Barium feldspar-based microwave dielectric ceramic and preparation method thereof

Abstract

The preparation method comprises the following steps: taking BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3 and SiO2 as raw materials, and weighing according to the chemical composition of [Ba1-x (Ca1 / 4Sr1 / 4La1 / 6Sm1 / 6) x] [Al1-y (Nb1 / 6Li1 / 6Mg1 / 6Ti1 / 6B1 / 3) y] 2Si2O8; x is equal to 0.4 to 0.6, and y is equal to 0.5 to 0.7; ball-milling and mixing the weighed raw materials to obtain a premix; the premix is sequentially subjected to calcination, granulation and dry pressing forming treatment, and the celsian-based microwave dielectric ceramic is obtained. The celsian-based microwave dielectric ceramic with low dielectric constant, high quality factor and near-zero temperature coefficient of resonance frequency is prepared.

Description

Barium feldspar-based microwave dielectric ceramics and their preparation methods Technical Field

[0001] This invention relates to the field of microwave dielectric ceramics technology, and in particular to a barium feldspar-based microwave dielectric ceramic and its preparation method. Background Technology

[0002] As communication frequencies expand into the millimeter-wave / submillimeter-wave band, signal wavelengths shorten significantly, placing higher demands on the dielectric properties, thermal stability, and processing adaptability of microwave dielectric materials.

[0003] Millimeter-wave communication uses low dielectric constant (εr < 10) as a core indicator for microwave dielectric ceramics to reduce signal flight time, conductor loss, and surface wave loss. Barium feldspar (BaAl₂Si₂O₈, BAS) has become an ideal candidate material for 5G / 6G high-frequency devices due to its intrinsically low dielectric constant (εr ≈ 6.5), high Q×f value (≈ 90,000 GHz), and low cost. However, its reversible hexagonal monoclinic phase transition accompanied by abrupt volume change severely restricts the dimensional stability of the ceramic, and its negative resonant frequency temperature coefficient (τf ~ -30 ppm / ℃) limits its application in microwave communication.

[0004] Existing research has significantly improved the overall performance of BAS ceramics through phase structure modulation, dielectric property optimization, and low-temperature sintering strategies, basically meeting the process requirements of microwave components and LTCC. However, while single-element doping (such as Ni2+, Li+) can effectively lower the sintering temperature and promote the transformation from hexagonal to monoclinic phase by introducing oxygen vacancies, its controllability is limited and often accompanied by side effects. For example, substitution to reduce the dielectric constant (εr) often leads to a further increase in the negative value of the frequency temperature coefficient (τf). This exposes the limitations of traditional "single-point" doping in the control of microwave dielectric properties. While composite techniques (such as introducing Si3N4) can improve the mechanical or thermal properties of materials to some extent, the introduction of a second phase often results in a decrease in Q×f at the expense of material properties.

[0005] Overall, existing research largely relies on external stimuli or local structural modifications, making it difficult to achieve synergistic optimization of dielectric properties based on the intrinsic characteristics of materials. This may even introduce new heterogeneous interface losses, limiting its application in the millimeter-wave band. Summary of the Invention

[0006] This invention provides a barium feldspar-based microwave dielectric ceramic and its preparation method, which can obtain barium feldspar-based microwave dielectric ceramics with low dielectric constant, high quality factor and near-zero resonant frequency temperature coefficient.

[0007] On one hand, the present invention provides a method for preparing barium feldspar-based microwave dielectric ceramics, the method comprising the following steps: using BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3, and SiO2 as raw materials, according to [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y The chemical composition of 2Si2O8 was weighed, where x = 0.4-0.6 and y = 0.5-0.7. After weighing, the raw materials were ball-milled to obtain a premix. The premix was then subjected to calcination, granulation, and dry pressing to obtain barium feldspar-based microwave dielectric ceramic.

[0008] Further, the step of sequentially calcining, granulating, and dry-pressing the premixed material to obtain barium feldspar-based microwave dielectric ceramic includes: calcining the premixed material at high temperature to obtain a pre-calcined material; placing the pre-calcined material in a ball mill for secondary ball milling to obtain a milled material; adding a binder to the milled material and performing spray granulation to obtain a granulated material; placing the granulated material in a mold and preparing a green body by dry pressing; and calcining the green body at high temperature to remove the binder from the green body, thereby obtaining the barium feldspar-based microwave dielectric ceramic.

[0009] Further, the step of subjecting the green blank to high-temperature calcination to remove the binder from the green blank and obtaining the barium feldspar-based microwave dielectric ceramic includes: subjecting the green blank to high-temperature calcination to remove the binder from the green blank; subjecting the green blank to high-temperature sintering, and holding it at a preset temperature for a preset time before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic.

[0010] Furthermore, the grinding media for ball milling the weighed raw materials are zirconium oxide grinding balls and deionized water, and the ball milling time is 16-20 hours.

[0011] Further, the step of calcining the premix at high temperature to obtain a pre-calcined material includes: calcining the premix at 750-900°C and holding it at that temperature for 3-6 hours to obtain the pre-calcined material.

[0012] Furthermore, the grinding media for the secondary ball milling of the pre-burned material are zirconium oxide grinding balls and deionized water, and the ball milling time is 20-24 hours.

[0013] Furthermore, the adhesive is a mixture of polyvinyl alcohol and polyethylene glycol, and the mass ratio of polyvinyl alcohol to polyethylene glycol is 4:1, and the mass of the adhesive is 2-3% of the mass of the ball milling material.

[0014] Furthermore, the pressure of the dry pressing is 200-300 MPa.

[0015] Further, the step of subjecting the green blank to high-temperature calcination to remove the binder from the green blank includes: subjecting the green blank to high-temperature calcination at 400-800°C to remove the binder from the green blank; the step of subjecting the green blank to high-temperature sintering and holding it at a preset temperature for a preset time before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic includes: subjecting the green blank to high-temperature sintering at 1050-1250°C and holding it at 1050-1250°C for 3-6 hours before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic.

[0016] On the other hand, the present invention provides a barium feldspar-based microwave dielectric ceramic, which is prepared by the above-described preparation method.

[0017] This invention has the following beneficial effects: This invention uses BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3, and SiO2 as raw materials, according to [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y The chemical composition of 2Si₂O₈ was weighed; where x = 0.4-0.6, y = 0.5-0.7; then the weighed raw materials were ball-milled to obtain a premix; the premix was then subjected to calcination, granulation, and dry pressing to obtain barium feldspar-based microwave dielectric ceramics. This invention is based on the combined rule of ionic radius and valence in the Ba₂O₈ composition of barium feldspar. 2+ And Al 3+ The location was simultaneously replaced by multiple other elements, resulting in a chemical composition of [Ba]. 1-x (Ca1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6Ti 1 / 6 B 1 / 3 ) y Barium feldspar-based microwave dielectric ceramics based on Si₂O₈ were obtained by adjusting the doping amounts of various substitution elements, setting x=0.4-0.6 and y=0.5-0.7, resulting in BAS-based ceramics with excellent microwave dielectric properties. These ceramics exhibited a dielectric constant of 6.5-7.5, a quality factor Q×f greater than 55000, and a resonant frequency temperature coefficient τf < ±10ppm / ℃ (between -30 and 130℃). This demonstrated the synergistic optimization of low dielectric constant, high quality factor, and near-zero resonant frequency temperature coefficient in barium feldspar-based microwave dielectric ceramics. Attached Figure Description

[0018] To more clearly illustrate the technical solution of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 is a flowchart of a method for preparing a barium feldspar-based microwave dielectric ceramic according to an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0022] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0023] As shown in Figure 1, this embodiment provides a method for preparing barium feldspar-based microwave dielectric ceramics, including the following steps: S1, using BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3, and SiO2 as raw materials, according to [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y S1. Weigh the chemical composition of 2Si2O8; where x=0.4-0.6, y=0.5-0.7; S2. After weighing, the raw materials are ball-milled to obtain a premix; S3. The premix is ​​calcined, granulated and dry-pressed sequentially to obtain barium feldspar-based microwave dielectric ceramic.

[0024] This embodiment uses BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3, and SiO2 as raw materials, and follows the [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) yThe chemical composition of 2Si2O8 was weighed; the mass ratio of various compounds was controlled so that x=0.4-0.6 and y=0.5-0.7; then the various weighed raw materials were mixed and placed in a ball mill for ball milling to obtain a premix of various compounds; then the premix was calcined, granulated and dry pressed in sequence to obtain a barium feldspar-based microwave dielectric ceramic with low dielectric constant, high quality factor and near-zero resonant frequency temperature coefficient.

[0025] This embodiment utilizes the ultra-high configurational entropy generated by multi-principal element solid solution as a powerful thermodynamic driving force for the formation of a stable single-phase solid solution and the suppression of element diffusion and segregation. This is because the high entropy effect specifically refers to the phenomenon in a system where multiple elements are mixed in equal proportions, and high mixing entropy dominates the thermodynamic process, suppressing the formation of intermediate compounds and promoting the stability of simple solid solution phases. The resulting lattice distortion effect, due to the chaotic lattice environment and differences in the binding forces between different atoms, requires atomic diffusion to overcome higher energy barriers and more complex paths, reducing the atomic diffusion rate and improving the thermal stability of the material. In addition, the high entropy generation introduces severe local lattice strain and distortion when elements of different atomic sizes occupy the same lattice position. Furthermore, when multiple elements form a solid solution, a synergistic and enhancing nonlinear composite effect is generated, achieving a performance customization of "1+1>2". It is these unique effects that provide the possibility for synergistically optimizing the performance of materials.

[0026] The addition of MgO can lower the sintering temperature and promote the transformation of the hexagonal phase to the monoclinic phase. Appropriate amounts of MgO can effectively promote the growth of monoclinic barium feldspar grains. Sm... 3+ It can effectively promote the transition of BAS from hexagonal phase to monoclinic phase, improve the quality factor (Q×f value), and improve the temperature coefficient of resonant frequency (τf). 2+ It can also effectively promote the transformation of hexagonal barium feldspar into monoclinic barium feldspar, with the increase of Sr 2+ With the increase of content, the sample density, dielectric constant and quality factor Q×f all increase.

[0027] For example, the grinding media for ball milling the weighed raw materials are zirconia grinding balls and deionized water, and the ball milling time is 16-20 hours; thereby ensuring that the raw materials are fully mixed.

[0028] For example, the step of sequentially calcining, granulating, and dry-pressing the premix to obtain barium feldspar-based microwave dielectric ceramic includes: calcining the premix at high temperature to obtain a pre-calcined material; placing the pre-calcined material in a ball mill for secondary ball milling to obtain a milled material; adding a binder to the milled material and performing spray granulation to obtain a granulated material; placing the granulated material in a mold and preparing a green body by dry pressing; and calcining the green body at high temperature to remove the binder from the green body, thereby obtaining the barium feldspar-based microwave dielectric ceramic.

[0029] In the embodiments of this specification, after obtaining the premix, the premix can be calcined at high temperature to obtain a pre-fired material; then, the pre-fired material is placed in a ball mill for secondary ball milling to obtain a ball-milled material; after the secondary ball milling, a binder is added to the ball-milled material, and spray granulation is performed to obtain a granulated material; ceramic powder itself is discrete and has no self-adhesive ability. After adding a binder (such as polyvinyl alcohol PVA, polyethylene glycol PEG, acrylic resin, etc.), these polymers will form strong "bridges" or "films" between the powder particles after drying, giving the green body sufficient dry compressive strength, so that it does not break or crack during demolding, transfer, and trimming.

[0030] Lubrication and Plasticization: Binder systems typically also include plasticizers (such as glycerin, which makes the binder film more flexible) and lubricants (such as stearic acid or paraffin, which reduce friction between particles and between particles and the mold). This helps to distribute pressure more evenly during dry pressing, reduces internal stress, and prevents delamination of the preform.

[0031] By spray granulating ceramic slurry with added binder, spherical or near-spherical particles with good flowability, uniform particle size distribution, and high bulk density can be produced. The binder-containing slurry is sprayed into the hot air (or inert gas) of a spray drying tower through an atomizer, and the droplets are dried instantly to form individual spherical particles composed of fine ceramic powder and binder inside.

[0032] The granulated material is then placed in a mold and a green blank is prepared by dry pressing. The granulated material can be automatically or manually loaded into the metal mold cavity, thereby pressing the loose granulated powder into a green blank (green blank) with a specific shape, high density, high strength, and uniform microstructure. For example, the method for forming the green blank may include: Pre-pressing: Initial pressure is applied to rearrange the particles and increase the initial density. Main pressing: High pressure (typically tens to hundreds of MPa) is applied. Under this pressure: The granulated particles are crushed, and the original fine powder inside is released. The particles undergo plastic deformation and sliding, filling the voids. A binder forms a strong bond between the particles. Finally, a dense whole with a certain strength is formed. Holding pressure: The pressure is maintained for a short time to relax the internal stress and make the density more uniform. Demolding: The pressure is released, and the green blank is ejected, at which point the green blank is obtained.

[0033] The green body is then subjected to high-temperature calcination to remove the binder, thereby obtaining the barium feldspar-based microwave dielectric ceramic. Exemplarily, the high-temperature calcination of the premix to obtain a pre-fired material includes: calcining the premix at 750-900°C and holding it at that temperature for 3-6 hours to obtain the pre-fired material. The peak temperature for binder removal needs to be higher than the main decomposition temperature of the binder, but much lower than the sintering temperature of the ceramic. The binder removal process is usually carried out in an air atmosphere, which helps the organic matter to be fully oxidized and decomposed into carbon dioxide and water vapor for removal.

[0034] For example, the grinding media used for the secondary ball milling of the pre-calcined material are zirconia grinding balls and deionized water, and the milling time is 20-24 hours. Since the raw material after high-temperature calcination is usually in the form of lumps or coarse particles, the secondary ball milling further refines the particles through the impact, friction, and extrusion of the grinding media, significantly reducing the particle size and increasing the specific surface area. Simultaneously, the ball milling process promotes the mixing of powder and additives (such as dispersants), eliminates concentration gradients, and improves the uniformity of the slurry. Grinding the particles finer significantly increases the specific surface area of ​​the powder. A larger surface area results in higher surface energy, making mass transfer and diffusion easier during subsequent sintering, thereby lowering the sintering temperature, increasing the sintering rate and densification degree, and ultimately improving the product strength.

[0035] For example, the step of subjecting the green blank to high-temperature calcination to remove the binder from the green blank and obtaining the barium feldspar-based microwave dielectric ceramic includes: subjecting the green blank to high-temperature calcination to remove the binder from the green blank; subjecting the green blank to high-temperature sintering, and holding it at a preset temperature for a preset time before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic.

[0036] For example, the adhesive is a mixture of polyvinyl alcohol and polyethylene glycol, and the mass ratio of polyvinyl alcohol to polyethylene glycol is 4:1. The mass of the adhesive is 2-3% of the mass of the ball milling material. By controlling the composition of the adhesive and the mass ratio of the adhesive to the ball milling material, pressure transmission can be more uniform during dry pressing, internal stress can be reduced, and delamination of the blank can be prevented.

[0037] For example, the dry pressing pressure is 200-300 MPa. Under this pressure, the granulated particles are crushed, and the original fine powder inside is released. The particles undergo plastic deformation and sliding, filling the voids. The binder forms a strong bond between the particles. Ultimately, a dense whole with a certain strength is formed.

[0038] For example, the step of performing high-temperature calcination on the green blank to remove the binder from the green blank includes: performing high-temperature calcination on the green blank at 400-800°C to remove the binder from the green blank; the step of performing high-temperature sintering on the green blank and holding it at a preset temperature for a preset time before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic includes: performing high-temperature sintering on the green blank at 1050-1250°C and holding it at 1050-1250°C for 3-6 hours before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic.

[0039] In this embodiment, the green blank is subjected to high-temperature calcination at 400-800℃ to remove the binder from the green blank; then the green blank is sintered at 1050-1250℃ and held at 1050-1250℃ for 3-6 hours before being cooled to room temperature, thereby obtaining a barium feldspar-based microwave dielectric ceramic with low dielectric constant, high quality factor and near-zero resonant frequency temperature coefficient.

[0040] This embodiment allows for setting different ball milling times, calcination temperatures, and sintering temperatures based on the chemical properties of different elements and the physical properties of the ceramic materials. For example, when the content of Li2CO3 and B2O3 in the raw materials increases, the pre-calcination temperature and sintering temperature will decrease due to their relatively low melting points and densities; while when the content of rare earth elements such as Sm2O3 and transition metal oxides (Nb2O5) increases, the corresponding heat treatment temperature will increase.

[0041] This invention also provides a barium feldspar-based microwave dielectric ceramic, which is prepared using the above-described preparation method. Its dielectric constant is 6.5-7.5, its quality factor Q×f>55000, and its resonant frequency temperature coefficient τf<±10ppm / ℃ when the temperature is -30 to 130℃.

[0042] This embodiment employs a traditional solid-state preparation method to obtain microwave dielectric ceramics with a dielectric constant of 6.5-7.5, a quality factor Q×f>55000, and a resonant frequency temperature coefficient τf<±10ppm / ℃ (between -30 and 130℃). It achieves synergistic optimization of low dielectric constant, high quality factor, and near-zero resonant frequency temperature coefficient, resulting in barium feldspar (BaAl2Si2O8, BAS)-based ceramics with excellent microwave dielectric properties.

[0043] The following specific embodiments illustrate the preparation method of the barium feldspar-based microwave dielectric ceramic of the present invention.

[0044] Example 1 This embodiment of the invention provides a method for preparing barium feldspar-based microwave dielectric ceramics, comprising the following steps: 1. Using BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3 and SiO2 as raw materials, according to the chemical formula [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y 1. A premix of 2Si₂O₈, where x=0.4 and y=0.5, is accurately weighed and mixed in a ball mill with zirconia balls and deionized water as grinding media for 16 hours to obtain a premix. 2. The premix is ​​calcined at 900℃ for 6 hours to obtain a pre-calcined material. 3. The pre-calcined material is placed in a ball mill again and ground for 22 hours with zirconia balls and deionized water as grinding media. 4. 2% (by mass) of binder (PVA / PEG=4 / 1wt) is added to the ball milling material obtained from the second ball milling, and the mixture is spray-granulated to obtain granulated material. 5. The granulated material is placed in a mold and formed under a pressure of 280MPa to obtain a green body. 6. After removing the binder from the green body at 600℃, the temperature is further increased to 1250℃ and held for 4 hours. After furnace cooling, BAS-based microwave dielectric ceramic is obtained. The microwave dielectric properties of the BAS-based microwave dielectric ceramic obtained in this embodiment are: dielectric constant ε r = 6.68, quality factor Q×f=64472, temperature coefficient of resonant frequency τf=-8.16 ppm / ℃.

[0045] Example 2 This embodiment of the invention provides a method for preparing barium feldspar-based microwave dielectric ceramics, comprising the following steps: 1. Using BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3 and SiO2 as raw materials, according to the chemical formula [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 )y 1. 2Si₂O₈, where x=0.6, y=0.7, after precise weighing and mixing, is ground and mixed in a ball mill for 20 hours using zirconia balls and deionized water as grinding media to obtain a premix; 2. The premix is ​​calcined at 750℃ for 3 hours to obtain a pre-calcined material; 3. The pre-calcined material is placed in a ball mill again, and ground for 24 hours using zirconia balls and deionized water as grinding media; 4. The material obtained from the second ball mill is mixed with 2.5% by mass of a binder (where PVA / PEG=4 / 1wt), and spray-granulated to obtain a granulated material; 5. The granulated material is placed in a mold and formed under a pressure of 240MPa to obtain a green body; 6. After removing the binder from the green body at 600℃, the temperature is further increased to 1050℃ and held for 3 hours, and then cooled in the furnace to obtain a BAS-based microwave dielectric ceramic; The microwave dielectric properties of the BAS-based microwave dielectric ceramic obtained in this embodiment are: dielectric constant ε r = 7.24, quality factor Q×f=56321, temperature coefficient of resonant frequency τf=-3.82 ppm / ℃.

[0046] Example 3 This embodiment of the invention provides a method for preparing barium feldspar-based microwave dielectric ceramics, comprising the following steps: 1. Using BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3 and SiO2 as raw materials, according to the chemical formula [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y 1. A premix of 2Si₂O₈, where x=0.5 and y=0.6, is accurately weighed and mixed in a ball mill with zirconia balls and deionized water as grinding media for 18 hours to obtain a premix. 2. The premix is ​​calcined at 800℃ for 5 hours to obtain a pre-calcined material. 3. The pre-calcined material is placed in a ball mill again and ground for 20 hours with zirconia balls and deionized water as grinding media. 4. 3% (by mass) of binder (PVA / PEG=4 / 1wt) is added to the material obtained from the second ball milling, and the mixture is spray-granulated to obtain granules. 5. The granules are placed in a mold and formed under a pressure of 300MPa to obtain a green body. 6. After removing the binder from the green body at 600℃, the temperature is further increased to 1150℃ and held for 5 hours. After furnace cooling, BAS-based microwave dielectric ceramic is obtained. The microwave dielectric properties of the BAS-based microwave dielectric ceramic obtained in this embodiment are: dielectric constant εr = 6.75, quality factor Q×f=59568, temperature coefficient of resonant frequency τf=-6.41 ppm / ℃.

[0047] Example 4 This embodiment of the invention provides a method for preparing barium feldspar-based microwave dielectric ceramics, comprising the following steps: 1. Using BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3 and SiO2 as raw materials, according to the chemical formula [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y 1. A premix of 2Si₂O₈, where x=0.4 and y=0.7, is accurately weighed and mixed in a ball mill with zirconia balls and deionized water as grinding media for 20 hours to obtain a premix. 2. The premix is ​​calcined at 750℃ for 4 hours to obtain a pre-calcined material. 3. The pre-calcined material is placed in a ball mill again and ground for 20 hours with zirconia balls and deionized water as grinding media. 4. 2.5% (by mass) of binder (PVA / PEG=4 / 1wt) is added to the material obtained from the second ball milling, and the mixture is spray-granulated to obtain granules. 5. The granules are placed in a mold and formed under a pressure of 280MPa to obtain a green body. 6. After removing the binder from the green body at 600℃, the temperature is further increased to 1180℃ and held for 4 hours. After furnace cooling, BAS-based microwave dielectric ceramic is obtained. The microwave dielectric properties of the BAS-based microwave dielectric ceramic obtained in this embodiment are: dielectric constant ε r = 7.45, quality factor Q×f=55612, temperature coefficient of resonant frequency τf=+1.37 ppm / ℃.

[0048] The properties of the BAS-based microwave dielectric ceramics obtained in the above embodiments are shown in Table 1 below: Table 1

[0049] Table 2 below shows the properties of BAS-based microwave dielectric ceramics obtained in related technologies.

[0050] As can be seen, compared with BAS-based microwave dielectric ceramics in related technologies, the BAS-based microwave dielectric ceramic of this embodiment has a low dielectric constant, a high quality factor, and a near-zero resonant frequency temperature coefficient.

[0051] This invention uses BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3, and SiO2 as raw materials, according to [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y The chemical composition of 2Si₂O₈ was weighed; where x = 0.4-0.6, y = 0.5-0.7; then the weighed raw materials were ball-milled to obtain a premix; the premix was then subjected to calcination, granulation, and dry pressing to obtain barium feldspar-based microwave dielectric ceramics. This invention is based on the combined rule of ionic radius and valence in the Ba₂O₈ composition of barium feldspar. 2+ And Al 3+ The location was simultaneously replaced by multiple other elements, resulting in a chemical composition of [Ba]. 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6Ti 1 / 6 B 1 / 3 ) y Barium feldspar-based microwave dielectric ceramics based on Si₂O₈ were obtained by adjusting the doping amounts of various substitution elements, setting x=0.4-0.6 and y=0.5-0.7. These ceramics exhibited excellent microwave dielectric properties, with a dielectric constant of 6.5-7.5, a quality factor Q×f greater than 55000, and a resonant frequency temperature coefficient τf < ±10ppm / ℃ (between -30 and 130℃). This demonstrated the synergistic optimization of low dielectric constant, high quality factor, and near-zero resonant frequency temperature coefficient in barium feldspar-based microwave dielectric ceramics.

[0052] The above-disclosed embodiments are merely a few preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a barium feldspar-based microwave dielectric ceramic, characterized in that, The method includes the following steps: using BaCO3, CaCO3, SrCO3, La2O3, Sm2O3, Al2O3, Nb2O5, Li2CO3, MgO, TiO2, B2O3, and SiO2 as raw materials, according to [Ba 1-x (Ca 1 / 4 Sr 1 / 4 La 1 / 6 Sm 1 / 6 ) x ][Al 1-y (Nb 1 / 6 Li 1 / 6 Mg 1 / 6 Ti 1 / 6 B 1 / 3 ) y The chemical composition of 2Si2O8 was weighed, where x = 0.4-0.6 and y = 0.5-0.

7. After weighing, the raw materials were ball-milled to obtain a premix. The premix was then subjected to calcination, granulation, and dry pressing to obtain barium feldspar-based microwave dielectric ceramic.

2. The method according to claim 1, characterized in that, The process of sequentially calcining, granulating, and dry-pressing the premixed material to obtain barium feldspar-based microwave dielectric ceramic includes: calcining the premixed material at high temperature to obtain a pre-calcined material; placing the pre-calcined material in a ball mill for secondary ball milling to obtain a milled material; adding a binder to the milled material and performing spray granulation to obtain a granulated material; placing the granulated material in a mold and preparing a green body by dry pressing; and calcining the green body at high temperature to remove the binder from the green body, thereby obtaining the barium feldspar-based microwave dielectric ceramic.

3. The method according to claim 2, characterized in that, The step of subjecting the green blank to high-temperature calcination to remove the binder from the green blank and obtaining the barium feldspar-based microwave dielectric ceramic includes: subjecting the green blank to high-temperature calcination to remove the binder from the green blank; subjecting the green blank to high-temperature sintering, and holding it at a preset temperature for a preset time before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic.

4. The method according to claim 1, characterized in that, The grinding media for ball milling the weighed raw materials are zirconium oxide grinding balls and deionized water, and the ball milling time is 16-20 hours.

5. The method according to claim 2, characterized in that, The step of calcining the premixed material at high temperature to obtain a pre-calcined material includes: calcining the premixed material at 750-900℃ and holding it at that temperature for 3-6 hours to obtain the pre-calcined material.

6. The method according to claim 2, characterized in that, The grinding media for the secondary ball milling of the pre-burned material are zirconium oxide grinding balls and deionized water, and the ball milling time is 20-24 hours.

7. The method according to claim 2, characterized in that, The adhesive is a mixture of polyvinyl alcohol and polyethylene glycol, and the mass ratio of polyvinyl alcohol to polyethylene glycol is 4:

1. The mass of the adhesive is 2-3% of the mass of the ball milling material.

8. The method according to claim 2, characterized in that, The pressure for dry pressing is 200-300 MPa.

9. The method according to claim 3, characterized in that, The step of subjecting the green blank to high-temperature calcination to remove the binder from the green blank includes: subjecting the green blank to high-temperature calcination at 400-800°C to remove the binder from the green blank; the step of subjecting the green blank to high-temperature sintering and holding it at a preset temperature for a preset time before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic includes: subjecting the green blank to high-temperature sintering at 1050-1250°C and holding it at 1050-1250°C for 3-6 hours before cooling it to room temperature to obtain the barium feldspar-based microwave dielectric ceramic.

10. A barium feldspar-based microwave dielectric ceramic, characterized in that, The microwave dielectric ceramic is prepared by the preparation method according to any one of claims 1-9.

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