CN101792320A - Method for sintering high-dielectric CaCu3Ti4O12 ceramics by using spark plasma - Google Patents

Abstract

A method of using spark plasma sintering (SPS) high dielectric ceramics CaCu ₃ Ti ₄ O ₁₂ (abbreviated as CCTO). Put the pure CCTO powder into the mold and put the mold between the upper and lower electrodes in the SPS sintering cavity; close the sintering cavity and vacuumize it, heat up, pressurize, and keep warm; then cool with the furnace, depressurize and turn off the vacuum pump; After the temperature drops to a certain level, the product is taken out from the sintering chamber. The XRD results of the sintered product show that the sample is a pure phase, and the SEM can be used to observe that its morphology is relatively dense. The measurement of the dielectric properties shows that the sample has a high relative permittivity and low loss at room temperature.

Description

Method of Sintering High Dielectric CaCu3Ti4O12 Ceramics Using Spark Plasma

Technical field:

The invention relates to a sintering method of high dielectric CaCu ₃ Ti ₄ O ₁₂ ceramics.

Background introduction:

CaCu ₃ Ti ₄ O ₁₂ (CCTO) is a high-dielectric electronic material that is currently being researched. Its relative permittivity at room temperature and low frequency range is as high as 10 ⁴ to 10 ⁵ , and its dielectric properties are in a wide temperature range. (100-300K) is relatively stable, therefore, CCTO materials have good application prospects in microelectronics.

The traditional sintering method of CCTO ceramics is to press CCTO powder into tablets under a certain pressure (generally up to tens or even hundreds of megapascals) with an ordinary tablet press, and then sinter at high temperature in a muffle furnace. In order to obtain denser ceramics, a longer sintering time (generally tens of hours) is required. Therefore, the energy consumption is large.

Spark plasma sintering (SPS) is a sintering method that can obtain denser flake materials through short-time sintering. It has been widely used in the preparation of various alloys and ceramic materials. However, due to the special properties of CCTO, SPS sintering has not been used in the production of CCTO ceramics at present.

Invention content:

The purpose of the present invention is to provide a method that can use SPS to sinter CCTO ceramics according to the special properties of CCTO, which can not only greatly reduce the high-temperature sintering time to effectively reduce energy consumption compared with existing methods, but also maintain or increase the high dielectric properties of CCTO .

Technical scheme of the present invention is made up of the following steps:

1. Put pure CaCu ₃ Ti ₄ O ₁₂ powder into a mold and place the mold between the upper and lower electrodes in the discharge plasma sintering chamber;

2. Close the sintering chamber, turn on the vacuum pump, and evacuate the sintering chamber;

3. Increase the temperature and pressurize the sintering chamber. When the temperature rises to 800-980 degrees Celsius, pressurize to 20-70 MPa, keep it warm for 5-60 minutes, then cool down with the furnace and depressurize with the temperature, and turn off the vacuum pump;

4. When the temperature drops below 100°C, take the product out of the sintering chamber.

The above pure CaCu ₃ Ti ₄ O ₁₂ powder can be prepared by sol-gel method.

In the above-mentioned heating and pressurizing process, the pressure should gradually increase as the temperature rises, and only a little pressure should be added at low temperatures. However, the pressure can be minimized during the above furnace cooling process.

If the above-mentioned mold is a graphite mold, a carburized layer with a certain thickness will appear on the surface of the ceramic obtained by using the above-mentioned technical solution. In order to remove the infiltrated carbon, the sintered sample needs to be sintered in a muffle furnace at 500-900 ° C for 2 Hours of annealing treatment, and then the part of the ceramic surface obtained after annealing that is decomposed due to carburization is ground off and polished.

According to the sintered CCTO ceramics of the present invention, the XRD result of its sintered product shows that the sample is a pure phase, and it can be observed that its morphology is relatively compact using SEM, and the dielectric property measurement shows that the sample has a higher relative permittivity and lower loss.

Description of drawings:

Accompanying drawing 1 is the cross-sectional scanning electron microscope topography figure of the CCTO sintered of the present invention;

Accompanying drawing 2 is the dielectric property of the CCTO of different sintering temperatures of the present invention. Among them, Figure 2-1 is a comparison diagram of relative permittivity, and Figure 2-2 is a comparison diagram of loss;

Accompanying drawing 3 is the dielectric property of the CCTO of different sintering holding time of the present invention. Among them, Figure 3-1 is a comparison chart of relative permittivity, and Figure 3-2 is a comparison chart of loss;

Accompanying drawing 4 is the dielectric property of the CCTO of different sintering pressures of the present invention. Among them, Figure 4-1 is a comparison diagram of relative permittivity, and Figure 4-2 is a comparison diagram of loss;

Accompanying drawing 5 is the dielectric property of the CCTO of different annealing temperature of the present invention. Among them, Figure 5-1 is a comparison diagram of relative permittivity, and Figure 5-2 is a comparison diagram of loss;

Accompanying drawing 6 shows the dielectric properties of CCTO with annealing and holding time of 2 hours and 10 hours according to the present invention. Among them, Figure 6-1 is a comparison chart of relative permittivity, and Figure 6-2 is a comparison chart of loss;

Accompanying drawing 7 is the dielectric property of spark plasma sintering and common sintering. Among them, Figure 7-1 is a comparison diagram of relative permittivity, and Figure 7-2 is a comparison diagram of loss;

In the above drawings: F-frequency; ε'-relative permittivity; tanδ-loss.

Detailed ways

Taking the graphite mold as an example below, the present invention will be further introduced in conjunction with the accompanying drawings:

Embodiment one:

The preparation conditions are as follows: the sintering holding time is 5 minutes, the sintering temperature is 980 degrees Celsius, the sintering pressure is 51 MPa, the annealing temperature is 600 degrees Celsius, and the annealing holding time is 2 hours.

It can be seen from accompanying drawing 1 that after sintering for a short time, the obtained sample is very dense.

Embodiment two;

The preparation conditions are as follows: the sintering holding time is 5 minutes, the sintering pressure is 51 MPa, the annealing temperature is 600 degrees Celsius, the annealing holding time is 10 hours, but the sintering temperature is 800 degrees Celsius and the other is 980 degrees Celsius.

From attached drawings 2-1 and 2-2, it can be known that the relative dielectric constant of the corresponding ceramics at 10000Hz is: 3.0×10 ³ , the latter is 7.0×10 ³ , and the loss at this frequency is: 0.12, the latter is: 0.12;

Embodiment three:

The preparation conditions are as follows: the sintering temperature is 980 degrees Celsius, the sintering pressure is 51 MPa, the annealing temperature is 600 degrees Celsius, and the annealing holding time is 10 hours, but the sintering holding time is 5 minutes and the other is 60 minutes.

From attached drawings 3-1 and 3-2, it can be seen that the relative dielectric constant of the corresponding ceramics at 10000Hz is: 7.0×10 ³ , the latter is 2.0×10 ⁴ , and the loss at this frequency is: 0.10, the latter is: 0.18;

Embodiment four:

The preparation conditions are as follows: the sintering temperature is 980 degrees Celsius, the sintering holding time is 5 minutes, the annealing temperature is 600 degrees Celsius, the annealing holding time is 10 hours, but the sintering pressure is 20 MPa for one and 70 MPa for the other.

From attached drawings 4-1 and 4-2, it can be seen that the relative dielectric constant of the corresponding ceramics at 10000Hz is: 8.0×10 ³ , the latter is 8.0×10 ³ , and the loss at this frequency is: 0.09, the latter is: 0.09;

Embodiment five:

The preparation conditions are as follows: the sintering temperature is 980 degrees Celsius, the sintering holding time is 5 minutes, the sintering pressure is 51 MPa, and the annealing holding time is 10 hours, but one annealing temperature is 500 degrees Celsius and the other is 900 degrees Celsius.

From attached drawings 5-1 and 5-2, it can be seen that the relative permittivity of the corresponding ceramics at 10000Hz is 7.0×10 ² , the latter is 7.0×10 ⁴ , and the loss at this frequency is: 0.50, the latter is: 0.27;

Embodiment six:

The preparation conditions are as follows: the sintering temperature is 980 degrees Celsius, the sintering holding time is 5 minutes, the sintering pressure is 51 MPa, the annealing temperature is 600 degrees Celsius, and the annealing holding time is 2 hours and 10 hours.

It can be seen from attached drawings 6-1 and 6-2 that the relative dielectric constant of the corresponding ceramics at 10000Hz is 7×10 ² and 2×10 ⁴ at 10,000 Hz. The loss of the former at this frequency is: 0.07, the latter is 0.16.

Embodiment seven:

The preparation conditions of spark plasma sintering are as follows: sintering temperature is 980°C, sintering holding time is 5 minutes, sintering pressure is 51 MPa, annealing temperature is 600°C, annealing holding time is 2 hours, the general sintering preparation conditions are: sintering temperature Incubate at 1035°C for 3 hours. The power consumption of the former sintering method is about 12Kw.h, and the power consumption of the latter sintering method is about 58Kw.h.

From attached drawings 7-1 and 7-2, it can be seen that the relative permittivity of the corresponding ceramics at 10000 Hz is: 7.0×10 ³ , the latter is 7.0×10 ² , and the loss at this frequency is: 0.07 The latter is: 0.04. Therefore, compared with the sample obtained by ordinary sintering, the loss of the sample obtained by spark plasma sintering is relatively close, but the relative dielectric constant is 10 times larger than that of the ordinary sintered sample, and the power consumption is ordinary One-fifth of the power consumption of sintering.

Claims (5)

1. utilize discharge plasma sintering high-dielectric CaCu ₃Ti ₄O ₁₂The method of pottery, it is characterized in that: described method is made up of following step:

1) with pure CaCu ₃Ti ₄O ₁₂Pack into mould and this mould put between upper/lower electrode in the discharge plasma sintering chamber of powder;

2) close the sintering chamber, open vacuum pump, the sintering chamber is vacuumized;

3) to the pressurization that heats up of sintering chamber, add pressure when waiting to be warming up to 800-980 degree centigrade, be incubated 5-60 minute, furnace cooling and then, pass vacuum pump with the temperature decompression to the 20-70 MPa;

When 4) equitemperature drops to below 100 ℃, product is taken out in the sintering chamber.

2. the discharge plasma sintering high-dielectric CaCu that utilizes as claimed in claim 1 ₃Ti ₄O ₁₂The method of pottery is characterized in that: described pure CaCu ₃Ti ₄O ₁₂Powder utilizes sol-gel method to make.

3. the discharge plasma sintering high-dielectric CaCu that utilizes as claimed in claim 1 or 2 ₃Ti ₄O ₁₂The method of pottery is characterized in that: in described intensification pressure process, the pressure size should raise and progressively increasing with temperature, should only add a little pressure when low temperature; In above-mentioned furnace cooling process, then pressure should be reduced to minimum.

4. the discharge plasma sintering high-dielectric CaCu that utilizes as claimed in claim 1 or 2 ₃Ti ₄O ₁₂The method of pottery, it is characterized in that: when described mould is graphite jig, the product that sinters is carried out 500-900 ℃ again in retort furnace, the anneal of insulation more than 2 hours, the part that decompose owing to carburizing on the products obtained therefrom surface, back of then will annealing again polishes off and polishes.

5. the discharge plasma sintering high-dielectric CaCu that utilizes as claimed in claim 3 ₃Ti ₄O ₁₂The method of pottery, it is characterized in that: when described mould is graphite jig, the product that sinters is carried out 500-900 ℃ again in retort furnace, insulation anneal more than 2 hours, the part that decompose owing to carburizing on the products obtained therefrom surface, back of then will annealing again polishes off and polishes.

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