Continuous phase evolution microwave dielectric ceramic material, preparation method and application thereof

Abstract

This invention discloses a continuous phase evolution microwave dielectric ceramic material, its preparation method, and its application, belonging to the field of ceramic materials technology. The continuous phase evolution microwave dielectric ceramic material is characterized by having the general chemical formula (1- x Li3MgAO5- x Li₂BO₃, where A is Nb 5+ Ta 5+ or Sb 5+ One or a mixture of two pentavalent ions, where B is Ti. 4+ Sn 4+ or Zr 4+ One or a mixture of two tetravalent ions; x The value range is 0.7≤ x ≤0.9. The crystal phase of microwave dielectric ceramic materials varies with... x As the value increases, the phase continuously evolves from cubic rock salt to monoclinic rock salt. The continuous phase evolution microwave dielectric ceramic material, its preparation method, and its application described in this invention can solve the problems of low quality factor and poor wide-range adjustment of dielectric constant in existing microwave dielectric ceramic materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic materials, and particularly relates to a continuous phase evolution microwave dielectric ceramic material, a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of modern communication technology, the performance requirements of microwave dielectric ceramic materials for high-frequency electronic devices such as 5G communication, satellite communication and radar systems are increasingly stringent. As the core functional material of radio frequency / microwave devices, the dielectric performance of microwave dielectric ceramic directly determines the working efficiency, frequency selectivity and environmental stability of key devices such as filters, resonators and dielectric antennas. As the core material of microwave devices, the dielectric performance of microwave dielectric ceramic directly determines the working efficiency and stability of the device. Excellent microwave dielectric ceramic materials should have high quality factor (low dielectric loss), appropriate relative dielectric constant ε r and near-zero resonant frequency temperature coefficient and other characteristics.

[0003] Currently, with the expansion of 5G communication to the millimeter wave frequency band and the pre-research of 6G communication technology, the development of microwave dielectric ceramic materials with low dielectric constant ε r ≤20) and ultra-high quality factor has become a key research and development direction in this field to meet the stringent requirements of high frequency, miniaturization and high-speed transmission. The quality factor value of microwave dielectric ceramic material is directly related to the insertion loss and frequency selectivity of the device, that is The greater the value, the lower the insertion loss of the filter, the higher the signal transmission efficiency, and the more excellent the frequency selection characteristics of the device. The resonant frequency temperature coefficient close to zero means that the center frequency of the device changes very little with the ambient temperature, ensuring the working stability and reliability of the system in a wide temperature range. Therefore, the development of new microwave dielectric ceramic materials with adjustable dielectric constant, ultra-low dielectric loss and near-zero resonant frequency temperature coefficient at microwave and millimeter wave frequencies has important strategic significance and great application value for promoting the development of next-generation communication technology.

[0004] Currently, commercial microwave dielectric ceramic materials on the market mainly include perovskite type (such as BaTi4O9 system, Ba(Zn 1 / 3 Nb 2 / 3 )O3 system), tungsten bronze type (such as Ba 6-3x R 8+2x Ti 18 O 54The traditional ceramic systems include perovskite type (such as BaTiO3 system), spinel type (such as MgAl2O4 system) and other structural systems. However, these traditional ceramic systems still face many technical bottlenecks in response to the emerging high-frequency application requirements: first, high quality factor and wide range of adjustable dielectric constant are often mutually restricted, and it is difficult to achieve synergistic optimization in the same system; second, the accurate regulation and stability of the temperature coefficient of the resonant frequency are still key technical difficulties, especially under the conditions of wide temperature and wide frequency band; third, the relative dielectric constant of the traditional materials is generally high (mostly greater than 20), which is not suitable for the miniaturization and high-frequency requirements of the millimeter wave system; finally, the density of the traditional materials is high, which is difficult to meet the requirements of the multiple-input multiple-output (MIMO) array antenna in the modern millimeter wave system, and some traditional formulations still contain toxic heavy metal elements such as lead, cadmium and mercury, which do not meet the increasingly stringent environmental protection regulations, limiting their wide application in consumer electronics and green communication fields. Therefore, it is urgent to develop a new type of microwave dielectric ceramic material to solve the above-mentioned problems. SUMMARY

[0005] The purpose of the present application is to provide a continuous phase evolution microwave dielectric ceramic material, its preparation method and application, which solves the problems of low quality factor and poor dielectric constant wide range adjustment of the existing microwave dielectric ceramic material.

[0006] To achieve the above-mentioned purpose, the present application provides a continuous phase evolution microwave dielectric ceramic material, the chemical general formula is (1- x Li3MgAO5- x Li2BO3, wherein A is one or a mixture of two of the following five-valent ions: Nb 5+ , Ta 5+ or Sb 5+ , and B is one or a mixture of two of the following four-valent ions: Ti 4 + , Sn 4+ or Zr 4+ . x The value range is 0.7≤ x ≤0.9.

[0007] Preferably, the crystal phase of the microwave dielectric ceramic material continuously evolves from cubic rock salt phase to monoclinic rock salt phase with the increase of the value of x. x

[0008] The preparation method of the above-mentioned continuous phase evolution microwave dielectric ceramic material comprises the following steps:

[0009] S1, batching; the raw materials are selected from Mg(OH)2·4MgCO3·5H2O and Li2CO3, niobium pentoxide, tantalum pentoxide and antimony pentoxide, and titanium dioxide, tin dioxide and zirconium dioxide according to the chemical general formula.

[0010] ​S2, primary ball milling; the raw materials are mixed, and primary ball milling is performed in zirconium dioxide balls and anhydrous ethanol to obtain primary ball milling materials;

[0011] S3, primary drying and sieving; the primary ball milling materials are dried and sieved through a 100-mesh sieve to obtain primary dry powders;

[0012] S4, pre-sintering; the primary dry powders are placed in an alumina crucible for pre-sintering to obtain pre-sintered powders;

[0013] S5, secondary ball milling; the pre-sintered powders are mixed with zirconium dioxide balls and anhydrous ethanol for secondary ball milling to obtain secondary ball milling materials;

[0014] S6, secondary drying and sieving; the secondary ball milling materials are dried and sieved through a 100-mesh sieve to obtain secondary dry powders;

[0015] S7, granulation and die pressing; the secondary dry powders are mixed with a polyvinyl alcohol aqueous solution for granulation, and the granulation size is 90-100 mesh; the granules are placed in a molding die for dry pressing under a pressure of 16 MPa to obtain a green body;

[0016] S8, sintering; the green body is buried and placed in a sintering furnace for sintering under inert gas protection and annealing to obtain a microwave dielectric ceramic material.

[0017] Preferably, in S1, the purity of Mg(OH)2·4MgCO3·5H2O raw materials is greater than 98.0%, and the purity of Li2CO3, niobium pentoxide, tantalum pentoxide, antimony pentoxide, titanium dioxide, tin dioxide and zirconium dioxide raw materials is greater than 99.9%.

[0018] Preferably, in S2, the mass ratio of raw materials, milling balls and anhydrous ethanol in primary ball milling is 1:(4-6):(2-3), and the primary ball milling time is 5-7 hours.

[0019] Preferably, in S4, the pre-sintering temperature is 900-1000 ℃, and the pre-sintering time is 3-5 hours.

[0020] Preferably, in S5, the mass ratio of raw materials, milling balls and anhydrous ethanol in secondary ball milling is 1:(3-5):(2-3), and the secondary ball milling time is 2-4 hours.

[0021] Preferably, in S8, the specific operation of burying the green body is as follows: the green body is stacked on a zirconium plate, a quartz crucible is inverted on the green body, high-purity lithium oxide powder is filled in the gap between the crucible and the zirconium plate and compacted, a layer of high-purity zirconium oxide powder is covered on the compacted lithium oxide powder, and the layer is compacted again.

[0022] Preferably, in step S8, the heating rate during sintering is 2 ℃ / min to 4 ℃ / min, the sintering temperature is 1220 ℃ to 1320 ℃, and the sintering time is 4 hours to 6 hours; the temperature is then reduced to 850 ℃ at a rate of 3 ℃ / min and held for 4 hours for annealing.

[0023] The aforementioned continuous phase evolution microwave dielectric ceramic materials are used in resonators, filters, and antennas in 5G / 6G communications, satellite internet, and millimeter-wave radar systems.

[0024] The advantages and positive effects of the continuous phase evolution microwave dielectric ceramic material, its preparation method, and its application described in this invention are as follows:

[0025] 1. This invention involves doping microwave dielectric ceramic materials with pentavalent ions (Nb) of similar ionic radii. 5+ Ta 5+ Sb 5+ ) and tetravalent ions with similar ionic radii (Ti) 4+ Sn 4+ or Zr 4+ ),along with x The variation in values ​​enables a continuous evolution from cubic rock salt facies to monoclinic rock salt facies. The continuous phase evolution interface formed at the atomic scale not only achieves ultra-high... This not only improves the value of the composite material but also fundamentally avoids the additional dielectric relaxation loss caused by the introduction of phase interfaces in traditional multiphase composite materials.

[0026] 2. This invention solves the common problem of lithium volatilization in the high-temperature preparation of lithium-based ceramics by embedding lithium oxide and zirconium oxide and sintering under a protective atmosphere. This ensures high densification of the ceramic material and accurate stoichiometry, resulting in a theoretical relative density exceeding 95%, significantly improving the yield and reliability of the product. Simultaneously, the bulk density is 3.19~3.58 g / cm³. 3 Within a lower range, it is suitable for applications of millimeter-wave MIMO array antennas.

[0027] 3. Compared with traditional perovskite ceramics, the microwave dielectric ceramic material of this invention has a sintering temperature that is reduced by approximately 50-100°C, and a wider formulation window (0.70 ≤ x With a particle size ≤ 0.90, it exhibits greater tolerance for compositional deviations in industrial production, effectively reducing energy consumption, improving yield, and lowering costs. The sintering temperature of the microwave dielectric ceramic material of this invention is 1200~1300℃, a wide range, providing good process adaptability. The microwave dielectric ceramic material of this invention is completely free of heavy metals such as lead, cadmium, and mercury, making it environmentally friendly.

[0028] 4、The microwave dielectric ceramic material has a quality factor of 95320 GHz~135430 GHz, a relative dielectric constant ε r The resonant frequency temperature coefficient is adjustable between 13.8~23.2 wide range The resonant frequency temperature coefficient is adjustable between 13.8~23.2 wide range

[0029] 5、The microwave dielectric ceramic material has a thermal expansion coefficient matched with commonly used oxide substrates, can be directly integrated into LTCC / HTCC co-firing or single-piece dielectric filter, antenna array and other high-frequency integrated processes, and significantly simplifies device design.

[0030] The technical solutions of the present application will be further described in detail below with the help of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The XRD patterns of the microwave dielectric ceramic materials prepared for example 2, example 3, example 5, example 6 of the present application;

[0032] Figure 2 The transmission electron microscope photos of the microwave dielectric ceramic material prepared for example 3 of the present application; (a) is the HRTEM image of the crystal phase axis direction, (b) is the HRTEM image of the phase evolution interface, (c) is the enlarged and denoised HRTEM image of the phase evolution interface, and (d) is the selected area electron diffraction (SAED) image of the phase evolution interface, and the inserted image is the Fourier transform (FFT) image of the region;

[0033] Figure 3 The scanning electron microscope photos of the microwave dielectric ceramic material prepared for example 8 of the present application. DETAILED DESCRIPTION

[0034] In the present application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. If there is any inconsistency, the meaning as explained in the present specification or the meaning derived from the content described in the present specification shall prevail. In addition, the terms used herein are only for the purpose of describing the embodiments of the present application, and are not intended to limit the present application.

[0035] The embodiments of the present application will be described in detail below with reference to the drawings.

[0036] A continuous phase evolution microwave dielectric ceramic material, the chemical general formula is (1- x Li3MgAO5- x Li2BO3, wherein A is Nb 5+ , Ta​5+ or Sb 5+ a mixture of one or two of the pentavalent ions, B is Ti 4+ , Sn 4+ or Zr 4+ a mixture of one or two of the tetravalent ions; x 0.7≤ x 0.9.

[0037] The crystal phase of the microwave dielectric ceramic material continuously evolves from a cubic rock salt phase to a monoclinic rock salt phase with the increase of the value of x. x The crystal phase of the microwave dielectric ceramic material continuously evolves from a cubic rock salt phase to a monoclinic rock salt phase with the increase of the value of x.

[0038] The preparation method of the continuously phase-evolved microwave dielectric ceramic material comprises the following steps:

[0039] S1, batching; raw materials are weighed according to a chemical formula, and the raw materials are selected from Mg(OH)2·4MgCO3·5H2O and Li2CO3, niobium pentoxide, tantalum pentoxide and antimony pentoxide, and titanium dioxide, tin dioxide and zirconium dioxide.

[0040] The purity of the Mg(OH)2·4MgCO3·5H2O raw material is greater than 98.0%, and the purity of the Li2CO3, niobium pentoxide, tantalum pentoxide and antimony pentoxide, and titanium dioxide, tin dioxide and zirconium dioxide raw materials is greater than 99.9%.

[0041] S2, primary ball milling; the raw materials are mixed, zirconium dioxide balls are used as milling balls, and primary ball milling is performed in anhydrous ethanol to obtain a primary ball milled material.

[0042] The mass ratio of the raw materials, the milling balls and the anhydrous ethanol in the primary ball milling is 1: (4-6): (2-3), and the primary ball milling time is 5-7 hours.

[0043] S3, primary drying and sieving; the primary ball milled material is dried and sieved through a 100-mesh sieve to obtain a primary dried powder.

[0044] S4, pre-sintering; the primary dried powder is placed in an alumina crucible and pre-sintered to obtain a pre-sintered powder.

[0045] The pre-sintering temperature is 900-1000℃, and the pre-sintering time is 3-5 hours.

[0046] S5, secondary ball milling; the pre-sintered powder is uniformly mixed with zirconium dioxide balls and anhydrous ethanol for secondary ball milling to obtain a secondary ball milled material.

[0047] The mass ratio of the raw materials, the milling balls and the anhydrous ethanol in the secondary ball milling is 1: (3-5): (2-3), and the secondary ball milling time is 2-4 hours.

[0048] S6, secondary drying and sieving; the secondary ball mill is dried and sieved through a 100 mesh sieve to obtain a secondary dried powder.

[0049] S7, granulation and die molding; the secondary dried powder is mixed with a polyvinyl alcohol aqueous solution to form granules with a size of 90-100 mesh; the granules are placed in a molding die and dry-pressed at a pressure of 16 MPa to obtain a green body. The green body is a cylinder with a size of Φ12 mm x 6 mm.

[0050] S8, sintering; the green body is buried and placed in a sintering furnace for sintering and annealing to obtain a microwave dielectric ceramic material.

[0051] The specific operation of burying the green body is as follows: the green body is stacked on a zirconium plate, a quartz crucible is inverted on the green body, high-purity lithium oxide powder is filled in the gap between the crucible and the zirconium plate and compacted, and a layer of high-purity zirconium oxide powder is covered on the compacted lithium oxide powder and compacted again. The green body is in a lithium-rich atmosphere during sintering, effectively inhibiting the volatilization of lithium oxide under high-temperature conditions, thereby obtaining a dense ceramic structure.

[0052] The heating rate during sintering is 2-4 ℃ / min, the sintering temperature is 1220-1320 ℃, and the sintering time is 4-6 hours. The temperature is lowered to 850 ℃ at a rate of 3 ℃ / min, and annealing is performed for 4 hours.

[0053] The continuous phase evolution microwave dielectric ceramic material is applied in resonators, filters and antennas in 5G / 6G communication, satellite internet and millimeter wave radar systems.

[0054] Example 1

[0055] The chemical formula of the continuous phase evolution microwave dielectric ceramic material in this example is 0.3Li3MgNb 0.75 Ta 0.25 O5-0.7Li2Ti 0.95 Sn 0.05 O3.

[0056] The basic magnesium carbonate (Mg(OH)2·4MgCO3·5H2O), Li2CO3, Nb2O5, Ta2O5, TiO2 and SnO2 are prepared in a mass ratio of 13.31%, 38.80%, 13.66%, 7.57%, 24.25% and 2.41%, respectively.

[0057] The obtained mixture is ground with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent, and the weight ratio of the mixture: grinding balls: ethanol is 1:5:2. The mixture is ground for 5 hours to obtain a uniformly mixed mixture.

[0058] The mixture after ball milling is dried at 80°C and sieved through a 100-mesh screen to obtain dry powder.

[0059] The sample is then pre-fired at 1000°C for 3 hours to obtain a sample fired block.

[0060] The sample fired block is crushed, and zirconium dioxide balls are used as the ball milling medium and anhydrous ethanol as the solvent, and the mixture: milling ball: ethanol is ground at a weight ratio of 1:5:2 for 2 hours.

[0061] The mixture is dried and granulated, and the granule size is controlled at 100 mesh. The granules are placed in a molding die and dry-pressed at a pressure of 16 MPa to obtain a Φ12 mm x 6 mm cylindrical green body.

[0062] The green body is ground with lithium oxide powder and zirconium oxide powder, and sintered at a temperature of 1230°C in a protective atmosphere for 6 hours. The temperature is then lowered to 850°C at a rate of 3°C / min, and annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0063] Example 2

[0064] In this example, the continuous phase of the microwave dielectric ceramic material has the chemical formula 0.2Li3MgNb 0.85 Ta 0.15 O5-0.8Li2Ti 0.85 Sn 0.15 O3.

[0065] The basic magnesium carbonate (Mg(OH)2·4MgCO3·5H2O), Li2CO3, Nb2O5, Ta2O5, TiO2, and SnO2 are prepared according to a mass ratio of 9.60%, 40.17%, 11.17%, 3.28%, 26.84%, and 8.94%, respectively.

[0066] The obtained mixture is ground with zirconium dioxide balls as the ball milling medium and anhydrous ethanol as the solvent, and the mixture: milling ball: ethanol is ground at a weight ratio of 1:5:3 for 6 hours to obtain a uniformly mixed mixture.

[0067] The mixture after ball milling is dried at 80°C and sieved through a 100-mesh screen to obtain dry powder.

[0068] The sample is then pre-fired at 950°C for 5 hours to obtain a sample fired block.

[0069] The sample fired block is crushed, and zirconium dioxide balls are used as the ball milling medium and anhydrous ethanol as the solvent, and the mixture: milling ball: ethanol is ground at a weight ratio of 1:4:3 for 4 hours.

[0070] The dry granulation process is carried out, and the granulation size is controlled to be 100 meshes. The granules are put into a molding mold to be dry-pressed to form a Φ12mm*6mm cylindrical green body under a pressure of 16MPa.

[0071] The green body is ground with lithium oxide powder and zirconium oxide powder, and sintered at a temperature of 1260°C in a protective atmosphere for 5 hours. Then, the temperature is decreased to 850°C at a rate of 3°C / min, and annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0072] Example 3

[0073] The continuous phase evolution microwave dielectric ceramic material in this example has a chemical formula of 0.15Li3MgNbO5-0.85Li2TiO3-SnO2. 0.95 0.05 O3.

[0074] The basic magnesium carbonate (Mg(OH)2*4MgCO3*5H2O), Li2CO3, Nb2O5, TiO2 and SnO2 are prepared according to a mass ratio of 7.88%, 42.97%, 10.79%, 34.89% and 3.47%, respectively.

[0075] The obtained mixture is ground with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent according to a weight ratio of the mixture: grinding balls: ethanol of 1:6:3 for 7 hours, and finally a uniformly mixed mixture is obtained.

[0076] The ground mixture is dried at 80°C and sieved through a 100 mesh sieve to obtain dry powder.

[0077] Then, the sample block is obtained by pre-sintering at 980°C for 4 hours.

[0078] The sample block is crushed, and the mixture is ground with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent according to a weight ratio of the mixture: grinding balls: ethanol of 1:3:3 for 3 hours.

[0079] The dry granulation process is carried out, and the granulation size is controlled to be 100 meshes. The granules are put into a molding mold to be dry-pressed to form a Φ12mm*6mm cylindrical green body under a pressure of 16MPa.

[0080] The green body is ground with lithium oxide powder and zirconium oxide powder, and sintered at a temperature of 1270°C in a protective atmosphere for 4 hours. Then, the temperature is decreased to 850°C at a rate of 3°C / min, and annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0081] Example 4

[0082] ​The continuous phase evolution microwave dielectric ceramic material in this embodiment has a chemical formula of 0.1Li3MgNb 0.65 Sb 0.35 O5-0.9Li2TiO3.

[0083] The basic magnesium carbonate (Mg(OH)2·4MgCO3·5H2O), Li2CO3, Nb2O5, Sb2O5 and TiO2 are prepared in a mass ratio of 5.60%, 44.72%, 4.98%, 3.26% and 41.44%, respectively.

[0084] The obtained mixture is ground for 7 hours with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent, and the weight ratio of the mixture: grinding balls: ethanol is 1:4:3.

[0085] The ground mixture is dried at 80°C and sieved through a 100-mesh screen to obtain dry powder.

[0086] Then, the sample is pre-fired at 940°C for 4 hours to obtain a sample block.

[0087] The sample block is crushed, and the crushed sample is ground for 4 hours with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent, and the weight ratio of the mixture: grinding balls: ethanol is 1:5:3.

[0088] The dry powder is granulated, and the granulation size is controlled to be 100 mesh. The granules are placed in a molding die and dry-pressed at a pressure of 16 MPa to obtain a Φ12mm×6mm cylindrical green body.

[0089] The green body is ground with lithium oxide powder and zirconium oxide powder, and sintered in a protective atmosphere at a temperature of 1290°C for 5 hours. Then, the temperature is lowered to 850°C at a rate of 3°C / min, and the sintered body is annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0090] Example 5

[0091] The continuous phase evolution microwave dielectric ceramic material in this embodiment has a chemical formula of 0.25Li3MgNb 0.65 Ta 0.35 O5-0.75Li2Ti 0.75 Zr 0.25 O3.

[0092] The basic magnesium carbonate (Mg(OH)2·4MgCO3·5H2O), Li2CO3, Nb2O5, Ta2O5, TiO2 and ZrO2 are prepared in a mass ratio of 11.23%, 38.42%, 9.98%, 8.93%, 20.76% and 10.68%, respectively.

[0093] The obtained mixture was ground for 5 hours with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent, according to the weight ratio of the mixture: grinding balls: ethanol of 1:6:2, and finally a uniformly mixed mixture was obtained.

[0094] The ground mixture was dried at 80°C and sieved through a 100-mesh screen to obtain dry powder.

[0095] Then, the sample was pre-fired at 920°C for 3 hours to obtain a sample fired block.

[0096] The sample fired block was crushed, and the crushed sample was ground for 3 hours with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent, according to the weight ratio of the mixture: grinding balls: ethanol of 1:5:3.

[0097] Drying and granulation were performed, and the granulation size was controlled at 100 mesh. The granules were placed into a molding die and dry-pressed at a pressure of 16 MPa to obtain a Φ12 mm x 6 mm cylindrical green body.

[0098] The green body was ground with lithium oxide powder and zirconium oxide powder, and sintered in a protective atmosphere at a temperature of 1320°C for 5 hours. Then, the temperature was decreased to 850°C at a rate of 3°C / min, and annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0099] Example 6

[0100] In this example, the continuous phase evolved microwave dielectric ceramic material has the chemical formula of 0.1Li3MgNb 0.85 Sb 0.15 O5-0.9Li2Sn 0.75 Zr 0.25 O3.

[0101] The basic magnesium carbonate (Mg(OH)2·4MgCO3·5H2O), Li2CO3, Nb2O5, Sb2O5, SnO2, and ZrO2 were prepared according to the mass ratio of 4.22%, 33.66%, 4.90%, 1.05%, 44.14%, and 12.03%, respectively.

[0102] The obtained mixture was ground for 6 hours with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent, according to the weight ratio of the mixture: grinding balls: ethanol of 1:4:3, and finally a uniformly mixed mixture was obtained.

[0103] The ground mixture was dried at 80°C and sieved through a 100-mesh screen to obtain dry powder.

[0104] Then, the sample was pre-fired at 900°C for 4 hours to obtain a sample fired block.

[0105] The sample block was crushed, zirconium dioxide balls were used as the ball milling medium, anhydrous ethanol was used as the solvent, and the mixture: milling ball: ethanol was ground at a weight ratio of 1:4:2 for 2 hours.

[0106] The dried and granulated mixture was dry-pressed into a molding die at a pressure of 16 MPa to obtain a cylindrical green body with a diameter of 12 mm and a height of 6 mm.

[0107] The green body was ground with lithium oxide powder and zirconium oxide powder, and sintered at a temperature of 1300 °C in a protective atmosphere for 4 hours, and then cooled to 850 °C at a rate of 3 °C / min and annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0108] Example 7

[0109] The continuous phase evolution microwave dielectric ceramic material in this example has the chemical formula 0.2Li3MgNb 0.85 Sb 0.15 O5-0.8Li2Sn 0.85 Zr 0.15 O3.

[0110] The basic magnesium carbonate (Mg(OH)2·4MgCO3·5H2O), Li2CO3, Nb2O5, Sb2O5, SnO2 and ZrO2 were prepared in a mass ratio of 7.52%, 31.46%, 8.74%, 1.88%, 39.67% and 10.73%, respectively.

[0111] The obtained mixture was ground with zirconium dioxide balls as the ball milling medium, anhydrous ethanol as the solvent, and the mixture: milling ball: ethanol was ground at a weight ratio of 1:6:2 for 7 hours, and finally a uniformly mixed mixture was obtained.

[0112] The ground mixture was dried at 80 °C and sieved through a 100 mesh sieve to obtain the dry powder.

[0113] Then, the sample block was pre-sintered at 970 °C for 5 hours to obtain the sample block.

[0114] The sample block was crushed, zirconium dioxide balls were used as the ball milling medium, anhydrous ethanol was used as the solvent, and the mixture: milling ball: ethanol was ground at a weight ratio of 1:3:3 for 4 hours.

[0115] The dried and granulated mixture was dry-pressed into a molding die at a pressure of 16 MPa to obtain a cylindrical green body with a diameter of 12 mm and a height of 6 mm.

[0116] The green body is ground by lithium oxide powder and zirconium oxide powder, and sintered at a temperature of 1220 ℃ in a protective atmosphere for 6 hours; then cooled to 850 ℃ at a rate of 3°C / min, and annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0117] Example 8

[0118] The continuous phase evolution microwave dielectric ceramic material in the embodiment has a chemical formula of 0.15Li3MgNb 0.65 Ta 0.35 O5-0.85Li2SnO3.

[0119] The basic magnesium carbonate (Mg(OH)2·4MgCO3·5H2O), Li2CO3, Nb2O5, Ta2O5 and SnO2 are prepared according to a mass ratio of 5.91%, 32.20%, 5.25%, 4.70% and 51.94%, respectively.

[0120] The obtained mixture is ground with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent according to a weight ratio of the mixture: grinding balls: ethanol of 1:4:2 for 6 hours, and finally a uniformly mixed mixture is obtained.

[0121] The ground mixture is dried at 80 ℃ and sieved through a 100 mesh sieve to obtain dry powder.

[0122] Then, the sample is pre-sintered at 990 ℃ for 3 hours to obtain a sample block.

[0123] The sample block is crushed, and ground with zirconium dioxide balls as the grinding medium and anhydrous ethanol as the solvent according to a weight ratio of the mixture: grinding balls: ethanol of 1:4:2 for 3 hours.

[0124] The sample is dried and granulated, and the granulation size is controlled at 100 mesh. The granules are placed into a molding mold and dry-pressed at a pressure of 16 MPa to obtain a Φ12 mm×6 mm cylindrical green body.

[0125] The green body is ground by lithium oxide powder and zirconium oxide powder, and sintered at a temperature of 1280 ℃ in a protective atmosphere for 5 hours; then cooled to 850 ℃ at a rate of 3°C / min, and annealed for 4 hours to obtain the final microwave dielectric ceramic material.

[0126] The chemical formula and the mass percentage of raw materials of the microwave dielectric ceramic materials in Examples 1-8 are shown in Table 1.

[0127] Table 1 Chemical formula and mass percentage of raw materials of Examples 1-8 (%)

[0128] ;

[0129] XRD analysis was performed on the microwave dielectric ceramic materials prepared in Examples 2, 3, 5, and 6. The XRD patterns are shown below. Figure 1 As shown. In (1- x Li3MgAO5- x Li2BO3 (0.7≤ x In microwave dielectric ceramic materials with a radius ≤0.9, A consists of pentavalent ions (Nb ions) with similar ionic radii. 5+ Ta 5+ Sb 5+ Both B and Ti are tetravalent ions with similar ionic radii (Ti). 4+ Sn 4+ or Zr 4+ Microwave dielectric ceramic materials with different ion combinations essentially form continuous solid solutions, and their phase composition and degree of phase transformation are mainly determined by... x The value is determined by [the value]. With [the change]... x As the value increased from 0.75 to 0.9, the characteristic peaks of the monoclinic phase gradually increased while those of the cubic phase gradually decreased, indicating that the material underwent a continuous phase evolution process from cubic rock salt to monoclinic rock salt. This was achieved through precise control... x The value allows for controllable adjustment of the degree of phase evolution, unaffected by changes in the specific ion species.

[0130] Figure 2 This is a transmission electron microscope (TEM) image of the microwave dielectric ceramic material prepared in Example 3 of the present invention. Figure 2 As shown, from Figure 2 The high-resolution TEM images in (b) and (c) clearly show that the material exhibits a continuous evolution from a disordered cubic structure to an ordered monoclinic structure at the atomic and nanoscale, without obvious phase interfaces or grain boundary defects during the evolution. Furthermore, the monoclinic phase displays a superlattice (SL) structure. Figure 2 The selected area electron diffraction pattern (d) shows that the ordered monoclinic phase near the continuously evolving structural region exhibits typical superlattice diffraction (SLRs) characteristics, which is due to the B-site ions affecting the Mg... 2+ Locally ordered superlattice structures formed by recombination substitution with A-site ions. This result can also be obtained from... Figure 2 As confirmed by the high-resolution TEM image in (a). It is this continuous evolution superstructure without obvious interfaces that fundamentally avoids the interfacial losses of traditional multiphase composite materials, enabling microwave dielectric ceramic materials to maintain ultra-low dielectric losses while adjusting dielectric parameters over a wide range.

[0131] Figure 3 This is a scanning electron microscope (SEM) image of the microwave dielectric ceramic material prepared in Example 8 of the present invention. Figure 3As shown, the ceramic grains realize full growth and densification by using the protective atmosphere sintering process provided by the application, the microstructure is highly dense, the grain distribution is uniform, the grain boundary is clear, and no defects such as pores and microcracks are found, which indicates that the process described in the application can effectively inhibit lithium evaporation and improve sintering density, and further ensure the low-loss characteristics and long-term reliability of the material.

[0132] The dielectric properties of the microwave dielectric ceramic materials of Examples 1-8 were detected, and the microwave dielectric properties are shown in Table 2.

[0133] Table 2 Microwave dielectric properties of Examples 1-8

[0134] ;

[0135] As can be seen from Table 2, the microwave dielectric ceramic materials of each example have high quality factors The relative dielectric constant is between 95,320 GHz and 135,430 GHz ε r The resonance frequency temperature coefficient is between 13.8 and 23.2 wide ranges The bulk density is between 3.19 and 3.58 g / cm 3 The linear expansion coefficient is in the range of 6.28-7.85 ppm / ℃, which is well matched with the thermal expansion coefficient of commonly used oxide LTCC and HTCC substrates (generally 6-9 ppm / ℃). In particular, Examples 3 and 8 have high values and near-zero values, and low bulk density, and the comprehensive performance meets the application requirements of high frequency, low loss and low density of millimeter wave devices.

[0136] Therefore, by using the continuous phase evolution microwave dielectric ceramic material, the preparation method and the application thereof, the component coefficient x of the material is accurately controlled to drive the material crystal structure to continuously and gradually evolve between the disordered cubic phase and the ordered monoclinic phase; in the transition zone of the phase transition, the material presents a unique continuous phase evolution interface at the atomic scale, which can solve the problems of low quality factor and poor dielectric constant wide range adjustment of existing microwave dielectric ceramic materials.

[0137] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application but not to limit it, although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the application can still be modified or equivalently replaced, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the application.

Claims

1. A microwave dielectric ceramic material with continuous phase evolution, characterized in that: The general chemical formula is (1- x Li3MgAO5- x Li₂BO₃, where A is Nb 5+ Ta 5+ or Sb 5+ One or a mixture of two pentavalent ions, where B is Ti. 4+ Sn 4+ or Zr 4+ One or a mixture of two tetravalent ions; x The value range is 0.7≤ x ≤0.

9.

2. The microwave dielectric ceramic material with continuous phase evolution according to claim 1, characterized in that: The crystal phase of the microwave dielectric ceramic material changes with x As the value increases, it continuously evolves from cubic rock salt facies to monoclinic rock salt facies.

3. A method for preparing a continuous phase evolution microwave dielectric ceramic material according to claim 1 or 2, characterized in that, Includes the following steps: S1. Ingredients: Weigh the raw materials according to the general chemical formula. The raw materials are selected from Mg(OH)2·4MgCO3·5H2O and Li2CO3, niobium pentoxide, tantalum pentoxide and antimony pentoxide, as well as titanium dioxide, tin dioxide and zirconium dioxide. S2. First ball milling: Mix the raw materials and use zirconia balls as milling balls to perform a first ball milling in anhydrous ethanol to obtain the first ball milling material; S3. First drying and sieving: Dry the ball milling material once and sieve it through a 100-mesh sieve to obtain a first-dried powder; S4. Pre-calcination: The dried powder is placed in an alumina crucible and pre-calcined to obtain pre-calcined powder. S5. Secondary ball milling: The pre-calcined powder is mixed with zirconium dioxide balls and anhydrous ethanol and then ball-milled to obtain secondary ball milling material. S6. Secondary drying and sieving: Dry the secondary ball milling material and sieve it through a 100-mesh sieve to obtain secondary dried powder. S7. Granulation and molding: The secondary dried powder is mixed with polyvinyl alcohol aqueous solution and then granulated to a particle size of 90-100 mesh; the granules are placed in a molding die and dry-pressed under a pressure of 16 MPa to obtain a green body; S8. Sintering: The green blank is buried and placed in a sintering furnace for sintering under inert gas protection, and then annealed to obtain microwave dielectric ceramic material.

4. The method for preparing a continuous phase evolution microwave dielectric ceramic material according to claim 3, characterized in that: In S1, the purity of Mg(OH)2·4MgCO3·5H2O raw material is greater than 98.0%, and the purity of Li2CO3, niobium pentoxide, tantalum pentoxide and antimony pentoxide, as well as titanium dioxide, tin dioxide and zirconium dioxide raw materials is greater than 99.9%.

5. The method for preparing a continuous phase evolution microwave dielectric ceramic material according to claim 3, characterized in that: In S2, the mass ratio of raw material, grinding balls and anhydrous ethanol in one ball milling is 1:(4~6):(2~3), and the ball milling time is 5 hours to 7 hours.

6. The method for preparing a continuous phase evolution microwave dielectric ceramic material according to claim 3, characterized in that: In step S4, the pre-firing temperature is 900 ℃~1000 ℃, and the pre-firing time is 3 hours to 5 hours.

7. The method for preparing a continuous phase evolution microwave dielectric ceramic material according to claim 3, characterized in that: In step S5, the mass ratio of raw material, grinding balls and anhydrous ethanol in the secondary ball milling is 1:(3~5):(2~3), and the secondary ball milling time is 2 hours to 4 hours.

8. The method for preparing a continuous phase evolution microwave dielectric ceramic material according to claim 3, characterized in that: In S8, the specific operation of burying the green blank is as follows: the green blank is stacked on a zircon plate, a quartz crucible is placed upside down on top of the green blank, and high-purity lithium oxide powder is filled into the gap between the crucible and the zircon plate and compacted; a layer of high-purity zirconium oxide powder is covered on the compacted lithium oxide powder and compacted again.

9. The method for preparing a continuous phase evolution microwave dielectric ceramic material according to claim 3, characterized in that: In S8, the heating rate during sintering is 2 ℃ / min~4 ℃ / min, the sintering temperature is 1220 ℃~1320 ℃, and the sintering time is 4 hours~6 hours; then the temperature is lowered to 850 ℃ at a rate of 3 ℃ / min and held for 4 hours for annealing.

10. The application of a continuous phase evolution microwave dielectric ceramic material according to claim 1 or 2 in resonators, filters and antennas in 5G / 6G communication, satellite internet and millimeter-wave radar systems.

Images