CN101265085B - Ba1-xSrxTiO3-MgAl2O4 two-phase composite microwave ceramic material with adjustable dielectric and its preparation method - Google Patents

Abstract

The invention belongs to the technical field of electronic materials and devices, and discloses a dielectrically adjustable Ba _1-x Sr _x TiO ₃ -MgAl ₂ O ₄ two-phase composite microwave ceramic material and a preparation method thereof. The two-phase composite microwave ceramic material It consists of the following components in mass percent: Ba _1-x Sr _x TiO ₃ (x=0.3-0.9) 40.0wt.%-95.0wt.%; MgAl ₂ O ₄ 5.0wt.%-60.0wt.%. The two-phase composite microwave ceramic material provided by the invention has the characteristics of adjustable dielectric properties and low dielectric loss (high Q value) in the microwave frequency band, and can be used for adjustable microwave devices.

Description

Ba1-xSrxTiO3-MgAl2O4 two-phase composite microwave ceramic material with adjustable dielectric and its preparation method

technical field

The invention belongs to the technical field of electronic materials and devices, and in particular relates to a two-phase composite microwave ceramic material.

Background technique

Perovskite structure Ba _1-x Sr _x TiO ₃ ferroelectric materials with high dielectric constant, low dielectric loss, non-linear tunable dielectric constant and tunable Curie temperature are used as microwave tunable devices (such as shifting phase shifters, filters, variable capacitors and delay lines, etc.) are getting more and more attention, especially as microwave phase shifters. In 1994, LCSengupta of the Materials Department of the National Military Research Laboratory of the United States and WCDrach of the Microwave and Optoelectronics Department of the United States Military Research Laboratory submitted a survey report on "Electrical Characteristics of Barium Strontium Titanate (BST) Phase Shifter Materials" to the United States military department. It is proposed that if BST ferroelectric materials can replace ferrite materials to make phase shifters, phased array radar antennas will face a huge revolution. However, the BST ceramic material with high dielectric constant is difficult to meet the impedance matching with the excitation source, and it has a large dielectric loss in the microwave frequency band, which greatly limits its application in the field of microwave tunable devices. . Therefore, how to prepare materials with moderate dielectric constant, low dielectric loss and high dielectric tunability is a technical difficulty.

At present, most researchers mainly form a composite structure by adding non-ferroelectric microwave dielectric materials, so as to reduce the dielectric constant and dielectric loss in the microwave frequency range, so that it can be used in microwave tunable devices. Sengupta and others have systematically studied the composite of BST and non-ferroelectric material MgO and applied for related US patents. Although the dielectric constant and loss of the composite material have been reduced to a certain extent, with the increase of MgO content , the temperature-dependent properties of the dielectric constant and the dielectric tunable properties drop sharply. Dong Xianlin and others have also done some research work on the composite of BST ceramic materials and Mg ₂ SiO ₄ -MgO, but the contradiction between the dielectric constant and dielectric tunability of BST materials is not well resolved. Our research group has done some work on Ba _1-x Sr _x TiO ₃ -Mg ₂ TiO ₄ composite ceramic materials earlier, and has made great progress. However, Ba _1-x Sr _x TiO ₃ and MgAl ₂ O ₄ (ε _r = 8.75, Qf = 68900GHz (loss tangent = 0.00017 at 12.3GHz)) composite with excellent microwave dielectric properties and their dielectric properties have not yet been studied. See related reports.

Contents of the invention

The purpose of the present invention is to provide a two-phase composite microwave ceramic material with adjustable dielectric properties, low dielectric loss (high Q value) in the microwave frequency band and can be used for adjustable microwave devices and its preparation method.

The dielectrically adjustable two-phase composite microwave ceramic material provided by the present invention contains the following components in mass percentage:

Ba _1-x Sr _x TiO ₃ , x=0.3-0.9 40.0wt.%～95.0wt.%

MgAl ₂ O ₄ 5.0wt.%～60.0wt.%

Preferably, in the aforementioned Ba _1-x Sr _x TiO ₃ , x is preferably 0.6.

The preparation method of the two-phase composite microwave ceramic material provided by the present invention specifically comprises the following steps:

(1) Prepare Ba _1-x Sr _x TiO ₃ (x=0.3-0.9) by solid state reaction method, and obtain Ba _1-x Sr _x TiO ₃ (x=0.3-0.9) powder after grinding. Specifically:

Using the traditional electronic ceramic powder preparation process, through the solid-state reaction method, select BaTiO ₃ and SrTiO ₃ as the main raw materials, according to a certain Ba/Sr molar ratio, put the prepared raw materials in a nylon ball mill tank, add zirconia Balls, adding absolute ethanol or deionized water, ball milling for 20-24 hours, and pre-calcining at 1100°C-1250°C for 4-8 hours after drying the discharged materials, after grinding, Ba _1-x Sr _x TiO ₃ (x=0.3 -0.9) Powder.

(2) MgAl ₂ O ₄ is prepared by a solid-state reaction method, and MgAl ₂ O ₄ powder is obtained after grinding.

Synthesize MgAl ₂ O ₄ powder according to the following reaction equation:

MgO+Al ₂ O ₃ ＝MgAl ₂ O ₄

First, weigh a certain molar ratio of MgO (98.50%) and Al ₂ O ₃ (99.99%) mixture and place it in a nylon ball mill jar, add zirconia balls, add absolute ethanol or deionized water, and ball mill for 20 to 24 hours , after discharging and drying, pre-calcine at 1250°C-1450°C for 4-8 hours, and obtain MgAl ₂ O ₄ powder after grinding.

(3) Weigh the mixture according to the following component distribution ratio, add zirconia balls, add absolute ethanol or deionized water, ball mill for 20 to 24 hours, and pass through a 200-mesh sieve after drying to obtain a composite powder.

Ba _1-x Sr _x TiO ₃ (x=0.3-0.9) powder 95.0wt.%～40.0wt.%

MgAl ₂ O ₄ powder 5.0wt.%～60.0wt.%

(4) Use 8-10% polyvinyl alcohol (PVA) as a binder to granulate the above-mentioned composite powder, and under a pressure of 10-100 MPa, press different types of molding dies to form ceramic raw materials of required size. Blank.

(5) After the ceramic green sheet is debonded at 550°C-600°C, the obtained ceramic sheet is sintered at 1400°C-1600°C (for 2-4 hours) to obtain the composite microwave ceramic material.

Wherein the mass ratio of the zirconia ball to the ball grinding material is 1.2-1.5; the mass ratio of the absolute ethanol or deionized water to the ball grinding material is 1.5-3.0.

Ball milling material refers to the sum of the main raw materials of ball milling, BaTiO ₃ and SrTiO ₃ in step 1, MgO and Al ₂ O ₃ in step 2, Ba _1-x Sr _x TiO ₃ in step 3 (x=0.3-0.9 ) powder and MgAl ₂ O ₄ powder.

The present invention adopts the traditional electronic ceramic preparation technology, selects microwave dielectric material magnesium aluminate (MgAl ₂ O ₄ ) and strontium barium titanate ferroelectric material with different Ba/Sr components to carry out two-phase gradient compounding, and develops a kind of Ba _1-x Sr _x TiO ₃ -MgAl ₂ O ₄ two-phase composite microwave ceramic material with tunable dielectric properties, low dielectric loss (high Q value) in the microwave frequency band and can be used for tunable microwave devices, which has the following main Features:

(1) The Curie temperature of the composite ceramic material system can be continuously adjusted in a wide range with the Ba/Sr ratio, and the structure and performance of the material system can be adjusted according to the working temperature requirements of the designed adjustable microwave device;

(2) By changing the content of Ba _1-x Sr _x TiO ₃ (x=0.3-0.9), MgAl ₂ O ₄ two-phase composite components, the dielectric constant of the composite ceramic material can be continuously adjusted between 15 and 2000 , the material system with serialized dielectric constant can be obtained, which broadens the application range of materials;

(3) Under the action of an external DC electric field, the composite microwave ceramic material has high dielectric adjustable properties (≥10%), and has a high Q value (≥200) in the microwave frequency band;

(4) The composition of the composite ceramic material exists in a pure two-phase form of Ba _1-x Sr _x TiO ₃ (x=0.3-0.9) and MgAl ₂ O ₄ , without the formation of other impurity phases, and has excellent dielectric properties performance;

(5) The traditional electronic ceramic preparation process is adopted, the process is simple, the cost is low, the material system is environmentally friendly, has no toxic side effects, and has excellent performance, which is suitable for the development and design of adjustable microwave devices.

Description of drawings

Fig. 1 is an X-ray diffraction analysis pattern of (1-x)Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material.

Fig. 2 is the relationship curve of dielectric constant and loss with temperature of (1-x)Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material.

Fig. 3 is the relationship curve between the dielectric constant and loss of (1-x)Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material and the applied DC field strength.

Detailed ways

Example 1-5 Preparation of (1-x) Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material:

According to the stoichiometric ratio of Ba _0.4 Sr _0.6 TiO ₃ , weigh 93.291g BaTiO ₃ and 110.110g SrTiO ₃ (99.90%, 100nm, provided by Shandong Guoci Functional Ceramic Material Co., Ltd.) Zirconium balls and anhydrous ethanol or deionized water are ball milled for 24 hours. After the discharge is dried, it is pre-calcined at 1100°C to 1250°C for 4 hours. After grinding, Ba _0.4 Sr _0.6 TiO ₃ powder is obtained for use. In addition, weigh 10.228g MgO and 25.493g Al ₂ O ₃ powders respectively and place them in a nylon ball mill jar, add zirconia balls and absolute ethanol or deionized water, and ball mill for 24 hours. Pre-calcined at 1450°C for 4 hours and ground to obtain MgAl ₂ O ₄ powder for use.

Weigh the Ba _0.4 Sr _0.6 TiO ₃ and MgAl ₂ O ₄ ready-to-use powders synthesized above according to the composition ratio of the composite components in Table 1:

Table 1. Ratio of (1-x)Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic materials

生坯片和10mm×5mm、15mm×7mm、18mm×9mm、25mm×12mm的圆柱体，经过550℃的排粘处理后，样品在空气气氛下，烧结温度为1500℃，保温4小时后，得到(1-x)Ba_0.4Sr_0.6TiO₃-xMgAl₂O₄两相复合微波陶瓷样品。将制得的陶瓷样品先进行两面抛光、被银，烧银后进行物相成分分析和介电性能测试，其相关介电性能见表2。Put the mixed materials of the above formulas into a nylon ball mill tank, add zirconia balls and absolute ethanol ball mill for 24 hours, and pass through a 200-mesh sieve after drying. According to the traditional electronic ceramic preparation process, 8% poly Vinyl alcohol (PVA) is used as a binder for granulation, and under a pressure of 10MPa, it is dry-pressed into a diameter

Green sheets and cylinders of 10mm×5mm, 15mm×7mm, 18mm×9mm, 25mm×12mm, after debonding treatment at 550°C, the samples were sintered at 1500°C in air atmosphere, and kept for 4 hours, to obtain (1-x)Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic samples. The prepared ceramic samples were first polished on both sides, covered with silver, and then subjected to phase composition analysis and dielectric property test after silver firing. The relevant dielectric properties are shown in Table 2.

Table 2. Relative dielectric properties of (1-x)Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic materials

Example 1 The X-ray diffraction analysis spectrum of the (1- ^x )Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material prepared by the formula ^# -5 # is shown in Figure 1, and the results show that the Ba _0.4 Sr _0.6 TiO ₃ and MgAl ₂ O ₄ coexist in a pure two-phase form, and no other impurity phases are formed; (1-x)Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O prepared by the formula of Example 1 ^# -5 ^# _4. The relationship curves of dielectric constant, loss and temperature of two-phase composite microwave ceramic materials are shown in Figure 2. The results show that with the increase of MgAl ₂ O ₄ content, the Curie peak moves to high temperature and is broadened and suppressed; Example The relation curves of the dielectric constant and loss of the (1- ^x )Ba _0.4 Sr _0.6 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material and the external DC field strength prepared by 1 ^# -5 # formula are shown in Fig. 3 The test results show that the modulation increases with the increase of MgAl ₂ O ₄ content.

Example 6 Preparation of (1-x)Ba _0.7 Sr _0.3 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material:

According to the stoichiometric ratio of Ba _0.7 Sr _0.3 TiO ₃ , weigh 163.259g BaTiO ₃ and 55.055g SrTiO ₃ (99.90%, 100nm, provided by Shandong Guoci Functional Ceramic Material Co., Ltd.) Zirconium balls and anhydrous ethanol or deionized water are ball milled for 24 hours. After the discharge is dried, it is pre-calcined at 1100°C to 1250°C for 4 hours. After grinding, Ba _0.7 Sr _0.3 TiO ₃ powder is obtained for use. In addition, weigh 10.228g MgO and 25.493g Al ₂ O ₃ powders respectively and place them in a nylon ball mill jar, add zirconia balls and absolute ethanol or deionized water, and ball mill for 24 hours. Pre-calcined at 1450°C for 4 hours and ground to obtain MgAl ₂ O ₄ powder for use.

Weigh the Ba _0.7 Sr _0.3 TiO ₃ and MgAl ₂ O ₄ ready-to-use powders synthesized above according to the composition ratio of the composite components in Table 3:

Table 3. Ratio of (1-x)Ba _0.7 Sr _0.3 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic materials

生坯片和10mm×5mm、15mm×7mm、18mm×9mm、25mm×12mm的圆柱体，经过550℃的排粘处理后，样品在空气气氛下，烧结温度为1500℃，保温4小时后，得到(1-x)Ba_0.7Sr_0.3TiO₃-xMgAl₂O₄两相复合微波陶瓷样品。Put the mixed materials of the above formulas into a nylon ball mill tank, add zirconia balls and absolute ethanol ball mill for 24 hours, and pass through a 200-mesh sieve after drying. According to the traditional electronic ceramic preparation process, 8% poly Vinyl alcohol (PVA) is used as a binder for granulation, and under a pressure of 10MPa, it is dry-pressed into a diameter

Green sheets and cylinders of 10mm×5mm, 15mm×7mm, 18mm×9mm, 25mm×12mm, after debonding treatment at 550°C, the samples were sintered at 1500°C in air atmosphere, and kept for 4 hours, to obtain (1-x)Ba _0.7 Sr _0.3 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic samples.

Example 7 Preparation of (1-x)Ba _0.1 Sr _0.9 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic material:

According to the stoichiometric ratio of Ba _0.1 Sr _0.9 TiO ₃ , weigh 23.323g BaTiO ₃ and 167.865g SrTiO ₃ (99.90%, 100nm, provided by Shandong Guoci Functional Ceramic Material Co., Ltd.) Zirconium balls and anhydrous ethanol or deionized water are ball milled for 24 hours, and the discharged material is dried and pre-calcined at 1100°C to 1250°C for 4 hours. After grinding, Ba _0.1 Sr _0.9 TiO ₃ powder is obtained for use. In addition, weigh 10.228g MgO and 25.493g Al ₂ O ₃ powders respectively and place them in a nylon ball mill jar, add zirconia balls and absolute ethanol or deionized water, and ball mill for 24 hours. Pre-calcined at 1450°C for 4 hours and ground to obtain MgAl ₂ O ₄ powder for use.

Weigh the Ba _0.1 Sr _0.9 TiO ₃ and MgAl ₂ O ₄ ready-to-use powders synthesized above according to the composition ratio of the composite components in Table 4:

Table 4. Ratio of (1-x)Ba _0.1 Sr _0.9 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic materials

生坯片和10mm×5mm、15mm×7mm、18mm×9mm、25mm×12mm的圆柱体，经过550℃的排粘处理后，样品在空气气氛下，烧结温度为1500℃，保温4小时后，得到(1-x)Ba_0.1Sr_0.9TiO₃-xMgAl₂O₄两相复合微波陶瓷样品。将制得的陶瓷样品先进行两面抛光、被银，烧银后进行物相成分分析和介电性能测试。Put the mixed materials of the above formulas into a nylon ball mill tank, add zirconia balls and absolute ethanol ball mill for 24 hours, and pass through a 200-mesh sieve after drying. According to the traditional electronic ceramic preparation process, 8% poly Vinyl alcohol (PVA) is used as a binder for granulation, and under a pressure of 10MPa, it is dry-pressed into a diameter

Green sheets and cylinders of 10mm×5mm, 15mm×7mm, 18mm×9mm, 25mm×12mm, after debonding treatment at 550°C, the samples were sintered at 1500°C in air atmosphere, and kept for 4 hours, to obtain (1-x)Ba _0.1 Sr _0.9 TiO ₃ -xMgAl ₂ O ₄ two-phase composite microwave ceramic samples. The prepared ceramic samples were firstly polished on both sides, coated with silver, and then subjected to phase composition analysis and dielectric property test after silver firing.

Claims (8)

1. two-phase composite microwave ceramic material that dielectric is adjustable, form by following component by mass percent:

Ba _1-xSr _xTiO ₃，x＝0.3-0.9 40.0wt.％～95.0wt.％

MgAl ₂O ₄ 5.0wt.％～60.0wt.％。

2. the adjustable two-phase composite microwave ceramic material of dielectric according to claim 1 is characterized in that said Ba _1-xSr _xTiO ₃In, x is 0.6.

3. the preparation method of the adjustable two-phase composite microwave ceramic material of the said dielectric of claim 1 comprises the steps:

A) adopt solid reaction process to prepare Ba _1-xSr _xTiO ₃Powder, wherein x=0.3-0.9;

B) adopt solid reaction process to prepare MgAl ₂O ₄Powder;

C) take by weighing the Ba that step a makes _1-xSr _xTiO ₃The MgAl that powder and b make ₂O ₄Powder adds zirconia ball, adds absolute ethyl alcohol or deionized water, and ball milling 20～24 hours obtains composite powder after the discharging oven dry, wherein, and Ba _1-xSr _xTiO ₃Powder and MgAl ₂O ₄Powder compares according to following set of dispense:

Ba _1-xSr _xTiO ₃Powder, x=0.3-0.9 95.0wt.%～40.0wt.%

MgAl ₂O ₄Powder 5.0wt.%～60.0wt.%;

D) Z 150PH of employing 8～10% carries out granulation as sticker to the composite powder that step c obtains, and under 10～100MPa pressure, is pressed into the ceramic green sheet through forming mould;

E) after the ceramic green sheet glues processing through row, carry out sintering processes, can obtain the adjustable two-phase composite microwave ceramic material of said dielectric.

4. like the preparation method of the adjustable two-phase composite microwave ceramic material of the said dielectric of claim 3, it is characterized in that among the said step c, the mass ratio of zirconia ball and ball milling material is 1.2～1.5, wherein the ball milling material is meant Ba _1-xSr _xTiO ₃Powder and MgAl ₂O ₄Powder.

5. like the preparation method of the adjustable two-phase composite microwave ceramic material of the said dielectric of claim 3, it is characterized in that among the said step c, the mass ratio of absolute ethyl alcohol or deionized water and ball milling material is 1.5～3.0, wherein the ball milling material is meant Ba _1-xSr _xTiO ₃Powder and MgAl ₂O ₄Powder.

6. like the preparation method of the adjustable two-phase composite microwave ceramic material of the said dielectric of claim 3, it is characterized in that the said solid reaction process of step a prepares Ba _1-xSr _xTiO ₃Powder comprises the steps:

Select BaTiO for use ₃And SrTiO ₃Be raw material, according to Ba _1-xSr _xTiO ₃The molar ratio ingredient of middle Ba/Sr places ball grinder with confected materials, adds zirconia ball, adds absolute ethyl alcohol or deionized water, ball milling 20～24 hours, and discharging oven dry back obtains Ba 1100 ℃～1250 ℃ pre-burnings 4～8 hours after the grinding _1-xSr _xTiO ₃Powder.

7. like the preparation method of the adjustable two-phase composite microwave ceramic material of the said dielectric of claim 3, it is characterized in that the said solid reaction process of step b prepares MgAl ₂O ₄Powder comprises the following steps:

Select MgO and Al for use ₂O ₃Be raw material, take by weighing MgO and Al ₂O ₃Compound places ball grinder, adds zirconia ball, adds absolute ethyl alcohol or deionized water, ball milling 20～24 hours, and discharging oven dry back obtains MgAl 1250 ℃～1450 ℃ pre-burnings 4～8 hours after the grinding ₂O ₄Powder.

8. like the preparation method of the adjustable two-phase composite microwave ceramic material of the said dielectric of arbitrary claim among the claim 3-7, it is characterized in that said Ba _1-xSr _xTiO ₃In, x is 0.6.

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