loss rate, wherein the ball milling revolution is 120r/min, and the ball milling time is 36 h.

First time ballAnd after the grinding is finished, adding YAG (yttrium aluminum garnet) and Ce fluorescent powder into a ball milling tank to ensure that the mass percent of fluorescent powder particles accounts for 20 mass percent of the total powder, and performing secondary ball milling at a low speed, wherein the ball milling revolution is 60r/min, and the ball milling time is 40 min. The total powder is Al₂O₃Powder, ZrO₂Sum of powder and phosphor powder.

After the ball milling is finished for two times, drying at constant temperature under vacuum at 60 ℃ to obtain dry powder. The dry powder was calcined at 500 ℃ in a muffle furnace to remove the organic components from the powder for 5 hours.

And sieving the calcined powder with 80-mesh, 150-mesh and 200-mesh sieves for granulation to obtain the high-fluidity raw material powder.

Weighing a proper amount of raw material powder, filling the raw material powder into a graphite die, pre-pressing the graphite die under the pressure of 5MPa, then putting the graphite die into a hot-pressing sintering furnace, sintering the graphite die in an argon atmosphere at the sintering temperature of 1500 ℃, and preserving the heat for 10min, wherein the sintering pressure is 40 MPa. And after sintering, removing pressure and cooling along with the furnace. Thus, YAG-Al was obtained₂O₃-ZrO₂Luminescent ceramic composites, i.e. PIA-ZrO₂。

A scanning electron micrograph of the resulting luminescent ceramic is shown in FIG. 2. The circles in the figure are YAG: Ce phosphor particles and the black areas are alumina areas, which have a very small particle size and are shown as a continuous phase.

The luminescent ceramic obtained in this example had a fracture toughness value of 5.56MPa · m^1/2。

Example 2：

Al used in this example₂O₃The nanopowder and the YAG: Ce phosphor were the same as in example 1. Using Y₂O₃The powder is high-purity superfine nanometer Y₂O₃Powder with a particle size of 0.05 to 0.1 μm.

Weighing a proper amount of Al₂O₃Powder, ZrO₂Powder and Y₂O₃Powder of ZrO so that₂The content of the powder is Al₂O₃0.2% by mass of the powder, so that Y₂O₃The content of the powder is Al₂O₃Powder of0.5% by mass of (A). And (2) putting the three powders into a polytetrafluoroethylene ball milling tank, adding a proper amount of ethanol as a grinding solvent, adding a proper amount of sodium silicate as a dispersing agent, and carrying out ball milling by using zirconia balls with ultra-low attrition rate, wherein the ball milling revolution is 120r/min, and the ball milling time is 36 hours.

After the first ball milling is finished, adding a proper amount of YAG (yttrium aluminum garnet) and Ce fluorescent powder into a ball milling tank so that the mass percent of the fluorescent powder particles accounts for 50 percent of the total powder. And performing secondary ball milling at a low speed, wherein the ball milling revolution is 60r/min, and the ball milling time is 40 min. The total powder is Al₂O₃Powder, ZrO₂Powder, Y₂O₃Sum of powder and phosphor powder.

After the ball milling is finished for two times, drying at constant temperature under vacuum at 60 ℃ to obtain dry powder. The dry powder was calcined at 650 ℃ in a muffle furnace to remove the organic components from the powder for 1 hour.

Weighing a proper amount of raw material powder, filling the raw material powder into a graphite die, pre-pressing the graphite die under the pressure of 15MPa, then putting the graphite die into a hot-pressing sintering furnace, sintering the graphite die in an argon atmosphere at the sintering temperature of 1250 ℃, and preserving heat for 6 hours, wherein the sintering pressure is 100 MPa. And after sintering, removing pressure and cooling along with the furnace. Thus, YAG-Al was obtained₂O₃-ZrO₂-Y₂O₃Luminescent ceramic composites, i.e. PIA-ZrO₂-Y₂O₃。

Example 3：

Al used in this example₂O₃The nanopowder and the YAG: Ce phosphor were the same as in example 1.

According to the fluorescent powder Al₂O₃Weighing appropriate amount of fluorescent powder and high-purity Al according to the mass ratio of 1:3₂O₃And (4) nano powder.

Preparing citric acid-NaOH solution with pH value of 5.0, the concentration is 1.0mol/L, then adding 1.5 mass percent of PEG4000, after ultrasonic dissolution, adding weighed YAG: Ce³⁺Phosphor particles and nano-Al₂O₃Powder is added with a magnetic stirrer after being dispersed by ultrasonic wave and is placed on a magnetic stirrer to be stirred continuously to obtain fluorescent powder-Al₂O₃And mixing the suspension to obtain a solution I.

According to ZrO₂:Al₂O₃Weighing appropriate amount of ZrOCl in a ratio of 0.5 to 100 mass%₂·8H₂O, according to Y₂O₃:Al₂O₃Weighing appropriate amount of Y (NO) at a ratio of 1 to 100 mass%₃)₃·6H₂And O, preparing the two nitrate hydrates into a nitrate mixed solution with the concentration of 0.05mol/L together, namely obtaining a solution II.

Adding the second solution into the first solution to obtain a third solution, wherein the third solution is YAG, Ce fluorescent powder particles and nano Al₂O₃The mixed solution of the powder suspension and the nitrate is continuously stirred by a magnetic stirrer. The temperature was set at 40 ℃ and the rotational speed was 250 r/m.

0.05mol/L ammonia water solution is prepared, and the continuously stirred mixed suspension III is slowly dropped until the PH value of the mixed suspension is controlled to be about 9. Keeping the pH value and then continuing stirring for 2.5h to obtain a coprecipitated composite powder suspension IV.

The suspension was centrifuged, and the obtained powder was washed with water 4 times and then vacuum-dried at 80 ℃ for 5 hours. Calcining the obtained dry powder at 500 ℃ to remove impurities, preserving heat for 5 hours, and then performing air cooling along with the furnace to obtain YAG-Al₂O₃-ZrO₂-Y₂O₃Mixing the powders, sieving with 80 mesh, 150 mesh and 200 mesh sieves, and granulating to obtain high-fluidity raw material powder.

Weighing a proper amount of raw material powder, filling the raw material powder into a mold, tabletting under the pressure of 40MPa, performing cold isostatic pressing treatment on the obtained sample piece under the pressure of 200MPa, then putting the sample piece into a hydrogen sintering furnace, sintering the sample piece in the hydrogen atmosphere at the sintering temperature of 1750 ℃, preserving heat for 20 hours, and cooling the sample piece along with the furnace after sintering is finished to obtain the luminescent composite ceramic material YAG-Al₂O₃-ZrO₂-Y₂O₃I.e. PIA-ZrO₂-Y₂O₃。

Example 4:

Preparing 1.5 mass% PEG aqueous solution, adding appropriate amount of Al₂O₃Mixing the nanopowder with aqueous PEG solution, and mixing Al₂O₃The solution is kept for later use after being subjected to ultrasonic treatment for 1.5h, and the solution is the first solution. The ultrasound is used to break up the secondary agglomeration between the particles and to make the powder as dispersed as possible in the solution.

According to ZrO₂:Al₂O₃Weighing appropriate amount of ZrOCl at a ratio of 3 mass% to 100 mass%₂·8H₂O, according to (MgO + Y)₂O₃):Al₂O₃Weighing appropriate amount of Mg (NO) at a ratio of 3 mass% to 100 mass%₃)₂·6H₂O and Y (NO)₃)₃·6H₂O, wherein Mg (NO)₃)₂·6H₂O and Y (NO)₃)₃·6H₂The mass percentage ratio of O is 1: 2. The three nitrates were dissolved together in deionized water to make a nitrate solution with a concentration of 0.05M, and a second solution.

And mixing the solution I and the solution II to obtain a mixed suspension III, and continuously stirring the mixed suspension III on a magnetic stirrer at the temperature of 60 ℃ and the rotating speed of 250 r/m.

Ammonium bicarbonate is used as a precipitant to prepare an aqueous solution of about 0.05mol/L, and the continuously stirred mixed suspension III is slowly dropped until the pH value of the mixed suspension is controlled to be about 9. Stirring is continued for 2.5h after the proper pH value is maintained, and the coprecipitated composite powder suspension is obtained.

The suspension was centrifuged, and the obtained powder was washed with water 4 times and then vacuum-dried at 80 ℃ for 5 hours. Calcining the obtained dry powder at 500 ℃ to remove impurities, preserving heat for 5 hours, and then performing air cooling along with the furnace to obtain Al₂O₃-ZrO₂-Y₂O₃MgO mixed powder is sieved by 80 meshes, 150 meshes and 200 meshes and granulated.

Weighing a proper amount of Al₂O₃-ZrO₂-Y₂O₃-MgO mixtureMixing the powder and the YAG-Ce fluorescent powder so that the mass ratio of the total powder to the YAG-Ce fluorescent powder is 2: 1. And (3) putting the two powders into a polytetrafluoroethylene ball milling tank, adding a proper amount of ethanol as a grinding solvent, and carrying out ball milling by using zirconia balls with ultralow loss rate for 30min without using any dispersing agent. The total powder is Al₂O₃Powder, ZrO₂Powder, Y₂O₃Powder, MgO powder and phosphor powder.

After the ball milling is finished, drying the mixture at constant temperature of 60 ℃ in vacuum to obtain dry powder, and then sieving the dry powder by using 80-mesh, 150-mesh and 200-mesh sieves for granulation to obtain high-fluidity raw material powder.

Weighing a proper amount of raw material powder, filling the raw material powder into a graphite die, pre-pressing the graphite die under the pressure of 5MPa, then putting the graphite die into an SPS sintering furnace, and sintering the graphite die in a vacuum atmosphere at the sintering temperature of 1450 ℃ for 3h at the sintering pressure of 80 MPa. After sintering, the pressure is removed and the material is cooled along with the furnace to obtain the luminescent composite ceramic material YAG-Al₂O₃-ZrO₂-Y₂O₃MgO, i.e. PIA-ZrO₂-Y₂O₃-MgO。

Example 5:

a luminescent ceramic of example 5 was prepared in the same manner as in example 1, except that the phosphor particles were made to account for 90 mass% of the total frit.

Comparative example 1:

except that no ZrO was added₂Except that, the luminescent ceramic of comparative example 1 was prepared in the same manner as in example 1. The fracture toughness value Kic of the luminescent ceramic obtained in comparative example 1 is 4.59MPa · m^1/2。

Comparing the fracture toughness value of the luminescent ceramic of example 1 with the fracture toughness value of the luminescent ceramic of comparative example 1, it can be seen that the fracture toughness value of example 1 is about 20% higher than that of comparative example 1. Thus, it can be seen that by using ZrO₂The particles and the fluorescent powder are fully mixed with Al₂O₃The matrix is mixed and uniformly dispersed in Al₂O₃In the matrix, the toughness of the luminescent ceramic is greatly improved without causingAdversely affecting the optical properties of the luminescent ceramic, and ZrO₂Acting as scattering particles, can act to homogenize incident light.

While the present application has been described in detail with reference to exemplary embodiments, it should be understood that the invention is not limited thereto. It will be apparent to those skilled in the art that changes and modifications may be made without departing from the spirit of the invention, and these are to be considered within the scope of the invention.

Claims

1. A luminescent ceramic, characterized in that it comprises Al₂O₃Matrix, ZrO₂Particles and fluorescent powder particles, wherein the fluorescent powder particles are arranged in a matrix,

wherein the ZrO₂The content of the particles is Al₂O₃0.05 to 0.2 mass% of the matrix, the ZrO 2₂The particle size of the particles is 0.05-1 mu m, the particle size of the fluorescent powder particles is 10-50 mu m, and the Al is₂O₃The grain size of the matrix is 0.05 to 5 μm,

wherein the phosphor particles are uniformly dispersed in the Al₂O₃In a matrix; the ZrO₂Particles are dispersed in the Al₂O₃Between the grain boundaries of the matrix, the grain boundary,

the luminescent ceramic further comprises Y₂O₃Particles, and Y₂O₃The content of the particles is Al₂O₃0.05 to 0.5 mass% of the matrix.

2. The luminescent ceramic of claim 1, wherein the phosphor particles are in contact with the Al₂O₃The mass ratio of the matrix is 1: 4-9: 1.

3. The luminescent ceramic of claim 1, wherein the ZrO₂The particle size of the raw material powder of the particles is 0.05-0.7 mu m; the particle size of the raw material powder of the fluorescent powder particles is 10-25 mu m; the Al is₂O₃The particle size of the raw material powder is 0.05-1 μm.

4. The luminescent ceramic of claim 1, wherein the ZrO₂The particle size of the particles is 0.05-0.35 μm.

5. A method for preparing a luminescent ceramic according to claim 1, characterized in that it comprises the following steps:

6. The production method according to claim 5, wherein the step 1 comprises the steps of:

7. The method of claim 6, wherein the step a is replaced with a step a' comprising: adding the Al₂O₃Suspension of starting powder of matrix with ZrO₂A step of mixing and co-precipitating a solution of the precursor of (a) and a solution of the precursor of the optional sintering aid; and the steps of centrifuging, washing, drying, calcining and sieving the obtained product.

8. The production method according to claim 5, wherein the step 1 comprises the steps of: