Preparation method of high-transmittance Ce:YAG transparent ceramic

Abstract

The application discloses a preparation method of high-transmittance Ce:YAG transparent ceramic, and the method comprises the following steps: taking tetraethyl orthosilicate and Al2O3 as raw materials, adding them into an ethanol solution, stirring uniformly at room temperature, heating to obtain a core-shell structure precursor, and washing and drying to obtain a core-shell structure oxide Al2O3@Si; taking Al2O3, Y2O3 and CeO2 as raw material powders, taking each raw material according to the stoichiometric ratio of corresponding elements in a chemical formula (Y 1‑x Ce x )3Al5O 12 Sintering aids, anhydrous ethanol, a dispersant, the core-shell structure oxide and the raw material powders are put into a ball mill tank to obtain a mixed slurry; the mixed slurry is sequentially subjected to drying, sieving, calcining, dry pressing, plastic packaging, sintering, annealing and polishing to obtain the transparent ceramic. The method can fill the grain boundary pores and accelerate the particle rearrangement, improve the sintering activity of the ceramic powder, thereby improving the density of the ceramic, and further improving the transmittance of the ceramic.

Description

TECHNICAL FIELD

[0001] The application relates to the field of advanced ceramic preparation, and particularly relates to a preparation method of high-transmittance Ce:YAG transparent ceramic. BACKGROUND

[0002] Transparent ceramic is a new type of optical functional material which has attracted wide attention in recent years. The transparent ceramic has rapidly developed due to its high thermal conductivity, good mechanical properties, high doping concentration of luminescent ions, uniform doping and flexible structure design. The Ce:YAG ceramic has been widely concerned due to its good light transmittance, high quantum efficiency, wide emission spectrum band and high thermal conductivity of 14 Wm-1K-1. -1 K -1 The Ce ion has a 4f5d electronic configuration and is an activated ion with high fluorescence efficiency among rare earth ions. Therefore, the scheme of using the YAG transparent ceramic doped with Ce ions to replace the Ce:YAG fluorescent powder can avoid the use of encapsulating materials such as epoxy resin, and the transparent ceramic has good heat dissipation, high thermal stability and long service life. Meanwhile, the transparent ceramic can realize high doping concentration and high chemical uniformity, so as to improve the light emission efficiency, optical uniformity and stability of the white light LED device. Improving the transmittance and light output rate of the transparent ceramic is still a key technical problem in research.

[0003] The residual pores, grain boundary impurities and doping segregation in the transparent ceramic are main factors affecting the optical quality. In the process of preparing the Ce:YAG transparent ceramic by the solid-phase reaction sintering method, directly drying the ball-milled slurry will cause serious agglomeration and irregular shape of the nanometer micrometer powder. The dried powder has poor flowability and large friction between particles, which is not conducive to the subsequent forming process. This phenomenon is more serious in the preparation of large size, complex shape and composite structure, and becomes the main source of the second phase and residual pores in the ceramic sintered body. Therefore, in order to further improve the optical quality of the Ce:YAG transparent ceramic, a sintering additive, that is, a sintering aid, is usually introduced. The purpose of the sintering aid is to further promote the densification of the ceramic, reduce the number of scattering sources, and prevent the rapid migration of the grain boundary and the formation of intragranular pores during the sintering process. Tetraethyl orthosilicate (TEOS) is the most common sintering aid for preparing the Ce:YAG transparent ceramic. TEOS can reduce the sintering temperature and improve the diffusion rate, which is beneficial to the densification of the transparent ceramic, but promotes the grain growth. Therefore, Mg is usually added as another sintering aid to inhibit the grain growth, but more impurities are introduced at the same time. Al2O3 is introduced as a second phase to improve the transmittance due to its hexagonal structure and matching refractive index with the transparent ceramic. However, the uniformity cannot be solved due to the low content of Al2O3. SUMMARY

[0004] The application aims to provide a preparation method of high-transmittance Ce:YAG transparent ceramic.

[0005] The technical scheme adopted by the application is as follows: the application provides a preparation method of high-transmittance Ce:YAG transparent ceramic, comprising the following steps:

[0006] (1) taking tetraethyl orthosilicate and commercially available Al2O3 with a purity greater than 99.9% as raw materials according to a mass ratio of (0.5-2):1, adding the raw material powder into an ethanol solution with a volume concentration of 30-50%, stirring uniformly at room temperature, and then heating to obtain a core-shell structure precursor; washing the core-shell structure precursor with deionized water and anhydrous ethanol for 3-4 times in sequence, and drying to obtain a core-shell structure oxide Al2O3@Si;

[0007] (2) taking commercially available Al2O3, Y2O3 and CeO2 with a purity greater than 99.9% as raw material powder, and taking each raw material according to the stoichiometric ratio of the corresponding element in the chemical formula (Y 1-x Ce x )3Al5O 12 , wherein x is the molar percentage of Ce 3+ doping Y 3+ , 0.01≤x≤0.5; putting a sintering aid, anhydrous ethanol, a dispersant and the core-shell structure oxide into a ball mill tank together with the raw material powder to obtain a mixed slurry;

[0008] (3) placing the mixed slurry after the ball milling in step (2) in a drying box for drying, sieving the mixed powder after drying, and then calcining in an air environment;

[0009] (4) putting the mixed powder after the calcining in step (3) into a mold for dry pressing forming, taking the green body out of the mold, performing plastic packaging on a vacuum packaging machine, and then performing cold isostatic pressing to obtain a ceramic green body;

[0010] (5) putting the ceramic green body obtained in step (4) into an atmosphere sintering furnace for sintering in a nitrogen atmosphere containing 5%-10% hydrogen;

[0011] (6) placing the ceramic material after the sintering in step (5) in a muffle furnace for annealing, reducing the furnace to room temperature, and then obtaining the high-transmittance Ce:YAG transparent ceramic after polishing.

[0012] Preferably, in step (1), the mass ratio of the ethanol solution to the raw material is (2-4):1.

[0013] Preferably, in step (1), the heating parameters are: heating temperature 300-450℃, heating time 12-15h; the drying parameters are: drying temperature 55-65℃, drying time 12-16h; the stirring parameters are: stirring rate 300r / min, stirring time 6-8h.

[0014] Preferably, in step (2), the sintering aid is tetraethyl orthosilicate, and its amount is 0.10-1.00wt.% of the total mass of Al2O3, Y2O3 and CeO2 powders; the dispersant is DS005, and its amount is 0.10-1.20wt.% of the total mass of Al2O3, Y2O3 and CeO2 powders.

[0015] Preferably, in step (2), the mass ratio of anhydrous ethanol to the total mass of Al2O3, Y2O3 and CeO2 powders is (1-3):1, and the mass ratio of the core-shell structure oxide to the total mass of Al2O3, Y2O3 and CeO2 powders is (0.15-0.2):1.

[0016] Preferably, in step (2), the ball milling parameters are: ball milling speed 50-100r / min, ball milling time 10-14h.

[0017] Preferably, in step (3), the drying temperature is 60-70℃, the drying time is 20-50h, the calcination temperature is 700-800℃, and the calcination time is 10-20h.

[0018] Preferably, in step (4), the cold isostatic pressing parameters are: pressure 50-70MPa, pressure maintaining time 15-30min.

[0019] Preferably, in step (5), the sintering temperature is 1700-1800℃, and the sintering time is 20-50h.

[0020] Preferably, in step (6), the annealing temperature is 1300-1450℃, and the annealing time is 15-50h.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The present application introduces the core-shell structure oxide Al2O3@Si into the traditional Ce:YAG transparent ceramic material. Since the core-shell structure tends to gather at the ceramic grain boundary during sintering, it is beneficial to fill the grain boundary pores. The introduction of Si can accelerate particle rearrangement, improve the sintering activity of the ceramic powder, and improve the density of the ceramic, thereby improving the transmittance. The transmittance of the transparent ceramic prepared by the present application can reach 83-87%.

[0023] (2) The transparent ceramic provided by the application strictly controls the introduction of impurities, has high quality, stable process, and is very suitable for preparing transparent ceramic materials; the preparation method is simple and conducive to industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A transmittance broken line graph of the transparent ceramic material prepared for Comparative Example 1 and Examples 1-3, respectively. DETAILED DESCRIPTION

[0025] The application will be further described in detail below in combination with the drawings and specific examples.

[0026] Example 1

[0027] A preparation method of a high-transmittance Ce:YAG transparent ceramic, comprising the following steps:

[0028] (1) 5 g of tetraethyl orthosilicate and 10 g of commercially available Al2O3 with a purity greater than 99.9% are weighed, the Al2O3 and the tetraethyl orthosilicate are added to 30 g of ethanol with a volume concentration of 30%, and stirring is performed at a stirring speed of 300 rpm for 6 h at room temperature; the uniformly stirred solution is heated at 300℃ for 12 h to obtain a core-shell structure precursor; the core-shell structure precursor is washed with deionized water and anhydrous ethanol for 3 times, respectively, and is placed in a drying oven at 55℃ for 12 h to obtain a core-shell structure oxide Al2O3@Si;

[0029] (2) 42.4 g of commercially available Al2O3 with a purity greater than 99.9%, 53.5 g of Y2O3 and 4.3 g of CeO2 are used as raw material powders, and the raw materials are weighed according to the stoichiometric ratio of the corresponding elements in the chemical formula (Y 0.99 Ce 0.01 )3Al5O 12 ; 0.1 g of a sintering aid tetraethyl orthosilicate, 100 g of anhydrous ethanol, 0.1 g of a dispersant DS005 and 15 g of the core-shell structure oxide are placed in a ball mill tank together with the raw material powders, and ball milling is performed at a rotating speed of 50 rpm for 10 h to obtain a mixed slurry;

[0030] (3) The mixed slurry after the ball milling in step (2) is placed in a drying oven for drying at 60℃ for 20 h, the dried mixed powders are sieved, and then calcination is performed at 700℃ for 10 h in an air environment;

[0031] (4) The mixed powders after the calcination in step (3) are placed in a mold for dry pressing, the green body is taken out of the mold, plastic packaging is performed on a vacuum packaging machine, and then cold isostatic pressing is performed at a pressure of 50 MPa for 15 min;

[0032] (5) Put the ceramic green body obtained in step (4) into an atmosphere sintering furnace, sinter in a nitrogen atmosphere containing 5% hydrogen, and keep at 1700°C for 20h;

[0033] (6) Anneal the ceramic material sintered in step (5) in a muffle furnace, the annealing temperature is 1300°C, the annealing time is 15h, and the furnace is cooled to room temperature, and the polished ceramic material A1 is obtained.

[0034] The luminescent efficiency of the transparent ceramic material A1 prepared in this embodiment is 112 lm / W, and the color rendering index Ra is 60, as shown in Figure 1 The transmittance of the transparent ceramic material A1 prepared is 81.3%.

[0035] Example 2

[0036] A method for preparing a high-transmittance Ce:YAG transparent ceramic, comprising the following steps:

[0037] (1) Take 10g of tetraethyl orthosilicate and 10g of commercially available Al2O3 with a purity of more than 99.9%, add the Al2O3 and tetraethyl orthosilicate to 60g of ethanol with a volume concentration of 35%, stir at a stirring speed of 300rpm at room temperature for 7h, and heat the uniformly stirred solution at 370°C for 13h to obtain a core-shell structure precursor; wash the core-shell structure precursor with deionized water and anhydrous ethanol for 3 times, and dry at 60°C for 14h to obtain a core-shell structure oxide Al2O3@Si;

[0038] (2) Take commercially available Al2O3 with a purity of more than 99.9%, Y2O3 and CeO2 as raw material powders, and take each raw material according to the stoichiometric ratio of the corresponding elements in the chemical formula (Y 0.88 Ce 0.12 )3Al5O 12 ; put 0.5g of sintering aid tetraethyl orthosilicate, 250g of anhydrous ethanol, 0.5g of dispersant DS005, and 20g of core-shell structure oxide into a ball mill tank together with the raw material powders, and mill at a rotating speed of 70rpm for 12h to obtain a mixed slurry;

[0039] (3) Dry the mixed slurry after ball milling in step (2) in a drying box at 65°C for 35h, sieve the dried mixed powders, and then calcine at 750°C for 15h in an air environment;

[0040] (4) Dry-press the mixed powders after calcining in step (3) into a mold, take out the green body from the mold, and perform plastic packaging on a vacuum packaging machine, and then perform cold isostatic pressing at a pressure of 60MPa for 20min;

[0041] (5) Put the ceramic green body obtained in step (4) into an atmosphere sintering furnace, and sinter the ceramic green body in a nitrogen atmosphere containing 8% hydrogen at 1750°C for 35h;

[0042] (6) Anneal the ceramic material sintered in step (5) in a muffle furnace at an annealing temperature of 1350°C for 25h, and then cool the ceramic material to room temperature. After polishing, the ceramic material A2 is obtained.

[0043] The prepared transparent ceramic material A2 has a luminous efficiency of 111 lm / W and a color rendering index Ra of 63, as shown in Figure 1 The prepared transparent ceramic material A2 has a transmittance of 82.7%.

[0044] Example 3

[0045] A method for preparing a high-transmittance Ce:YAG transparent ceramic includes the following steps:

[0046] (1) Take 20g of tetraethyl orthosilicate and 10g of commercially available Al2O3 with a purity of greater than 99.9%, and add the Al2O3 and the tetraethyl orthosilicate to 120g of ethanol with a volume concentration of 40%, and stir the mixture at a stirring speed of 300rpm for 8h at room temperature. Then, heat the stirred solution to 450°C for 15h to obtain a core-shell structure precursor. Then, wash the core-shell structure precursor with deionized water and anhydrous ethanol for 3 times, and then dry the core-shell structure precursor at 65°C for 16h to obtain a core-shell structure oxide Al2O3@Si;

[0047] (2) Take 63.6g of commercially available Al2O3 with a purity of greater than 99.9%, 80.3g of Y2O3 and 6.4g of CeO2 as raw material powders, and take each raw material according to the stoichiometric ratio of the corresponding elements in the chemical formula (Y 0.5 Ce 0.5 )3Al5O 12 Then, put 1g of a sintering aid tetraethyl orthosilicate, 450g of anhydrous ethanol, 1g of a dispersant DS005 and 30g of the core-shell structure oxide into a ball mill tank together with the raw material powders, and mill the mixture at a rotating speed of 100rpm for 14h to obtain a mixed slurry;

[0048] (3) Dry the mixed slurry obtained in step (2) in a drying box at 70°C for 50h, sieve the dried mixed powders, and then calcine the sieved mixed powders at 800°C for 20h in an air environment;

[0049] (4) Dry-press the mixed powders calcined in step (3) into a mold, take the green body out of the mold, and then perform plastic packaging on the green body in a vacuum packaging machine. Then, perform cold isostatic pressing on the green body at a pressure of 70MPa for 30min;

[0050] (5) Put the ceramic green body obtained in step (4) into an atmosphere sintering furnace, and sinter it in a nitrogen atmosphere containing 10% hydrogen at 1800°C for 50h;

[0051] (6) Put the ceramic material sintered in step (5) into a muffle furnace for annealing, the annealing temperature is 1450°C, the annealing time is 50h, and the furnace is cooled to room temperature, and the polished ceramic material A3 is obtained.

[0052] The luminescent efficiency of the transparent ceramic material A3 prepared in this example is 117lm / W, and the color rendering index Ra is 64, as shown in Figure 1 The transmittance of the transparent ceramic material A3 prepared in this example is 83.5%.

[0053] Comparative Example 1

[0054] The difference between this comparative example 1 and example 1 is that step (1) in example 1 is not implemented in this comparative example 1, that is, the core-shell structured oxide Al2O3@Si is not added in this comparative example, and other steps are consistent with example 1. The ceramic material B1 is prepared by this comparative example 1.

[0055] The luminescent efficiency of the transparent ceramic material B1 prepared in this comparative example is 110lm / W, and the color rendering index Ra is 60, as shown in Figure 1 The transmittance of the transparent ceramic material B1 prepared in this comparative example is 80.4%.

[0056] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this, any skilled person in the art can make any modification, equivalent replacement and improvement within the technical range disclosed in the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for preparing a high-transmittance Ce:YAG transparent ceramic, characterized in that, The method comprises the following steps: (1) taking tetraethyl orthosilicate and commercially available Al2O3 with a purity of greater than 99.9% as raw materials in a mass ratio of (0.5-2):1, adding the raw material powder into an ethanol solution with a volume concentration of 30-50%, stirring uniformly at room temperature, and then heating to obtain a core-shell structure precursor; washing the core-shell structure precursor with deionized water and anhydrous ethanol for 3-4 times, and drying to obtain an Al2O3@Si core-shell structure oxide; (2) commercially available Al203, Y203 and Ce02 with purity greater than 99.9% as raw material powders, according to the chemical formula (Y 1-x Ce x )3Al5O 12 x is the molar percentage of Ce 3+ doping Y 3+ , 0.01≤x≤0.5; a sintering aid, anhydrous ethanol, a dispersant, and a core-shell structure oxide are put into a ball mill tank together with the raw material powders to obtain a mixed slurry; the mass ratio of the core-shell structure oxide to the total mass of Al203, Y203 and Ce02 powders is (0.15-0.2):1; (3) placing the mixed slurry after ball milling in step (2) in a drying box for drying, sieving the dried mixed powder, and then calcining in an air environment; (4) placing the mixed powder after calcination in step (3) into a mold for dry pressing, taking out the green body from the mold, performing plastic packaging on a vacuum packaging machine, and then performing cold isostatic pressing to obtain a ceramic green body; (5) placing the ceramic green body obtained in step (4) into an atmosphere sintering furnace for sintering in a nitrogen atmosphere containing 5%-10% hydrogen; (6) annealing the ceramic material after sintering in step (5) in a muffle furnace, reducing the furnace to room temperature, and then polishing to obtain a high-transmittance Ce:YAG transparent ceramic.

2. The method of claim 1, wherein the Ce:YAG transparent ceramic has a transmittance of 70% or more at a wavelength of 550 nm. In step (1), the mass ratio of the ethanol solution to the raw materials is (2-4):

1.

3. The method of claim 1 or 2, wherein the method further comprises the step of sintering the green sheet to form a high-transmittance Ce:YAG transparent ceramic. In step (1), the heating parameters are: heating temperature 300-450 o C, heating time 12-15 h; the drying parameters are: drying temperature 55-65 o C, drying time 12-16 h; the stirring parameters are: stirring rate 300 r / min, stirring time 6-8 h.

4. The method of claim 1 or 2, wherein the transparent ceramic is Ce:YAG, and the method further comprises the steps of: sintering the green body to form a sintered body; and annealing the sintered body. In step (2), the sintering aid is tetraethyl orthosilicate, and the amount is 0.10-1.00 wt.% of the total mass of Al2O3, Y2O3 and CeO2 powders; the dispersant is DS005, and the amount is 0.10-1.20 wt.% of the total mass of Al2O3, Y2O3 and CeO2 powders.

5. The method of claim 1 or 2, wherein the transparent ceramic is Ce:YAG, and the method further comprises the steps of: sintering the green body to form a sintered body; and annealing the sintered body. In step (2), the mass ratio of the anhydrous ethanol to the total mass of Al2O3, Y2O3 and CeO2 powders is (1-3):

1.

6. The method of claim 1 or 2, wherein the transparent ceramic is Ce:YAG, and the method further comprises the steps of: sintering the green body to form a sintered body; and annealing the sintered body. In step (2), the ball milling parameters are as follows: a ball milling speed of 50-100 r / min and a ball milling time of 10-14 h.

7. The method of claim 1 or 2, wherein the transparent ceramic is Ce:YAG, and the method further comprises the steps of: sintering the green body to form a sintered body; and annealing the sintered body. In step (3), the drying temperature is 60-70 °C, the drying time is 20-50 h, the calcination temperature is 700-800 °C, and the calcination time is 10-20 h.

8. The method of claim 1 or 2, wherein the transparent ceramic is Ce:YAG, and the method further comprises the steps of: sintering the green body to form a sintered body; and annealing the sintered body. In step (4), the cold isostatic pressing parameters are as follows: a pressure of 50-70 MPa and a pressure maintaining time of 15-30 min.

9. The method of claim 1 or 2, wherein the transparent ceramic is Ce:YAG, and the method further comprises the steps of: sintering the green body to form a sintered body; and annealing the sintered body. In step (5), the sintering temperature is 1700-1800 °C, and the sintering time is 20-50 h.

10. The method of claim 1 or 2, wherein the transparent ceramic is Ce:YAG, and the method further comprises the steps of: sintering the green body to form a sintered body; and annealing the sintered body. In step (6), the annealing temperature is 1300-1450 °C, and the annealing time is 15-50 h.

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