High-purity ceramic substrate and ceramic substrate thereof

Abstract

The invention discloses a high-purity ceramic substrate and a preparation method thereof, and belongs to the technical field of ceramics. The preparation method of the high-purity ceramic substrate comprises the following steps: S01, mixing alumina powder with a rare earth element oxide compound, a sintering aid, a binder, a dispersant and water, and carrying out ball milling to obtain ceramic slurry; s02, vacuum defoaming is carried out; s03, tape casting, hot pressing and drying are carried out, and a ceramic basic green body is obtained; and S04, performing high-temperature sintering to obtain the high-purity ceramic substrate. The obtained ceramic substrate is good in heat-conducting property and fracture toughness, and can well meet the requirements of the electronic industry.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramics, and in particular relates to a high-purity ceramic substrate and a preparation method thereof. Background Art

[0002] Driven by the rapid development of cutting-edge technologies such as high-power integrated circuits, IGBT modules, LED technology, high-frequency communication equipment, LED lighting systems, new energy vehicles, high-speed railways, wind power generation and solar photovoltaic systems, the performance requirements for substrate packaging materials are constantly increasing. In these electronic devices, ceramic substrates play a core role. They not only need to provide solid support and protection for the devices, but also withstand the test of thermal stress during the heat dissipation process. In order to ensure the long-term stable operation of electronic equipment, the mechanical strength of the substrate must be high enough. Therefore, the development of ceramic substrate materials with both excellent thermal conductivity and good mechanical strength is crucial to meet the high standards of the current and future electronics industry.

[0003] Alumina ceramics, also known as bauxite ceramics or corundum ceramics, are a type of ceramic material made of aluminum oxide (Al2O3) as the main raw material. It has a variety of excellent physical and chemical properties, so it is widely used in industry and technology. Alumina ceramics are widely used in the electronics industry, mainly due to their excellent electrical insulation, high thermal conductivity, good mechanical strength and high temperature resistance. Alumina ceramics are widely used as substrate materials for integrated circuits (ICs) due to their high insulation and low dielectric constant, especially in high-frequency and high-speed electronic devices. Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for preparing a high-purity ceramic substrate. The obtained ceramic substrate has good thermal conductivity and fracture toughness, and can well meet the needs of the electronics industry.

[0005] The first aspect of the present invention is to disclose a method for preparing a high-purity ceramic substrate, comprising the following steps:

[0006] S01, mixing alumina powder with a rare earth element oxide composite, a sintering aid, a binder, a dispersant and water, and ball milling to obtain a ceramic slurry;

[0007] S02, vacuum degassing;

[0008] S03, tape casting, hot pressing and drying to obtain a basic ceramic green body;

[0009] S04, high temperature sintering to obtain a high-purity ceramic substrate.

[0010] In some embodiments of the present invention, in S01, the rare earth element oxide composite includes at least two rare earth element oxides whose rare earth element atomic numbers differ by more than 5.

[0011] In some embodiments of the present invention, in S01, the rare earth element oxide composite includes at least one of lanthanum trioxide and cerium dioxide,

[0012] and,

[0013] At least one of dysprosium dioxide and holmium trioxide.

[0014] Alumina powder, CeO2, Dy2O3, and magnesium oxide are all commercially available products with a purity greater than 99.0% and a median particle size D50 of 0.5-0.8 μm.

[0015] In some embodiments of the present invention, in S01, in the rare earth element oxide composite, the weight ratio of the rare earth element oxide with a high atomic number to the rare earth element oxide with a low atomic number is (2-6):(0.5-2), preferably (4-6):2.

[0016] In some embodiments of the present invention, in S01, the weight ratio of the aluminum oxide powder to the rare earth element oxide composite is (65-85):(3-10), preferably (70-80):(6-8).

[0017] In some embodiments of the present invention, in S01, the weight ratio of the alumina powder to the sintering aid, the binder, the dispersant and the water is (70-80): (1-3): (6-10): (1-3): (100-200).

[0018] In some embodiments of the present invention, in S01, the ball-to-material ratio is (1-3):1, the rotation speed is 200-400 r / min, and the mixing time is 4-8 h.

[0019] In some embodiments of the present invention, in S02, the vacuum degree is 0.3-0.6 MPa, the stirring speed is 100-200 r / min, and the stirring time is 10-20 min.

[0020] In some embodiments of the present invention, in S03, the speed of the casting machine is 0.5-5 cm / s.

[0021] In some embodiments of the present invention, in S04, the temperature is kept at 500-700°C for 3-5 hours, and then the temperature is increased to 1200-1500°C and kept for 1-3 hours.

[0022] In some embodiments of the present invention, the particle sizes of alumina powder (α-Al2O3) and magnesium oxide are both 0.5≤D90≤0.8μm. The particle sizes of CeO2 and Dy2O3 particles are both 1μm≤D90≤5μm. It was found in the study that when the particle size of alumina powder is D50>20μm, the viscosity of the slurry increases and the casting speed needs to be greatly increased. At the same time, the cooling speed after high-temperature sintering also needs to be reduced, otherwise, if it is too fast, it will easily affect the mechanical properties of the finished ceramic.

[0023] The second aspect of the present invention is to disclose a high-purity ceramic substrate obtained by the preparation method described in the first aspect.

[0024] Beneficial effects:

[0025] The high-purity ceramic substrate prepared by the present invention has excellent fracture toughness and thermal conductivity, overcomes the shortcomings of high brittleness and low thermal conductivity of general ceramics, and can be well used as a substrate for electronic components and related equipment.

[0026] The preparation method of the high-purity ceramic substrate of the present invention has simple steps and fast speed, and is prepared by adding rare earth element oxide composites of specific components and proportions. Different from general rare earth oxides, the fine powders of cerium dioxide, dysprosium dioxide and aluminum oxide increase the contact between silicon carbide particles, improve the green body density and promote densification. More importantly, the synergistic wetting and capillary forces promote particle rearrangement and pore filling, enhance density, optimize grain growth and grain boundary structure, reduce stress concentration, thereby improving toughness, reducing grain boundary scattering, improving heat conduction efficiency, and significantly improving the performance of the obtained high-purity ceramic substrate.

[0027] In the preparation method of the high-purity ceramic substrate of the present invention, when optimizing the rare earth element components, it is found that the effect of the rare earth element oxide composite is related to the difference in the atomic numbers of the two rare earth elements, which may be related to the size of the atomic radius. It is speculated that only the oxides of the two rare earth elements with a sufficiently large difference in atomic radius can have an ideal effect on grain growth and grain boundary structure. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] In the following examples and comparative examples, the particle sizes of alumina powder (α-Al2O3) and magnesium oxide are 0.5≤D90≤0.8 μm. The particle sizes of CeO2 and Dy2O3 particles are 1 μm≤D90≤5 μm.

[0030] Unless otherwise specified, the examples and comparative examples are parallel tests with the same parameters such as components, component contents, preparation steps, preparation parameters, and dimensions.

[0031] Example 1

[0032] A method for preparing a high-purity ceramic substrate:

[0033] (1) 75 parts of alumina, 5 parts of CeO2, 2 parts of Dy2O3, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0034] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0035] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0036] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0037] Example 2

[0038] A method for preparing a high-purity ceramic substrate:

[0039] (1) By weight, 75 parts of aluminum oxide, 4 parts of CeO2, 2 parts of Dy2O3, 1 part of sintering aid magnesium oxide, 10 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 3:1, the rotation speed was 300 r / min, and the mixing time was 4 h;

[0040] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0041] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0042] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the temperature is kept at 650° C. for 3 hours, and then the temperature is increased to 1400° C. and kept at this temperature for 2 hours.

[0043] Example 3

[0044] A method for preparing a high-purity ceramic substrate:

[0045] (1) By weight, 75 parts of alumina, 6 parts of CeO2, 2 parts of Dy2O3, 3 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 3 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0046] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0047] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0048] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1300° C. and kept at this temperature for 4 hours.

[0049] Example 4

[0050] A method for preparing a high-purity ceramic substrate:

[0051] (1) 75 parts of aluminum oxide, 5 parts of CeO2, 0.5 parts of Dy2O3, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0052] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0053] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0054] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0055] Example 5

[0056] A method for preparing a high-purity ceramic substrate:

[0057] (1) 75 parts of alumina, 3 parts of CeO2, 2 parts of Dy2O3, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0058] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0059] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0060] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0061] Example 6

[0062] A method for preparing a high-purity ceramic substrate:

[0063] (1) By weight, 75 parts of alumina, 2 parts of CeO2, 1 part of Dy2O3, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0064] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0065] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0066] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0067] Example 7

[0068] A method for preparing a high-purity ceramic substrate:

[0069] (1) 75 parts of aluminum oxide, 5 parts of CeO2, 2 parts of La2O3, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0070] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0071] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0072] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0073] Example 8

[0074] A method for preparing a high-purity ceramic substrate:

[0075] (1) 75 parts of aluminum oxide, 5 parts of Ho2O3, 2 parts of Dy2O3, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0076] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0077] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0078] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0079] Comparative Example 1

[0080] A method for preparing a high-purity ceramic substrate:

[0081] (1) 75 parts of aluminum oxide, 7 parts of CeO2, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0082] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0083] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0084] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0085] Comparative Example 2

[0086] A method for preparing a high-purity ceramic substrate:

[0087] (1) 75 parts of aluminum oxide, 7 parts of Dy2O3, 2 parts of sintering aid magnesium oxide, 8 parts of PVA binder and 2 parts of sodium dodecyl sulfate dispersant were added to a ball mill, 150 parts of deionized water were added, and agate balls were used as ball milling media to obtain a ceramic slurry; wherein the ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h;

[0088] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0089] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0090] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0091] Comparative Example 3

[0092] A method for preparing a high-purity ceramic substrate:

[0093] (1) 75 parts of aluminum oxide, 2 parts of magnesium oxide as a sintering aid, 8 parts of a PVA binder, and 2 parts of a sodium dodecyl sulfate dispersant were added to a ball mill, and 150 parts of deionized water were added. Agate balls were used as ball milling media, and the ceramic slurry was obtained by ball milling. The ball-to-material ratio was 2:1, the rotation speed was 300 r / min, and the mixing time was 6 h.

[0094] (2) stirring in a vacuum sealed tank for vacuum defoaming treatment; wherein the vacuum degree is 0.5 MPa, the stirring speed is 150 r / min, and the stirring time is 15 min;

[0095] (3) Using a metal sheet substrate, the slurry is injected into a tape casting machine, the slurry flows out from the lower part of the hopper onto the metal sheet, and is coated with a scraper, and then hot-pressed and dried to form a high-purity ceramic substrate green body; wherein the scraper height is 2 mm, and the speed of the tape casting machine is 2 cm / s;

[0096] (4) placing the crucible into a high-temperature sintering furnace to obtain a high-purity ceramic substrate; wherein, the substrate is kept at 600° C. for 4 hours, and then heated to 1400° C. and kept at this temperature for 2 hours.

[0097] Experimental Example Performance Test

[0098] The high-purity ceramic substrates obtained in the examples and comparative examples were taken as samples for performance testing.

[0099] 1 Mechanical properties

[0100] Hardness: First, polish the test sample into a mirror surface, and then use a microhardness tester to pressurize the surface with a load of 1 kg and hold it for 10 seconds to measure the Vickers hardness of the sample.

[0101] The results show that the hardness of the high-purity ceramic substrates obtained in Examples 1-6 is all above 10.0, which meets the requirements of the general electronics industry.

[0102] Fracture toughness:

[0103] When testing fracture toughness, after measuring the Vickers hardness of the sample, the fracture toughness k of the ceramic sample is calculated based on the measured crack length. Where M is the load. C is the half length of the crack. β is 68°. The results are shown in Table 1.

[0104] Table 1 Fracture toughness of ceramics

[0105] <![CDATA[Fracture toughness / MPa·m 1 / 2 > Example 1 4.2 Example 2 3.9 Example 3 3.8 Example 4 3.6 Example 5 3.6 Example 6 3.5 Example 7 3.2 Example 8 3.3 Comparative Example 1 3.2 Comparative Example 2 3.1 Comparative Example 3 2.9

[0106] The results show that compared with the comparative example 3 without adding the rare earth element oxide composite auxiliary material, the fracture toughness of the ceramic substrate obtained in Examples 1-6 is significantly improved. Although the rare earth element oxide composite auxiliary materials Examples 8 and 9, which respectively add lanthanum trioxide and cerium dioxide and dysprosium dioxide and holmium trioxide, are slightly improved compared with the comparative example 3, they are not much different from the comparative examples 1 and 2 in which only one rare earth element oxide is added, and the improvement is limited. The fracture toughness of Examples 1-3 is significantly better than that of Examples 4, 5 and 6, among which Example 1 is the best. This shows that in addition to the components, the content of the components also significantly affects the fracture toughness of the obtained ceramic substrate.

[0107] 2 Thermal conductivity

[0108] The thermal conductivity test is to first polish the surface of the test sample to a roughness of 0.5 μm, and then use a laser thermal conductivity meter to measure its thermal conductivity at room temperature.

[0109] The results show that the high-purity ceramic substrates obtained in Examples 1-6 are all below 30W·m -1 ·k -1 The above meets the requirements of general electronics industry.

[0110] The preferred specific implementation modes and embodiments of the present invention are described in detail above, but the present invention is not limited to the above implementation modes and embodiments, and various changes can be made within the knowledge scope of those skilled in the art without departing from the concept of the present invention.

Claims

1. A method for preparing a high-purity ceramic substrate, characterized in that: The following steps are involved: S01, mixing alumina powder with a rare earth element oxide composite, a sintering aid, a binder, a dispersant and water, and ball milling to obtain a ceramic slurry; S02, vacuum degassing; S03, tape casting, hot pressing and drying to obtain a basic ceramic green body; S04, high temperature sintering to obtain a high-purity ceramic substrate.

2. The method for preparing a high-purity ceramic substrate according to claim 1, characterized in that: In S01, the rare earth element oxide composite includes at least two rare earth element oxides whose atomic numbers differ by more than 5.

3. The method for preparing a high-purity ceramic substrate according to claim 1 or 2, characterized in that: In S01, the rare earth element oxide composite includes at least one of lanthanum trioxide and cerium dioxide, and, At least one of dysprosium dioxide and holmium trioxide.

4. The method for preparing a high-purity ceramic substrate according to claims 1-3, characterized in that: In S01, in the rare earth element oxide composite, the weight ratio of the rare earth element oxide with a high atomic number to the rare earth element oxide with a low atomic number is (2-6):(0.5-2), preferably (4-6):

2.

5. The method for preparing a high-purity ceramic substrate according to any one of claims 1 to 4, characterized in that: In S01, the weight ratio of the aluminum oxide powder to the rare earth element oxide composite is (65-85):(3-10), preferably (70-80):(6-8); In S01, the weight ratio of the alumina powder to the sintering aid, the binder, the dispersant and the water is (70-80):(1-3):(6-10):(1-3):(100-200).

6. The method for preparing a high-purity ceramic substrate according to any one of claims 1 to 5, characterized in that: In S01, the ball-to-material ratio is (1-3):1, the rotation speed is 200-400r / min, and the mixing time is 4-8h.

7. The method for preparing a high-purity ceramic substrate according to any one of claims 1 to 6, characterized in that: In S02, the vacuum degree is 0.3-0.6MPa, the stirring speed is 100-200r / min, and the stirring time is 10-20min.

8. The method for preparing a high-purity ceramic substrate according to any one of claims 1 to 7, characterized in that: In S03, the speed of the casting machine is 0.5-5 cm / s.

9. The method for preparing a high-purity ceramic substrate according to any one of claims 1 to 8, characterized in that: In S04, keep the temperature at 500-700℃ for 3-5h, increase the temperature to 1200-1500℃ and keep the temperature for 1-3h.

10. A high-purity ceramic substrate obtained by the preparation method according to any one of claims 1 to 9.