Alumina ceramic and preparation method thereof

Abstract

The invention provides aluminum oxide ceramic and a preparation method thereof, and belongs to the technical field of ceramic, the aluminum oxide ceramic comprises the following raw materials in percentage by mass: 75-95% of aluminum oxide, 4-15% of a sintering aid and 1-10% of an organic substance, and a dispersing agent, the powder I comprises the following components in percentage by mass: 90-96% of aluminum oxide, 4-15% of a sintering aid and 1-10% of an organic substance, and the dispersing agent comprises the following components in percentage by mass: 1-10% of a dispersing agent. 2.5%-8.5% of a sintering aid, 0.5%-5% of a rare metal additive and 1%-7% of an organic substance; by designing and adjusting the proportion of two or more ceramic raw material granulation powder, the reflectivity of the surface of the device is adjusted, and the reflectivity of the surface of the ceramic device is increased to 95% or more from conventional 85%-92%.

Description

Technical Field

[0001] The invention relates to the technical field of ceramics, and in particular to an alumina ceramic and a preparation method thereof. Background Art

[0002] Highly reflective materials are widely used in the field of optical products. The high reflectivity of the material surface allows light to be reused many times to improve the utilization rate of light energy. Due to its thermal conductivity and insulation material properties, ceramics are increasingly used as optical reflective devices in the LED field. Common ceramic high-reflective optical devices are formed and sintered in one go using a single ceramic material with rare metal oxides as additives, and the price of rare metal oxides is generally high. Therefore, how to improve the preparation method and obtain ceramics with high reflectivity while reducing the amount of rare metal oxides or not adding rare metal oxides is a technical problem that needs to be solved urgently. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an alumina ceramic and a preparation method thereof, which are used to solve the problem in the prior art that a high reflectivity of the ceramic surface can only be achieved by adding a high proportion of rare metal oxides.

[0004] In order to achieve the above-mentioned object and other related objects, the present invention provides an alumina ceramic, wherein the raw materials of the alumina ceramic include:

[0005] Powder 1: by mass percentage, alumina 75% to 95%, sintering aid 4% to 15%, organic matter 1% to 10%;

[0006] Powder 2: by mass percentage, 90% to 96% alumina, 2.5% to 8.5% sintering aid, 0.5% to 5% rare metal additive, 1% to 7% organic matter;

[0007] Also included are dispersants;

[0008] The organic substances in the powder 1 and the powder 2 are independently selected from one or more of starch, ammonium polymethacrylate, polymethyl methacrylate, polyethylene, polypropylene, polyvinyl alcohol and polyethylene glycol.

[0009] The present invention also provides a method for preparing the alumina ceramic as described above, comprising the following steps:

[0010] S1, wet ball milling the components in powder 1 and the dispersant, and spray granulating the slurry after ball milling to obtain powder 1;

[0011] S2, wet ball milling the components in the second powder with a dispersant, and spray granulating the slurry after ball milling to obtain the second powder;

[0012] S3, mixing powder material 1, powder material 2 and a dispersant evenly, pressing into shape, and sintering to obtain alumina ceramics.

[0013] As described above, the alumina ceramics and the preparation method thereof of the present invention have the following beneficial effects:

[0014] The alumina ceramic of the present invention mainly includes powder one and powder two. Powder one includes alumina, a sintering aid, and an organic substance. Powder two includes alumina, a sintering aid, a rare metal additive, and an organic substance. The present invention adjusts the reflectivity of the device surface by designing and adjusting the ratio of two or more ceramic raw material granulation powders, thereby increasing the reflectivity of the ceramic device surface from the conventional 85% to 92% to 95% or above.

[0015] In the preparation method of alumina ceramics of the present invention, powder one and powder two are spray granulated separately and then mixed, pressed, formed and sintered. Compared with ceramic devices made of granulated powders obtained by traditional liquid homogeneous mixed spray granulation, when the same materials are input, the solid mixture of two or more granulated powders of different ceramic raw materials has a higher reflectivity than the granulated powder of liquid homogeneous liquid phase mixture. DETAILED DESCRIPTION

[0016] 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.

[0017] When a numerical range is disclosed herein, the above range is deemed to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. For example, a specified range from "1 to 10" should be deemed to include any and all sub-ranges between a minimum of 1 and a maximum of 10. Exemplary sub-ranges of ranges 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, and the like.

[0018] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; and, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0019] A first aspect of the present invention provides an alumina ceramic, wherein the raw materials of the alumina ceramic include:

[0020] Powder 1: by mass percentage, alumina 75%-95%, 75%-80%, 80%-85%, 85%-90%, 90%-95%, sintering aid 4%-15%, 4%-6%, 6%-8%, 8%-10%, 10%-12% or 12%-15%, organic matter 1%-10%, 1%-2%, 2%-4%, 4%-6%, 6%-8% or 8%-10%;

[0021] Powder 2: by mass percentage, alumina 90%-96%, 90%-92%, 92%-94% or 94%-96%, sintering aid 2.5%-8.5%, 2.5%-3.5%, 3.5%-4.5%, 4.5%-5.5%, 5.5%-6.5%, 6.5%-7.5% or 7.5%-8.5%, rare metal additive 0.5%-5%, 0.5%-1%, 1%-2%, 2%-3%, 3%-4% or 4%-5%, organic matter 1%-7%, 1%-2%, 2%-4%, 4%-6% or 6%-7%;

[0022] Also included are dispersants;

[0023] The organic substances in the powder 1 and the powder 2 are independently selected from one or more of starch, ammonium polymethacrylate, polymethyl methacrylate, polyethylene, polypropylene, polyvinyl alcohol and polyethylene glycol.

[0024] In the alumina ceramics of the present invention, the sintering aids in the powders one and two are respectively selected from one or more of silicon micropowder, zinc oxide, titanium dioxide, magnesium oxide, magnesium carbonate, calcium carbonate and barium carbonate.

[0025] In the alumina ceramics of the present invention, the rare metal additive is selected from one or more of zirconium oxide, yttrium oxide and lanthanum oxide.

[0026] In the alumina ceramics of the present invention, the dispersant is selected from one or more of polyacrylic acid ammine, polyvinyl alcohol, polyethylene glycol, oleic acid, stearic acid, dodecylbenzenesulfonic acid ammine, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate.

[0027] In the alumina ceramic of the present invention, the ratio of the total mass of the powder 1 and the powder 2 to the dispersant is 100:(0.5-1.5), for example, 100:(0.5-0.7), 100:(0.7-0.9), 100:(0.9-1.1), 100:(1.1-1.3) or 100:(1.3-1.5).

[0028] A second aspect of the present invention provides a method for preparing the alumina ceramic as described above, comprising the following steps:

[0029] S1, wet ball milling the components in powder 1 and the dispersant, and spray granulating the slurry after ball milling to obtain powder 1;

[0030] S2, wet ball milling the components in the second powder with a dispersant, and spray granulating the slurry after ball milling to obtain the second powder;

[0031] S3, mixing powder material 1, powder material 2 and a dispersant evenly, pressing into shape, and sintering to obtain alumina ceramics.

[0032] In the method for preparing alumina ceramics of the present invention, the solvent for wet ball milling in step S1 and step S2 is water. The mass ratio of water added to the material is 45 to 65:100, for example, 45 to 50:100, 50 to 55:100, 55 to 60:100 or 60 to 65:100.

[0033] In the preparation method of alumina ceramics of the present invention, the wet ball milling in step S1 and step S2 is first ball milling at 30-40 Hz, 30-35 Hz or 35-40 Hz for 30-40 h, 30-32 h, 32-34 h, 34-36 h, 36-38 h or 38-40 h, and then ball milling at 15-25 Hz, 15-20 Hz or 20-25 Hz for 0.5-1 h, 0.5-0.7 h, 0.7-0.9 h or 0.9-1 h.

[0034] In the method for preparing alumina ceramics of the present invention, the mass ratio of powder 1 to powder 2 in step S3 is 3:7-1:9, for example, 3:7-1:3, 1:3-1:4, 1:4-1:5, 1:5-1:6, 1:6-1:7, 1:7-1:8 or 1:8-1:9.

[0035] In the method for preparing alumina ceramics of the present invention, the sintering temperature in step S3 is 1400-1600° C. For example, 1400-1420° C., 1420-1440° C., 1440-1460° C., 1460-1480° C., 1480-1500° C., 1500-1520° C., 1520-1540° C., 1540-1560° C., 1560-1580° C. or 1580-1600° C.

[0036] In the method for preparing alumina ceramics of the present invention, the sintering time in step S3 is 6 to 12 hours, for example, 6 to 7 hours, 7 to 8 hours, 8 to 9 hours, 9 to 10 hours, 10 to 11 hours or 11 to 12 hours.

[0037] Example 1

[0038] Preparation of an alumina ceramic:

[0039] S1. Preparation of powder material 1: 50 parts of water (the total raw materials except water is 100 parts) are added to a ball mill; 91.5% of aluminum oxide, 4% of silicon powder, and 3% of calcium carbonate are added by mass percentage, the ball mill is started at a speed of 40 Hz for 30 hours, and then 1.5% of polyvinyl alcohol aqueous solution is added and the ball milling is continued at a speed of 20 Hz for 0.5 hours, and the milled slurry is pumped into a granulation tower for spray granulation to obtain powder material 1;

[0040] S2, preparation of powder material 2: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 94.5% of aluminum oxide, 1.5% of silicon powder, 1.5% of calcium carbonate, and 1.5% of lanthanum oxide by mass percentage, start the ball mill and mill at 40 Hz for 30 hours, then add 1% of polyvinyl alcohol aqueous solution and continue to mill at 15 Hz for 1 hour, and pump the milled slurry into a granulation tower for spray granulation to obtain powder material 2;

[0041] S3. Mechanically stir and mix powder one and powder two in proportions (10:0, 8:2, 5:5, 2:8, 0:10) respectively, and add stearic acid in an amount of 1.5% of the total weight of powder one and powder two before mechanical stirring and mixing, and mix for 30 minutes; after mixing, use a mold to dry-press the powder into a green body of the ceramic device, and place the green body in a sintering furnace at 1600°C and sinter for 6 hours to obtain alumina ceramics.

[0042] The thickness of the sintered ceramic components is 1.0 mm.

[0043] The reflectivity (SCI value was tested by a colorimeter) and thermal conductivity (referenced to ASTM E1461-2013 standard test method for thermal diffusivity by flash method) of the alumina ceramic device prepared in Example 1 were measured. The results are shown in Table 1:

[0044] Table 1

[0045]

[0046]

[0047] From the data in Table 1, it can be seen that as the proportion of powder 2 in the total powder increases, the reflectivity shows an upward trend, and reaches a peak when the ratio of powder 1: powder 2 is close to 2:8; as the proportion of powder 2 in the total powder continues to increase, the reflectivity shows a downward trend.

[0048] Example 2

[0049] Preparation of an alumina ceramic:

[0050] S1. Preparation of powder material 1: add 65 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 91.5% of aluminum oxide, 3% of silicon powder, 3% of calcium carbonate, and 1% of barium carbonate by mass percentage, start the ball mill and mill at 30 Hz for 40 hours, then add 1.5% of polyvinyl alcohol aqueous solution and continue to mill at 15 Hz for 1 hour, and pump the milled slurry into a granulation tower for spray granulation to obtain powder material 1;

[0051] S2, preparation of powder material 2: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 94% of aluminum oxide, 2% of silicon powder, 1% of barium carbonate, and 1.5% of lanthanum oxide by mass percentage, start the ball mill and mill at 30 Hz for 40 hours, then add 1% of polyvinyl alcohol and 0.5% of polyethylene glycol aqueous solution and continue to mill at 15 Hz for 1 hour, and pump the milled slurry into a granulation tower for spray granulation to obtain powder material 2;

[0052] S3. Mechanically stir and mix powder one and powder two in a ratio of 2:8, and add stearic acid in an amount of 1.5% of the total weight of powder one and powder two before mechanical stirring and mixing, and mix for 30 minutes; after mixing, use a mold to dry-press the powder into a green body of a ceramic device, and place the green body in a sintering furnace at 1600°C and sinter for 6 hours to obtain alumina ceramics.

[0053] Example 3

[0054] Preparation of an alumina ceramic:

[0055] S1. Preparation of powder material 1: 50 parts of water (the total raw materials except water is 100 parts) are added to a ball mill; 85% of aluminum oxide, 8.5% of silicon powder, 2% of calcium carbonate, and 3% of barium carbonate are added by mass percentage, the ball mill is started to mill at a speed of 40 Hz for 30 hours, and then 1.5% of polyvinyl alcohol aqueous solution is added and the ball milling is continued at a speed of 20 Hz for 0.5 hours, and the milled slurry is pumped into a granulation tower for spray granulation to obtain powder material 1;

[0056] S2, preparation of powder material 2: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 94.5% of aluminum oxide, 1.5% of silicon powder, 1.5% of calcium carbonate, and 1.5% of lanthanum oxide by mass percentage, start the ball mill and mill at 40 Hz for 30 hours, then add 1% of polyvinyl alcohol aqueous solution and continue to mill at 15 Hz for 1 hour, and pump the milled slurry into a granulation tower for spray granulation to obtain powder material 2;

[0057] S3. Mechanically stir and mix powder one and powder two in a ratio of 3:7, and add 1.5% of the total weight of powder one and powder two of polyoxyethylene sorbitan monolaurate before mechanical stirring and mixing, and mix for 30 minutes; after mixing, use a mold to dry-press the powder into a green body of the ceramic device, and place the green body in a sintering furnace at 1500°C and sinter for 8 hours to obtain alumina ceramics.

[0058] Example 4

[0059] Preparation of an alumina ceramic:

[0060] S1. Preparation of powder material 1: 50 parts of water (the total raw materials except water is 100 parts) are added to a ball mill; 91.5% of aluminum oxide, 4% of silicon powder, and 3% of calcium carbonate are added by mass percentage, and the ball mill is started at a speed of 40 Hz for 30 hours, and then 1% of polyvinyl alcohol and 0.5% of polyethylene glycol aqueous solution are added and the ball milling is continued at a speed of 20 Hz for 0.5 hours, and the slurry after ball milling is pumped into a granulation tower for spray granulation to obtain powder material 1;

[0061] S2, preparation of powder material 2: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 93.5% of aluminum oxide, 1.5% of silicon powder, 1.5% of calcium carbonate, 1% of lanthanum oxide, and 1.5% of zirconium oxide by mass percentage, start the ball mill and mill at 40 Hz for 30 hours, then add 1% of polyvinyl alcohol aqueous solution and continue to mill at 15 Hz for 1 hour, and pump the milled slurry into a granulation tower for spray granulation to obtain powder material 2;

[0062] S3. Mechanically stir and mix powder one and powder two in a ratio of 2:8, and add stearic acid in an amount of 1.5% of the total weight of powder one and powder two before mechanical stirring and mixing, and mix for 30 minutes; after mixing, use a mold to dry-press the powder into a green body of a ceramic device, and place the green body in a sintering furnace at 1560°C and sinter for 7 hours to obtain alumina ceramics.

[0063] Example 5

[0064] Preparation of an alumina ceramic:

[0065] S1. Preparation of powder material 1: 45 parts of water (the total raw materials except water are 100 parts) are added to a ball mill; 75% of aluminum oxide, 12% of silicon powder, 2% of calcium carbonate, 1.5% of barium carbonate, and 7% of magnesium oxide are added in percentage by mass, and the ball mill is started to mill at a speed of 40 Hz for 30 hours, and then 1.5% of polyvinyl alcohol and 1% of polymethacrylic acid ammonia solution are added and the ball milling is continued at a speed of 20 Hz for 0.5 hours, and the milled slurry is pumped into a granulation tower for spray granulation to obtain powder material 1;

[0066] S2, preparation of powder material 2: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 96% of aluminum oxide, 1% of silicon powder, 1% of calcium carbonate, 0.5% of lanthanum oxide, and 0.5% of zirconium oxide by mass percentage, start the ball mill and mill at 40 Hz for 30 hours, then add 1% of polyvinyl alcohol aqueous solution and continue to mill at 15 Hz for 1 hour, and pump the milled slurry into a granulation tower for spray granulation to obtain powder material 2;

[0067] S3. Mechanically stir and mix powder one and powder two in a ratio of 3:7, and add stearic acid in an amount of 1.5% of the total weight of powder one and powder two before mechanical stirring and mixing, and mix for 30 minutes; after mixing, use a mold to dry-press the powder into a green body of a ceramic device, and place the green body in a sintering furnace at 1400°C and sinter for 12 hours to obtain alumina ceramics.

[0068] The thickness of the ceramic components after sintering in Examples 2 to 5 is 1.0 mm.

[0069] The reflectivity and thermal conductivity of the alumina ceramic devices prepared in Examples 2 to 5 were compared with those in Examples 1 to 4. The results are shown in Table 2:

[0070] Table 2

[0071]

[0072] Comparative Example 1

[0073] Preparation of an alumina ceramic:

[0074] S1. Preparation of slurry 1: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 91.5% of aluminum oxide, 4% of silicon powder, and 3% of calcium carbonate by mass percentage, start the ball mill at 40 Hz for 30 hours, then add 1.5% of polyvinyl alcohol aqueous solution and continue to ball mill at 20 Hz for 0.5 hours, pump the milled slurry into a container and slowly stir for standby use, which is slurry 1;

[0075] S2. Preparation of slurry 2: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 94.5% of aluminum oxide, 1.5% of silicon powder, 1.5% of calcium carbonate, and 1.5% of lanthanum oxide by mass percentage, start the ball mill at 40 Hz for 30 hours, then add 1% of the total weight of the powder polyvinyl alcohol aqueous solution and continue to ball mill at 15 Hz for 1 hour, pump the milled slurry into a container and slowly stir for standby use, which is slurry 2;

[0076] S3, mechanically stirring and mixing slurry 1 and slurry 2 in a ratio of 8:2, 5:5, and 2:8 for 1 hour, and the mixed slurries are pumped into a granulation tower for spray granulation;

[0077] S4. Use a mold to dry-press a green body of the ceramic device, place the green body in a sintering furnace at 1600° C. and sinter for 6 hours to obtain alumina ceramics.

[0078] The thickness of the sintered ceramic components is 1.0 mm.

[0079] The reflectivity and thermal conductivity of the alumina ceramic device prepared in Comparative Example 1 were measured, and the results are shown in Table 2.

[0080] Table 3

[0081] unit Comparative Example 1-1 Comparative Example 1-2 Comparative Examples 1-3 Powder 1: Powder 2 8：2 5：5 2：8 Reflectivity ％ 89.42 93.65 94.48 Thermal conductivity W / (mk) 23.85 24.68 25.21

[0082] It can be seen from the data in Table 3 that compared with Example 1, the reflectivity of the alumina ceramic prepared by directly mixing the slurry, spraying granulating, and then dry pressing the slurry into a mold is reduced.

[0083] Comparative Example 2

[0084] Preparation of an alumina ceramic:

[0085] S1. Preparation of powder material 1: 50 parts of water (the total raw materials except water is 100 parts) are added to a ball mill; 91.5% of aluminum oxide, 4% of silicon powder, and 3% of calcium carbonate are added by mass percentage, the ball mill is started at a speed of 40 Hz for 30 hours, and then 1.5% of polyvinyl alcohol aqueous solution is added and the ball milling is continued at a speed of 20 Hz for 0.5 hours, and the milled slurry is pumped into a granulation tower for spray granulation to obtain powder material 1;

[0086] S2, preparation of powder material 2: add 50 parts of water (the total raw materials except water is 100 parts) into a ball mill; add 94.5% of aluminum oxide, 1.5% of silicon powder, 1.5% of calcium carbonate, and 1.5% of lanthanum oxide by mass percentage, start the ball mill and mill at 40 Hz for 30 hours, then add 1% of polyvinyl alcohol aqueous solution and continue to mill at 20 Hz for 0.5 hours, and pump the milled slurry into a granulation tower for spray granulation to obtain powder material 2;

[0087] S3. Powder 1 and powder 2 are mechanically stirred and mixed in a ratio of 10:0, 8:2, 5:5, 2:8, and 0:10, respectively. The mixed powders are dry-pressed into a green body of a ceramic device using a mold, and the green body is placed in a sintering furnace at 1600° C. and sintered for 2 hours to obtain alumina ceramics.

[0088] The thickness of the sintered ceramic components is 1.0 mm.

[0089] The reflectivity and thermal conductivity of the alumina ceramic device prepared in Comparative Example 2 were measured, and the results are shown in Table 4.

[0090] Table 4

[0091]

[0092] It can be seen from the data in Table 4 that compared with Example 1, the sintering time of the green body of Comparative Example 2 is shortened, the reflectivity of the single-component ceramic is increased, and the reflectivity of the mixed-component ceramic is reduced.

[0093] It can be seen from Tables 1 to 4 in combination with Example 1 and Comparative Examples 1 to 2 that, compared with ceramic devices made of granulated powder obtained by spray granulation after homogeneous mixing of traditional liquid slurry, when the same materials are input, the solid mixture of two or more granulated powders of different ceramic raw materials has a higher reflectivity than the granulated powder obtained by liquid homogeneous liquid phase mixing.

[0094] In summary, the present invention utilizes the design and matching of two or more ceramic raw material granulation powders and a matching sintering method to make the surface of the ceramic device have a higher reflectivity, from the conventional 85% to 92% reflectivity to 95% and above, while achieving the goal of improving light utilization without sacrificing heat dissipation performance and reducing material costs.

[0095] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0096] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An alumina ceramic, characterized in that: The raw materials of the alumina ceramics include: Powder 1: by mass percentage, aluminum oxide 75% to 95%, sintering aid 4% to 15%, organic matter 1% to 10%; Powder 2: by mass percentage, aluminum oxide 90% to 96%, sintering aid 2.5% to 8.5%, rare metal additives 0.5% to 5%, organic matter 1% to 7%; Also included are dispersants; The organic substances in the powder 1 and the powder 2 are independently selected from one or more of starch, ammonium polymethacrylate, polymethyl methacrylate, polyethylene, polypropylene, polyvinyl alcohol and polyethylene glycol.

2. The alumina ceramic according to claim 1, characterized in that: The sintering aids in the powder one and the powder two are respectively selected from one or more of silicon micropowder, zinc oxide, titanium dioxide, magnesium oxide, magnesium carbonate, calcium carbonate and barium carbonate.

3. The alumina ceramic according to claim 1, characterized in that: The rare metal additive is selected from one or more of zirconium oxide, yttrium oxide and lanthanum oxide.

4. The alumina ceramic according to claim 1, characterized in that: The dispersant is selected from one or more of polyacrylic acid ammonium, polyvinyl alcohol, polyethylene glycol, oleic acid, stearic acid, dodecylbenzenesulfonic acid ammonium, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate.

5. The alumina ceramic according to claim 1, characterized in that: The ratio of the total mass of the powder 1 and the powder 2 to the dispersant is 100:(0.5-1.5).

6. A method for preparing an alumina ceramic according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, wet ball milling the components in powder 1 and the dispersant, and spray granulating the slurry after ball milling to obtain powder 1; S2, wet ball milling the components in the second powder with a dispersant, and spray granulating the slurry after ball milling to obtain the second powder; S3, mixing powder material 1, powder material 2 and a dispersant evenly, pressing into shape, and sintering to obtain alumina ceramics.

7. The method for preparing alumina ceramics according to claim 6, characterized in that: The solvent for wet ball milling in step S1 and step S2 is water; And / or, the wet ball milling in step S1 and step S2 is first ball milling at 30-40 Hz for 30-40 h, and then ball milling at 15-25 Hz for 0.5-1 h.

8. The method for preparing alumina ceramics according to claim 6, characterized in that: In step S3, the mass ratio of powder 1 to powder 2 is 3:7 to 1:

9.

9. The method for preparing alumina ceramics according to claim 6, characterized in that: The sintering temperature in step S3 is 1400-1600°C.

10. The method for preparing alumina ceramics according to claim 6, characterized in that: The sintering time in step S3 is 6 to 12 hours.

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