CN111423227B

CN111423227B - Microwave dielectric ceramic material with medium dielectric constant and high Qf and preparation method thereof

Info

Publication number: CN111423227B
Application number: CN202010244756.6A
Authority: CN
Inventors: 张军志; 杨和成; 谭焕辉
Original assignee: XIAMEN SONGYUAN ELECTRONICS CO Ltd
Current assignee: XIAMEN SONGYUAN ELECTRONICS CO Ltd
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2022-04-01
Anticipated expiration: 2040-03-31
Also published as: CN111423227A

Abstract

The invention provides a microwave dielectric ceramic material with a medium dielectric constant and a high Qf and a preparation method thereof, relating to the technical field of ceramic materials. The ceramic material comprises a main crystal phase material with the mass fraction of 98.5-99.5 and a modified additive with the mass fraction of 0.5-1.5%, wherein the main crystal phase material is xSr_1‑aMg_aTiO₃‑yLaAlO₃Wherein a is 0 to 0.2, and x/y is 2 to 3. The material adopts xSr synthesized by Mg pre-doping and solid phase method_1‑aMg_aTiO₃‑yLaAlO₃As the main crystal phase component, and adding a certain proportion of modifying additive. Can be made into porcelain under the condition of 1620-1680 ℃, and can obtain good microwave characteristics, the room-temperature dielectric constant is between 39-42, the Qf value is not less than 80000, and the temperature coefficient tau_f(-40-85 ℃): +/-10 ppm/deg.C, excellent performance.

Description

Microwave dielectric ceramic material with medium dielectric constant and high Qf and preparation method thereof

Technical Field

The invention relates to the field of ceramic materials, in particular to a microwave dielectric ceramic material with a medium dielectric constant and a high Qf and a preparation method thereof.

Background

The microwave dielectric ceramic material is a novel functional ceramic material which is rapidly developed in recent years and has low microwave loss, high dielectric constant and dielectric constant temperature coefficient tau_fStable and the like. The dielectric material is used as a dielectric material in a microwave frequency band circuit, is a core basic material of a novel microwave circuit and a device including a dielectric resonator, a filter, an oscillator, a duplexer, an antenna, a dielectric substrate and the like, and is widely applied to modern microwave communication and satellite navigation systems and equipment.

The dielectric resonator has resonance property when working in narrow frequency band, is an electromagnetic element, generally consists of ceramic cylinders with higher dielectric constant and low loss, and has the advantages of small size, low loss, stable device and the like compared with the traditional metal waveguide resonator. The existing medium ceramic material with medium dielectric constant is mainly made of CaTiO₃-NdAlO₃The system is primary, one side is Nd₂O₃The raw materials are expensive, which limits the application. On the other hand, the dielectric constant is 43 to 48, and it is difficult to apply the dielectric constant to the case of the medium dielectric constant of 39 to 42. In addition, the quality factor Qf of the existing medium-dielectric-constant dielectric ceramic material can only reach about 40000GHz usually, and the requirement is difficult to meet.

Disclosure of Invention

The invention aims to provide a microwave dielectric ceramic material with a medium dielectric constant and a high Qf, which has low dielectric loss, excellent microwave performance, and can obtain required dielectric parameters and a temperature coefficient close to zero.

The invention also aims to provide a preparation method of the microwave dielectric ceramic material with the medium dielectric constant and high Qf, which is simple, easy to operate and suitable for industrial large-scale production.

The technical problem to be solved by the invention is realized by adopting the following technical scheme.

The invention provides a microwave dielectric ceramic material with medium dielectric constant and high Qf, which comprises a main crystal phase material with the mass fraction of 98.5-99.5 and a modified additive with the mass fraction of 0.5-1.5%, wherein the main crystal phase material comprises xSr_1- _aMg_aTiO₃-yLaAlO₃Wherein a is 0 to 0.2, and x/y is 2 to 3.

The invention also provides a preparation method of the microwave dielectric ceramic material, which comprises the following steps:

s1, according to xSr_1-aMg_aTiO₃-yLaAlO₃Mixing a Mg-containing compound, a Sr-containing compound, a La-containing compound, an Al-containing compound and a Ti-containing compound according to the molar ratio of the elements, adding water, performing ball milling, drying, and calcining in an air atmosphere to obtain the main crystal phase material;

s2, mixing the main crystal phase material and the modified additive according to the mass ratio of 98.5-99.5: 0.5-1.5, adding water, performing ball milling, and drying to obtain the microwave dielectric ceramic powder.

The microwave dielectric ceramic material with medium dielectric constant and high Qf and the preparation method thereof have the advantages that:

xSr_1-aMg_aTiO₃-yLaAlO₃has the advantages of low dielectric loss, adjustable dielectric constant, good microwave performance and the like. LaAlO₃Has higher negative temperature coefficient, SrTiO₃Has positive temperature coefficient and higher dielectric constant, and the two opposite resonance frequenciesThe materials with the temperature coefficient of coefficient are combined together, and the materials form a solid solution, so that the temperature coefficient close to zero can be obtained, and the required dielectric constant can be obtained at the same time. Meanwhile, the Mg pair is previously doped to obtain the main crystal phase material xSr_1- _aMg_aTiO₃-yLaAlO₃Mg pre-doping changes the microstructure of the main crystal phase material, and the dielectric constant is 39-42, the Qf value is higher than 80000, and the temperature coefficient tau is obtained by selecting subsequent modification additives_f(-40-85 ℃): product at + -10 ppm/deg.C. The solid phase synthesis mechanism of partial pre-doping and directional post-doping modes is successfully applied, and the prepared material has good uniformity and meets the requirements of microwave devices.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The microwave dielectric ceramic material with high Qf and medium dielectric constant and the preparation method thereof according to the embodiments of the present invention will be described in detail.

The microwave dielectric ceramic material with the medium dielectric constant and the high Qf is characterized by comprising a main crystal phase material with the mass fraction of 98.5-99.5 and a modified additive with the mass fraction of 0.5-1.5%, wherein the main crystal phase material comprises xSr_1-aMg_aTiO₃-yLaAlO₃Wherein a is 0 to 0.2, and x/y is 2 to 3.

In a preferred embodiment, the modifying additive is selected from SnO₂、MnCO₃、MnO₂、CaCO₃、Y₂O₃、MoO₃And ZrO₂One or more of (a).

Under the mixture ratio of the main crystal phase material and the additive, the microwave dielectric ceramic material can be effectively modified, the room-temperature dielectric constant of the obtained microwave dielectric ceramic material is 39-42, and the quality factor Qf value is larger than or equal to 80000 GHz.

More preferably xSr_1-aMg_aTiO₃-yLaAlO₃Wherein a is 0.05 to 0.16, and x/y is 2.1 to 2.4. The pre-doping amount of Mg is strictly controlled, so that the performance of the microwave dielectric ceramic material can be further optimized. The material obtained under the condition has the dielectric constant of 39.6-40.2, and meets the special requirements of microwave devices.

Further, in a preferred embodiment, the mass fractions of the components in the microwave dielectric ceramic material in the modified additives are as follows: SnO₂ 0～0.5％、MnCO₃0～0.6％、MnO₂ 0～0.4％、CaCO₃0～1％、Y₂O₃ 0～0.2％、MoO₃ 0～0.1％，ZrO₂0～0.3％。

Further, in a preferred embodiment, in SnO₂、MnCO₃、MnO₂、CaCO₃、Y₂O₃、MoO₃And ZrO₂2-5 components are selected and added, and the mass fraction of each component is controlled in the following range: SnO₂ 0.1～0.5％、MnCO₃ 0.1～0.6％、MnO₂ 0.2～0.4％、CaCO₃ 0.1～1％、Y₂O₃ 0.1～0.2％、MoO₃ 0.1％，ZrO₂ 0.1～0.3％。

The properties of the microwave dielectric ceramic material can be further improved by optimizing the selection and the proportion of the modified additives, for example, the Qf value of the microwave dielectric material is further improved.

s1, according to xSr_1-aMg_aTiO₃-yLaAlO₃Mixing a Mg-containing compound, a Sr-containing compound, a La-containing compound, an Al-containing compound and a Ti-containing compound according to the molar ratio of the elements, adding water, performing ball milling, drying, and calcining in an air atmosphere to obtain the main crystal phase material.

In a preferred embodiment, the Mg-containing compound is selected from high-purity superfine magnesium hydroxide. The magnesium hydroxide is pre-doped in the solid-phase synthesis process, is easy to decompose, well changes the microstructure of the material, and greatly improves the microwave performance of the material. Further, the Sr-containing compound is strontium carbonate, the La-containing compound is lanthanum oxide, the Al-containing compound is aluminum oxide, and the Ti-containing compound is titanium dioxide. Controlling the purity of each material to be more than 99.6 percent and controlling Mg (OH)₂The content of S in the catalyst is controlled below 600ppm, so that the formation of cavities in the calcining process is avoided, and the generation of impurity phases is reduced.

In a preferred embodiment, in the step, the calcination temperature is 1200-1270 ℃, and the calcination time is 2-4 h. More preferably, the calcination temperature is 1230 to 1250 ℃ and the calcination time is 3 hours. The calcination is carried out at a relatively low temperature, so that the generation of impurities and the increase of voids caused by high temperature can be avoided.

Further, in the step, after the components are mixed, water is added according to the mass ratio of the mixture to the water of 1: 01-2 for wet ball milling.

In the step, after a main crystal phase material and a modified additive are mixed, water is added according to the mass ratio of the material to the water of 1: 0.5-1 for wet ball milling.

Further, in a preferred embodiment, after the microwave dielectric ceramic powder is obtained, the method further includes the following steps:

and S3, adding an auxiliary agent into the microwave dielectric ceramic powder, and performing ball milling to obtain slurry, wherein the auxiliary agent comprises an adhesive, a plasticizer and a dispersing agent. The binder may be, for example, polyvinyl alcohol, the plasticizer may be, for example, polyethylene glycol, and the dispersant may be, for example, ammonium carboxylate.

S4, drying the slurry to obtain spherical particles, and pressing the spherical particles into a green body.

And S5, removing the glue from the green body, sintering and annealing to obtain the product.

Further, in the step, the rubber discharging conditions are as follows: and (3) preserving the heat for 24h at the temperature of 500-650 ℃, removing organic matters in the green body, and requiring the temperature rise speed to be less than 10 ℃/h in the whole glue removing process.

Further, in this step, the sintering conditions are: in the air atmosphere, the temperature is raised to 1620-1680 ℃ at the temperature rise rate of 150-200 ℃/h, and the temperature is kept for 3-5 h.

Further, in this step, the conditions of the annealing treatment are: and (3) preserving the heat of the sintered product for 2-3 h at the temperature of 950-1050 ℃. After high-temperature sintering, an annealing section is added within the range of 950-1050 ℃, so that the internal stress of the material can be effectively eliminated, and the Qf value is improved.

The features and properties of the present invention are described in further detail below with reference to examples.

Examples

The microwave dielectric ceramic material with the medium dielectric constant and the high Qf provided by the embodiment is prepared by the following steps:

(1) according to xSr_1-aMg_aTiO₃-yLaAlO₃The stoichiometric ratio of (a). Mixing high-purity and superfine magnesium hydroxide, strontium carbonate, lanthanum oxide, aluminum oxide and titanium dioxide according to the proportion shown in the following table 1, placing the mixture and deionized water in a mass ratio of 1:1.5, and performing wet ball milling in a ball mill. Mixing, spray drying, calcining at 1220 deg.C or 1250 deg.C for 3 hr in air furnace to obtain xSr_1-aMg_aTiO₃-yLaAlO₃A main crystal phase.

TABLE 1 main crystal phase material proportioning table

(2) The compositions in accordance with Table 2 below were proportioned at xSr_1-aMg_aTiO₃-yLaAlO₃Adding a modifying additive into the main crystal phase material, and adding deionized water according to the mass ratio of the material to the deionized water of 1:0.8 for wet ball milling. Ball-milling to make the powder flatThe average particle size reaches 200-300 nm.

TABLE 2 proportioning table of dielectric ceramic material

(3) And (3) adding a proper amount of adhesive, plasticizer and dispersant into the powder obtained in the step (2), and carrying out ball milling for 1.5h in a ball milling tank by using zirconia balls as ball milling media to obtain slurry. The slurry was subjected to centrifugal spray drying to obtain spherical particles having good fluidity.

(4) Pressing and molding the spherical particles obtained in the step (3) to obtain the spherical particles with the density of 3.25g/cm³Cylindrical green sheets with dimensions of 15 x 10 mm.

(5) And (3) placing the green sheet at 600 ℃, preserving heat for 24h, removing organic matters in the green sheet, and requiring the temperature rise speed in the whole glue removing process to be less than 10 ℃/h.

(6) And sintering the green body after the binder removal in air. The sintering condition is that the temperature is raised to 1620-1680 ℃ at the temperature rise speed of 150-200 ℃/h, and the heat preservation time is 3-5 h. A plurality of samples were obtained according to the sintering conditions in table 3.

(7) And (4) keeping the temperature of the high-temperature sintering product obtained in the step (6) at 1000 ℃ for 2.5h for annealing treatment.

Test examples

For the samples obtained in the examples, an agilent network analyzer was used to perform microwave performance tests at a frequency of 5-7 GHz. The test results are shown in table 3.

Table 3 table of performance test results

As shown in Table 3, the microwave dielectric ceramic material obtained by the preparation method can be preparedSintering at 1620-1680 deg.c to form the microwave dielectric ceramic device. The room temperature dielectric constant is between 39 and 42 and the temperature coefficient tau can be formed by adjusting the compounding ratio of the materials_f(-40-85 ℃): the ceramic material of the continuous adjustable system meets the application requirement of the microwave device greatly and widens the application field and application scene, wherein the concentration of the ceramic material is +/-10 ppm/DEG C, and the Qf value is more than or equal to 80000 GHz.

The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims

1. The microwave dielectric ceramic material with medium dielectric constant and high Qf is characterized by comprising 98.5-99.5 mass percent of main crystal phase material and 0.5-1.5 mass percent of modified additive, wherein the main crystal phase material is xSr_1- _aMg_aTiO₃-yLaAlO₃Wherein a is 0.05-0.16, and x/y is 2.1-2.4;

the modifying additive is selected from SnO₂、MnCO₃、MnO₂、CaCO₃、Y₂O₃、MoO₃And ZrO₂One or more of;

in the modified additive, the mass fractions of the components in the microwave dielectric ceramic material are as follows: SnO₂0～0.5％、MnCO₃ 0～0.6％、MnO₂0～0.4％、CaCO₃ 0～1％、Y₂O₃ 0～0.2％、MoO₃ 0～0.1％，ZrO₂ 0～0.3％；

The room temperature dielectric constant of the microwave dielectric ceramic material is 39-42, and the quality factor Qf value is larger than or equal to 80000 GHz.

2. A method for preparing a microwave dielectric ceramic material as claimed in claim 1, comprising the steps of:

s2, mixing the main crystal phase material and the modified additive according to the mass ratio of 98.5-99.5: 0.5-1.5, adding water, performing ball milling, and drying to obtain microwave dielectric ceramic powder;

s3, adding an auxiliary agent into the microwave dielectric ceramic powder, and performing ball milling to obtain slurry, wherein the auxiliary agent comprises an adhesive, a plasticizer and a dispersing agent;

s4, drying the slurry to obtain spherical particles, and pressing the spherical particles into a green body;

s5, performing binder removal, sintering and annealing treatment on the green body to obtain a product;

in the step S1, the calcining temperature is 1200-1270 ℃, and the calcining time is 2-4 h;

in step S5, the conditions of the annealing treatment are: and (3) preserving the heat of the sintered product for 2-3 h at the temperature of 950-1050 ℃.

3. A method for preparing a microwave dielectric ceramic material as claimed in claim 2, wherein in step S5, the sintering conditions are as follows: in the air atmosphere, the temperature is raised to 1620-1680 ℃ at the temperature rise rate of 150-200 ℃/h, and the temperature is kept for 3-5 h.