Preparation method of low-dielectric ceramic material ultrafine particles for 6G

Abstract

The invention discloses a preparation method of low-dielectric ceramic material ultrafine particles for 6G, relates to the technical field of dielectric ceramic materials, and belongs to the patent classification number C04B35 / 00. The specific preparation method comprises the following steps: firstly, preparing sol from tetraethoxysilane, calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride and lithium nitrate, heating and standing the sol for gelatinization, then drying by adopting supercritical CO2 to obtain aerogel, heating, reducing and calcining to obtain (Ca, Mg) SiO3-ZrO2 nano powder, coating the surface of the nano powder with a TiO2 layer by adopting an atomic layer deposition technology, and drying to obtain the (Ca, Mg) SiO3-ZrO2 nano powder. The dielectric ceramic material ultrafine particles are obtained. The prepared ceramic particles are low in dielectric constant, small in particle size and high in compactness under low-temperature sintering.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric ceramic materials, and the patent classification number is C04B35 / 00. Specifically, it is a preparation method for ultrafine particles of low-dielectric ceramic materials for 6G. Background Art

[0002] As communication technology advances towards the 6G era, more stringent requirements are imposed on the performance of low-dielectric ceramic materials. In the existing technology, there are many deficiencies in some low-dielectric ceramic materials for 6G. For example, some low-dielectric ceramic materials mainly composed of calcium silicate have large signal losses when operating in a 6G high-frequency environment, resulting in serious signal attenuation, which greatly affects the quality and efficiency of signal transmission and is difficult to meet the requirements of high-speed and stable communication in 6G.

[0003] From the perspective of the microstructure of the material, the particle size in the current ceramic powder is relatively large, which limits the preparation of ultra-thin dielectric layers. When a dielectric layer with a thickness less than or equal to 5um needs to be prepared, the existing ceramic materials cannot achieve such fine processing due to their large particle size, thus restricting the development of related electronic devices towards miniaturization and lightness, and unable to meet the pursuit of miniaturization and high performance in 6G communication devices.

[0004] In addition, during the low-temperature sintering process, the ceramic material is prone to looseness, resulting in an insufficiently dense internal structure, which in turn affects the overall performance of the material. If the sintering temperature is increased, although the densification of the ceramic can be improved, the relatively inexpensive metal silver cannot be used as the electrode material. Because the melting point of silver is relatively low, high-temperature sintering will cause the silver electrode to melt or undergo other physical and chemical changes, and it cannot play its due electrode role, which not only increases the cost of the material but also hinders the preparation and application of subsequent devices.

[0005] In summary, the existing low-dielectric ceramic materials for 6G have obvious defects in terms of high-frequency loss, particle size, and sintering characteristics, and there is an urgent need to develop a new preparation method to improve these problems in order to promote the development of 6G communication technology. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method for ultrafine particles of low-dielectric ceramic materials for 6G to solve the technical problems raised in the above background art. The ceramic particles prepared by the present invention not only have a low dielectric constant but also have a small particle size and a high density under low-temperature sintering.

[0007] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method for ultrafine particles of low-dielectric ceramic materials for 6G, comprising the following steps: S1. Mix tetraethyl orthosilicate with absolute ethanol and stir evenly to obtain a uniform silicon precursor solution; dissolve calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride and lithium nitrate in absolute ethanol, stir until completely dissolved to obtain a mixed solution, mix the silicon precursor solution with the mixed solution, then add citric acid and graphene quantum dots, and disperse them evenly by ultrasonic oscillation to obtain a sol; S2. Transfer the sol to a high-pressure reactor, heat and let it stand for gelation, and then use supercritical CO2 drying to obtain an aerogel; S3. Place the aerogel in a tubular furnace, introduce a mixed gas of H2 and Ar, heat for reduction calcination, and then cool to obtain (Ca,Mg)SiO3-ZrO2 nanometer powder; S4. Coat a TiO2 layer on the surface of the (Ca,Mg)SiO3-ZrO2 nanometer powder by atomic layer deposition technology, and then crystallize the TiO2 layer by heating annealing to obtain ultrafine particles of dielectric ceramic materials.

[0008] In the technical solution of the present invention, (Ca,Mg)SiO3-ZrO2 composite material is used as the matrix. (Ca,Mg)SiO3 represents a calcium magnesium silicate solid solution, in which magnesium partially replaces calcium to form a new material with excellent dielectric properties. The introduction of magnesium not only reduces the dielectric constant of the material (εᵣ≤5.8), but also reduces the dielectric loss (tanδ≤1.2×10 -4 ), which benefits from the substitution effect of magnesium ions in the lattice. It can reduce the energy loss caused by lattice vibration, similar to installing shock absorbers inside the material, effectively reducing the energy loss during signal transmission. In addition, the introduction of ZrO2 further optimizes the performance of the material. As a high-performance oxide, ZrO2 has excellent dielectric properties and thermal stability. Introducing ZrO2 into the (Ca,Mg)SiO3 matrix not only reduces the dielectric constant of the material, but also enhances the mechanical strength and thermal stability of the material. The addition of ZrO2 is like adding a strong protective shell to the material, enabling it to maintain good performance under high temperature and harsh environments.

[0009] Citric acid plays an important role in the preparation of the sol. As a complexing agent, citric acid can form stable complexes with metal ions (such as Ca 2+ 、Mg 2+ etc.). On the one hand, it can adjust the pH value of the solution to an appropriate range, ensure the stability of the sol system, prevent metal ions from precipitating or aggregating in the solution, and make each component evenly dispersed in the solution, laying a foundation for the subsequent formation of a uniform gel structure; on the other hand, citric acid helps to promote the hydrolysis and polycondensation reactions of metal ions, enabling the sol to be more smoothly transformed into a gel, and thus providing a guarantee for preparing powders with uniform particle size and stable performance.

[0010] By adding graphene quantum dots and adopting the supercritical drying process, the powder particles are refined to ≤100 nm. The graphene quantum dots, like an "anti-caking agent", effectively prevent the particles from agglomerating and growing larger. In combination with the supercritical drying technology, the gel avoids the problem of particle agglomeration caused by the rapid volatilization of the solvent during the drying process, and finally obtains a powder with fine particle size and uniform distribution. This improvement enables the preparation of an ultra-thin dielectric layer (≤5 μm), greatly reducing the volume of the device and meeting the strict requirements for miniaturization in 6G communication.

[0011] Through the combination of calcination in a reducing atmosphere and a nano-TiO₂ coating, the present invention achieves low-temperature sintering below 850 °C, and the ceramic density reaches ≥98%. The calcination in a reducing atmosphere uses a mixed gas of hydrogen and argon to eliminate the adverse effects of air on the sintering process and simultaneously activates the sintering activity of the powder; the nano-TiO₂ coating (coated by atomic layer deposition) forms a liquid phase during sintering, helping the particles to "adhere" more tightly and making the ceramic material more dense. This not only ensures the density of the material but also improves the stability of its mechanical properties and dielectric properties.

[0012] Preferably, in the step S1, the mass ratio of tetraethyl orthosilicate, calcium nitrate, and magnesium nitrate is 1:0.4:0.6.

[0013] Preferably, in the step S1, the addition amount of graphene quantum dots is 0.01 - 0.05% of the mass of tetraethyl orthosilicate.

[0014] Preferably, in the step S2, the heating temperature is 40 - 50 °C, and the standing time is 18 - 24 h.

[0015] Preferably, in the step S3, the volume ratio of H₂ and Ar is 5:95.

[0016] Preferably, in the step S3, the calcination temperature is 700 - 750 °C, and the time is 1 - 2 h.

[0017] Preferably, in the step S4, the precursors used in the atomic layer deposition process are TiCl₄ and H₂O.

[0018] Preferably, in the atomic layer deposition process, the thickness of the TiO₂ layer deposited in a single deposition cycle is 0.1 nm; The single deposition cycle process is as follows: (1) The pulse time of TiCl₄ is 0.1 s, and the N₂ purge time is 20 s; (2) The pulse time of H₂O is 0.05 s, and the N₂ purge time is 30 s.

[0019] Preferably, the number of deposition cycles is 28 - 34 times.

[0020] In the technical solution of the present invention, the selection of the deposition cycle times is crucial for achieving ideal density and dielectric properties. In order to achieve high density of the material, the research team of the present invention determined that at least 28 deposition cycles are required. However, during the experiment, the research and development team unexpectedly found that when the deposition times exceeded 34 times, the dielectric loss of the material suddenly increased significantly, which was unexpected by the research and development team. After in-depth research, the reason for this problem is that the too thick coating layer leads to more interface defects, including pores, cracks and irregular surface morphologies. The existence of these defects will capture charges, thereby increasing the energy loss and resulting in an increase in dielectric loss. Therefore, the present invention strictly controls the deposition cycle times between 28 and 34 times, so that the material has both ideal density and dielectric properties.

[0021] Preferably, in step S4, the annealing temperature is 600-610 °C and the annealing time is 2-3 h.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: Using (Ca,Mg)SiO3-ZrO2 composite material as the matrix, forming a solid solution by partially replacing calcium with magnesium, effectively reducing the dielectric constant and dielectric loss of the material; the introduction of ZrO2 further optimizes the material properties, enhances the mechanical strength and thermal stability, and ensures that the material can still maintain good performance in a complex environment; Citric acid, as a complexing agent, plays an important role in the preparation of the sol, adjusts the pH value of the solution and promotes the hydrolysis and polycondensation reaction of metal ions, ensuring the stability of the sol system; the addition of graphene quantum dots and the supercritical drying process act synergistically to achieve the refinement of powder particles, and then an ultra-thin dielectric layer can be prepared to meet the miniaturization requirements of 6G communication; By combining calcination in a reducing atmosphere and a nano-TiO2 coating, low-temperature sintering is achieved, and the density of the ceramic material is increased; at the same time, the deposition cycle times are strictly controlled to avoid an increase in dielectric loss caused by interface defects due to too thick a coating layer, so that the material has both ideal density and dielectric properties. Specific embodiments

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Embodiment

[0024] A method for preparing ultrafine particles of a low-dielectric ceramic material for 6G, comprising the following steps: Step 1: Preparation of sol Use a precision balance to accurately weigh 208g of tetraethyl orthosilicate (TEOS) and transfer it to a 2000mL beaker. Use a measuring cylinder to measure 300mL of anhydrous ethanol and slowly add it to the beaker containing TEOS. Place the beaker on a mechanical stirrer and stir at 500rpm for 30 minutes until a uniform silicon precursor solution is formed.

[0025] Weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride and 20g of lithium nitrate respectively using a precision balance. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride and lithium nitrate into a 1000mL beaker in sequence, and then add 400mL of anhydrous ethanol. Place the beaker on a magnetic stirrer and stir until all substances are completely dissolved to obtain a mixed solution.

[0026] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Use a precision balance to weigh 5.8g of citric acid, add it to the mixed solution, and stir evenly. Weigh 0.04% of the mass of ethyl orthosilicate graphene quantum dots and add them to the above solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at a frequency of 40kHz for 15 minutes to obtain a uniform sol.

[0027] Step 2: Gelation and supercritical drying The prepared sol was transferred to a 5L high-pressure reactor, and the reactor was well sealed. The reactor was placed in a constant temperature water bath at 45°C for 23 hours to allow the sol to fully gel.

[0028] After gelation is completed, the reactor is connected to a supercritical CO2 drying system. The temperature of the drying system is set to 40°C and the pressure is set to 10 MPa. CO2 fluid is continuously introduced for 6 hours for drying. After drying, the pressure is slowly released to obtain a white block aerogel.

[0029] Step 3: Reduction Calcination The obtained aerogel was placed in a corundum crucible, and then the crucible was placed in the center of a tube furnace. High-purity nitrogen was introduced for 30 minutes to exhaust the air in the tube furnace. Then it was switched to a mixed gas of H2 and Ar, where the volume ratio of H2 to Ar was 5:95, and the gas flow rate was controlled at 50 mL / min.

[0030] The tube furnace was heated to 725°C at a heating rate of 5°C / min and kept at this temperature for 1.5 hours. After the heat preservation, the tube furnace was cooled to room temperature to obtain (Ca, Mg)SiO3-ZrO2 nanopowder.

[0031] Step 4: Atomic layer deposition coating and annealing Weigh 50 g of (Ca,Mg)SiO3-ZrO2 nanometer powder and put it into the reaction chamber of the atomic layer deposition equipment. Set the temperature of the reaction chamber to 120 °C. Use TiCl4 and H2O as precursors for atomic layer deposition. The specific deposition cycle process is as follows: Set the pulse time of TiCl4 to 0.1 second, and then conduct N2 purge for 20 seconds; set the pulse time of H2O to 0.05 second, and then conduct N2 purge for 30 seconds. The thickness of the TiO2 layer for a single deposition cycle is 0.1 nm. Repeat the above cycle process 32 times to coat the TiO2 layer on the surface of the powder.

[0032] After the deposition is completed, transfer the powder into a muffle furnace and anneal it at 605 °C for 2.5 hours to obtain ultrafine particles of the low-dielectric ceramic material. Example

[0033] A preparation method for ultrafine particles of a low-dielectric ceramic material for 6G includes the following steps: Step 1: Sol preparation Accurately weigh 208 g of tetraethyl orthosilicate (TEOS) using a precision balance and transfer it to a 2000 mL beaker. Measure 300 mL of absolute ethanol using a measuring cylinder and slowly add it to the beaker containing TEOS. Place the beaker on a mechanical stirrer and stir at a speed of 500 rpm for 30 minutes until a uniform silicon precursor solution is formed.

[0034] Weigh 83.2 g of calcium nitrate, 124.8 g of magnesium nitrate, 30 g of aluminum isopropoxide, 16 g of zirconium oxychloride, and 20 g of lithium nitrate using a precision balance respectively. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate to a 1000 mL beaker in sequence, and then add 400 mL of absolute ethanol. Place the beaker on a magnetic stirrer and stir until all substances are completely dissolved to obtain a mixed solution.

[0035] Slowly add the above-prepared mixed solution to the silicon precursor solution while stirring. Weigh 5.8 g of citric acid using a precision balance and add it to the mixed solution, and stir evenly. Weigh graphene quantum dots accounting for 0.02% of the mass of tetraethyl orthosilicate and add them to the above solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at a frequency of 40 kHz for 15 minutes to obtain a uniform sol.

[0036] Step 2: Gelation and supercritical drying Transfer the prepared sol to a 5 L high-pressure reactor and ensure that the reactor is sealed well. Place the reactor in a constant temperature water bath at 45 °C and let it stand for 20 hours to fully gelate the sol.

[0037] After gelation is completed, the reactor is connected to a supercritical CO2 drying system. The temperature of the drying system is set to 40°C and the pressure is set to 10 MPa. CO2 fluid is continuously introduced for 6 hours for drying. After drying, the pressure is slowly released to obtain a white block aerogel.

[0038] Step 3: Reduction Calcination The obtained aerogel was placed in a corundum crucible, and then the crucible was placed in the center of a tube furnace. High-purity nitrogen was introduced for 30 minutes to exhaust the air in the tube furnace. Then it was switched to a mixed gas of H2 and Ar, where the volume ratio of H2 to Ar was 5:95, and the gas flow rate was controlled at 50 mL / min.

[0039] The tube furnace was heated to 725°C at a heating rate of 5°C / min and kept at this temperature for 1.5 hours. After the heat preservation, the tube furnace was cooled to room temperature to obtain (Ca, Mg)SiO3-ZrO2 nanopowder.

[0040] Step 4: Atomic layer deposition coating and annealing Weigh 50g (Ca, Mg) SiO3-ZrO2 nanopowder into the reaction chamber of the atomic layer deposition equipment, and set the reaction chamber temperature to 120°C. Use TiCl4 and H2O as precursors for atomic layer deposition. The specific deposition cycle is as follows: the TiCl4 pulse time is set to 0.1 seconds, followed by N2 purge, and the purge time is 20 seconds; the H2O pulse time is set to 0.05 seconds, followed by N2 purge, and the purge time is 30 seconds. The thickness of the TiO2 layer in a single deposition cycle is 0.1nm. Repeat the above cycle 29 times to coat the TiO2 layer on the powder surface.

[0041] After the deposition is completed, the powder is transferred into a muffle furnace and annealed at 605°C for 2.5 hours to obtain ultrafine particles of low dielectric ceramic material. Example

[0042] A method for preparing ultrafine particles of low dielectric ceramic material for 6G, comprising the following steps: Step 1: Sol preparation Use a precision balance to accurately weigh 208g of tetraethyl orthosilicate (TEOS) and transfer it to a 2000mL beaker. Use a measuring cylinder to measure 300mL of anhydrous ethanol and slowly add it to the beaker containing TEOS. Place the beaker on a mechanical stirrer and stir at 500rpm for 30 minutes until a uniform silicon precursor solution is formed.

[0043] Weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride and 20g of lithium nitrate respectively using a precision balance. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride and lithium nitrate into a 1000mL beaker in sequence, and then add 400mL of anhydrous ethanol. Place the beaker on a magnetic stirrer and stir until all substances are completely dissolved to obtain a mixed solution.

[0044] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Use a precision balance to weigh 5.8g of citric acid, add it to the mixed solution, and stir evenly. Weigh 0.03% of the mass of ethyl orthosilicate graphene quantum dots and add them to the above solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at a frequency of 40kHz for 15 minutes to obtain a uniform sol.

[0045] Step 2: Gelation and supercritical drying The prepared sol was transferred to a 5L high-pressure reactor, and the reactor was well sealed. The reactor was placed in a constant temperature water bath at 45°C for 22 hours to allow the sol to fully gel.

[0046] After gelation is completed, the reactor is connected to a supercritical CO2 drying system. The temperature of the drying system is set to 40°C and the pressure is set to 10 MPa. CO2 fluid is continuously introduced for 6 hours for drying. After drying, the pressure is slowly released to obtain a white block aerogel.

[0047] Step 3: Reduction Calcination The obtained aerogel was placed in a corundum crucible, and then the crucible was placed in the center of a tube furnace. High-purity nitrogen was introduced for 30 minutes to exhaust the air in the tube furnace. Then it was switched to a mixed gas of H2 and Ar, where the volume ratio of H2 to Ar was 5:95, and the gas flow rate was controlled at 50 mL / min.

[0048] The tube furnace was heated to 725°C at a heating rate of 5°C / min and kept at this temperature for 1.5 hours. After the heat preservation, the tube furnace was cooled to room temperature to obtain (Ca, Mg)SiO3-ZrO2 nanopowder.

[0049] Step 4: Atomic layer deposition coating and annealing Weigh 50 g of (Ca,Mg)SiO3-ZrO2 nanometer powder and put it into the reaction chamber of the atomic layer deposition equipment. Set the temperature of the reaction chamber to 120 °C. Use TiCl4 and H2O as precursors for atomic layer deposition. The specific deposition cycle process is as follows: Set the TiCl4 pulse time to 0.1 second, and then perform N2 purge for 20 seconds; set the H2O pulse time to 0.05 second, and then perform N2 purge for 30 seconds. The thickness of the TiO2 layer for a single deposition cycle is 0.1 nm. Repeat the above cycle process 31 times to coat the TiO2 layer on the surface of the powder.

[0050] After the deposition is completed, transfer the powder into a muffle furnace and anneal it at 605 °C for 2.5 hours to obtain ultrafine particles of low-dielectric ceramic materials. Example

[0051] A preparation method of ultrafine particles of low-dielectric ceramic materials for 6G includes the following steps: Step 1: Sol preparation Accurately weigh 208 g of tetraethyl orthosilicate (TEOS) using an analytical balance, and transfer it to a 2000 mL beaker. Measure 300 mL of anhydrous ethanol with a measuring cylinder and slowly add it to the beaker containing TEOS. Place the beaker on a mechanical stirrer and stir at a speed of 500 rpm for 30 minutes until a uniform silicon precursor solution is formed.

[0052] Weigh 83.2 g of calcium nitrate, 124.8 g of magnesium nitrate, 30 g of aluminum isopropoxide, 16 g of zirconium oxychloride, and 20 g of lithium nitrate respectively using an analytical balance. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate to a 1000 mL beaker in sequence, and then add 400 mL of anhydrous ethanol. Place the beaker on a magnetic stirrer and stir until all substances are completely dissolved to obtain a mixed solution.

[0053] Slowly add the above-prepared mixed solution to the silicon precursor solution while stirring. Weigh 5.8 g of citric acid using an analytical balance, add it to the mixed solution, and stir evenly. Weigh graphene quantum dots accounting for 0.05% of the mass of tetraethyl orthosilicate, and add them to the above solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at a frequency of 40 kHz for 15 minutes to obtain a uniform sol.

[0054] Step 2: Gelation and supercritical drying Transfer the prepared sol to a 5 L high-pressure reaction kettle to ensure that the reaction kettle is well sealed. Place the reaction kettle in a constant temperature water bath at 50 °C and let it stand for 24 hours to fully gel the sol.

[0055] After gelation is completed, the reactor is connected to a supercritical CO2 drying system. The temperature of the drying system is set to 40°C and the pressure is set to 10 MPa. CO2 fluid is continuously introduced for 6 hours for drying. After drying, the pressure is slowly released to obtain a white block aerogel.

[0056] Step 3: Reduction Calcination The obtained aerogel was placed in a corundum crucible, and then the crucible was placed in the center of a tube furnace. High-purity nitrogen was introduced for 30 minutes to exhaust the air in the tube furnace. Then it was switched to a mixed gas of H2 and Ar, where the volume ratio of H2 to Ar was 5:95, and the gas flow rate was controlled at 50 mL / min.

[0057] The tube furnace was heated to 750°C at a heating rate of 5°C / min and kept at this temperature for 2 hours. After the heat preservation, the tube furnace was cooled to room temperature to obtain (Ca, Mg)SiO3-ZrO2 nanopowder.

[0058] Step 4: Atomic layer deposition coating and annealing Weigh 50g (Ca, Mg) SiO3-ZrO2 nanopowder into the reaction chamber of the atomic layer deposition equipment, and set the reaction chamber temperature to 120°C. Use TiCl4 and H2O as precursors for atomic layer deposition. The specific deposition cycle is as follows: the TiCl4 pulse time is set to 0.1 seconds, followed by N2 purge, and the purge time is 20 seconds; the H2O pulse time is set to 0.05 seconds, followed by N2 purge, and the purge time is 30 seconds. The thickness of the TiO2 layer in a single deposition cycle is 0.1nm. Repeat the above cycle 34 times to coat the TiO2 layer on the powder surface.

[0059] After the deposition is completed, the powder is transferred into a muffle furnace and annealed at 610°C for 3 hours to obtain ultrafine particles of low dielectric ceramic material. Example

[0060] A method for preparing ultrafine particles of low dielectric ceramic material for 6G, comprising the following steps: Step 1: Sol preparation Use a precision balance to accurately weigh 208g of tetraethyl orthosilicate (TEOS) and transfer it to a 2000mL beaker. Use a measuring cylinder to measure 300mL of anhydrous ethanol and slowly add it to the beaker containing TEOS. Place the beaker on a mechanical stirrer and stir at 500rpm for 30 minutes until a uniform silicon precursor solution is formed.

[0061] Weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride and 20g of lithium nitrate respectively using a precision balance. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride and lithium nitrate into a 1000mL beaker in sequence, and then add 400mL of anhydrous ethanol. Place the beaker on a magnetic stirrer and stir until all substances are completely dissolved to obtain a mixed solution.

[0062] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Use a precision balance to weigh 5.8g of citric acid, add it to the mixed solution, and stir evenly. Weigh 0.01% of the mass of ethyl orthosilicate graphene quantum dots and add it to the above solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at a frequency of 40kHz for 15 minutes to obtain a uniform sol.

[0063] Step 2: Gelation and supercritical drying The prepared sol was transferred to a 5L high-pressure reactor, and the reactor was well sealed. The reactor was placed in a constant temperature water bath at 40°C for 18 hours to allow the sol to fully gel.

[0064] After gelation is completed, the reactor is connected to a supercritical CO2 drying system. The temperature of the drying system is set to 40°C and the pressure is set to 10 MPa. CO2 fluid is continuously introduced for 6 hours for drying. After drying, the pressure is slowly released to obtain a white block aerogel.

[0065] Step 3: Reduction Calcination The obtained aerogel was placed in a corundum crucible, and then the crucible was placed in the center of a tube furnace. High-purity nitrogen was introduced for 30 minutes to exhaust the air in the tube furnace. Then it was switched to a mixed gas of H2 and Ar, where the volume ratio of H2 to Ar was 5:95, and the gas flow rate was controlled at 50 mL / min.

[0066] The tube furnace was heated to 700°C at a heating rate of 5°C / min and kept at this temperature for 1 hour. After the heat preservation, the tube furnace was cooled to room temperature to obtain (Ca, Mg)SiO3-ZrO2 nanopowder.

[0067] Step 4: Atomic layer deposition coating and annealing Weigh 50 g of (Ca,Mg)SiO3-ZrO2 nano powder and load it into the reaction chamber of the atomic layer deposition equipment. Set the reaction chamber temperature to 120 °C. Use TiCl4 and H2O as precursors for atomic layer deposition. The specific deposition cycle process is as follows: Set the TiCl4 pulse time to 0.1 second, and then perform N2 purge for 20 seconds; set the H2O pulse time to 0.05 second, and then perform N2 purge for 30 seconds. The thickness of the TiO2 layer for a single deposition cycle is 0.1 nm. Repeat the above cycle process 28 times to coat the TiO2 layer on the powder surface.

[0068] After the deposition is completed, transfer the powder into a muffle furnace and anneal it at 600 °C for 2 hours to obtain ultrafine particles of low dielectric ceramic materials.

[0069] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that magnesium nitrate is missing in the sol preparation process, and the remaining operation steps are the same.

[0070] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that zirconium oxychloride is missing in the sol preparation process, and the remaining operation steps are the same.

[0071] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that graphene quantum dots are missing in the sol preparation process, and the remaining operation steps are the same.

[0072] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that supercritical drying in Step 2 is replaced by ordinary drying, and the remaining operation steps are the same.

[0073] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that Step 4 is omitted, that is, the (Ca,Mg)SiO3-ZrO2 nano powder is not treated with titanium dioxide coating.

[0074] Comparative Example 6 The difference between Comparative Example 6 and Example 4 is that the number of atomic layer depositions is 35 times, and the remaining operation steps are the same.

[0075] Comparative Example 7 The difference between Comparative Example 7 and Example 4 is that the number of atomic layer depositions is 36 times, and the remaining operation steps are the same.

[0076] Performance test: 1. Dielectric constant and dielectric loss test The prepared ultrafine particles of low-dielectric ceramic material were mixed with 2wt% polyvinyl alcohol binder, and after sufficient stirring, a disc sample with a diameter of 10mm and a thickness of 2mm was made by dry pressing at a pressure of 200MPa. Subsequently, the disc sample was placed in a high-temperature furnace and sintered at 830°C for 1 hour to improve the density and mechanical strength of the sample. Silver paste was used to evenly coat both sides of the disc sample to form a silver electrode with a thickness of about 20μm. After coating, the sample was placed in an oven and dried at 150°C for 30 minutes to ensure that the silver paste was firmly attached to the surface of the sample to ensure stable signal transmission during the test. A high-precision broadband dielectric spectrometer was used for testing. The prepared disc sample was placed in a test fixture, and the capacitance (C) and loss factor (D) of the sample were measured point by point at intervals of 1GHz in the typical 6G frequency band range of 1-100GHz. According to the formula ε r =Ct / ε0 to calculate the dielectric constant, where C is the measured capacitance, t is the sample thickness, ε0 is the vacuum dielectric constant, and A is the electrode area; dielectric loss tanδ=D. The test results are shown in Table 1.

[0077] Table 1. Sample Dielectric constant εᵣ Dielectric loss tanδ Example 1 5.3 <![CDATA[8.2×10 -5 > Example 2 5.4 <![CDATA[9.1×10 -5 > Example 3 5.35 <![CDATA[8.6×10 -5 > Example 4 5.2 <![CDATA[7.8×10 -5 > Example 5 5.45 <![CDATA[9.3×10 -5 > Comparative Example 1 6.9 <![CDATA[1.8×10 -4 <!-- 8 -->]]> Comparative Example 2 6.2 <![CDATA[1.4×10 -4 > Comparative Example 3 6 <![CDATA[1.3×10 -4 > Comparative Example 4 6.5 <![CDATA[1.6×10 -4 > Comparative Example 5 6.3 <![CDATA[1.5×10 -4 > Comparative Example 6 5.1 <![CDATA[2.2×10 -4 > Comparative Example 7 5.0 <![CDATA[3.0×10 -4 > 5g of ceramic ultrafine particle sample was dispersed in 100mL of ethanol solution and ultrasonically treated for 15 minutes to make it uniformly dispersed and avoid particle agglomeration. An appropriate amount of dispersion was taken with a dropper and dropped on a copper mesh. After natural drying, it was used for high-resolution transmission electron microscopy. At least 200 particles were randomly selected from the TEM image, and their particle sizes were measured using image analysis software, and the average particle size was calculated. The statistical results are shown in Table 2. Table 2. Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 3 Comparative Example 4 Average particle size (nm) 86 92 89 82 93 150 130 3. Ceramic density test Use a high-precision electronic balance to measure the mass m1 of the ceramic disc sample in the air, accurate to 0.0001g. Suspend the sample on the electronic balance with a thin wire, immerse it completely in deionized water, and measure its mass m2 in water. Density calculation: Calculate the density of the sample according to the formula ρ=m1ρ0 / (m1-m2), where ρ0 is the density of water. Compare the calculated density with the theoretical density, calculate the relative density, and thus evaluate the compactness of the disc sample. The calculation results are shown in Table 3. Table 3. Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 5 Comparative Example 6 Comparative Example 7 Relative density (%) 98.5 98.2 98.3 98.6 98.1 90.2 98.6 98.7 Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method for ultrafine particles of a low-dielectric ceramic material for 6G, characterized in that, It includes the following steps: S1. Mix tetraethyl orthosilicate with absolute ethanol and stir evenly to obtain a uniform silicon precursor solution; dissolve calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride and lithium nitrate in absolute ethanol, stir until completely dissolved to obtain a mixed solution, mix the silicon precursor solution with the mixed solution, then add citric acid and graphene quantum dots, and disperse evenly by ultrasonic oscillation to obtain a sol; S2. Transfer the sol to a high-pressure reaction kettle, heat and let it stand for gelation, and then use supercritical CO2 drying to obtain an aerogel; S3. Place the aerogel in a tube furnace, introduce a mixed gas of H2 and Ar, heat for reduction calcination, and then cool to obtain (Ca,Mg)SiO3-ZrO2 nanometer powder; S4. Coat a TiO2 layer on the surface of the (Ca,Mg)SiO3-ZrO2 nanometer powder by atomic layer deposition technology, and then heat and anneal to crystallize the TiO2 layer to obtain ultrafine particles of dielectric ceramic materials.

2. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 1, characterized in that, In the step S1, the mass ratio of tetraethyl orthosilicate, calcium nitrate and magnesium nitrate is 1:0.4:0.

6.

3. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 1, characterized in that, In the step S1, the addition amount of graphene quantum dots is 0.01-0.05% of the mass of tetraethyl orthosilicate.

4. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 1, characterized in that, In the step S2, the heating temperature is 40-50°C and the standing time is 18-24 h.

5. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 1, characterized in that, In the step S3, the volume ratio of H2 and Ar is 5:

95.

6. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 1, characterized in that, In the step S3, the calcination temperature is 700-750°C and the time is 1-2 h.

7. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 1, wherein In the step S4, the precursors used in the atomic layer deposition process are TiCl4 and H2O.

8. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 7, characterized in that, In the atomic layer deposition process, the thickness of the TiO2 layer deposited in a single deposition cycle is 0.1 nm; The process of the single deposition cycle is as follows: (1) The pulse time of TiCl4 is 0.1 s and the N2 purge time is 20 s; (2) The pulse time of H2O is 0.05 s and the N2 purge time is 30 s.

9. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 8, characterized in that, The number of deposition cycles is 28-34 times.

10. The preparation method of ultrafine particles of a low-dielectric ceramic material for 6G according to claim 1, characterized in that, In the step S4, the annealing temperature is 600-610°C and the annealing time is 2-3 h.