A method for preparing rare earth-doped garnet transparent ceramics by tape casting

Abstract

The present invention belongs to the technical field of functional ceramics, and specifically discloses a method for preparing rare earth-doped garnet transparent ceramics by tape casting, which includes the following steps: taking rare earth-doped garnet powder, carrageenan gum and a dispersant, adding water for wet ball milling to obtain a ceramic slurry; after defoaming the ceramic slurry, tape casting is used to obtain a green body; the green body is degummed and then sintered in a vacuum environment. The present invention uses rare earth-doped garnet powder as the main raw material, adds a certain amount of carrageenan gum organic monomer and a dispersant to make a ceramic slurry, and uses tape casting to prepare transparent ceramics. Utilizing the network macromolecular structure of carrageenan gum, the rare earth-doped garnet powder is solidified in the network molecular structure, and the dissolved substances in the solvent will not migrate with the directional movement of the solvent during the drying process, ensuring the uniformity of the composition and structure of the green body, thereby preparing transparent ceramics with high transparency, density and good uniformity.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional ceramics, and particularly relates to a method for preparing rare-earth doped garnet transparent ceramics by tape casting. Background Art

[0002] In the early 1990s, Professors Mark.A.Janny and O.Omattete of the Oak Ridge National Laboratory in the United States invented the gel casting method, which is a near-net-shape ceramic forming technology. Its forming principle is to form a macromolecular network structure or a ceramic particle network structure through chemical reactions inside the slurry, so that the ceramic slurry injected into the mold quickly solidifies into a ceramic green body. Gel casting requires the preparation of a ceramic slurry with low viscosity and high solid content. A catalyst, an initiator, and an organic monomer are added to the slurry. The organic monomer in the slurry undergoes a polymerization reaction under the action of the initiator and the catalyst, and a three-dimensional network structure is formed in-situ. This network structure gel serves as a framework to fix the ceramic particles in the network, namely in-situ curing forming; acrylamide monomer (AM) was the first to be developed in this system. Potassium persulfate (APS) is required as an initiator and tetramethylethylenediamine (TEMED) is required as a catalyst for monomer polymerization. Moreover, oxygen needs to be isolated during the polymerization process to prevent oxygen from preventing the polymerization of AM monomers, which brings trouble to the operation. At the same time, the monomer acrylamide is harmful to the human nervous system. Therefore, the research on non-toxic gel casting systems has important research value.

[0003] Natural organic macromolecules such as agarose and pectin can form gels during physical or chemical changes. Sarkar et al. first proposed heat-resistant gels and used methyl cellulose as a gelling agent. When heated above the gel temperature, methyl cellulose completely dissolves, and then it is cooled to solidify. In recent years, many studies have begun to use polysaccharides for gel casting of ceramics. Fanelly et al. used agar for gel casting, heating to melt and cooling to solidify. Millan et al. used carrageenan as a gelling agent, and Isabel Santacruz et al. used the synergistic gel of carrageenan and locust bean gum for gel casting. However, these gelling agents need to be cooled after heating to solidify into gels, resulting in the products prepared being unable to simultaneously meet good transparency, uniformity, and density. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this reason, the present invention provides a method for preparing rare-earth doped garnet transparent ceramics by tape casting. The transparent ceramics prepared by this preparation method can simultaneously have high transparency and density, and excellent overall uniformity.

[0005] To solve the above technical problems, the first aspect of the present invention provides a method for preparing transparent ceramics, including the following steps:

[0006] (1) Take the rare earth doped garnet powder, curdlan gum and dispersant, add water and carry out wet ball milling to obtain a ceramic slurry.

[0007] (2) After defoaming the ceramic slurry, use tape casting to obtain a green body.

[0008] (3) Debind the green body and then sinter it in a vacuum environment to obtain the transparent ceramic.

[0009] Specifically, the transparent ceramic of the present invention uses rare earth doped garnet powder as the main raw material, and by adding a certain amount of curdlan gum organic monomer and dispersant, a ceramic slurry is made; then the ceramic slurry is placed in a tape casting doctor blade hopper for tape casting to obtain a green body. Polymerization reaction occurs during the tape casting process of curdlan gum polymer single chains, turning single chain molecules into polymer high molecular gels. Since the gel body is a network macromolecular structure, the rare earth doped garnet powder is solidified in the network molecular structure, and the dissolved substances in the solvent will not migrate with the directional movement of the solvent during the drying process, thus maintaining the uniformity of the composition and structure of the green body, and also avoiding the defect that the density of the green body is reduced due to the addition of a large amount of organic binders and plasticizers in conventional tape casting, while facilitating the removal of pores in the green body during the subsequent vacuum sintering process, and then obtaining a ceramic product with high transparency and good overall uniformity.

[0010] At the same time, curdlan gum is a safe edible gel. It is insoluble in water and most organic solvents such as alcohol, and the curdlan emulsion will solidify to form a gel when heated. The molecular formula of curdlan gum is (C6H 10 O5)n. Common coagulants need to be cooled after heating to solidify and form a gel, but curdlan gum is different. It gradually forms a gel when heated, and the curdlan gum will not melt even when the temperature continues to rise. It is a thermogel. The present invention makes full use of the gel characteristics of curdlan gum, combines tape casting to prepare a high-quality green body, and then obtains a highly transparent and highly dense rare earth doped garnet transparent ceramic through vacuum sintering.

[0011] Preferably, the chemical general formula of the rare earth doped garnet powder is: (A x B 1-x )3Al5O 12 , where: A represents Ce, B represents Y or Lu, and 0 < x ≤ 0.01. That is, the rare earth doped garnet of the present invention is cerium doped yttrium aluminum garnet (YAG) or cerium doped lutetium aluminum garnet (LuAG).

[0012] Preferably, the preparation steps of the rare earth doped garnet powder are: according to the chemical general formula (A x B 1-x)3Al5O 12 Weigh CeO2, Y2O3 or Lu2O3, and Al2O3 according to the stoichiometric ratio, add sintering aids and solvents, and obtain the rare earth-doped garnet powder through ball milling, drying, and calcining at 1200 - 1500 °C for 1 - 3 hours.

[0013] Preferably, the sintering aid includes tetraethyl orthosilicate (TEOS).

[0014] Preferably, the solvent includes ethanol.

[0015] Preferably, the weight of the ethanol is 1 - 1.5 times that of the rare earth-doped garnet powder.

[0016] Preferably, alumina grinding balls are used for ball milling.

[0017] Preferably, the weight of the alumina grinding balls is 3.8 - 4.3 times that of the rare earth-doped garnet powder.

[0018] Preferably, the rotation speed of the ball milling is 60 - 70 r / min.

[0019] Preferably, the ball milling time is 24 - 48 hours.

[0020] Preferably, the dispersant is a polycarboxylic acid compound.

[0021] More preferably, the dispersant is selected from DOLAPIX CE-64 produced by Ciba Specialty Chemicals.

[0022] Specifically, when using a polycarboxylic acid compound as the dispersant, the carboxylate anions are mainly dispersed into anionic groups in the aqueous solution, adsorbed on the surface of the rare earth-doped garnet powder particles to form an electrostatic interaction of like-charge repulsion, enabling the powder to play a good dispersing role in the aqueous slurry, improving the solid content of the slurry while increasing the fluidity of the slurry, thereby increasing the density of the gel green body.

[0023] Preferably, the calcination temperature is 1350 - 1400 °C.

[0024] Preferably, in step (1), the raw material components of the ceramic slurry, by weight, include: 100 parts of rare earth-doped garnet powder, 0.5 - 2.5 parts of carrageenan, and 0.5 - 1.5 parts of dispersant.

[0025] Preferably, in step (1), the solid content of the ceramic slurry is 60 - 80 wt%.

[0026] Preferably, in step (1), the pH of the ceramic slurry is 7 - 10.

[0027] Preferably, in step (2), defoaming is carried out by centrifugal vacuum defoaming, the degree of vacuum is below -0.1 MPa, and the rotation speed of centrifugation is 600 - 1200 r / min.

[0028] More preferably, the rotation speed program of centrifugation is: first centrifuge at a rotation speed of 600 - 700 r / min for 20 - 40 s; then increase the speed to 800 - 900 r / min and centrifuge for 80 - 90 s; then increase the speed to 1100 - 1200 r / min and centrifuge for 20 - 40 s. It is found that adopting this rotation speed program of centrifugation is more conducive to the discharge of bubbles.

[0029] Preferably, in step (2), the solidification temperature of tape casting is 30 - 80 °C.

[0030] More preferably, the control program of the solidification temperature is: first adjust the temperature of the tape casting film to 60 - 80 °C, rotate the film so that the ceramic slurry flows out from the doctor blade, and solidify the ceramic slurry; after the green ceramic body solidifies in situ, reduce the temperature to 30 - 40 °C to slowly dry the moisture in the green body and prevent the green ceramic body from cracking due to excessive shrinkage.

[0031] Preferably, in step (2), the moving speed of the doctor blade in tape casting is 1 - 2 mm / min.

[0032] Preferably, in step (3), the highest temperature of debinding is 700 - 800 °C to remove the carnauba wax and dispersant in the green ceramic body.

[0033] More preferably, in step (3), the temperature regime of debinding is: first heat up from room temperature to 200 - 300 °C at a rate of 0.5 - 1.5 °C / min; then heat up to 300 - 500 °C at a rate of 0.5 - 1 °C / min; then heat up to 500 - 800 °C at a rate of 0.5 - 1.5 °C / min; finally, keep warm for 2 - 5 hours. The main purpose of debinding is to remove organic substances such as carnauba wax and dispersant in the green ceramic body.

[0034] Preferably, in step (3), the highest temperature of sintering is 1400 - 1900 °C.

[0035] More preferably, in step (3), the temperature regime of sintering is: first heat up from room temperature to 900 - 1000 °C at a rate of 8 - 12 °C / min; then heat up to 1000 - 1400 °C at a rate of 4 - 6 °C / min and keep warm for 4 - 6 hours; then heat up to 1400 - 1900 °C at a rate of 1 - 3 °C / min and keep warm for 8 - 10 hours; finally, cool down to 1100 - 1300 °C at a rate of 4 - 6 °C / min and naturally cool to room temperature.

[0036] Further preferably, in step (3), the highest temperature of the sintering is 1750 - 1820 °C.

[0037] Specifically, for ceramic products, their microstructures depend to a considerable extent on their thermal processes. The final microstructure is the result of the combined action of the kinetic factors determined by the firing regime and the thermodynamic factors determined by the chemical composition. In the initial stage of heating in the present invention, since the green body has not shrunk and the pores have not been removed, the heating rate is relatively fast. The second stage (900 - 1000 °C) is the process of powder particles fusing and growing to form grain boundaries, and at the same time, it is the stage of rapid shrinkage of the green body. Therefore, it is necessary to control the growth rate of the grains not to be too fast and carry out heat preservation for a certain period of time to prevent the pores from being encapsulated inside the grains. The third stage (1400 - 1900 °C) is the stage of removing the residual pores in the grain boundary triangular region. In this process, the movement speed of the grain boundary atoms is accelerated, but at the same time, the migration speed of the grain boundary pores should be greater than the grain boundary migration speed. To prevent the grain boundaries from quickly crossing the pores to form intragranular closed pores and make the ceramic opaque, it is necessary to reduce the heating rate and carry out heat preservation for a sufficient period of time. At the same time, control the cooling rate in the high-temperature zone to obtain a transparent and dense ceramic product.

[0038] The second aspect of the present invention provides a transparent ceramic prepared by the above-mentioned method for preparing a transparent ceramic, and the linear transmittance of the transparent ceramic > 66%. The present invention uses polysaccharide curdlan gum as a gelling agent, and the transparent ceramic prepared by in-situ curing tape casting has high transparency.

[0039] Preferably, the linear transmittance of the transparent ceramic is 66.8 - 73.2%.

[0040] Preferably, the theoretical density of the transparent ceramic > 99.9%.

[0041] Further preferably, the theoretical density of the transparent ceramic is 99.90 - 99.99%.

[0042] The third aspect of the present invention provides the application of the above-mentioned transparent ceramic.

[0043] Specifically, a lamp includes the transparent ceramic.

[0044] The above technical solutions of the present invention have at least the following technical effects or advantages compared with the prior art:

[0045] (1) The present invention uses rare earth-doped garnet powder as the main raw material. By adding a certain amount of curdlan gum organic monomer and dispersant, a ceramic slurry is made, and tape casting is used to prepare transparent ceramics. Utilizing the network macromolecular structure of curdlan gum, the rare earth-doped garnet powder is solidified in the network molecular structure. During the drying process, the dissolved substances in the solvent will not migrate with the directional movement of the solvent, ensuring the uniformity of the composition and structure of the green body and improving the density of the green body, thereby preparing transparent ceramics with high transparency, high density, and good overall uniformity.

[0046] (2) The present invention utilizes the thermogelation property of non-toxic polysaccharide curdlan gum to in-situ solidify and form a ceramic green body, combined with the tape casting process, solving the technical problems of the toxicity of the traditional gel system and the reduction of the density of the green body due to the need to add a large amount of organic binders and plasticizers in tape casting, simplifying the preparation process of transparent ceramics. The linear transmittance of the obtained transparent ceramics can reach 66.8 - 73.2%, and the theoretical density can reach 99.90 - 99.99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 XRD patterns of rare earth-doped garnet powder prepared in Examples 1 - 2;

[0048] Figure 2 SEM images of rare earth-doped garnet powder prepared in Example 1;

[0049] Figure 3 Viscosity curve graphs of ceramic slurries prepared in Examples 1, 3 - 4;

[0050] Figure 4 Viscosity curve graphs of ceramic slurries prepared in Examples 1, 5 - 7;

[0051] Figure 5 Linear transmittance curve graphs of transparent ceramics prepared in Examples 1, 5 - 7;

[0052] Figure 6 Linear transmittance curve graphs of transparent ceramics prepared in Comparative Examples 1 - 3;

[0053] Figure 7 Photographs of transparent ceramics prepared in Example 1 and Comparative Examples 1 - 3;

[0054] Figure 8 Photograph of transparent ceramics prepared in Example 8. DETAILED DESCRIPTION OF THE INVENTION

[0055] The present invention will be specifically described below in conjunction with embodiments to facilitate the understanding of those skilled in the art. It is necessary to specifically point out here that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art, based on the above-mentioned inventive content, make non-essential improvements and adjustments to the present invention, which should still fall within the protection scope of the present invention. At the same time, for the raw materials not detailed below, they are all commercially available products; the process steps or preparation methods not detailed are the process steps or preparation methods well known to those skilled in the art.

[0056] Example 1

[0057] A method for preparing a transparent ceramic, comprising the following steps:

[0058] (1) Weigh 674.043 grams of Y2O3 powder, 509.75 grams of Al2O3 powder, and 5.164 grams of CeO2 powder. Add 3.567 grams of tetraethyl orthosilicate (TEOS) as a sintering aid, 1426.7 grams of ethanol, and alumina grinding balls (with a weight 4.3 times that of the total weight of the powder). Put them into a 5L nylon roller for ball milling. The roller mixing speed is 65 r / min, and ball milling is carried out for 36 hours. Then, place the ball-milled slurry in an oven and bake it at 100 °C for 2 hours to volatilize the ethanol and obtain a mixed ceramic powder. After grinding and sieving the ceramic powder, calcine it in air at 1350 °C for 2 hours to remove the organic additives in the powder and obtain cerium-doped yttrium aluminum garnet powder.

[0059] (2) Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 2 grams of DOLAPIX CE-64 dispersant (the addition amount accounts for 1.0 wt% of the cerium-doped yttrium aluminum garnet powder), and 1 gram of curdlan gum (the addition amount accounts for 0.5 wt% of the cerium-doped yttrium aluminum garnet powder). Adjust the pH value to 9 with ammonia water and ball mill for 12 hours to obtain a ceramic slurry.

[0060] (3) Load the ceramic slurry prepared in step (2) into an open plastic container, and then place it on a centrifugal vacuum degassing machine for degassing. During high-speed centrifugation, the vacuum degree reaches below -0.1 Mpa for vacuum degassing. The rotation speed program for centrifugation is as follows: first, centrifuge at a speed of 600 r / min for 30 s; then increase the speed to 900 r / min and centrifuge for 90 s; then increase the speed to 1200 r / min and centrifuge for 30 s. After breaking the vacuum, take out the ceramic slurry and add it to the hopper of the tape casting machine to prepare for gel tape casting to form a green body of the ceramic. Adjust the temperature of the tape casting film to 60°C - 80°C, and the moving speed of the doctor blade to 1 - 2 mm / min, so that the curdlan gum forms a thermogel in-situ curing of the ceramic powder in this temperature range. As the film moves, the gel green body enters the temperature range of 30 - 40°C for slow drying of the ceramic green body to prevent the ceramic green body from cracking due to too fast shrinkage, and a ceramic green body is obtained.

[0061] (4) The ceramic green body prepared in step (3) needs to be subjected to debinding treatment. The temperature regime for debinding is as follows: first, heat from room temperature to 300°C at a rate of 1°C / min; then heat to 400°C at a rate of 0.5°C / min; then heat to 800°C at a rate of 1°C / min and hold for 2 hours; cool naturally with the furnace. The debound ceramic green body is placed in a vacuum furnace and sintered in a vacuum atmosphere (vacuum degree 3.5×10 -3 Pa). The temperature regime for sintering is as follows: first, heat to 1000°C at a heating rate of 10°C / min, then heat to 1450°C at a heating rate of 5°C / min and hold for 5 hours, then heat to 1750°C at a heating rate of 2°C / min and hold for 10 hours, and finally cool to 1200°C at a cooling rate of 5°C / min and cool naturally to room temperature. After grinding and polishing, the Ce:YAG transparent ceramic of this example is obtained.

[0062] Example 2

[0063] Referring to the preparation method of the transparent ceramic in Example 1, only change step (1), and the specific steps are as follows:

[0064] (1) Weigh 674.043 grams of Y2O3 powder, 509.75 grams of Al2O3 powder, 5.164 grams of CeO2 powder, add 3.567 grams of tetraethyl orthosilicate (TEOS) as a sintering aid, 1426.7 grams of ethanol, and alumina grinding balls (with a weight 4.3 times that of the total weight of the powder), and put them into a 5L nylon roller for ball milling. The roller mixing speed is 65 r / mim, and ball milling is carried out for 36 hours; then place the ball-milled slurry in an oven and bake at 100°C for 2 hours, and the ethanol volatilizes to obtain a mixed ceramic powder; after grinding and sieving the ceramic powder, calcine it in the air at 1400°C for 2 hours to remove the organic additives in the powder, and obtain cerium-doped yttrium aluminum garnet powder.

[0065] Example 3

[0066] Referring to the preparation method of the transparent ceramic in Example 1, only step (2) is changed. The specific steps are as follows:

[0067] Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 1 gram of DOLAPIX CE-64 dispersant (the addition amount accounts for 0.5 wt% of the powder), 1 gram of curdlan gum (the addition amount accounts for 0.5 wt% of the powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0068] Example 4

[0069] Referring to the preparation method of the transparent ceramic in Example 1, only step (2) is changed. The specific steps are as follows:

[0070] Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 3 grams of DOLAPIX CE-64 dispersant (the addition amount accounts for 1.5 wt% of the powder), 1 gram of curdlan gum (the addition amount accounts for 0.5 wt% of the powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0071] Example 5

[0072] Referring to the preparation method of the transparent ceramic in Example 1, only step (2) is changed. The specific steps are as follows:

[0073] Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 2 grams of DOLAPIX CE-64 dispersant (the addition amount accounts for 1.0 wt% of the powder), 2 grams of curdlan gum (the addition amount accounts for 1 wt% of the powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0074] Example 6

[0075] Referring to the preparation method of the transparent ceramic in Example 1, only step (2) is changed. The specific steps are as follows:

[0076] Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 2 grams of DOLAPIX CE-64 dispersant (the addition amount accounts for 1.0 wt% of the powder), 3 grams of curdlan gum (the addition amount accounts for 1.5 wt% of the powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0077] Example 7

[0078] Refer to the preparation method of the transparent ceramic in Example 1. Only change step (2). The specific steps are as follows:

[0079] Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 2 grams of DOLAPIX CE-64 dispersant (the addition amount accounts for 1.0 wt% of the powder), 5 grams of curdlan gum (the addition amount accounts for 2.5 wt% of the powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0080] Example 8

[0081] A preparation method of a transparent ceramic, comprising the following steps:

[0082] (1) Weigh 1126.26 grams of Lu2O3 powder, 509.75 grams of Al2O3 powder, 5.164 grams of CeO2 powder, add 3.567 grams of tetraethyl orthosilicate (TEOS) as a sintering aid, 1635.7 grams of ethanol, and alumina grinding balls (the weight is 3.8 times the total weight of the powder), put them into a 5L nylon drum for mixing and ball milling, the drum mixing speed is 65 r / min, and ball mill for 36 hours; then place the mixed powder slurry in an oven and bake at 100 °C for 2 hours, and the ethanol volatilizes to obtain a mixed ceramic powder; after the powder is ground and sieved, it is calcined in air at 1400 °C for 2 hours to remove the organic additives in the powder, and a cerium-doped lutetium aluminum garnet powder is obtained.

[0083] (2) Weigh 200 grams of the lutetium-doped yttrium aluminum garnet powder prepared in step (1), add 80 grams of deionized water, 2 grams of DOLAPIX CE-64 dispersant (the addition amount accounts for 1.0 wt% of the lutetium-doped yttrium aluminum garnet powder), 3 grams of curdlan gum (the addition amount accounts for 1.5 wt% of the lutetium-doped yttrium aluminum garnet powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0084] (3) Load the ceramic slurry prepared in step (2) into an open plastic container, then place it on a centrifugal vacuum degassing machine for degassing. During high-speed centrifugation, the vacuum degree reaches below -0.1 Mpa for vacuum degassing. The centrifugation speed program is: first centrifuge at a speed of 600 r / min for 30 s; then increase the speed to 900 r / min and centrifuge for 90 s; then increase the speed to 1200 r / min and centrifuge for 30 s. After breaking the vacuum, take out the ceramic slurry, add it to the hopper of the tape casting machine to prepare for gel tape casting to form a ceramic green body. Adjust the tape casting film temperature to 60 °C - 80 °C, and the scraper moving speed to 1 - 2 mm / min, so that the curdlan gum forms a thermogel in-situ curing of the ceramic powder in this temperature range. As the film moves, the gel green body reaches the temperature range of 30 - 4 °C for slow drying of the ceramic green body to prevent the ceramic green body from cracking due to too fast shrinkage, and a ceramic green body is obtained.

[0085] (4) The ceramic green body obtained in step (3) needs to be degummed. The temperature regime for degumming is as follows: First, heat from room temperature to 300 °C at a rate of 1 °C / min; then heat to 400 °C at a rate of 0.5 °C / min; then heat to 800 °C at a rate of 1 °C / min and hold for 2 hours; then cool naturally with the furnace. The degummed ceramic green body is placed in a vacuum furnace and sintered under a vacuum atmosphere (vacuum degree 3.5×10 -3 Pa). The temperature regime for sintering is as follows: First, raise the temperature to 1000 °C at a heating rate of 10 °C / min, then raise the temperature to 1450 °C at a heating rate of 5 °C / min and hold for 5 hours, then raise the temperature to 1750 °C at a heating rate of 2 °C / min and hold for 10 hours, and finally cool to 1200 °C at a cooling rate of 5 °C / min and then cool naturally to room temperature. After grinding and polishing, the Ce:LuAG transparent ceramic of this example is obtained.

[0086] Comparative Example 1

[0087] Referring to the preparation method of the transparent ceramic in Example 1, only step (2) is changed. The specific steps are as follows:

[0088] (2) Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 2 grams of DOLAPIX CE-64 dispersant (the addition amount accounts for 1.0 wt% of the cerium-doped yttrium aluminum garnet powder), 1 gram of gellan gum (the addition amount accounts for 0.5 wt% of the cerium-doped yttrium aluminum garnet powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0089] Comparative Example 2

[0090] Referring to the preparation method of the transparent ceramic in Example 1, only step (2) is changed. The specific steps are as follows:

[0091] (2) Weigh 200 grams of the cerium-doped yttrium aluminum garnet powder prepared in step (1), add 200 grams of deionized water, 2 grams of ammonium citrate dispersant (the addition amount accounts for 1.0 wt% of the cerium-doped yttrium aluminum garnet powder), 1 gram of carrageenan (the addition amount accounts for 0.5 wt% of the cerium-doped yttrium aluminum garnet powder), adjust the pH value to 9 with ammonia water, and ball mill for 12 hours to obtain a ceramic slurry.

[0092] Comparative Example 3

[0093] Referring to the preparation method of the transparent ceramic in Example 1, only step (4) is changed. The specific steps are as follows:

[0094] (4) The ceramic blank obtained in step (3) needs to be subjected to binder removal treatment. The temperature system for binder removal is as follows: first, the temperature is raised from room temperature to 300°C at a rate of 1°C / min; then, the temperature is raised to 400°C at a rate of 0.5°C / min; then, the temperature is raised to 800°C at a rate of 1°C / min, and kept at this temperature for 2 hours; and then, the ceramic blank is naturally cooled in the furnace. The debonded ceramic blank is placed in a vacuum furnace and heated in a vacuum atmosphere (vacuum degree 3.5×10 -3 The sintering temperature was as follows: heating to 1750°C at a rate of 10°C / min, holding for 10 hours, and then naturally cooling to room temperature. After grinding and polishing, the Ce:YAG transparent ceramic of this comparative example was obtained.

[0095] Performance Testing

[0096] 1. Phase analysis

[0097] Figure 1 The XRD patterns of the cerium-doped yttrium aluminum garnet powders prepared in Example 1 and Example 2 are shown in FIG. Figure 1 It can be seen that the diffraction peaks of the cerium-doped yttrium aluminum garnet powder prepared by calcining at 1350℃ and 1400℃ for 2 hours all correspond to the cubic YAG crystal phase, and no intermediate transition phase YAP or YAM appears, indicating that the oxides in the raw materials have reacted completely under this temperature condition.

[0098] 2. Micromorphology

[0099] Figure 2 This is the SEM image of the cerium-doped yttrium aluminum garnet powder prepared in Example 1. Figure 2 It can be seen that the particle size distribution of the powder particles is uniform and the dispersion is good without obvious agglomeration.

[0100] 3. Ceramic slurry viscosity

[0101] Figure 3 The viscosity curves of the ceramic slurries prepared in Examples 1 and 3-4 are shown in FIG. Figure 3 It can be seen that when 0.5 wt % of Curdlan gum is added and 0.5-1.5 wt % of DOLAPIX CE-64 dispersant is added respectively, the viscosity of the prepared ceramic slurry is 5-15 Pa·S.

[0102] Figure 4 The viscosity curves of the ceramic slurries prepared in Examples 1, 5-7 are shown in FIG. Figure 4 It can be seen that when 1.0 wt% of DOLAPIX CE-64 dispersant is added and 0.5-2.5 wt% of Curdlan gum is added respectively, the viscosity of the prepared ceramic slurry is 10-20 Pa·S, and the slurry is easy to flow and form at this viscosity.

[0103] 4. Linear transmittance

[0104] According to the standard GB / T 7962.12-1987 "Test Methods for Colorless Optical Glass - Test Method for Spectral Transmittance", the linear transmittance of the transparent ceramic samples prepared in Examples 1, 5 - 7 was measured. The Archimedes drainage method was used to test the measured density of the samples and compare it with the theoretical density value of the ceramics to calculate the theoretical density of the samples. The results are shown in Table 1 and Figures 5 - 6 as follows.

[0105] Table 1:

[0106] Sample Linear transmittance (%) Theoretical density (%) Example 1 66.8 99.93 Example 5 70.3 99.95 Example 6 73.2 99.99 Example 7 68.4 99.90 Comparative Example 1 37.5 99.83 Comparative Example 2 34.7 99.75 Comparative Example 3 33.0 99.72

[0107] As can be seen from Table 1 and Figures 5 - 6 it can be known that the linear transmittance of the transparent ceramic samples prepared in Examples 1, 5 - 7 can reach 66.8 - 73.2%, and the theoretical density can reach more than 99.90%, having the characteristics of high transparency and high density. Moreover, the transparency and density of Examples 2 - 4 are similar to those of Examples 1, 5 - 7. For Comparative Examples 1 - 3 prepared by using different colloids, dispersants and sintering systems respectively relative to Example 1, the linear transmittance and theoretical density of the prepared fluorescent transparent ceramics have decreased to a large extent. This shows that the performance of the transparent ceramics of the present invention is closely related to the selection of colloids and dispersants, as well as the sintering system.

[0108] 5. Uniformity

[0109] Figure 7 and Figure 8 are respectively the physical pictures of the transparent ceramics prepared in Example 1, Comparative Examples 1 - 3 and Example 8. As can be seen from Figures 7 - 8 it, the ceramic products prepared in Example 1 and Example 8 by using the preparation method of the present invention both have good transparency and no obvious bubbles. However, for Comparative Examples 1 - 3, due to using other similar gel raw materials and dispersants respectively, as well as a non-gradient temperature sintering system, the prepared ceramic products have obvious fogginess and obvious bubbles, and both the transparency and uniformity are not good.

[0110] For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made without creative labor. Therefore, all simple improvements made by those skilled in the art based on the disclosure of the present invention should be within the protection scope of the present invention. The above embodiments are the preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made thereto shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a transparent ceramic, characterized in that, It includes the following steps: (1) Take rare earth-doped garnet powder, curdlan gum and a dispersant, add water and carry out wet ball milling to obtain a ceramic slurry; The chemical general formula of the rare earth-doped garnet powder is: (A x B 1-x )3Al5O 12 , where: A represents Ce, B represents Y or Lu, and 0 < x ≤ 0.01; the preparation steps of the rare earth-doped garnet powder are as follows: according to the chemical stoichiometric ratio of the chemical general formula (A x B 1-x )3Al5O 12 , weigh CeO2, Y2O3 or Lu2O3, and Al2O3, add a sintering aid and a solvent, grind by ball milling, dry, and calcine at 1200-1500 °C for 1-3 hours to obtain the rare earth-doped garnet powder; the sintering aid includes tetraethyl orthosilicate, and the solvent includes ethanol; The dispersant is a polycarboxylic acid compound; The raw material components of the ceramic slurry, by weight, include: 100 parts of rare earth-doped garnet powder, 0.5 - 2.5 parts of curdlan gum and 0.5 - 1.5 parts of dispersant; the solid content of the ceramic slurry is 60 - 80 wt%; the pH of the ceramic slurry is 7 - 10; (2) After defoaming the ceramic slurry, carry out tape casting to obtain a green ceramic body; (3) Debind the green ceramic body, and then sinter it in a vacuum environment to obtain the transparent ceramic; The temperature regime for the sintering is: first heat from room temperature to 900 - 1000 °C at a rate of 8 - 12 °C / min; then heat from 1000 - 1400 °C at a rate of 4 - 6 °C / min and hold for 4 - 6 hours; then heat from 1400 - 1900 °C at a rate of 1 - 3 °C / min and hold for 8 - 10 hours; finally cool from 1400 - 1900 °C at a rate of 4 - 6 °C / min to 1100 - 1300 °C and naturally cool to room temperature.

2. The preparation method of the transparent ceramic according to claim 1, characterized in that, In step (2), the solidification temperature of the tape casting is 30 - 80 °C; and / or, the moving speed of the doctor blade for the tape casting is 1 - 2 mm / min.

3. The method for preparing the transparent ceramic according to claim 1, wherein, In step (3), the maximum temperature for debinding is 700 - 800 °C; and / or, the maximum temperature for sintering is 1400 - 1900 °C.

4. A transparent ceramic, characterized in that, Prepared by the method for preparing a transparent ceramic according to any one of claims 1 - 3, the linear transmittance of the transparent ceramic > 66%; and / or, the theoretical density of the transparent ceramic > 99.9%.

5. A lighting fixture, characterized in that, It includes the transparent ceramic according to claim 4.

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