阅读说明：本技术 谐振频率温度系数可调的低介电常数微波介质陶瓷及其制备方法 (Low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient and preparation method thereof ) 是由 苏聪学 方亮 敖来远 韦启航 于 2020-10-31 设计创作，主要内容包括：本发明公开了一种谐振频率温度系数可调的低介电常数微波介质陶瓷及其制备方法。该微波介质陶瓷的化学组成是Ca_4ZrGe_(3-x)Ti_xO_(12),其中0≤x≤0.75。本发明采用传统的固相反应烧结法,制备方法简单。本发明制备得到的谐振频率温度系数可调的低介电常数微波介质陶瓷在不需要额外添加CaTiO_3的情况下,可通过原位复合形成的CaTiO_3来有效优化陶瓷的谐振频率温度系数。利用Ti~(4+)取代Ge~(4+),不仅可以改善谐振频率温度系数,而且能够减少昂贵的原材料GeO_2,工艺简单,有利于工业规模化生产。1370℃烧结6小时的Ca_4ZrGe_(2.5)Ti_(0.5)O_(12)陶瓷具有优异的微波介电性能为：ε_r＝11.95,Q×f＝45060GHz,τ_f＝+0.4ppm/℃。(The invention discloses a low-dielectric constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient and a preparation method thereof. The chemical composition of the microwave dielectric ceramic is Ca 4 ZrGe 3‑x Ti x O 12 Wherein x is more than or equal to 0 and less than or equal to 0.75. The invention adopts the traditional solid-phase reaction sintering method, and the preparation method is simple. The low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient prepared by the invention does not need to be additionally added with CaTiO 3 In the case of (3), CaTiO formed by in situ compounding 3 To effectively optimize the temperature coefficient of the resonant frequency of the ceramic. By using Ti 4+ Substituted Ge 4+ Not only can improve the temperature coefficient of the resonance frequency, but also can reduce the expensive raw material GeO 2 The method has simple process and is beneficial to industrial large-scale production. Ca sintered at 1370 ℃ for 6 hours 4 ZrGe 2.5 Ti 0.5 O 12 The ceramic has excellent microwave dielectric properties as follows: epsilon r ＝11.95，Q×f＝45060GHz，τ f ＝+0.4ppm/℃。)

1. Dielectric constant epsilon_r9.89 to 16.37, the quality factor Qf is 24900 to 77980GHz, the temperature coefficient of the resonance frequency is within-47.7 ppm/DEG C to +95 ppm/DEG C, the positive and negative of the temperature coefficient of the resonance frequency can be adjusted, and the low dielectric constant microwave dielectric ceramic is characterized in that the chemical composition of the low dielectric constant microwave dielectric ceramic with the adjustable temperature coefficient of the resonance frequency is Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75.

2. A method for preparing the low dielectric constant microwave dielectric ceramic with adjustable temperature coefficient of resonance frequency according to claim 1, which comprises the following steps:

(1) with CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Weighing the ingredients according to the stoichiometric ratio of x being more than or equal to 0 and less than or equal to 0.75;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1350-1390 ℃ for sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low dielectric constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

3. The method for preparing low dielectric constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient as claimed in claim 2, wherein the purity of the raw material in the step (1) is not less than 99.9%.

4. The method for preparing a low dielectric constant microwave dielectric ceramic with an adjustable temperature coefficient of resonant frequency according to claim 2, wherein the rotation speed of the ball mill is 300 rpm.

5. The method for preparing a low-dielectric-constant microwave dielectric ceramic with an adjustable temperature coefficient of resonance frequency according to claim 2, wherein the mass concentration of the polyvinyl alcohol solution is 5%.

Technical Field

The invention belongs to the technical field of electronic ceramics and preparation thereof, and particularly relates to a low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient and a preparation method thereof.

Background

Modern mobile communication deviceThe rapid development of the communication has promoted the rapid development of various microwave mobile communication terminal devices toward miniaturization, light weight, multi-functionalization and low cost. With the deep application of 5G technology, the microwave communication technology extends to the millimeter wave band, and the microwave dielectric ceramic material is required in the millimeter wave band of very high frequency: 1. has a low dielectric constant to increase the transmission rate of the electrical signal; 2. the selectivity of the working frequency of the device is improved by extremely low dielectric loss, and the energy conversion consumption of the device can be reduced; 3. temperature coefficient of resonant frequency (| τ) near zero_fLess than or equal to 10 ppm/DEG C) to ensure the working stability of signals during resonance and transmission.

The resonant frequency temperature coefficients of most of the low-dielectric high-quality factor microwave dielectric ceramics reported at present are large in the negative direction, and are not favorable for the thermal stability of device operation. For example, garnet microwave dielectric ceramics, which have gained much attention in recent years, generally have a high quality factor: vanadium-based garnet LiCa₃MgV₃O₁₂Up to 74700GHz, aluminum-based garnet Y₃MgAl₃SiO₁₂Has a quality factor of 16739 to 57337GHz, and is a lithium-based garnet Li₃Nd₃W₂O₁₂The quality factor of (2) is 36800GHz, but the temperature coefficient of the resonant frequency of the above garnet microwave dielectric ceramic material is large in the negative direction. Germanium-based garnet microwave dielectric ceramics have also received high attention from researchers since 2020, such as Ca₃Y₂Ge₃O₁₂(Journal of the European Ceramic Society,2020,40:3989～3995.)、Ca₄ZrGe₃O₁₂Germanium-based garnets such as (Materials Letters,2020,275:128149.) have difficulty in satisfying a near-zero resonant frequency temperature coefficient (| τ) despite their slightly lower resonant frequency temperature coefficients, both less than-45 ppm/DEG C, than those of the aforementioned vanadium-based garnets_fLess than or equal to 10 ppm/DEG C). However, these microwave dielectric ceramics all have a high quality factor in which rare earth germanium-based garnet Ca, which is expensive compared to the raw material, is present₃Y₂Ge₃O₁₂Cheaper Ca₄ZrGe₃O₁₂Garnet microwaveThe quality factor of the dielectric ceramic is as high as 76900GHz, but the temperature coefficient of the resonant frequency is also larger, reaching-41.3 ppm/DEG C. In the germanium-based garnet microwave dielectric Ceramic, Tang et al (Journal of the European Ceramic Society,2020,40: 3989-3995, CN202010358668.9) used Ca₃Ln₂Ge₃O₁₂Substituting Ca with Mg at A site of (Ln ═ Y and Yb) to obtain solid solution ceramic with adjustable temperature coefficient of resonance frequency, and adding Mg at Ca site to obtain ceramic_0.5Mg_2.5Ln₂Ge₃O₁₂Obtaining near zero τ on component ceramics_fHowever, the quality factor is suddenly decreased to less than 25000GHz, and the dielectric properties are seriously deteriorated. Ge-based garnet microwave dielectric ceramic Ca with high quality factor and relatively low price₄ZrGe₃O₁₂On the other hand, how to obtain the near-zero resonant frequency temperature coefficient on the premise of lower process cost and simultaneously keep higher quality factor (Qf is more than or equal to 40000GHz) is a problem which is difficult to solve, and the problem is the common problem of the microwave dielectric ceramic with low dielectric, high quality factor and larger negative resonant frequency temperature coefficient.

Generally, the main method for solving the temperature coefficient of resonant frequency with larger negative value of material is to add the material with larger positive value of resonant frequency temperature coefficient (such as CaTiO)₃Or TiO₂Etc.) to perform two-phase compounding of the material, thereby adjusting the temperature coefficient of the resonant frequency of the material system to be close to zero. However, this method generally requires a relatively complicated process: mixing the host material of pure phase with CaTiO₃Weighing according to a certain proportion, ball milling, presintering, secondary ball milling, granulating, sieving and column pressing sintering. Before that, the host material (or CaTiO) was in a pure phase₃) And the raw materials also need to be subjected to ball milling, presintering, secondary ball milling, granulation screening and compression column sintering according to a certain proportion. Finally obtained temperature-stable, tau_fComposite ceramics with values close to zero take a lot of process time and energy consumption for production.

Disclosure of Invention

In order to solve the problems, the invention aims to provide a low-dielectric-constant microwave dielectric ceramic with adjustable temperature coefficient of resonant frequency and a preparation method thereof. Harmonic of the inventionThe low-dielectric constant microwave dielectric ceramic with adjustable temperature coefficient of vibration frequency has high quality factor, and the temperature coefficient of resonance frequency is adjustable in a positive and negative range (-47.7 ppm/DEG C to +95 ppm/DEG C). In addition, the method for preparing the ceramic is simple and low in cost, and the CaTiO formed by in-situ compounding₃Can be made into ceramic_fThe value is adjusted to near zero and still maintain a high figure of merit.

In order to overcome the defects of the prior art, the technical scheme of the invention is as follows:

dielectric constant epsilon_r9.89 to 16.37, the quality factor Qf is 24900 to 77980GHz, the temperature coefficient of the resonance frequency is within-47.7 ppm/DEG C to +95 ppm/DEG C, the positive and negative of the temperature coefficient of the resonance frequency can be adjusted, and the low dielectric constant microwave dielectric ceramic is characterized in that the chemical composition of the low dielectric constant microwave dielectric ceramic with the adjustable temperature coefficient of the resonance frequency is Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75.

The preparation method of the low dielectric constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient comprises the following steps:

(1) with CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.0.75;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1350-1390 ℃ for sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low dielectric constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

Preferably, the purity of the raw material in the step (1) is more than or equal to 99.9 percent.

Preferably, the rotation speed of the ball mill is 300 r/min.

Preferably, the polyvinyl alcohol solution has a mass concentration of 5%.

Compared with the prior art, the invention has the advantages that: the material provided by the invention has low dielectric constant (9.89-16.37), can improve the transmission rate of electric signals, has high quality factor (24900-77980 GHz), can improve the selectivity of the working frequency of a device, and can adjust tau within a positive and negative resonant frequency temperature coefficient range_fThe thermal stability of the device can be ensured. The optimization process of the resonant frequency temperature coefficient of the ceramic is divided into two parts, namely, in Ti⁴⁺Substituted Ge⁴⁺In the process of (3), substitution within the solid solubility can optimize tau_fValue, after exceeding solid solubility, in-situ recombination forms second phase CaTiO₃And further to optimize tau substantially_fThe value is obtained. The whole optimization process is carried out in the primary ceramic preparation process, and the expensive raw material GeO is reduced₂The method has simple process and is beneficial to industrial large-scale production.

Drawings

FIG. 1 shows Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75 XRD pattern of ceramic at optimum sintering temperature.

FIG. 2 shows Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75, and the ceramic is subjected to scanning electron microscopy at 1370 ℃.

FIG. 3 shows Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75, and the microwave dielectric property diagrams of the ceramics at different sintering temperatures.

Detailed Description

The invention is further described in detail below with reference to the figures and examples.

Ca of the invention₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75, the preparation method of the microwave dielectric ceramic material comprises the following steps:

(1) with CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.0.75;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1350-1390 ℃ for sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low dielectric constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

Example 1:

(1) with CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1350 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 2:

(1) with CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder, wrapping the powder and covering the cylinder, placing the crucible into a high-temperature furnace, heating to 1380 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, the rotation speed of ball milling is 300 r/min, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 3

(1) With CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0.125 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1360 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 4

(1) With CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0.25 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1360 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 5

(1) With CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0.375 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1370 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 6

(1) With CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0.5 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1370 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 7

(1) With CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0.625 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder, wrapping the powder and covering the cylinder, placing the crucible into a high-temperature furnace, heating to 1380 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 8

(1) With CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0.75 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder, wrapping the powder and covering the cylinder, placing the crucible into a high-temperature furnace, heating to 1380 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Example 9

(1) With CaCO₃、ZrO₂、GeO₂And TiO₂As a raw material, in accordance with Ca₄ZrGe_3-xTi_xO₁₂Wherein x is 0.75 in stoichiometric ratio;

(2) placing the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol which are weighed and prepared in the step (1) into a ball milling tank according to the mass ratio of 1:3:3, and then placing the ball milling tank into a planetary ball mill for ball milling for 8 hours; drying the slurry raw material after ball milling to obtain raw material mixture powder;

(3) pre-burning the mixture powder obtained by drying in the step (2) at 1200 ℃ for 4 hours to make a raw material mixture sample preliminarily react to obtain a pre-burnt material;

(4) grinding the pre-sintered material obtained through the preliminary reaction in the step (3) into powder, putting the powder, zirconium dioxide ball milling beads and absolute ethyl alcohol into a ball milling tank according to the mass ratio of 1:3:3, carrying out ball milling for 2 hours to obtain viscous slurry in the ball milling tank, adding a polyvinyl alcohol solution accounting for 1.5% of the mass of the pre-sintered material in the step (3) into the slurry in the ball milling tank, starting the ball milling machine again for ball milling for 6 hours, and drying to obtain dried powder;

(5) drying and sieving the powder obtained by drying in the step (4) to obtain powder with uniformly dispersed particles and refined particle size, wherein the powder is divided into two parts for later use;

(6) putting a part of the powder obtained in the step (5) into a die, and pressing the powder into a cylinder under the pressure of 200 MPa;

(7) and (3) placing the cylinder formed by pressing in the step (6) into a crucible, pouring the other part of the powder in the step (5) into the crucible as the buried burning powder to wrap the powder and cover the cylinder, placing the crucible into a high-temperature furnace, heating to 1390 ℃, sintering for 6 hours, cooling along with the furnace, and taking out a sample from the crucible to obtain the low-dielectric-constant microwave dielectric ceramic with adjustable resonant frequency temperature coefficient.

In the specific embodiment, the purity of the raw materials is more than or equal to 99.9 percent, in the specific embodiment, the rotation speed of the ball mill is 300 r/m, and the mass concentration of the polyvinyl alcohol solution is 5 percent.

Table 1 shows the microwave dielectric properties of each of the examples.

TABLE 1

FIG. 1 shows Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75, and the ceramic has an XRD pattern at the optimal sintering temperature. As can be seen from the figure, Ca is present when x is 0. ltoreq. x.ltoreq.0.375₄ZrGe_3-xTi_xO₁₂The ceramics are all pure cubic garnet phases which are matched with PDF card 01-081-2356, no impurity phase exists, and a single-phase material can be obtained. When x is more than or equal to 0.5 and less than or equal to 0.75, Ca₄ZrGe_3-xTi_xO₁₂CaTiO ceramic₃Second phase, but only garnet Ca in the entire material₄ZrGe₃O₁₂Phase of CaTiO₃And (4) phase(s). CaTiO formed by in situ compounding₃Gradually becomes apparent on the diffraction peak as the value of x increases.

FIG. 2 shows Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75, and the ceramic is subjected to scanning electron microscopy at 1370 ℃. As can be seen from the figure, Ca₄ZrGe_2.875Ti_0.125O₁₂、Ca₄ZrGe_2.75Ti_0.25O₁₂And Ca₄ZrGe_2.625Ti_0.375O₁₂The ceramics have compact and compact microstructures, but the first two have a plurality of larger grains, and Ca₄ZrGe_2.625Ti_0.375O₁₂The ceramic grains of (a) are relatively small and the size distribution is relatively uniform. To more visually observe the second phase of CaTiO₃We used low power to observe x-0.5-0.75 ceramic backScattered electron microscopic morphology. It can be seen that the ceramic sample with x equal to 0.5 has more and larger grains, CaTiO, as a whole₃The number of grains (dark color in the figure) is relatively small. The ceramic sample with x 0.625 generally has smaller garnet phase grains relative to the main phase grains of the ceramic sample with x 0.5. The ceramic sample with x equal to 0.75 has more CaTiO in a local range₃Crystal grains and relative looseness among the crystal grains.

FIG. 3 shows Ca₄ZrGe_3-xTi_xO₁₂Wherein x is more than or equal to 0 and less than or equal to 0.75, and the microwave dielectric property diagrams of the ceramics at different sintering temperatures. (a) In the figure, with Ti⁴⁺Increase in the amount of substitution, Ca₄ZrGe_3-xTi_xO₁₂The sintering temperature and dielectric constant of the ceramic show a tendency to rise. (b) In the figure, Ca₄ZrGe_3-xTi_xO₁₂Quality factor of ceramics with Ti⁴⁺The substitution amount increases and the tendency to decrease is exhibited. (c) In the figure, Ca₄ZrGe_3-xTi_xO₁₂Tau of ceramics_fThe value change can be divided into two phases. When x is more than or equal to 0 and less than or equal to 0.375, tau_fThe value of the X gradually decreases, and Ca gradually increases to 0.375₄ZrGe_3-xTi_xO₁₂Tau of ceramics_fThe value can be reduced from about-45 ppm/DEG C to about-26 ppm/DEG C. In the second stage, when x is more than or equal to 0.5 and less than or equal to 0.75, tau_fThe value clearly shifts in the positive direction, in particular when x is 0.5, Ca₄ZrGe_2.5Ti_0.5O₁₂The ceramic has a near-zero temperature coefficient of resonant frequency at each sintering temperature. The microwave dielectric property shows that the second phase CaTiO formed by in-situ compounding₃Can remarkably reduce tau_fThe value is adjusted to a positive value direction, and tau close to zero is obtained when x is 0.5_fValues while maintaining a figure of merit greater than 40000GHz also reduce expensive raw material costs and production costs. Ca sintered at 1370 ℃ for 6 hours₄ZrGe_2.5Ti_0.5O₁₂The ceramic has excellent microwave dielectric properties as follows: epsilon_r＝11.95，Q×f＝45060GHz，τ_f＝+0.4ppm/℃。

While the invention has been described in further detail with reference to specific preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.