Yttrium oxide ceramic and preparation method thereof

Abstract

The invention provides yttrium oxide ceramic and a preparation method thereof, and the preparation method comprises the following steps: uniformly mixing yttrium salt and a composite sintering agent to obtain a mixed raw material, and preparing yttrium oxide powder; uniformly mixing a dispersing agent, a binding agent, alkali liquor and a solvent to obtain a premixed solution; uniformly mixing the yttrium oxide powder and the premixed liquid to obtain suspension slurry, injecting the suspension slurry into a mold, and removing liquid in the suspension slurry to obtain a green body; and carrying out gradient drying and segmented sintering on the green body to obtain the yttrium oxide ceramic. According to the yttrium oxide ceramic and the preparation method thereof provided by the invention, the sintering temperature in the preparation process can be remarkably reduced, and meanwhile, the compactness of the yttrium oxide ceramic and the uniformity of a microstructure are improved.

Description

Technical Field

[0001] This invention relates to the field of inorganic ceramic material preparation technology, specifically to a yttrium oxide ceramic and its preparation method. Background Technology

[0002] In the modern semiconductor industry, with the rapid development of power electronics, radio frequency devices, and optoelectronic devices, increasingly stringent requirements are being placed on ceramic substrates, which serve as their core supporting materials. Yttrium oxide (Y₂O₃) ceramics, with their high melting point, excellent thermal conductivity, extremely low dielectric loss, and superior chemical stability, are considered ideal candidate materials for manufacturing high-performance semiconductor substrates, effectively ensuring the stability and reliability of semiconductor devices. However, the high sintering temperature required for Yttrium oxide ceramic preparation leads to high energy consumption and production costs. Furthermore, the densification and performance uniformity of the ceramics are not high. Therefore, it is difficult to effectively reduce the sintering temperature while simultaneously ensuring high density and uniform particle size of Yttrium oxide ceramics, often resulting in a trade-off. Summary of the Invention

[0003] This invention proposes a yttrium oxide ceramic and its preparation method. The yttrium oxide ceramic and its preparation method provided by this invention can significantly reduce the sintering temperature in the preparation process, reduce energy consumption and production costs, and at the same time improve the density and uniformity of the microstructure of the yttrium oxide ceramic.

[0004] To solve the above-mentioned technical problems, the present invention provides a method for preparing yttrium oxide ceramics, comprising at least the following steps:

[0005] Yttrium salt and composite sintering agent were mixed evenly and used as a mixed raw material to prepare yttrium oxide powder;

[0006] The dispersant, binder, alkali solution and solvent are mixed evenly to obtain a premixed solution;

[0007] The yttrium oxide powder and the premixed liquid are mixed evenly to obtain a suspension slurry, which is then injected into a mold. The liquid in the suspension slurry is then removed to obtain a green body.

[0008] The green body is subjected to gradient drying and segmented sintering to obtain yttrium oxide ceramic.

[0009] In one embodiment of the present invention, the composite sintering agent includes at least silicon dioxide, titanium dioxide and zinc oxide.

[0010] In one embodiment of the present invention, the content of silicon dioxide in the composite sintering agent is 15wt%-45wt%, the content of titanium dioxide in the composite sintering agent is 20wt%-50wt%, and the content of zinc oxide in the composite sintering agent is 30wt%-65wt%.

[0011] In one embodiment of the present invention, the preparation of the yttrium oxide powder includes at least the following steps:

[0012] The raw materials and reagents are mixed evenly to obtain a raw material solution;

[0013] The raw material solution is mixed with a complexing agent, heated, and stirred to obtain a sol, which is then allowed to stand and age to form a gel; and

[0014] The gel was calcined to obtain the yttrium oxide powder.

[0015] In one embodiment of the present invention, one or more of the following features are included:

[0016] The complexing agent includes citric acid;

[0017] The molar ratio of yttrium ions to the complexing agent in the raw material solution is 1:(1-3);

[0018] The temperature for heating the raw material solution and the complexing agent is 50℃-90℃;

[0019] The aging time is 5-24 hours.

[0020] The gel is calcined at a temperature of 500℃-900℃;

[0021] The gel is calcined for 1-10 hours.

[0022] In one embodiment of the present invention, one or more of the following features are included:

[0023] The dispersant includes at least one of tartaric acid, polyvinylpyrrolidone, polyacrylic acid, and polyethylene glycol;

[0024] The adhesive includes at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and polyacrylamide;

[0025] The alkaline solution includes at least one of potassium hydroxide, ammonia, and lithium hydroxide.

[0026] The pH value of the premixed solution is 9-12;

[0027] The mass of the dispersant is 0.05%-2.5% of the mass of the yttrium oxide powder;

[0028] The mass of the binder is 0.5%-4% of the mass of the yttrium oxide powder;

[0029] The solid content in the suspension slurry is 20wt%-55wt%.

[0030] In one embodiment of the present invention, when the green blank is gradient dried, the green blank is first kept at a first temperature for a first time, then kept at a second temperature for a second time, and finally kept at a third temperature for a third time.

[0031] In one embodiment of the present invention, when sintering the green blank in stages, at least two-stage sintering is adopted. In the first stage of sintering the green blank, the green blank is heated to a first sintering temperature at a first heating rate and held at the temperature for a first sintering time to obtain a pre-sintered blank. Then, the process is transferred to the second stage of sintering, where the pre-sintered blank is heated to a second sintering temperature at a second heating rate and held at the temperature for a second sintering time.

[0032] In one embodiment of the present invention, one or more of the following features are included:

[0033] The first heating rate is 0.1℃ / min - 2℃ / min;

[0034] The first sintering temperature is 300℃-650℃;

[0035] The first sintering time is 0.5h-10h;

[0036] The second heating rate is 2℃ / min-8℃ / min;

[0037] The second sintering temperature is 1200℃-1500℃;

[0038] The second sintering time is 2h-12h.

[0039] The present invention also provides a yttrium oxide ceramic obtained by the above-described preparation method.

[0040] In summary, this invention proposes a yttrium oxide ceramic and its preparation method, which can significantly reduce the sintering temperature of yttrium oxide ceramic, thereby significantly reducing energy consumption and preparation costs; at the same time, it can achieve uniform distribution of sintering agent in yttrium oxide powder, thereby improving the density and microstructure uniformity of yttrium oxide ceramic and inhibiting abnormal growth of yttrium oxide grains; it can also avoid cracking of green bodies during the drying process, thus improving the quality of yttrium oxide ceramic. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a scanning electron microscope characterization image of yttrium oxide ceramic in Example 1 of the present invention.

[0043] Figure 2 This is a scanning electron microscope characterization image of the yttrium oxide ceramic in Comparative Example 1 of the present invention.

[0044] Figure 3 This is a scanning electron microscope characterization image of the yttrium oxide ceramic in Comparative Example 2 of the present invention. Detailed Implementation

[0045] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0046] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0047] The technical solution of the present invention will be further described in detail below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0048] This invention proposes a method for preparing yttrium oxide ceramics, which includes at least steps S11-S14.

[0049] Step S11: Mix yttrium salt and composite sintering agent evenly and use the mixture as raw material to prepare yttrium oxide powder.

[0050] Step S12: Mix the dispersant, binder, alkali solution and solvent evenly to obtain a premixed solution.

[0051] Step S13: Mix yttrium oxide powder and premixed liquid evenly to obtain a suspension slurry, then inject it into a mold and remove the liquid from the suspension slurry to obtain a green body.

[0052] Step S14: Gradient drying and segmented sintering of the green body are performed to obtain yttrium oxide ceramic.

[0053] In one embodiment of the present invention, in step S11, yttrium salt and composite sintering agent are mixed uniformly as a mixed raw material. The yttrium salt includes, for example, at least one of organic yttrium salts and inorganic yttrium salts; the organic yttrium salt includes, for example, at least one of isopropoxide yttrium and ethanol yttrium; the inorganic yttrium salt includes, for example, at least one of yttrium nitrate, yttrium chloride, and yttrium acetate; the composite sintering agent includes, for example, silicon dioxide, titanium dioxide, and zinc oxide; the content of silicon dioxide in the composite sintering agent is, for example, 15wt%-45wt%; the content of titanium dioxide in the composite sintering agent is, for example, 20wt%-50wt%; and the content of zinc oxide in the composite sintering agent is, for example, 30wt%-65wt%.

[0054] In one embodiment of the present invention, after obtaining the mixed raw materials, yttrium oxide powder is prepared using the mixed raw materials in step S11. The mass of the composite sintering agent in the mixed raw materials is 0.5%-5% of the mass of the yttrium oxide powder, specifically, for example, 1%. The preparation method of the yttrium oxide powder is, for example, the sol-gel method, co-precipitation method, hydrothermal method, or spray pyrolysis method. In this embodiment, the sol-gel method is used as an example to illustrate the preparation method. The sol-gel method can prepare yttrium oxide powder with small particle size, high purity, and good activity, laying the foundation for obtaining high-density yttrium oxide ceramics through subsequent low-temperature sintering. Specifically, the mixed raw materials and reagents are first mixed evenly to obtain a raw material solution. Then, the raw material solution is mixed with a complexing agent, heated, and stirred to obtain a sol. After static aging, a gel is formed. Finally, the gel is calcined to obtain yttrium oxide powder. The reagents include at least one of deionized water and ethanol, the complexing agent includes citric acid, the molar ratio of yttrium ions to complexing agent in the raw material solution is, for example, 1:(1-3), specifically 1:2, the heating temperature of the raw material solution and complexing agent is, for example, 50℃-90℃, specifically 85℃, the standing aging time is, for example, 5h-24h, specifically 15h, the calcination temperature of the gel is, for example, 500℃-900℃, specifically 850℃, and the calcination time of the gel is, for example, 1h-10h, specifically 3.5h.

[0055] In one embodiment of the present invention, after obtaining yttrium oxide powder, in step S12, a dispersant and a binder are added to a solvent and mixed evenly to obtain a mixture. Then, an alkaline solution is added and mixed to adjust the pH value of the mixture until it reaches, for example, 9-12. The addition of the alkaline solution is then stopped, and a premixed solution is obtained. The dispersant includes, for example, at least one of tartaric acid, polyvinylpyrrolidone, polyacrylic acid, and polyethylene glycol. The mass of the dispersant is 0.05%-2.5% of the mass of the yttrium oxide powder. The dispersant has good steric hindrance or electrostatic repulsion, effectively preventing the yttrium oxide powder from agglomerating and promoting its uniform dispersion in the aqueous phase during subsequent mixing of the yttrium oxide powder and the premixed solution. In this embodiment, the dispersant includes, for example, tartaric acid and polyvinylpyrrolidone, with a mass ratio of tartaric acid to polyvinylpyrrolidone of, for example, (1-5):1.

[0056] In one embodiment of the present invention, in the premixed liquid of step S12, the binder includes at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and polyacrylamide, and the mass of the binder is 0.5%-4% of the mass of yttrium oxide powder. The binder is used to provide sufficient mechanical strength for subsequent green body forming. Furthermore, the solvent includes at least one of deionized water and ethanol, and the concentration of the alkali solution is, for example, 0.5 mol / L-3 mol / L. The alkali solution includes at least one of potassium hydroxide, ammonia, and lithium hydroxide, wherein the NH3 in the ammonia solution can volatilize during subsequent calcination, preventing ammonia residue in the yttrium oxide ceramic; the residual amount of lithium hydroxide in the yttrium oxide ceramic is small, and it has little interference with dielectric properties. Adjusting the pH of the premixed solution to 9-12 with alkali solution can, on the one hand, ensure that the dispersant is fully ionized, giving full play to the electrostatic repulsion or steric hindrance of the dispersant, ensuring the best dispersion effect of each component, especially the sintering agent, and preventing the agglomeration of yttrium oxide powder during the mixing of yttrium oxide powder and premixed solution. On the other hand, it can avoid the dissolution or excessive hydrolysis of yttrium oxide powder.

[0057] In one embodiment of the present invention, after obtaining the premixed liquid, in step S13, the yttrium oxide powder and the premixed liquid are mixed evenly to obtain a suspension slurry, wherein the solid content in the suspension slurry is, for example, 20wt%-55wt%. Further, after obtaining the suspension slurry, the suspension slurry is subjected to vacuum treatment to completely remove air bubbles entrained in the suspension slurry, preventing air bubbles from forming pores during subsequent sintering and affecting the density of the yttrium oxide ceramic product.

[0058] In one embodiment of the present invention, after vacuum treatment of the suspension slurry, in step S13, a mold is installed on a porous support plate, and then the suspension slurry is injected into the mold. For example, liquid in the suspension slurry is removed by suction molding, and the liquid flows out from the porous support plate, while the solid particles in the suspension slurry gradually accumulate and form a green body with a certain shape and strength in the mold. The green body is obtained after demolding. Suction molding includes, for example, vacuum filtration or pressure filtration.

[0059] In one embodiment of the present invention, after obtaining the green body, in step S14, the green body is subjected to gradient drying to slowly remove moisture and organic solvents from the green body, effectively avoiding cracking and defects caused by rapid drying, and ensuring the integrity of the green body and the quality of subsequent sintering. Specifically, during gradient drying, the green body is first held at a first temperature for a first time, then held at a second temperature for a second time, and finally held at a third temperature for a third time. The first temperature is, for example, 10℃-40℃, specifically 30℃; the first time is, for example, 0.5h-10h, specifically 2h; the second temperature is, for example, 40℃-70℃, specifically 50℃; the second time is, for example, 2h-24h, specifically 13h; the third temperature is, for example, 70℃-100℃, specifically 70℃; and the third time is, for example, 3h-10h, specifically 4h.

[0060] In one embodiment of the present invention, after gradient drying of the green body, in step S14, the green body is further sintered in stages to obtain yttrium oxide ceramic. For example, at least two-stage sintering is employed. In this embodiment, for example, a two-stage sintering of the green body is employed. Specifically, the green body is placed in a sintering furnace, and a first-stage sintering is initiated. The green body is heated to a first sintering temperature at a first heating rate and held at that temperature for a first sintering time to obtain a pre-sintered green body. Then, a second-stage sintering is initiated, where the pre-sintered green body is heated to a second sintering temperature at a second heating rate and held at that temperature for a second sintering time. The pre-sintered green body has formed yttrium oxide ceramic. Then, the sintering furnace and the yttrium oxide ceramic are cooled to room temperature, and the yttrium oxide ceramic is removed from the sintering furnace. The atmosphere inside the sintering furnace is, for example, an inert gas such as argon or air; the pressure inside the sintering furnace is, for example, atmospheric pressure; the first heating rate is, for example, 0.1℃ / min-2℃ / min; the first sintering temperature is, for example, 300℃-650℃; the first sintering time is, for example, 0.5h-10h; the second heating rate is, for example, 2℃ / min-8℃ / min; the second sintering temperature is, for example, 1200℃-1500℃; and the second sintering time is, for example, 2h-12h. Specifically, the first-stage sintering process thoroughly removes residual binders and dispersants from the green body, preventing their decomposition at high temperatures that could generate gases and create pores within the yttrium oxide ceramic, thus increasing its density. Furthermore, by controlling the initial heating rate during the first-stage sintering, organic materials such as binders and dispersants can be slowly decomposed, allowing gases to escape smoothly. However, an excessively high initial heating rate can lead to gas retention, forming pores or cracking of the green body; conversely, an insufficient initial heating rate prolongs the sintering time, increases energy consumption, and may leave residual carbon impurities. Moreover, controlling the second-stage sintering and the second heating rate can improve the density of the yttrium oxide ceramic and inhibit abnormal grain growth. Specifically, an excessively high second heating rate results in coarse yttrium oxide grains, while an insufficient second heating rate increases costs and may cause localized enrichment of the composite sintering agent.

[0061] In the preparation method of yttrium oxide ceramics provided by this invention, in step S11, a sintering agent is added during the preparation of yttrium oxide powder. Compared with directly mechanically mixing yttrium oxide powder and sintering agent, this helps the sintering agent to be uniformly distributed in the yttrium oxide powder, avoiding local enrichment or depletion of sintering agent in the yttrium oxide powder. This allows the densification behavior of each region in the green body to be synchronized during sintering in step S14, avoiding defects such as the formation of pores and abnormal growth of yttrium oxide grains in the green body, and ultimately improving the overall density, mechanical properties, and electrical properties uniformity of the yttrium oxide ceramic. Moreover, compared with a single sintering agent, the composite sintering agent used in step S11, which combines ZnO-TiO2-SiO2 in a near ternary eutectic ratio, is added to the yttrium oxide powder preparation process. The multiphase liquid phase formed at low temperature by the ternary composite sintering agent can significantly reduce the sintering temperature in step S14. Specifically, the ZnO-TiO2-SiO2 ternary combination generates a highly wettable liquid phase at approximately 1100℃, promoting rapid interparticle diffusion and neck growth to form a dense yttrium oxide structure. This reduces the sintering temperature of Y2O3 from ≥1700℃ to 1200℃-1500℃. Furthermore, single or binary sintering agents have high melting temperatures, low liquid phase amounts, and low diffusion rates, making it difficult to achieve densification of yttrium oxide ceramics at low sintering temperatures. Achieving densification requires longer sintering times and higher sintering temperatures, resulting in high energy consumption and costs. In contrast, the liquid phase generated by ternary sintering agents has diverse components, strong miscibility, fast diffusion rates, and significant synergistic effects. This allows for the acquisition of yttrium oxide ceramics with high density and excellent mechanical properties at lower sintering temperatures and shorter sintering times.

[0062] In the preparation method of yttrium oxide ceramics provided by this invention, the ternary composite sintering agent system is closely related to multiple process parameters, including low-temperature sintering, sol-gel method for preparing yttrium oxide powder, pH control of the premixed solution, and gradient drying process. These parameters work synergistically to improve the density of the yttrium oxide ceramics. Specifically, regarding low-temperature sintering, at a precisely controlled sintering temperature of 1200℃-1500℃, the liquid phase of the composite sintering agent is in its optimal active state, promoting particle rearrangement, dissolution-precipitation, and grain boundary migration. Regarding the sol-gel method, it provides high-purity and highly active yttrium oxide powder, ensuring that the composite sintering agent can exert its synergistic effect under a precise and expected chemical environment. Precise pH control of the premixed solution is crucial for ensuring uniform dispersion of yttrium oxide powder in the suspension slurry, thus laying the foundation for subsequent synergistic reactions. Gradient drying maintains the carefully constructed, dense green body structure with uniformly distributed sintering agent, preventing cracking that could compromise the effectiveness of the composite sintering agent. These parameters together construct an interconnected and mutually reinforcing process system, aiming to maximize the synergistic effect with the composite sintering agent. Starting from multiple mechanisms such as liquid phase sintering, grain boundary regulation, grain growth inhibition, gas phase transport promotion and sintering enhancement, the sintering activation energy is significantly reduced, enabling the high density of yttrium oxide ceramics to be achieved at lower sintering temperatures.

[0063] Please see Figure 1 As shown, the present invention also provides a yttrium oxide ceramic, obtained by the above-described preparation method, which will not be elaborated upon here. The yttrium oxide ceramic exhibits high density, specifically, a density greater than or equal to 99.4%, and a uniform microstructure, specifically characterized by uniform yttrium grain size and the absence of abnormally large grains.

[0064] The present invention will be explained in more detail below by referring to embodiments, which should not be construed as limiting. Appropriate modifications can be made within the scope of the present invention, and all such modifications fall within the technical scope of the present invention.

[0065] Example 1

[0066] Preparation of yttrium oxide powder: Yttrium nitrate and a composite sintering agent were mixed uniformly as a raw material. The raw material was then mixed uniformly with deionized water to obtain a raw material solution. This solution was then mixed with citric acid and stirred at 85°C to obtain a sol. After standing and aging for 5 hours, a gel was formed. Finally, the gel was calcined at 850°C for 3.5 hours to obtain yttrium oxide powder. The molar ratio of yttrium ions to citric acid in the raw material solution was 1:2. The composite sintering agent consisted of silicon dioxide, titanium dioxide, and zinc oxide. The content of silicon dioxide in the composite sintering agent was 24 wt%, the content of titanium dioxide was 28 wt%, and the content of zinc oxide was 48 wt%. The mass of the composite sintering agent in the mixed raw material was 1% of the mass of the yttrium oxide powder.

[0067] Preparation of the premix: A mixture of tartaric acid and polyvinylpyrrolidone (PPP) in a mass ratio of 2:1 was added to deionized water and mixed thoroughly. After obtaining the mixture, a 0.8 mol / L potassium hydroxide solution was added and mixed until the pH of the mixture reached 10.5. The addition of potassium hydroxide was then stopped, yielding the premix. The mass of the tartaric acid and PPP mixture was 0.4% of the mass of the yttrium oxide powder, and the mass of the polyvinyl alcohol was 2% of the mass of the yttrium oxide powder.

[0068] Preparation of suspension slurry: Yttrium oxide powder and premixed liquid were mixed and stirred for 1 hour, and then vacuumed for 30 minutes to obtain suspension slurry with a solid content of 40 wt%.

[0069] Preparation of green body: A mold is installed on a porous support plate. Then, the suspension slurry is injected into the mold. The liquid in the suspension slurry is removed by vacuum filtration. The liquid flows out from the porous support plate, while the solid particles in the suspension slurry gradually accumulate in the mold to form a green body with a certain shape and strength. After demolding, the green body is obtained.

[0070] Preparation of yttrium oxide ceramics: The green body was held at 30℃ for 2 hours, then at 50℃ for 3 hours, and finally at 70℃ for 4 hours to complete gradient drying. Next, the green body was placed in a sintering furnace under an argon protective atmosphere to begin the first stage of sintering. The green body was heated to 550℃ at a rate of 1℃ / min and held for 0.5 hours to complete the pre-sintering treatment, obtaining a pre-sintered green body. Then, the second stage of sintering was carried out, where the pre-sintered green body was heated to 1400℃ at a rate of 4℃ / min and held for 4 hours. After sintering, the pre-sintered green body formed yttrium oxide ceramics. The sintering furnace and yttrium oxide ceramics were then cooled to room temperature, and the yttrium oxide ceramics were removed from the sintering furnace.

[0071] Example 2

[0072] Preparation of yttrium oxide powder: Yttrium nitrate and a composite sintering agent were mixed evenly as a raw material. The raw material was then mixed evenly with deionized water to obtain a raw material solution. This solution was then mixed with citric acid and stirred at 60°C to obtain a sol. The sol was allowed to stand for 10 hours to form a gel. Finally, the gel was calcined at 700°C for 5 hours to obtain yttrium oxide powder. The molar ratio of yttrium ions to citric acid in the raw material solution was 1:3. The composite sintering agent consisted of silicon dioxide, titanium dioxide, and zinc oxide. The content of silicon dioxide in the composite sintering agent was 20 wt%, the content of titanium dioxide was 40 wt%, and the content of zinc oxide was 40 wt%. The mass of the composite sintering agent in the mixed raw material was 2% of the mass of the yttrium oxide powder.

[0073] Preparation of the premix: A mixture of tartaric acid and polyvinylpyrrolidone (PVP) in a mass ratio of 3:1 was added to deionized water and mixed thoroughly. After obtaining the mixture, a 2 mol / L potassium hydroxide solution was added and mixed until the pH of the mixture reached 11. The addition of potassium hydroxide was then stopped, yielding the premix. The mass of the tartaric acid and PPVP mixture was 1.5% of the mass of the yttrium oxide powder, and the mass of the polyvinyl alcohol was 0.5% of the mass of the yttrium oxide powder.

[0074] Preparation of suspension slurry: Yttrium oxide powder and premixed liquid were mixed and stirred for 1 hour, and then vacuumed for 30 minutes to obtain suspension slurry with a solid content of 20 wt%.

[0075] Preparation of green body: A mold is installed on a porous support plate. Then, the suspension slurry is injected into the mold. The liquid in the suspension slurry is removed by vacuum filtration. The liquid flows out from the porous support plate, while the solid particles in the suspension slurry gradually accumulate in the mold to form a green body with a certain shape and strength. After demolding, the green body is obtained.

[0076] Preparation of yttrium oxide ceramics: The green body was held at 10℃ for 10 h, then at 60℃ for 10 h, and finally at 70℃ for 3 h to complete gradient drying. Next, the green body was placed in a sintering furnace under an argon protective atmosphere to begin the first stage of sintering. The green body was heated to 600℃ at a rate of 0.5℃ / min and held for 3 h to complete the pre-sintering treatment, obtaining a pre-sintered green body. Then, the second stage of sintering was carried out, where the pre-sintered green body was heated to 1450℃ at a rate of 5℃ / min and held for 3 h. The pre-sintered green body had formed yttrium oxide ceramics. The sintering furnace and yttrium oxide ceramics were then cooled to room temperature, and the yttrium oxide ceramics were removed from the sintering furnace.

[0077] Example 3

[0078] Preparation of yttrium oxide powder: Yttrium nitrate and a composite sintering agent were mixed uniformly as a raw material. The raw material was then mixed uniformly with deionized water to obtain a raw material solution. This solution was then mixed with citric acid and stirred at 70°C to obtain a sol. The sol was allowed to stand for 12 hours to form a gel. Finally, the gel was calcined at 600°C for 3.5 hours to obtain yttrium oxide powder. The molar ratio of yttrium ions to citric acid in the raw material solution was 1:1. The composite sintering agent consisted of silicon dioxide, titanium dioxide, and zinc oxide. The content of silicon dioxide in the composite sintering agent was 30 wt%, the content of titanium dioxide was 20 wt%, and the content of zinc oxide was 50 wt%. The mass of the composite sintering agent in the mixed raw material was 0.5% of the mass of the yttrium oxide powder.

[0079] Preparation of the premix: A mixture of tartaric acid and polyvinylpyrrolidone (PPP) in a 1:1 mass ratio was added to deionized water and mixed thoroughly. After obtaining the mixture, a 0.5 mol / L potassium hydroxide solution was added and mixed until the pH of the mixture reached 9.5. The addition of potassium hydroxide was then stopped, yielding the premix. The mass of the tartaric acid and PPP mixture was 2.5% of the mass of the yttrium oxide powder, and the mass of the polyvinyl alcohol was 3% of the mass of the yttrium oxide powder.

[0080] Preparation of suspension slurry: Yttrium oxide powder and premixed liquid were mixed and stirred for 1 hour, and then vacuumed for 30 minutes to obtain suspension slurry with a solid content of 50 wt%.

[0081] Preparation of green body: A mold is installed on a porous support plate. Then, the suspension slurry is injected into the mold. The liquid in the suspension slurry is removed by vacuum filtration. The liquid flows out from the porous support plate, while the solid particles in the suspension slurry gradually accumulate in the mold to form a green body with a certain shape and strength. After demolding, the green body is obtained.

[0082] Preparation of yttrium oxide ceramics: The green body was held at 20℃ for 8 hours, then at 70℃ for 2 hours, and finally at 90℃ for 3 hours to complete gradient drying. Next, the green body was placed in a sintering furnace under an argon protective atmosphere to begin the first stage of sintering. The green body was heated to 650℃ at a rate of 1.5℃ / min and held for 1 hour to complete the pre-sintering treatment, obtaining a pre-sintered green body. Then, the second stage of sintering was carried out, where the pre-sintered green body was heated to 1200℃ at a rate of 5℃ / min and held for 5 hours. The pre-sintered green body had formed yttrium oxide ceramics. The sintering furnace and yttrium oxide ceramics were then cooled to room temperature, and the yttrium oxide ceramics were removed from the sintering furnace.

[0083] Example 4

[0084] Preparation of yttrium oxide powder: Yttrium nitrate and a composite sintering agent were mixed evenly as a raw material. The raw material was then mixed evenly with deionized water to obtain a raw material solution. This solution was then mixed with citric acid and stirred at 80°C to obtain a sol. The sol was allowed to stand for 7 hours to form a gel. Finally, the gel was calcined at 900°C for 1 hour to obtain yttrium oxide powder. The molar ratio of yttrium ions to citric acid in the raw material solution was 1:1.5. The composite sintering agent consisted of silicon dioxide, titanium dioxide, and zinc oxide. The content of silicon dioxide in the composite sintering agent was 40 wt%, the content of titanium dioxide was 20 wt%, and the content of zinc oxide was 40 wt%. The mass of the composite sintering agent in the mixed raw material was 3% of the mass of the yttrium oxide powder.

[0085] Preparation of the premix: A mixture of tartaric acid and polyvinylpyrrolidone (PPP) in a mass ratio of 3:1 was added to deionized water and mixed thoroughly. After obtaining the mixture, a 2.5 mol / L potassium hydroxide solution was added and mixed until the pH of the mixture reached 10. The addition of potassium hydroxide was then stopped, yielding the premix. The mass of the tartaric acid and PPP mixture was 0.1% of the mass of yttrium oxide powder, and the mass of polyvinyl alcohol was 3.5% of the mass of yttrium oxide powder.

[0086] Preparation of suspension slurry: Yttrium oxide powder and premixed liquid were mixed and stirred for 1 hour, and then vacuumed for 30 minutes to obtain suspension slurry with a solid content of 50 wt%.

[0087] Preparation of green body: A mold is installed on a porous support plate. Then, the suspension slurry is injected into the mold. The liquid in the suspension slurry is removed by vacuum filtration. The liquid flows out from the porous support plate, while the solid particles in the suspension slurry gradually accumulate in the mold to form a green body with a certain shape and strength. After demolding, the green body is obtained.

[0088] Preparation of yttrium oxide ceramics: The green body was held at 40℃ for 0.5 h, then at 60℃ for 8.5 h, and finally at 95℃ for 3.5 h to complete gradient drying. Next, the green body was placed in a sintering furnace under an argon protective atmosphere to begin the first stage of sintering. The green body was heated to 500℃ at a rate of 1.5℃ / min and held for 1.5 h to complete the pre-sintering treatment, obtaining a pre-sintered green body. Then, the second stage of sintering was carried out, where the pre-sintered green body was heated to 1250℃ at a rate of 6℃ / min and held for 5 h. After sintering, the pre-sintered green body formed yttrium oxide ceramics. The sintering furnace and the yttrium oxide ceramics were then cooled to room temperature, and the yttrium oxide ceramics were removed from the sintering furnace.

[0089] Example 5

[0090] Preparation of yttrium oxide powder: Yttrium nitrate and a composite sintering agent were mixed uniformly as a raw material. The raw material was then mixed uniformly with deionized water to obtain a raw material solution. This solution was then mixed with citric acid and stirred at 55°C to obtain a sol. The sol was allowed to stand for 18 hours to form a gel. Finally, the gel was calcined at 750°C for 3.5 hours to obtain yttrium oxide powder. The molar ratio of yttrium ions to citric acid in the raw material solution was 1:2.5. The composite sintering agent consisted of silicon dioxide, titanium dioxide, and zinc oxide. The content of silicon dioxide in the composite sintering agent was 30 wt%, the content of titanium dioxide was 40 wt%, and the content of zinc oxide was 30 wt%. The mass of the composite sintering agent in the mixed raw material was 5% of the mass of the yttrium oxide powder.

[0091] Preparation of the premix: A mixture of tartaric acid and polyvinylpyrrolidone (PVP) in a mass ratio of 4:1 was added to deionized water and mixed thoroughly. After obtaining the mixture, a 2.5 mol / L potassium hydroxide solution was added and mixed until the pH of the mixture reached 11.5. The addition of potassium hydroxide was then stopped, yielding the premix. The mass of the tartaric acid and PPVP mixture was 2% of the mass of the yttrium oxide powder, and the mass of the polyvinyl alcohol was 3.5% of the mass of the yttrium oxide powder.

[0092] Preparation of suspension slurry: Yttrium oxide powder and premixed liquid were mixed and stirred for 1 hour, and then vacuumed for 30 minutes to obtain suspension slurry with a solid content of 55 wt%.

[0093] Preparation of green body: A mold is installed on a porous support plate. Then, the suspension slurry is injected into the mold. The liquid in the suspension slurry is removed by vacuum filtration. The liquid flows out from the porous support plate, while the solid particles in the suspension slurry gradually accumulate in the mold to form a green body with a certain shape and strength. After demolding, the green body is obtained.

[0094] Preparation of yttrium oxide ceramics: The green body was held at 35℃ for 7 hours, then at 55℃ for 5 hours, and finally at 80℃ for 7 hours to complete gradient drying. Next, the green body was placed in a sintering furnace under an argon protective atmosphere to begin the first stage of sintering. The green body was heated to 400℃ at a rate of 0.5℃ / min and held for 4 hours to complete the pre-sintering treatment, obtaining a pre-sintered green body. Then, the second stage of sintering was carried out, where the pre-sintered green body was heated to 1450℃ at a rate of 5℃ / min and held for 3 hours. The pre-sintered green body formed yttrium oxide ceramics. The sintering furnace and yttrium oxide ceramics were then cooled to room temperature, and the yttrium oxide ceramics were removed from the sintering furnace.

[0095] Comparative Example 1

[0096] Preparation of yttrium oxide powder: Yttrium nitrate and deionized water were mixed evenly to obtain a raw material solution. Then, the raw material solution was mixed with citric acid at a molar ratio of 1:2 and stirred at 85°C to obtain a sol. After standing and aging for 5 hours, a gel was formed. Finally, the gel was calcined at 850°C for 3.5 hours to obtain yttrium oxide powder.

[0097] Preparation of the premix: A mixture of tartaric acid and polyvinylpyrrolidone in a mass ratio of 2:1 was added to deionized water and mixed thoroughly. After obtaining the mixture, a potassium hydroxide solution with a concentration of 0.8 mol / L was added and mixed until the pH of the mixture reached 10.5. Then, the addition of potassium hydroxide was stopped to obtain the premix.

[0098] Preparation of the suspension slurry: Yttrium oxide powder and silica powder were mixed evenly and placed in a ball mill jar. Deionized water and milling media were added, and the mixture was wet-milled for 24 hours to obtain a ball-milled slurry. Then, a mixture of tartaric acid and polyvinylpyrrolidone (PVP) at a mass ratio of 2:1 was added, along with polyvinyl alcohol. The mixture was stirred for 1 hour, followed by vacuum treatment for 30 minutes to obtain the suspension slurry. The mass of silica powder was 1% of the mass of yttrium oxide powder, the mass of the tartaric acid and PPVP mixture was 0.4% of the mass of yttrium oxide powder, and the mass of polyvinyl alcohol was 2% of the mass of yttrium oxide powder.

[0099] Preparation of green body: A mold is installed on a porous support plate. Then, the suspension slurry is injected into the mold. The liquid in the suspension slurry is removed by vacuum filtration. The liquid flows out from the porous support plate, while the solid particles in the suspension slurry gradually accumulate in the mold to form a green body with a certain shape and strength. After demolding, the green body is obtained.

[0100] Preparation of yttrium oxide ceramics: The green body is placed in a sintering furnace under an argon protective atmosphere and heated to 1750℃ at a rate of 5℃ / min and held for 10h. The green body has been sintered to form yttrium oxide ceramics. Then the sintering furnace and yttrium oxide ceramics are cooled to room temperature and the yttrium oxide ceramics are taken out from the sintering furnace.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 1 is that only silicon dioxide is used as the sintering agent, and when sintering the green body, the green body is directly heated to 1700°C at a rate of 4°C / min and held at that temperature for 8 hours. The green body has formed yttrium oxide ceramic after sintering. Then, the sintering furnace and the yttrium oxide ceramic are cooled to room temperature, and the yttrium oxide ceramic is taken out from the sintering furnace.

[0103] Please refer to Table 1. In one embodiment of the present invention, the density of yttrium oxide ceramics in Examples 1-5 and Comparative Examples 1-2 was tested, for example, using Archimedes' displacement method. Specifically, the yttrium oxide ceramics were dried and weighed to obtain the dried mass; then, they were immersed in distilled water and boiled or vacuumed to remove internal air bubbles, and their apparent mass when suspended in water was measured; finally, they were removed, the surface moisture was wiped off, and their saturated mass was immediately weighed. Using these three sets of mass data, the bulk density of the yttrium oxide ceramics can be calculated, and then the density can be calculated based on the ratio of the bulk density to the theoretical density of yttrium oxide. The theoretical density of yttrium oxide is 5.01 g / cm³. 3 The bulk density is calculated using the following formula:

[0104] Bulk density = Dry mass * Density of water / (Saturated mass - Apparent mass).

[0105] Please see Figures 1-3 As shown, in one embodiment of the present invention, the microstructure of yttrium oxide ceramics in Example 1 and Comparative Examples 1-2 is observed, for example, using a scanning electron microscope. (Comparison) Figures 1-3 It can be seen that the yttrium oxide grains in Example 1 are fine, uniform in structure, have low porosity and high density. In Comparative Example 1, the yttrium oxide grains are coarse, unevenly distributed, have a small number of pores and low density. The density of the yttrium oxide ceramic in Comparative Example 2 is improved compared to Comparative Example 1, but there are still a certain number of residual pores, and the grain uniformity and density are not as good as in Example 1. This shows that by adding a composite sintering agent during the preparation of yttrium oxide powder, the composite sintering agent is evenly distributed in the yttrium oxide powder and fully exerts the densification and grain refinement effects, thus it is possible to obtain yttrium oxide ceramics with high density and uniform microstructure.

[0106] Table 1. Density of yttrium oxide ceramics in Examples 1-5 and Comparative Examples 1-2

[0107] Group Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Density (%) 99.6 99.4 99.7 99.8 99.7 94.6 95.2

[0108] Please refer to Table 1. Comparing Example 1 and Comparative Example 1, it can be seen that, compared to directly mechanically mixing yttrium oxide powder with sintering agent, adding sintering agent during the preparation of yttrium oxide powder can improve the density of yttrium oxide ceramics. This indicates that adding sintering agent during the preparation of yttrium oxide powder, compared to directly mechanically mixing yttrium oxide powder with sintering agent, helps the sintering agent to be evenly distributed in the yttrium oxide powder, avoiding local enrichment or depletion of sintering agent in the yttrium oxide powder. This allows the densification behavior of each region in the green body to be synchronized during sintering, avoiding the formation of pores and abnormal growth of yttrium oxide grains in the green body, and ultimately improving the overall density, mechanical properties, and electrical properties uniformity of yttrium oxide ceramics. Furthermore, if yttrium oxide powder is directly mechanically mixed with sintering agent to prepare yttrium oxide ceramics, a higher sintering temperature is required. This indicates that by adding sintering agent during the preparation of yttrium oxide powder, the sintering temperature can be reduced, thereby significantly reducing preparation costs and energy consumption.

[0109] Please refer to Table 1. Comparing Example 1 and Comparative Example 2, it can be seen that the yttrium oxide ceramic prepared using the ZnO-TiO2-SiO2 ternary composite sintering agent has a higher density than that prepared using only silicon dioxide as a sintering agent. This indicates that, compared to a single sintering agent, the ternary composite sintering agent generates a well-wetting liquid phase at approximately 1100°C, promoting rapid interparticle diffusion and neck growth, forming a dense yttrium oxide structure, thereby significantly reducing the sintering temperature of Y2O3. Therefore, by using a ternary composite sintering agent, it is possible to achieve high density in yttrium oxide ceramics while reducing the sintering temperature.

[0110] Please refer to Table 1. Comparing Examples 1-5, it can be seen that the density of yttrium oxide ceramics can be changed by altering parameters such as the content of each component in the composite sintering agent, the pH value of the premixed liquid, the solid content in the suspension slurry, and the heating rate and temperature of the segmented sintering.

[0111] In summary, this invention proposes a yttrium oxide ceramic and its preparation method. By using a composite sintering agent, the sintering temperature of the yttrium oxide ceramic can be significantly reduced, thereby significantly reducing energy consumption and preparation costs. Simultaneously, by adding the sintering agent during the preparation of the yttrium oxide powder, uniform distribution of the sintering agent within the yttrium oxide powder can be achieved, thereby improving the density and microstructure uniformity of the yttrium oxide ceramic and inhibiting abnormal grain growth. Furthermore, gradient drying can prevent cracking of the green body during the drying process, improving the quality of the yttrium oxide ceramic.

[0112] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0113] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A method for preparing yttrium oxide ceramics, characterized in that, At least the following steps are included: Yttrium salt and composite sintering agent were mixed evenly and used as a mixed raw material to prepare yttrium oxide powder; The dispersant, binder, alkali solution and solvent are mixed evenly to obtain a premixed solution; The yttrium oxide powder and the premixed liquid are mixed evenly to obtain a suspension slurry, which is then injected into a mold. The liquid in the suspension slurry is then removed to obtain a green body. as well as The green body is subjected to gradient drying and segmented sintering to obtain yttrium oxide ceramic.

2. The preparation method according to claim 1, characterized in that, The composite sintering agent includes at least silicon dioxide, titanium dioxide, and zinc oxide.

3. The preparation method according to claim 2, characterized in that, The content of silicon dioxide in the composite sintering agent is 15wt%-45wt%, the content of titanium dioxide in the composite sintering agent is 20wt%-50wt%, and the content of zinc oxide in the composite sintering agent is 30wt%-65wt%.

4. The preparation method according to claim 1, characterized in that, The preparation of the yttrium oxide powder includes at least the following steps: The raw materials and reagents are mixed evenly to obtain a raw material solution; The raw material solution is mixed with a complexing agent, heated, and stirred to obtain a sol, which is then allowed to stand and age to form a gel; and The gel was calcined to obtain the yttrium oxide powder.

5. The preparation method according to claim 4, characterized in that, Includes one or more of the following characteristics: The complexing agent includes citric acid; The molar ratio of yttrium ions to the complexing agent in the raw material solution is 1:(1-3); The temperature for heating the raw material solution and the complexing agent is 50℃-90℃; The aging time is 5-24 hours. The gel is calcined at a temperature of 500℃-900℃; The gel is calcined for 1-10 hours.

6. The preparation method according to claim 1, characterized in that, Includes one or more of the following characteristics: The dispersant includes at least one of tartaric acid, polyvinylpyrrolidone, polyacrylic acid, and polyethylene glycol; The adhesive includes at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and polyacrylamide; The alkaline solution includes at least one of potassium hydroxide, ammonia, and lithium hydroxide. The pH value of the premixed solution is 9-12; The mass of the dispersant is 0.05%-2.5% of the mass of the yttrium oxide powder; The mass of the binder is 0.5%-4% of the mass of the yttrium oxide powder; The solid content in the suspension slurry is 20wt%-55wt%.

7. The preparation method according to claim 1, characterized in that, When the green body is gradient dried, it is first kept at a first temperature for a first time, then kept at a second temperature for a second time, and finally kept at a third temperature for a third time.

8. The preparation method according to claim 1, characterized in that, When sintering the green blank in stages, at least two-stage sintering is adopted. In the first stage of sintering the green blank, the green blank is heated to the first sintering temperature at a first heating rate and held at the temperature for a first sintering time to obtain a pre-sintered blank. Then, the process is transferred to the second stage of sintering, where the pre-sintered blank is heated to the second sintering temperature at a second heating rate and held at the temperature for a second sintering time.

9. The preparation method according to claim 8, characterized in that, Includes one or more of the following characteristics: The first heating rate is 0.1℃ / min - 2℃ / min; The first sintering temperature is 300℃-650℃; The first sintering time is 0.5h-10h; The second heating rate is 2℃ / min-8℃ / min; The second sintering temperature is 1200℃-1500℃; The second sintering time is 2h-12h.

10. A yttrium oxide ceramic, characterized in that, Obtained by the preparation method according to any one of claims 1-9.

Images