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

Abstract

The present invention discloses a method for preparing ultrafine particles of low-dielectric ceramic materials for 6G, relates to the technical field of dielectric ceramic materials, and belongs to patent classification number C04B35 / 00. The specific preparation method is to first prepare a sol using tetraethyl orthosilicate, calcium nitrate, magnesium nitrate, aluminum isopropylate, zirconium oxychloride and lithium nitrate, heat the sol and let it stand for gelation, then use supercritical CO2 to dry, obtain aerogel, heat and reduce calcination to obtain (Ca, Mg) SiO3-ZrO2 nanopowder, and use atomic layer deposition technology to coat a TiO2 layer on the surface of the nanopowder to obtain ultrafine particles of dielectric ceramic materials. The ceramic particles prepared by the present invention not only have a low dielectric constant, but also have a smaller particle size and a higher density under low-temperature sintering.

Description

Technical Field

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

[0002] As communications technology advances toward the 6G era, increasingly stringent requirements are being placed on the performance of low-dielectric ceramic materials. Existing technologies have numerous shortcomings in some 6G-compatible low-dielectric ceramic materials. For example, some low-dielectric ceramic materials primarily composed of calcium silicate experience significant signal loss and attenuation when operating in 6G high-frequency environments. This significantly impacts signal transmission quality and efficiency, making it difficult to meet the high-speed, stable communication requirements of 6G.

[0003] From a material microstructure perspective, the large particle size of current ceramic powders limits the fabrication of ultra-thin dielectric layers. When dielectric layers with a thickness of 5µm or less are required, existing ceramic materials are too large to achieve such fine processing. This, in turn, limits the miniaturization and lightweighting of related electronic devices, making them unable to meet the demands of 6G communication equipment for miniaturization and high performance.

[0004] In addition, during the low-temperature sintering process, ceramic materials are prone to porosity, resulting in a less dense internal structure, which in turn affects the overall performance of the material. While increasing the sintering temperature can improve the density of the ceramic, it prevents the use of relatively inexpensive metallic silver as an electrode material. Because silver has a relatively low melting point, high-temperature sintering can cause the silver electrode to melt or undergo other physical and chemical changes, making it unable to perform its proper electrode function. This not only increases the cost of the material, but also hinders the preparation and application of subsequent devices.

[0005] In summary, existing low-dielectric ceramic materials for 6G have obvious defects in high-frequency loss, particle size, and sintering characteristics. It is urgent 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 present invention aims to provide a method for preparing ultrafine particles of low-dielectric ceramic material for 6G applications, thereby resolving the technical problems raised by the aforementioned 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 when sintered at low temperatures.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing ultrafine particles of low-dielectric ceramic material for 6G, comprising the following steps:

[0009] S1. Mixing tetraethyl orthosilicate with anhydrous ethanol and stirring uniformly to obtain a uniform silicon precursor solution; dissolving calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate in anhydrous ethanol and stirring until completely dissolved to obtain a mixed solution; mixing the silicon precursor solution with the mixed solution; then adding citric acid and graphene quantum dots; and uniformly dispersing them by ultrasonic oscillation to obtain a sol;

[0010] S2, transferring the sol to a high-pressure reactor, heating and standing to gel, and then drying with supercritical CO2 to obtain an aerogel;

[0011] S3, placing the aerogel in a tubular furnace, introducing a mixed gas of H2 and Ar, heating for reduction calcination, and then cooling to obtain (Ca, Mg)SiO3-ZrO2 nanopowder;

[0012] S4. A TiO2 layer is coated on the surface of the (Ca, Mg)SiO3-ZrO2 nanopowder using an atomic layer deposition technique, and then the TiO2 layer is crystallized by heating and annealing to obtain ultrafine particles of dielectric ceramic material.

[0013] In the technical solution of the present invention, a (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, forming 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 is due to the substitution effect of magnesium ions in the lattice, which can reduce the energy loss caused by lattice vibration, similar to installing a shock absorber 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. The introduction of ZrO2 in 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 solid protective shell to the material, allowing it to maintain good performance under high temperatures and harsh environments.

[0014] Citric acid plays an important role in the preparation of sol. As a complexing agent, citric acid can react with metal ions (such as Ca 2+ Mg 2+On the one hand, it can adjust the pH value of the solution to an appropriate range, ensuring the stability of the sol system, preventing the precipitation or aggregation of metal ions in the solution, and evenly dispersing the various components in the solution, laying the foundation for the subsequent formation of a uniform gel structure. On the other hand, citric acid helps promote the hydrolysis and polycondensation of metal ions, allowing the sol to be converted into a gel more smoothly, thus ensuring the preparation of powders with uniform particle size and stable performance.

[0015] By adding graphene quantum dots and employing a supercritical drying process, the powder particles are refined to ≤100nm. The graphene quantum dots act as an anti-caking agent, effectively preventing the particles from agglomerating and enlarging. Combined with supercritical drying, the gel avoids particle agglomeration caused by rapid solvent evaporation during drying, ultimately yielding a powder with a fine and uniform particle size. This improvement enables the production of an ultrathin dielectric layer (≤5μm), significantly reducing the device size and meeting the stringent miniaturization requirements of 6G communications.

[0016] By combining reducing atmosphere calcination with nano-TiO2 coating, this invention achieves low-temperature sintering below 850°C and ceramic density of ≥98%. Reducing atmosphere calcination utilizes a mixture of hydrogen and argon, eliminating the adverse effects of air on the sintering process while simultaneously activating the powder's sintering activity. The nano-TiO2 coating (coated via atomic layer deposition) forms a liquid phase during sintering, helping the particles "bond" more tightly and making the ceramic material denser. This not only ensures the material's density but also improves the stability of its mechanical and dielectric properties.

[0017] Preferably, in step S1, the mass ratio of tetraethyl orthosilicate, calcium nitrate and magnesium nitrate is 1:0.4:0.6.

[0018] Preferably, in step S1, the amount of graphene quantum dots added is 0.01-0.05% of the mass of ethyl orthosilicate.

[0019] Preferably, in step S2, the heating temperature is 40-50° C. and the standing time is 18-24 hours.

[0020] Preferably, in step S3, the volume ratio of H2 to Ar is 5:95.

[0021] Preferably, in step S3, the calcination temperature is 700-750° C. and the calcination time is 1-2 h.

[0022] Preferably, in step S4, the precursors used in the atomic layer deposition process are TiCl4 and H2O.

[0023] Preferably, during the atomic layer deposition process, the thickness of the TiO2 layer in a single deposition cycle is 0.1 nm;

[0024] The single deposition cycle process is:

[0025] (1) TiCl4 pulse time 0.1 seconds, N2 purge time 20 seconds;

[0026] (2) H2O pulse time 0.05 seconds, N2 purge time 30 seconds.

[0027] Preferably, the number of deposition cycles is 28-34 times.

[0028] In the technical solution of the present invention, the selection of the number of deposition cycles is crucial to achieving ideal density and dielectric properties. In order to achieve high density of the material, the present invention team determined that at least 28 deposition cycles are required. However, during the experiment, the research and development team unexpectedly discovered that when the number of depositions 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, it was found that the reason for this problem was that the overly thick coating layer led to more interface defects, including pores, cracks and irregular surface morphology. The presence of these defects will capture charges, thereby increasing energy loss and leading to an increase in dielectric loss. Therefore, the present invention strictly controls the number of deposition cycles between 28-34 times, so that the material has both ideal density and dielectric properties.

[0029] Preferably, in step S4, the annealing temperature is 600-610° C., and the annealing time is 2-3 hours.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] Using a (Ca,Mg)SiO3-ZrO2 composite material as the matrix, magnesium partially replaces calcium to form a solid solution, effectively reducing the dielectric constant and dielectric loss of the material. The introduction of ZrO2 further optimizes the material properties, enhances mechanical strength and thermal stability, and ensures that the material can maintain good performance even in complex environments.

[0032] Citric acid plays an important role as a complexing agent in sol preparation, regulating the solution pH and promoting the hydrolysis and polycondensation of metal ions, ensuring the stability of the sol system. The addition of graphene quantum dots and the supercritical drying process work synergistically to achieve powder particle refinement, thereby enabling the preparation of ultra-thin dielectric layers to meet the miniaturization requirements of 6G communications.

[0033] By combining reducing atmosphere calcination with nano-TiO2 coating, low-temperature sintering is achieved to improve the density of the ceramic material. At the same time, the number of deposition cycles is strictly controlled to avoid interface defects caused by excessively thick coating layers, which leads to increased dielectric loss, so that the material has both ideal density and dielectric properties. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention. Example

[0035] A method for preparing ultrafine particles of low-dielectric ceramic material for 6G, comprising the following steps:

[0036] Step 1: Sol preparation

[0037] Accurately weigh 208g of tetraethyl orthosilicate (TEOS) using a precision balance and transfer it to a 2000mL beaker. Using a graduated cylinder, measure 300mL of anhydrous ethanol and slowly add it to the TEOS beaker. Place the beaker on a mechanical stirrer at 500 rpm for 30 minutes until a homogeneous silicon precursor solution is formed.

[0038] Using a precision balance, weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride, and 20g of lithium nitrate. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate, in sequence, to a 1000mL beaker. 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.

[0039] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Using a precision balance, weigh 5.8g of citric acid and add it to the mixed solution, stirring evenly. Weigh 0.04% by weight of ethyl orthosilicate (TES) graphene quantum dots and add them to the solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at 40kHz for 15 minutes to obtain a uniform sol.

[0040] Step 2: Gelation and supercritical drying

[0041] The prepared sol was transferred to a 5 L autoclave, ensuring that the autoclave was well sealed. The autoclave was placed in a constant temperature water bath at 45°C for 23 hours to allow the sol to fully gel.

[0042] After gelation, the reactor was connected to a supercritical CO2 drying system. The drying system was set to 40°C and 10 MPa, and CO2 was continuously introduced for 6 hours to dry the aerogel. After drying, the pressure was slowly released to produce a white, blocky aerogel.

[0043] Step 3: Reduction Calcination

[0044] The resulting aerogel was placed in a corundum crucible, which was then placed in the center of a tube furnace. High-purity nitrogen was first introduced for 30 minutes to expel the air from the furnace. The gas was then switched to a mixture of H₂ and Ar (with a volume ratio of 5:95) and a controlled flow rate of 50 mL / min.

[0045] 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 holding period, the tube furnace was cooled to room temperature to obtain (Ca,Mg)SiO3-ZrO2 nanopowder.

[0046] Step 4: Atomic layer deposition coating and annealing

[0047] 50g of (Ca,Mg)SiO3-ZrO2 nanopowder was weighed and loaded into the reaction chamber of an atomic layer deposition (ALD) apparatus, with the chamber temperature set at 120°C. ALD was performed using TiCl4 and H2O as precursors. The deposition cycle was as follows: a TiCl4 pulse duration of 0.1 seconds, followed by a N2 purge for 20 seconds; and an H2O pulse duration of 0.05 seconds, followed by a N2 purge for 30 seconds. The thickness of the TiO2 layer in a single deposition cycle was 0.1nm. This cycle was repeated 32 times to coat the powder surface with a TiO2 layer.

[0048] 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

[0049] A method for preparing ultrafine particles of low-dielectric ceramic material for 6G, comprising the following steps:

[0050] Step 1: Sol preparation

[0051] Accurately weigh 208g of tetraethyl orthosilicate (TEOS) using a precision balance and transfer it to a 2000mL beaker. Using a graduated cylinder, measure 300mL of anhydrous ethanol and slowly add it to the TEOS beaker. Place the beaker on a mechanical stirrer at 500 rpm for 30 minutes until a homogeneous silicon precursor solution is formed.

[0052] Using a precision balance, weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride, and 20g of lithium nitrate. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate, in sequence, to a 1000mL beaker. 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.

[0053] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Using a precision balance, weigh 5.8g of citric acid and add it to the mixed solution, stirring evenly. Weigh 0.02% of the mass of ethyl orthosilicate (TES) to form graphene quantum dots and add them to the solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at 40kHz for 15 minutes to obtain a uniform sol.

[0054] Step 2: Gelation and supercritical drying

[0055] The prepared sol was transferred to a 5 L autoclave, ensuring that the autoclave was well sealed. The autoclave was placed in a constant temperature water bath at 45°C for 20 hours to allow the sol to fully gel.

[0056] After gelation, the reactor was connected to a supercritical CO2 drying system. The drying system was set to 40°C and 10 MPa, and CO2 was continuously introduced for 6 hours to dry the aerogel. After drying, the pressure was slowly released to produce a white, blocky aerogel.

[0057] Step 3: Reduction Calcination

[0058] The resulting aerogel was placed in a corundum crucible, which was then placed in the center of a tube furnace. High-purity nitrogen was first introduced for 30 minutes to expel the air from the furnace. The gas was then switched to a mixture of H₂ and Ar (with a volume ratio of 5:95) and a controlled flow rate of 50 mL / min.

[0059] 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 holding period, the tube furnace was cooled to room temperature to obtain (Ca,Mg)SiO3-ZrO2 nanopowder.

[0060] Step 4: Atomic layer deposition coating and annealing

[0061] 50g of (Ca,Mg)SiO3-ZrO2 nanopowder was weighed and loaded into the reaction chamber of an atomic layer deposition (ALD) apparatus, with the reaction chamber temperature set at 120°C. ALD was performed using TiCl4 and H2O as precursors. The deposition cycle was as follows: a TiCl4 pulse duration of 0.1 seconds, followed by a N2 purge for 20 seconds; and an H2O pulse duration of 0.05 seconds, followed by a N2 purge for 30 seconds. The thickness of the TiO2 layer in a single deposition cycle was 0.1nm. This cycle was repeated 29 times to coat the powder surface with a TiO2 layer.

[0062] 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

[0063] A method for preparing ultrafine particles of low-dielectric ceramic material for 6G, comprising the following steps:

[0064] Step 1: Sol preparation

[0065] Accurately weigh 208g of tetraethyl orthosilicate (TEOS) using a precision balance and transfer it to a 2000mL beaker. Using a graduated cylinder, measure 300mL of anhydrous ethanol and slowly add it to the TEOS beaker. Place the beaker on a mechanical stirrer at 500 rpm for 30 minutes until a homogeneous silicon precursor solution is formed.

[0066] Using a precision balance, weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride, and 20g of lithium nitrate. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate, in sequence, to a 1000mL beaker. 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.

[0067] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Using a precision balance, weigh 5.8g of citric acid and add it to the mixed solution, stirring evenly. Weigh 0.03% of the mass of ethyl orthosilicate (TES) to form graphene quantum dots and add them to the solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at 40kHz for 15 minutes to obtain a uniform sol.

[0068] Step 2: Gelation and supercritical drying

[0069] The prepared sol was transferred to a 5 L autoclave, ensuring that the autoclave was well sealed. The autoclave was placed in a constant temperature water bath at 45°C for 22 hours to allow the sol to fully gel.

[0070] After gelation, the reactor was connected to a supercritical CO2 drying system. The drying system was set to 40°C and 10 MPa, and CO2 was continuously introduced for 6 hours to dry the aerogel. After drying, the pressure was slowly released to produce a white, blocky aerogel.

[0071] Step 3: Reduction Calcination

[0072] The resulting aerogel was placed in a corundum crucible, which was then placed in the center of a tube furnace. High-purity nitrogen was first introduced for 30 minutes to expel the air from the furnace. The gas was then switched to a mixture of H₂ and Ar (with a volume ratio of 5:95) and a controlled flow rate of 50 mL / min.

[0073] 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 holding period, the tube furnace was cooled to room temperature to obtain (Ca,Mg)SiO3-ZrO2 nanopowder.

[0074] Step 4: Atomic layer deposition coating and annealing

[0075] 50g of (Ca,Mg)SiO3-ZrO2 nanopowder was weighed and loaded into the reaction chamber of an atomic layer deposition (ALD) apparatus, with the reaction chamber temperature set at 120°C. ALD was performed using TiCl4 and H2O as precursors. The deposition cycle was as follows: a TiCl4 pulse duration of 0.1 seconds, followed by a N2 purge for 20 seconds; and an H2O pulse duration of 0.05 seconds, followed by a N2 purge for 30 seconds. The thickness of the TiO2 layer in a single deposition cycle was 0.1nm. This cycle was repeated 31 times to coat the powder surface with a TiO2 layer.

[0076] 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

[0077] A method for preparing ultrafine particles of low-dielectric ceramic material for 6G, comprising the following steps:

[0078] Step 1: Sol preparation

[0079] Accurately weigh 208g of tetraethyl orthosilicate (TEOS) using a precision balance and transfer it to a 2000mL beaker. Using a graduated cylinder, measure 300mL of anhydrous ethanol and slowly add it to the TEOS beaker. Place the beaker on a mechanical stirrer at 500 rpm for 30 minutes until a homogeneous silicon precursor solution is formed.

[0080] Using a precision balance, weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride, and 20g of lithium nitrate. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate, in sequence, to a 1000mL beaker. 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.

[0081] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Use a precision balance to weigh 5.8g of citric acid and add it to the mixed solution, stirring evenly. Weigh 0.05% of the mass of ethyl orthosilicate (TES) to form graphene quantum dots and add them to the solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at 40kHz for 15 minutes to obtain a uniform sol.

[0082] Step 2: Gelation and supercritical drying

[0083] The prepared sol was transferred to a 5 L autoclave, ensuring that the autoclave was well sealed. The autoclave was placed in a constant temperature water bath at 50°C for 24 hours to allow the sol to fully gel.

[0084] After gelation, the reactor was connected to a supercritical CO2 drying system. The drying system was set to 40°C and 10 MPa, and CO2 was continuously introduced for 6 hours to dry the aerogel. After drying, the pressure was slowly released to produce a white, blocky aerogel.

[0085] Step 3: Reduction Calcination

[0086] The resulting aerogel was placed in a corundum crucible, which was then placed in the center of a tube furnace. High-purity nitrogen was first introduced for 30 minutes to expel the air from the furnace. The gas was then switched to a mixture of H₂ and Ar (with a volume ratio of 5:95) and a controlled flow rate of 50 mL / min.

[0087] 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 holding period, the tube furnace was cooled to room temperature to obtain (Ca,Mg)SiO3-ZrO2 nanopowder.

[0088] Step 4: Atomic layer deposition coating and annealing

[0089] 50g of (Ca,Mg)SiO3-ZrO2 nanopowder was weighed and loaded into the reaction chamber of an atomic layer deposition (ALD) apparatus, with the chamber temperature set at 120°C. ALD was performed using TiCl4 and H2O as precursors. The deposition cycle was as follows: a TiCl4 pulse duration of 0.1 seconds, followed by a N2 purge for 20 seconds; and an H2O pulse duration of 0.05 seconds, followed by a N2 purge for 30 seconds. The thickness of the TiO2 layer in a single deposition cycle was 0.1nm. This cycle was repeated 34 times to coat the powder surface with a TiO2 layer.

[0090] 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

[0091] A method for preparing ultrafine particles of low-dielectric ceramic material for 6G, comprising the following steps:

[0092] Step 1: Sol preparation

[0093] Accurately weigh 208g of tetraethyl orthosilicate (TEOS) using a precision balance and transfer it to a 2000mL beaker. Using a graduated cylinder, measure 300mL of anhydrous ethanol and slowly add it to the TEOS beaker. Place the beaker on a mechanical stirrer at 500 rpm for 30 minutes until a homogeneous silicon precursor solution is formed.

[0094] Using a precision balance, weigh 83.2g of calcium nitrate, 124.8g of magnesium nitrate, 30g of aluminum isopropoxide, 16g of zirconium oxychloride, and 20g of lithium nitrate. Add the weighed calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate, in sequence, to a 1000mL beaker. 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.

[0095] Slowly add the prepared mixed solution to the silicon precursor solution while stirring. Using a precision balance, weigh 5.8g of citric acid and add it to the mixed solution, stirring evenly. Weigh 0.01% of the mass of ethyl orthosilicate (TES) to form graphene quantum dots and add them to the solution. Transfer the mixed solution to an ultrasonic cleaner and ultrasonically disperse it at 40kHz for 15 minutes to obtain a uniform sol.

[0096] Step 2: Gelation and supercritical drying

[0097] The prepared sol was transferred to a 5 L autoclave, ensuring that the autoclave was well sealed. The autoclave was placed in a constant temperature water bath at 40°C for 18 hours to allow the sol to fully gel.

[0098] After gelation, the reactor was connected to a supercritical CO2 drying system. The drying system was set to 40°C and 10 MPa, and CO2 was continuously introduced for 6 hours to dry the aerogel. After drying, the pressure was slowly released to produce a white, blocky aerogel.

[0099] Step 3: Reduction Calcination

[0100] The resulting aerogel was placed in a corundum crucible, which was then placed in the center of a tube furnace. High-purity nitrogen was first introduced for 30 minutes to expel the air from the furnace. The gas was then switched to a mixture of H₂ and Ar (with a volume ratio of 5:95) and a controlled flow rate of 50 mL / min.

[0101] 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 holding period, the tube furnace was cooled to room temperature to obtain (Ca,Mg)SiO3-ZrO2 nanopowder.

[0102] Step 4: Atomic layer deposition coating and annealing

[0103] 50g of (Ca,Mg)SiO3-ZrO2 nanopowder was weighed and loaded into the reaction chamber of an atomic layer deposition (ALD) apparatus, with the chamber temperature set at 120°C. ALD was performed using TiCl4 and H2O as precursors. The deposition cycle was as follows: a TiCl4 pulse duration of 0.1 seconds, followed by a N2 purge for 20 seconds; and an H2O pulse duration of 0.05 seconds, followed by a N2 purge for 30 seconds. The thickness of the TiO2 layer in a single deposition cycle was 0.1nm. This cycle was repeated 28 times to coat the powder surface with a TiO2 layer.

[0104] After the deposition is completed, the powder is transferred into a muffle furnace and annealed at 600°C for 2 hours to obtain ultrafine particles of low-dielectric ceramic material.

[0105] Comparative Example 1

[0106] The difference between Comparative Example 1 and Example 1 is that magnesium nitrate is missing during the preparation of the sol, and the remaining operating steps are the same.

[0107] Comparative Example 2

[0108] The difference between Comparative Example 2 and Example 1 is that zirconium oxychloride is omitted in the sol preparation process, and the remaining operating steps are the same.

[0109] Comparative Example 3

[0110] The difference between Comparative Example 3 and Example 1 is that graphene quantum dots are missing in the sol preparation process, and the other operating steps are the same.

[0111] Comparative Example 4

[0112] The difference between Comparative Example 4 and Example 1 is that the supercritical drying in step 2 is replaced by ordinary drying, and the remaining operating steps are the same.

[0113] Comparative Example 5

[0114] The difference between Comparative Example 5 and Example 1 is that step 4 is omitted, that is, the (Ca, Mg)SiO3-ZrO2 nanopowder is not subjected to titanium dioxide coating treatment.

[0115] Comparative Example 6

[0116] The difference between Comparative Example 6 and Example 4 is that the number of atomic layer depositions is 35 times, and the other operating steps are the same.

[0117] Comparative Example 7

[0118] The difference between Comparative Example 7 and Example 4 is that the number of atomic layer depositions is 36 times, and the other operating steps are the same.

[0119] Performance testing:

[0120] 1. Dielectric constant and dielectric loss test

[0121] The prepared ultrafine particles of low-dielectric ceramic material are mixed with 2wt% of polyvinyl alcohol binder, and after thorough stirring, a disc sample with a diameter of 10mm and a thickness of 2mm is made by dry pressing at a pressure of 200MPa. Subsequently, the disc sample is 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 is 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 is placed in an oven and dried at 150°C for 30 minutes to ensure that the silver paste is firmly attached to the surface of the sample and to ensure stable signal transmission during the test. A high-precision broadband dielectric spectrometer is used for testing. The prepared disc sample is placed in a test fixture, and the capacitance (C) and loss factor (D) of the sample are measured point by point at intervals of 1GHz in the typical 6G frequency band of 1-100GHz. According to the formula ε r =Ct / ε0, 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.

[0122] Table 1.

[0123] 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 ]]>

[0124] 5g of ultrafine ceramic particles were dispersed in 100mL of ethanol and sonicated for 15 minutes to achieve uniform dispersion and prevent particle agglomeration. An appropriate amount of the dispersion was pipetted onto a copper grid and allowed to dry naturally. High-resolution transmission electron microscopy was then used to examine at least 200 randomly selected particles from the TEM image. Image analysis software was used to measure the particle size and calculate the average particle size. The statistical results are shown in Table 2.

[0125] Table 2.

[0126] 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

[0127] 3. Ceramic density test

[0128] Using a high-precision electronic balance, measure the mass m1 of the ceramic disc sample in air to an accuracy of 0.0001g. Suspend the sample from the electronic balance with a thin wire and completely immerse it in deionized water. Measure its mass m2 in water. Density calculation: Calculate the sample's density using the formula ρ = m1ρ0 / (m1 - m2), where ρ0 is the density of water. Compare the calculated density with the theoretical density to calculate the relative density, thereby assessing the compaction performance of the disc sample. The results are shown in Table 3.

[0129] Table 3.

[0130] 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

[0131] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine particles of low dielectric ceramic material for 6G, characterized in that: The following steps are involved: S1. Mixing tetraethyl orthosilicate with anhydrous ethanol and stirring uniformly to obtain a uniform silicon precursor solution; dissolving calcium nitrate, magnesium nitrate, aluminum isopropoxide, zirconium oxychloride, and lithium nitrate in anhydrous ethanol and stirring until completely dissolved to obtain a mixed solution; mixing the silicon precursor solution with the mixed solution; then adding citric acid and graphene quantum dots; and uniformly dispersing them by ultrasonic oscillation to obtain a sol; S2, transferring the sol to a high-pressure reactor, heating and standing to gel, and then drying with supercritical CO2 to obtain an aerogel; S3, placing the aerogel in a tubular furnace, introducing a mixed gas of H2 and Ar, heating for reduction calcination, and then cooling to obtain (Ca, Mg)SiO3-ZrO2 nanopowder; S4, coating a TiO2 layer on the surface of the (Ca, Mg)SiO3-ZrO2 nanopowder using an atomic layer deposition technique, and then crystallizing the TiO2 layer by heating and annealing to obtain ultrafine particles of dielectric ceramic material; The precursors used in the atomic layer deposition process are TiCl4 and H2O; The number of deposition cycles was 28–34; The thickness of the TiO2 layer in a single deposition cycle is 0.1 nm; The single deposition cycle process is: (1) TiCl4 pulse time 0.1 seconds, N2 purge time 20 seconds; (2) H2O pulse time 0.05 seconds, N2 purge time 30 seconds.

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

6.

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

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

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

95.

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

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