Low dielectric ceramic and preparation method thereof

Abstract

The invention belongs to the technical field of ceramic materials, and particularly relates to low-dielectric ceramic and a preparation method thereof, and the preparation method comprises the following steps: firstly, mixing Li2CO3, Al2O3 and SiO2 according to a molar ratio of 1: 1: 2, and carrying out ball milling, drying, screening and presintering to obtain LiAlSiO4, namely powder 1; mixing Al2O3, MoO3 and B2O3 according to a molar ratio of 1: 3: (0.2-0.3), and carrying out ball milling, drying, screening and pre-sintering to obtain powder 2; mixing the powder 1 in the step S1 and the powder 2 in the step S2 according to a mass ratio of 1: (12-16), adding lithium nitrate powder in a molar ratio of 0.01-0.05 to the powder 1, adding a solvent, and grinding to obtain slurry; and finally, pouring the slurry obtained in the step S3 into a mold with the diameter of 10mm, putting the mold into a heating ring, fixing the heating ring on a single-shaft press, pressing, carrying out cold sintering, cooling and demolding to obtain a sample, and annealing to obtain the low-dielectric ceramic.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and particularly relates to a low-dielectric ceramic and a preparation method thereof. Background Art

[0002] 6G (the sixth generation of mobile communication technology) aims to achieve ultra-low latency in signal transmission and truly enable the interconnection of all things. Low-dielectric constant ε r ceramics can reduce the interactive coupling loss between the substrate and the metal electrode, and significantly improve the signal transmission rate. The lower the dielectric constant, the shorter the latency. At the same time, the dielectric porcelain also needs to have a high quality factor Q×f and a near-zero resonance frequency temperature coefficient τ f , to ensure low loss and working stability of the device. At present, the εr of low-dielectric ceramics is basically greater than 6, such as Mg 2 SiO 4 olivine, CaMgSi 2 O 6 diopside, AB 2 Si 2 O 8 (A = Ba, Sr, Ca; B = Al, Ga) feldspar, MgAl 2 O 4 spinel, MgWO 4 tungstate and Mg 2 TiO 4 . ε r <5 application scenarios mostly use organic polymer materials (polystyrene, fluorinated polymers, liquid crystal polymers, etc.) or glass, which have problems such as poor mechanical properties and large losses.

[0003] β-spodumene LiAlSiO 4 (β-LAS) has a small ε r = 4-5, but its inherent mechanical properties are poor, the elastic modulus is low, and it is easy to form a glass phase, and it is difficult to obtain a dense pure-phase porcelain body. Due to the anisotropy of the negative thermal expansion coefficient, more residual stress is released during cooling, which easily causes the porcelain body to crack and the fracture strength to decrease. Adding SiC, Si 3 N 4 , Al 2 O 3 , forsterite, mullite can obtain a composite ceramic with high mechanical strength, but the added phase ε rThey are all relatively high. Therefore, it is difficult for composite ceramics to simultaneously have an ultra-low dielectric constant and a near-zero temperature coefficient. Research shows that reducing the temperature below 1300 °C can effectively avoid microcracks. However, inorganic ceramics are mainly composed of covalent bonds and ionic bonds, and their dense sintering requires a relatively high sintering driving force. However, high temperatures will cause cracks and lithium volatilization, affecting the dielectric properties. The present invention provides a method for obtaining dense β-LAS ceramics at low temperatures, which can effectively prevent lithium volatilization, solve the problem of porcelain body cracking, and have a low dielectric constant and a near-zero resonance frequency temperature coefficient. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for preparing low-dielectric ceramics, comprising the following steps:

[0005] S1: Mix Li 2 CO 3 , Al 2 O 3 and SiO 2 , perform ball milling, drying, screening, and pre-sintering to obtain LiAlSiO 4 , i.e., powder 1;

[0006] S2: Mix Al 2 O 3 , MoO 3 and B 2 O 3 , perform ball milling, drying, screening, and pre-sintering to obtain powder 2;

[0007] S3: Mix the powder 1 from S1 and the powder 2 from S2 in a mass ratio of 1:12 to 16, add lithium nitrate powder with a molar ratio of 0.01 to 0.05 to the powder 1, add a solvent, and perform grinding to obtain a slurry;

[0008] S4: Pour the slurry from S3 into a mold with a diameter of 10 mm, place the mold in a heating coil, fix it on a uniaxial press, perform pressing, cold sintering, cooling and demolding to obtain a sample, and perform annealing to obtain low-dielectric ceramics.

[0009] Further, the ball milling time in S1 is 6 h, the drying temperature is 100 °C, the pre-sintering temperature is 900 - 1000 °C, and a 200-mesh sieve is used during the screening process.

[0010] Further, the ball milling time in S2 is 6 h, the drying temperature is 100 °C, the pre-sintering temperature is 700 - 800 °C, and a 200-mesh sieve is used during the screening process.

[0011] Further, the solvent in S3 is water or acetic acid; the slurry is a powder with a water / acetic acid content of 8 - 12 wt.%.

[0012] Furthermore, during the pressing process in S4, a uniaxial press applies a pressure of 100 - 200 Mpa, the pressure holding time is 10 - 15 min, the speed is 8 - 10 °C / min, the temperature during the cold sintering process is raised to 190 - 250 °C, and the sintering time is 1 - 2 h; the annealing temperature is 600 - 700 °C, and the annealing time is 1 - 6 h.

[0013] A low - dielectric ceramic.

[0014] Beneficial effects

[0015] Through the preparation method of a low - dielectric ceramic provided by the present invention, a dense low - dielectric leucite ceramic can be obtained at a low temperature of 700 °C. The dielectric constant is less than 4 and the temperature coefficient is 0, which has not been achieved in the leucite system and is also rare in the entire dielectric field. Lithium nitrate is added in the method. On the one hand, it can increase the solubility of powder 1 in the solvent and promote cold sintering; on the other hand, it can make up for the loss of lithium volatilization during annealing in step 6; enabling cold sintering to be achieved at a low temperature, effectively avoiding cracking of the leucite ceramic at high temperatures. Specific embodiments

[0016] The following will clearly and completely describe the technical solutions of the present invention in conjunction with Examples 1 - 10 of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0017] Example 1

[0018] S1: Weigh Li 2 CO 3 , Al 2 O 3 and SiO 2 according to the masses of 73.9, 102 and 120 g, ball - mill for 6 h, the drying temperature is 100 °C, after passing through a 200 - mesh sieve, and then pre - sinter at 900 °C to obtain LiAlSiO 4 powder, that is, powder 1;

[0019] S2: Mix Al 2 O 3 , MoO 3 and B 2 O 3 according to the masses of 102, 431.82 and 13.92 g, ball - mill for 6 h, dry at 100 °C, pass through a 200 - mesh sieve, and then pre - sinter at 750 °C to obtain powder 2;

[0020] S3: Weigh 10 g of the powder 1 obtained in S1 and 125 g of the powder 2 obtained in S2 respectively, pour them into an agate mortar, add 0.69 g of lithium nitrate powder, and at the same time drip water or acetic acid solvent, and grind carefully to ensure uniform mixing to obtain a powder with a water or acid content of 8 wt.%.

[0021] S4: Pour the above-mentioned uniformly mixed slurry into a cylindrical mold with a diameter of 10 mm, and fit the gasket well. Place the mold in a heating coil and fix it on a uniaxial press; use the uniaxial press to apply a pressure of 100 Mpa and hold the pressure for 10 min, then heat up to 190 °C at a rate of 8 °C / min and sinter for 1 h, then cool naturally, demold, and then anneal at 600 °C for 2 h to obtain a low-dielectric ceramic.

[0022] Example 2

[0023] S1: Weigh 73.9 g, 102 g and 120 g of Li 2 CO 3 、Al 2 O 3 and SiO 2 respectively, ball mill for 6 h, the drying temperature is 100 °C, after passing through a 200-mesh sieve, and after pre-sintering at 950 °C, obtain LiAlSiO 4 powder, that is, powder 1;

[0024] S2: Mix 102 g, 431.82 g and 13.92 g of Al 2 O 3 、MoO 3 and B 2 O 3 by mass, ball mill for 6 h, dry at 100 °C, pass through a 200-mesh sieve, and obtain powder 2 after pre-sintering at 750 °C;

[0025] S3: Weigh 10 g of the powder 1 obtained in S1 and 130 g of the powder 2 obtained in S2 respectively, pour them into an agate mortar, add 0.69 g of lithium nitrate powder, and at the same time drip water or acetic acid solvent, and grind carefully to ensure uniform mixing to obtain a powder with a water or acid content of 8 wt.%.

[0026] S4: Pour the above-mentioned uniformly mixed slurry into a cylindrical mold with a diameter of 10 mm, and fit the gasket well. Place the mold in a heating coil and fix it on a uniaxial press; use the uniaxial press to apply a pressure of 100 Mpa and hold the pressure for 10 min, then heat up to 190 °C at a rate of 8 °C / min and sinter for 1 h, then cool naturally, demold, and then anneal at 600 °C for 2 h to obtain a low-dielectric ceramic.

[0027] Example 3

[0028] S1: Take Li 2 CO3 、Al 2 O 3 and SiO 2 are weighed by 73.9, 102 and 120 g in mass, ball milled for 6 h, dried at a temperature of 100 °C, sieved through a 200-mesh sieve, and pre-sintered at 950 °C to obtain LiAlSiO 4 powder, namely powder 1;

[0029] S2: Mix Al 2 O 3 , MoO 3 and B 2 O 3 by 102, 431.82 and 13.92 g in mass, ball milled for 6 h, dried at 100 °C, sieved through a 200-mesh sieve, and pre-sintered at 800 °C to obtain powder 2;

[0030] S3: Weigh 10 g and 130 g of powder 1 obtained in S1 and powder 2 obtained in S2 respectively, pour them into an agate mortar, add 1.39 g of lithium nitrate powder, and simultaneously drip water or acetic acid solvent, and grind carefully to ensure uniform mixing to obtain a powder body with a water or acid content of 9 wt.%;

[0031] S4: Pour the above-mentioned uniformly mixed slurry into a cylindrical mold with a diameter of 10 mm, fit the gasket, place the mold in a heating coil, and fix it on a uniaxial press; use the uniaxial press to apply a pressure of 150 Mpa and hold the pressure for 10 min, then heat up to 200 °C at a speed of 10 °C / min and sinter for 1 h, then cool naturally, demold, and then anneal at 700 °C for 2 h to obtain a low-dielectric ceramic.

[0032] Example 4

[0033] S1: Weigh Li 2 CO 3 , Al 2 O 3 and SiO 2 by 73.9, 102 and 120 g in mass, ball milled for 6 h, dried at a temperature of 100 °C, sieved through a 200-mesh sieve, and pre-sintered at 950 °C to obtain LiAlSiO 4 powder, namely powder 1;

[0034] S2: Mix Al 2 O 3 , MoO 3 and B 2 O 3 by 102, 431.82 and 20.89 g in mass, ball milled for 6 h, dried at 100 °C, sieved through a 200-mesh sieve, and pre-sintered at 750 °C to obtain powder 2;

[0035] S3: Weigh 10 g of the powder 1 obtained in S1 and 140 g of the powder 2 obtained in S2 respectively, pour them into an agate mortar, add 1.39 g of lithium nitrate powder, and at the same time drip water or acetic acid solvent, and grind carefully to ensure uniform mixing to obtain a powder with a water or acid content of 9 wt.%.

[0036] S4: Pour the above-mentioned uniformly mixed slurry into a cylindrical mold with a diameter of 10 mm, fit the gasket, place the mold in a heating coil, and fix it on a uniaxial press; use the uniaxial press to apply a pressure of 150 Mpa and hold the pressure for 15 min, then heat it up to 200 °C at a rate of 10 °C / min and sinter for 1 h, and then cool naturally, demold, and then anneal at 700 °C for 1.5 h to obtain a low-dielectric ceramic.

[0037] Example 5

[0038] S1: Weigh 73.9 g, 102 g and 120 g of Li 2 CO 3 , Al 2 O 3 and SiO 2 respectively, ball mill for 6 h, the drying temperature is 100 °C, after passing through a 200-mesh sieve, and after pre-sintering at 1000 °C, obtain LiAlSiO 4 powder, that is, powder 1;

[0039] S2: Mix 102 g, 431.82 g and 20.89 g of Al 2 O 3 , MoO 3 and B 2 O 3 by mass, ball mill for 6 h, dry at 100 °C, pass through a 200-mesh sieve, and obtain powder 2 after pre-sintering at 800 °C;

[0040] S3: Weigh 10 g of the powder 1 obtained in S1 and 140 g of the powder 2 obtained in S2 respectively, pour them into an agate mortar, add 1.39 g of lithium nitrate powder, and at the same time drip water or acetic acid solvent, and grind carefully to ensure uniform mixing to obtain a powder with a water or acid content of 10 wt.%.

[0041] S4: Pour the above-mentioned uniformly mixed slurry into a cylindrical mold with a diameter of 10 mm, fit the gasket, place the mold in a heating coil, and fix it on a uniaxial press; use the uniaxial press to apply a pressure of 200 Mpa and hold the pressure for 15 min, then heat it up to 220 °C at a rate of 10 °C / min and sinter for 1.5 h, and then cool naturally, demold, and then anneal at 700 °C for 1.5 h to obtain a low-dielectric ceramic.

[0042] Example 6

[0043] S1: Take Li2 CO 3 、 Al 2 O 3 and SiO 2 are weighed at 73.9, 102 and 120 g by mass, ball milled for 6 h, dried at a temperature of 100 °C, sieved through a 200-mesh sieve, and pre-fired at 1000 °C to obtain LiAlSiO 4 powder, namely powder 1;

[0044] S2: Al 2 O 3 、 MoO 3 and B 2 O 3 are mixed at 102, 431.82 and 20.89 g by mass, ball milled for 6 h, dried at 100 °C, sieved through a 200-mesh sieve, and pre-fired at 750 °C to obtain powder 2;

[0045] S3: 10 g and 150 g of powder 1 obtained in S1 and powder 2 obtained in S2 are weighed respectively, poured into an agate mortar, 1.39 g of lithium nitrate powder is added, and water or acetic acid solvent is dropped while carefully grinding to ensure uniform mixing, obtaining a powder with a water or acid content of 10 wt.%;

[0046] S4: The above-mentioned uniformly mixed slurry is poured into a cylindrical mold with a diameter of 10 mm, and a gasket is nested. The mold is placed in a heating coil and fixed on a uniaxial press; a pressure of 200 Mpa is applied using the uniaxial press and held for 15 min, then heated to 220 °C at a rate of 10 °C / min and sintered for 2 h, followed by natural cooling, demolding, and then annealed at 700 °C for 2 h to obtain a low-dielectric ceramic.

[0047] Example 7

[0048] S1: Li 2 CO 3 、 Al 2 O 3 and SiO 2 are weighed at 73.9, 102 and 120 g by mass, ball milled for 6 h, dried at a temperature of 100 °C, sieved through a 200-mesh sieve, and pre-fired at 1000 °C to obtain LiAlSiO 4 powder, namely powder 1;

[0049] S2: Al 2 O 3 、 MoO 3 and B 2 O 3 are mixed at 102, 431.82 and 20.89 g by mass, ball milled for 6 h, dried at 100 °C, sieved through a 200-mesh sieve, and pre-fired at 800 °C to obtain powder 2;

[0050] S3: Weigh 10 g of the powder 1 obtained in S1 and 150 g of the powder 2 obtained in S2 respectively, pour them into an agate mortar, add 2.07 g of lithium nitrate powder, and at the same time drip water or acetic acid solvent, and grind carefully to ensure uniform mixing to obtain a powder body with a water or acid content of 11 wt.%.

[0051] S4: Pour the above-mentioned uniformly mixed slurry into a cylindrical mold with a diameter of 10 mm, fit the gasket, place the mold in a heating coil, and fix it on a uniaxial press; use the uniaxial press to apply a pressure of 180 Mpa and hold the pressure for 10 min, then heat up to 240 °C at a rate of 10 °C / min and sinter for 2 h, then cool naturally, demold, and then anneal at 700 °C for 2 h to obtain a low-dielectric ceramic.

[0052] Example 8

[0053] S1: Weigh 73.9 g, 102 g and 120 g of Li 2 CO 3 、Al 2 O 3 and SiO 2 respectively, ball mill for 6 h, the drying temperature is 100 °C, after passing through a 200-mesh sieve, and after pre-sintering at 1000 °C, obtain LiAlSiO 4 powder, that is, powder 1;

[0054] S2: Mix 102 g, 431.82 g and 13.92 g of Al 2 O 3 、MoO 3 and B 2 O 3 by mass, ball mill for 6 h, dry at 100 °C, pass through a 200-mesh sieve, and obtain powder 2 after pre-sintering at 750 °C;

[0055] S3: Weigh 10 g of the powder 1 obtained in S1 and 160 g of the powder 2 obtained in S2 respectively, pour them into an agate mortar, add 2.76 g of lithium nitrate powder, and at the same time drip water or acetic acid solvent, and grind carefully to ensure uniform mixing to obtain a powder body with a water or acid content of 11 wt.%.

[0056] S4: Pour the above-mentioned uniformly mixed slurry into a cylindrical mold with a diameter of 10 mm, fit the gasket, place the mold in a heating coil, and fix it on a uniaxial press; use the uniaxial press to apply a pressure of 180 Mpa and hold the pressure for 10 min, then heat up to 240 °C at a rate of 10 °C / min and sinter for 2 h, then cool naturally, demold, and then anneal at 700 °C for 2 h to obtain a low-dielectric ceramic.

[0057] Example 9

[0058] S1: Weigh Li2 CO 3 、 Al 2 O 3 and SiO 2 were weighed according to 73.9, 102 and 120 g by mass, ball milled for 6 h, dried at a temperature of 100 °C, sieved through a 200-mesh sieve, and pre-fired at 950 °C to obtain LiAlSiO 4 powder, i.e., powder 1;

[0059] S2: Al 2 O 3 , MoO 3 and B 2 O 3 were mixed according to 102, 431.82 and 13.92 g by mass, ball milled for 6 h, dried at 100 °C, sieved through a 200-mesh sieve, and pre-fired at 800 °C to obtain powder 2;

[0060] S3: 10 g and 160 g of powder 1 obtained in S1 and powder 2 obtained in S2 were weighed respectively, poured into an agate mortar, 3.45 g of lithium nitrate powder was added, and water or acetic acid solvent was dropped while carefully grinding to ensure uniform mixing, obtaining a powder with a water or acid content of 12 wt.%;

[0061] S4: The above-mentioned uniformly mixed slurry was poured into a cylindrical mold with a diameter of 10 mm, and a gasket was nested. The mold was placed in a heating coil and fixed on a uniaxial press; a pressure of 140 Mpa was applied using the uniaxial press and kept for 10 min, then heated to 200 °C at a rate of 8 °C / min and sintered for 1.5 h, followed by natural cooling, demolding, and then annealed at 700 °C for 2 h to obtain a low-dielectric ceramic.

[0062] Example 10

[0063] S1: Li 2 CO 3 , Al 2 O 3 and SiO 2 were weighed according to 73.9, 102 and 120 g by mass, ball milled for 6 h, dried at a temperature of 100 °C, sieved through a 200-mesh sieve, and pre-fired at 900 °C to obtain LiAlSiO 4 powder, i.e., powder 1;

[0064] S2: Al 2 O 3 , MoO 3 and B 2 O 3 were mixed according to 102, 431.82 and 20.89 g by mass, ball milled for 6 h, dried at 100 °C, sieved through a 200-mesh sieve, and pre-fired at 750 °C to obtain powder 2;

[0065] S3: Weigh 10 and 160 g of powder 1 of S1 and powder 2 obtained from S2, respectively, pour into an agate mortar, add 3.45 g of lithium nitrate powder, and drip water or acetic acid solvent at the same time, grind carefully to ensure uniform mixing, and obtain a powder containing 12 wt.% of water or acid;

[0066] S4: Pour the above-mentioned evenly mixed slurry into a cylindrical mold with a diameter of 10 mm, and insert the gasket, put the mold into the heating ring, and fix it on the uniaxial press; use the uniaxial press to apply a pressure of 140 MPa and maintain the pressure for 15 minutes, then increase the temperature to 200°C at a speed of 8°C / min, sinter for 1.5 hours, then cool naturally, demold, and anneal at 700°C for 6 hours to obtain a low-dielectric ceramic.

[0067] The results obtained through Examples 1 to 10 are shown in Table 1. The specific data show that a ceramic material having a dielectric constant less than 4 and a temperature coefficient of 0 can meet the requirements of ultra-low delay in signal transmission and temperature stability of device operation.

[0068]

[0069]

[0070] Through the preparation method of a low-dielectric ceramic provided by the present invention, two materials are mixed together to adjust the temperature coefficient. The prior art is the traditional solid phase method, which is easy for researchers to think of. However, due to the lack of material types, materials with a dielectric constant of less than 4 and a positive temperature coefficient are very rare. The material in step 2 of the present invention just meets the performance requirements, but its sintering temperature is lower than 800°C, which is far from eucryptite (sintering temperature is higher than 1300°C), and co-firing matching is difficult to solve, which cannot be achieved by the traditional solid phase method. This prompted us to find a suitable sintering method. Cold sintering can solve this problem, so this also reflects our creative thinking and substantial progress.

[0071] In the present invention, it is creative to put the materials of eucryptite and S2 together. By cold sintering, the problem of mismatched sintering between the two is solved. At present, there are three important indicators for the application of dielectric ceramics: small dielectric constant, high quality factor, and near-zero temperature coefficient, and none of them can be missing. Existing research has no materials with a dielectric constant less than 4 and a temperature coefficient of 0 at the same time, so it is necessary to compound and adjust the temperature coefficient. The dielectric constant of existing ceramic materials is basically greater than 6, and there are few less than 4, and low-dielectric ceramics are lacking. Most of the existing materials, including eucryptite, have a negative temperature coefficient, and only a small part of the materials have a positive temperature coefficient. Materials with a dielectric constant less than 4 (meeting the dielectric constant of the composite material less than 4) and a positive temperature coefficient are extremely rare. ⑤In summary, there are few low-dielectric materials with a dielectric constant less than 4. It is very difficult to satisfy the opposite temperature coefficients of the two, and it is even more difficult to satisfy the similar sintering characteristics of the two. Therefore, it is difficult to prepare a composite material with a dielectric constant less than 4 and a temperature coefficient of 0; in the prior art, porous structures, nano-hollow spheres, and adding PTFE polymer materials will all reduce the mechanical properties of the materials, and the quality factor is very low. The pore structure is easy to absorb water, and water will affect the dielectric properties of the materials. At present, there is no ceramic material with a dielectric less than 4 and a temperature coefficient of 0. However, the method provided by the present invention obtains a low-dielectric ceramic with such properties, reflecting the substantial progress brought by this application.

Claims

1. A method for preparing low dielectric ceramics, characterized in that: The following steps are involved: S1: Li2CO3, Al2O3 and SiO2 in a molar ratio of 1:1:2 are mixed, ball-milled, dried, screened, and pre-calcined to obtain LiAlSiO4, i.e., powder 1; S2: Al2O3, MoO3 and B2O3 are mixed in a molar ratio of 1:3:0.2-0.3, and powder 2 is obtained by ball milling, drying, screening and pre-calcining; S3: Powder 1 of S1 and powder 2 of S2 are mixed in a mass ratio of 1:12-16, lithium nitrate powder is added in a molar ratio of 0.01-0.05 to powder 1, a solvent is added, and a slurry is obtained by grinding; S4: Pour the slurry of S3 into a mold with a diameter of 10 mm, put the mold into a heating ring, fix it on a uniaxial press, press it, cold sinter it, cool it down and demould it to get a sample, and then anneal it to get a low-dielectric ceramic.

2. The method for preparing a low dielectric ceramic according to claim 1, characterized in that: The ball milling time in S1 is 6 hours, the drying temperature is 100° C., the pre-calcination temperature is 900-1000° C., and a 200-mesh sieve is used in the screening process.

3. The method for preparing a low dielectric ceramic according to claim 1, characterized in that: In S2, the ball milling time is 6 h, the drying temperature is 100 °C, the pre-calcination temperature is 700-800 °C, and a 200-mesh sieve is used in the screening process.

4. The method for preparing a low dielectric ceramic according to claim 1, characterized in that: The solvent in S3 is water or acetic acid; the slurry is a powder with a water / acid content of 8-12 wt.%.

5. The method for preparing a low dielectric ceramic according to claim 1, characterized in that: During the pressing process in S4, the uniaxial press applies a pressure of 100-200 MPa, the holding time is 10-15 min, the speed is 8-10°C / min, the temperature during the cold sintering process is 190-250°C, the sintering time is 1-2 h; the annealing temperature is 600-700°C, and the annealing time is 1-6 h.

6. A low dielectric ceramic obtained according to a preparation method according to any one of claims 1 to 5.

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