One-step tape casting method for high density fluorescent ceramic

Abstract

This invention provides a one-step casting method for preparing high-density fluorescent ceramics, comprising the following steps: S1, mixing powder raw materials, oxygen vacancy eliminators, sintering aids, solvents, and dispersants in proportion, and ball milling for a period of time to obtain slurry A; the powder raw materials are Ce-doped garnet-based fluorescent materials and / or nitride fluorescent materials; the oxygen vacancy eliminators include one or more of feldspar, kaolin, and zeolite; S2, adding binders, plasticizers, and homogenizers in proportion to slurry A, and continuing ball milling for a period of time to obtain slurry B; S3, filtering slurry B, degassing under vacuum to obtain casting slurry, and casting the casting slurry to obtain casting green body; S4, drying the casting green body, and performing debinding treatment under a certain atmosphere and temperature; finally, sintering at high temperature to obtain high-density fluorescent ceramics. This invention achieves a one-step preparation of high-optical-performance, high-density fluorescent ceramics.

Description

TECHNICAL FIELD

[0001] The application relates to a one-step flow casting method for preparing high-density fluorescent ceramics and belongs to the technical field of fluorescent ceramic preparation. BACKGROUND

[0002] Solid-state lighting technology has the advantages of high luminous efficiency, fast response speed, energy saving, environmental protection, long service life and the like. With the development of time, the market has put forward the demand for high-power density excitation and high-brightness output of solid-state lighting. Laser diode (LD) lighting, as a breakthrough technology for high-power excitation, uses laser as an excitation light source and solid-state fluorescent material as a light conversion medium, which can meet the above requirements. At present, the fluorescent conversion materials suitable for high-power density excitation include fluorescent single crystals, fluorescent glasses, fluorescent films and fluorescent ceramics. The preparation process of the fluorescent single crystals is complex, the cycle is long and the technical requirements are high. The thermal conductivity of the fluorescent glass is low and cannot well meet the demand for heat dissipation. Although the thermal conductivity of the fluorescent film is improved compared with that of the fluorescent glass, the thermal conductivity is still limited. The fluorescent ceramic (represented by Y3Al5O 12 :Ce / YAG / garnet) is one of the most concerned luminescent materials in the future as a fluorescent conversion material with high thermal conductivity and stable optical performance.

[0003] There are various methods for obtaining fluorescent ceramics, and each method has its own unique technical features that are different from other technical means. Generally speaking, the first core step of obtaining fluorescent ceramics is forming. Because only the raw materials for preparing fluorescent ceramics can be "shaped" into a certain shape through a certain means, sintering can be carried out. In addition, the density of the final product of the fluorescent ceramic is also closely related to the forming process. The second core step is sintering. The sintering process almost determines the luminescent performance of the final product of the fluorescent ceramic. During sintering, the pore density (pore rate) in the fluorescent ceramic should be as low as possible. Because the existence of pores will lead to an increase in the scattering of light by the fluorescent ceramic and a decrease in the luminous intensity; at the same time, the pores will reduce the density of the fluorescent ceramic to a certain extent, so how to reduce the pore rate of the fluorescent ceramic has always been the focus of the preparation technology of the fluorescent ceramic. Usually, the fluorescent ceramic is subjected to annealing treatment (secondary sintering) after being sintered once. This is because, as believed in Non-Patent Document 1 (Hu Pan, QI Yao, Liu Yongfu, Sun Peng, Luo Zhaohua, Liu Zehua, Jiang Jun, Preparation of YAG:Ce fluorescent ceramic and its application in laser lighting, Light Source and Illumination, 2021, (S1): 70-73): after annealing (secondary sintering, usually in a vacuum state to reduce the pore rate of the ceramic), the oxygen vacancies (caused by the oxidation of the raw materials in the fluorescent ceramic during the first sintering process) are eliminated, the color center effect is weakened, and the performance of the fluorescent ceramic is improved. Without annealing, the oxygen vacancies cannot be eliminated, the color center effect is enhanced, and the performance of the fluorescent ceramic is improved.

[0004] Of course, for non-oxide fluorescent ceramics, even if the casting method is used, annealing is not necessary. This is because there are no oxides in the raw materials, so there is no need to eliminate oxygen vacancies (due to the oxides in the fluorescent ceramic raw materials during the first sintering process), and therefore no annealing is required.

[0005] For manufacturing oxide fluorescent ceramics, tape casting is a suitable continuous production process. However, (secondary) annealing is also essential. Without annealing, oxygen vacancies cannot be eliminated, color centers become more prominent, and the performance of the fluorescent ceramic is difficult to improve. Furthermore, Ce ion-doped oxide fluorescent ceramics, limited by their outer electron structure, often lack red spectral components in the white light source after mixing with blue excitation light, resulting in a low color rendering index. Therefore, better and more uniformly combining them with red phosphors in non-oxide fluorescent ceramics is one effective method to achieve a high color rendering index light source.

[0006] In summary, the above-mentioned production methods for oxide fluorescent ceramics face the following problems: too many processes, making continuous production difficult; reduced production efficiency due to secondary (annealing) sintering; and low color rendering index. Summary of the Invention

[0007] This invention provides a one-step casting method for preparing high-density fluorescent ceramics, which can effectively solve the above-mentioned problems.

[0008] This invention is implemented as follows:

[0009] A method for preparing high-density fluorescent ceramics by one-step casting includes the following steps:

[0010] S1, the powder raw material, oxygen vacancy eliminator, sintering aid, solvent, and dispersant are mixed in proportion and ball-milled for a period of time to obtain slurry A; the powder raw material is Ce-doped garnet-based fluorescent material and / or nitride fluorescent material; the oxygen vacancy eliminator includes one or more of feldspar, kaolin, and zeolite.

[0011] S2, add binder, plasticizer and homogenizer to slurry A in proportion, and continue ball milling for a period of time to obtain slurry B;

[0012] S3, filter slurry B, remove bubbles under vacuum to obtain casting slurry, and cast casting slurry to obtain casting green body;

[0013] S4 involves drying the cast green body and then performing a debinding process under a specific atmosphere and temperature. Finally, the green body is sintered at a high temperature to obtain a high-density fluorescent ceramic.

[0014] In some embodiments, the Ce-doped garnet-based fluorescent material is YAG:Ce(Y3A) l5 O 12:Ce) or LuAG:Ce(Lu3Al5O 12 The nitride fluorescent material is CaAlSiN3:Eu or La3Si6N11:Ce.

[0015] In some embodiments, the sintering aid is one or more of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, propyl orthosilicate, or silicon dioxide; and the solvent is one or more of butanone, acetone, ethanol, butanol, and methyl ethyl ketone.

[0016] In some embodiments, the dispersant is one or more of fish oil, castor oil, polyethyleneimine, Japanese oil, and trioleic acid glyceride; the binder is one or more of ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, and polyethyl methacrylate.

[0017] In some embodiments, the plasticizer is one or more of glycerol, polyethylene glycol, dibutyl phthalate, and dioctyl phthalate; the homogenizing agent is cyclohexanone.

[0018] In some embodiments, the oxygen vacancy eliminator is 0.1–0.5 wt% of the powder raw material; the sintering aid is 0.1–15 wt% of the powder raw material; the dispersant is 1–15 wt% of the powder raw material; the solvent is 30–90 wt% of the powder raw material; the binder is 1–50 wt% of the powder raw material; the plasticizer is 1–20 wt% of the powder raw material; and the homogenizer is 0.01–10 wt% of the powder raw material.

[0019] In some embodiments, the casting slurry is in 4s -1 The viscosity under shear force is 2000–40000 mPa·s.

[0020] In some embodiments, the drying temperature is 20–40°C, the humidity is 20–90%, and the time is 5–36 hours.

[0021] In some embodiments, the sintering conditions are 1.0 × 10⁻⁶. -2 ~9.0×10 -5 The sample is kept at a vacuum of 1500 MPa or a nitrogen atmosphere of 0.1-0.9 MPa for 3-35 hours, with a holding temperature of 1500-1800℃ and a heating gradient of 5-20℃ / min.

[0022] A high-density fluorescent ceramic prepared by the above method.

[0023] The beneficial effects of this invention are:

[0024] Based on the actual conditions of the raw materials, this invention selects a suitable casting process and optimizes the sintering process of fluorescent ceramics. While realizing the preparation of large-area, high-performance fluorescent ceramics, it combines oxygen vacancy eliminators and uses a one-time sintering technology to significantly reduce the experimental cycle and the energy consumption caused by secondary annealing. This further promotes the development of fluorescent ceramic preparation technology and lays the foundation for the popularization of high-power lighting devices.

[0025] The casting slurry system of the present invention is a low-toxicity organic system. The system has low toxicity and further reduces the impact on the environment while meeting process requirements.

[0026] The powder raw material selected in this invention is a phosphor with high optical performance and stability, which has the basis for commercial mass production. This lays the foundation for the further preparation of high-performance fluorescent ceramics. At the same time, it reduces the instability, non-uniformity, and variability of fluorescent ceramics made by molding and sintering original oxides, further ensuring the performance reliability of the finished product and reducing costs.

[0027] Based on the structural characteristics of oxide fluorescent ceramics and non-oxide fluorescent ceramics, this invention combines oxygen vacancy eliminators to achieve effective bonding of phosphors from different matrixes. The introduced oxygen vacancy eliminators not only significantly reduce the experimental cycle and the energy consumption caused by secondary annealing, but also effectively inhibit the chemical reaction between oxide fluorescent ceramics and non-oxide fluorescent ceramics, suppressing the transfer and diffusion of oxygen from oxide fluorescent ceramics to non-oxide fluorescent ceramics, thereby improving the color rendering index. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the preparation process of the fluorescent material provided in the embodiments of this application.

[0030] Figure 2 The TG and DTG diagrams of the cast green blank provided in the embodiments of this application are shown.

[0031] Figure 3 A physical image of the fluorescent ceramic provided in the embodiments of this application.

[0032] Figure 4 A cross-sectional microstructure diagram of the fluorescent ceramic provided in the embodiments of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention 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 the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This invention provides a method for preparing high-density fluorescent ceramics using a one-step casting method, comprising the following steps:

[0035] S1, the powder raw material, oxygen vacancy eliminator, sintering aid, solvent, and dispersant are mixed in proportion and ball-milled for a period of time to obtain slurry A; the powder raw material is Ce-doped garnet-based fluorescent material and / or nitride fluorescent material; the oxygen vacancy eliminator includes one or more of feldspar (K2O·Al2O3·6SiO2), kaolin (Al2O3·2SiO2·22H2O), and zeolite (Na2O·Al2O3·3SiO2·22H2O);

[0036] S2, add binder, plasticizer and homogenizer to slurry A in proportion, and continue ball milling for a period of time to obtain slurry B;

[0037] S3, filter slurry B, remove bubbles under vacuum to obtain casting slurry, and cast casting slurry to obtain casting green body;

[0038] S4 involves drying the cast green body and then performing a debinding process under a specific atmosphere and temperature. Finally, the green body is sintered at a high temperature to obtain a high-density fluorescent ceramic.

[0039] The casting slurry in this embodiment is a composite system of polymer and inorganic powder. The powder raw materials in the slurry are the main functional materials and are the main components of the final dense fluorescent ceramic. Their properties directly affect the performance of the final product. Among them, the sintering aid decomposes effectively during the debinding process, and its decomposition products, as additives in the high-temperature ceramic sintering process, further promote the formation of the liquid phase, effectively improve the sintering performance of the ceramic, and promote the densification of the fluorescent ceramic. The solvent, as the main dispersion system of the slurry, needs to have the ability to dissolve other organic substances and ensure that the organic substances are uniformly dispersed in the system. The dispersant, as a macromolecular organic substance, effectively disperses and separates the powder particles through steric hindrance or electrostatic hindrance, reduces agglomeration, enhances the flowability between particles, and promotes particle rearrangement and stacking. The binder effectively connects the dispersed powder particles, giving the cast green body a certain strength and workability. The plasticizer interacts with the binder in the system, further reducing the glass softening point of the binder, giving it good flexibility at room temperature. The homogenizer can improve the mutual solubility between the slurry components.

[0040] In existing technologies, the preparation of fluorescent ceramics using oxides as raw materials requires physicochemical changes, specifically endothermic and exothermic in-situ reactions. The system must first be heated to a suitable temperature to initiate the reaction and propel it forward, effectively doping the luminescent centers. However, the generation of oxygen vacancies is not self-eliminating and necessitates secondary annealing. In contrast, this invention uses phosphors as the raw material for ceramic preparation, reducing the inhomogeneity of luminescent center doping during crystal phase synthesis. The overall crystal phase composition of the ceramic is stable and uniform, requiring only high temperature and a liquid phase to promote mass transfer between raw material particles, leading to densification and resulting in ceramics with high luminous efficiency. The oxygen vacancy eliminator added in this application increases the oxygen concentration in the liquid phase during high-temperature sintering, effectively reducing oxygen vacancy generation and improving the external quantum efficiency of the ceramic without the need for a secondary annealing process. Feldspar, kaolin, and zeolite, used as oxygen vacancy eliminators, have the chemical formula xAl₂O₃·ySiO₂ (where x and y are different stoichiometric ratios). However, if alumina and silica are added separately as a mixture, the mixture is merely physically mixed and cannot synergistically eliminate oxygen vacancies during high-temperature sintering. This invention avoids the energy consumption associated with secondary annealing processes while achieving high quantum efficiency and a dense ceramic structure. The embodiments of this invention overcome the technical difficulty of traditional methods where ceramics prepared from oxide raw materials require a secondary annealing process to improve their external quantum efficiency.

[0041] In some embodiments, the Ce-doped garnet-based fluorescent material is YAG:Ce(Y3Al5O) 12 :Ce) or LuAG:Ce(Lu3Al5O 12 The nitride fluorescent material is CaAlSiN3:Eu or La3Si6N.11 :Ce.

[0042] In some embodiments, the sintering aid is one or more of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, propyl orthosilicate, or silicon dioxide. In one embodiment, the sintering aid is ethyl orthosilicate, which has a suitable decomposition rate during the binder removal process and can effectively decompose into silicon oxide compounds.

[0043] In some embodiments, the solvent is one or more of butanone, acetone, ethanol, butanol, and methyl ethyl ketone.

[0044] In some embodiments, the dispersant is one or more of fish oil, castor oil, polyethyleneimine, Japanese oil, and trioleic acid glyceride.

[0045] In some embodiments, the binder is one or more of ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, and polyethyl methacrylate. In one embodiment, the binder is polyvinyl butyral, which has a suitable molecular weight and can provide good bonding between powders.

[0046] In some embodiments, the plasticizer is one or more of glycerol, polyethylene glycol, dibutyl phthalate, and dioctyl phthalate; in one embodiment, the plasticizer is dibutyl phthalate, which can effectively increase the flexibility of the cast green body.

[0047] In one embodiment, the homogenizing agent is cyclohexanone, which effectively promotes the dissolution of various organic substances.

[0048] In some embodiments, the oxygen vacancy eliminator is 0.1–0.5 wt% of the powder raw material; the sintering aid is 0.1–15 wt% of the powder raw material; the dispersant is 1–15 wt% of the powder raw material; the solvent is 30–90 wt% of the powder raw material; the binder is 1–50 wt% of the powder raw material; the plasticizer is 1–20 wt% of the powder raw material; and the homogenizer is 0.01–10 wt% of the powder raw material. Within this range, structural collapse after the cast green body is removed can be avoided.

[0049] In some embodiments, in step S1, the ball milling time is 4–24 hours, and the ball milling speed is 100–400 rpm. The purpose of this ball milling is to ensure that the dispersant is effectively dissolved in the solvent and adsorbed onto the surface of the powder particles through intermolecular forces, achieving steric hindrance and electrostatic hindrance, thereby effectively dispersing the powder raw material particles and reducing particle agglomeration. In some embodiments, the ball milling time is 8–12 hours, and the ball milling speed is 250–350 rpm, which can achieve a good dispersion effect in a short time.

[0050] In some embodiments, in step S2, the ball milling time is 4–48 hours, and the ball milling speed is 100–400 rpm. The purpose of this ball milling is to effectively dissolve the binder and plasticizer in the solvent system. Since there are many types of organic matter in the system, a homogenizing agent is needed to further promote the solubility of various organic substances in the solvent and increase the slurry viscosity to meet the requirements of casting molding and the strength of the cast green body. In some embodiments, the ball milling time is 10–15 hours, and the ball milling speed is 300–400 rpm, which can achieve a good homogenization effect in a short time.

[0051] In some embodiments, the casting slurry is in 4s -1 The viscosity under shear force is 2000–40000 mPa·s. Too low a viscosity will affect the stability of the casting slurry's height as it flows through the doctor blade, while too high a viscosity will make it difficult for the slurry to pass through the doctor blade and form. In one embodiment, the viscosity of the casting slurry is 7550 mPa·s.

[0052] In some embodiments, the casting process involves uniformly pouring the casting slurry into a pool, and adjusting the moving speed of the substrate at a certain scraper height to perform casting. The scraper height is between 0.1 and 2.0 mm, and the substrate moving speed is between 0.05 and 3.0 m / min. -1 The purpose of scraper forming is to achieve large, thin, and uniform cast green bodies. In some embodiments, the scraper height is 0.3–1.2 mm, and the substrate moving speed is 0.20–1.00 m / min. -1 This ensures that the cast slurry has good uniformity after molding.

[0053] In some embodiments, the vacuum degassing is performed under a vacuum of 0.06 to (-0.1) MPa, with stirring for 10 to 90 minutes. The purpose of vacuum degassing is to further reduce the air introduced into the slurry by ball milling and to reduce defects in the green body during the casting process. In some embodiments, the vacuum degassing is performed under a vacuum of 0.08 to (-0.1) MPa, with stirring for 20 to 40 minutes, to efficiently remove residual air bubbles from the cast slurry.

[0054] In some embodiments, the drying temperature is 20–40°C, the humidity is 20–90%, and the drying time is 5–36 hours. The purpose of drying is to evaporate the solvent and obtain a cast green body that can be processed and transferred after drying. In some embodiments, the drying temperature is 30–35°C, the humidity is 50–70%, and the drying time is 12–24 hours to obtain a dry, smooth, and crack-free cast green body.

[0055] In some embodiments, the atmosphere for the debinding process is air, oxygen, nitrogen, or argon; the temperature regime is 100–200°C for 20–300 min, 300–500°C for 20–600 min, and 500–650°C for 20–600 min, with a heating rate of 0.5–3°C / min. The purpose of the debinding process for the cast green body is to effectively promote the decomposition of organic matter, remove organic matter, further promote particle accumulation, leaving only the accumulated raw material particles, which is beneficial for ceramic sintering. In some embodiments, the ambient atmosphere is oxygen, the temperature is 150–180°C for 150–300 min, the temperature is 400–450°C for 300–400 min, and the temperature is 580–620°C for 350–450 min, with a heating rate of 1–2°C / min, so that the organic matter can be more fully decomposed into water and carbon dioxide after cracking and vaporizing at high temperature.

[0056] In some embodiments, the sintering conditions are 1.0 × 10⁻⁶. -2 ~9.0×10 -5 The ceramic is held at a vacuum of 1500-1800℃ for 3-35 hours under a nitrogen atmosphere of 0.1-0.9 MPa, with a heating gradient of 5-20℃ / min. The purpose of high-temperature sintering is to promote interparticle material transfer and effectively densify the ceramic through prolonged high-temperature holding. In some embodiments, the high-temperature sintering conditions are 5.5 × 10⁻⁶ MPa. -4 ~9.0×10 -5 Under vacuum conditions of Pa, the ceramic is kept at a temperature of 1600-1750℃ for 10-20 hours, with a heating rate of 7-10℃ / min. Appropriate vacuum conditions are beneficial to the densification of ceramics. Under a certain heating rate, the longer the holding temperature and holding time, the higher the degree of ceramic densification. However, excessively high holding time and holding temperature will increase energy consumption.

[0057] This invention also provides a high-density fluorescent ceramic prepared by the above method.

[0058] The casting process in this application will be further described below with several embodiments.

[0059] Example 1-1

[0060] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A1-1 was prepared.

[0061] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A1-1 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B1-1.

[0062] Examples 1-2

[0063] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of silica, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A1-2 was prepared.

[0064] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A1-2 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B1-2.

[0065] Examples 1-3

[0066] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of acetone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A1-3 was prepared.

[0067] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A1-3 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B1-3.

[0068] Examples 1-4

[0069] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of castor oil were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A1-4 was prepared.

[0070] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A1-4 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B1-4.

[0071] Examples 1-5

[0072] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A1-5 was prepared.

[0073] (2) Add 12g of polyethyl methacrylate, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A1-5 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B1-5.

[0074] Examples 1-6

[0075] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A1-6 was prepared.

[0076] (2) Add 12g of polyvinyl butyral, 6g of polyethylene glycol, and 0.5g of cyclohexanone to slurry A1-6 in a certain proportion, and continue ball milling at 380 rpm for 12 hours to prepare slurry B1-6; Examples 1-7

[0077] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 350 rpm for 12 hours, a mixed slurry A1-7 was prepared.

[0078] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A1-7 in a certain proportion, and continue to ball mill at 400 rpm for 15 h to prepare slurry B1-7.

[0079] Examples 1-8

[0080] (1) 50g of YAG:Ce phosphor, 50g of CaAlSiN3:Eu phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone, and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 12 hours, mixed slurry A1-8 was prepared.

[0081] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A1-8 in a certain proportion, and continue to ball mill at 380 rpm for 15h to prepare slurry B1-8.

[0082] Table 1

[0083]

[0084] Table 1 shows the viscosities of Examples 1-1 to 1-8. The different components of the casting formulations were obtained at a shear force of 4s. -1 The viscosities of the different materials vary slightly, but all meet the viscosity requirements for casting.

[0085] The sintering process in the technical solution of this application will be further described below with several embodiments.

[0086] Comparative Example 2-1 (Anaerobic Vacancy Eliminator)

[0087] (1) 100g of YAG:Ce phosphor, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-1 was prepared.

[0088] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-1 in a certain proportion, and continue to ball mill at 320 rpm for 12h to prepare slurry B2-1.

[0089] (3) Filter slurry B2-1, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0090] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0091] Comparative Example 2-2 (using alumina and silica instead of oxygen vacancy scavengers)

[0092] (1) 100g of YAG:Ce phosphor, 0.1g of alumina, 0.1g of silica, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-2 was prepared.

[0093] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-2 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-2.

[0094] (3) Filter slurry B2-2, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0095] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0096] Comparative Examples 2-3 (Oxygen-free vacancy eliminator + secondary annealing)

[0097] (1) 100g of YAG:Ce phosphor, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-3 was prepared.

[0098] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-3 in a certain proportion, and continue to ball mill at 320 rpm for 12 h to prepare slurry B2-3.

[0099] (3) Filter slurry B2-3, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0100] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 YAG:Ce fluorescent ceramics were obtained by holding at 1600℃ for 10 hours under vacuum, and then annealed at 1450℃ for 10 hours to obtain secondary sintered YAG:Ce fluorescent ceramics.

[0101] Comparative Examples 2-4 (Oxygen-free vacancy eliminator + non-oxide phosphor)

[0102] (1) 50g of YAG:Ce phosphor, 50g of CaAlSiN3:Eu phosphor, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone, and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-2 was prepared.

[0103] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-2 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2.

[0104] (3) Filter slurry B1, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0105] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Under vacuum conditions, it was kept at 1600℃ for 10 hours.

[0106] Example 2-1

[0107] (1) 100g of YAG:Ce phosphor, 0.3g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-1 was prepared.

[0108] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-1 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-2.

[0109] (3) Filter slurry B2-2, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0110] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0111] Example 2-2

[0112] (1) 100g of YAG:Ce phosphor, 0.5g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-2 was prepared.

[0113] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-2 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-2.

[0114] (3) Filter slurry B2-2, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0115] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0116] Example 2-3

[0117] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-3 was prepared.

[0118] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-3 in a certain proportion, and continue to ball mill at 320 rpm for 12 h to prepare slurry B2-3.

[0119] (3) Filter slurry B2-3, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0120] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1700℃ for 10 hours under vacuum conditions.

[0121] Examples 2-4

[0122] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-4 was prepared.

[0123] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-4 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-4.

[0124] (3) Filter slurry B2-4, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0125] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1750℃ for 10 hours under a vacuum environment of Pa.

[0126] Examples 2-5

[0127] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-5 was prepared.

[0128] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-5 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-5.

[0129] (3) Filter slurry B2-5, and after vacuum degassing at 0.08 MPa for 30 min, prepare casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0130] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 15 hours under vacuum conditions.

[0131] Examples 2-6

[0132] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-6 was prepared.

[0133] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-6 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-6.

[0134] (3) Filter slurry B2-6, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0135] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 20 hours under vacuum conditions.

[0136] Examples 2-7

[0137] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-7 was prepared.

[0138] (2) Add 40g of polyvinyl butyral, 18g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-7 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-7.

[0139] (3) The slurry B2-7 was filtered and vacuum defoamed at 0.08 MPa for 30 min to prepare the casting slurry. The slurry was then poured into the material tank at a uniform speed, with the scraper height at 0.9 mm and the substrate moving speed at 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0140] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0141] Examples 2-8

[0142] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-8 was prepared.

[0143] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-8 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-8.

[0144] (3) Filter slurry B2-8, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0145] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0146] Examples 2-9

[0147] (1) 100g of YAG:Ce phosphor, 0.2g of feldspar, 14g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, mixed slurry A2-9 was prepared.

[0148] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-9 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-9.

[0149] (3) Filter slurry B2-9, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0150] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0151] Example 2-10

[0152] (1) 55g of YAG:Ce phosphor, 45g of CaAlSiN3:Eu phosphor, 0.2g of feldspar, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 h, mixed slurry A2-9 was prepared.

[0153] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-9 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-9.

[0154] (3) Filter slurry B2-9, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0155] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0156] Example 2-11

[0157] (1) 100g of YAG:Ce phosphor, 0.2g of zeolite, 0.5g of tetraethyl orthosilicate, 23g of ethanol, 38g of butanone and 2g of polyethyleneimine were mixed in sequence and added to a ball mill jar. After ball milling at 260 rpm for 10 hours, a mixed slurry A2-9 was prepared.

[0158] (2) Add 12g of polyvinyl butyral, 6g of dibutyl phthalate and 0.5g of cyclohexanone to slurry A2-9 in a certain proportion, and continue to ball mill at 320 rpm for 12 hours to prepare slurry B2-9.

[0159] (3) Filter slurry B2-9, and after vacuum degassing at 0.08 MPa for 30 min, prepare a casting slurry. Pour the slurry into the material tank at a uniform speed, with a scraper height of 0.9 mm and a substrate moving speed of 0.20 m·min. -1 Under certain conditions, the casting process was carried out, and the casting green body was obtained after drying at 35℃ and 58% humidity for 15 hours.

[0160] (4) Cut the cast iron blank obtained in step (3) into... The blanks were prepared and placed in an air atmosphere for debinding. The entire heating rate was 1℃ / min, with a holding time of 35min at 150℃, 125min at 480℃, and 352min at 550℃. The debinded blanks were then placed in a 4×10... -3 Dense YAG:Ce fluorescent ceramics were obtained by holding the ceramic at 1600℃ for 10 hours under vacuum conditions.

[0161] Table 2

[0162]

[0163]

[0164] Table 2 shows a comparison of the external quantum efficiency (OQE) of the powder raw materials and fluorescent ceramics in Comparative Examples 2-1 to 2-4 and Examples 2-1 to 2-11. It can be seen that although the quantum efficiency of the fluorescent ceramics decreased, the prepared fluorescent ceramics maintained a high OQE. Specifically, Comparative Examples 2-1 and Example 2-1 show that the oxygen vacancy eliminator effectively reduced the oxygen vacancies generated during sintering, improving the OQE of the prepared fluorescent ceramics. Comparative Examples 2-1, 2-3, and Example 2-1 show that the absence of an oxygen vacancy eliminator and the presence of a second annealing significantly reduced the OQE of the prepared fluorescent ceramics and increased energy consumption. Comparative Example 2-1 shows that adding a mixture of alumina and silica separately, while physically mixing them, cannot achieve a synergistic effect of eliminating oxygen vacancies during high-temperature sintering. As shown in Examples 2-1 and 2-2, with the increase of feldspar content, the oxygen vacancies decrease during the sintering process of fluorescent ceramics, and their external quantum efficiency gradually increases. As shown in Examples 2-3 and 2-4, with the increase of sintering temperature, the density of fluorescent ceramics gradually increases, and their external quantum efficiency gradually increases. As shown in Examples 2-5 and 2-6, at the same sintering temperature, with the extension of holding time, the density of fluorescent ceramics gradually increases, and their external quantum efficiency gradually increases. As shown in Example 2-7, binders and plasticizers are the main organic components after the cast green sheet is dried. With the increase of their content, more organic matter fills and separates the particles in the cast green sheet, reducing its bulk density, and the external quantum efficiency of the prepared fluorescent ceramic decreases slightly. As shown in Examples 2-8 and 2-9, the external quantum efficiency of the prepared fluorescent ceramics first increases and then decreases with the increase of sintering aids. This is because, to a certain extent, increasing the content of sintering aids is beneficial to promoting liquid-phase mass transfer during sintering and to densifying the ceramic. However, with further increases in sintering aids, the amount of liquid phase increases, leading to a certain degree of corrosion of the fluorescent particles, thus decreasing the external quantum efficiency of the prepared fluorescent ceramics. As shown in Comparative Examples 2-4 and 2-10, two materials, mixed together and cast in a tape casting process, ultimately produce a multiphase fluorescent ceramic; therefore, this value represents the final external quantum efficiency of the ceramic. The addition of an oxygen vacancy scavenger effectively inhibits the mutual influence between the two materials during the high-temperature reaction, reducing the diffusion of oxygen from oxide phosphors to non-oxide phosphors. As shown in Comparative Example 2-4, without an oxygen vacancy scavenger, the non-oxide phosphors react with the oxide phosphors, causing a decrease in the quantum efficiency of the ceramic. As shown in Example 2-11, zeolite also acts as an oxygen vacancy scavenger, resulting in fluorescent ceramics with better quantum efficiency.

[0165] The color temperature and color rendering index (CRI) were tested using a 450nm blue laser excitation. Example 2-1 had a color temperature of 7678K and a CRI of 69; Comparative Examples 2-4 had a color temperature of 5341K and a CRI of 73; and Example 2-10 had a color temperature of 3423K and a CRI of 79, resulting in a warm-colored lighting source with a lower color temperature. A higher CRI indicates greater value of the non-oxide phosphor as part of the ceramic, a higher proportion of red components in the spectrum, and a greater degree of color reproduction of the illuminated object after the ceramic is excited and emits light. Oxide phosphor YAG:Ce emits yellow light when excited; however, it does not emit red light when excited without non-oxide phosphor as a raw material. Therefore, the CRI of Example 2-1 is not high. Both Comparative Examples 2-4 and Examples 2-10 used non-oxide phosphors as one of the raw materials to prepare fluorescent ceramics. However, Comparative Examples 2-4 lacked oxygen vacancy eliminators, which caused the oxide phosphors to react with the non-oxide phosphors, resulting in the loss of luminescent centers. Consequently, less light was generated when excited, and the color rendering index was lower than that of Examples 2-10.

[0166] The ceramics prepared in Example 2-2 are as follows Figure 3 As shown, its bulk density, measured by Archimedes' displacement method, is 4.48 g / cm³. 3 Its microstructure is as follows Figure 4 As shown, the grains are closely packed together with no obvious pores.

[0167] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing high-density fluorescent ceramics by one-step casting, characterized in that, Includes the following steps: S1, the powder raw material, oxygen vacancy eliminator, sintering aid, solvent, and dispersant are mixed in proportion and ball-milled for a period of time to obtain slurry A; the powder raw material is Ce-doped garnet-based fluorescent material and / or nitride fluorescent material; the oxygen vacancy eliminator is one or more of feldspar, kaolin, and zeolite. S2, add binder, plasticizer and homogenizer to slurry A in proportion, and continue ball milling for a period of time to obtain slurry B; S3, filter slurry B, remove bubbles under vacuum to obtain casting slurry, and cast casting slurry to obtain casting green body; S4 involves drying the cast green body and then performing a debinding process under a specific atmosphere and temperature. Finally, the green body is sintered at a high temperature to obtain a high-density fluorescent ceramic.

2. The method according to claim 1, characterized in that, The Ce-doped garnet-based fluorescent material is Y3Al5O 12 Ce or Lu3Al5O 12 Ce; the nitride fluorescent material is CaAlSiN3:Eu or La3Si6N11:Ce.

3. The method according to claim 1, characterized in that, The sintering aid is one or more of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, propyl orthosilicate, or silicon dioxide; the solvent is one or more of butanone, acetone, ethanol, butanol, and methyl ethyl ketone.

4. The method according to claim 1, characterized in that, The dispersant is one or more of fish oil, castor oil, polyethyleneimine, and trioleic acid glyceride; the binder is one or more of ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, and polyethyl methacrylate.

5. The method according to claim 1, characterized in that, The plasticizer is one or more of glycerin, polyethylene glycol, dibutyl phthalate, and dioctyl phthalate; the homogenizing agent is cyclohexanone.

6. The method according to claim 1, characterized in that, The oxygen vacancy eliminator is present in an amount of 0.1-0.5 wt% of the powder raw material; the sintering aid is present in an amount of 0.1-15 wt% of the powder raw material; the dispersant is present in an amount of 1-15 wt% of the powder raw material; the solvent is present in an amount of 30-90 wt% of the powder raw material; the binder is present in an amount of 1-50 wt% of the powder raw material; the plasticizer is present in an amount of 1-20 wt% of the powder raw material; and the homogenizer is present in an amount of 0.01-10 wt% of the powder raw material.

7. The method according to claim 1, characterized in that, The cast slurry was in 4 s -1 The viscosity under shear force is 2000~40000 mPa·s.

8. The method according to claim 1, characterized in that, The drying temperature is 20~40 ℃, the humidity is 20~90%, and the time is 5~36 h.

9. The method according to claim 1, characterized in that, The sintering conditions are 1.0 × 10⁻⁶. -2 ~9.0×10 -5 The sample is kept at a vacuum of 1500-1800 ℃ for 3-35 h under a nitrogen atmosphere of 0.1-0.9 MPa, with a heating gradient of 5-20 ℃ / min.

10. A high-density fluorescent ceramic prepared by the method of any one of claims 1 to 9.

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