High-bending-strength aluminum nitride ceramic sintered body and method for producing the same

Abstract

The application discloses a high-bending-strength aluminum nitride ceramic sintered body and a preparation method thereof, relates to the technical field of ceramic materials, and solves the technical problem of low bending strength of existing AlN ceramic materials; the method comprises the following steps: ball milling aluminum nitride powder, a sintering aid, an additive and a solvent to obtain mixed slurry; and the mixed slurry is subjected to defoaming, flow casting, degreasing and sintering to obtain the high-bending-strength aluminum nitride ceramic sintered body; wherein the sintering aid is a Y2O3-Ca(Y-Sm)O3 perovskite type composite oxide, the sintering aid is obtained by adding Sm2O3 and Ca(OH)2 into YCl3 solution, and co-precipitating in an alkaline environment at 70-90 DEG C and then calcining; by adopting the method, the bending strength and thermal conductivity of the material can be effectively improved, the bending strength of the prepared aluminum nitride ceramic sintered body can reach 631 MPa, and the thermal conductivity can reach 211.7 W / m.K.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a high-flexural-strength aluminum nitride ceramic sintered body and its preparation method. Background Technology

[0002] Aluminum nitride (AlN) ceramics, due to their outstanding performance characteristics—high resistivity, excellent thermal conductivity, significant dielectric constant, and a thermal expansion coefficient highly matched with silicon—have become a recognized ideal substrate material choice in the field of electronic packaging. In packaging applications for high-end functional devices such as insulated-gate bipolar transistors (IGBTs), 5G communication RF components, and high-power LEDs, AlN ceramics demonstrate enormous application potential, providing a solid material foundation for the development of modern electronic technology. Furthermore, the high hardness, wear resistance, corrosion resistance, high thermal conductivity, and strength of aluminum nitride ceramics make them ideal materials for manufacturing special ceramic products such as ceramic valves and ceramic cylinder valve plates. Simultaneously, aluminum nitride ceramics are non-toxic, high-purity, and possess good chemical stability, making them a high-performance, green, and special refractory ceramic with broad application prospects in high-temperature refractory components, electronic packaging, semiconductor manufacturing, and optical devices.

[0003] Despite its superior properties, aluminum nitride (AlN) is a strongly covalent compound with a high melting point, making sintering difficult. Its oxidative affinity also contributes to performance degradation, resulting in a flexural strength typically only around 300 MPa. This inherent brittleness and low mechanical strength limit its applications as a ceramic material. In high-temperature, high-frequency, or high-stress environments (aerospace equipment, nuclear power equipment), materials require both high thermal conductivity and resistance to mechanical fatigue. The fabrication of complex-shaped electronic components also necessitates higher fracture toughness in AlN materials. However, the relatively low fracture toughness of AlN ceramics further complicates processing, easily leading to brittle removal. This phenomenon not only reduces processing efficiency but can also leave microcracks and other defects on the surface and subsurface of the ceramic, severely impacting its mechanical properties and reliability. Therefore, enhancing the flexural strength of AlN ceramics not only effectively ensures the production of AlN ceramic substrates with high integrity and excellent performance during the fabrication stage but also has a significant and far-reaching positive impact on the actual performance of AlN ceramics in a wide range of applications. This is crucial for improving the performance and reliability of electronic packaging devices and promoting the further development of electronic technology.

[0004] Based on this, the present invention provides a high-bending-strength aluminum nitride ceramic sintered body and its preparation method to improve the bending strength of AlN ceramic materials. Summary of the Invention

[0005] The present invention aims to solve the technical problem of low flexural strength of existing AlN ceramic materials. The purpose is to provide a high flexural strength aluminum nitride ceramic sintered body and its preparation method, which can effectively improve the flexural strength and thermal conductivity of the material. The flexural strength of the prepared aluminum nitride ceramic sintered body can reach 631 MPa, while the thermal conductivity reaches 211.7 W / m•K.

[0006] This invention is achieved through the following technical solution:

[0007] The first objective of this invention is to provide a method for preparing a high-flexural-strength aluminum nitride ceramic sintered body, comprising the following steps:

[0008] Aluminum nitride powder, sintering aid, additives and solvent are ball-milled to obtain a mixed slurry;

[0009] The mixed slurry was degassed, cast, degreased, and sintered to obtain a high-flexural-strength aluminum nitride ceramic sintered body.

[0010] The sintering aid is a Y2O3-Ca(Y-Sm)O3 perovskite-type composite oxide, which is obtained by adding Sm2O3 and Ca(OH)2 to a YCl3 solution, co-precipitating them in an alkaline environment at 70-90℃, and then calcining them.

[0011] This invention obtains a Y-Sm-Ca ternary composite hydroxide precipitate by co-precipitation of Sm2O3 and Ca(OH)2 in a YCl3 solution. After the reaction, the precipitate is calcined to obtain a composite sintering aid material. The invention innovatively proposes using the Y2O3-Ca(Y-Sm)O3 composite oxide material as a sintering aid for aluminum nitride ceramic sintering bodies. Using the sintering aid of this invention can reduce the thermal resistance phase at grain boundaries. In the early stage of sintering, Y2O3 and Ca(Y-Sm)O3 react with Al2O3 on the AlN surface to generate Y3Al5O3. 12 Low-melting-point aluminate liquid phases such as CaAl2O4 wet AlN particles, promoting particle rearrangement through a dissolution-precipitation mechanism, further reducing liquid phase viscosity, and accelerating mass transfer. The liquid phase of Ca(Y-Sm)O3 can completely wet AlN particles during the mid-sintering stage (1500-1650℃), promoting rapid rearrangement and pore removal. However, existing technologies using a ternary mixed system of Y2O3, Sm2O3, and CaO suffer from delayed liquid phase formation, with densification mainly concentrated at high temperatures, easily leading to abnormal grain growth. Therefore, using Y2O3-Ca(Y-Sm)O3 perovskite-type composite oxides as sintering aids is beneficial for improving the fracture toughness and flexural strength of AlN materials.

[0012] During sintering, Y2O3 forms Y4Al2O9 (YAM). YAM crystals hinder the migration of yttrium oxide particles and inhibit the growth of aluminum nitride ceramic particles. After the reaction is complete, it can react with aluminum oxide on the surface of aluminum nitride to form compounds such as yttrium aluminum garnet (YAG, which is the final reactant of YAM). YAG fills the pores in the liquid phase and promotes particle rearrangement, significantly improving the densification rate; and forms strong bonds at the grain boundaries, inhibiting crack propagation and improving fracture toughness.

[0013] In Ca(Y-Sm)O3, Ca reacts with the alumina on the surface of aluminum nitride to form calcium aluminate, promoting liquid-phase sintering and lowering the sintering temperature. Furthermore, calcium aluminate improves the toughness and thermal shock resistance of ceramics. Meanwhile, Sm forms samarium aluminates (such as SmAlO3) or other complex samarium aluminate compounds during sintering, promoting densification. These compounds form a liquid phase at high temperatures, further promoting densification, optimizing the grain boundary structure, controlling grain boundary segregation, and ultimately improving the thermal conductivity and flexural strength of the ceramic.

[0014] Therefore, this invention uses Y2O3-Ca(Y-Sm)O3 composite material as a sintering aid for aluminum nitride ceramic sintering body, so that the AlN grain size is uniformly distributed in 3-5μm, optimizes phonon scattering, and can effectively improve the bending resistance and thermal conductivity of the material.

[0015] Furthermore, a co-precipitation method was used to prepare the sintering aid composite material. A YCl3 solution was prepared using ultrapure water. After stirring continuously for 5 minutes in a water bath at 70-90℃ (preferably 80℃), Sm2O3 and Ca(OH)2 were added. The stirring speed was set to 300 rpm. 20% ammonia water was used to adjust the pH value of the reaction to keep it within the range of 11-13. After reacting for 1 hour, the mixture was allowed to stand for 4 hours and then filtered for later use.

[0016] Furthermore, the Y-Sm-Ca ternary composite hydroxide precipitate is placed in a muffle furnace and calcined under a nitrogen atmosphere at a temperature of 750-850℃ (preferably 800℃) for 2-4 hours to obtain the Y2O3-Ca(Y-Sm)O3 composite material.

[0017] Furthermore, in the sintering aids, the molar mass of YCl3 > the molar mass of Ca(OH)2 > the molar mass of Sm2O3. Since the amount of YCl3 added is greater than that of Ca(OH)2 and Sm2O3, a two-phase coexistence region of Y2O3 + perovskite exists after calcination, where Ca(Y-Sm)O3 is a single-phase composite oxide, and Y... 3+ 、Sm 3+ Ca 2+The YCl3 particles are uniformly distributed within the crystal lattice, allowing for rapid formation of a homogeneous liquid phase during sintering without the need for additional diffusion. In contrast, existing ternary mixed systems require the individual dissolution of Y2O3, Sm2O3, and CaO particles before they react to form a liquid phase, a process that is slow and prone to localized segregation due to uneven diffusion. Preferably, the addition amounts of YCl3 are 120–1200 mmol / L, Ca(OH)2 is 500–1000 mmol / L, and Sm2O3 is 10–50 mmol / L.

[0018] Furthermore, the amount of sintering aid added is 1-5 wt% of aluminum nitride powder. Specifically, the amount of sintering aid added is 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt% of aluminum nitride powder. When the amount of sintering aid added exceeds 5 wt% of aluminum nitride powder, it is not conducive to cost control due to the presence of rare earth elements. When the amount of sintering aid added is less than 1 wt% of aluminum nitride powder, the flexural strength of the aluminum nitride ceramic material may be significantly reduced. Preferably, the amount of sintering aid added is 3-5 wt% of aluminum nitride powder.

[0019] Furthermore, the additives include a dispersant, a binder, and a plasticizer, with addition amounts of 1.5~3.5wt%, 7~14wt%, and 3~10wt% of the aluminum nitride powder, respectively. The dispersant is oleic acid, the binder is polyvinyl butyral, and the plasticizer is dibutyl phthalate.

[0020] Furthermore, the solvent is a mixture of anhydrous ethanol and isopropanol, and the amount added is 40-45 wt% of aluminum nitride powder, wherein the aqueous ethanol and isopropanol are mixed in a weight percentage ratio of 1.2:1.

[0021] Furthermore, the sintering process employs microwave sintering. During microwave sintering, microwaves not only reduce the thermal stress of aluminum nitride ceramics as a whole heating energy source, but also accelerate the sintering process by promoting the migration of charged vacancies on the grain surface, causing plastic deformation similar to diffusion creep. Its rapid heating characteristic helps to suppress abnormal grain growth, and the fine and uniform grains help to reduce stress concentration points in the ceramic and improve the bending strength of the material.

[0022] Furthermore, aluminum nitride whiskers are added to the aluminum nitride powder, with the addition amount being 0-2 wt% of the aluminum nitride powder. The addition amount of aluminum nitride whiskers is 1 wt% or 2 wt% of the aluminum nitride powder. The aluminum nitride whiskers have good interfacial bonding force with the aluminum nitride ceramic matrix, which helps to transfer stress between the whiskers and the matrix. When the substrate is subjected to external force, the crack will encounter the aluminum nitride whiskers during the crack propagation process, forcing the crack to deflect or bridge. On the one hand, more energy is consumed, and on the other hand, this crack deflection and bridging mechanism helps to prevent the rapid propagation of cracks, thereby improving the bending strength of the material.

[0023] The second objective of this invention is to provide a high-bending-strength aluminum nitride ceramic sintered body prepared by the aforementioned method.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects.

[0025] 1. This invention uses a co-precipitation method to prepare perovskite-type composites, and obtains Y2O3-Ca(Y-Sm)O3 composite material by calcination as a sintering aid. At the same time, the proportion and total amount of each component in the sintering aid are controlled, and microwave sintering is used to effectively improve the bending strength and thermal conductivity of the material, so that the prepared aluminum nitride ceramic sintered body has both high bending strength and high thermal conductivity.

[0026] 2. Existing technologies using a ternary mixed system of Y₂O₃, Sm₂O₃, and CaO suffer from delayed liquid phase formation, resulting in densification primarily concentrated at high temperatures. This can easily lead to abnormal grain growth. Furthermore, the Y₂O₃, Sm₂O₃, and CaO particles must first dissolve individually before reacting to form a liquid phase, a slow process prone to localized segregation due to uneven diffusion. In contrast, this invention utilizes co-precipitation and calcination to obtain a Y₂O₃-Ca(Y-Sm)O₃ composite material as a sintering aid. During sintering, this material completely wets the AlN particles, promoting particle rearrangement through a dissolution-precipitation mechanism, reducing liquid phase viscosity, accelerating mass transfer, and significantly improving densification. After calcination, a two-phase coexistence region of Y₂O₃ and perovskite exists, where Ca(Y-Sm)O₃ is a single-phase composite oxide. 3+ 、Sm 3+ Ca 2+ The uniform distribution within the crystal lattice allows for rapid formation of a homogeneous liquid phase during sintering without the need for additional diffusion, effectively controlling local segregation and thus improving the fracture toughness and flexural strength of AlN materials.

[0027] 3. Based on the use of Y2O3-Ca(Y-Sm)O3 composite material as a sintering aid and microwave sintering, this invention further adds aluminum nitride whiskers to aluminum nitride powder, which can further improve the bending strength and thermal conductivity of the material, making the bending strength of the material reach 631 MPa and the thermal conductivity reach 211.7 W / m•K. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0029] The following details the embodiments of a high-flexural-strength aluminum nitride ceramic sintered body and its preparation method according to the present invention. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art.

[0030] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0031] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0032] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0033] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0034] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0036] It should be noted that in the following examples, the weight of aluminum nitride powder is 10 kg, and the remaining auxiliary materials are calculated based on the weight of the aluminum nitride powder. A 100L ball mill jar is used for ball milling. In addition, unless otherwise specified, the experimental methods used in the examples are conventional methods. Unless otherwise specified, all materials, reagents, methods, and instruments used are conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0037] Example 1

[0038] A method for preparing a high-flexural-strength aluminum nitride ceramic sintered body includes the following steps:

[0039] (1) Preparation of Y2O3-Ca(Y-Sm)O3: YCl3 (1200 mmol / L) was used as the solution. Sm2O3 (20 mmol / L) and Ca(OH)2 (1000 mmol / L) were added in an 80℃ water bath with a stirring speed of 300 rpm. During the reaction, 20% ammonia water was used to adjust the pH of the solution to 12. The reaction was stopped after stirring for 1 h and allowed to stand for 4 h. Then it was placed in a muffle furnace at 800℃ and calcined for 2 h under the protection of N2 atmosphere. After grinding, Y2O3-Ca(Y-Sm)O3 was obtained for later use.

[0040] (2) Weigh 10 kg of aluminum nitride powder, add 3 wt% Y2O3-Ca(Y-Sm)O3 as the first powder, add alumina grinding balls with a mass ratio of 4:1 to the first powder, and then add a mixture of 2.2 wt% oleic acid, 45 wt% anhydrous ethanol and isopropanol (weight percentage of anhydrous ethanol and isopropanol is 1.2:1) to the grinding jar and mix for 8 h;

[0041] (3) Add 12wt% polyvinyl butyral and 4.2wt% dibutyl phthalate and ball mill for 10h;

[0042] (4) The mixture was degassed for 6 hours at a vacuum of -0.095 MPa using a vacuum degassing system to obtain the mixed slurry;

[0043] (5) The degassed slurry is scraped and pressed on the casting machine by a scraper to obtain a film with uniform thickness and smooth surface, resulting in a 0.7 mm thick aluminum nitride green ceramic sheet; the casting speed and temperature need to be controlled. In order to ensure that the green ceramic sheet does not crack and can be successfully demolded, three temperature zones are selected for air drying. The first temperature zone is controlled at 50-70℃, the second temperature zone is controlled at 90-110℃, and the third temperature zone is controlled at 130-150℃.

[0044] (6) Place the raw ceramic pieces in a muffle furnace at 530°C for 8 hours to degrease, and obtain aluminum nitride degreased pieces;

[0045] (7) Place the green ceramic sheet in the TE103 single-mode cavity for microwave sintering. High-purity nitrogen is used as the protective atmosphere during sintering. The temperature is slowly increased to 1150℃ at 10℃ / min and held for 60min. Then, the temperature is rapidly increased to 1420℃ at a rate of 80℃ / min and held for 50min. The aluminum nitride sintered body is then obtained by natural cooling.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that in step (7), the raw ceramic sheet is placed in a high-temperature pressureless sintering furnace, and under the protection of high-purity nitrogen, the temperature is slowly increased to 1200°C at 10°C / min and held for 60 min. Then, the temperature is increased to 1700°C at 30°C / min and held for 4 h. After that, the aluminum nitride sintered body is obtained by natural cooling.

[0048] It should be noted that this comparative example is pressureless sintering. The heating temperature of 1700℃ / min is the conventional sintering temperature for pressureless sintering. If the temperature is raised to the same temperature as microwave sintering, 1420℃, aluminum nitride ceramics cannot be formed. Therefore, the conventional sintering temperature of pressureless sintering was selected as the comparison.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 1 is that a mixture of Y2O3, CaO, and Sm2O3 is directly used as a sintering aid, and the amount added is the same as the molar amounts of Y, Sm, and Ca in Example 1.

[0051] Comparative Example 3

[0052] The difference between this comparative example and Example 1 is that the sintering aid prepared without adding Sm2O3 is labeled as Y2O3-Ca(Y)O3.

[0053] Comparative Example 4

[0054] The difference between this comparative example and Example 1 is that no Ca(OH)2 was added to prepare the sintering aid, which is labeled as Y2O3-Sm2O3.

[0055] The performance test data of the aluminum nitride sintered bodies prepared in Example 1, Comparative Examples 1 and 3 are shown in Table 1.

[0056] Table 1. Performance test data of aluminum nitride sintered bodies prepared in Examples 1 and Comparative Examples 1-4

[0057]

[0058] As can be seen from the data in Table 1:

[0059] By comparing Example 1 and Comparative Example 1, it was found that the bending strength was increased by 24.9% by using microwave sintering, indicating that microwave sintering can effectively improve the bending strength of the material and also improve the thermal conductivity. This is attributed to the fact that the heating method of microwave sintering can make the grains grow rapidly and uniformly, and the short sintering time will not cause the grains to be too large, thus obtaining fine and uniform grains.

[0060] Comparative Examples 1 and 2 revealed that, compared to directly adding the same molar amounts of the ternary sintering aids Y₂O₃, Sm₂O₃, and CaO, the co-precipitation-calcination method for preparing the sintering aid was beneficial for improving flexural strength. This is attributed to the superior ability of Ca(Y-Sm)O₃ to regulate grain boundary energy, thus inhibiting abnormal AlN grain growth. Thermal conductivity was also slightly improved, which is attributed to the presence of Y₂O₃ in Ca(Y-Sm)O₃. 3+ and Sm 3+ The synergistic effect effectively reduces the oxygen content in the AlN lattice.

[0061] Comparative examples 1, 3, and 4 revealed that when preparing the composite sintering aid, adding only the same amount of Ca(OH)2 reduced the flexural strength by 9.7% when the amount of YCl3 remained constant; while adding only the same amount of Sm2O3 reduced the flexural strength by 15.2%. This indicates that Ca(Y-Sm)O3 is superior to Sm2O3 in improving flexural strength. This demonstrates that using a composite sintering aid can effectively improve the flexural strength of materials, and the ratio among the three components also affects the flexural strength.

[0062] Therefore, it can be seen that the present invention uses Y2O3-Ca(Y-Sm)O3 perovskite-type composite oxide as a sintering aid, controls the proportion of each component in the sintering aid, and adopts microwave sintering, which can effectively improve the bending strength and thermal conductivity of the material.

[0063] Example 2

[0064] This embodiment is based on Example 1, but aluminum nitride whiskers are added to the aluminum nitride powder, with an addition amount of 1.0 wt%.

[0065] Comparative Example 4

[0066] The difference between this embodiment and Embodiment 2 is that the amount of aluminum nitride whiskers added is changed to 3.0 wt%.

[0067] Comparative Example 5

[0068] The difference between this embodiment and Embodiment 2 is that 6 wt% of Y2O3-Ca(Y-Sm)O3 was added.

[0069] The performance test data of the aluminum nitride sintered bodies prepared in Example 2 and Comparative Examples 4-6 are shown in Table 2.

[0070] Table 2. Performance test data of aluminum nitride sintered bodies prepared in Example 2 and Comparative Examples 4-6

[0071]

[0072] As can be seen from the data in Table 2:

[0073] By comparing Example 1, Example 2 and Comparative Example 4, it was found that adding aluminum nitride whiskers in Example 2 can effectively improve the bending strength of the material. However, when the aluminum nitride whisker content is increased to 3.0 wt%, the bending strength decreases. This is because excessive aluminum nitride whiskers are unevenly distributed in the ceramic matrix, forming agglomeration and generating stress concentration points. It may even change the phase composition of the ceramic material, leading to the appearance of new phase boundaries or grain boundaries inside the material.

[0074] By comparing Example 2 and Comparative Example 5, it was found that when the amount of sintering aid added was 6%, compared with the amount added at 3%, it can be seen that the range of sintering aid addition is selective. Excessive addition will lead to a decrease in the bending strength of aluminum nitride ceramic materials. Therefore, the optimal amount of sintering aid added is 3 wt% of aluminum nitride powder.

[0075] Therefore, based on the use of Y2O3-Ca(Y-Sm)O3 perovskite-type composite oxide as a sintering aid and microwave sintering, the present invention further adds aluminum nitride whiskers to aluminum nitride powder, which can further improve the bending strength and thermal conductivity of the material, making the bending strength of the material reach 631 MPa and the thermal conductivity reach 211.7 W / m•K.

[0076] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a high-flexural-strength aluminum nitride ceramic sintered body, characterized in that, Includes the following steps: Aluminum nitride powder, sintering aid, additives and solvent are ball-milled to obtain a mixed slurry; The mixed slurry was degassed, cast, degreased, and sintered to obtain a high-flexural-strength aluminum nitride ceramic sintered body. The sintering aid is a Y2O3-Ca(Y-Sm)O3 perovskite-type composite oxide, which is obtained by adding Sm2O3 and Ca(OH)2 to a YCl3 solution, co-precipitating them at 70-90℃ in an alkaline environment, and then calcining them. In the sintering aid, the mass of YCl3 > the mass of Ca(OH)2 > the mass of Sm2O3, the amount of the sintering aid added is 1~5wt% of aluminum nitride powder, and the sintering is carried out by microwave sintering.

2. The method for preparing a high-flexural-strength aluminum nitride ceramic sintered body according to claim 1, characterized in that, The alkaline environment is maintained at pH 11-13.

3. The method for preparing a high-flexural-strength aluminum nitride ceramic sintered body according to claim 1, characterized in that, The calcination temperature is 750-850℃, and the temperature is maintained for 2-4 hours.

4. The method for preparing a high-flexural-strength aluminum nitride ceramic sintered body according to claim 1, characterized in that, The additives include dispersants, binders, and plasticizers, with addition amounts of 1.5~3.5wt%, 7~14wt%, and 3~10wt% of aluminum nitride powder, respectively.

5. The method for preparing a high-flexural-strength aluminum nitride ceramic sintered body according to claim 1, characterized in that, The solvent is a mixture of anhydrous ethanol and isopropanol, and the amount added is 40-45 wt% of aluminum nitride powder.

6. The method for preparing a high-flexural-strength aluminum nitride ceramic sintered body according to any one of claims 1-5, characterized in that, The aluminum nitride powder contains aluminum nitride whiskers, and the amount added is 0~2wt% of the aluminum nitride powder.

7. A high-bending-strength aluminum nitride ceramic sintered body, prepared by the method described in any one of claims 1-6.

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