Silicon nitride material and preparation method therefor, and structural member

Abstract

Provided in the present application are a silicon nitride material and a preparation method therefor, and a structural member. The silicon nitride material comprises silicon nitride crystals, wherein the average short-axis grain size of the silicon nitride crystals is less than or equal to 3.5 μm. Since the average short-axis grain size of the silicon nitride crystals is relatively small, not only can concentrated stress be effectively reduced and dislocation slip be retarded, but defects and discontinuity at a grain boundary can also be reduced, and a phonon transport path can be optimized; therefore, the silicon nitride material has the characteristics of both high hardness and high thermal conductivity.

Description

A silicon nitride material, its preparation method, and structural components thereof

[0001] This application claims priority to Chinese Patent Application No. 202411846433.9, filed on December 13, 2024, entitled "A silicon nitride material and its preparation method and structural component", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of inorganic non-metallic materials technology, and more specifically, to a silicon nitride material, its preparation method, and structural components. Background Technology

[0003] With the development of modern high technology, ceramic materials have gradually become key materials for the development of many high-tech fields and are widely used in various fields of the national economy, such as national defense, chemical industry, metallurgy, electronics, machinery, aviation, aerospace, and biomedicine.

[0004] However, commonly used alumina and aluminum nitride materials each have their own advantages and disadvantages: alumina has high hardness and stability, but low thermal conductivity; aluminum nitride has excellent thermal conductivity, but insufficient hardness. Therefore, there is an urgent need to develop a ceramic material that combines high hardness and high thermal conductivity. Summary of the Invention

[0005] The main objective of this application is to provide a silicon nitride material that combines high hardness and high thermal conductivity.

[0006] This application also discloses a method for preparing silicon nitride material, which can prepare the above-mentioned silicon nitride material, and the process is simple and low in cost.

[0007] This application also discloses a structural component comprising the aforementioned silicon nitride material, thus the silicon nitride material of the structural component exhibits superior performance.

[0008] In a first aspect, this application discloses a silicon nitride material comprising silicon nitride crystals, wherein the average short-axis grain size of the silicon nitride crystals is less than or equal to 3.5 μm.

[0009] The silicon nitride material described above has an average long-axis grain size of less than or equal to 8.5 μm.

[0010] And / or, the difference between the maximum short-axis grain size and the minimum short-axis grain size of the silicon nitride crystal is less than or equal to 8.5 μm;

[0011] And / or, the difference between the maximum long axis grain size and the minimum long axis grain size of the silicon nitride crystal is less than or equal to 10 μm.

[0012] The silicon nitride material described above has a thermal conductivity greater than or equal to 90 W / m·K;

[0013] And / or, the Vickers hardness HV10 of the silicon nitride material is greater than or equal to 1600;

[0014] And / or, the density of the silicon nitride material is greater than or equal to 3.21 g / cm³. 3 ;

[0015] And / or, the flexural strength of the silicon nitride material is greater than or equal to 900 MPa.

[0016] The silicon nitride material as described above, wherein the mass percentage of β-Si3N4 in the silicon nitride material crystal is greater than or equal to 95%.

[0017] The silicon nitride material described above has a grain boundary phase between the silicon nitride crystals. The grain boundary phase includes a glass phase, which includes at least one of Mg, Ca, Zr, La, Ce, Y, Yb, Eu, Dy, Lu, B, and Ti.

[0018] Secondly, this application discloses a method for preparing the silicon nitride material as described above, comprising the following steps:

[0019] 1) A raw material including silicon powder and a nitrogen source are brought into contact to carry out a nitriding reaction to obtain a precursor containing silicon nitride; the precursor containing silicon nitride includes β-Si3N4 and α-Si3N4, and the mass ratio of β-Si3N4 to α-Si3N4 is 0.57-0.86.

[0020] 2) The silicon nitride-containing precursor is sintered to obtain the silicon nitride material.

[0021] In the preparation method described above, the raw materials including silicon powder also include at least one of the following: reinforcing phase, sintering aid, dispersant, binder, plasticizer, and defoamer;

[0022] The reinforcing phase includes TiC and / or TiN.

[0023] The preparation method described above further includes, before the nitriding reaction: sequentially performing a casting process and a debinding process on the raw material including silicon powder to obtain a debinding product; and contacting the debinding product with a nitrogen source to perform a nitriding reaction to obtain the precursor containing silicon nitride.

[0024] In the preparation method described above, the D50 of the silicon powder is 0.9μm-15μm, preferably 2.0μm-6.5μm;

[0025] And / or, the sintering temperature is 1700℃-1900℃.

[0026] The preparation method described above, wherein the nitriding reaction process includes:

[0027] 1) The raw material including silicon powder is brought into contact with a nitrogen source and subjected to a first reaction at 1200℃-1250℃ to obtain a first reaction product; wherein the mass ratio of β-Si3N4 to α-Si3N4 in the first reaction product is 0.04-0.54;

[0028] 2) The first reaction product is subjected to a second reaction at 1300℃-1350℃ to obtain a second reaction product; wherein the mass ratio of β-Si3N4 to α-Si3N4 in the second reaction product is 0.33-0.82;

[0029] 3) The second reaction product is subjected to a third reaction at 1400℃-1500℃ to obtain the silicon nitride-containing precursor.

[0030] Thirdly, this application provides a structural component comprising the silicon nitride material as described above or the silicon nitride material prepared by the preparation method described above.

[0031] The structural component described above is at least one of the following: an electrostatic chuck, a ceramic substrate, a ceramic bearing ball, a ceramic bearing sleeve, and a protective tube.

[0032] The silicon nitride material provided in this application includes silicon nitride crystals with an average short-axis grain size of less than or equal to 3.5 μm. The small grain size can not only effectively reduce concentrated stress and impede dislocation slip, but also reduce defects and discontinuities at grain boundaries and optimize phonon transport paths, thereby enabling the silicon nitride material to have both high hardness and high thermal conductivity. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments of this application or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 is a schematic diagram of an electrostatic chuck provided in this application;

[0035] Figure 2 is a schematic diagram of the main structure of an electrostatic chuck provided in this application;

[0036] Figure 3 is a scanning electron microscope image of the silicon nitride material in Example 1 of this application;

[0037] Figure 4 is a scanning electron microscope image of the silicon nitride material in Example 2 of this application;

[0038] Figure 5 is a scanning electron microscope image of the silicon nitride material in Example 3 of this application;

[0039] Figure 6 is a scanning electron microscope image of the silicon nitride material of Comparative Example 3 of this application;

[0040] Figure 7 is a scanning electron microscope image of the alumina material of Comparative Example 5 of this application;

[0041] Figure 8 is a grain size distribution diagram of the silicon nitride material in Embodiment 1 of this application;

[0042] Figure 9 is a grain size distribution diagram of the silicon nitride material in Embodiment 2 of this application;

[0043] Figure 10 is a grain size distribution diagram of the silicon nitride material in Embodiment 3 of this application;

[0044] Figure 11 is a grain size distribution diagram of the silicon nitride material of Comparative Example 3 of this application;

[0045] Figure 12 is a physical image of the silicon nitride ceramic green sheet of Comparative Example 2 of this application;

[0046] Figure 13 is a physical image of the silicon nitride material of Comparative Example 4 of this application. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0048] Ceramic materials are widely used in various sectors of the national economy due to their advantages such as high melting point, high hardness, high wear resistance, and oxidation resistance. Currently, commonly used alumina materials have high hardness and stability, but low thermal conductivity; aluminum nitride materials have excellent thermal conductivity, but insufficient hardness.

[0049] Specifically, semiconductor manufacturing processes are complex, requiring wafers to move, be processed, and inspected across multiple process devices, all while ensuring stable wafer fixation. Electrostatic chucks are process components used for wafer clamping in integrated circuit (IC) manufacturing processes such as etching, physical vapor deposition (PVD), and chemical vapor deposition (CVD), and are among the most critical components in semiconductor manufacturing. Compared to traditional mechanical chucks or vacuum chucks, the electrostatic chuck shown in Figure 1 can effectively clamp wafers, resulting in a more uniform force distribution. This avoids damage to the wafer caused by pressure and impacts during use, as is common with traditional mechanical chucks. It also effectively prevents wafer warping due to contact stress, reduces particle contamination, and increases the wafer processing area. Furthermore, it overcomes the limitations of vacuum chucks, such as their inability to operate in low-pressure environments and their inability to effectively control wafer temperature using back-blown gas. Therefore, electrostatic chucks are replacing traditional mechanical chucks and vacuum chucks, becoming the primary choice in semiconductor manufacturing processes. As shown in Figure 2, the clamping system of the electrostatic chuck is similar to a sandwich structure, consisting of an electrolyte adsorption layer, an electrode layer, and a base layer from top to bottom, all stacked together in a layered structure. The electrolyte adsorption layer is the core of the electrostatic chuck, typically made of ceramic materials such as alumina or aluminum nitride, and serves functions such as electrostatic induction, support, and heat conduction, directly determining the performance of the electrostatic chuck.

[0050] Specifically, Al2O3 chucks have high hardness and good stability, but poor thermal conductivity, only 20W / m·K to 30W / m·K, making it difficult to ensure temperature uniformity on the wafer surface and adversely affecting wafer processing stability and accuracy. AlN chucks, although having good thermal conductivity, as high as 170W / m·K to 200W / m·K, have a narrow bandgap that causes their resistivity to drop sharply above 400℃, making them unable to work effectively at high temperatures. In addition, their low hardness and poor stability make them difficult to meet the needs of advanced semiconductor manufacturing processes.

[0051] Based on this, in a first aspect, this application provides a silicon nitride material comprising silicon nitride crystals, wherein the average short-axis grain size of the silicon nitride crystals is less than or equal to 3.5 μm, for example, it can be a range of 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm or any two of these.

[0052] The silicon nitride material of this application comprises silicon nitride crystals with an average short-axis grain size of less than or equal to 3.5 μm, giving the silicon nitride material both high hardness and high thermal conductivity. This is because a smaller grain size means more grain boundaries, which can hinder dislocation movement. Simultaneously, smaller grains increase the number of grains per unit volume, resulting in more dispersed stress and effectively reducing the risk of stress concentration, thereby improving the strength, toughness, hardness, and density of the silicon nitride material. Furthermore, a smaller grain size reduces defects and discontinuities at grain boundaries, optimizing phonon transport paths and thus improving the thermal conductivity of the silicon nitride material. In addition, a refined grain size helps improve the uniformity and stability of the material, preventing uneven local thermal expansion, thereby improving the thermal stability of the material, reducing the tendency for grain growth at high temperatures, and maintaining the stability of its mechanical and thermal properties.

[0053] The silicon nitride material provided in this application includes silicon nitride crystals with an average short-axis grain size of less than or equal to 3.5 μm. This smaller grain size not only effectively reduces concentrated stress and hinders dislocation slip, but also reduces defects and discontinuities at grain boundaries, optimizing phonon transport paths. This allows the silicon nitride material to possess both high hardness and high thermal conductivity. When used in structural components, such as electrostatic chucks, this silicon nitride material enables stable operation of the electrostatic chuck within the 300℃-600℃ range, providing better positioning accuracy. Its resistivity does not significantly decrease at high temperatures. During high-temperature ion implantation, it can significantly improve wafer positioning accuracy and temperature uniformity, thereby increasing processing precision and yield.

[0054] In some embodiments of this application, the average long axis grain size of the silicon nitride crystal is less than or equal to 8.5 μm, for example, it can be a range of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 8.5 μm or any two of these.

[0055] In some embodiments, the difference between the maximum short-axis grain size and the minimum short-axis grain size of the silicon nitride crystal is less than or equal to 8.5 μm, for example, it can be a range of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 8.5 μm or any two of these.

[0056] In some embodiments, the difference between the maximum long axis grain size and the minimum long axis grain size of the silicon nitride crystal is less than or equal to 10 μm, for example, it can be a range of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any two of these.

[0057] In this application, the differences between the average long-axis grain size, the maximum short-axis grain size, and the minimum short-axis grain size, as well as the differences between the maximum long-axis grain size and the minimum long-axis grain size, of the silicon nitride crystal are within the aforementioned ranges. This ensures a uniform distribution of stress in the crystal, reduces local stress concentration, thereby improving the overall strength and durability of the material, enhancing fracture toughness, and reducing phonon scattering at grain boundaries, thus increasing the thermal conductivity of the material.

[0058] In some embodiments of this application, the thermal conductivity of the silicon nitride material is greater than or equal to 90 W / m·K, for example, it can be a range of 90 W / m·K, 91 W / m·K, 93 W / m·K, 95 W / m·K, 100 W / m·K, 110 W / m·K, 120 W / m·K, 130 W / m·K, 140 W / m·K, 150 W / m·K or any two of these.

[0059] The thermal conductivity of the silicon nitride material in this application is within the above-mentioned range, which means that the material can conduct heat quickly and effectively, which helps to prevent overheating and heat accumulation, maintain a uniform temperature distribution, reduce local overheating, and reduce the risk of material cracking or deformation.

[0060] In some embodiments, the Vickers hardness HV10 of the silicon nitride material is greater than or equal to 1600, for example, it can be a range of 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, 2000 or any two of these.

[0061] The silicon nitride material in this application has a hardness of HV10 within the above range, which gives it excellent wear resistance, significantly reduces the risk of surface damage, and enables the material to withstand large mechanical loads without deformation or breakage.

[0062] In some embodiments, the density of the silicon nitride material is greater than or equal to 3.21 g / cm³. 3 For example, it could be 3.21 g / cm³. 3 3.25g / cm 3 3.3g / cm 3 3.35g / cm 3 3.4g / cm 3 3.45g / cm 3 3.5g / cm 3 or a range consisting of any two of them.

[0063] The density of the silicon nitride material in this application is within the above range, which means that the porosity inside the material is low, which helps to improve the strength and hardness of the material. Fewer pores can reduce stress concentration points, thereby improving the compressive and bending strength of the material. In addition, the material has good thermal stability, can distribute heat more evenly, reduce thermal stress caused by uneven thermal expansion, and also help to reduce obstacles in the heat conduction path, such as pores, thereby improving the thermal conductivity of the material.

[0064] In some embodiments, the flexural strength of the silicon nitride material is greater than or equal to 900 MPa, for example, it can be a range of 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1200 MPa, 1300 MPa, 1400 MPa, 1500 MPa or any two of these.

[0065] The flexural strength of the silicon nitride material in this application is within the above-mentioned range, which enables it to withstand large loads without breaking or deforming. It can improve impact resistance to a certain extent and maintain its strength at high temperatures, thus reducing the risk of breakage and failure.

[0066] In some embodiments of this application, the mass percentage of β-Si3N4 in the silicon nitride crystal is greater than or equal to 95%. β-Si3N4 has very high mechanical strength and toughness, can withstand high stress without fracture, exhibits excellent thermal stability in high-temperature environments, can withstand extreme temperatures without significant performance changes, and has high thermal conductivity, enabling effective heat dissipation.

[0067] In the scanning electron microscope (SEM) image of silicon nitride material, the length of the short side of the columnar β-Si3N4 crystal represents the short-axis grain size, and the length of the long side represents the long-axis grain size. The average short-axis grain size of the silicon nitride crystal can be obtained by measuring the lengths of the short sides of multiple β-Si3N4 crystals and averaging them; similarly, the average long-axis grain size can be obtained by measuring the lengths of the long sides of multiple β-Si3N4 crystals. The longest short side length represents the maximum short-axis grain size, and the shortest long side length represents the minimum short-axis grain size; the longest long side length represents the maximum long-axis grain size, and the shortest long-axis grain size.

[0068] In some embodiments of this application, there are grain boundary phases between silicon nitride crystals. The grain boundary phase includes a glassy phase, which includes at least one of Mg, Ca, Zr, La, Ce, Y, Yb, Eu, Dy, Lu, B, and Ti.

[0069] Among them, the metal elements in the sintering aid and the metal elements in the reinforcing material, along with elements such as oxygen and silicon, form a glassy phase existing between the grain boundaries of silicon nitride crystals. This can reduce the sintering temperature of silicon nitride, promote liquid phase sintering, obtain silicon nitride materials with higher density, and improve their mechanical strength and toughness.

[0070] The grain size of the silicon nitride material prepared in this application is controllable. By controlling the in-situ nitridation of silicon powder, the nitridation rate of silicon powder, the conversion ratio of silicon powder to α-Si3N4, the conversion ratio of α-Si3N4 to β-Si3N4, and the nucleation site of β-Si3N4, a grain refinement effect is achieved. Compared with Si3N4 material prepared directly using silicon nitride powder, the average grain size is reduced from 5μm-10μm to below 3.5μm. By strengthening through grain refinement instead of adding aluminum for solid solution strengthening, the problem of decreased thermal conductivity caused by the introduction of Al in traditional high-hardness silicon nitride ceramics is avoided, and a combination of high hardness and high thermal conductivity is achieved.

[0071] Secondly, this application provides a method for preparing the silicon nitride material as described above, comprising the following steps:

[0072] 1) A raw material including silicon powder and a nitrogen source are brought into contact to undergo a nitriding reaction to obtain a precursor containing silicon nitride; the precursor containing silicon nitride includes β-Si3N4 and α-Si3N4, and the mass ratio of β-Si3N4 to α-Si3N4 is 0.57-0.86; for example, it can be a range of 0.57, 0.60, 0.65, 0.70, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86 or any combination thereof.

[0073] 2) The precursor containing silicon nitride is sintered to obtain silicon nitride material.

[0074] In step 1), the raw materials for preparing silicon nitride material include silicon powder. Silicon powder is readily available and has a lower oxygen content than silicon nitride powder. With the combined action of sintering aids, it can, to a certain extent, prevent oxygen atoms from entering the silicon nitride lattice, reducing crystal defects and facilitating heat transfer between grains, thus achieving better thermal conductivity. Simultaneously, materials using silicon powder as raw material exhibit less dimensional shrinkage during sintering, resulting in higher yields compared to materials using Si3N4 powder for the same product size. Specifically, the silicon powder purity is greater than or equal to 99%, and in one optional embodiment, it is greater than or equal to 99.5%; the oxygen content is less than or equal to 2%, and in another optional embodiment, it is less than or equal to 1%; the content of other impurities is less than or equal to 1%, and in another optional embodiment, it is less than or equal to 600 ppm. This ensures that the surface of the cast wafer does not crack or become rough, while also preventing performance degradation of the resulting silicon nitride material due to excessive oxygen content and the introduction of impurity elements.

[0075] The process involves in-situ nitriding of silicon powder and nitrogen sources, such as nitrogen gas, to produce silicon nitride, thus yielding a precursor containing silicon nitride. During the nitriding reaction, nitrogen gas is introduced at 900℃-1200℃, with the pressure gradually increasing with temperature. In the silicon powder nitriding stage, two processes occur simultaneously: the conversion of Si to α-Si3N4 and the conversion of α-Si3N4 to β-Si3N4. However, the conversion of Si to α-Si3N4 is dominant. When the mass ratio of β-Si3N4 to α-Si3N4 is less than 1, the rate of Si conversion to α-Si3N4 is faster than that of α-Si3N4 conversion to β-Si3N4. At the end of this heating stage, all the silicon powder is transformed into the Si3N4 crystalline phase. Some α-Si3N4 has not yet been transformed into β-Si3N4. That is, the mass ratio of β-Si3N4 to α-Si3N4 in the obtained silicon nitride precursor is 0.75-0.86. Subsequently, as the temperature rises, i.e. sintering treatment, the silicon powder undergoes further transformation and growth in the presence of the liquid phase, eventually becoming dense.

[0076] In step 2), the silicon nitride-containing precursor is sintered to completely convert α-Si3N4 into β-Si3N4, yielding silicon nitride material. The sintering temperature ensures sufficient growth of β-Si3N4 grains, eliminates porosity, and achieves high density in the silicon nitride material. This high density helps improve the material's mechanical strength and wear resistance, effectively controls grain growth and phase transformation, reduces defects and porosity, and improves the overall quality and performance of the material. The heating rate during sintering is controlled at 0.2℃ / min-5℃ / min, and the sintering time is 2h-6h. Afterward, cooling is performed at a certain rate, for example, 1℃ / min-5℃ / min, up to 1300℃-1500℃, followed by natural cooling to room temperature.

[0077] The method for preparing silicon nitride provided in this application can prepare the above-mentioned silicon nitride material, and the silicon nitride material has both high hardness and high thermal conductivity.

[0078] In some embodiments of this application, the raw materials including silicon powder also include at least one of a reinforcing phase, a sintering aid, a dispersant, a binder, a plasticizer, and a defoamer; the reinforcing phase includes TiC and / or TiN.

[0079] The raw materials in this application, including silicon powder, also include at least one of the following: reinforcing phase, sintering aid, dispersant, binder, plasticizer, and defoamer. The reinforcing phase significantly improves the mechanical strength and hardness of silicon nitride, making the material more wear-resistant. TiC and TiN can inhibit crack propagation, thereby improving the fracture toughness of the material, making it less prone to fracture under impact and mechanical loads. Furthermore, TiC and TiN possess excellent thermal stability, maintaining their performance in high-temperature environments. This characteristic helps improve the stability and reliability of silicon nitride ceramics in high-temperature applications. Simultaneously, the reinforcing phase can also improve the thermal conductivity of the material, facilitating effective heat dissipation. Since Si3N4 ceramics are difficult to form a dense crystal structure through self-diffusion during sintering, sintering aids are generally added to form a liquid phase (eutectic molten compound), providing a medium for rapid material transport, thereby accelerating the densification process of silicon nitride. Dispersants and binders can improve the uniformity and formability of the material, while plasticizers and defoamers help improve the material's flowability and reduce defects.

[0080] The mixed powder in this application includes silicon powder, sintering aids, and / or reinforcing phases. The silicon powder in the mixed powder comprises 75%-98% by mass; alternatively, the silicon powder content is 86.5%-95% by mass. The sintering aids in the mixed powder comprise 2%-25% by mass; alternatively, the sintering aids content is 5%-11% by mass. The reinforcing phase in the mixed powder comprises 0.5%-2.5% by mass. The binder accounts for 12%-40% of the mass of the mixed powder. Alternatively, the binder accounts for 15%-35% of the mass of the mixed powder. The plasticizer accounts for 2%-20% of the mass of the mixed powder. Alternatively, the plasticizer accounts for 3%-10% of the mass of the mixed powder. The dispersant accounts for 0.5%-5% of the mass of the mixed powder. Alternatively, the dispersant accounts for 1.5%-3% of the mass of the mixed powder. The defoamer accounts for 0.5%-3% of the mass of the mixed powder. Alternatively, the defoamer accounts for 0.5%-1.5% of the mass of the mixed powder.

[0081] The sintering aid includes at least one of metal oxides, metal non-oxides, rare earth oxides, and non-metal oxides. The metal oxides include at least one of MgO, CaO, and ZrO2; the metal non-oxides include MgSiN2; the rare earth oxides include at least one of La2O3, Ce2O3, Y2O3, Yb2O3, Eu2O3, Dy2O3, and Lu2O3; and the non-metal oxides include at least one of Si3N4, B2O3, and SiO2. As an optional implementation, the sintering aid includes at least one of MgO, Y2O3, and Yb2O3. The above-mentioned sintering aids ensure the compactness and improved performance of the ceramic. Intrinsic high hardness can be achieved without adding Al additives for solid solution strengthening. Optimization of the additives avoids the decrease in thermal conductivity caused by Al solid solution entering β-Si3N4, forming vacancies and causing lattice distortion, thus achieving a combination of ultra-high hardness and high thermal conductivity.

[0082] The binder includes at least one of polyvinyl butyral, acrylic resin, and rosin. As an optional embodiment, the binder includes polyvinyl butyral and / or acrylic resin. The plasticizer includes a primary plasticizer and a secondary plasticizer. The primary plasticizer includes at least one of dibutyl phthalate, dioctyl phthalate, diisooctyl phthalate, dimethyl phthalate, diethyl phthalate, dioctyl adipate, triethylene glycol diisooctyl ester, and di-n-hexyl adipate. The secondary plasticizer includes at least one of epoxidized soybean oil, methyl methacrylate, polyethylene glycol, and trioctyl phosphate. As an optional embodiment, the plasticizer includes at least one of dibutyl phthalate, dioctyl phthalate, triethylene glycol diisooctyl ester, and polyethylene glycol. The dispersant includes at least one of castor oil, fatty alcohol polyoxyethylene ether, polyvinylpyrrolidone, polyether-type polymeric dispersant, and polyester-type polymeric dispersant. As an optional embodiment, the dispersant includes at least one of castor oil, polyvinylpyrrolidone, and polyether-type polymeric dispersant. The defoamer includes at least one of alkane compounds without organosilicon, alcohol defoamers, and phosphate ester defoamers.

[0083] In some embodiments of this application, the process prior to the nitriding reaction includes: sequentially performing a casting process and a debinding process on a raw material including silicon powder to obtain a debinding product; and bringing the debinding product into contact with a nitrogen source to perform a nitriding reaction to obtain a precursor containing silicon nitride.

[0084] The process involves using a casting machine to cast raw materials, including silicon powder. The thickness of the slurry is controlled by lifting it with a scraper, and it is dried in a segmented oven with progressively increasing temperatures. The tape speed of the casting machine ranges from 60 mm / min to 1000 mm / min, and the casting temperature is set in a progressively increasing range from 40℃ to 120℃. Casting can produce thin and uniform silicon nitride materials, ensuring consistency in material thickness and composition, and allowing for precise control over the material's thickness and shape.

[0085] The debinding process takes place at temperatures ranging from 500℃ to 700℃, with a heating rate of 0.1℃ / min to 3℃ / min. This process removes binders and plasticizers introduced during the silicon nitride production process, ensuring that no harmful gases or material defects are generated during subsequent sintering. It also improves the purity of the silicon nitride material, enhances its mechanical and thermal properties, and helps reduce defects and voids in the molded product, increasing the material's density and strength. The debinding temperature is not lower than the decomposition temperature of the binders and plasticizers, thus decomposing these organic materials.

[0086] In some embodiments of this application, the D50 of the silicon powder is 0.9 μm-15 μm, for example, it can be a range of 0.9 μm, 1 μm, 1.5 μm, 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm or any combination thereof. As an optional embodiment, the D50 of the silicon powder is 2.0 μm-6.5 μm. This is beneficial for ultimately preparing a silicon nitride material with a small average short-axis grain size, thereby enabling the silicon nitride material to possess both high hardness and high thermal conductivity.

[0087] In some embodiments, the sintering temperature is 1700℃-1900℃, for example, it can be a range of 1700℃, 1710℃, 1730℃, 1750℃, 1800℃, 1850℃, 1900℃, or any combination thereof. This ensures sufficient growth of β-Si3N4 grains, eliminates porosity, and achieves high density in silicon nitride ceramics. This high density helps improve the mechanical strength and wear resistance of the material, and can effectively control grain growth and phase transformation, reduce defects and porosity in the material, and improve the overall quality and performance of the material.

[0088] In some embodiments of this application, the nitriding reaction process includes: 1) contacting a raw material including silicon powder with a nitrogen source and performing a first reaction at a temperature of 1200℃-1250℃, for example, 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, 1250℃, etc., to obtain a first reaction product; wherein the mass ratio of β-Si3N4 to α-Si3N4 in the first reaction product is 0.04-0.54, for example, 0.04, 0.11, 0.20, 0.30, 0.35, 0.39, 0.40, 0.42, 0.45, 0.47, 0.50, 0.52, 0.54, etc.; 2) subjecting the first reaction product to a temperature of 1300℃-1350℃, for example, 1300℃, 1310℃, 1320℃, 1250℃, etc. The second reaction is carried out at temperatures such as 330℃, 1340℃, and 1350℃ to obtain the second reaction product; wherein the mass ratio of β-Si3N4 to α-Si3N4 in the second reaction product is 0.33-0.82, for example, it can be 0.33, 0.35, 0.40, 0.43, 0.50, 0.60, 0.64, 0.66, 0.68, 0.70, 0.72, 0.75, 0.77, 0.80, 0.82, etc.; 3) The second reaction product is subjected to a third reaction at temperatures such as 1400℃-1500℃, for example, it can be 1400℃, 1410℃, 1420℃, 1430℃, 1440℃, 1450℃, 1460℃, 1470℃, 1480℃, 1490℃, and 1500℃ to obtain a precursor containing silicon nitride.

[0089] The nitriding process of silicon powder occurs within the range of 1200℃-1500℃, with a heating rate of 0.2℃ / min-1℃ / min. To control the grain size of the material and avoid abnormal grain growth, staged temperature control is adopted. The relationship between the Si and Si3N4 content and the mass ratio of β-Si3N4 and α-Si3N4 in this process is shown in the table below:

[0090] To achieve fine grain refinement, the nitriding reaction temperature was programmed to increase in stages within the range of 1200℃-1500℃ at a rate of 0.2℃ / min-1℃ / min. This controlled the nitriding rate and degree of silicon powder, ensuring that the mass ratio of β-Si3N4 to α-Si3N4 fluctuated between 0.04 and 0.86 during the nitriding process, with an overall β-Si3N4 to α-Si3N4 ratio less than 1. This ensured complete Si→α-Si3N4 conversion and controlled the gradual formation of β-Si3N4 nucleation sites. This ensured sufficient β-Si3N4 nucleation sites for the in-situ generated silicon nitride during the dissolution / precipitation growth stage, while suppressing β-Si3N4 growth during simultaneous sintering and densification, ultimately resulting in a fine-grained microstructure. This grain refinement significantly improved the strength, toughness, and intrinsic hardness of the silicon nitride material.

[0091] In this application, the above-mentioned programmed temperature rise method is used for the nitriding reaction, which allows the mass of β-Si3N4 and α-Si3N4 to fluctuate within the range of 0.04-0.86 during the nitriding process. This ensures the complete conversion of Si to α-Si3N4 and controls the gradual formation of nucleation sites for β-Si3N4. This is beneficial for obtaining silicon nitride materials with smaller particle sizes. The grain refinement strengthens the silicon nitride material, significantly improving its strength, toughness, and intrinsic hardness.

[0092] The specific preparation method of the silicon nitride material in this application may include the following steps:

[0093] 1) Add raw materials including silicon powder, sintering aids and / or reinforcing phases to a mixing equipment for mixing to obtain a mixed powder with a particle size reduction of 10%-20%.

[0094] 2) The first system, comprising mixed powder, dispersant, partial solvent, and silicon nitride balls, is subjected to a first ball milling process to obtain a first ball milling slurry. The solid content of the first ball milling slurry is 30%-70%, and as an optional embodiment, the solid content of the first ball milling slurry is 37%-50%. The ball-to-material mass ratio in the first ball milling process is (1-5):1, the rotation speed of the mixing equipment is 20rpm-100rpm, and the mixing time is 3h-6h.

[0095] 2) A second ball milling process is performed on the second system comprising the primary ball milling slurry, binder, plasticizer, defoamer, and residual solvent. After the secondary ball milling, the slurry is filtered through a filter screen to obtain a secondary ball milling slurry. The solid content of the secondary ball milling slurry is 30%-70%, and in an optional embodiment, the solid content is 37%-50%. The total mass of the solvent accounts for 70%-150% of the mass of the mixed powder, and in an optional embodiment, the total mass of the solvent accounts for 80%-130% of the mass of the mixed powder. The solvent includes at least one of ethanol, butanol, and ethyl acetate. The mass ratio of partial solvent to residual solvent is 9:1-4:6. The mixing time for a single ball milling is adjusted according to the particle size and solubility of the powder. The single ball milling time does not exceed 48 hours, and the duration of two ball millings is 24 hours-96 hours, with the rotation speed set to 30 rpm-300 rpm.

[0096] 3) The secondary ball-milled slurry is degassed under negative pressure and stirring conditions to obtain a non-aqueous silicon nitride casting slurry. The degassed pressure is less than or equal to -0.1 MPa, the stirring speed is 20 rpm-60 rpm, and the degassed time is 1 h-6 h. The dynamic viscosity of the non-aqueous silicon nitride casting slurry at 25°C is 6000 mPa·s-40000 mPa·s. As an optional embodiment, the dynamic viscosity of the non-aqueous silicon nitride casting slurry at 25°C is 9000 mPa·s-17000 mPa·s.

[0097] 4) The non-aqueous silicon nitride casting slurry is cast using a casting machine. The thickness of the slurry is controlled by lifting with a scraper. It is dried in a segmented oven with progressively increasing temperatures to obtain silicon nitride ceramic green sheets, which are then cut to the required dimensions. The thickness of the silicon nitride ceramic green sheets is 0.2mm-1mm, with an accuracy control of 1μm±2%. The length and width dimensions can be arbitrarily cut according to actual needs.

[0098] 5) Silicon nitride ceramic green sheets are isolated and stacked using boron nitride powder, and then debinded in a degreasing furnace to obtain debinded products.

[0099] 6) The debinding products are subjected to high-pressure nitriding and sintering treatment in sequence to obtain silicon nitride material.

[0100] Thirdly, this application provides a structural component comprising the silicon nitride material as described above or the silicon nitride material prepared by the preparation method described above. This structural component has advantages corresponding to the aforementioned silicon nitride material, which will not be elaborated further.

[0101] In some embodiments of this application, the structural component is at least one of an electrostatic chuck, a ceramic substrate, a ceramic bearing ball, a ceramic bearing sleeve, and a protective tube.

[0102] The specific structural components of this application include the aforementioned silicon nitride material; therefore, the silicon nitride material in these structural components exhibits superior performance. For example, if the structural component is an electrostatic chuck, the electrolyte adsorption layer of the electrostatic chuck includes silicon nitride material; therefore, this electrostatic chuck has high positioning accuracy and good high-temperature stability.

[0103] The technical solution of this application will be further described below with reference to specific embodiments.

[0104] Example 1

[0105] The method for preparing silicon nitride material in this embodiment includes the following steps:

[0106] 1) The mixed powder consists of silicon powder, sintering aids, and reinforcing phases. The sintering aids include Y2O3, MgO, and MgSiN2, and the reinforcing phase includes TiN. Weigh out 447.5g of Si powder (accounting for 89.5% of the mixed powder mass). The D50 of the silicon powder is 2.6μm. Y2O3 powder 32.5g (6.5% of the total mass of the mixed powder), MgO powder 14.5g (2.9% of the total mass of the mixed powder), MgSiN2 powder 3.0g (0.6% of the total mass of the mixed powder), TiN powder 2.5g (0.5% of the total mass of the mixed powder), binder polyvinyl butyral 133.5g (26.7% of the total mass of the mixed powder), plasticizer diisooctyl phthalate 35g (7% of the total mass of the mixed powder), dispersant polyvinylpyrrolidone 12.5g (2.5% of the total mass of the mixed powder), defoamer diethylhexanol 5g (1% of the total mass of the mixed powder), solvent ethanol 450g (90% of the total mass of the mixed powder), silicon nitride grinding balls 750g (150% of the total mass of the mixed powder).

[0107] 2) Weigh the silicon powder, sintering aid, and reinforcing phase and add them to a mixing device for mixing. The mixing speed is set to 30 rpm and the mixing time is 3 hours to obtain a mixed powder. Then, add the mixed powder, silicon nitride grinding balls, dispersant, and part of the solvent to a ball mill and perform a ball milling process at 60 rpm for 36 hours to obtain a primary ball mill slurry.

[0108] 3) Then, binder, plasticizer, defoamer and remaining solvent are added to the primary ball mill slurry and the mixture is ball milled for 36 hours. After the ball milling is completed, the mixture is filtered to obtain the secondary ball mill slurry.

[0109] 4) The secondary ball milling slurry was degassed for 3 hours under a negative pressure of -0.07 MPa and a stirring speed of 30 rpm to obtain a non-aqueous silicon nitride casting slurry with a dynamic viscosity of 11000 mPa·s at 25℃.

[0110] 5) The non-aqueous silicon nitride casting slurry was cast using a casting machine with a belt speed of 300 mm / min and five temperature zones of 40℃, 50℃, 60℃, 70℃ and 80℃ in ascending order for drying, to obtain silicon nitride ceramic green sheets with a thickness of 0.5 mm.

[0111] 6) Use boron nitride powder to isolate and stack silicon nitride ceramic green sheets, pre-fire at 550℃ in a debinding furnace to remove the binder, with a heating rate of 1℃ / min, to obtain the debinded product.

[0112] 7) The debinding product was subjected to nitriding treatment to obtain a precursor containing silicon nitride. The heating rate was 2℃ / min, and the temperatures were maintained at 1100℃ for 150 min, 1200℃ for 120 min, 1250℃ for 120 min, 1300℃ for 60 min, 1350℃ for 300 min, and 1400℃ and 1450℃ for 300 min each. During the nitriding process, nitrogen gas was introduced when the temperature reached 1200℃, and the pressures were controlled at 0.5 MPa at 1200℃, 0.5 MPa at 1250℃, 0.7 MPa at 1300℃, 0.7 MPa at 1350℃, 1.0 MPa at 1400℃, and 1.0 MPa at 1450℃. The mass ratio of β-Si3N4 to α-Si3N4 was 0.08 after maintaining the temperature at 1200℃ for 120 min, 0.41 after maintaining the temperature at 1250℃ for 120 min, 0.43 after maintaining the temperature at 1300℃ for 60 min, 0.69 after maintaining the temperature at 1350℃ for 300 min, 0.72 after maintaining the temperature at 1400℃ for 300 min, and 0.78 after maintaining the temperature at 1450℃ for 300 min.

[0113] 8) The silicon nitride-containing precursor was sintered to obtain silicon nitride material. The sintering temperature was 1900℃, held for 3 hours; then cooled to 1400℃ at a rate of 3℃ / min; finally, it was allowed to cool naturally to room temperature. The silicon nitride material consists of silicon nitride crystals, with grain boundary phases existing between the crystals. These grain boundary phases include a glassy phase, comprising Y, Mg, Si, O, and Ti.

[0114] Example 2

[0115] The preparation method of silicon nitride material in Example 2 is basically the same as that in Example 1, except that: in step 1), the sintering aids include Y2O3 and MgO, and 450g of Si powder (accounting for 90% of the mass of the mixed powder), 28.0g of Y2O3 powder (accounting for 5.6% of the mass of the mixed powder), 17.0g of MgO powder (accounting for 3.4% of the mass of the mixed powder), and 5.0g of TiN powder (accounting for 1.0% of the mass of the mixed powder) are weighed out, and the binder is polyvinyl alcohol condensate. The mixture contains 137.5g of butyraldehyde (27.5% of the mixed powder mass), 27.5g of diisooctyl phthalate (5.5% of the mixed powder mass), 10.0g of polyvinylpyrrolidone (2.0% of the mixed powder mass), 5g of diethylhexanol (1% of the mixed powder mass), 450g of ethanol (90% of the mixed powder mass), and 1000g of silicon nitride grinding balls (200% of the mixed powder mass). In step 2), the first ball milling treatment time is 30 hours. In step 3), the second ball milling treatment time is 30 hours. In step 4), the degassing treatment time is 5 hours. In step 6), the debinding treatment temperature is 600℃, and the heating rate is 0.1℃ / min-3℃ / min. In step 7), the process control procedure is as follows: maintain 1100℃ for 120 min, 1200℃ for 150 min, 1250℃ for 180 min, 1300℃ for 150 min, 1350℃ for 200 min, and maintain 1400℃ and 1450℃ for 300 min each. During the nitriding process, nitrogen gas is introduced when the temperature reaches 1200℃, and the pressure is controlled at 0.5 MPa at 1200℃, 0.5 MPa at 1250℃, 0.8 MPa at 1300℃, 0.9 MPa at 1350℃, 1.0 MPa at 1400℃, and 1.2 MPa at 1450℃. After maintaining the temperature at 1200℃ for 150 min, the mass ratio of β-Si3N4 to α-Si3N4 was 0.11; after maintaining the temperature at 1250℃ for 180 min, the mass ratio was 0.39; after maintaining the temperature at 1300℃ for 150 min, the mass ratio was 0.43; after maintaining the temperature at 1350℃ for 200 min, the mass ratio was 0.64; after maintaining the temperature at 1400℃ for 300 min, the mass ratio was 0.73; and after maintaining the temperature at 1450℃ for 300 min, the mass ratio was 0.78. In step 8), the sintering temperature was 1800℃, and the holding time was 6 h. Silicon nitride materials include silicon nitride crystals, and there are grain boundary phases between the silicon nitride crystals. The grain boundary phases include glass phases, which include Y, Mg, Si, O, and Ti.

[0116] Example 3

[0117] The preparation method of silicon nitride material in Example 3 is basically the same as that in Example 1, except that in step 1), the sintering aids include Y2O3, MgO, and Si3N4, and the reinforcing phase includes TiC. Weigh out 445.5g of Si powder (89.1% of the mixed powder mass), 22.5g of Y2O3 powder (4.5% of the mixed powder mass), 19.5g of MgO powder (3.9% of the mixed powder mass), 2.5g of Si3N4 powder (0.5% of the mixed powder mass), 10g of TiC powder (2% of the mixed powder mass), and 141.5g of polyvinyl butyral binder (1% of the mixed powder mass). The mixture contains 28.3% (by weight), 28.5g (5.7% by weight) of diisooctyl phthalate (plasticizer), 7.5g (1.5% by weight) of polyvinylpyrrolidone (dispersant), 7.5g (1.5% by weight) of diethylhexanol (defoamer), 500g (100% by weight) of ethanol (solvent), and 1000g (200% by weight) of silicon nitride grinding balls. In step 2), the first ball milling treatment time is 30 hours. In step 3), the second ball milling treatment time is 30 hours. In step 4), the degassing treatment time is 5 hours. In step 6), the debinding treatment temperature is 500℃. In step 7), the process control is as follows: maintain 1100℃ for 300 min, 1200℃ for 60 min, 1250℃ for 120 min, 1300℃ for 120 min, 1350℃ for 300 min, and maintain 1400℃ and 1450℃ for 360 min each. During the nitriding process, nitrogen gas is introduced when the temperature reaches 1200℃, and the pressure is controlled at 0.5 MPa at 1200℃, 0.6 MPa at 1250℃, 0.8 MPa at 1300℃, 0.8 MPa at 1350℃, 1.0 MPa at 1400℃, and 1.0 MPa at 1450℃. After maintaining the temperature at 1200℃ for 60 min, the mass ratio of β-Si3N4 to α-Si3N4 was found to be 0.04; after maintaining the temperature at 1250℃ for 120 min, the mass ratio was 0.40; after maintaining the temperature at 1300℃ for 120 min, the mass ratio was 0.43; after maintaining the temperature at 1350℃ for 300 min, the mass ratio was 0.74; after maintaining the temperature at 1400℃ for 360 min, the mass ratio was 0.65; and after maintaining the temperature at 1450℃ for 360 min, the mass ratio was 0.76. In step 8), the sintering temperature was 1700℃, and the holding time was 4 h. Silicon nitride materials include silicon nitride crystals, and there are grain boundary phases between the silicon nitride crystals. The grain boundary phases include glass phases, which include Y, Mg, Si, O, and Ti.

[0118] Example 4

[0119] The preparation method of the silicon nitride material in Example 4 is basically the same as that in Example 1, except that the D50 of the silicon powder is changed to 0.9 μm. The mass ratio of β-Si3N4 and α-Si3N4 in each stage is basically the same as in Example 1.

[0120] Example 5

[0121] The preparation method of the silicon nitride material in Example 5 is basically the same as that in Example 1, except that the D50 of the silicon powder is changed to 6.5 μm. The mass ratio of β-Si3N4 and α-Si3N4 in each stage is basically the same as in Example 1.

[0122] Example 6

[0123] The preparation method of the silicon nitride material in Example 6 is basically the same as that in Example 1, except that the D50 of the silicon powder is changed to 15 μm. The mass ratio of β-Si3N4 and α-Si3N4 in each stage is basically the same as in Example 1.

[0124] Example 7

[0125] The preparation method of the silicon nitride material in Example 7 is basically the same as that in Example 1, except that the sintering temperature is changed to 1700℃. The mass ratio of β-Si3N4 and α-Si3N4 in each stage is basically the same as in Example 1.

[0126] Example 8

[0127] The preparation method of the silicon nitride material in Example 8 is basically the same as that in Example 1, except that the reinforcing phase is changed to TiC. The mass ratio of β-Si3N4 and α-Si3N4 in each stage is basically the same as in Example 1.

[0128] Comparative Example 1

[0129] The preparation methods of the silicon nitride materials in Comparative Example 1 and Example 3 are basically the same, except for the types of sintering aids. A small amount of Al-containing sintering aids are added: 444.5g of Si powder (88.9% of the mixed powder mass), 22.5g of Y2O3 powder (4.5% of the mixed powder mass), 19.5g of MgO powder (3.9% of the mixed powder mass), 2.5g of Si3N4 powder (0.5% of the mixed powder mass), 10g of TiC powder (2% of the mixed powder mass), and 1g of AlN powder (0.2% of the mixed powder mass). The mass ratio of β-Si3N4 and α-Si3N4 in each stage is basically the same as in Example 3.

[0130] Comparative Example 2

[0131] The preparation methods of the silicon nitride materials in Comparative Example 2 and Example 3 are basically the same, except that the D50 of the silicon powder is 18.3 μm, the binder is 141.0 g of polyvinyl butyral (accounting for 28.2% of the mass of the mixed powder), the plasticizer is 36.0 g of diisooctyl phthalate (accounting for 7.2% of the mass of the mixed powder), the dispersant is 15.0 g of polyvinylpyrrolidone (accounting for 3.0% of the mass of the mixed powder), the defoamer is 7.5 g of diethylhexanol (accounting for 1.5% of the mass of the mixed powder), and the solvent is 50 g of ethanol (accounting for 100% of the mass of the mixed powder). The mass ratio of β-Si3N4 and α-Si3N4 in each stage is basically the same as in Example 3.

[0132] Comparative Example 3

[0133] The preparation methods of the silicon nitride materials in Comparative Example 3 and Example 3 are basically the same, except for the control process of the nitriding reaction: in this process, the temperature is held at 1100℃ for 60 min, then at 1500℃ for 180 min, and the temperature is increased from 1100℃ to 1500℃ at a rate of 0.5℃ / min. During the nitriding process, after holding at 1500℃ for 180 min, the mass ratio of β-Si3N4 to α-Si3N4 was measured to be 1.23.

[0134] Comparative Example 4

[0135] The preparation methods of silicon nitride materials in Comparative Example 4 and Example 3 are basically the same, except that the sintering temperature is 1950℃ and the holding time is 4h.

[0136] Comparative Example 5

[0137] The preparation method of the alumina material in this comparative example is basically the same as that of the silicon nitride material in Example 1, except that in step 1), the mixed powder includes alumina and sintering aids, and the sintering aids include ZrO2, MgO, La2O3, and Si3N4. 430g of Al2O3 powder (86% of the mixed powder mass), 62.5g of ZrO2 powder (12.5% ​​of the mixed powder mass), 2.5g of MgO powder (0.5% of the mixed powder mass), 2.5g of La2O3 powder (0.5% of the mixed powder mass), and 2.5g of Si3N4 powder (0.5% of the mixed powder mass) are weighed. The binder consists of 60.0 g of polyvinyl butyral (12% of the mixed powder mass), 60.0 g of diisooctyl phthalate (12% of the mixed powder mass), 10.0 g of polyvinylpyrrolidone (2% of the mixed powder mass), 5.0 g of diethylhexanol (1.0% of the mixed powder mass), 300 g of ethanol (60% of the mixed powder mass), and 1000 g of silicon nitride grinding balls (200% of the mixed powder mass). In step 2), the first ball milling treatment time is 12 hours. In step 3), the second ball milling treatment time is 16 hours. In step 4), the degassing treatment time is 5 hours. In step 5), the belt speed of the casting machine is 120 mm / min, and the temperature is set in four increasing zones: 50℃, 60℃, 65℃, and 80℃. In step 6), the cast ceramic green sheets are isolated and stacked using boron nitride powder, and pre-fired in a debinding furnace at 550℃ to remove the binder, with a heating rate of 0.1℃ / min-3℃ / min, to obtain the debinded product. In steps 7) and 8), the debinded product is sintered in air at a temperature of 1600℃ for 2 hours, and then cooled naturally.

[0138] Test case

[0139] 1. Density test: The density of the ceramic substrate was tested according to GB / T 3850-2015, which specifies the method for determining the density of dense sintered metallic materials and cemented carbides. The test sample was a 10mm diameter disc.

[0140] 2. Bending strength test: Refer to GB / T 6569-2006 Test method for bending strength of fine ceramics, with a loading speed of 0.5 mm / min and a measurement distance of 30 mm.

[0141] 3. Thermal conductivity test: The thermal diffusivity or thermal conductivity is measured using the flash method according to GB / T 22588-2008.

[0142] 4. Crystal phase content test: The mass ratio of β-Si3N4 and α-Si3N4 crystal phases was measured using the general rules of polycrystalline X-ray diffraction method JY / T 0587-2020.

[0143] 5. Grain size test: The microstructure of silicon nitride material was observed using a field emission scanning electron microscope. The short axis and long axis of the grains were sampled and tested using ImageJ software. The largest short axis grain size among 100 grains is the largest short axis grain size, and the smallest short axis grain size among 100 grains is the smallest short axis grain size. The largest long axis grain size among 100 grains is the largest long axis grain size, and the smallest long axis grain size among 100 grains is the smallest long axis grain size. The average value of the short axis dimensions among 100 grains is the average short axis grain size, and the average value of the long axis dimensions among 100 grains is the average long axis grain size.

[0144] 6. Vickers hardness HV10: The Vickers hardness HV10 of silicon nitride materials was measured using GB / T 16534-2009, the room temperature hardness test method for fine ceramics.

[0145] 7. Elemental analysis methods in the glass phase: The composition and elemental distribution of the grain boundary glass phase are observed and tested using transmission electron microscopy and high-resolution transmission electron microscopy.

[0146] Figure 3 is a scanning electron microscope image of the silicon nitride material of Example 1 of this application.

[0147] Figure 4 is a scanning electron microscope image of the silicon nitride material of Example 2 of this application.

[0148] Figure 5 is a scanning electron microscope image of the silicon nitride material of Example 3 of this application.

[0149] Figure 6 is a scanning electron microscope image of the silicon nitride material of Comparative Example 3 of this application.

[0150] Figure 7 is a scanning electron microscope image of the alumina material of Comparative Example 5 of this application.

[0151] As can be seen from Figures 3-7, the silicon nitride materials prepared in Examples 1-3 of this application have smaller grain sizes, while the silicon nitride materials prepared in Comparative Examples 3 and 5 have larger grain sizes.

[0152] Figure 8 is a grain size distribution diagram of the silicon nitride material in Example 1 of this application.

[0153] Figure 9 is a grain size distribution diagram of the silicon nitride material in Example 2 of this application.

[0154] Figure 10 is a grain size distribution diagram of the silicon nitride material in Example 3 of this application.

[0155] Figure 11 is a grain size distribution diagram of the silicon nitride material of Comparative Example 3 of this application.

[0156] As can be seen from Figures 8-11, the silicon nitride materials prepared in Examples 1-3 of this application have a narrower grain size distribution, while the silicon nitride materials prepared in Comparative Example 3 have a wider grain size distribution.

[0157] Figure 12 is a physical image of the silicon nitride ceramic green sheet of Comparative Example 2 of this application.

[0158] As can be seen from Figure 12, the silicon nitride ceramic green sheet prepared in Comparative Example 2 has cracks and cannot be subjected to subsequent sintering.

[0159] Figure 13 is a physical image of the silicon nitride material of Comparative Example 4 of this application.

[0160] As can be seen from Figure 13, the silicon nitride material prepared in Comparative Example 4 was overburned, resulting in silicon nitride decomposition. The surface was rough and uneven, making it unsuitable for use as an electrostatic chuck.

[0161] Table 1

[0162] The silicon nitride material provided in this application includes silicon nitride crystals with an average short-axis grain size of less than or equal to 3.5 μm. The small grain size can not only effectively reduce concentrated stress and impede dislocation slip, but also reduce defects and discontinuities at grain boundaries and optimize phonon transport paths, thereby enabling the silicon nitride material to have both high hardness and high thermal conductivity.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing 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 can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A silicon nitride material, characterized in that, The silicon nitride material comprises silicon nitride crystals, wherein the average short-axis grain size of the silicon nitride crystals is less than or equal to 3.5 μm.

2. The silicon nitride material according to claim 1, characterized in that, The average long-axis grain size of the silicon nitride crystal is less than or equal to 8.5 μm; And / or, the difference between the maximum short-axis grain size and the minimum short-axis grain size of the silicon nitride crystal is less than or equal to 8.5 μm; And / or, the difference between the maximum long axis grain size and the minimum long axis grain size of the silicon nitride crystal is less than or equal to 10 μm.

3. The silicon nitride material according to claim 1 or 2, characterized in that, The thermal conductivity of the silicon nitride material is greater than or equal to 90 W / m·K; And / or, the Vickers hardness HV10 of the silicon nitride material is greater than or equal to 1600; And / or, the density of the silicon nitride material is greater than or equal to 3.21 g / cm³. 3 ; And / or, the flexural strength of the silicon nitride material is greater than or equal to 900 MPa.

4. The silicon nitride material according to any one of claims 1-3, characterized in that, The mass percentage of β-Si3N4 in the silicon nitride crystal is greater than or equal to 95%.

5. The silicon nitride material according to any one of claims 1-4, characterized in that, The silicon nitride crystals contain grain boundary phases, which include a glassy phase, and the glassy phase includes at least one of Mg, Ca, Zr, La, Ce, Y, Yb, Eu, Dy, Lu, B, and Ti.

6. A method for preparing the silicon nitride material according to any one of claims 1-5, characterized in that, Includes the following steps: 1) A raw material including silicon powder and a nitrogen source are brought into contact to carry out a nitriding reaction to obtain a precursor containing silicon nitride; the precursor containing silicon nitride includes β-Si3N4 and α-Si3N4, and the mass ratio of β-Si3N4 to α-Si3N4 is 0.57-0.

86. 2) The silicon nitride-containing precursor is sintered to obtain the silicon nitride material.

7. The preparation method according to claim 6, characterized in that, The raw materials including silicon powder also include at least one of the following: reinforcing phase, sintering aid, dispersant, binder, plasticizer, and defoamer; The reinforcing phase includes TiC and / or TiN.

8. The preparation method according to claim 6 or 7, characterized in that, Prior to the nitriding reaction, the process further includes: sequentially performing a casting process and a debinding process on the raw material containing silicon powder to obtain a debinding product; and then contacting the debinding product with a nitrogen source to perform a nitriding reaction to obtain the precursor containing silicon nitride.

9. The preparation method according to any one of claims 6-8, characterized in that, The silicon powder has a D50 of 0.9μm-15μm; And / or, the sintering temperature is 1700℃-1900℃.

10. The preparation method according to any one of claims 9, characterized in that, The silicon powder has a D50 of 2.0μm-6.5μm.

11. The preparation method according to any one of claims 6-10, characterized in that, The nitriding reaction process includes: 1) The raw material including silicon powder is brought into contact with a nitrogen source and subjected to a first reaction at 1200℃-1250℃ to obtain a first reaction product; wherein the mass ratio of β-Si3N4 to α-Si3N4 in the first reaction product is 0.04-0.54; 2) The first reaction product is subjected to a second reaction at 1300℃-1350℃ to obtain a second reaction product; wherein the mass ratio of β-Si3N4 to α-Si3N4 in the second reaction product is 0.33-0.82; 3) The second reaction product is subjected to a third reaction at 1400℃-1500℃ to obtain the silicon nitride-containing precursor.

12. A structural component, characterized in that, This includes the silicon nitride material according to any one of claims 1-5 or the silicon nitride material prepared by the preparation method according to any one of claims 6-11.

13. The structural component according to claim 12, characterized in that, The structural component is at least one of the following: an electrostatic chuck, a ceramic substrate, a ceramic bearing ball, a ceramic bearing sleeve, and a protective tube.

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