Fluorescent ceramic and preparation method therefor, and light-emitting device

Abstract

Provided in the present application is fluorescent ceramic, which comprises a substrate, fluorescent particles and a high-refractive-index phase, wherein the fluorescent particles are distributed in the substrate, and the high-refractive-index phase is distributed in the substrate. The high-refractive-index phase comprises at least one compound having general formula A2B2O7, where A is selected from any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and B is selected from any one of Ti, Zr and Hf. The ratio of the refractive index of the high-refractive-index phase to the refractive index of the fluorescent particles is greater than or equal to 1.1. By means of the fluorescent ceramic and the preparation method therefor provided in the present application, the high-refractive-index phase can effectively control light diffusion during a laser excitation process, thereby improving the efficient absorption and conversion of the fluorescent ceramic to incident laser and improving the comprehensive performance of a laser illumination fluorescent apparatus. In addition, further provided in the present application are a preparation method for the fluorescent ceramic, and a light-emitting device.

Description

Fluorescent ceramic, preparation method thereof and light-emitting device Technical Field

[0001] The present application relates to the field of luminescence technology, and in particular to a fluorescent ceramic, a preparation method thereof, and a luminescent device. Background Art

[0002] In recent years, with the rise of high-power blue laser diodes (LDs) as excitation light sources, the demand for high thermal conductivity in fluorescent materials has become more prominent, becoming a key technical challenge that urgently needs to be addressed in the development of high-power lighting devices. In contrast, fluorescent ceramic materials have a higher thermal conductivity coefficient, 5-10 times that of reference samples of phosphor-glass composite materials. Therefore, fluorescent ceramics are considered one of the most suitable fluorescent materials for high-power solid-state lighting. In addition, in addition to LEDs, the use of lasers as excitation light sources has advantages such as high brightness, long irradiation distance, higher conversion efficiency, and longer service life. However, the intensity distribution of the laser spot usually has the characteristics of a Gaussian distribution. After exciting the fluorescent material, the emitted light has an uneven light field problem. In addition, the light spot irradiated on the fluorescent ceramic expands laterally, causing light diffusion problems and reducing the effective light intensity. Therefore, it is necessary to design the optical performance of the fluorescent ceramic structure so that it can effectively reduce the lateral diffusion of the laser spot and improve the effective luminous flux of the light source. Summary of the Invention

[0003] The purpose of this application is to provide a fluorescent ceramic, a preparation method thereof, and a light-emitting device to improve the above-mentioned technical problems.

[0004] In a first aspect, an embodiment of the present application provides a fluorescent ceramic comprising a matrix, fluorescent particles, and a high refractive index phase, wherein the fluorescent particles are distributed in the matrix, and the high refractive index phase is distributed in the matrix, wherein the high refractive index phase comprises at least one compound having the general formula A2B2O7; wherein A is selected from any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and B is selected from any one of Ti, Zr, and Hf; and the ratio of the refractive index of the high refractive index phase to the refractive index of the fluorescent particles is greater than or equal to 1.1.

[0005] In some embodiments, the high refractive index has a refractive index of 2.0-2.5 relative to light having a wavelength of 400 nm-600 nm.

[0006] In some embodiments, the volume of the high refractive index phase accounts for 1% to 20% of the total volume of the phosphor ceramic.

[0007] In some embodiments, the high refractive index phase is coated on the surface of the fluorescent particles.

[0008] In some embodiments, the average thickness of the high refractive index phase coated on the surface of the fluorescent particles is 400 nm to 700 nm.

[0009] In some embodiments, the refractive index of the fluorescent particles is 1.4-1.9.

[0010] In some embodiments, the matrix is ​​selected from one or more of Al2O3, MgO, γ-AlON, BN, AlN, and Si3N4.

[0011] In some embodiments, the fluorescent particles are oxides, the matrix is ​​selected from at least one of Al2O3 and MgO, or; the fluorescent particles are nitrides, the matrix is ​​selected from at least one of γ-AlON, BN and AlN, or; the fluorescent particles are β-Sialon:Eu 2+ , the matrix is ​​selected from γ-AlON.

[0012] In some embodiments, the fluorescent ceramic further includes a grain boundary phase, wherein the grain boundary phase is distributed between the high refractive index phase and the matrix.

[0013] In some embodiments, the volume of the grain boundary phase accounts for 1% to 5% of the total volume of the phosphor ceramic.

[0014] In some embodiments, the grain boundary phase is formed by a reaction between a portion of the high refractive index phase and the matrix during the sintering process.

[0015] In some embodiments, the fluorescent ceramic further includes a plurality of pores, and the sum of the volumes of the plurality of pores is less than 5% of the total volume of the fluorescent ceramic.

[0016] In a second aspect, the embodiments of the present application also provide a method for preparing the above-mentioned fluorescent ceramics, comprising mixing a high refractive index phase with fluorescent particles, adding a dispersant and a binder, stirring evenly to form a slurry, and vacuum drying to obtain a composite powder; mixing the composite powder with a matrix and pre-sintering the mixture, and sintering to form a fluorescent ceramic.

[0017] In some embodiments, the particle size of the high refractive index phase preform is 0.4 μm to 1 μm.

[0018] In a third aspect, an embodiment of the present application further provides a light-emitting device, comprising an excitation light source and the above-mentioned fluorescent ceramic, wherein the excitation light source can emit excitation light for exciting the fluorescent ceramic to emit stimulated light.

[0019] The fluorescent ceramics and preparation methods provided in the present application, on the one hand, the high refractive index phase can effectively control the light diffusion during the laser excitation process, and improve the efficient absorption and conversion of the incident laser by the fluorescent ceramic. At the same time, due to the formation of a refractive index gradient between the high refractive index phase and the fluorescent particles, the light scattering during the excitation light excitation process can be improved, while the lateral diffusion of light in the fluorescent ceramic can be reduced, thereby improving the comprehensive performance of the fluorescent ceramic; on the other hand, the matrix is ​​tightly wrapped around the fluorescent particles, and can timely diffuse the heat generated by the fluorescent particles during the luminescence process, thereby improving the thermal stability of the fluorescent ceramic; through the design of the above-mentioned structure and components, the light power threshold of the fluorescent ceramic can be further improved, so that the comprehensive performance of the light-emitting device including the fluorescent ceramic is improved.

[0020] These and other aspects of the present application will become more readily apparent from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0022] FIG1 is a schematic structural diagram of a fluorescent ceramic provided in an embodiment of the present application.

[0023] FIG2 is a schematic structural diagram of a light-emitting device provided in Example 5 of the present application. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0025] Currently, the phosphor conversion materials used in laser lighting sources are typically porous YAG:Ce fluorescent ceramics or Al2O3-YAG:Ce composite fluorescent ceramics. Porous YAG:Ce fluorescent ceramics utilize pores as scattering centers to improve blue light absorption, achieving high light conversion efficiency. However, due to their low thermal conductivity, their power saturation threshold is low, making them difficult to withstand continuous high-power-density laser excitation. As laser spot size requirements decrease, the optical power per unit area increases, placing greater demands on the thermal dissipation performance of fluorescent ceramics. Currently, the use of Al2O3-YAG:Ce composite fluorescent ceramics is one of the solutions. The high thermal conductivity of Al2O3 ceramics is used to improve the thermal stability of YAG:Ce fluorescent ceramics. There are usually two ways to obtain Al2O3-YAG:Ce composite fluorescent ceramics. One is to co-sinter commercial YAG:Ce phosphor powder with Al2O3 powder. The other is to weigh Y2O3, CeO2 and excess Al2O3 powder in a certain proportion, and then fully mix them to prepare YAG:Ce ceramics containing excess Al2O3, that is, Al2O3-YAG:Ce composite fluorescent ceramics. Among them, the first type of composite ceramics, although its alumina phase has high thermal conductivity and mechanical strength, the alumina phase is the main phase matrix, which occupies most of the volume, is not conducive to the effective absorption of blue laser by the phosphor and affects its effective conversion to blue laser; and the refractive index of the alumina matrix and the yttrium aluminum garnet fluorescent particle ceramic is close, and the scattering effect on the incident blue laser is insufficient, which is not conducive to reducing the lateral diffusion of the laser spot, and cannot effectively improve the blue light absorption rate, making it difficult to obtain a uniform light field and a higher luminous flux.

[0026] There is an urgent need to design a composite fluorescent ceramic material with a refractive index gradient. Based on this, the inventors of this application propose a fluorescent ceramic, a preparation method thereof, and a light-emitting device in order to improve the above technical problems, which will be described in detail below with reference to the accompanying drawings.

[0027] 1 , the present application provides a fluorescent ceramic 10 comprising a matrix 100, fluorescent particles 200 distributed within the matrix 100, and a high-refractive-index phase 300 distributed within the matrix 100. The high-refractive-index phase comprises at least one compound having the general formula A2B2O7; wherein A is selected from any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and B is selected from any one of Ti, Zr, and Hf. The ratio of the refractive index of the high-refractive-index phase to the refractive index of the fluorescent particles is greater than or equal to 1.1.

[0028] As a more specific embodiment, the high refractive index phase 300 includes at least one compound having the general formula A2B2O7, that is, the high refractive index phase 300 may include only one compound having the general formula A2B2O7, or may include multiple compounds having the general formula A2B2O7, where multiple refers to two or more compounds.

[0029] Among them, A can be selected from any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and B can be selected from any one of Ti, Zr and Hf. For example, in some embodiments of the present application, the high refractive index phase 300 can include one or more of La2Ti2O7, Lu2Ti2O7, Y2Hf2O7, etc. La2Ti2O7, Lu2Ti2O7, and Y2Hf2O7 are transparent high refractive index materials. In the present application, the high refractive index phase itself does not participate in the excitation of the excitation light to form the stimulated light, but its own high refractive index and high transparency properties cause the excitation light incident on the interior of the fluorescent ceramic to be scattered by it, so that the excitation light contacts more fluorescent particles after scattering, thereby increasing the number of fluorescent particles participating in the excitation process and improving the excitation efficiency of the excitation light.

[0030] The ratio of the refractive index of the high-refractive-index phase 300 to the refractive index of the phosphor particles is greater than or equal to 1.1, meaning the refractive index of the high-refractive-index phase 300 is greater than that of the phosphor particles 200. The refractive index refers to the refractive index of the excitation light incident on the phosphor ceramic and the converted stimulated light, specifically for light with a wavelength of 400nm-600nm. Because the high-refractive-index phase 300 has a higher refractive index than the phosphor particles 200, it forms a refractive index gradient with the phosphor particles 200. This improves light scattering during the excitation light excitation process and reduces lateral light diffusion within the phosphor ceramic, thereby enhancing the overall performance of the phosphor ceramic.

[0031] In some embodiments of the present application, the high refractive index phase 300 can be uniformly or unevenly distributed in the matrix; the high refractive index phase 300 can also be adhered to or coated on the outer surface of the fluorescent particle 200; the high refractive index phase 300 can also be partially adhered to or coated on the outer surface of the fluorescent particle 200, or can be partially uniformly or unevenly distributed in the matrix.

[0032] The high-refractive-index phase has a refractive index of 2.0-2.5. In some embodiments of the present application, the high-refractive-index phase refers to a refractive index of 2.0-2.5 relative to light with a wavelength of 400nm-700nm. For example, in another embodiment of the present application, the high-refractive-index phase refers to a refractive index of 2.0-2.5 relative to blue light and yellow light with a wavelength of 400nm-600nm. In yet another embodiment of the present application, the refractive index of 2.0-2.5 of the high-refractive-index phase 300 refers to the refractive index of blue light with a wavelength of 400nm-470nm. The refractive index of the fluorescent particles 200 is generally between 1.4-1.9, thereby forming a refractive index gradient with the fluorescent particles 200. Therefore, when the excitation light is blue or yellow light, the excitation light scattering during the excitation process is improved (primarily longitudinally, parallel to the direction of the incident excitation light), while reducing the lateral diffusion of the excitation light spot within the fluorescent ceramic (perpendicular to the direction of the incident excitation light), thereby improving the overall performance of the fluorescent ceramic.

[0033] In some embodiments of the present application, the volume of the high refractive index phase 300 accounts for 1% to 20% of the total volume of the fluorescent ceramic. In another embodiment of the present application, the volume of the high refractive index phase 300 accounts for 5% to 10% of the total volume of the fluorescent ceramic, and more specifically, 5%, 6%, 8%, 10%, etc. It should be noted that in some embodiments of the present application, the inventors have discovered through long-term experiments that when the volume of the high refractive index phase 300 accounts for more than 20% (excluding 20%) of the total volume of the fluorescent ceramic, the total volume of the fluorescent particles 200 in the total volume of the fluorescent ceramic decreases, thereby reducing the luminous efficiency. In addition, due to the high refractive index of the high refractive index phase itself, when the content is too high, the reflectivity of light increases, and the incident excitation light will be reflected from the surface of the fluorescent ceramic and lost, thereby reducing the overall luminous efficiency of the fluorescent ceramic. When the volume of the high refractive index phase 300 accounts for less than 1% (not including 1%) of the total volume of the fluorescent ceramic, the light scattering during excitation will be insufficient, and the lateral diffusion of the excitation light spot will be insufficiently weakened, and the blue light extraction efficiency cannot be effectively improved. The high refractive index phase 300 can improve the density of the fluorescent ceramic. When its content is too low, the density of the fluorescent ceramic will be reduced, the pore content will increase, and the structural optimization of the fluorescent ceramic will be insufficient. The fluorescent particles 200 can generate excited light under the excitation of the excitation light. In particular, the fluorescent particles 200 can generate excited light in the visible light band under the excitation of blue light (440nm-470nm). In one embodiment, the fluorescent particles 200 can be selected from Y3Al5O 12 :Ce 3+ 、Lu3Al5O 12 :Ce 3+ 、Gd3(Al,Ga)5O 12 :Ce 3+ 、Lu3(Al,Ga)5O12 :Ce 3+ 、(Ca,Sr)SiAlN3:Eu 2+ (Ba,Sr)2Si5N8:Eu 2+ 、Sr[LiAl3N4]:Eu 2+ β-Sialon:Eu 2+ One or more of .

[0034] Among them, the particle size of the fluorescent particles 200 is in the range of 0.5μm to 40μm, preferably 5μm to 20μm. Preferably, the fluorescent particles 200 can be selected from particles with uniform particle morphology, which helps to evenly distribute the fluorescent particles 200 in the matrix 100. In addition, during the preparation process, the fluorescent particles 200 with uniform morphology are also more conducive to uniform mixing with the high refractive index phase 300, and facilitate the formation of a structure in which the high refractive index phase 300 covers the fluorescent particles 200.

[0035] Increasing the proportion of phosphor particles 200 can improve the conversion efficiency of the fluorescent ceramic. However, if the proportion of phosphor particles 200 in the fluorescent ceramic is too high, the corresponding matrix proportion will be too low. When the excitation light is irradiated on the fluorescent ceramic, the heat generated will accumulate too much. The low matrix proportion will not be able to conduct and diffuse the heat effectively, affecting the heat dissipation of the fluorescent ceramic and causing thermal quenching. Preferably, the total volume of the phosphor particles 200 can account for 20% to 80% of the total volume of the fluorescent ceramic. In some embodiments of the present application, the total volume of the phosphor particles 200 can account for 40% to 60% of the total volume of the fluorescent ceramic.

[0036] As a preferred embodiment, the high refractive index phase 300 can be coated on the surface of the fluorescent particle 200. This arrangement allows the high refractive index phase 300 to be as close to the fluorescent particle 200 as possible, thereby significantly improving the scattering effect of the incident excitation light in the high refractive index phase 300, which helps to reduce the lateral diffusion of the incident excitation light spot and thus improve the excitation efficiency of the excitation light. When the high refractive index phase 300 is farther away from the fluorescent particle 200 than the size of the fluorescent particle 200 itself but is distributed in the matrix (i.e., the high refractive index phase 300 does not coat the fluorescent particle 200), the high refractive index phase 300 has a weaker effect on improving the scattering effect of the incident excitation light and reducing the lateral diffusion of the excitation light spot than when the high refractive index phase 300 is as close to the fluorescent particle 200 as possible. At the same time, by coating the high refractive index phase 300 on the surface of the fluorescent particle 200, the high refractive index phase 300 can be prevented from agglomerating and aggregating during the preparation process, thereby avoiding the formation of a reflection center that loses blue light from the aggregated high refractive index phase. If the thickness of the high-refractive-index phase 300 coating the surface of the fluorescent particles 200 is too high, the incident excitation light will be reflected and unable to pass through the high-refractive-index phase to enter the fluorescent particles. This will reduce the efficiency and probability of contact between the excitation light and the fluorescent particles 200, thereby reducing the excitation efficiency. If the thickness is too small, the scattering effect will not be effective. Preferably, the average thickness of the high-refractive-index phase 300 coating the surface of the fluorescent particles 200 can be 400nm-700nm, for example, 500nm, 600nm, etc.

[0037] Specifically, the matrix 100 can be formed from a high thermal conductivity ceramic material, for example, a thermally conductive ceramic material having a thermal conductivity greater than or equal to 7 W / (mK). In one embodiment, the matrix 100 can be selected from one or more of Al2O3, MgO, γ-AlON, BN, AlN, and Si3N4. The refractive index of the matrix 100 is similar to that of the fluorescent particles 200. Since the matrix is ​​the primary phase, the volume of the matrix 100 accounts for more than 20% of the total volume of the fluorescent ceramic 10. If the refractive index of the matrix 100 forms a significant gradient difference with the refractive index of the fluorescent particles 200, this will cause the incident excitation light to be reflected and lost by the fluorescent ceramic 10. Therefore, the refractive index of the matrix 100 is selected to be similar to that of the fluorescent particles 200 (the difference is less than 0.15). In some embodiments of the present application, the refractive index of the matrix is ​​1.4-1.7. The matrix 100 tightly wraps the fluorescent particles 200 and the high refractive index phase 300. The matrix 100 can diffuse the heat generated by the fluorescent particles 200 and the high refractive index phase 300 during the light-emitting process, thereby improving the thermal stability of the fluorescent ceramic.

[0038] In order to improve the tightness of the interface between the matrix 100 and the fluorescent particles 200 during packaging, in one embodiment, different matrices 100 can be selected for different fluorescent particles 200. Specifically, a matrix 100 with physical and chemical properties closer to those of the fluorescent particles 200 is selected to improve the compatibility between the matrix 100 and the fluorescent particles 200. For example: when the fluorescent particles 200 are oxides, the matrix 100 can be selected from at least one of Al2O3 and MgO. For another example: when the fluorescent particles 200 are nitrides, the matrix 100 can be selected from at least one of γ-AlON, BN and AlN. For another example: when the fluorescent particles 200 are β-Sialon:Eu 2+ When , the matrix 100 can be selected from γ-AlON.

[0039] The high refractive index phase 300 can chemically react with the matrix 100 during the sintering process, and the product of the reaction process varies depending on the high refractive index phase 300 and the matrix 100 .

[0040] Furthermore, the fluorescent ceramic 10 may also include a grain boundary phase 400. This grain boundary phase 400 may be formed by a reaction between a portion of the high-refractive-index phase 300 and the matrix 100 during the sintering process, or by the addition of highly fluid grain boundary phase raw materials prior to preparation, which then enter the pores. This embodiment is not limited to this. The grain boundary phase 400 effectively reduces the porosity around the fluorescent particles 200 and the high-refractive-index phase 300, increasing the density of the ceramic and, in turn, improving the thermal conductivity of the fluorescent ceramic 10.

[0041] The formation of grain boundary phase 400 promotes the formation of a dense phase at the interface between high refractive index phase 300 and matrix 100, eliminating residual pores between high refractive index phase 300, phosphor particles 200, and matrix 100, or reducing the volume of the pores. This reduces the total volume of the pores in the phosphor ceramic, thereby increasing the density of the phosphor ceramic. The phosphor ceramic 10 also includes a plurality of pores. The total volume of the pores in the phosphor ceramic can be less than 5% of the total volume of the phosphor ceramic. In some embodiments of the present application, the volume of the pores in the phosphor ceramic can be less than 1%, 2%, 3%, 4%, or 5% of the total volume of the phosphor ceramic. In preferred embodiments of the present application, the volume of the pores in the phosphor ceramic can be less than 1% or 2% of the total volume of the phosphor ceramic.

[0042] The proportion of the grain boundary phase 400 to the total volume of the fluorescent ceramic 10 can be 1%-5%. Within this volume ratio range, the high refractive index phase 300 can be ensured to only partially react with the matrix 100, thereby ensuring that the volume content of the high refractive index phase 300 is moderate. At the same time, the matrix 100 can be well coated on the outside of the high refractive index phase 300. In addition, the total volume of the grain boundary phase 400 is related to the total volume of the pores remaining between the high refractive index phase 300 and the matrix 100, that is, the total volume of the grain boundary phase 400 + the volume of the pores in the finished fluorescent ceramic = the volume of the pores in the fluorescent ceramic without the grain boundary phase = the pores remaining between the high refractive index phase 300 and the matrix 100 during preparation.

[0043] The fluorescent ceramic 10 can be prepared as follows:

[0044] First, the high refractive index phase preform can be mixed with the fluorescent particles 200, and a dispersant and a binder are added during the mixing and stirred to form a slurry. During this process, the high refractive index phase preform is adsorbed on the surface of the fluorescent particles 200, wrapping and dispersing the fluorescent particles 200. After the slurry is vacuum dried, a composite powder is obtained for use.

[0045] Among them, the high refractive index phase preform can be prepared in advance, for example, in the following manner: according to the structure of the selected high refractive index phase 300 (i.e., the compound according to the general formula A2B2O7), the corresponding oxide raw material is selected, and after adding an additive, it is ground so that the oxide raw material is evenly distributed to form a primary slurry, and the primary slurry is calcined at a low temperature to form a high refractive index phase preform. Furthermore, the obtained high refractive index phase preform can also be ground to obtain a high refractive index phase preform with more uniform particle size and more stable particle morphology. The grinding method can be ball milling, which is not limited here.

[0046] In some embodiments of the present application, the particle size of the high-refractive-index phase preform is 0.4 μm to 1 μm. Within this size range, the particle size of the high-refractive-index phase preform is at the submicron level. The high-refractive-index phase preform can be evenly diffused, occupying the pores within the fluorescent ceramic, further improving the density of the fluorescent ceramic. Furthermore, during the preparation of the fluorescent ceramic, the high-refractive-index phase preform also serves as a sintering aid, promoting the densification of the fluorescent ceramic.

[0047] The composite powder is mixed with the matrix 100 and then pre-sintered. For example, the process can be as follows: the composite powder is mixed with the matrix 100 and then sieved, calcined at 500-800°C for at least 2 hours, and then cold isostatically pressed at 50-250 MPa to increase density; and after cold isostatic pressing, pre-sintered in air to remove organic additives or impurities.

[0048] After pre-sintering, the fluorescent ceramic is sintered. Sintering can be performed under the following conditions: hot pressing or spark plasma sintering in a vacuum or protective atmosphere, with a sintering temperature of 1400°C to 1700°C and a sintering pressure of 10 MPa to 100 MPa. During the sintering process, the high refractive index phase preform forms a high refractive index phase 300, and a portion of the high refractive index phase 300 chemically reacts with the matrix 100 to form a grain boundary phase 400.

[0049] After sintering, the resulting fluorescent ceramic 10 can be annealed. Specifically, the annealing process can be performed in air or an oxygen atmosphere at a temperature of 800°C to 1300°C for a holding time of 10 to 100 hours. Annealing eliminates internal stress within the fluorescent ceramic 10, preventing subsequent cracking or fissures in the fluorescent ceramic 10. After annealing, the fluorescent ceramic can be further ground, polished, and cut to the desired size, depending on the intended use.

[0050] The present application will be further described below with reference to specific embodiments.

[0051] Example 1

[0052] Select YAG:Ce 3+ As fluorescent particles, La2Ti2O7 serves as a high refractive index phase, a mixture of Al2O3 and MgO serves as a matrix, and part of the high refractive index phase reacts with the matrix to generate LaAlO3 as a grain boundary phase.

[0053] First, a high-refractive index phase preform is mixed with fluorescent particles. A dispersant and a binder are added during mixing and stirred until a slurry is formed. During this process, the high-refractive index phase preform adheres to the surface of the fluorescent particles and becomes evenly dispersed. The slurry is vacuum-dried to obtain a composite powder for later use. The composite powder is then mixed with the matrix, sieved, calcined at 500-800°C for at least 2 hours, and then cold isostatically pressed at 50-250 MPa. After this, it is pre-sintered in air to remove organic components.

[0054] Spark plasma sintering is performed under vacuum or a protective atmosphere at a sintering temperature of 1400° C. to 1700° C. and a sintering pressure of 10 MPa to 100 MPa to obtain a fluorescent ceramic. After sintering, the fluorescent ceramic 10 is annealed in air or an oxygen atmosphere at a temperature of 800° C. to 1300° C. for a holding time of 10 to 100 hours. The annealing can eliminate internal stress within the fluorescent ceramic 10.

[0055] Example 2

[0056] Select LuAG:Ce 3+As fluorescent particles, Lu2Ti2O7 serves as a high refractive index phase, a mixture of AlON and Al2O3 serves as a matrix, and part of the high refractive index phase reacts with the matrix to generate LuAlO3 as a grain boundary phase.

[0057] First, a high-refractive index phase preform is mixed with fluorescent particles. A dispersant and a binder are added during mixing and stirred until a slurry is formed. During this process, the high-refractive index phase preform adheres to the surface of the fluorescent particles and becomes evenly dispersed. The slurry is vacuum-dried to obtain a composite powder for later use. The composite powder is then mixed with the matrix, sieved, calcined at 500-800°C for at least 2 hours, and then cold isostatically pressed at 50-250 MPa. After this, it is pre-sintered in air to remove organic components.

[0058] Spark plasma sintering is performed under vacuum or a protective atmosphere at a sintering temperature of 1400° C. to 1700° C. and a sintering pressure of 10 MPa to 100 MPa to obtain a fluorescent ceramic. After sintering, the fluorescent ceramic 10 is annealed in air or an oxygen atmosphere at a temperature of 800° C. to 1300° C. for a holding time of 10 to 100 hours. The annealing can eliminate internal stress within the fluorescent ceramic 10.

[0059] Example 3

[0060] Select (Ca, Sr)SiAlN3:Eu 2+ As fluorescent particles, Lu2Ti2O7 serves as a high refractive index phase, a mixture of AlON and Al2O3 serves as a matrix, and part of the high refractive index phase reacts with the matrix to generate LaAlO3 as a grain boundary phase.

[0061] First, a high-refractive index phase preform is mixed with fluorescent particles. A dispersant and a binder are added during mixing and stirred until a slurry is formed. During this process, the high-refractive index phase preform adheres to the surface of the fluorescent particles and becomes evenly dispersed. The slurry is vacuum-dried to obtain a composite powder for later use. The composite powder is then mixed with the matrix, sieved, calcined at 500-800°C for at least 2 hours, and then cold isostatically pressed at 50-250 MPa. After this, it is pre-sintered in air to remove organic components.

[0062] Hot pressing sintering is performed under vacuum or protective atmosphere at a sintering temperature of 1400°C to 1700°C and a sintering pressure of 10 MPa to 100 MPa to obtain a fluorescent ceramic. After sintering, the fluorescent ceramic 10 is annealed. The annealing can be performed in air or an oxygen atmosphere at a temperature of 800°C to 1300°C for a holding time of 10 to 100 hours. The annealing can eliminate internal stress within the fluorescent ceramic 10.

[0063] Example 4

[0064] Select β-Sialon:Eu 2+ As fluorescent particles, Y2Hf2O7 serves as a high refractive index phase, a mixture of AlON and Al2O3 serves as a matrix, and part of the high refractive index phase reacts with the matrix to generate YAlO3 as a grain boundary phase.

[0065] First, a high-refractive index phase preform is mixed with fluorescent particles. A dispersant and a binder are added during mixing and stirred until a slurry is formed. During this process, the high-refractive index phase preform adheres to the surface of the fluorescent particles and becomes evenly dispersed. The slurry is vacuum-dried to obtain a composite powder for later use. The composite powder is then mixed with the matrix, sieved, calcined at 500-800°C for at least 2 hours, and then cold isostatically pressed at 50-250 MPa. After this, it is pre-sintered in air to remove organic components.

[0066] Spark plasma sintering is performed under vacuum or a protective atmosphere at a sintering temperature of 1400° C. to 1700° C. and a sintering pressure of 10 MPa to 100 MPa to obtain a fluorescent ceramic. After sintering, the fluorescent ceramic 10 is annealed in air or an oxygen atmosphere at a temperature of 800° C. to 1300° C. for a holding time of 10 to 100 hours. The annealing can eliminate internal stress within the fluorescent ceramic 10.

[0067] The fluorescent ceramics and preparation methods provided in the present application, on the one hand, the high refractive index phase can effectively control the light diffusion during the laser excitation process, thereby improving the efficient absorption and conversion of the incident laser by the fluorescent ceramics; on the other hand, the matrix tightly wraps around the fluorescent particles, which can timely diffuse the heat conduction generated by the light-emitting process of the fluorescent particles, thereby improving the thermal stability of the fluorescent ceramics; through the design of the above-mentioned structure and components, the light power threshold of the fluorescent ceramics can be further improved, thereby improving the comprehensive performance of laser lighting fluorescent devices.

[0068] Example 5

[0069] Referring to Figure 2, this embodiment provides a light-emitting device 1, which includes a laser light source 20 and a fluorescent ceramic 10. The laser light source 20 emits excitation light to excite the fluorescent ceramic 10 to emit stimulated light, wherein the fluorescent ceramic 10 can be any one of the aforementioned embodiments. For details, please refer to the relevant content of the aforementioned embodiments.

[0070] The laser light source 20 may be, for example, a blue light source. In some other implementations, the laser light source 20 may also be a light source of other colors, which is not limited in this embodiment.

[0071] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A fluorescent ceramic, characterized in that: include: Matrix; fluorescent particles distributed in the matrix; as well as A high refractive index phase, wherein the high refractive index phase is distributed in the matrix; Wherein, the high refractive index phase includes at least one compound having the general formula A2B2O7; wherein A is selected from any one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and B is selected from any one of Ti, Zr and Hf; the ratio of the refractive index of the high refractive index phase to the refractive index of the fluorescent particles is greater than or equal to 1.

1.

2. The fluorescent ceramic according to claim 1, characterized in that: The high refractive index is 2.0-2.5 relative to the light with a wavelength of 400nm-600nm.

3. The fluorescent ceramic according to claim 1, characterized in that: The volume of the high refractive index phase accounts for 1% to 20% of the total volume of the fluorescent ceramic.

4. The fluorescent ceramic according to any one of claims 1 to 3, characterized in that: The high refractive index phase is coated on the surface of the fluorescent particles.

5. The fluorescent ceramic according to claim 4, characterized in that: The average thickness of the high refractive index phase coated on the surface of the fluorescent particle is 400nm-700nm.

6. The fluorescent ceramic according to claim 2, characterized in that: The refractive index of the fluorescent particles is 1.4-1.

9.

7. The fluorescent ceramic according to claim 1, characterized in that: The matrix is ​​selected from one or more of Al2O3, MgO, γ-AlON, BN, AlN, and Si3N4.

8. The fluorescent ceramic according to claim 7, characterized in that: The fluorescent particles are oxides, and the matrix is ​​selected from at least one of Al2O3 and MgO, or; The fluorescent particles are nitrides, and the matrix is ​​selected from at least one of γ-AlON, BN and AlN, or; The fluorescent particles are β-Sialon:Eu 2+ , the matrix is ​​selected from γ-AlON.

9. The fluorescent ceramic according to claim 1, characterized in that: The fluorescent ceramic further includes a grain boundary phase distributed between the high refractive index phase and the matrix.

10. The fluorescent ceramic according to claim 9, characterized in that: The volume of the grain boundary phase accounts for 1% to 5% of the total volume of the fluorescent ceramic.

11. The fluorescent ceramic according to claim 9, characterized in that: The grain boundary phase is formed by the reaction of a portion of the high refractive index phase and the matrix during the sintering process.

12. The fluorescent ceramic according to claim 9, characterized in that: The fluorescent ceramic further comprises a plurality of pores, and the sum of the volumes of the plurality of pores is less than 5% of the total volume of the fluorescent ceramic.

13. The method for preparing the fluorescent ceramic according to any one of claims 1 to 12, characterized in that: include: The high refractive index phase preform is mixed with fluorescent particles, a dispersant and a binder are added, and the mixture is stirred evenly to form a slurry, and then vacuum dried to obtain a composite powder; The composite powder is mixed with a matrix and then pre-sintered to form a fluorescent ceramic.

14. The method according to claim 13, characterized in that: The particle size of the high refractive index phase preform is 0.4 μm to 1 μm.

15. A light-emitting device, comprising an excitation light source and the fluorescent ceramic according to any one of claims 1 to 12, wherein the excitation light source can emit excitation light for exciting the fluorescent ceramic to emit stimulated light.

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