CN102219505A - Microwave tuned composite ceramic material and preparation method thereof - Google Patents

Abstract

The invention discloses a microwave tuning composite ceramic material, which is composed of Mn-doped Ba _1-x Sr _x TiO ₃ and a mixture, the molar percentage of Mn is 0.1-2%, and the Mn-doped Ba _1- The mass percentage of _x Sr _x TiO ₃ is 30-95%, x=0.3-0.7, the mixture is composed of Mg ₂ SiO ₄ and MgO, and the mass percentage of Mg ₂ SiO ₄ in the mixture is 1-99%. The invention also discloses a preparation method of the composite ceramic material, that is, first preparing Mn-doped Ba _1-x Sr _x TiO ₃ and Mg ₂ SiO ₄ respectively according to the stoichiometric ratio, after ball milling, discharging, drying, pre- Burn to obtain _Mn -doped Ba _{1 -x} Sr _x TiO ₃ and Mg ₂ SiO ₄ powders respectively, _and then dope Mg ₂ SiO ₄ and MgO, ball milling, drying, granulation, molding, debinding, and finally sintering at a furnace temperature of 1200 ^o C-1400 ^o C for 2h-4h to obtain the required material. The material has moderate dielectric constant, low dielectric loss, high tuning rate, high performance and low sintering temperature, and can be used in phase shifters, tunable filters, delay lines, oscillators, resonators and phased arrays In microwave devices such as antennas.

Description

A kind of microwave tuning composite ceramic material and preparation method thereof

technical field

The invention belongs to microwave ceramic material technology, in particular to a Mn-doped Ba _x Sr _1-x TiO ₃ -MgO-Mg ₂ SiO ₄ microwave tuning composite ceramic material and a preparation method thereof.

Background technique

Microwave devices such as tunable filters, delay lines, phase shifters, oscillators, resonators and phased array antennas are important devices in the field of microwave communications, but their high cost limits their wide commercial application. Low-cost tuning technology will revolutionize the microwave components and antenna industry.

The dielectric constant of microwave tuning materials can change with the applied voltage. Applied in the field of microwave communication, the operating frequency of the component can be changed by applying an external voltage, such as a filter that can produce frequency hopping, which is very important for future broadband communication, because it can enable several users to transmit and receive in a common frequency range Signal. New microwave tuning materials can greatly reduce the cost of phased array antennas, and will expand the application of phased array antennas from the current military to civilian use. The speed, accuracy and reliability of the phased array antenna are higher than the corresponding mechanical steering antenna.

Microwave tuning materials can be used to make phase shifters. The current phase shifters are mainly ferrite phase shifters and semiconductor diode phase shifters. However, at high frequencies, PIN diodes have the disadvantages of large loss and low power, which require a logic circuit to control phase shift and cannot be tuned continuously; ferrite has low loss and high power above 3GHz, but its tuning circuit is expensive and bulky. Big, bulky, high power consumption, only used in the military field, in addition, the loss of ferrite at 1-2GHz is greater than at 10GHz, not suitable for cellular phones and personal communication services. Ferrite phase shifters are difficult to make planar structures.

The dielectric constant of barium strontium titanate can change with the applied electric field, so it is a suitable microwave tuning material. Barium strontium titanate can be applied to various antennas, however, the microwave dielectric loss of barium strontium titanate is too high, and the material needs to be improved. In addition, too large a dielectric constant will lead to too large insertion loss, which makes it difficult to match with the circuit. Therefore, how to obtain barium strontium titanate with moderate dielectric constant and high tuning rate is a technical difficulty.

Barium strontium titanate Ba _1-x Sr _x TiO ₃ composite ceramics have low dielectric constant, dielectric loss and high tuning efficiency, among which Ba _1-x Sr _x TiO ₃ -MgO has the best comprehensive performance. The sintering temperature of Ba _1-x Sr _x TiO ₃ -MgO-Mg ₂ SiO ₄ is significantly lower than that of Ba _1-x Sr _x TiO ₃ -MgO, but the addition of Mg ₂ SiO ₄ will increase the microwave dielectric loss.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a microwave tuning composite ceramic material, which has moderate dielectric constant, low dielectric loss and high tuning rate, and is especially suitable for microwave tuning components; the invention also provides the material method of preparation.

The invention provides a microwave tuning composite ceramic material, which is composed of Mn-doped Ba _1-x Sr _x TiO ₃ and a mixture, wherein the mass percentage of the Mn-doped Ba _1-x Sr _x TiO ₃ is 30 -95%, x=0.3-0.7, the molar percentage of Mn relative to Ba _1-x Sr _x TiO ₃ is 0.1-2%, the mixture is composed of Mg ₂ SiO ₄ and MgO, the Mg ₂ SiO ₄ in the mixture The mass percentage is 1-99%.

The present invention also provides a method for preparing the above-mentioned microwave tuning composite ceramic material, comprising the following steps:

(1) Prepare Mn-doped Ba _1-x Sr _x TiO ₃ and Mg ₂ SiO ₄ powders;

(2) According to the ratio, mix powdered Mg ₂ SiO ₄ and MgO into the Mn-doped Ba _1-x Sr _x TiO ₃ powder, dry it after wet ball milling for 6-24 hours;

(3) adding 3-8wt% polyvinyl alcohol to the dried material to granulate, and then pressing to form a green body;

(4) Heating the green body to 400-800° C. at a heating rate less than or equal to 30° C./minute, and then keeping it warm for 2-4 hours to remove organic matter in the green body;

(5) Sintering in the range of 1200° C. to 1400° C., followed by heat preservation for 2-4 hours, to obtain a microwave tuning composite ceramic material.

Further, the above-mentioned step (1) includes the following sub-steps:

(a) mix powdered BaTiO ₃ , SrTiO ₃ and MnCO ₃ in proportion as a group of raw materials, and mix powdered SiO ₂ and MgO in proportion as another group of raw materials;

(b) wet ball milling the two groups of raw materials for 6-24 hours respectively, then discharging and drying;

(c) Calcining in the range of 1000°C-1300°C for 2-6 hours to obtain Mn-doped Ba _1-x Sr _x TiO ₃ and Mg ₂ SiO ₄ powders respectively.

The beneficial effects of the present invention are as follows:

1. The composite ceramic material of the present invention, by adding Mn in Ba _1-x Sr _x TiO ₃ , suppresses Ti reduction in Ba _1-x Sr _x TiO ₃ , and has little influence on dielectric constant and tuning rate In the case of Ba _1-x Sr _x TiO ₃ -Mg ₂ SiO ₄ -MgO, the microwave dielectric loss of Ba 1-x Sr x TiO 3 -Mg 2 SiO 4 -MgO can be sintered in the range of 1200 ° C -1400 ° C, and has a moderate dielectric constant, dielectric Excellent properties such as low loss and high tuning rate have achieved both high performance and low sintering temperature.

2. The composite ceramic material of the present invention, its composition is Ba _1-x Sr _x TiO ₃ , Mg ₂ SiO ₄ and MgO three-phase composite, and there is no impurity phase.

3. The composite ceramic material of the present invention can be widely used in variable capacitors, adjustable filters, phase shifters, adjustable delay lines, voltage-controlled oscillators, adjustable dielectric resonators, and adjustable impedance matching devices and other tunable microwave devices. Among them, the phase shifter is an important component of the phased array antenna, which directly determines the cost and performance of the phased array antenna. The material can replace the expensive ferrite used in the phased array antenna, making the phased array antenna smaller in size, lighter in weight and cheaper in price.

4. The preparation method of the composite ceramic material of the present invention adopts the traditional electronic ceramic preparation process, the process is simple, the cost is low, and the material system is environmentally friendly and has no toxic and side effects.

Description of drawings

Figure 1 XRD spectrum of Mn-doped Ba _0.5 Sr _0.5 TiO ₃ -MgO-Mg ₂ SiO ₄ composite ceramics;

Fig. 2. Curves of the tuning ratio of Mn-doped Ba _0.5 Sr _0.5 TiO ₃ -MgO-Mg ₂ SiO ₄ composite ceramics versus the applied DC field strength.

Detailed ways

The present invention is described in more detail below by means of examples, but the following examples are only illustrative, and the protection scope of the present invention is not limited by these examples.

Examples 1-5:

Using powdered MnCO ₃ , BaTiO ₃ , SrTiO ₃ , SiO ₂ and MgO as raw materials, Ba _1-x Sr _x TiO ₃ (x=0.5) and Mg ₂ SiO ₄ doped with different contents of Mn were prepared according to the stoichiometric ratio , adding absolute ethanol or deionized water to the raw material, using agate balls or zirconia as the ball milling medium, after wet ball milling for 6 hours, discharging, drying, and pre-calcining the powder at 1100°C for 2 hours to obtain Mn-doped Ba _1-x Sr _x TiO ₃ (x=0.5) and Mg ₂ SiO ₄ powders with impurity contents of 0, 0.25, 0.5, 0.75 and 1 mol%, Ba _1-x Sr _x TiO ₃ doped with different contents of Mn (x=0.5), Mg ₂ SiO ₄ and MgO were mixed in a mass ratio of 50; 40:10 (respectively examples 1-5), wet ball milled for 6 hours, discharged and dried, using 5wt% polyvinyl alcohol as a viscous The mixture is granulated, and the powder is compacted under a pressure of 150MPa; after debinding at 600°C, it is sintered at 1330°C for 3 hours in an air atmosphere to obtain Mn-doped Ba _1-x Sr _x TiO ₃ -MgO- Mg ₂ SiO ₄ composite ceramics. The fired samples are finely ground, ultrasonically cleaned, and then silver electrodes are applied, which can be used for dielectric property testing. The columnar sample is not connected to the electrode, and the microwave dielectric properties are tested by the Hakki-Coleman method.

Dielectric Constant, Dielectric Loss, Tuning Ratio and Microwave Dielectric of Mn-doped Ba _1-x Sr _x TiO ₃ -MgO-Mg ₂ SiO ₄ Composite Ceramics at 10kHz The properties are shown in Table 1.

Table 1 Dielectric properties of Mn-doped Ba _1-x Sr _x TiO ₃ -MgO-Mg ₂ SiO ₄ composite ceramics

example Example 1 Example 2 Example 3 Example 4 Example 5 Mn content (mol%) 0 0.25 0.5 0.75 1 Permittivity (10kHz) 130.2 124.1 132.2 121.4 118.7 Dielectric loss (10kHz) 0.00065 0.00062 0.00048 0.00042 0.00044 Tuning rate (2kV/mm) 6.4% 6.5% 7.37% 7.33% 7.9% Tuning rate (3kV/mm) 11.1% 11.27% 12.86% 12.3% 13% Resonant frequency (GHz) 3.42 3.83 3.7 3.82 4.02 Permittivity (microwave) 128.03 118.63 127.01 117.81 114.22 Qf(GHz) 475 618 574 570 583

The XRD spectrum of the Mn-doped Ba _1-x Sr _x TiO ₃ -MgO-Mg ₂ SiO ₄ composite ceramic obtained from the formula of Example 1-5 is shown in FIG. 1 . The composite ceramic material is composed of three phases of Ba _1-x Sr _x TiO ₃ (x=0.5), MgO and Mg ₂ SiO ₄ . The tuning ratios of the Ba _1-x Sr _x TiO ₃ -MgO-Mg ₂ SiO ₄ composite ceramics obtained from the formulas of Examples 1-5 under different DC electric field intensities are shown in Fig. 2 . Compared with Example 1 without Mn doping, the dielectric loss of the composite ceramics decreases at 10kHz, and the Qf increases at microwave frequencies. The Qf of Example 2 increases by 30% compared with Example 1, while the tuning rate remains basically unchanged. The Qf values of Examples 3, 4 and 5 are also increased by more than 20%, while the tuning rate is even slightly increased. Apparently, doping Mn in Ba _1-x Sr _x TiO ₃ -MgO-Mg ₂ SiO ₄ composite ceramics can reduce the microwave dielectric loss of the ceramics while the tuning rate is basically unchanged.

Example 6: The molar percentage of Mn is 0.1%, the mass percentage of Ba _1-x Sr _x TiO ₃ (x=0.3) is 30%, and the mass percentage of Mg ₂ SiO ₄ in the mixture is 1%;

Example 7: The molar percentage of Mn is 0.6%, the mass percentage of Ba _1-x Sr _x TiO ₃ (x=0.45) is 40%, and the mass percentage of Mg ₂ SiO ₄ in the mixture is 50%;

Example 8: The molar percentage of Mn is 1.5%, the mass percentage of Ba _1-x Sr _x TiO ₃ (x=0.6) is 60%, and the mass percentage of Mg ₂ SiO ₄ in the mixture is 80%;

Example 9: The molar percentage of Mn is 2%, the mass percentage of Ba _1-x Sr _x TiO ₃ (x=0.7) is 95%, and the mass percentage of Mg ₂ SiO ₄ in the mixture is 99%;

Using the materials and chemical ratios described in Examples 6-9 above, microwave tuning composite ceramic materials were prepared according to the following process, and the obtained materials could all achieve the technical effects described in the present invention.

(1) Prepare Mn-doped Ba _1-x Sr _x TiO ₃ and Mg ₂ SiO ₄ respectively according to the stoichiometric ratio,

The raw materials are powdered BaTiO ₃ , SrTiO ₃ , MnCO ₃ , SiO ₂ and MgO, then add absolute ethanol or deionized water, use agate balls or zirconia as the ball milling medium, and after ball milling for 6h-24h, discharge and bake Dry, the powder is pre-calcined in the range of 1000°C-1300°C for 2h-6h to obtain Mn-doped Ba _1-x Sr _x TiO ₃ and Mg ₂ SiO ₄ powders respectively;

(2) According to the composition ratio, mix Mg ₂ SiO ₄ and MgO into Mn-doped Ba _1-x Sr _x TiO ₃ powder, then add absolute ethanol or deionized water, and use agate balls or zirconia For ball milling medium, ball milling 6h-24h;

(3) adding 3-8wt% polyvinyl alcohol to the dried mixture to granulate and press to form a green body;

(4) Raise the temperature to below 800°C and keep it warm for 2-4 hours to remove the organic matter in the green body, and the temperature rise rate during the debinding process should not be higher than 30°C/min;

(5) The green body is sintered in the range of 1200°C-1400°C and kept for 2h-4h to obtain the required block with excellent performance.

The examples in the present invention are only used to illustrate the present invention, and do not constitute a limitation to the scope of the claims. Other substantially equivalent substitutions that can be imagined by those skilled in the art all fall within the protection scope of the present invention.

Claims (3)

1. a microwave-tuned composite ceramic material is characterized in that, it is by the adulterated Ba of Mn _1-xSr _xTiO ₃Constitute with mixture, wherein, the adulterated Ba of described Mn _1-xSr _xTiO ₃Mass percent be 30-95%, x=0.3-0.7, Mn is with respect to Ba _1-xSr _xTiO ₃Molar percentage be 0.1-2%, described mixture is by Mg ₂SiO ₄Constitute Mg with MgO ₂SiO ₄Mass percent in mixture is 1-99%.

2. the preparation method of the described microwave-tuned composite ceramic material of claim 1 comprises the steps:

(1) the adulterated Ba of preparation Mn _1-xSr _xTiO ₃And Mg ₂SiO ₄Powder;

(2) according to proportioning at the adulterated Ba of Mn _1-xSr _xTiO ₃Mix pulverous Mg in the powder ₂SiO ₄And MgO, oven dry after wet ball grinding 6-24 hour;

(3) the polyvinyl alcohol granulation of adding 3-8wt%, compression moulding green compact again in the material after oven dry;

(4) green compact are heated to 400-800 ℃, heat-up rate is incubated 2-4 hour then smaller or equal to 30 ℃/minute, gets rid of the organic substance in the green compact;

(5) sintering in 1200 ℃ of-1400 ℃ of scopes is incubated 2-4 hour again, obtains microwave-tuned composite ceramic material.

3. the preparation method of microwave-tuned composite ceramic material according to claim 2 is characterized in that, step (1) comprises following substep:

(a) with pulverous BaTiO ₃, SrTiO ₃And MnCO ₃Be mixed in proportion as one group of raw material, with pulverous SiO ₂Be mixed in proportion as another group raw material with MgO;

(b) two groups of raw materials are distinguished wet ball grindings 6-24 hour, discharging then, oven dry;

(c) in 1000 ℃ of-1300 ℃ of scopes pre-burning 2-6 hour, obtain the adulterated Ba of Mn respectively _1-xSr _xTiO ₃And Mg ₂SiO ₄Powder.

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