Multiphase fluorescent ceramic, method for preparing the same, and light emitting device

Abstract

The present application protects a kind of multiphase fluorescent ceramic and its preparation method and light emitting device, multiphase fluorescent ceramic includes fluorescent powder particle and the cladding layer of wrapping the fluorescent powder particle and the adhesive phase particle for the adhesive fluorescent powder particle with cladding layer and its preparation method;The fluorescent ceramic can realize high brightness high efficiency, also can realize high thermal conductivity and high reliability.

Description

Technical Field

[0001] This invention relates to the field of fluorescent ceramics, and in particular to a multiphase fluorescent ceramic, its preparation method, and a light-emitting device. Background Technology

[0002] Currently, with the development of the laser projection field, laser products are required to be smaller, brighter, and more efficient. This means that the size of the internal wavelength conversion device needs to be smaller, the laser power density that the emitting layer can withstand needs to be larger, and the requirements for the heat resistance and thermal conductivity of the entire encapsulated phosphor layer need to be improved. Among these, the serious thermal quenching problem of red phosphors has always been a technical challenge that needs to be solved in this field.

[0003] Existing red phosphor layers are generally encapsulated using silicone or glass. However, silicone encapsulation technology has poor thermal conductivity, generates more heat, and exacerbates the thermal quenching effect of the fluorescent material, thus reducing wavelength conversion efficiency; glass-encapsulated red phosphors are easily oxidized and decomposed at high temperatures, have poor thermal stability, and low luminous efficiency. Summary of the Invention

[0004] To address the problems of severe thermal quenching, low luminous efficiency, and poor thermal stability in the existing technologies, this invention provides a multiphase fluorescent ceramic, comprising phosphor particles, a coating layer encapsulating the phosphor particles, and bonding phase ceramic particles for bonding the phosphor particles with the coating layer.

[0005] In one embodiment, the phosphor particles are nitride red phosphor particles.

[0006] In one embodiment, the nitride red powder particles have a brick-like shape.

[0007] In one embodiment, the phosphor particles are oriented.

[0008] In one embodiment, the phosphor particles are oriented along their 002 crystal plane.

[0009] In one embodiment, the coating layer is an amorphous aluminum oxide or an amorphous silicon oxide layer, and the thickness of the coating layer is 1 nm to 100 nm.

[0010] In one embodiment, the binder ceramic particles are α-phase alumina ceramic particles.

[0011] In one embodiment, the present invention also provides a method for preparing multiphase fluorescent ceramics, comprising the following steps:

[0012] Prepare phosphor particles and binder phase ceramic particles;

[0013] A coating layer is formed on the surface of the phosphor particles to encapsulate them;

[0014] Phosphor particles with a coating layer are mixed with binder ceramic particles and formed into a green body.

[0015] The raw preform was sintered in an SPS discharge plasma sintering furnace at 1300℃~1500℃ for 3min~60min.

[0016] In one embodiment, phosphor particles with a coating layer are mixed with binder phase ceramic particles, and then a directional magnetic field is applied to cause the phosphor particles with the coating layer to oriented.

[0017] In one embodiment, the present invention also provides a light-emitting device comprising an excitation light source and the aforementioned multiphase fluorescent ceramic.

[0018] Compared with existing technologies, this application forms fluorescent ceramics by coating phosphor particles with a coating layer and then uniformly mixing and sintering them with binder phase ceramic particles. This provides a multiphase fluorescent ceramic capable of achieving high brightness, high efficiency, high thermal conductivity, and high stability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a multiphase fluorescent ceramic according to an embodiment of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] Please refer to Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of a multiphase fluorescent ceramic according to an embodiment of the present invention. The multiphase fluorescent ceramic includes phosphor particles 101, a coating layer 102 that encapsulates the phosphor particles 101, and adhesive phase ceramic particles 103 for bonding the phosphor particles 101 having the coating layer 102.

[0022] In some embodiments, the phosphor particles 101 may be yellow, green, or red phosphor particles, such as YAG:Ce. 3+ LSN:Ce 3+ LuAG:Ce 3+ (Sr,Ca)AlSiN3:Eu 2+ Furthermore, the phosphor particles 101 can be red nitride phosphor particles, specifically (Sr,Ca)AlSiN3:Eu 2+Phosphor particles, etc. Because the performance of phosphor particles is easily degraded at high temperatures—for example, red nitride phosphor particles are prone to thermal decomposition above 600℃—and easily react chemically with binder materials such as glass powder in oxide systems at high temperatures, making it impossible to prepare fluorescent materials with high luminous efficiency. Furthermore, when using fluorescent materials in high-power-density excitation light sources, the performance of phosphor particles is also easily degraded at high operating temperatures. Therefore, by using a coating layer 102 to encapsulate the phosphor particles 101, thermal decomposition of the phosphor particles 101 can be effectively avoided at temperatures above 600℃ during preparation, and reactions between the phosphor particles 101 and the binder ceramic particles 103 can be prevented. This also effectively reduces the possibility of performance degradation when using high-power-density excitation light sources.

[0023] In some embodiments, the red nitride phosphor particles may be selected as brick-shaped red nitride phosphor particles, such as brick-shaped red nitride phosphor particles prepared by a pressure method. In this application, brick-shaped refers to a shape that is rectangular or substantially rectangular.

[0024] In some embodiments, the phosphor particles 101 can be oriented. Further, the phosphor particles 101 can be oriented along their 002 crystal plane. Since the phosphor particles 101 may have different properties in different directions, such as surface area and crystallinity, by oriented the phosphor particles 101, especially by orienteding them along their 002 crystal plane (e.g., red nitride phosphor particles), the 002 crystal plane has the largest surface area and the best crystallinity compared to other crystal planes, thus exhibiting higher luminous efficiency under high power density laser excitation. Combined with the high thermal conductivity of the ceramic binder phase, high brightness, high luminous efficiency, and high stability can be achieved. Understandably, since multiphase fluorescent ceramic particles are generally in sheet form during use, to achieve better thermal conductivity, brightness, luminous efficiency, and stability, the oriented direction can be selected to be parallel to the plane of the sheet-like multiphase fluorescent ceramic. Of course, it is not required that all phosphor particles must be arranged in the exact same direction. Furthermore, when 40-99% of the total number of phosphor particles (such as the long side of brick-shaped phosphor particles) are within the range of 0-30 degrees with the preset orientation direction (such as the 002 crystal plane direction), they can also have a better effect.

[0025] In some embodiments, the coating layer 102 may be an inorganic oxide material, such as an amorphous dense alumina layer or an amorphous dense silicon oxide layer, and may further be an amorphous dense alumina layer. The coating layer 102 can improve the heat resistance and stability of the phosphor particles 101. In addition, since the sintering activity of red nitride phosphor particles is low, it is difficult to obtain high-density and high-efficiency red light ceramics. The efficiency of current red light ceramics is only about 60% of that of red nitride phosphors. By coating the surface of the phosphor particles 101 with an inorganic oxide material coating layer 102, the coating layer 102 and the binder phase ceramic particles 103 have better sintering activity, which is beneficial to the densification of the prepared multiphase fluorescent ceramic. Moreover, during the sintering preparation process, the coating layer 102 can prevent the phosphor particles 101 and the binder phase ceramic particles 103 from reacting, thereby improving the luminescence efficiency of the multiphase fluorescent ceramic. Furthermore, when the coating layer 102 and the binder ceramic particles 103 are made of the same material, such as alumina, the sintering activity can be further improved, thereby enhancing the compactness, luminous efficiency and thermal conductivity of the multiphase fluorescent ceramic.

[0026] If the coating layer 102 is too thin, it will not provide protection; if it is too thick, it will affect the transmittance and thus the light efficiency. After a large number of experiments, the applicant found that the thickness of the coating layer 102 is 1nm to 100nm, which can meet the requirements of light transmittance and protection of phosphor particles, such as 2nm, 10nm, 15nm, 30nm, 50nm, 70nm, 90nm, etc. The thickness of the coating layer 102 can be further reduced to 2nm to 50nm.

[0027] In some embodiments, the binder phase ceramic particles 103 may be selected from ceramic particles such as alumina, magnesium oxide, zinc oxide, and zirconium oxide. Further, the binder phase ceramic particles 103 may be α-phase alumina ceramic particles, which have high sintering activity and thermal conductivity, and can be used to prepare multiphase fluorescent ceramics with high density and thermal conductivity. In some embodiments, the particle size of the binder phase ceramic particles 103 may be 100 nm to 500 nm, and more specifically 150 nm to 300 nm. The binder phase ceramic particles 103 act as a binder for the phosphor particles 101, and have better thermal conductivity than glass powder, effectively reducing fluorescence quenching caused by heat accumulation. Furthermore, the sintered ceramic binder phase has higher transparency, which can further improve the luminous efficiency and lifespan of the fluorescent ceramic.

[0028] The proportion of phosphor particles 102 is not particularly limited in this application. In one embodiment, the mass of phosphor particles 102 may be 10-90% of the total mass of phosphor particles 102 and binder phase ceramic particles 103, and may be 20-80%.

[0029] The multiphase fluorescent ceramic of this application can achieve high brightness and high efficiency, as well as high thermal conductivity and high stability.

[0030] This application also relates to a method for preparing multiphase fluorescent ceramics, specifically including the following steps:

[0031] Prepare phosphor particles and binder phase ceramic particles.

[0032] The materials that can be used for phosphor particles and binder phase ceramic particles are as described above and will not be repeated here. They can be commercially available phosphor particles or binder phase ceramic particles, or they can be prepared by existing known methods. Before use, phosphor particles can be pretreated, such as by acid washing, water washing, and drying, to obtain phosphor particles with pure crystal surfaces, which can then be stored for later use.

[0033] A coating layer is formed on the surface of the phosphor particles to encapsulate them.

[0034] The phosphor particles can be coated with a coating layer using methods such as atomic layer deposition (ALD) or chemical vapor deposition (CVD). ALD is preferred, in which the coating layer, such as amorphous alumina, is deposited layer by layer onto the surface of the phosphor particles in the form of a single-atom film. During the deposition process, the chemical reaction of the new atomic film is directly related to the previous layer. This method ensures that only one atomic layer is deposited for each reaction, thus the thickness of the coating layer is controllable and the coating effect is good.

[0035] Phosphor particles with a coating layer are mixed with binder ceramic particles and formed into a green body.

[0036] In some embodiments, phosphor particles with a coating layer and binder phase ceramic particles can be ball-milled to form a mixed powder. The mixed powder can be directly molded into a green body using a mold, or a binder can be added to the mixed powder, followed by granulation, molding, and debinding to form a green body. Furthermore, the ratio of phosphor particles to binder phase ceramic particles can be selected according to a mass ratio of 10-90% of the total mass of phosphor particles and binder phase ceramic particles.

[0037] In some embodiments, the method further includes applying a directional magnetic field to a mixed powder formed by mixing phosphor particles with a coating layer and binder ceramic particles, thereby causing the phosphor particles with the coating layer to oriented and form an oriented mixed powder. For example, if the crystal of the red nitride phosphor particles is orthorhombic, when a directional magnetic field is applied, the (002) crystal plane of the red nitride phosphor particles experiences the greatest attraction from the magnetic field, causing the red nitride phosphor particles to oriented along their (002) crystal plane. Simultaneously, while applying the directional magnetic field to the mixed powder, the binder ceramic particles also play a role in oriented alignment, which is beneficial for densification of the binder ceramic particles, resulting in higher transparency of the sintered binder ceramic particles and higher thermal conductivity and luminous efficiency of the multiphase fluorescent ceramic. Alternatively, this oriented alignment can also be achieved through other methods such as vibration or centrifugation.

[0038] The green blank is sintered in an SPS discharge plasma sintering furnace at 1300℃~1500℃ for 3min~60min, or more specifically 3min~30min, or more specifically 3min~10min.

[0039] SPS (Spark Plasma Sintering) technology utilizes low-pressure argon gas introduced during pressure sintering to create argon plasma discharge within the particle interstices. This activates the powder, and the rapid, localized high temperature generated by the plasma also facilitates faster and denser sintering. Therefore, this rapid sintering technology enables the phosphor particles with coatings to form a dense sintered structure with the binder ceramic particles, while also reducing the chemical reaction between the phosphor particles and the binder ceramic particles, thus obtaining multiphase fluorescent ceramic materials with high luminous efficiency. Understandably, other steps may also be included, such as annealing, cutting, grinding, and polishing.

[0040] This application also provides a light-emitting device comprising an excitation light source and the multiphase fluorescent ceramic of any of the above embodiments. The excitation light source can be a light source in the form of a laser light source or a light-emitting diode light source. The light-emitting device can be specifically applied in fields such as projection display systems, lighting systems, or 3D display technology. The aforementioned multiphase fluorescent ceramic can be made into a fixed device or a moving device, such as a color wheel.

[0041] Example 1: Red-light multiphase fluorescent ceramic

[0042] The brick-shaped (Sr,Ca)AlSiN3:Eu was prepared using a pressure method. 2+ As phosphor particles, after acid washing, water washing, and drying, pure (Sr,Ca)AlSiN3:Eu crystals with clean grain surfaces are obtained. 2+ Nitride red phosphor particles. Subsequently, amorphous alumina was uniformly and densely deposited on (Sr,Ca)AlSiN3:Eu using atomic layer deposition.2+ Alumina coating layer with a thickness of 2 nm is formed on the surface of nitride red phosphor particles. Subsequently, α-phase alumina binder ceramic particles with a particle size of 150 nm are uniformly mixed with the amorphous alumina-coated nitride red phosphor particles to form a mixed powder, wherein the mass ratio of nitride red phosphor particles to alumina binder ceramic particles is 0.5:1. Under the action of a directional magnetic field, the coated (Sr,Ca)AlSiN3:Eu 2+ The red phosphor particles are oriented along their 002 crystal plane. Finally, the mixed powder is pressed into a blank, which is then sintered in an SPS discharge plasma sintering furnace at 1300℃ for 3 min to obtain nitride red light multiphase fluorescent ceramic.

[0043] Example 2: Red-light multiphase fluorescent ceramics

[0044] The brick-shaped (Sr,Ca)AlSiN3:Eu was prepared using a pressure method. 2+ As phosphor particles, after acid washing, water washing, and drying, pure (Sr,Ca)AlSiN3:Eu crystals with clean grain surfaces are obtained. 2+ Nitride red phosphor particles. Subsequently, amorphous alumina was uniformly and densely deposited on (Sr,Ca)AlSiN3:Eu using atomic layer deposition. 2+ Alumina coating layer with a thickness of 50 nm is formed on the surface of nitride red phosphor particles. Subsequently, α-phase alumina binder ceramic particles with a particle size of 300 nm are uniformly mixed with the amorphous alumina-coated nitride red phosphor particles to form a mixed powder. The mass ratio of nitride red phosphor particles to alumina binder ceramic particles is 0.5:1. Under the action of a directional magnetic field, the coated (Sr,Ca)AlSiN3:Eu 2+ The red phosphor particles are oriented along their 002 crystal plane. Finally, the mixed powder is pressed into a blank, which is then sintered in an SPS discharge plasma sintering furnace at 1400℃ for 10 min to obtain nitride red light multiphase fluorescent ceramic.

[0045] Example 3: White Light Multiphase Fluorescent Ceramics

[0046] The brick-shaped (Sr,Ca)AlSiN3:Eu was prepared using a pressure method. 2+ As phosphor particles, after acid washing, water washing, and drying, pure (Sr,Ca)AlSiN3:Eu crystals with clean grain surfaces are obtained. 2+ Nitride red phosphor particles. Subsequently, amorphous alumina was uniformly and densely deposited on (Sr,Ca)AlSiN3:Eu using atomic layer deposition. 2+The surface of the nitride red phosphor particles is coated with an alumina layer, and the thickness of the amorphous alumina coating layer is 100 nm.

[0047] Subsequently, red phosphor particles with a coating layer and yellow YAG:Ce were added. 3+ Fluorescent powder particles, green LuAG:Ce 3+ Phosphor particles and α-phase alumina binder ceramic particles with a particle size of 500 nm are uniformly mixed to form a mixed powder. The mass ratio of red phosphor particles, yellow phosphor particles, and green phosphor particles to alumina ceramic particles is 0.008:0.164:0.328:1. Under the action of a directional magnetic field, the (Sr,Ca)AlSiN3:Eu coated layer is formed. 2+ The red phosphor particles are oriented along their 002 crystal plane. Finally, the mixed powder is pressed into a blank, which is then sintered in an SPS discharge plasma sintering furnace at 1500℃ for 60 min to obtain white light multiphase fluorescent ceramic.

[0048] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A multiphase fluorescent ceramic, characterized in that, The fluorescent ceramic comprises phosphor particles, a coating layer encapsulating the phosphor particles, and adhesive phase ceramic particles for bonding the phosphor particles with the coating layer; the phosphor particles are oriented.

2. The multiphase fluorescent ceramic according to claim 1, characterized in that, The phosphor particles are nitride red phosphor particles.

3. The multiphase fluorescent ceramic according to claim 2, characterized in that, The nitride red powder particles have a brick-like crystal structure.

4. The multiphase fluorescent ceramic according to claim 1, characterized in that, The phosphor particles are oriented along their 002 crystal plane.

5. The multiphase fluorescent ceramic according to claim 1, characterized in that, The coating layer is an amorphous alumina layer or an amorphous silicon oxide layer.

6. The multiphase fluorescent ceramic according to claim 5, characterized in that, The thickness of the coating layer is 1 nm to 100 nm.

7. The multiphase fluorescent ceramic according to claim 1, characterized in that, The bonding phase ceramic particles are α-phase alumina ceramic particles.

8. A method for preparing multiphase fluorescent ceramics, characterized in that, Includes the following steps: Prepare phosphor particles and binder phase ceramic particles; A coating layer is formed on the surface of the phosphor particles to encapsulate the phosphor particles; The phosphor particles with a coating layer are mixed with the binder phase ceramic particles and formed into a blank; The green blank is sintered in an SPS discharge plasma sintering furnace at 1300℃~1500℃ for 3min~60min. The step of mixing the phosphor particles with the coating layer with the binder phase ceramic particles and forming a blank further includes: applying a directional magnetic field after mixing the phosphor particles with the coating layer with the binder phase ceramic particles to cause the phosphor particles with the coating layer to oriented.

9. A light-emitting device, characterized in that, The light-emitting device comprises an excitation light source and a multiphase fluorescent ceramic as described in any one of claims 1-7.

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