WO2023024273A1

WO2023024273A1 - Non-oxide y3si2c2 sintering aid, high-performance silicon nitride ceramic substrate, and preparation methods therefor

Info

Publication number: WO2023024273A1
Application number: PCT/CN2021/130573
Authority: WO
Inventors: 伍尚华; 黄瑶; 黄民忠
Original assignee: 广东工业大学
Priority date: 2021-08-27
Filing date: 2021-11-15
Publication date: 2023-03-02
Also published as: CN113697810A

Abstract

A non-oxide Y3Si2C2 sintering aid, a high-performance silicon nitride ceramic substrate, and preparation methods therefor, relating to the technical field of silicon nitride ceramic preparation. In the preparation method for the non-oxide Y3Si2C2 sintering aid, preparation is implemented by means of a flux method by using silicon carbide and metal yttrium as main raw materials and using sodium chloride and potassium chloride as supplements; the method is a synthesis method for synthesizing the non-oxide Y3Si2C2 by introducing a low melting point salt as a fluxing agent in a conventional solid phase reaction; a non-oxide Y3Si2C2 sintering aid can be obtained. In the preparation method for the high-performance silicon nitride ceramic substrate, the non-oxide Y3Si2C2 and a rare earth oxide are used as sintering aids, and the addition of said non-oxide and the rare earth oxide facilitates reducing introduction of oxygen impurities in ab oxide sintering aid and promoting sintering densification; the selected sintering aids can react with the oxygen impurities to purify lattices and effectively improve thermal conductivity.

Description

A non-oxide Y 3Si 2C 2 Sintering aid, high-performance silicon nitride ceramic substrate and preparation method thereof

technical field

The invention relates to the technical field _of silicon nitride ceramic preparation, in particular to a non-oxide _Y3Si2C2 sintering aid, a high- _performance silicon nitride ceramic substrate and a preparation method thereof.

Background technique

With the development of high-power integrated circuits (ICs), high-power IGBT modules and LEDs, high-frequency communications, LED lighting, new energy vehicles, high-speed rail, wind energy and photovoltaic power generation, higher requirements are placed on substrate packaging materials . Since the silicon nitride ceramic substrate must carry and protect the entire device during use, and a certain thermal stress will also be generated during the exothermic cooling process, there are certain requirements for the strength of the silicon nitride substrate. A sufficiently high strength must be ensured to ensure a long service life of electronic devices, so it is particularly important to prepare silicon nitride ceramics with high thermal conductivity and high strength.

Silicon nitride is a compound with strong covalent bonds. It mainly exists in two phases, namely α phase and β phase. The crystal forms of the two phases are all hexagonal. On the c-axis, the β-type unit cell constant is about twice that of the α-type, so the microstructure of the β-phase tends to be rod-shaped, and the α-phase tends to be equiaxed, which also has a certain impact on the thermal conductivity. Because of the lack of freely movable electrons as heat carriers, the heat conduction is achieved through the vibration between lattices. Lattice vibration is a kind of non-harmonic vibration, and the vibration energy is quantized, called phonon. Phonons achieve heat transfer by restricting each other and coordinating vibrations in the lattice vibration process, and the mean free path of phonons determines the efficiency of heat transfer. Among them, the phonon mean free path is mainly affected by the scattering caused by the collision between phonons, and the scattering caused by the interaction between phonons and crystal grain boundary phases, defects and impurities. The ideal crystal is a non-elastic body, and the main source of thermal resistance is the collision between phonons, that is, the thermal conductivity is determined by the mean free path of phonons, and will not be affected by structural elements. However, the actual crystal is an elastic body, and there are various defects, oxygen impurities, and additives that interfere with and scatter phonon propagation, resulting in a decrease in the thermal conductivity of the material.

In 2001, Watari et al. predicted that the upper limit of room temperature thermal conductivity of β-Si ₃ N ₄ could reach 400W/(m K), and Hirosaki calculated it in 2002 by combining molecular dynamics method and Green-Kubo equation Theoretical room temperature thermal conductivities of single crystal α-Si ₃ N ₄ and β-Si ₃ N ₄ on a, c axis are 105W/(m·K) and 225W/(m·K), 170W/( m K) and 450W/(m K), but the thermal conductivity of polycrystalline silicon nitride obtained by the researchers so far is the highest and only 177W/(m K) of silicon nitride ceramics can be obtained, And in order to obtain this value, a very high price was paid.

As one of the ceramics with the best comprehensive performance, silicon nitride has a broad application market. At present, the market of high-performance silicon nitride substrates is mainly monopolized by Toshiba, Kyocera, Denka and MARUWA of Japan and Rogers of the United States. The rate is still low, and although the Shanghai Institute of Ceramics has obtained a silicon nitride ceramic substrate with a maximum of 136.9W/(m K), it is still in the laboratory test stage and there is still a distance from mass production, so it is necessary for high thermal conductivity The research on the preparation process of silicon nitride substrate is very necessary.

Contents of the invention

The technical problem to be solved by the present invention is how to provide a suitable sintering aid, combined with a sintering method, to improve thermal conductivity and obtain a high-performance silicon nitride ceramic substrate.

In order to solve the above problems, the present invention uses a vacuum pressure sintering method to prepare a silicon nitride ceramic substrate with high thermal conductivity and high mechanical properties, so as to improve the density, bending strength and thermal conductivity of the silicon nitride ceramic substrate.

Specifically, the present invention proposes the following technical solutions:

In a first aspect, the present invention provides a method for preparing a non-oxide sintering aid Y ₃ Si ₂ C ₂ , comprising the following steps:

S1. Grinding the mixture of silicon carbide and metal yttrium and the metal salt in an agate grinding bowl at a volume ratio of 1:2-8, and mixing them uniformly to obtain a mixed powder;

S2. Put the mixed powder into an alumina crucible, and cover the crucible to prevent bumping from contaminating the furnace cavity;

S3. Put the alumina crucible in the corundum tube of the tube furnace, and carry out sintering in the tube furnace in a vacuumed inert atmosphere. After the sintering is completed, the non-oxide Y ₃ Si ₂ C ₂ is obtained.

Its further technical solution is that in step S3, the sintering operation of the vacuum inert atmosphere tube furnace is as follows: when the vacuum degree in the furnace body reaches -0.1MPa, argon gas is introduced into the furnace to 0MPa, and the vacuum pumping-argon gas is repeated Operation, start heating when the pressure in the furnace is about 1MPa; when the tube furnace starts to heat, flow argon into the furnace, continue to heat up to 1100°C, keep it warm for two hours, and finally cool down.

Its further technical solution is that when heating, the temperature rise rate is 5°C/min, and when cooling, the temperature drop rate is 5°C/min down to 500°C, and then cooled with the furnace.

Its further technical scheme is, in step S3, the powder body that sintering completes will boil 30 to 60 minutes, and wash more than four times with deionized water.

Its further technical solution is that in step S1, the molar mass ratio of silicon carbide and metal yttrium is 2-5:1-4.

Its further technical solution is that the metal salt is at least one selected from sodium chloride, potassium chloride, lithium chloride, and calcium chloride.

Preferably, the metal salt is selected from any two of sodium chloride, potassium chloride, lithium chloride and calcium chloride.

More preferably, the metal salt is selected from sodium chloride and potassium chloride, and the molar mass ratio of the two is 1-4:8-32.

More preferably, the metal salt is selected from lithium chloride and calcium chloride, and the molar mass ratio of the two is 1-4:8-32.

It should be noted that the presence of salt will affect the performance of the final ceramics. Therefore, when preparing the non-oxide sintering aid Y ₃ Si ₂ C ₂ , the metal salt should be a low-melting metal salt, which can be boiled, etc. removed so as not to remain in the product.

In the second aspect, the present invention also provides the application of a non-oxide sintering aid Y ₃ Si ₂ C ₂ as a ceramic sintering aid, and the non-oxide sintering aid Y ₃ Si ₂ C ₂ is described in the first aspect The preparation method of the non-oxide sintering aid Y ₃ Si ₂ C ₂ is prepared.

In a third aspect, the present invention provides a method for preparing a high-performance silicon nitride ceramic substrate, which is characterized in that it includes the following steps:

T1. In parts by weight, grind 90-100 parts of silicon nitride, 0-10 parts of non-oxide Y ₃ Si ₂ C ₂ sintering aid, and 0-10 parts of rare earth oxide, and mix them uniformly to obtain a mixed powder body;

T2. Put the mixed powder into a dry pressing mold, compact it to obtain an embryo body, and put the embryo body into a boron nitride crucible;

T3. Place the boron nitride crucible in the furnace cavity, raise the pressure of the furnace body from 0MPa to 0.3-0.8MPa, fix the graphite mold, and carry out vacuum pressure sintering. After the sintering is completed, a high-performance silicon nitride ceramic substrate is obtained;

Wherein, the non-oxide sintering aid Y ₃ Si ₂ C ₂ is prepared by the preparation method of the non-oxide sintering aid Y ₃ Si ₂ C ₂ described in the first aspect.

Specifically, in the mixed powder in step T1, the non-oxide Y ₃ Si ₂ C ₂ sintering aid is 0-10 parts, such as 0 parts, 1 part, 3 parts, 5 parts, 7 parts, 9 parts, 10 parts; 0-10 parts of rare earth oxides, such as 0 parts, 1 part, 3 parts, 5 parts, 7 parts, 9 parts, 10 parts.

Specifically, the silicon nitride is made of high-purity silicon nitride powder, the α-phase weight percentage is greater than 83, the particle size is preferably 0.3-10 μm, and the distribution is unimodal.

Specifically, the impurity content of the non-oxide sintering aid Y ₃ Si ₂ C ₂ does not exceed 0.07%.

Specifically, the mold used for molding is a dry pressing mold, and its size depends on the size of the ceramic substrate.

Specifically, in step T2, the mixed powder is put into a dry pressing mold, and the powder is compacted by a hydraulic press with a pressure of 5-15 MPa.

Specifically, the sintering furnace used for vacuum pressure sintering in the present invention is a vacuum pressure sintering furnace.

Its further technical solution is that in step T3, the vacuum pressure sintering operation is, when the vacuum degree in the furnace body reaches 100Pa, nitrogen gas is introduced into the furnace to 1-3MPa, and the vacuum pumping-nitrogen gas operation is repeated until the pressure in the furnace reaches 1-3 MPa. Start heating when the temperature is below 0.01Pa; when the temperature in the furnace is lower than 800°C, fill the furnace with nitrogen, continue to raise the temperature to 1800-2000°C, and finally cool down and lower the pressure.

Its further technical solution is that when heating, when the temperature rises from 600-900°C to 1300-1600°C, nitrogen gas is introduced until the pressure in the furnace is 1 atmosphere, and the flowing nitrogen atmosphere is maintained, and the flow pressure of nitrogen gas is controlled at 1-3Mpa ;When the temperature rises to 1450-1750°C, keep it warm for 1-3h; when the temperature rises from 1450-1750°C to 1800-2000°C, keep the nitrogen pressure in the furnace constant, then keep it warm for 8-12h, then cool down and reduce the pressure.

Its further technical solution is that when cooling down, when the temperature drops from 1600-2000°C to 1100-1300°C, the cooling rate is 8-20°C/min; Decrease from 1-3MPa to 0MPa; then cool down to below 40-60°C with the furnace, take out the mold, and obtain a sintered high-performance silicon nitride ceramic substrate.

Its further technical solution is that the rare earth oxide is one or more of magnesium oxide, yttrium oxide, and ytterbium oxide; magnesium oxide and yttrium oxide are preferred, and the particle size is preferably 1-20 μm.

Its further technical solution is that in step T1, the specific operation of grinding is to add absolute ethanol to the raw material for planetary ball grinding, and the grinding medium is silicon nitride balls, wherein silicon nitride balls: absolute ethanol: weight of raw materials The ratio is 2-5:1-5:1, the ball milling time is 6-12h; the ball milling speed is 250-500r/min.

Specifically, the silicon nitride balls used for grinding are silicon nitride balls with three different ball diameters, which are 3-5mm, 7-9mm, and 10-15mm respectively; the mass ratio of the three silicon nitride balls is 1-4: 1-2:1.

Specifically, the ball-to-material mass ratio during grinding is preferably 3:1.

In a fourth aspect, the present invention also provides a high-performance silicon nitride ceramic substrate, which is prepared by the method for preparing a high-performance silicon nitride ceramic substrate described in the third aspect.

The principles involved in the present invention include: pressure sintering is to apply a certain gas pressure while heating, usually nitrogen, and the pressure range is 1-10MPa, so as to suppress the decomposition and weight loss of ceramics at high temperatures, thereby increasing the temperature, so compared to For pressureless sintering, air pressure sintering can significantly increase the sintering temperature, which can make the contact between grains closer, and the content of pores is less, so that the silicon nitride ceramics are densified, and the preparation performance is better at a lower cost, and the shape is complex. products and achieve mass production.

Sintering aids such as non-oxide sintering aids Y ₃ Si ₂ C ₂ and rare earth oxides can form a low-melting point eutectic with silicon nitride powder at high temperature, and play a role in liquid phase sintering, thereby promoting the matrix The densification behavior also reduces the sintering temperature and holding time, as well as the content of oxygen impurities, inhibits the formation of large-sized silicon nitride crystals, and improves the flexural strength of ceramic materials.

Compared with the prior art, the technical effects that the present invention can achieve include:

The preparation method of the non-oxide sintering aid Y ₃ Si ₂ C ₂ provided by the present invention uses silicon carbide and metal yttrium as the main raw materials, supplemented by metal salts, prepared by molten salt method, and introduces low melting point in conventional solid phase reaction A new synthetic method of using salt as a flux to synthesize non-oxide Y ₃ Si ₂ C ₂ can obtain a non-oxide Y ₃ Si ₂ C ₂ sintering aid. Traditional sintering aids usually use two or more rare earth oxides to improve the thermal conductivity of silicon nitride ceramics, but this will increase the introduction of oxygen impurities, which will affect the thermal conductivity instead. The non-oxide sintering aid Y ₃ Si ₂ C ₂ prepared by the method of the present invention can be added to silicon nitride ceramic raw materials as a sintering aid to significantly reduce the influence of oxygen impurities on the thermal conductivity of silicon nitride ceramics.

The preparation method of the high-performance silicon nitride ceramic substrate provided by the present invention uses non-oxide sintering aids Y ₃ Si ₂ C ₂ and rare earth oxides as sintering aids, and its addition helps to reduce the oxygen content of oxide sintering aids. The introduction of impurities promotes sintering density; the selected sintering aid can react with oxygen impurities to purify the crystal lattice and effectively improve thermal conductivity. The preparation method of the present invention is a vacuum thermal sintering method. Under the action of furnace pressure and flowing nitrogen atmosphere, it is beneficial to the formation of silicon nitride, further promotes the densification of sintering, and can effectively reduce the size of crystal grains, thereby improving The flexural strength of ceramics.

In summary, the high-performance silicon nitride ceramic substrate prepared by the vacuum pressure sintering method provided by the present invention is prepared by the vacuum pressure sintering method by matching the sintering aid of rare earth oxide and non-oxide sintering aid Y ₃ Si ₂ C ₂ Silicon nitride ceramic substrate, the performance of the obtained ceramic substrate is greatly improved, the thermal conductivity can reach 90W·m ^-1 ·K ^-1 , the strength can reach 860MPa, and the density can be calculated according to the principle of Archimedes by boiling water. 99.7%.

Description of drawings

Fig. 1 is an XRD pattern of the non-oxide sintering aid Y ₃ Si ₂ C ₂ prepared in Example 1 of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention, and similar component numbers in the drawings represent similar components. Apparently, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

It should be understood that when used in this specification and the appended claims, the terms "comprising" and "comprises" indicate the presence of described features, integers, steps, operations, elements and/or components, but do not exclude one or Presence or addition of multiple other features, integers, steps, operations, elements, components and/or collections thereof.

It should also be understood that the terms used in the description of the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention. As used in the description of the embodiments of the present invention and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly dictates otherwise.

Example 1

This example provides a non-oxide sintering aid Y ₃ Si ₂ C ₂ prepared by vacuum pressure sintering method and the corresponding preparation method:

Silicon carbide powder is used as the standard raw material, plus metal yttrium with a molar mass ratio of 3:2 to silicon carbide, and then sodium chloride and potassium chloride with a molar mass ratio of 1:8. The volume ratio of silicon carbide and metal yttrium to sodium chloride and potassium chloride is 1:2, put them into a grinding bowl and grind them, and mix them uniformly to obtain a mixed powder;

Put the mixed powder into the alumina crucible and cover the crucible to prevent the furnace cavity from being polluted by bumping;

Put the alumina crucible in the corundum tube of the tube furnace, and sinter the tube furnace in a vacuum inert atmosphere: when the vacuum degree in the furnace reaches -0.1MPa, feed argon into the furnace to 0 MPa, and repeat vacuuming-argon Gas operation, start heating when the pressure in the furnace is about 1MPa; when the tube furnace starts to heat, flow argon into the furnace, the temperature rise rate is 5°C/min and the temperature is raised to 1100°C, kept for two hours, and then cooled The rate is 5°C/min down to 500°C, and then cooled with the furnace, that is, the sintering is completed.

Boil the sintered product with deionized water for 40 minutes, wash it with deionized water for 4-5 times, and dry it in a 60°C oven to remove the added metal salt.

The XRD of the non-oxide sintering aid Y ₃ Si ₂ C ₂ prepared by the above process is shown in Figure 1.

Example 2

Silicon carbide powder is used as the reference raw material, metal yttrium with a molar mass ratio of 4:2 to silicon carbide is added, and sodium chloride and potassium chloride with a molar mass ratio of 1:17 are added. The volume ratio of silicon carbide and metal yttrium to sodium chloride and potassium chloride is 1:4, put them into a grinding bowl and grind them, and mix them uniformly to obtain a mixed powder;

Example 3

Silicon carbide powder is used as the standard raw material, plus metal yttrium with a molar mass ratio of 5:2 to silicon carbide, and then lithium chloride and calcium chloride with a molar mass ratio of 3:26. The volume ratio of silicon carbide and metal yttrium to lithium chloride and calcium chloride is 1:7, put them into a grinding bowl and grind them, and mix them uniformly to obtain a mixed powder;

Example 4

This embodiment provides a high-performance silicon nitride ceramic substrate prepared by a vacuum pressure sintering method and a corresponding preparation method:

(1) Using silicon nitride as the standard raw material, add 3wt% non-oxide sintering aid Y ₃ Si ₂ C ₂ obtained in Example 1, 5wt% yttrium oxide for grinding, and mix uniformly. The specific operation of grinding is to add absolute ethanol to the raw material for planetary ball milling, the grinding medium is silicon nitride balls, wherein the weight ratio of silicon nitride balls: absolute ethanol: raw materials is 3:3:1, and the ball milling time is 6h; the ball milling speed is 300r/min.

(2) Put the mixed powder into a dry pressing mold, compact the powder with a hydraulic pressure of 10 MPa to obtain an embryo body, and put it into a boron nitride crucible;

(3) Place the boron nitride crucible in the furnace cavity, increase the pressure of the furnace body from 0MPa to 0.3-0.8MPa, fix the graphite mold, and carry out vacuum pressure sintering: when the vacuum degree in the furnace body reaches 100Pa, the Introduce nitrogen to 1-3MPa, repeat the vacuum pumping-nitrogen operation, and start heating when the pressure in the furnace is below 0.01Pa; Atmospheric pressure, and maintain a flowing nitrogen atmosphere, the nitrogen flow pressure is controlled at 1-3Mpa; when the temperature rises to 1450-1750°C, keep it warm for 1-3h; when the temperature rises from 1450-1750°C to 1800-2000°C, the furnace body The nitrogen pressure was kept constant, followed by heat preservation for 8-12h, then cooling and depressurization. When cooling down, when the temperature drops from 1600-2000°C to 1100-1300°C, the cooling rate is 8-20°C/min; at the same time, in the 10-40min of cooling, the nitrogen pressure of the furnace body is reduced from 1-3MPa to 0MPa ; Then cool down to room temperature with the furnace, take out the mold, and obtain a sintered high-performance silicon nitride ceramic substrate.

The thermal conductivity of silicon nitride ceramics prepared by the above process can reach 90W·m ^-1 ·K ^-1 , the strength is 860MPa, and the density is 99.7% calculated according to the principle of Archimedes by using the method of boiling water.

Example 5

(1) Using silicon nitride as the standard raw material, add 3wt% of the non-oxide sintering aid Y ₃ Si ₂ C ₂ obtained in Example 1, and 5wt% of magnesium oxide for grinding and uniform mixing. The specific operation of grinding is to add absolute ethanol to the raw material for planetary ball milling, the grinding medium is silicon nitride balls, wherein the weight ratio of silicon nitride balls: absolute ethanol: raw materials is 3:3:1, and the ball milling time is 6h; the ball milling speed is 300r/min.

The thermal conductivity of the silicon nitride ceramics prepared by the above process can reach 87W·m ^-1 ·K ^-1 , the strength is 893MPa, and the density is calculated to be 97.5% by the method of boiling water according to the Archimedes principle.

Example 6

(1) Using silicon nitride as the standard raw material, add 3wt% of the non-oxide sintering aid Y ₃ Si ₂ C ₂ obtained in Example 1, and 5wt% of ytterbium oxide for grinding and mixing evenly. The specific operation of grinding is to add absolute ethanol to the raw material for planetary ball milling, the grinding medium is silicon nitride balls, wherein the weight ratio of silicon nitride balls: absolute ethanol: raw materials is 3:3:1, and the ball milling time is 6h; the ball milling speed is 300r/min.

The thermal conductivity of silicon nitride ceramics prepared by the above process can reach 83W·m ^-1 ·K ^-1 , the strength is 882MPa, and the density is 98.1% calculated according to the principle of Archimedes by using boiling water method.

Example 7

(1) Using silicon nitride as a standard raw material, adding 3wt% magnesium oxide for grinding and mixing evenly. The specific operation of grinding is to add absolute ethanol to the raw material for planetary ball milling, the grinding medium is silicon nitride balls, wherein the weight ratio of silicon nitride balls: absolute ethanol: raw materials is 3:3:1, and the ball milling time is 6h; the ball milling speed is 300r/min.

The thermal conductivity of the silicon nitride ceramics prepared by the above process can reach 70W·m ^-1 ·K ^-1 , the strength is 882MPa, and the density is calculated to be 98.1% by the method of boiling water according to the principle of Archimedes.

In summary, the high-performance silicon nitride ceramic substrate prepared by the vacuum pressure sintering method provided by the present invention is combined with non-oxide sintering aids Y3Si2C2 and rare earth oxides as sintering aids, and the vacuum pressure sintering method is used to prepare silicon nitride ceramic substrates. The performance of the obtained ceramic substrate is greatly improved. By further adjusting the type and addition ratio of sintering aids, the thermal conductivity of the obtained ceramic substrate can reach 90W·m ^-1 ·K ^-1 , and the strength can reach 860MPa. 99.7%.

In the foregoing embodiments, the descriptions of each embodiment have their own emphases, and for parts not described in detail in a certain embodiment, reference may be made to relevant descriptions of other embodiments.

The above is a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of various equivalent modifications within the technical scope disclosed in the present invention. Or replacement, these modifications or replacements should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

A method for preparing a non-oxide sintering aid Y 3 Si 2 C 2 is characterized in that it comprises the following steps:

S1. Grinding the mixture of silicon carbide and metal yttrium and the metal salt in an agate grinding bowl at a volume ratio of 1:2-8, and mixing them uniformly to obtain a mixed powder;

S2. Put the mixed powder into an alumina crucible, and cover the crucible;

S3. Sintering the alumina crucible in a vacuumed inert atmosphere, and the non-oxide Y 3 Si 2 C 2 is obtained after the sintering is completed.
The preparation method of non-oxide sintering aid Y 3 Si 2 C 2 as claimed in claim 1, characterized in that, in step S3, the sintering operation in a vacuumed inert atmosphere is that when the vacuum degree in the furnace reaches -0.1MPa, Introduce argon gas into the furnace to 0MPa, repeat the vacuum pumping-argon gas operation, and start heating when the pressure in the furnace is about 1MPa; 1100°C, keep warm for two hours, and finally cool down.
The preparation method of non-oxide sintering aid Y 3 Si 2 C 2 as claimed in claim 2, characterized in that, when heating, the heating rate is 5°C/min, and when cooling, the cooling rate is 5°C/min down to 500°C, and then cooled with the furnace.
The preparation method of non-oxide sintering aid Y 3 Si 2 C 2 as claimed in claim 1, characterized in that in step S3, the sintered powder should be boiled for 30 to 60 minutes and washed with deionized water More than four times.
The preparation method of non-oxide sintering aid Y 3 Si 2 C 2 according to claim 1, characterized in that, in step S1, the molar mass ratio of silicon carbide and metal yttrium is 2-5:1-4.
The preparation method of non-oxide sintering aid Y 3 Si 2 C 2 as claimed in claim 1, wherein the metal salt is selected from sodium chloride, potassium chloride, lithium chloride, calcium chloride at least one.
An application of non-oxide Y 3 Si 2 C 2 as a ceramic sintering aid, the non-oxide sintering aid Y 3 Si 2 C 2 is composed of the non-oxide sintering aid described in any one of claims 1-6 The auxiliary agent Y 3 Si 2 C 2 is prepared by the preparation method.
A method for preparing a high-performance silicon nitride ceramic substrate, characterized in that it comprises the following steps:

T1. In parts by weight, grind 90-100 parts of silicon nitride, 0-10 parts of non-oxide Y 3 Si 2 C 2 sintering aid, and 0-10 parts of rare earth oxide, and mix them uniformly to obtain a mixed powder body;

T2, put the mixed powder into a dry pressing mold, compact it to obtain an embryo body, and put the embryo body into a boron nitride crucible;

T3. Place the boron nitride crucible in the furnace cavity, raise the pressure of the furnace body from 0MPa to 0.3-0.8MPa, fix the graphite mold, and carry out vacuum pressure sintering. After the sintering is completed, a high-performance silicon nitride ceramic substrate is obtained;

Wherein, the non-oxide sintering aid Y 3 Si 2 C 2 is prepared by the preparation method of the non-oxide sintering aid Y 3 Si 2 C 2 described in any one of claims 1-6.
The preparation method of high-performance silicon nitride ceramic substrate as claimed in claim 8, characterized in that, in step T3, the vacuum pressure sintering operation is, when the vacuum degree in the furnace body reaches 100Pa, nitrogen gas is introduced into the furnace to 1 -3MPa, repeat the vacuuming-nitrogen operation, and start heating when the pressure in the furnace is below 0.01Pa; when the temperature in the furnace is lower than 800°C, fill the furnace with nitrogen, continue to heat up to 1800-2000°C, and finally cool Buck.
A high-performance silicon nitride ceramic substrate, characterized in that it is prepared by the method for preparing a high-performance silicon nitride ceramic substrate according to any one of claims 8-9.