WO2018223544A1 - Luminous ceramic and preparation process thereof - Google Patents

Abstract

The present invention provides a luminous ceramic and a preparation process thereof. The luminous ceramic comprises Al2O3 matrixes, ZrO2 particles and phosphor particles, and can be obtained by a solid phase method or a liquid phase method.

Description

Light-emitting ceramic and preparation method thereof Technical field

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

Background technique

The blue laser excitation of fluorescent materials to obtain visible light technology, as a new light source technology, has made significant progress in the field of laser display, and has been recognized by the market, and related technologies continue to receive attention. The hotspots and difficulties in current research are mainly to develop new fluorescent materials (wavelength conversion materials, luminescent materials) for the characteristics of laser-excited phosphors. These materials must have excellent performance, such as high optical conversion efficiency, high brightness, and unit light-emitting area. Can withstand higher power laser irradiation, high thermal conductivity, long life and so on.

With the improvement of requirements, the traditional silica gel package phosphor technology and glass package phosphor technology can not meet the needs of high-end products. The temperature of silicone can not exceed 200-250 °C. It is easy to age and work for a long time under high temperature environment. Not long; the thermal conductivity of silicone encapsulation and glass encapsulation materials generally does not exceed 2W / (m · k), in the fixed excitation scheme (corresponding to the rotary excitation scheme), can not withstand high power or even large Power laser irradiation.

Luminescent ceramics are an ideal choice because luminescent ceramics have higher heat and thermal conductivity than silica and glass-encapsulated phosphors. However, the traditional YAG (Y ₃ Al ₅ O ₁₂ ) pure phase luminescent ceramics are still weaker in luminescent properties than silica gel and glass packages; especially in ultra-thin packaging, the light effect caused by total reflection of the interface The loss is great. Therefore, using other high thermal conductivity ceramic materials to encapsulate the phosphor, such as YAG-Al ₂ O ₃ (PIA, Phosphor In Alumina) prepared by using Al ₂ O ₃ encapsulated YAG phosphor, can obtain better than pure phase YAG luminescent ceramics. Performance is the direction that deserves in-depth research.

Since luminescent ceramics tend to be more precise, after a luminescent ceramic in which Al ₂ O ₃ encapsulated phosphor is prepared, a series of processes of cutting, smoothing, polishing, dividing, coating, soldering, etc. are required, thereby illuminating The mechanical properties of ceramics are very high, especially for their toughness.

Therefore, how to obtain luminescent ceramics with both optical and mechanical properties is an important subject of research.

Summary of the invention

Problems to be solved by the invention

The present invention has been made to solve the above problems. Accordingly, it is an object of the present invention to provide a luminescent ceramic which can simultaneously satisfy the improvement in the toughness of a luminescent ceramic without significantly affecting the optical properties of the luminescent ceramic.

Solution to solve the problem

The present invention provides a luminescent ceramic characterized by comprising an Al ₂ O ₃ matrix, ZrO ₂ particles, and phosphor particles.

The luminescent ceramic according to the present invention, wherein the phosphor particles and the ZrO ₂ particles are uniformly dispersed in the Al ₂ O ₃ matrix. Further, the ZrO ₂ particles are dispersed between grain boundaries of the Al ₂ O ₃ matrix.

The luminescent ceramic according to the present invention, wherein the content of the ZrO ₂ particles is 0.05 to 5% by mass, preferably 0.2 to 3% by mass, more preferably 0.5 to 1% by mass based on the mass of the Al ₂ O ₃ substrate.

The luminescent ceramic according to the present invention, wherein the mass ratio of the phosphor particles to the Al ₂ O ₃ matrix is from 1:4 to 9:1, preferably from 1:4 to 3:1, more preferably 1:3. 1:1.

The luminescent ceramic according to the present invention, wherein the ZrO ₂ particles have a particle diameter of 0.05 to 1 μm, preferably 0.05 to 0.7 μm, particularly preferably 0.05 to 0.35 μm, and the phosphor particles have a particle diameter of 10 to 50 μm. Preferably, it is 10 to 30 μm, particularly preferably 10 to 25 μm, and the crystal grain size of the Al ₂ O ₃ matrix is 0.05 to 5 μm, preferably 0.15 to 5 μm, particularly preferably 0.15 to 3 μm; and/or the ZrO ₂ particles The raw material powder has a particle diameter of 0.05 to 0.7 μm, preferably 0.05 to 0.2 μm, and the raw material powder of the phosphor particles has a particle diameter of 10 to 25 μm, preferably 15 to 17 μm, and the particle diameter of the Al ₂ O ₃ raw material powder. It is 0.05 to 1 μm, preferably 0.1 to 0.3 μm.

The luminescent ceramic according to the present invention, further comprising a sintering aid, and the sintering aid is at least one selected from the group consisting of Y ₂ O ₃ , MgO, CaO, SiO ₂ , TiO ₂ , BaO, CaF ₂ , and BaF ₂ . Preferably, Y ₂ O ₃ and/or MgO, more preferably Y ₂ O ₃ .

In addition, the present invention also provides a method for preparing a luminescent ceramic, characterized in that it comprises the following steps:

Step 1: a preparation step of a mixed powder comprising an Al ₂ O ₃ matrix, ZrO ₂ particles, and phosphor particles;

Step 2: a step of pressing and sintering the above mixed powder to obtain a luminescent ceramic.

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

Step a: a preparation step of a mixed powder of the Al ₂ O ₃ substrate and the ZrO ₂ particles and an optional sintering aid;

Step b: a step of mixing the above mixed powder with the phosphor particles, ball milling, drying, and sieving.

The preparation method according to the present invention, wherein the step a may be replaced by the step a', the step a' comprising: a solution of a suspension of the raw material powder of the Al ₂ O ₃ matrix and a precursor of ZrO ₂ a step of mixing and coprecipitating with a solution of a precursor of an optional sintering aid; and a step of centrifuging, washing, drying, calcining, and sieving the obtained product.

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

Step I: a step of mixing a mixed suspension of an Al ₂ O ₃ raw material powder and a phosphor with a solution of a precursor of ZrO _{2 and} a precursor of a precursor of a sintering aid, and then coprecipitating;

Step II: a step of centrifuging, washing, drying, calcining, and sieving the product obtained in the step I.

Effect of the invention

In the present invention, by adding an appropriate amount of small-diameter ZrO _{2 to} the luminescent ceramic of the Al ₂ O ₃ encapsulated phosphor, the phosphor particles and the ZrO ₂ particles are uniformly dispersed in the Al ₂ O ₃ matrix, thereby not only improving the toughness of the luminescent ceramic. And does not adversely affect the optical properties of the luminescent ceramic. Moreover, ZrO ₂ can also function as scattering particles to homogenize incident light. Therefore, the luminescent ceramic of the present invention has excellent characteristics of high light efficiency, high thermal conductivity, and adjustable blue light transmittance, and can be applied to a high performance laser light source, particularly a precision laser light source system.

DRAWINGS

Fig. 1 is a schematic view showing the structure of a luminescent ceramic of the present invention.

2 is a scanning electron micrograph of a sample obtained in Example 1.

detailed description

Hereinafter, the luminescent ceramic of the present invention and a method for producing the same will be described in more detail by way of specific embodiments.

The luminescent ceramic of the present invention includes an Al ₂ O ₃ matrix, ZrO ₂ particles, and phosphor particles. Among them, the phosphor particles having a large particle diameter are uniformly dispersed in the Al ₂ O ₃ matrix, and the ZrO ₂ particles having a small particle diameter are located between the grain boundaries of the Al ₂ O ₃ matrix.

Fig. 1 is a schematic view showing the structure of a luminescent ceramic of the present invention. Wherein 1 represents an Al ₂ O ₃ matrix, 2 represents ZrO ₂ particles, and 3 represents phosphor particles. It can be seen from FIG. 1 that the luminescent ceramic of the present invention is characterized in that a fine grain of Al ₂ O ₃ is used as a matrix, and a large phosphor particle is uniformly dispersed in an Al ₂ O ₃ matrix, and a small ZrO is used. _{2 The} particles are located between the grain boundaries of the Al ₂ O ₃ matrix. Also, the phosphor particles are continuously surrounded by crystal grains of the Al ₂ O ₃ matrix. The phosphor particles in the ceramic can absorb the excitation light and emit the laser; in particular, the blue light can be excited to emit yellow visible light; the dense and fine grained Al ₂ O ₃ matrix has good light transmission performance, and the excited visible light can be worn. The Al ₂ O ₃ matrix exits the outside of the ceramic. The smaller ZrO ₂ particles can function to increase the toughness of the luminescent ceramic and do not adversely affect the luminescent properties of the luminescent ceramic. Moreover, ZrO ₂ can also function as scattering particles to homogenize incident light.

The luminescent ceramic according to the present invention, wherein the ZrO ₂ particles have a particle diameter of 0.05 to 1 μm, preferably 0.05 to 0.7 μm, particularly preferably 0.05 to 0.35 μm.

The luminescent ceramic according to the invention, wherein the phosphor particles have a particle diameter of 10 to 50 μm, preferably 10 to 30 μm, particularly preferably 10 to 25 μm.

The luminescent ceramic according to the present invention, wherein the crystal grain size of the Al ₂ O ₃ matrix is 0.05 to 5 μm, preferably 0.15 to 5 μm, 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, in the preparation of the luminescent ceramics of the Al ₂ O ₃ encapsulated phosphor, an appropriate amount of ZrO ₂ nanopowder is added, and the tetragonal phase t-ZrO ₂ and the monoclinic phase are used in the process of heating and cooling using ZrO ₂ grains. The volume change characteristic produced by the reversible transformation of m-ZrO ₂ is toughened by the microcrack phase transformation toughening. That is, when the temperature during heating is about 1200 ° C, m-ZrO _{2 is} converted into t-ZrO ₂ and the volume is contracted; when the temperature is about 1000 ° C during cooling, t-ZrO _{2 is} converted into m-ZrO ₂ and the volume is expanded. The volume shrinkage and expansion process of ZrO ₂ will produce tiny cracks or elastic post-effect forces in the ceramic matrix. When the ceramic is broken or breaks, the microcracks or stress will absorb or offset the stress causing the ceramic fracture, thus Ceramics can withstand greater stresses without breaking, which enhances the toughness of ceramics. The small particle size and dispersion of ZrO ₂ particles is the key to achieving the toughening effect. In addition, ZrO ₂ is a white opaque component in the light-transmitting Al ₂ O ₃ matrix, which usually affects the light transmittance of the Al ₂ O ₃ matrix. In the present invention, it is surprisingly small that the influence of the incidence of blue light and yellow light is small by making the particle size of ZrO ₂ small and the amount of addition is small. Further, as a white particle, ZrO ₂ can function to scatter incident light to make the incident light uniform, and it does not substantially absorb light, and does not cause loss of light. Therefore, the final effect is that the addition of ZrO ₂ particles does not significantly affect the optical properties of the luminescent ceramics, and ZrO ₂ can significantly enhance the mechanical properties of the luminescent ceramics and can act as scattering particles to homogenize incident light.

In the luminescent ceramic of the present invention, the content of ZrO ₂ is 0.05 to 5% by mass, preferably 0.2 to 3% by mass, and more preferably 0.5 to 1% by mass based on the mass of the Al ₂ O ₃ substrate. When the content of ZrO ₂ is less than 0.05% by mass, the toughening effect is not remarkable. When the content of ZrO ₂ is more than 5% by mass, the ZrO ₂ phase in the luminescent ceramic is more pronounced, and the reflection of the incident blue light is more remarkable. At this time, the blue light content of the light emitted by the yellow luminescent ceramic is increased, and the yellow light is increased. The content will decrease, which will result in a decrease in the overall luminous efficacy of the luminescent ceramic. When the content of ZrO ₂ is 0.05 to 5% by mass, preferably 0.2 to 3% by mass, not only the toughening effect can be exhibited, but also the light effect of the luminescent ceramic is not adversely affected, and the scattering granule can be used as a scattering particle. The role of incident light.

In addition, it should be noted that when it is required to emit a uniform white light ceramic, the content of ZrO ₂ can be increased to increase the number of white spots. At this time, the content of ZrO ₂ may be a relatively high value within the above range, for example, 4 to 5% by mass. ZrO ₂ acts as a scattering particle to make the emitted white light more uniform.

The phosphor is not particularly limited, and a phosphor commonly used in the field of luminescent ceramics can be used. In the present invention, the phosphor preferably used is selected from the group consisting of Ca ₃ (Al, Sc) ₂ Si ₃ O ₁₂ , (Gd, Tb, Y, Lu) ₃ (Al, Ga) ₅ O ₁₂ , Y ₃ Mg ₂ AlSi ₂ O ₁₂ and at least one doped Ce ³⁺ phosphor, preferably wherein Y ₃ Al ₅ O ₁₂ phosphor doped with Ce ³⁺ i.e. YAG:Ce ³⁺ phosphor.

The mass ratio of the phosphor particles to the Al ₂ O ₃ matrix is from 1:4 to 9:1, preferably from 1:4 to 3:1, more preferably from 1:3 to 1:1. Further, the content of the phosphor particles is 15 to 90% by mass, preferably 15 to 50% by mass, based on the total amount of the Al ₂ O ₃ matrix, the ZrO ₂ particles, the phosphor particles, and the sintering aid present.

As described above, the small particle size of the ZrO ₂ particles is one of the key factors for achieving the toughening effect. In the present invention, the ZrO ₂ raw material powder has a particle diameter of 0.05 to 0.7 μm, preferably 0.05 to 0.2 μm, particularly preferably 0.05 to 0.1 μm. If the particle size of the ZrO ₂ raw material powder is too large, white spots are formed in the luminescent ceramic, and the toughening effect is not good at the same time. It should be noted that the particle size range of the ZrO ₂ raw material powder here is slightly smaller than the particle size range of ZrO ₂ in the luminescent ceramic; it can be understood that when the ZrO ₂ raw material powder as a raw material is in the whole preparation process, partial agglomeration may occur. And during the sintering process, some ZrO ₂ grains will grow abnormally without inhibition; therefore, the particle size range of ZrO ₂ in the luminescent ceramic may be slightly larger than the particle size of the ZrO ₂ raw material powder; but based on the uniformity of dispersion The change in the particle size of ZrO ₂ is not too significant.

Further, the particle diameter of the Al ₂ O ₃ raw material powder is 0.05 to 1 μm, preferably 0.1 to 0.3 μm. The phosphor raw material powder has a particle diameter of 10 to 25 μm, preferably 15 to 17 μm. It should be noted that fine-grained Al ₂ O ₃ has good mechanical properties in luminescent ceramics, and its strength and toughness are superior to those of large-grained Al ₂ O ₃ matrix. Generally, due to the abnormal growth of crystal grains during agglomeration and sintering, the particle size of some Al ₂ O ₃ raw material powders is increased by 3 to 5 times. It will be understood that this phenomenon is equally applicable to other components of the present invention. However, in the present invention, the use of the Al ₂ O ₃ raw material powder having a small particle size during the preparation process, the added ZrO ₂ simultaneously acts to suppress the excessive (abnormal) growth of the Al ₂ O ₃ , thus enhancing the strength of the luminescent ceramic. And resilience has a positive impact.

When the alumina grain size falls within the scope of the present invention, sintering is favored at a lower temperature. For example, when YAG:Ce ³⁺ phosphor is used as the phosphor of the present invention, the melting point of YAG is 1970 ° C, and the melting point of Al ₂ O ₃ is 2000 ° C. To form the above-mentioned luminescent ceramic material, Al ₂ O _{3 is required} first. Into the liquid phase sintering, the main phase migration occurs, YAG does not enter or rarely enter the liquid phase sintering, only a very small amount of phase migration occurs. Therefore, the Al ₂ O ₃ powder in the raw material is an ultrafine powder having a nanometer-high specific surface area, and the average particle diameter is 0.05 to 1 μm, preferably 0.1 to 0.3 μm. Using a small particle size nano-Al ₂ O ₃ powder, under the conditions of hot pressing sintering, a dense Al ₂ O ₃ ceramic can be fired at about 1500 ° C, which is much lower than the melting point of the large particle YAG, and Al ₂ O ₃ can be realized. The sintering is completed and YAG does not participate in the sintering, so the main particle morphology is unchanged.

Further, the luminescent ceramic of the present invention may include a sintering aid. The example of the sintering aid is not particularly limited, and an auxiliary agent commonly used in the art can be used. For example, the sintering aid may be at least one selected from the group consisting of Y ₂ O ₃ , MgO, CaO, and SiO ₂ . Among them, Y ₂ O ₃ and/or MgO, more preferably Y ₂ O ₃ is preferable as the sintering aid of the present invention. The content of the sintering aid is 0.05 to 5% by mass, preferably 0.05 to 3% by mass, and more preferably 0.5 to 1% by mass based on the mass of the Al ₂ O ₃ substrate.

When Y ₂ O ₃ powder particles are used as an auxiliary agent, it can be used as a sintering aid for luminescent ceramics to promote liquid phase sintering, or as a stabilizer for ZrO ₂ , so that the phase transition behavior of ZrO ₂ is not so severe. Moderate volume change.

Together, MgO and Y ₂ O ₃ can be used as auxiliaries for luminescence ceramic sintering, which can significantly improve liquid phase sintering and lower the sintering temperature. Y ₂ O ₃ and MgO are all minor additives, and if their content is less than 0.05% by mass relative to the mass of the Al ₂ O ₃ matrix, the auxiliary action is reduced; if their content is more than 5% by mass, Affects the transparency of the Al ₂ O ₃ matrix. The three powder particles of ZrO ₂ , Y ₂ O ₃ and MgO need to be thoroughly mixed with the Al ₂ O ₃ nano powder particles in order to function most effectively.

Further, the relative density of the luminescent ceramic of the present invention is 4.1 to 4.31 g/cm ³ . The higher the relative density, the higher the thermal conductivity, light efficiency and mechanical properties, especially the thermal conductivity will be greatly improved.

The method for producing the luminescent ceramic of the present invention is further explained below.

As described above, it is necessary to sufficiently mix the ZrO ₂ and the sintering aid present if present with the Al ₂ O ₃ matrix powder to function most effectively. Therefore, the method for producing the luminescent ceramic of the present invention is not particularly limited as long as the powder can be uniformly mixed.

Specifically, the method for preparing the luminescent ceramic of the present invention comprises the following steps:

Step 1: a preparation step of a mixed powder comprising an Al ₂ O ₃ matrix, ZrO ₂ particles, and phosphor particles;

Step 2: a step of pressing and sintering the above mixed powder to obtain a luminescent ceramic.

step 1

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

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

<Solid phase method>

In the present invention, a method of preparing a mixed powder comprising an Al ₂ O ₃ matrix, ZrO ₂ particles, and phosphor particles by a solid phase method includes the following steps:

Step a: a preparation step of a mixed powder of an Al ₂ O ₃ substrate and ZrO ₂ particles and an optional sintering aid;

Step b: a step of mixing the above mixed powder with a phosphor, ball milling, drying, and sieving.

Step a

The preparation of a mixed powder of an Al ₂ O ₃ substrate and ZrO ₂ particles and an optional sintering aid can be obtained by a method comprising: a raw material powder of an Al ₂ O ₃ matrix and a raw material of ZrO ₂ particles and optionally The powder of the raw material of the sintering aid is mixed and subjected to a step of ball milling (referred to as first ball milling).

Specifically, a raw material powder of an Al ₂ O ₃ matrix and a raw material of a raw material of ZrO ₂ particles and a raw material of an optional sintering aid are charged into a polytetrafluoroethylene ball mill tank, and an appropriate amount of ethanol is added as a grinding solvent, and an appropriate amount is added. The ceramic dispersant is used as a dispersing agent and ball-milled with an ultra-low wear rate zirconia ball, and the ball milling time is 1 to 72 h, preferably 24 to 36 h. Thereby, a mixed powder of an Al ₂ O ₃ matrix with ZrO ₂ and an optional sintering aid is obtained. In the first ball milling, the raw material powder of the Al ₂ O ₃ matrix is mixed and ground with the raw material powder of the ZrO ₂ particles and the raw material powder of the optional sintering aid, and therefore the number of rotations of the ball mill is not particularly limited.

Among them, the dispersing agent is not particularly limited, and a dispersing agent commonly used in the art can be used. Examples thereof include inorganic salts such as sodium silicate, sodium tripolyphosphate, sodium hexametaphosphate, etc.; lower organic substances such as sodium stearate, sodium citrate, sodium alkylsulfonate, etc.; polymers such as polyacrylic acid and salts thereof , polyvinyl alcohol and the like.

Step b

The mixed powder of the Al ₂ O ₃ matrix obtained by the above step a and the mixed powder of the ZrO ₂ particles and the optional sintering aid is mixed with the phosphor particles, and then ball milled at a low speed (referred to as a second ball milling), and the ball milling time is 10 to 120 min, preferably 30 to 50 min. The number of revolutions of the ball mill is 30-100 r/min. It should be noted that the main purpose of using low speed is to control the impact force on the phosphor particles during ball milling to avoid damage to the surface morphology of the phosphor particles.

The first ball milling time is longer in order to thoroughly mix the Al ₂ O ₃ powder with the ZrO ₂ particles and the optional sintering aid powder, and the powder of the ZrO ₂ particles and the optional sintering aid must be mixed with the Al ₂ O ₃ powder. Full mixing to ensure even diffusion. The second ball milling time is shorter because the phosphor particles are larger and easier to disperse. If the ball milling time is too long, the grain surface morphology of the phosphor is easily damaged, which affects the luminescence property.

After the ball milling is completed, the dry powder is obtained by vacuum drying at a constant temperature. The dry powder is calcined in a muffle furnace at 500 to 650 ° C to remove organic components in the powder. Then, the calcined powder was passed through a mesh of 80 mesh, 150 mesh, and 200 mesh to obtain a raw material powder having high fluidity.

The above-mentioned step a, that is, the preparation of a mixed powder of an Al ₂ O ₃ substrate and ZrO ₂ particles and an optional sintering aid can also be obtained by a coprecipitation method. The method comprises the following steps (referred to as step a'): mixing a suspension of a raw material powder of an Al ₂ O ₃ matrix with a solution of a precursor of ZrO _{2 and} a precursor of an optional sintering aid and making Al ₂ a step of coprecipitating the O ₃ substrate with ZrO ₂ and an optional sintering aid; and a treatment step of centrifuging, washing, drying, calcining, and sieving the obtained product.

First, a suspension of the raw material powder of the Al ₂ O ₃ matrix was prepared. Specifically, the raw material powder of the Al ₂ O ₃ matrix was mixed with the PEG aqueous solution, and then ultrasonicated for 1 to 3 hours and then used. Ultrasound is to destroy the secondary agglomeration between the particles, allowing the powder to disperse as much as possible in the solution. The concentration of the PEG aqueous solution may be 1 to 3% by mass.

The precursor of ZrO ₂ is then formulated into a mixed salt solution together with the precursor of the adjuvant if present. The solution concentration may be from 0.01 to 1 mol/L. Wherein, ZrO ₂ precursors can be used ZrOCl ₂ · 8H ₂ O. When the auxiliary agent contains Y ₂ O ₃ , Y(NO ₃ ) ₃ ·6H ₂ O can be used as an auxiliary precursor; when the auxiliary agent contains MgO, an inorganic magnesium salt such as Mg(NO ₃ ) ₂ ·6H ₂ can be used. O, MgCl ₂ · 6H ₂ O, MgSO ₄ · 7H ₂ O, and the like. When MgO and Y ₂ O ₃ are used together as an auxiliary agent for luminescence ceramic sintering, the mass percentage ratio of the MgO precursor to the Y ₂ O ₃ precursor may be 1:2 to 3:1.

Further, a suspension of the raw material powder of the Al ₂ O ₃ matrix is mixed with a precursor solution of ZrO ₂ and a possible auxiliary agent, stirred, and then the pH of the mixed solution is adjusted by using ammonia water or an ammonium hydrogencarbonate solution to obtain a coprecipitation. Composite powder suspension. Then, the obtained composite powder suspension is centrifuged, and the obtained powder is washed with water for 2 to 8 times, and vacuum-dried at 50 to 150 ° C for 1 to 10 hours. Then, the obtained dry powder is calcined to remove impurities, and then granulated by 80 mesh, 150 mesh, and 200 mesh sieves with air cooling to obtain a highly fluid Al ₂ O ₃ matrix and ZrO ₂ particles and optional auxiliary agents. Mixed powder. The calcination temperature and the calcination time are not particularly limited and may be selected according to different auxiliary agents, but usually the calcination temperature is 200 to 500 ° C, and the calcination time is 1 to 5 hours.

The temperature during the stirring is set to 20 to 80 ° C, preferably 40 to 60 ° C, and the number of rotations is 100 to 300 r/m, preferably 170 to 250 r/m.

The concentration of the aqueous ammonia solution or the ammonium hydrogencarbonate solution used in the coprecipitation may be 0.01 to 0.1 mol/L. The pH of the solution can be controlled to be about 8 to 10, preferably 9 to 9.5. A suitable pH value is very important for the dispersion and deflocation of Al ₂ O ₃ ultrafine powder particles. The stirring time may be from 1 to 5 h, preferably from 2 to 3 h, after maintaining a suitable pH.

When adjusting the pH of the solution, a forward titration method may be employed in which ammonia water or an ammonium hydrogencarbonate solution is added dropwise to the mixed solution to precipitate the nanoparticles of the ZrO ₂ and the sintering aid. These nanoparticles will partially adhere to the surface of the phosphor particles and the surface of the Al ₂ O ₃ particles. Under the action of magnetic stirring, these precipitated suspended particles will mix very uniformly with the Al ₂ O ₃ nanoparticles in the suspension. Together. The dosage of the auxiliary agent added in this way can be smaller, the mixing is more uniform, and the effect is more remarkable.

<Coprecipitation method>

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

Step I: a step of mixing a mixed suspension of the Al ₂ O ₃ raw material powder and the phosphor with a solution of a precursor of ZrO ₂ and a solution of a precursor of the optional sintering aid, and then coprecipitating;

Step II: a step of centrifuging, washing, drying, calcining, and sieving the product obtained in the above step.

Step I

First, a citric acid-NaOH solution is prepared, then PEG4000 is added, and after ultrasonic dissolution, a phosphor and a nano-Al ₂ O ₃ powder are added, and after ultrasonic dispersion, the mixture is stirred on a magnetic stirrer to obtain a phosphor-Al ₂ O. ₃ mixed suspension. Wherein the phosphor with the Al ₂ O ₃ mass ratio of the phosphor _{:Al 2 O 3 = 1:4 ~ 9:1} .

The precursor of ZrO ₂ is formulated into a mixed salt solution together with the precursor of the sintering aid if present. The solution concentration may be from 0.01 to 1 mol/L. Here, examples of the precursor of ZrO _{2 and} the precursor of the sintering aid are the same as described above.

Mixing the phosphor-Al ₂ O ₃ mixed suspension obtained above with a precursor solution of ZrO ₂ and an optional sintering aid, stirring, and then adjusting the pH of the mixed solution by using ammonia water or ammonium hydrogencarbonate solution to obtain a total Precipitated composite powder suspension. This step is the same as in the step a' described in the above solid phase method.

Step II

The steps of centrifuging, drying, calcining, and sieving the product obtained in the above step I are the same as those in the step a' described in the above solid phase method. Thereby, a mixed powder of phosphor particles, an Al ₂ O ₃ matrix, ZrO ₂ particles and, if present, a sintering aid is obtained.

Further, in the above coprecipitation method, a mixed suspension of a phosphor and an Al ₂ O ₃ substrate is first prepared, and then mixed with a mixed solution of a precursor of ZrO _{2 and} a precursor of a sintering aid which is present. However, the order of addition of the raw materials is not limited thereto, and the mixed suspension of the Al ₂ O ₃ matrix may be mixed with the mixed solution of the precursor of ZrO _{2 and} the precursor of the sintering aid if present, and then with the phosphor. The suspension is mixed.

Step 2

Weighing an appropriate amount of the mixed powder of the phosphor particles, the Al ₂ O ₃ matrix, the ZrO ₂ particles and the optional sintering aid obtained in the step 1 into a high temperature resistant mold such as a graphite mold for pressing, followed by sintering, followed by furnace Cooling to obtain the luminescent ceramic composite of the present invention.

The sintering method may be a direct sintering method, a hot press sintering method or a spark plasma sintering method.

When the direct sintering method is employed, the mixed powder obtained in the step 1 is charged into a mold, and the sheet is pressed under a pressure of 20 to 40 MPa, and the obtained sample is subjected to cold isostatic pressing treatment at 200 MPa, and then the sample is placed in a sintering furnace. Internally, it is sintered under a protective atmosphere such as nitrogen, argon or hydrogen. The sintering temperature may be from 1,450 to 1,750 ° C, preferably from 1,550 to 1,650 ° C. The sintering time can be from 30 min to 20 h, preferably from 60 min to 10 h.

The hot press sintering method can greatly reduce the sintering temperature of the material by applying pressure while sintering, and is an ideal process for preparing the above materials. At the same time, the hot pressing method has a high heating rate, and a vacuum atmosphere or a protective gas atmosphere can be used, and it can be applied to sintering of various types of materials.

When the hot press sintering method is employed, the mixed powder obtained in the step 1 is charged into a mold, Pre-compression is carried out under a pressure of 5-15 MPa, and then the mold is placed in a hot press sintering furnace and sintered under vacuum or argon atmosphere. The sintering temperature may be from 1,250 to 1,650 ° C, preferably from 1,350 to 1,550 ° C; the sintering pressure is preferably from 30 to 200 MPa, preferably from 40 to 100 MPa, more preferably from 40 to 75 MPa; and the sintering time may be from 5 minutes to 6 hours, preferably from 30 minutes to 3 hours.

In addition to the characteristics of hot press sintering, the SPS technology of spark plasma sintering has its own characteristics. It can mainly heat the sample by pulse current to make the sample melt quickly. It is generally believed that SPS has the following densification pathways: (1) local high temperature is generated by discharge and ionization between grains, causing evaporation and melting on the surface of powder particles, directly promoting the process of densification; (2) pulse current Under the action of the powder particles, the surface of the powder particles is easily activated, and various diffusion effects are enhanced, thereby promoting the process of densification. In the plasma sintering of the discharge, each particle uniformly heats itself to activate the surface of the particle, thereby having high thermal efficiency, and the sintered body can be dense in a relatively short period of time, and the sintering temperature of the fine powder can be effectively reduced.

When sintering by the SPS method, the mixed powder obtained in the step 1 was charged into a mold, pre-compressed under a pressure of 5 to 15 MPa, and then the mold was placed in an SPS sintering furnace to be sintered under a vacuum atmosphere. The sintering temperature may be 1250 to 1550 ° C, preferably 1350 to 1450 ° C; the sintering time is 30 min to 6 h, preferably 60 min to 4 h; and the sintering pressure is 30 to 200 MPa, preferably 40 to 100 MPa.

As described above, by adding the luminescent ceramic containing ZrO ₂ Al ₂ O ₃ in the matrix, and the ZrO ₂ and Al ₂ O ₃ matrix and the phosphor sufficiently uniformly mixed, not only improve the performance of luminescent ceramic toughness, and do not The optical properties of the luminescent ceramic can be adversely affected. Thereby, the luminescent ceramic of the present invention has excellent characteristics of high light efficiency, high thermal conductivity, and adjustable blue light transmittance, and can be applied to a high performance laser light source, particularly a precision laser light source system.

Example

The invention is further illustrated by the following examples, but the invention is not limited to the following examples.

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

(1) Shooting of scanning electron microscope photographs

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

(2) Measurement of fracture toughness

In the present invention, the fracture toughness of the obtained luminescent ceramic is measured by a one-sided notched beam method. The sample size was height x width x length = 5 mm x 2.5 mm x 25 mm. After the sample was cut in the height direction into a slit having a depth of 2.5 mm and a width of less than 0.2 mm, a three-point bending test was performed, the span was 20 mm, and the indenter pressing rate was 0.05 mm·min ^-1 . The test was carried out on a DCS-5000 Shimadzu material testing machine. Record the breaking load P and calculate the fracture toughness value Kic according to the following formula:

Kic=PL/BW ^3/2 ·f(a/W)

Under the condition of the aspect ratio W/B=2 and the high span ratio W/L=1/4, the value of f(a/W) is 2.665.

Example 1 :

The raw material is high-purity ultrafine Al ₂ O ₃ nano powder with a particle size of 0.08-0.2 μm; high-purity ultra-fine nano ZrO ₂ powder with a particle size of 0.05-0.1 μm; high-purity commercial YAG:Ce ³⁺ fluorescence The powder has a particle size of 15 to 17 μm.

A certain amount of Al ₂ O ₃ powder and ZrO ₂ powder were weighed so that the content of the ZrO ₂ powder was 1% by mass of the Al ₂ O ₃ powder. The two powders were charged into a polytetrafluoroethylene ball mill jar, an appropriate amount of ethanol was added as a grinding solvent, and an appropriate amount of sodium silicate was added as a dispersing agent, and ball milling was performed with an ultra-low wear rate zirconia ball. The number of revolutions of the ball mill was 120r/min, ball milling time is 36h.

After the first ball milling, the YAG:Ce phosphor is added to the ball mill tank so that the mass percentage of the phosphor particles accounts for 20% by mass of the total powder, and the second ball milling is performed at a low speed, and the number of revolutions of the ball mill is 60 r/min. The ball milling time is 40 minutes. The total powder is the sum of Al ₂ O ₃ powder, ZrO ₂ powder and phosphor powder.

After the completion of the two ball millings, the dried powder was obtained by vacuum drying at 60 ° C under constant temperature. The dry powder was calcined at 500 ° C in a muffle furnace to remove organic components in the powder for 5 hours.

The calcined powder was granulated through a mesh of 80 mesh, 150 mesh, and 200 mesh to obtain a raw material powder having high fluidity.

Weigh the appropriate amount of raw material powder into the graphite mold, pre-compact under the pressure of 5MPa, then put the graphite mold into the hot press sintering furnace, sinter under argon atmosphere, sintering temperature 1500 ° C, heat preservation for 10 min, sintering pressure is 40MPa . After the sintering is completed, the pressure is removed and cooled with the furnace. Thus, a YAG-Al ₂ O ₃ -ZrO ₂ luminescent ceramic composite material, namely PIA-ZrO _{2 , was obtained} .

A scanning electron micrograph of the obtained luminescent ceramic is shown in Fig. 2. The circle in the figure is a YAG:Ce phosphor particle, and the black region is an alumina region. The particle size of the alumina is small, and is shown here as a continuous phase.

Further, the refractory toughness value of the luminescent ceramic obtained in the present example was 5.56 MPa·m ^1/2 .

Example 2 :

The Al ₂ O ₃ nanopowder and the YAG:Ce phosphor used in this example were the same as in Example 1. The Y ₂ O ₃ powder used was a high-purity ultrafine nano Y ₂ O ₃ powder having a particle diameter of 0.05 to 0.1 μm.

Weigh an appropriate amount of Al ₂ O ₃ powder, ZrO ₂ powder and Y ₂ O ₃ powder so that the content of the ZrO ₂ powder is 0.2% by mass of the Al ₂ O ₃ powder, and the content of the Y ₂ O ₃ powder is Al ₂ O ₃ 0.5% by mass of the powder. The three powders were charged into a polytetrafluoroethylene ball mill jar, an appropriate amount of ethanol was added as a grinding solvent, and an appropriate amount of sodium silicate was added as a dispersing agent, and the ball mill was ball milled with an ultra-low wear rate zirconia ball. 120r/min, ball milling time is 36 hours.

After the end of the first ball milling, an appropriate amount of YAG:Ce phosphor was added to the ball mill tank so that the mass percentage of the phosphor particles accounted for 50% by mass of the total powder. The second ball milling was carried out at a low speed, the number of revolutions of the ball mill was 60 r/min, and the ball milling time was 40 min. The total powder is the sum of Al ₂ O ₃ powder, ZrO ₂ powder, Y ₂ O ₃ powder, and phosphor powder.

After the completion of the two ball millings, the dried powder was obtained by vacuum drying at 60 ° C under constant temperature. The dry powder was calcined at 650 ° C in a muffle furnace to remove organic components in the powder for 1 hour.

The calcined powder was granulated through a mesh of 80 mesh, 150 mesh, and 200 mesh to obtain a raw material powder having high fluidity.

Weigh an appropriate amount of raw material powder into a graphite mold, pre-compact under a pressure of 15MPa, then place the graphite mold into a hot-pressing sintering furnace, and sinter it under an argon atmosphere. The sintering temperature is 1250 ° C, the heat preservation is 6 h, and the sintering pressure is 100 MPa. . After the sintering is completed, the pressure is removed and cooled with the furnace. Thus, a YAG-Al ₂ O ₃ -ZrO ₂ -Y ₂ O ₃ luminescent ceramic composite material, namely PIA-ZrO ₂ -Y ₂ O _{3 , was obtained} .

Example 3 :

The Al ₂ O ₃ nanopowder and the YAG:Ce phosphor used in this example were the same as in Example 1.

An appropriate amount of phosphor and high-purity Al ₂ O ₃ nanopowder were weighed according to the mass ratio of phosphor:Al ₂ O ₃ = 1: ₃ .

Prepare a citric acid-NaOH solution with a pH of 5.0 at a concentration of 1.0 mol/L, then add 1.5% by mass of PEG4000. After sonication, add the weighed YAG:Ce ³⁺ phosphor particles and nano-Al ₂ O ₃ After the powder is dispersed by ultrasonication, a magnetic stirrer is added and placed on a magnetic stirrer to stir continuously to obtain a phosphor-Al ₂ O ₃ mixed suspension, which is a solution one.

An appropriate amount of ZrOCl ₂ ·8H ₂ O was weighed in a ratio of ZrO ₂ :Al ₂ O ₃ =0.5% by mass:100% by mass, and ratio of Y ₂ O ₃ :Al ₂ O ₃ = 1% by mass: 100% by mass. An appropriate amount of Y(NO ₃ ) ₃ ·6H ₂ O was weighed, and the two nitrate hydrates were together formulated into a nitrate mixed solution having a concentration of 0.05 mol/L, which is the solution 2.

The solution two was added to the solution one to obtain a solution three, which was a mixed solution of YAG:Ce phosphor particles and a nano-Al ₂ O ₃ powder suspension + nitrate, and the stirring was continued using a magnetic stirrer. The temperature was set to 40 ° C and the speed was 250 r/m.

A 0.05 mol/L aqueous ammonia solution was prepared, and the mixed suspension 3 which was continuously stirred was slowly dropped until the pH of the mixed suspension was controlled to about 9. After maintaining the pH value, stirring was continued for 2.5 hours 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 ° C for 5 hours. The obtained dry powder is calcined at 500 ° C to remove impurities, and kept for 5 hours, and then air-cooled with the furnace to obtain a YAG-Al ₂ O ₃ -ZrO ₂ -Y ₂ O ₃ mixed powder, which is then sieved through 80 mesh, 150 mesh, and 200 mesh. Granules, which give high flow of raw material powder.

Weigh the appropriate amount of raw material powder into the mold, press it under the pressure of 40MPa, and then obtain the sample after 200MPa cold isostatic pressing treatment, then put the sample into the hydrogen sintering furnace, and sinter it under hydrogen atmosphere, the sintering temperature is 1750 °C. After heat preservation for 20 h, after sintering, the furnace was cooled to obtain a light-emitting composite ceramic material YAG-Al ₂ O ₃ -ZrO ₂ -Y ₂ O ₃ , that is, PIA-ZrO ₂ -Y ₂ O ₃ .

Example 4:

The Al ₂ O ₃ nanopowder and the YAG:Ce phosphor used in this example were the same as in Example 1.

A 1.5% by mass aqueous solution of PEG was prepared, and an appropriate amount of Al ₂ O ₃ nanopowder was mixed with an aqueous solution of PEG, and the Al ₂ O ₃ solution was ultrasonicated for 1.5 hours and then used as a solution. Ultrasound is to destroy the secondary agglomeration between the particles, allowing the powder to disperse as much as possible in the solution.

An appropriate amount of ZrOCl ₂ ·8H ₂ O was weighed in a ratio of ZrO ₂ :Al ₂ O ₃ =3 mass%:100 mass%, and (MgO+Y ₂ O ₃ ):Al ₂ O ₃ =3 mass%:100 For the ratio of mass %, weigh an appropriate amount of Mg(NO ₃ ) ₂ ·6H ₂ O and Y(NO ₃ ) ₃ ·6H ₂ O, where Mg(NO ₃ ) ₂ ·6H ₂ O and Y(NO ₃ ) ₃ · The mass percentage ratio of 6H ₂ O is 1:2. The three nitrates were dissolved together in deionized water to prepare a nitrate solution having a concentration of 0.05 M, in addition to solution two.

The solution one was mixed with the solution two to obtain a mixed suspension three, which was placed on a magnetic stirrer and continuously stirred, and the temperature was set to 60 ° C, and the rotation speed was 250 r / m.

Ammonium bicarbonate was used as a precipitant to prepare an aqueous solution of about 0.05 mol/L, and the mixed suspension 3 which was continuously stirred was slowly dropped until the pH of the mixed suspension was controlled to about 9. After maintaining a suitable pH value, stirring was continued for 2.5 hours to obtain a coprecipitated composite powder suspension.

The suspension was centrifuged, and the obtained powder was washed with water 4 times, and then vacuum dried at 80 ° C for 5 hours. The obtained dry powder is calcined at 500 ° C to remove impurities, and kept for 5 h, and then air-cooled to obtain an Al ₂ O ₃ -ZrO ₂ -Y ₂ O ₃ -MgO mixed powder, which is then sieved through 80 mesh, 150 mesh, and 200 mesh. grain.

An appropriate amount of Al ₂ O ₃ -ZrO ₂ -Y ₂ O ₃ -MgO mixed powder and YAG:Ce phosphor were weighed so that the mass ratio of the total powder:YAG:Ce phosphor was 2:1. The two powders were placed in a Teflon ball mill jar, and an appropriate amount of ethanol was added as a grinding solvent. No dispersing agent was used, and ball milling was performed with an ultra-low wear rate zirconia ball, and the ball milling time was 30 min. The total powder is the sum of Al ₂ O ₃ powder, ZrO ₂ powder, Y ₂ O ₃ powder, MgO powder, and phosphor powder.

After the ball milling is finished, the dry powder is obtained by vacuum drying at 60 ° C, and then 80 mesh, 150 mesh, The 200 mesh sieve was granulated to obtain a high fluidity raw material powder.

Weigh an appropriate amount of raw material powder into a graphite mold, pre-compact at a pressure of 5 MPa, then place the graphite mold into an SPS sintering furnace, and sinter it in a vacuum atmosphere at a sintering temperature of 1,450 ° C for 3 h, and a sintering pressure of 80 MPa. After the sintering is completed, the pressure is removed and cooled with the furnace to obtain a light-emitting composite ceramic material YAG-Al ₂ O ₃ -ZrO ₂ -Y ₂ O ₃ -MgO, that is, PIA-ZrO ₂ -Y ₂ O ₃ -MgO.

Example 5:

The luminescent ceramic of Example 5 was prepared in the same manner as in Example 1 except that the mass percentage of the phosphor particles was 90% by mass based on the total powder.

Comparative example 1:

The luminescent ceramic of Comparative Example 1 was prepared in the same manner as in Example 1 except that ZrO _{2 was} not added. The fracture toughness value of the luminescent ceramic obtained in Comparative Example 1 was Kic = 4.59 MPa·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, the fracture toughness value of Example 1 was higher than the fracture toughness value of Comparative Example 1 by about 20%. It can be seen that by sufficiently mixing the ZrO ₂ particles and the phosphor with the Al ₂ O ₃ matrix and uniformly dispersing in the Al ₂ O ₃ matrix, the toughness of the luminescent ceramic is greatly improved, and the luminescent ceramic is not adversely affected. The optical properties, and ZrO ₂ as a scattering particle can play the role of homogenizing incident light.

Although the present application has been described in detail with reference to the exemplary embodiments, it is understood that the invention is not limited thereto. Modifications or improvements made by those skilled in the art without departing from the scope of the invention are considered to be within the scope of the invention.

Claims (11)

1. A luminescent ceramic characterized by comprising an Al ₂ O ₃ matrix, ZrO ₂ particles, and phosphor particles.
2. The luminescent ceramic according to claim 1, wherein said phosphor particles are uniformly dispersed in said Al ₂ O ₃ matrix; said ZrO ₂ particles are dispersed between grain boundaries of said Al ₂ O ₃ matrix.
3. The luminescent ceramic according to claim 1 or 2, wherein the content of the ZrO ₂ particles is 0.05 to 5% by mass based on the mass of the Al ₂ O ₃ substrate.
4. The luminescent ceramic according to claim 1, wherein a mass ratio of said phosphor particles to said Al ₂ O ₃ matrix is from 1:4 to 9:1.
5. The luminescent ceramic according to claim 1, wherein said ZrO ₂ particles have a particle diameter of 0.05 to 1 μm; said phosphor particles have a particle diameter of 10 to 50 μm; and said Al ₂ O ₃ matrix has a crystal grain size 0.05 to 5 μm;

   and / or,

   The raw material powder of the ZrO ₂ particles has a particle diameter of 0.05 to 0.7 μm; the raw material powder of the phosphor particles has a particle diameter of 10 to 25 μm; and the Al ₂ O ₃ raw material powder has a particle diameter of 0.05 to 1 μm.
6. The luminescent ceramic according to claim 5, wherein the ZrO ₂ particles have a particle diameter of from 0.05 to 0.35 μm.
7. The luminescent ceramic according to claim 1, further comprising a sintering aid, and the sintering aid is at least selected from the group consisting of Y ₂ O ₃ , MgO, CaO, SiO ₂ , TiO ₂ , BaO, CaF ₂ , BaF ₂ One.
8. A method of preparing a luminescent ceramic according to claim 1, comprising the steps of:

   Step 1: a preparation step of a mixed powder comprising an Al ₂ O ₃ matrix, ZrO ₂ particles, and phosphor particles;

   Step 2: a step of pressing and sintering the above mixed powder to obtain a luminescent ceramic.
9. The preparation method according to claim 8, wherein said step 1 comprises the following steps:

   Step a: a preparation step of a mixed powder of the Al ₂ O ₃ substrate and the ZrO ₂ particles and an optional sintering aid;

   Step b: a step of mixing the above mixed powder with the phosphor particles, ball milling, drying, and sieving.
10. The production method according to claim 9, wherein said step a is replaced by step a', which comprises: suspending a raw material powder of said Al ₂ O ₃ matrix with a precursor of ZrO ₂ a step of mixing and coprecipitating a solution of the solution and the precursor of the optional sintering aid; and a step of centrifuging, washing, drying, calcining and sieving the obtained product.
11. The preparation method according to claim 8, wherein said step 1 comprises the following steps:

    Step I: a step of mixing a mixed suspension of an Al ₂ O ₃ raw material powder and a phosphor with a solution of a precursor of ZrO _{2 and} a precursor of a precursor of a sintering aid, and then coprecipitating;

    Step II: a step of centrifuging, washing, drying, calcining, and sieving the product obtained in the step I.

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