A method for preparing a zirconia toughened alumina ceramic substrate

Abstract

This invention discloses a method for preparing a zirconia-toughened alumina ceramic substrate. The method involves surface modification of alumina powder and zirconia powder using coupling agents, catalysts, and crosslinking agents. The modified powders are then mixed with rare earth sintering aids, dispersants, binders, and plasticizers, followed by ball milling. The resulting ceramic substrate is then produced through tape casting and sintering. This method is simple, easy to control, and yields a zirconia-toughened alumina ceramic substrate with a maximum flexural strength of 847 MPa and a maximum fracture toughness of 7.6 MPa·m. 1 / 2 .

Description

Technical Field

[0001] This invention belongs to the field of electronic ceramic substrate preparation, and relates to a method for preparing a zirconia-toughened alumina ceramic substrate. Background Technology

[0002] Alumina ceramic substrates are widely used in electronic integrated circuits, semiconductor packaging, and high-temperature insulation due to their excellent insulation properties, high mechanical strength, good chemical stability, and low cost. However, the inherent brittleness and relatively low fracture toughness of traditional alumina ceramics limit their application in environments requiring higher reliability and more demanding conditions.

[0003] To improve the toughness of alumina ceramics, researchers developed zirconia-toughened alumina ceramics (ZTA). Utilizing ZrO2 phase transformation toughening and microcrack toughening mechanisms, the fracture toughness and thermal shock resistance of ZTA substrates were significantly enhanced. Due to their excellent overall performance, ZTA substrates have been widely used in various industrial fields. In the field of electronics, ZTA substrates are used as substrates and packaging shells for high-power LEDs, semiconductor lasers, IGBTs, and multilayer ceramic circuits. This requires the substrate to not only possess excellent insulation and high thermal conductivity, but also sufficient mechanical strength to support and protect the precision circuitry.

[0004] However, there is a contradiction between the high performance requirements of ZTA substrates in the electronics field and the technical bottlenecks in the actual preparation process, especially the difficulty in simultaneously achieving the stability of the slurry system and the densification effect during sintering. In existing technologies, such as Chinese patent CN202110598880.7, a ZTA substrate and its preparation method are disclosed, which employs a tape casting process and mentions various possible sintering aids and solvents. However, this approach does not adequately address the dispersion of powder in organic solvent systems and does not perform surface modification of the powder, resulting in limited slurry uniformity, stability, and solid content, thus affecting the density and mechanical properties of the final ceramic substrate. The ZTA substrate disclosed in Chinese patent CN202010410660.2 uses magnesium aluminum spinel sintering aids with limited inhibitory effect on grain boundary migration, and the selected ethanol-butanone binary solvent system has insufficient wettability for the powder, easily causing uneven slurry dispersion. Therefore, despite the superior theoretical performance of ZTA, there is still room for improvement in terms of paste uniformity, sintering densification, and final mechanical properties of the ZTA substrates currently prepared.

[0005] Therefore, it is of great significance to develop a method for preparing ZTA substrates that can significantly improve powder dispersibility, thereby obtaining higher density and better mechanical properties. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention aims to provide a method for preparing a zirconia-toughened alumina ceramic substrate. The method involves surface modification of alumina powder and zirconia powder using coupling agents, catalysts, and crosslinking agents. The modified powders are then mixed with rare earth sintering aids, dispersants, binders, and plasticizers, followed by ball milling. The resulting ceramic substrate is then produced through tape casting and sintering processes. This invention offers a simple and easily controllable preparation method, achieving a maximum flexural strength of 847 MPa and a maximum fracture toughness of 7.6 MPa·m for the prepared zirconia-toughened alumina ceramic substrate. 1 / 2 .

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a zirconia-toughened alumina ceramic substrate comprises the following steps in sequence:

[0009] S1. Powder surface modification pretreatment

[0010] S11. Weigh alumina powder and zirconium oxide powder, and dry them at 100-120℃ for 2-4 h to obtain dried powder;

[0011] S12. Mix the coupling agent and solvent evenly to prepare a mixed solution with a concentration of 1-5 wt.%, then add the catalyst to it, stir evenly to obtain a surface modification solution, and prepare two parallel portions of the solution.

[0012] S13. Place the dried alumina powder and zirconium oxide powder into two sets of reflux devices respectively, add a portion of surface modification solution and crosslinking agent to each device, and carry out reflux stirring reaction. After the reaction is completed, filter and wash the powder, and vacuum dry at 80-100℃ for 6-12 h to obtain surface modified inorganic powder.

[0013] S2, Ingredient preparation and sintering

[0014] S21. After uniformly mixing the surface-modified alumina powder and the surface-modified zirconium oxide powder with the rare earth sintering aid, a mixed powder is obtained.

[0015] S22. Add the mixed powder, anhydrous ethanol, and triethyl phosphate to a planetary ball mill and ball mill at 150-300 r / min for 24-48 h. After the milling is completed, add polyvinyl butyral and dioctyl phthalate and ball mill at 150-300 r / min for 12-24 h to obtain the cast slurry.

[0016] S23. The casting slurry is cast into shape, dried at 40°C for 1 h, and then sintered to obtain a zirconia toughened alumina ceramic substrate.

[0017] As a limitation of the present invention, in step S12, the coupling agent is one or more of isopropyltris(isostearoyl)titanate, γ-aminopropyltriethoxysilane, and distearyloxyisopropoxyaluminate, and the catalyst is one or more of aluminum acetylacetonate, tetraisopropyl titanate, and glacial acetic acid.

[0018] As another limitation of the present invention, in step S12, the mass ratio of the coupling agent to the dry powder is (0.5-3):100; the mass of the catalyst added is 0.1-1 wt. of the mass of the coupling agent.

[0019] As a third limitation of the present invention, in step S12, the solvent is a mixed solvent composed of anhydrous ethanol and propylene glycol methyl ether, and the volume ratio of anhydrous ethanol to propylene glycol methyl ether is 4:1.

[0020] The present invention uses a mixed solvent because it takes advantage of the high solubility of ethanol and the high boiling point of propylene glycol methyl ether. This ensures that the coupling agent is fully dissolved and dispersed, while preventing boiling up during the reflux reaction. If only anhydrous ethanol is used as a solvent, the solution boiling point will be too low, resulting in violent boiling at the reflux temperature and causing boiling up. In addition, the solubility of long-chain coupling agents is insufficient, and the surface modification is uneven. If only propylene glycol methyl ether is used as a solvent, the solvent cost will be too high, the viscosity will be high, the wetting and penetration speed of the powder will be slow, and the subsequent drying will be difficult.

[0021] As a fourth limitation of the present invention, in step S13, the crosslinking agent is magnesium acetate or zinc acetate, and the mass of the crosslinking agent added is 0.5-2 wt. of the mass of the dried powder.

[0022] As a fifth limitation of the present invention, in step S13, the reflux stirring reaction is carried out according to the following procedure:

[0023] (a) In the first reaction stage, the mixture was refluxed and stirred at 60-80℃ for 1 h;

[0024] (b) Second reaction stage: reflux and stir at 90-110°C for 2 h.

[0025] This invention employs a staged reflux technique to optimize coupling reaction kinetics, thereby ensuring the formation of a complete and robust surface-modified layer. Specifically, the lower temperature in the first stage facilitates sufficient wetting and physical adsorption of coupling agent molecules on the powder surface, while the higher temperature in the subsequent second stage provides sufficient activation energy to drive a complete chemical condensation reaction. This results in a more robust and uniform coating layer at the molecular scale, significantly improving the powder's dispersibility and compatibility with the organic phase in subsequent slurries. Using only a one-stage reflux reaction would lead to insufficient hydrolysis and grafting of the coupling agent, resulting in uneven surface coating and unstable modification effects.

[0026] As a sixth limitation of the present invention, in step S21, the mass ratio of the surface-modified alumina powder to the surface-modified zirconium oxide powder and rare earth sintering aid is 100:(5-40):(1-2).

[0027] In this invention, the mass ratio of surface-modified alumina powder to zirconia powder and rare earth sintering aids affects the toughening effect, sintering density, and mechanical properties of the final ceramic substrate. When the mass ratio is within this range, the phase transformation toughening effect of zirconia and the densification-promoting effect of rare earth sintering aids are optimized, thereby significantly improving the toughening effect of the ceramic substrate, achieving an ideal sintering density, and achieving an optimal balance of key performance indicators such as hardness, flexural strength, and toughness. If the mass ratio is less than this range, the toughening effect will be insufficient, and the strength and toughness of the sintered body will decrease. If the mass ratio is greater than this range, the content of the main phase alumina will be relatively insufficient, the hardness and thermal conductivity of the substrate will decrease, and cracks will be easily induced.

[0028] As a seventh limitation of the present invention, in step S21, the rare earth sintering aid is one or more of yttrium oxide, cerium oxide, erbium oxide, and europium oxide.

[0029] As an eighth limitation of the present invention, in step S22, the mass ratio of the surface-modified alumina powder to anhydrous ethanol, triethyl phosphate, polyvinyl butyral, and dioctyl phthalate is 100:(30-50):(0.5-3):(4-8):(2-6).

[0030] As a ninth limitation of the present invention, in step S23, the sintering stage is performed according to the following procedure:

[0031] (c) In the first heating stage, the temperature is increased from room temperature to 400-600℃ at a heating rate of 0.5-2℃ / min, and held for 1-2 hours;

[0032] (d) In the second heating stage, the temperature is increased from 400-600℃ to 1450-1500℃ at a heating rate of 3-5℃ / min, and held for 2-3 hours.

[0033] (e) Cooling stage: The furnace is cooled to room temperature.

[0034] The sintering process of this invention employs segmented heating because it is necessary to control the kinetics of organic matter removal and ceramic grain growth to prevent defects. In the first heating stage, the temperature is increased from room temperature to 400-600℃ at a heating rate of 0.5-2℃ / min. This allows organic matter such as binders and plasticizers in the cast green body to slowly and fully decompose and be removed. If the temperature is below 400℃ in this stage, organic matter residue will remain, leading to carbide contamination; if the temperature is above 600℃, the organic matter will decompose violently, resulting in internal cracks and pores. Holding the temperature for 1-2 hours ensures that the organic matter inside the green body is completely decomposed and removed. In the second heating stage, the temperature is increased from 400-600℃ to 1450-1500℃ at a heating rate of 3-5℃ / min. During this stage, the ceramic powder undergoes rapid densification and grain growth. If the temperature is below 1450℃, the sintering density will be insufficient and the substrate strength will be low. If the temperature is above 1500℃, abnormal grain growth will occur, reducing the toughness and reliability of the material. Holding the temperature for 2-3 hours is to obtain a uniform microstructure and a stable phase composition, ensuring uniform material properties.

[0035] This invention employs a mixed solvent system composed of anhydrous ethanol and propylene glycol methyl ether, which enhances the mass transfer and wetting properties of the solution during reflux stirring. The introduction of propylene glycol methyl ether can increase the azeotropic point and enhance the spreading ability on the powder surface, thereby providing a more stable reaction environment under reflux conditions and avoiding the problem of uneven reaction caused by the boiling point limitation of a single solvent. Metal acetates, acting as crosslinking agents, play a crucial role by using their cations to coordinate with the oxygen-containing functional groups (such as phosphate esters and alkoxy groups) at the ends of coupling agent molecules and the hydroxyl groups on the surface of alumina powder to form a molecular-scale crosslinking network. This network bridges and fixes the arrangement of coupling agent molecules on the alumina particle surface, ensuring uniform distribution and dense arrangement, fundamentally preventing particle agglomeration. Furthermore, it acts as a positioning beacon, guiding the active centers of the catalyst (such as alkoxy, acetylacetone, and carboxyl groups) to form stable coordination intermediates with the coupling agent, crosslinking agent, and hydroxyl groups on the powder surface. This significantly reduces the activation energy of the coupling reaction and guides the reaction pathway towards directional and ordered bonding. This results in faster and more thorough chemical bonding, ultimately leading to excellent dispersion stability, high filling rate, and strong interfacial bonding with organic binders in the subsequent casting and sintering processes of the surface-modified powder. Ultimately, this process ensures the formation of a uniform, dense, and firmly bonded hybrid coating layer with the core particles, which is key to achieving high-performance composite materials. Without such ionic cross-linking, the reaction will tend to be random and agglomerated, resulting in uneven coating and weak interfaces.

[0036] The above-mentioned technical solution of the present invention is a whole in which each step is closely related and mutually influential, and together they determine the morphological characteristics and performance of the product.

[0037] The above technical solution has the following advantages or beneficial effects:

[0038] 1. This invention constructs an efficient and stable powder surface modification system, which, with the compatibility of rare earth sintering aids, can effectively suppress abnormal grain boundary movement, reduce residual porosity, and promote the full play of the zirconia phase transformation toughening effect in the subsequent sintering stage, ultimately greatly improving the mechanical properties of the ceramic substrate.

[0039] 2. The zirconia-toughened alumina ceramic substrate prepared by this invention can achieve a maximum flexural strength of 847 MPa and a maximum fracture toughness of 7.6 MPa·m. 1 / 2 ;

[0040] 3. The preparation method of this invention is simple, the process is easy to control, and it is suitable for large-scale industrial production.

[0041] This invention is applicable to the preparation of zirconia-toughened alumina ceramic substrates.

[0042] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0043] Figure 1 The image shows the fracture surface SEM image of the zirconia-toughened alumina ceramic substrate prepared in Example 1 of this invention.

[0044] Figure 2 This is a SEM image of the fracture surface of the zirconia-toughened alumina ceramic substrate prepared in Comparative Example 5 of the present invention.

[0045] Figure 3 This is a SEM image of the fracture surface of the zirconia-toughened alumina ceramic substrate prepared in Comparative Example 7 of the present invention. Detailed Implementation

[0046] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0047] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0048] Example 1

[0049] This embodiment prepares a zirconia-toughened alumina ceramic substrate, and the preparation process and steps are as follows:

[0050] S1. Powder surface modification pretreatment

[0051] S11. Weigh alumina powder and zirconium oxide powder, and dry them at 100℃ for 3 h to obtain dried powder;

[0052] S12. Mix 1.5 g of isopropyltris(isostearoyl) titanate with 60 mL of solvent (composed of anhydrous ethanol and propylene glycol methyl ether in a volume ratio of 4:1) to prepare a mixed solution with a concentration of 3 wt.%. Then add 7.5 mg of aluminum acetylacetonate to the solution and stir until homogeneous to obtain a surface-modified solution. Prepare two parallel portions of this solution.

[0053] S13, (1) Surface modification of alumina powder

[0054] 100 g of dried alumina powder and 1.5 g of magnesium acetate were added to a surface modification solution, and the solution was refluxed and stirred at 80 °C for 1 h, and then refluxed and stirred at 90 °C for 2 h. After the reaction was completed, the solution was filtered, washed, and vacuum dried at 90 °C for 8 h to obtain surface modified alumina powder.

[0055] (2) Surface modification of zirconia powder

[0056] Add 100 g of dried zirconia powder and 1.5 g of magnesium acetate to another part of the surface modification solution, and reflux and stir at 80 °C for 1 h, then reflux and stir at 90 °C for 2 h. After the reaction is completed, filter and wash the solution, and vacuum dry it at 90 °C for 8 h to obtain surface-modified zirconia powder.

[0057] S2, Ingredient preparation and sintering

[0058] S21. Mix 100 g of surface-modified alumina powder and 10 g of surface-modified zirconium oxide powder with 1.5 g of yttrium oxide to obtain a mixed powder.

[0059] S22. The mixed powder, 30 g of anhydrous ethanol, and 0.5 g of triethyl phosphate were added to a planetary ball mill and ball milled at 150 r / min for 24 h. After the milling was completed, 4 g of polyvinyl butyral and 2 g of dioctyl phthalate were added and ball milled at 150 r / min for 12 h. The slurry was then subjected to vacuum degassing to obtain a casting slurry with a viscosity of 7000 mPa·s.

[0060] S23. After the cast slurry is cast and shaped, it is dried at 40℃ for 1 h and then sintered. The sintering process adopts segmented sintering. First, the temperature is raised from room temperature to 400℃ at a heating rate of 0.5℃ / min and held for 1 h. Then, the temperature is raised from 400℃ to 1450℃ at a heating rate of 3℃ / min and held for 2 h. Finally, it is cooled to room temperature with the furnace to obtain a zirconia toughened alumina ceramic substrate.

[0061] Example 2

[0062] This embodiment prepares a zirconia-toughened alumina ceramic substrate, and the preparation process and steps are as follows:

[0063] S1. Powder surface modification pretreatment

[0064] S11. Weigh alumina powder and zirconium oxide powder, and dry them at 110℃ for 2 h to obtain dried powder;

[0065] S12. Mix 0.5 g of γ-aminopropyltriethoxysilane with 61 mL of solvent (composed of anhydrous ethanol and propylene glycol methyl ether in a volume ratio of 4:1) to prepare a mixed solution with a concentration of 1 wt.%. Then add 0.5 mg of tetraisopropyl titanate to the solution and stir until homogeneous to obtain a surface-modified solution. Prepare two parallel portions of this solution.

[0066] S13, (1) Surface modification of alumina powder

[0067] 100 g of dried alumina powder and 0.5 g of zinc acetate were added to a surface modification solution, and the solution was refluxed and stirred at 70 °C for 1 h, and then refluxed and stirred at 110 °C for 2 h. After the reaction was completed, the solution was filtered, washed, and vacuum dried at 80 °C for 12 h to obtain surface modified alumina powder.

[0068] (2) Surface modification of zirconia powder

[0069] Add 100 g of dried zirconia powder and 1.5 g of zinc acetate to another part of the surface modification solution, and reflux and stir at 70 °C for 1 h, then reflux and stir at 110 °C for 2 h. After the reaction is completed, filter and wash the solution, and vacuum dry it at 80 °C for 12 h to obtain surface-modified zirconia powder.

[0070] S2, Ingredient preparation and sintering

[0071] S21. Mix 100 g of surface-modified alumina powder and 5 g of surface-modified zirconium oxide powder with 1 g of erbium oxide to obtain a mixed powder.

[0072] S22. The mixed powder, 40 g of anhydrous ethanol, and 2 g of triethyl phosphate were added to a planetary ball mill and ball milled at 230 r / min for 32 h. After the end of the milling, 6 g of polyvinyl butyral and 4 g of dioctyl phthalate were added and ball milled at 230 r / min for 18 h. The slurry was then subjected to vacuum degassing to obtain a casting slurry with a viscosity of 6000 mPa·s.

[0073] S23. After the cast slurry is cast and shaped, it is dried at 40℃ for 1 h and then sintered. The sintering process adopts segmented sintering. First, the temperature is raised from room temperature to 500℃ at a heating rate of 1℃ / min and held for 1.5 h. Then, the temperature is raised from 500℃ to 1500℃ at a heating rate of 4℃ / min and held for 2.5 h. Finally, it is cooled to room temperature with the furnace to obtain a zirconia toughened alumina ceramic substrate.

[0074] Example 3

[0075] This embodiment prepares a zirconia-toughened alumina ceramic substrate, and the preparation process and steps are as follows:

[0076] S1. Powder surface modification pretreatment

[0077] S11. Weigh alumina powder and zirconium oxide powder, and dry them at 120℃ for 4 h to obtain dried powder;

[0078] S12. Mix 3 g of distearyloxyisopropoxyaluminate with 70 mL of solvent (composed of anhydrous ethanol and propylene glycol methyl ether in a volume ratio of 4:1) to prepare a mixed solution with a concentration of 5 wt.%. Then add 30 mg of tetraisopropyl titanate to the solution and stir until homogeneous to obtain a surface-modified solution. Prepare two parallel portions of this solution.

[0079] S13, (1) Surface modification of alumina powder

[0080] 100 g of dried alumina powder and 2 g of zinc acetate were added to a surface modification solution, and the solution was refluxed and stirred at 60 °C for 1 h, and then refluxed and stirred at 100 °C for 2 h. After the reaction was completed, the solution was filtered, washed, and vacuum dried at 100 °C for 6 h to obtain surface modified alumina powder.

[0081] (2) Surface modification of zirconia powder

[0082] Add 100 g of dried zirconia powder and 2 g of zinc acetate to another part of the surface modification solution, and reflux and stir at 60 °C for 1 h, then reflux and stir at 100 °C for 2 h. After the reaction is completed, filter and wash the solution, and vacuum dry it at 100 °C for 6 h to obtain surface modified zirconia powder.

[0083] S2, Ingredient preparation and sintering

[0084] S21. Mix 100 g of surface-modified alumina powder and 40 g of surface-modified zirconium oxide powder with 2 g of cerium oxide to obtain a mixed powder.

[0085] S22. The mixed powder, 50 g of anhydrous ethanol, and 3 g of triethyl phosphate were added to a planetary ball mill and ball milled at 300 r / min for 48 h. After the end of the milling, 8 g of polyvinyl butyral and 6 g of dioctyl phthalate were added and ball milled at 300 r / min for 24 h. The slurry was then subjected to vacuum degassing to obtain a casting slurry with a viscosity of 6500 mPa·s.

[0086] S23. After the cast slurry is cast and shaped, it is dried at 40℃ for 1 h and then sintered. The sintering process adopts segmented sintering. First, the temperature is raised from room temperature to 600℃ at a heating rate of 2℃ / min and held for 2 h. Then, the temperature is raised from 600℃ to 1480℃ at a heating rate of 5℃ / min and held for 3 h. Finally, it is cooled to room temperature with the furnace to obtain a zirconia toughened alumina ceramic substrate.

[0087] Comparative Example

[0088] To investigate the influence of different raw materials on the performance of the product during the preparation process of this invention, the following comparative experiments were conducted. Different zirconia-toughened alumina ceramic substrates were prepared according to the following comparative examples:

[0089] Comparative Example 1

[0090] This comparative example prepares a zirconia-toughened alumina ceramic substrate. The preparation process is similar to that of Example 1, except that step S1 is not performed, that is, the alumina powder and zirconia powder are not modified.

[0091] Comparative Example 2

[0092] This comparative example prepares a zirconia-toughened alumina ceramic substrate. The preparation process is similar to that of Example 1, except that in step S12, the solvent is replaced with single anhydrous ethanol.

[0093] Comparative Example 3

[0094] This comparative example prepares a zirconia-toughened alumina ceramic substrate. The preparation process is similar to that of Example 1, except that magnesium acetate is not added when modifying the alumina powder and zirconia powder in step S13.

[0095] Comparative Example 4

[0096] This comparative example prepares a zirconia-toughened alumina ceramic substrate. The preparation process is similar to that of Example 1, except that aluminum acetylacetone is not added when preparing the surface modification solution in step S12.

[0097] Comparative Example 5

[0098] This comparative example prepares a zirconia-toughened alumina ceramic substrate. The preparation process is similar to that of Example 1, except that in step S12, isopropyltris(isostearoyl) titanate is not added when preparing the surface modification solution.

[0099] Comparative Example 6

[0100] This comparative example prepares a zirconia-toughened alumina ceramic substrate. The preparation process is similar to that of Example 1, except that in step S13, when performing the reflux reaction, a one-stage reflux is used instead of a two-stage reflux, that is, the reflux reaction is carried out at 90°C for 3 h.

[0101] Comparative Example 7

[0102] This comparative example prepares a zirconia-toughened alumina ceramic substrate. The preparation process is similar to that of Example 1, except that in step S23, the sintering reaction is not carried out in stages, but is directly heated from room temperature to 1450℃ at a heating rate of 1.5℃ / min and held for 2 h.

[0103] Performance testing

[0104] The zirconia-toughened alumina ceramic substrates prepared in Examples 1-3 and Comparative Examples 1-7 of the present invention were subjected to a series of tests, as follows:

[0105] like Figure 1 The image shows a SEM image of the fracture surface of the zirconia-toughened alumina ceramic substrate prepared in Example 1 of this invention. As can be seen from the image, the structure is dense and uniform with uniform grains, and the fracture surface is transgranular. This is attributed to the surface modification system and segmented sintering process of this invention, which together ensure excellent mechanical properties.

[0106] like Figure 2 The image shows a fracture surface SEM image of the zirconia-toughened alumina ceramic substrate prepared in Comparative Example 5 of this invention. As can be seen from the image, there is obvious agglomeration at the fracture surface of the ceramic substrate, the porosity is high, and the fracture mode is mainly intergranular fracture. This is because no coupling agent was added in Comparative Example 5, resulting in extremely weak interfacial bonding within the ceramic substrate and an increase in the number of defects. Ultimately, the flexural strength and fracture toughness of this ceramic substrate are the lowest among all tested samples.

[0107] like Figure 3The image shows a fracture surface SEM image of the zirconia-toughened alumina ceramic substrate prepared in Comparative Example 7 of this invention. As can be seen from the image, the fracture surface of the ceramic substrate exhibits characteristics of uneven grain size and high porosity. This is because Comparative Example 7 uses a one-step sintering process, which leads to uncontrolled decomposition of organic matter and grain growth, resulting in an increase in internal defects of the substrate and ultimately a significant decrease in its strength and toughness.

[0108] The mechanical properties of the zirconia-toughened alumina ceramic substrates prepared in Examples 1-3 and Comparative Examples 1-7 of this invention were tested, and the specific test results are shown in Table 1.

[0109] Table 1. Mechanical property test results of ceramic substrates prepared in Examples 1-3 and Comparative Examples 1-7

[0110]

[0111] As shown in the test results above, the zirconia-toughened alumina ceramic substrates prepared in Examples 1-3 of this invention exhibit superior flexural strength and fracture toughness compared to all comparative examples 1-7. This is because this invention constructs an efficient surface modification system by mixing solvents, catalysts, coupling agents, and crosslinking agents. Combined with optimized staged reflow and sintering processes, a uniform, dense, and chemically bonded coating layer is formed on the surface of inorganic powders. This significantly improves the dispersion and green uniformity of the powders in the organic phase and effectively inhibits abnormal grain boundary migration during sintering, promoting the full realization of densification and the toughening effect of zirconia phase transformation.

[0112] Each comparative example, due to not adopting the complete technical solution of this invention, has specific defects leading to performance degradation: Comparative Example 1 did not modify the powder, resulting in poor compatibility and uneven dispersion between the powder and the organic binder, making the sintered body prone to agglomeration defects and weak interfaces; Comparative Example 2 used only anhydrous ethanol as a solvent, leading to insufficient dissolution of the coupling agent and a tendency for the reaction system to boil over, resulting in uneven surface modification and a non-dense coating layer; Comparative Example 3 did not add magnesium acetate crosslinking agent, resulting in disordered arrangement of coupling agent molecules and an inability to form a stable crosslinking network, leading to a loose coating layer that is easily detached; Comparative Example 4 did not add aluminum acetylacetone catalyst, resulting in… The coupling reaction has a high activation energy, slow and incomplete reaction rate, and low degree of chemical bonding on the powder surface; Comparative Example 5 did not add isopropyltris(isostearoyl) titanate coupling agent, and there was a lack of effective chemical bridging between the inorganic powder and the organic phase, resulting in weak interfacial bonding, high porosity and many defects; Comparative Example 6 did not use a staged reflux reaction, and the physical adsorption and chemical bonding process of the coupling agent could not be optimized, resulting in insufficient uniformity and density of the coating layer; Comparative Example 7 used a one-step sintering process, which resulted in incomplete decomposition of organic matter, internal stress concentration and uncontrolled grain growth, introducing defects such as microcracks and pores.

[0113] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method of making a zirconia toughened alumina ceramic substrate, characterized by, Follow these steps in sequence: S1. Powder surface modification pretreatment S11. Weigh alumina powder and zirconium oxide powder, and dry them at 100-120℃ for 2-4 h to obtain dried powder; S12. Mix the coupling agent and solvent evenly to prepare a mixed solution with a concentration of 1-5 wt.%, then add the catalyst to it, stir evenly to obtain a surface modification solution, and prepare two parallel portions of the solution. The coupling agent is one or more of isopropyltris(isostearoyl)titanate, γ-aminopropyltriethoxysilane, and distearyloxyisopropoxyaluminate, and the catalyst is one or more of aluminum acetylacetonate, tetraisopropyl titanate, and glacial acetic acid. S13. Place the dried alumina powder and zirconium oxide powder into two sets of reflux devices respectively, add a portion of surface modification solution and crosslinking agent to each device, and carry out reflux stirring reaction. After the reaction is completed, filter and wash the powder, and vacuum dry it at 80-100℃ for 6-12 h to obtain surface modified inorganic powder. The crosslinking agent is magnesium acetate or zinc acetate, and the mass of the crosslinking agent added is 0.5-2 wt.% of the mass of the dried powder. S2, Ingredient preparation and sintering S21. After uniformly mixing the surface-modified alumina powder and the surface-modified zirconium oxide powder with the rare earth sintering aid, a mixed powder is obtained. S22. Add the mixed powder, anhydrous ethanol, and triethyl phosphate to a planetary ball mill and ball mill at 150-300 r / min for 24-48 h. After the milling is completed, add polyvinyl butyral and dioctyl phthalate and ball mill at 150-300 r / min for 12-24 h to obtain the cast slurry. S23. The casting slurry is cast into shape, dried at 40°C for 1 h, and then sintered to obtain a zirconia toughened alumina ceramic substrate.

2. The method for preparing a zirconia-toughened alumina ceramic substrate according to claim 1, characterized in that, In step S12, the mass ratio of the coupling agent to the dry powder is (0.5-3):100; the mass of the catalyst added is 0.1-1 wt.% of the mass of the coupling agent.

3. The method for preparing a zirconia-toughened alumina ceramic substrate according to claim 1, characterized in that, In step S12, the solvent is a mixed solvent composed of anhydrous ethanol and propylene glycol methyl ether, with a volume ratio of anhydrous ethanol to propylene glycol methyl ether of 4:

1.

4. The method for preparing a zirconia-toughened alumina ceramic substrate according to claim 1, characterized in that, In step S13, the reflux stirring reaction is carried out according to the following procedure: (a) In the first reaction stage, the mixture was refluxed and stirred at 60-80℃ for 1 h; (b) Second reaction stage: reflux and stir at 90-110°C for 2 h.

5. The method for preparing a zirconia-toughened alumina ceramic substrate according to claim 1, characterized in that, In step S21, the mass ratio of the surface-modified alumina powder to the surface-modified zirconium oxide powder and rare earth sintering aid is 100:(5-40):(1-2).

6. The method for preparing a zirconia-toughened alumina ceramic substrate according to claim 1, characterized in that, In step S21, the rare earth sintering aid is one or more of yttrium oxide, cerium oxide, erbium oxide, and europium oxide.

7. The method for preparing a zirconia-toughened alumina ceramic substrate according to claim 1, characterized in that, In step S22, the mass ratio of the surface-modified alumina powder to anhydrous ethanol, triethyl phosphate, polyvinyl butyral, and dioctyl phthalate is 100:(30-50):(0.5-3):(4-8):(2-6).

8. The method for preparing a zirconia-toughened alumina ceramic substrate according to claim 1, characterized in that, In step S23, the sintering stage is performed according to the following procedure: (c) In the first heating stage, the temperature is increased from room temperature to 400-600℃ at a heating rate of 0.5-2℃ / min, and held for 1-2 hours; (d) In the second heating stage, the temperature is increased from 400-600℃ to 1450-1500℃ at a heating rate of 3-5℃ / min, and held for 2-3 hours. (e) Cooling stage: The furnace is cooled to room temperature.

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