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CN-121974662-A - Preparation method of low dielectric loss alumina ceramic

CN121974662ACN 121974662 ACN121974662 ACN 121974662ACN-121974662-A

Abstract

The invention relates to the technical field of ceramic materials and discloses a preparation method of alumina ceramic with low dielectric loss, which comprises the steps of premixing a solvent, a dispersing agent, a sintering aid and a defoaming agent to obtain a premix; adding aluminum oxide raw powder into the premix, ball milling at a speed of 120-200 rpm, adding a lubricant and a binder, ball milling at a speed of 50-90 rpm to obtain slurry, sieving, removing iron and defoaming the slurry, spraying and granulating to obtain granulated powder, and molding and sintering the granulated powder to obtain aluminum oxide ceramic. The alumina ceramic obtained by the preparation method has lower dielectric loss and higher density and bending strength.

Inventors

  • WANG FU
  • MA YUQI
  • ZHANG WEN

Assignees

  • 浙江富乐德半导体材料科技有限公司

Dates

Publication Date
20260505
Application Date
20251113

Claims (10)

  1. 1. A method for preparing an alumina ceramic with low dielectric loss, which is characterized by comprising the following steps: s1, premixing a solvent, a dispersing agent, a sintering aid and a defoaming agent to obtain a premix; S2, adding aluminum oxide raw powder into the premix, performing ball milling at a rotating speed of 120-200 rpm, adding a lubricant and a binder, and performing ball milling at a rotating speed of 50-90 rpm to obtain slurry; S3, sieving, deironing and defoaming the slurry, and then spraying and granulating to obtain granulated powder; and S4, molding and sintering the granulated powder to obtain the alumina ceramic.
  2. 2. The method for preparing alumina ceramic according to claim 1, wherein in step S2, the time of ball milling at 120-200 rpm is 4-8 hours, and the time of ball milling at 50-90 rpm is 0.5-1.5 hours.
  3. 3. The method for preparing alumina ceramic according to claim 1, wherein in step S4, the sintering is performed in air, and the specific process comprises heating to 400-600 ℃ at 1-2 ℃ per min, maintaining the temperature for 3-6 hours, heating to 1200-1400 ℃ at 3-5 ℃ per min, maintaining the temperature for 3-5 hours, heating to 1500-1700 ℃ at 2-3 ℃ per min, and maintaining the temperature for 2-4 hours.
  4. 4. The method for preparing alumina ceramic according to claim 1, wherein in the steps S1 and S2, the amounts of the solvent, the binder, the dispersant, the lubricant, the defoamer and the sintering aid are 45-65%, 3-5%, 0.4-0.6%, 3.5-4.5%, 0.2-0.4% and 0.2-0.4% of the mass of the alumina raw powder, respectively.
  5. 5. The method for preparing alumina ceramic according to claim 1 or 4, wherein in step S2, the purity of the alumina raw powder is >99.7%, the Na element content is <100ppm, the fe element content is <100ppm, the specific surface area is 5-10 m 2 /g, the particle size D 50 =0.4-1.5 μm, in step S1, the solvent is pure water, the pH value is 6-7, and the conductivity is less than or equal to 10 μs/cm.
  6. 6. The method according to claim 1 or 4, wherein in step S1, the sintering aid is magnesium oxide and/or yttrium oxide, the dispersant is an ammonium polycarboxylate salt and/or an acrylic resin, and the antifoaming agent is at least one of silica, silicone, and silica mineral oil.
  7. 7. The method according to claim 1 or 4, wherein in the step S2, the binder is at least one of an acrylic resin, a polyvinyl alcohol, and a urethane-modified ether, and the lubricant is a fatty acid.
  8. 8. The method for preparing the alumina ceramic according to claim 1, wherein in the step S3, a 400-450 mesh nylon screen is adopted in the sieving process, the iron removal mode is that an iron remover with magnetic force of more than or equal to 12000GS is adopted for stirring for not less than 30min, and the deaeration mode is vacuum deaeration, and specifically comprises the steps of stirring for 1-1.5 hours at 20-40 rpm under the state that the vacuum degree reaches-0.09-0.1 MPa.
  9. 9. The method for preparing alumina ceramic according to claim 1, wherein in the step S3, the spray drying condition is that the air inlet temperature is 180-200 ℃, the air outlet temperature is 80-100 ℃, the rotation speed of an atomizer is 7000-9000 rpm, and the powder is obtained by sieving with a 60-80 mesh sieve after the spray drying is completed.
  10. 10. The method for preparing alumina ceramic according to claim 1, wherein in the step S4, the molding mode is cold isostatic pressing, and the conditions are a pressure increasing rate of 5-10 mpa/min, a molding pressure of 80-140 mpa, and a holding time of 20-40 min.

Description

Preparation method of low dielectric loss alumina ceramic Technical Field The invention relates to the technical field of ceramic materials, in particular to a preparation method of alumina ceramic with low dielectric loss. Background Alumina ceramics have been widely used in the fields of electronics, machinery, chemical industry, medical treatment, etc. by virtue of their high hardness, high temperature resistance, corrosion resistance, good insulation, etc. However, although the existing alumina ceramic can achieve lower dielectric loss at low frequency (for example, the dielectric loss of the alumina ceramic in patent CN114702306a can reach 1×10 -4 at the lowest at 1 MHz), when the alumina ceramic works at high frequency (for example, 13.56 MHz), microscopic defects inside the alumina ceramic are activated under the high-frequency alternating electric field, so that the phenomenon of dielectric loss improvement easily occurs, which causes the dielectric loss of the alumina ceramic to be higher when the alumina ceramic works at high frequency, resulting in signal attenuation and energy loss, and limiting the application of the alumina ceramic in high-frequency electronic devices. Dielectric losses are mainly due to impurity ions (such as Na +), pores and microstructural inhomogeneities in the ceramic. The low dielectric loss ceramic material has wide application prospect in the fields of high-frequency electronic devices, microwave communication, aerospace and the like due to excellent electrical performance, mechanical performance and thermal stability. Therefore, the development of a preparation method capable of effectively reducing dielectric loss of alumina ceramic has important significance. Disclosure of Invention In order to solve the technical problems, the invention provides a preparation method of alumina ceramic with low dielectric loss. By adopting the preparation method provided by the invention, the alumina ceramic with extremely low dielectric loss, high density and high bending strength can be obtained. The specific technical scheme of the invention is as follows: a preparation method of low dielectric loss alumina ceramic comprises the following steps: s1, premixing a solvent, a dispersing agent, a sintering aid and a defoaming agent to obtain a premix; S2, adding aluminum oxide raw powder into the premix, performing ball milling at a rotating speed of 120-200 rpm, adding a lubricant and a binder, and performing ball milling at a rotating speed of 50-90 rpm to obtain slurry; S3, sieving, deironing and defoaming the slurry, and then spraying and granulating to obtain granulated powder; and S4, molding and sintering the granulated powder to obtain the alumina ceramic. In the invention, the solvent, the dispersing agent, the sintering aid and the defoaming agent are premixed, the alumina raw powder is added for carrying out the first ball milling, and then the lubricant and the binder are added for carrying out the second ball milling, so that the specific feeding sequence and the design of the ball milling scheme can produce the following effects, thereby the finally prepared alumina ceramic has higher density, lower dielectric loss and higher bending strength: (1) The solvent, the dispersing agent, the sintering aid and the defoaming agent are pre-mixed before the raw alumina powder is added, so that the dispersing agent, the sintering aid and the defoaming agent can be fully dispersed in the solvent, and the raw alumina powder can better play a role, wherein the dispersing agent pre-dispersed in the solvent is beneficial to uniformly dispersing the raw alumina powder added subsequently, improving the stability of slurry, reducing the viscosity of the slurry and facilitating ball milling, and bubbles are easy to appear in the slurry during the raw alumina powder adding and ball milling process, and the foam can be better inhibited from forming during the subsequent raw alumina powder adding and ball milling process by fully dispersing the defoaming agent in the solvent in advance. (2) After the raw alumina powder is added, the particle size of the alumina powder in the slurry can be reduced by performing the first ball milling at a relatively high rotating speed (120-200 rpm), so that the bending strength of the alumina ceramic is improved. However, if the lubricant and the binder are added before the first ball milling, the effect of reducing the particle size of the alumina powder by the first ball milling is negatively affected, and therefore, after the first ball milling is finished, the lubricant and the binder are added, so that the slurry with smaller particle size is obtained, and better performance is given to the alumina ceramic. (3) In the first ball milling, the particle size of the alumina powder is relatively large, the viscosity of the slurry is relatively high, and in this case, the use of a relatively high ball milling rotation speed (120-200 rpm) is beneficial to reduci