CN104671773B - A kind of low dielectric constant microwave dielectric ceramic material and preparation method thereof - Google Patents

Abstract

The invention discloses a low dielectric constant microwave dielectric ceramic material and a preparation method thereof. The phase of the ceramic material includes Li ₂ Mg ₃ SnO ₆ and Mg ₂ SnO ₄ , wherein the content of Li ₂ Mg ₃ SnO ₆ is 42 wt%. ～95wt%, the rest is Mg ₂ SnO ₄ ; the dielectric constant of the ceramic material is 7.8～8.8, the dielectric loss is 0.00007～0.00019, Q×f is 72000～123000GHz, and the resonant frequency temperature coefficient is ‑40～‑31ppm/ ℃, prepared by high-temperature solid-state reaction method. The preparation method of the microwave dielectric ceramic material of the present invention is simple, the raw materials used are abundant, the cost is low, and it is beneficial to industrial production. The performance of the prepared microwave dielectric ceramic is stable, and it can be used as an electronic circuit substrate, a dielectric resonator, a filter, and a high-frequency satellite microwave device. The use of manufacturing materials for substrates and microstrip lines has important application prospects and economic value in the fields of electronic circuits, microwave mobile communications, satellite communications, and radar systems.

Description

A kind of low dielectric constant microwave dielectric ceramic material and preparation method thereof

technical field

The invention belongs to the technical field of electronic information materials and devices thereof, and in particular relates to a low dielectric constant microwave dielectric ceramic material and a preparation method thereof.

Background technique

Microwave dielectric ceramics refer to ceramic materials used in microwave frequency (300MHz-300GHz) circuits as dielectric materials to complete one or more functions. Ideal microwave dielectric ceramics have suitable dielectric constant (ε _r ), high quality factor (Q×f) and resonant frequency temperature coefficient (τ _f ) tending to zero. Components such as resonators, filters, and microwave integrated circuit substrates made of microwave dielectric ceramics have been widely used in modern communication technologies such as mobile communications, wireless local area networks, and military communications. In addition, as the operating frequency of communication equipment continues to increase, system loss and heat generation increase, and system stability gradually deteriorates. In order to overcome many problems caused by frequency broadening, it is urgent to develop microwave dielectric materials with high Q value and low, medium ε _r (10≤ε _r ≤25) and near zero τ _f value. Low ε _r can reduce the interaction coupling loss between the material and the electrode, and increase the signal transmission rate. Low dielectric loss is conducive to improving the selectivity of the operating frequency of the device. Near zero τ _f helps to improve the frequency and temperature stability of the device. characteristic.

Traditional low _εr ceramics are mainly composed of glass-ceramics (glass-ceramics), glass+ceramics (multiphase ceramics), etc. Although glass-ceramic materials can be sintered at relatively low temperatures, due to the introduction of a large amount of low-melting glass substances, the dielectric loss of the material is increased, and it is difficult to use at high frequencies. In order to meet the needs of high-frequency and high-speed development of electronic components, new low dielectric constant (ε _r <15), high-Q microwave dielectric ceramic materials have attracted more and more attention from domestic and foreign materials scholars. Typical low ε _r and high Q value material systems reported in recent years mainly include: M ₂ SiO ₄ (M=Mg, Zn)-based, Al ₂ O ₃ -based, A ₄ M ₂ O ₉ (A=Co, Mg; B =Nb, Ta) and spinel structure M ₂ SnO ₄ (M=Cu, Zn, Ni, etc.) based microwave dielectric ceramics.

Contents of the invention

The technical problem to be solved by the present invention is to provide a novel microwave dielectric ceramic material with low dielectric constant and excellent microwave dielectric properties and its preparation method.

The technical solution adopted to solve the above technical problems is: the phase of the low dielectric constant microwave dielectric ceramic material includes Li ₂ Mg ₃ SnO ₆ and Mg ₂ SnO ₄ , wherein the content of Li ₂ Mg ₃ SnO ₆ is 42wt%-95wt% %, the rest is Mg ₂ SnO ₄ ; the dielectric constant of the ceramic material is 7.8-8.8, the dielectric loss is 0.00007-0.00019, Q×f is 72000-123000 GHz, and the temperature coefficient of resonance frequency is -40-31ppm/℃.

The optimal content of Li ₂ Mg ₃ SnO ₆ in the above ceramic material is 52wt%, the rest is Mg ₂ SnO ₄ , its dielectric constant is 7.8, dielectric loss is 0.00007, Q×f is 123000GHz, and the temperature coefficient of resonance frequency is - 32ppm/°C.

The preparation method of the above-mentioned low dielectric constant microwave dielectric ceramic material consists of the following steps:

1. Mixing

Mix Li ₂ CO ₃ powder, MgO powder, and SnO ₂ powder with a purity greater than 99.9% in a molar ratio of 1:3:1, and then add them to a ball mill jar, use zirconia balls as the grinding balls, and absolute ethanol as the grinding medium. Mix and ball mill for 6-10 hours, and dry at 80-100°C.

2. Pre-burning

Pre-calcining the dried mixture in step 1 at 1000-1200° C. for 4-6 hours to obtain calcined powder.

3. Secondary mixing

Put the calcined powder into a ball mill jar, use zirconia balls as the grinding balls and absolute ethanol as the grinding medium, mix thoroughly and ball mill for 6-10 hours, and dry at 80-100°C.

4. Granulation and molding

Add polyvinyl alcohol aqueous solution with a mass fraction of 5% to the calcined powder dried in step 3 to granulate, pass through a sieve of 80-160 mesh, and then press into a cylindrical green body with a powder tablet press.

5. Sintering

The cylindrical green body obtained in step 4 is sintered at 1320-1400° C. for 2-10 hours to obtain a low dielectric constant microwave dielectric ceramic material.

In the above step 2, the dried mixture in step 1 is preferably pre-calcined at 1000° C. for 4 hours.

In step 5 above, the cylindrical green body obtained in step 4 was sintered at 1360° C. for 6 hours.

The preparation method of the microwave dielectric ceramic material of the present invention is simple, the raw materials used are abundant, the cost is low, and it is beneficial to industrial production. The prepared microwave dielectric ceramic has low dielectric constant and excellent microwave dielectric performance, and can be used as an electronic circuit substrate and a dielectric resonator. , filters, high-frequency satellite microwave device substrates and microstrip line manufacturing materials have important application prospects and economic value in the fields of electronic circuits, microwave mobile communications, satellite communications, and radar systems.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the low dielectric constant microwave dielectric ceramic material prepared in Examples 1-7.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

Example 1

1. Mixing

Take 2.500g (0.033mol) of Li2CO3 powder, _4.012g (0.099mol) of MgO powder and 5.023g ( _0.033mol ) of _SnO2 powder with a purity greater than 99.9%, and mix them evenly, and mix the raw material mixture with zirconia balls, absolute ethanol Put it into a ball mill tank at a mass ratio of 1:2:2, thoroughly mix and ball mill at 360 rpm for 8 hours, and dry at 80-100°C for 12 hours.

2. Pre-burning

Put the dried mixture in step 1 into an alumina crucible, raise the temperature to 1000°C at a heating rate of 2°C/min, and pre-fire at a constant temperature for 4 hours to obtain calcined powder.

3. Secondary mixing

Put calcined powder, zirconia balls, and absolute ethanol in a mass ratio of 1:2:2 into a ball mill jar, mix thoroughly and ball mill for 8 hours, and dry at 80-100°C for 12 hours.

4. Granulation and molding

Add its mass fraction to the calcined powder after step 3 drying and be 5% polyvinyl alcohol aqueous solution to granulate, cross 120 mesh sieves, and then use a powder tablet press to compress it into a diameter of 11.5mm cylindrical green body with a thickness of 5.5mm.

5. Sintering

The cylindrical green body obtained in step 4 was sintered at 1360° C. for 6 hours to obtain a low dielectric constant microwave dielectric ceramic material.

Example 2

In step 5 of embodiment 1, the cylindrical green body was sintered at 1340° C. for 6 hours, and other steps were the same as in embodiment 1 to obtain a low dielectric constant microwave dielectric ceramic material.

Example 3

In step 5 of embodiment 1, the cylindrical green body was sintered at 1320° C. for 6 hours, and other steps were the same as in embodiment 1 to obtain a low dielectric constant microwave dielectric ceramic material.

Example 4

In Step 5 of Example 1, the cylindrical green body was sintered at 1380° C. for 6 hours, and other steps were the same as in Example 1 to obtain a low dielectric constant microwave dielectric ceramic material.

Example 5

In Step 5 of Example 1, the cylindrical green body was sintered at 1400° C. for 6 hours, and other steps were the same as in Example 1 to obtain a low dielectric constant microwave dielectric ceramic material.

Example 6

In Step 5 of Example 1, the cylindrical green body was sintered at 1360° C. for 2 hours, and other steps were the same as in Example 1 to obtain a low dielectric constant microwave dielectric ceramic material.

Example 7

In Step 5 of Example 1, the cylindrical green body was sintered at 1360° C. for 10 hours, and other steps were the same as in Example 1 to obtain a low dielectric constant microwave dielectric ceramic material.

The inventors characterized the low dielectric constant microwave dielectric ceramic materials prepared in Examples 1-7 using a Raguku D/Max2550 (Japan) X-ray diffractometer, and the results are shown in FIG. 1 . It can be seen from Figure 1 that the phase composition of the prepared low dielectric constant microwave dielectric ceramic material is Li ₂ Mg ₃ SnO ₆ and Mg ₂ SnO ₄ , and the mass percentage of each phase is shown in Table 1.

The phase composition of table 1 microwave dielectric ceramic material of the present invention

Li ₂ Mg ₃ SnO ₆ (wt%) Mg ₂ SnO ₄ (wt%) Example 1 52 48 Example 2 86 14 Example 3 95 5 Example 4 44 56 Example 5 79 twenty one Example 6 65 35 Example 7 42 58

The inventor ground and polished the ceramic materials prepared in Examples 1-7 and processed them into cylinders with a diameter of 9-10 mm and a height of 5 mm, and tested the microwave dielectric properties of the ceramics with a vector network analyzer, closed-cavity resonance method and high-low temperature oven. The results are shown in Table 2.

Table 2 Dielectric properties and sintering properties of microwave dielectric ceramic material of the present invention

It can be seen from Table 2 that the microwave dielectric ceramic materials prepared in Examples 1-7 have low dielectric constant, ultra-low loss and high Q×f value, the temperature coefficient of resonance frequency is between -40～-31ppm/℃, and the sintering temperature Wide range (1320～1400℃) and stable performance, it is a new type of microwave dielectric ceramic material with low dielectric constant and excellent microwave dielectric properties.

Claims (5)

1. A low dielectric constant microwave dielectric ceramic material, characterized in that: the phase of the ceramic material includes Li ₂ Mg ₃ SnO ₆ and Mg ₂ SnO ₄ , wherein the content of Li ₂ Mg ₃ SnO ₆ is 42wt% to 95wt %, the rest is Mg ₂ SnO ₄ ; the dielectric constant of the ceramic material is 7.8-8.8, the dielectric loss is 0.00007-0.00019, Q×f is 72000-123000 GHz, and the temperature coefficient of resonance frequency is -40-31ppm/℃. 2. The low dielectric constant microwave dielectric ceramic material according to claim 1, characterized in that: the phase of the ceramic material includes Li ₂ Mg ₃ SnO ₆ and Mg ₂ SnO ₄ , wherein the content of Li ₂ Mg ₃ SnO ₆ It is 52wt%, and the rest is Mg ₂ SnO ₄ ; the dielectric constant of this ceramic material is 7.8, the dielectric loss is 0.00007, Q×f is 123000GHz, and the temperature coefficient of resonance frequency is -32ppm/°C. 3. a preparation method of low dielectric constant microwave dielectric ceramic material as claimed in claim 1, is characterized in that it is made up of following steps: (1) Mixing Mix Li ₂ CO ₃ powder, MgO powder, and SnO ₂ powder with a purity greater than 99.9% in a molar ratio of 1:3:1, and then add them to a ball mill jar, use zirconia balls as the grinding balls, and absolute ethanol as the grinding medium. Mix ball mill for 6-10 hours, dry at 80-100°C; (2) pre-burning Pre-calcining the dried mixture in step (1) at 1000-1200° C. for 4-6 hours to obtain calcined powder; (3) Secondary mixing Put the calcined powder into the ball mill jar, use zirconia balls as the grinding balls and absolute ethanol as the grinding medium, mix the balls thoroughly for 6-10 hours, and dry at 80-100°C; (4) Granulation and molding Add polyvinyl alcohol aqueous solution to the dried mixture in step (3) to granulate, the mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5%, pass through a 80-160 mesh sieve, and then use a powder tablet press to compress Into a cylindrical green body; (5) Sintering The cylindrical green body obtained in step (4) is sintered at 1320-1400° C. for 2-10 hours to obtain a low dielectric constant microwave dielectric ceramic material. 4. The method for preparing a low-dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: in the step (2), the dried mixture in the step (1) is pre-fired at 1000° C. for 4 hours. 5. The preparation method of the low dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: in the step (5), the cylindrical green body obtained in the step (4) is sintered at 1360° C. for 6 hours .