CN108911746B

CN108911746B - Low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material and preparation method and application thereof

Info

Publication number: CN108911746B
Application number: CN201810896856.XA
Authority: CN
Inventors: 汪宏; 袁晓峰
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2018-08-08
Filing date: 2018-08-08
Publication date: 2020-10-27
Anticipated expiration: 2038-08-08
Also published as: CN108911746A

Abstract

The invention discloses an ultra-low temperatureA sintered microwave dielectric ceramic material system and a preparation method and application thereof. The structural expression formula of the system is Na₂W_xO_3x+1(x is 1,2, 4). The system can be sintered at very low temperatures (565-. The powder preparation adopts an improved solid phase method, and the presintering temperature is 400-550 ℃. The material system can be co-fired with Ag or Al electrodes, can be used for preparing low temperature co-fired ceramic (LTCC) substrates, and is applied to microwave resonators, filters, panel antennas and the like. The invention meets the requirement of environmental protection, and has no toxicity and pollution.

Description

Low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of electronic ceramic material preparation, and particularly relates to a low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material, and a preparation method and application thereof.

Background

With the continuous development of modern communication technology, the industry has made higher and higher demands on the miniaturization, portability, multifunction, high reliability, low cost, wearability and the like of electronic products. LTCC, a very important technology in electronic communications, is mainly used in the technology of high integration and high performance electronic packaging, and has great potential in design flexibility, wiring density and reliability.

Most of the traditional electronic ceramics can not meet the requirements of LTCC technology on materials because the sintering temperature of the ceramics is still too high to realize co-sintering with electrodes with lower melting points. Meanwhile, most of the existing ceramic materials have poor stability, the placing performance in the air is seriously deteriorated, and the large-scale industrial production is difficult to realize. There is interest in developing materials that are low temperature, stable and have good microwave properties.

In the traditional solid phase method, PVA has been used as a binder to improve the compactness of ceramic materials, and then is removed by heat preservation at 550 ℃ for 4 hours. However, as the sintering temperature is continuously decreased (<550 ℃), PVA cannot be completely eliminated, and the remaining PVA largely decreases the density of the ceramic and the microwave dielectric properties. Here, there is a need for improvement of the conventional solid phase method to eliminate the influence of PVA on the properties of ceramics.

The ultra-low temperature sintering microwave dielectric ceramic systems which are published and reported at present mainly have Te base and Mo base, however, in the systems, the raw material of Te is expensive and extremely toxic, and is not suitable for mass production. Mo-based materials tend to have strong water absorption, and the performance of the Mo-based materials is seriously deteriorated in air, so that the Mo-based materials are difficult to meet the industrial stability requirement.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material, and a preparation method and application thereof. Meanwhile, on the basis of not adding any sintering aid, the ethanol is used for replacing PVA and an isostatic pressing process, the technical requirements of the LTCC substrate material are met, and the application range is wide.

The invention provides an ultra-low temperature sintered microwave dielectric ceramic material which has excellent microwave performance after being sintered, and is mainly characterized by very low sintering temperature, excellent microwave dielectric performance and good stability, simultaneously can be co-sintered with Ag or Al electrodes, and has simple chemical composition and preparation process.

In order to achieve the purpose, the invention provides an environment-friendly ultralow-temperature sintered microwave dielectric ceramic material system, which comprises the following structural expressions: na (Na)₂W_xO_3x+1(x ═ 1,2,4), by sintering at an ultra-low sintering temperature range of 565 ℃ to 740 ℃.

Preferably, the ceramic material is_r＝5～12，Qf＝10000～124200GHz，τ_f-60 to-80 ppm/° c. The ceramic material can be co-fired with an Ag electrode or an Al electrode.

The second purpose of the invention is to provide a preparation method of the ultralow temperature sintered microwave dielectric ceramic material.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material system is characterized by comprising the following steps of: according to the general formula Na₂W_xO_3x+1(x ═ 1,2,4), weighedThe raw materials are uniformly mixed by adopting primary ball milling, then are presintered at the temperature of 400-.

Preferably, the primary ball milling is carried out in a ball milling tank, and zirconium balls, raw materials and absolute ethyl alcohol are added into the ball milling tank, wherein the mass ratio of the zirconium balls: the raw materials are 2:1, and the raw materials are just immersed in the absolute ethyl alcohol.

Preferably, the parameters of the primary ball milling are as follows: the speed is 200-400r/min, and the time is 4 hours.

Preferably, the powder obtained after primary ball milling is dried in a common oven at 100-150 ℃ and then is placed in a crucible for presintering.

Preferably, the tabletting process of the tabletting sintering is as follows: adding 10 percent by weight of ethanol into the powder after the secondary ball milling, molding under the pressure of 100-150MPa, and then pressing in an isostatic press under the pressure of 200-300 MPa. After pressing, the mixture was incubated at 120 ℃ for 1-2 hours to remove ethanol.

Preferably, after compression molding, the mixture is heat-preserved at 120 ℃ until ethanol is removed.

Preferably, the preparation method of the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material comprises the following steps:

1) mixing raw material Na₂CO₃And WO₃Prepared according to a formula general formula, wherein the formula is Na₂W_xO_3x+1，x＝1,2,4；

2) Putting the weighed zirconium balls, raw materials and absolute ethyl alcohol into a ball milling tank, and mixing the raw materials according to the mass ratio of the zirconium balls: adding zirconium balls and the raw materials in a mass ratio of 2:1, just immersing the raw materials in absolute ethyl alcohol, sealing, and ball-milling for 4 hours on a planetary ball mill at a rotating speed of 200-400 r/min;

3) taking the powder subjected to the primary ball milling out of a crucible, drying the powder at 100-150 ℃, and then putting the powder into the crucible to presintere for 4 hours at 400-550 ℃ to form a phase;

4) manually grinding the pre-sintered powder, then placing the powder into a ball milling tank, and carrying out secondary ball milling according to the method same as the step 2);

5) and taking out and drying the powder subjected to secondary ball milling, adding 5-10% by mass of ethanol, performing compression molding, keeping the temperature at 120 ℃ for 1-2 h to remove the ethanol, and finally keeping the temperature at 565-740 ℃ for 6h to perform sintering to obtain the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material.

The third purpose of the invention is to disclose the application of the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material. The material system can be co-fired with Ag or Al electrodes, can be used for preparing low temperature co-fired ceramic (LTCC) substrates, and is applied to microwave resonators, filters, panel antennas and the like.

Compared with the prior art, the invention has the following beneficial technical effects:

the present inventors studied Na₂O-WO₃The system finds that the system material has excellent microwave dielectric property,_r＝5～12，Qf＝10000～124200GHz，τ_f-60 to-80 ppm/° c. In particular Na₂WO₄The ceramic can be sintered at 565 ℃, has a dielectric constant of 5.6(13.1GHz), a quality factor Q of 9474, a Qf of 124,200GHz, a temperature coefficient of resonance frequency TCF of-63 ppm/° C (25-85 ℃) and can be co-sintered with Ag or Al electrodes. The component ceramic has good stability when placed in the air, simple chemical composition and preparation process, particularly has ultra-high Qf value, and is the highest in the microwave dielectric ceramic system with the sintering temperature lower than 600 ℃ reported at present.

The ceramic material system is prepared by adopting a simple and effective improved solid-phase reaction synthesis method. Firstly, weighing materials according to a formula design. Then, the raw materials are uniformly mixed by adopting primary ball milling, the required phase is synthesized by presintering at a proper temperature, and the synthesized powder is ground by adopting secondary ball milling. Finally, the required ceramic sample is obtained through tabletting and sintering. By the simple and effective preparation method, the dielectric constant of the obtained ceramic sample is changed between 5 and 12, the quality factor Qf is distributed between 10,000 and 124,200GHz, the temperature coefficient of resonance frequency is between-60 and-80 ppm/DEG C, the sintering temperature is between 565 and 740 ℃, and the ceramic sample can be co-sintered with Ag or Al electrodes, so that the ceramic sample is suitable for the requirement of LTCC technology.

Drawings

FIG. 1 is an XRD pattern of the samples of examples 1,2, 3;

FIG. 2 is a relative density plot of the samples of example 1;

FIG. 3 is a graph of the Qf values of the samples of example 1.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

The structural expression general formula of the ultralow temperature sintered microwave dielectric ceramic is as follows:

Na₂W_xO_3x+1，(x＝1,2,4)。

the preparation process of the ultralow temperature sintered microwave dielectric ceramic comprises the following steps:

1) mixing chemical raw material Na₂CO₃(purity 99.8%) and WO₃(purity 99.8%) according to the formula Na₂W_xO_3x+1(x is 1,2, 4);

2) putting the weighed raw materials into a ball milling tank, and adding zirconium balls, the raw materials and absolute ethyl alcohol into the ball milling tank, wherein the mass ratio of the zirconium balls: the raw materials are 2:1, the raw materials are just immersed in absolute ethyl alcohol, and the raw materials are placed on a planetary ball mill to be ball-milled for 4 hours at the rotating speed of 200-400r/min after being sealed;

3) taking out the powder after the primary ball milling, drying the powder (the drying temperature is 100-;

4) manually grinding the pre-sintered powder, putting the powder into a ball milling tank, sealing the powder according to the same proportion in the step 2), and then putting the powder on a planetary ball mill for ball milling for 4 hours at the rotating speed of 200-;

5) taking out the powder after ball milling, drying at the drying temperature of 100-. After pressing, the mixture was incubated at 120 ℃ for 1-2 hours to remove ethanol. Then the microwave dielectric ceramic material is sintered by heat preservation for 6h at 565-.

The ultralow temperature sintered microwave dielectric ceramic substrate material has the following characteristics: the dielectric constant is relatively low (5-12), the dielectric loss is low (10,000-124,200 GHz), the temperature coefficient of resonance frequency (TCF is-60 to-80 ppm/DEG C), the sintering temperature is ultralow (565-740 ℃), the ceramic can be co-sintered with Ag or Al electrodes, and the chemical composition and the preparation process are simple. The invention meets the requirement of environmental protection, has no toxicity and no pollution to the environment.

According to the theory related to crystal chemistry and dielectric physics, the invention selects low-melting point oxide as the starting raw material and takes Na as₂O-WO₃The microwave dielectric ceramic material which is sintered at ultralow temperature and has good microwave performance is obtained by adopting the solid phase synthesis process based on the low-burning compound in the binary system phase diagram.

Example 1

Raw material Na with analytical purity₂CO₃And WO₃Preparing main powder according to a ratio of 1:1, fully mixing and ball-milling the main powder for 4 hours, drying, pre-sintering at 400 ℃ for 4 hours, crushing the pre-sintered block sample, performing secondary ball-milling for 4 hours, grinding, drying, adding 10 wt% of ethanol, forming (sheet or column) at 100MPa, pressing in an isostatic press at 200MPa, keeping the temperature at 120 ℃ for 2 hours, removing the ethanol, and sintering at 565 ℃ for 6 hours to obtain the ceramic material of the ultra-low temperature sintering microwave dielectric.

The microwave dielectric property and the temperature spectrum of the sample are tested by a closed cavity resonance method by using a network analyzer (8720ES Agilent) and a temperature box (Delta 9023, Delta Design). The formula for TCF is as follows:

f₈₅and f₂₅Respectively at 85 ℃ and 25 ℃ TE₀₁The resonant frequency of the mode.

The performance of the group of ceramic materials reaches the following indexes:

Na₂WO₄sintering into porcelain in air at 565 deg.C, dielectric property_r5.6(13.1GHz), quality factor Q-9474, Qf-124,200 GHz, temperature coefficient of resonance frequency TCF-63 ppm/DEG C (25-85 ℃) and good stability in air.

Example 2

Raw material Na with analytical purity₂CO₃And WO₃Preparing main powder according to a ratio of 1:2, fully mixing and ball-milling the main powder for 4 hours, drying, pre-sintering at 400 ℃ for 4 hours, crushing the pre-sintered massive sample, performing secondary ball-milling for 4 hours, grinding, drying, adding 10 wt% of ethanol, forming (sheet or column) at 100MPa, pressing in an isostatic press at 200MPa, keeping the temperature at 120 ℃ for 2 hours, removing the ethanol, and sintering at 650 ℃ for 6 hours to obtain the ceramic material of the ultralow-temperature sintering microwave dielectric.

Na₂W₂O₇sintering into porcelain in air at 650 deg.C, dielectric property_r8.1(11.7GHz), quality factor Q-1932, Qf-22,600 GHz, and temperature coefficient of resonance frequency TCF-78 ppm/DEG C (25-85 ℃).

Example 3

Raw material Na with analytical purity₂CO₃And WO₃Preparing main powder according to a ratio of 1:4, fully mixing and ball-milling the main powder for 4 hours, drying, pre-sintering at 550 ℃ for 4 hours, crushing the pre-sintered block sample, ball-milling for 4 hours again, grinding and bakingAdding 10 wt% of ethanol after drying, forming (sheet or column) according to the requirement under the pressure of 100MPa, pressing under the pressure of 200MPa in an isostatic press, keeping the temperature at 120 ℃ for 2h to remove the ethanol, and sintering at 740 ℃ for 6h to form porcelain, thus obtaining the ultralow temperature sintering microwave dielectric ceramic material.

Na₂W₄O₁₃sintering into porcelain in air at 740 deg.C, dielectric property under microwave_r11.2(10.1GHz), quality factors Q-1089, Qf-11,006 GHz, and a temperature coefficient TCF of resonance frequency under microwave to-65 ppm/DEG C (25-85 ℃).

FIG. 1 shows the XRD results of the above examples 1-3, and it can be seen that pure phases of the corresponding components can be obtained at a proper pre-sintering temperature without other miscellaneous items; FIG. 2 is a graph showing the relative density of the component ceramic of example 1 as a function of sintering temperature. As can be seen from the figure, the ceramic has a relative density of up to 95.8% at a sintering temperature of 560 ℃, and the relative density of the sample is 96.1% after being left in air for 60 days. FIG. 3 is a graph of the Qf values of the component ceramics of example 1 as a function of sintering temperature. It can be seen from fig. 3 that the Qf value of the composition reaches 124200 at 565 c sintering, and only 4.6% to 118500 drops after 60 days of air exposure. Fig. 2 and fig. 3 show that the component ceramic not only has excellent dielectric properties, but also has good stability when placed in air.

By comparing examples 1,2 and 3, it can be seen that Na proposed by the present invention₂W_xO_3x+1(x ═ 1,2,4) bodiesHas excellent microwave dielectric properties (_r5 to 12, Qf 10,000 to 124,200GHz, TCF-60 to-80 ppm/DEG C). The invention has the advantages that the novel low-loss system can be sintered at ultralow temperature and has excellent microwave dielectric property and good stability.

It should be noted that, according to the technical scheme of the present invention, many examples can be mentioned in the above embodiments, and based on a great deal of experimental results of the applicant, the object of the present invention can be achieved within the scope set by the claims of the present invention.

Claims

1. A low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material is characterized by comprising the following components in percentage by weight: na (Na)₂W_xO_3x+1Wherein x is 1,2 or 4;

of ceramic materials_r＝5～12，Qf＝10000～124200GHz，τ_f＝-60～-80ppm/℃。

2. The low loss tungsten based ultra-low temperature sintered microwave dielectric ceramic material of claim 1, wherein the ceramic material can be co-fired with Ag or Al electrodes.

3. A preparation method of a low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material is characterized in that the ceramic material is prepared according to a composition expression Na₂W_xO_3x+1Wherein x is 1,2 or 4; weighing raw material Na₂CO₃And WO₃Uniformly mixing the raw materials by adopting primary ball milling, then performing presintering at 400-550 ℃ to generate a specific phase, performing secondary ball milling on a presintering product to reduce the particle size of the raw materials, and finally performing tabletting sintering and densification at 565-740 ℃ to obtain the low-loss tungsten-based ultralow-temperature sintering microwave dielectric ceramic material.

4. The method for preparing the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material as claimed in claim 3, wherein the primary ball milling is carried out in a ball milling tank, and zirconium balls, raw materials and absolute ethyl alcohol are added into the ball milling tank; wherein, according to the mass ratio, the zirconium ball: the raw material is 2:1, and the absolute ethyl alcohol is based on the condition that the raw material can be immersed; the primary ball milling speed is 200-400r/min, and the ball milling time is 4 h.

5. The preparation method of the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material as claimed in claim 3, wherein the powder obtained after primary ball milling is dried at 100-150 ℃ and then is placed in a crucible for presintering.

6. The preparation method of the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material as claimed in claim 3, wherein 5-10% by mass of ethanol is added into the powder after the secondary ball milling, the mixture is molded under the pressure of 100-150MPa, and then the molding is carried out in an isostatic press under the pressure of 200-300 MPa.

7. The method for preparing the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material as claimed in claim 3, wherein after the step of press forming, the ceramic material is subjected to heat preservation treatment at 120 ℃ until ethanol is removed.

8. The method for preparing the low-loss tungsten-based ultralow-temperature sintered microwave dielectric ceramic material as claimed in claim 3, wherein the method comprises the following steps:

9. The use of the low-loss tungsten-based ultra-low temperature sintered microwave dielectric ceramic material according to any one of claims 1 to 2 in the preparation of low temperature co-fired ceramic substrates, microwave resonators, filters or panel antennas.