JPH05262562A - Production of forsterite porcelain - Google Patents

Abstract

PURPOSE:To provide a process for producing a forsterite porcelain having low dielectric loss in microwave range. CONSTITUTION:A powdery raw material produced by mixing MgO with SiO2 at a molar ratio of 2:1 is calcined and crushed to obtain forsterite powder. The powder is mixed with a binder and compressionmolded and the obtained molded material is degreased and sintered to obtain a forsterite porcelain. In the above process, the amounts of impurities in the sintered forsterite porcelain are controlled to <=0.10% of Al2O3, <=0.05% of CaO, <=0.05% of Fe2O3, <=0.40% of ZrO2 and <=0.01% of the other impurities and the particle size distribution of the forsterite powder is adjusted to have an average particle diameter of <=3mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing forsterite porcelain, and more particularly to a method for obtaining forsterite porcelain having a low dielectric loss with respect to microwaves.

[0002]

2. Description of the Related Art Generally, one of the characteristics required for dielectric ceramics used in the microwave region is that the dielectric loss in the region is small. The dielectric loss represents the amount of energy lost as heat when an AC electric field is applied to the dielectric, and it is particularly important that the value is small at high frequencies. Forsterite is MgO and S
It is composed of a reaction product of iO ₂ , and originally has relatively excellent high frequency characteristics.

[0003]

However, when manufacturing forsterite porcelain, the raw materials MgO and Si are used.
Due to impurities mixed in O ₂ and elements added for various purposes, a phase other than forsterite is formed in the final product porcelain sinter, which has a problem of affecting electrical characteristics.

Therefore, the present inventor, in his research on forsterite, controls the impurities mixed in each step of obtaining the raw material (powder) and the forsterite porcelain and controlling the particle size of the forsterite powder.
We have found that the electrical characteristics of forsterite porcelain, especially the dielectric loss in the microwave region, can be reduced. The present invention is based on this finding.

That is, an object of the present invention is to provide a method for producing a forsterite porcelain having a small dielectric loss in the microwave region.

[0006]

In order to achieve the above-mentioned object, the present invention provides a forsterite powder by calcining and pulverizing a raw material powder prepared by mixing MgO and SiO ₂ in a molar ratio of 2: 1. A method of producing a forsterite porcelain by mixing the powder with a binder and press-molding to form a molded article, and degreasing and sintering the molded article,
In each step of obtaining the forsterite porcelain from the raw material powder, impurities contained in the porcelain sintered body of the forsterite porcelain are Al ₂ O ₃ 0.10% or less, CaO.
0.05% or less, Fe ₂ O ₃ 0.05% or less, ZrO
₂ 0.40% or less, other 0.01% or less, and the particle size distribution of the forsterite powder is set to an average particle size of 3 μm or less.

The calcination is, for example, 1000 to 120.
It is carried out at 0 ° C. for 2 to 4 hours. By calcination, a good single phase of almost forsterite is synthesized. 1000 ° C
Lower temperatures and higher than 1200 do not synthesize forsterite well. The calcination of the forsterite that has been calcined can be carried out, for example, with a ball mill using zirconia balls. This pulverization requires that the particle size distribution of the forsterite powder be 3 μm or less in average particle size.
If the particle size of the forsterite powder is large, the sinterability of the molded product of the forsterite powder deteriorates, and a high density sintered body cannot be obtained.

As a binder for forming a molded product, an organic paste such as polyvinyl alcohol or methyl cellulose is used. The molded product is formed into a predetermined shape according to the application by an appropriate pressure molding means. In the molded product, the organic compound such as the binder is sintered and removed in the degreasing process. The degreasing temperature is considered to be such that organic compounds are gradually burned out,
For example, it is 4 to 7 hours at 300 to 500 ° C. After degreasing, it is subsequently sintered. Sintering is performed at 1300 to 1600 ° C. for about 1 to 3 hours, preferably 1400 ° C. for 2 hours. If the sintering conditions are not satisfied, good porcelain electrical characteristics, particularly low dielectric loss against microwaves Can't get
The frequency number microwaves here hundred MH _Z ~ several hundred GH _Z, refers to the range of approximately 300MH _Z ~300GH _Z.

In the present invention, in the raw material powder, and in each step for obtaining the forsterite porcelain from the raw material powder, consideration is given so as to prevent impurities from entering the porcelain sintered body of the forsterite porcelain as much as possible. In addition to the adjustment of the raw material powder, materials and means in which impurities are not mixed are used in each processing step such as mixing, crushing and molding.

[0010]

The raw material powder is synthesized into forsterite by calcination, and the synthesized forsterite is pulverized into powder. When forsterite porcelain is manufactured, high-purity forsterite is synthesized by controlling the mixture of impurities that are mixed from raw material powder, etc., and the amount of impurities is controlled in each process of obtaining forsterite porcelain. As a result, a highly purified porcelain sintered body is obtained.

Further, forsterite powder has an average particle size of 3
By using a powder having a particle size distribution of μm or less, deterioration of sinterability due to elimination of a glass phase can be prevented, and densification can be performed at a sintering temperature almost equal to that in the past, to obtain a high-density porcelain sintered body.
Therefore, the crystal of the forsterite porcelain obtained in the present invention has a high purity in which the phases other than the forsterite phase are excluded and the glass phase at the grain boundaries is excluded.

[0012]

Next, an embodiment of the present invention will be described with reference to FIGS. First, high-purity MgO powder and SiO ₂ powder to be used as raw material powders are prepared. It is desirable that the particle size of the MgO powder and the SiO ₂ powder is small, but in this example, (average particle size 0.09 μm, (specific surface area 26.03 m ²
/ G) of MgO powder and a SiO ₂ powder having an average particle size of 0.82 and a (comparative area of 1.78 m ² / g). In addition,
The particle size of both powders may be such that they react sufficiently during calcination. I of MgO powder and SiO ₂ powder used in this example
The results of the contained impurities analyzed by CP analysis are shown in Table 1.

[0013]

[Table 1]

In Table 1, the numerical unit of the component amount is%, and the-mark indicates that the content is 0.001% or less.

Then, the molar ratio of MgO and SiO ₂ is 2: 1.
The MgO powder and the SiO ₂ powder were weighed so that the following was obtained, distilled water was added, and the mixture was mixed for 20 hours in a ball mill using urethane balls to obtain a mixture. The mixture is dried at about 100 ° C. for 24 hours to obtain a raw material powder. Next, the raw material powder is 1200 ° C for 3
It was calcined for a time to obtain a calcined product in which forsterite was synthesized. This calcined product was crushed for 24 hours in distilled water using zirconia balls and then dried at 100 ° C. for 24 hours to obtain forsterite powder (calcined powder).

The particle size distribution of this forsterite powder is as shown in FIG. In FIG. 2, the vertical scale on the right shows the scale of the bar graph, and the vertical scale (%) on the left shows the scale of the line graph. As shown in the graph of FIG. 2, 50% of this forsterite powder had a particle size of 1 μm or less.

Thus, 1% of polyvinyl alcohol was added as a binder to the forsterite powder thus prepared,
After mixing, it was formed into a cylindrical shape. Molding is first 300k
Uniaxial molding (temporary molding) of g / cm ² and then 3000 k
CIP molding (main molding) was performed at g / cm ² to obtain a molded product.
Next, the molded product was placed in a heating furnace, heated at 400 ° C. for 6 hours to degrease, then heated and fired at 1400 ° C. for 2 hours to obtain a cylindrical forsterite porcelain. The forsterite porcelain of this example produced in the above steps had good sinterability.

The bulk density and dielectric properties (dielectric constant ε and dielectric loss tan δ) of the forsterite porcelains a and b produced in this example are shown in Table 2.

[0019]

[Table 2]

Conventional forsterite porcelain c
In the production process, the grain size distribution of the forsterite powder is not taken into consideration in the production process, and the content of impurities in the porcelain sintered body is Al ₂ O ₃ 0.10%, CaO 0.05%, F
e ₂ O ₃ 0.05%, ZrO ₂ 0.04%, at least one. Then, the dielectric constant ε and the dielectric loss tanδ at Table 2 is a value measured at both short-circuited dielectric rod resonator method, the present embodiment forsterite porcelain Lee, b is measured at 15.8～18.7GH _Z and, conventional forsterite porcelain Ha ~ ho 9.3~10.0GH _Z
It is when measured in. From Table 2, it was confirmed that the forsterite porcelains a and b of this example had a dielectric loss one order smaller than those of the conventional c, d, and e.

The resistivity (measured by the three-terminal method) of the forsterite porcelain of this example is shown in Table 3, and the coefficient of thermal expansion and the coefficient of expansion (temperature rise 10 ° C./min. Maximum temperature 800 ° C., standard alumina sample was used). Are shown in Table 4. The resistivity is measured by the three-terminal method, and the coefficient of thermal expansion and the coefficient of expansion are elevated by 1
0 ° C./min. The maximum temperature was 800 ° C., and measurement was performed using standard sample alumina. Each numerical value of this example in Tables 3 and 4 is the average value of the forsterite porcelains a and b, and the conventional value is the average value of the conventional porcelain c, d and e.

[0022]

[Table 3]

[0023]

[Table 4] From the values in Tables 3 and 4, it is recognized that the forsterite porcelain of this example has a resistivity, a coefficient of thermal expansion, and a coefficient of expansion that are substantially the same as those of conventional forsterite porcelain. Therefore, it can be said that the forsterite porcelain obtained by this example is preferable as an insulating material for microwaves.

[0024]

According to the present invention, the impurities contained in the porcelain sintered body of the forsterite porcelain in the raw powder and the steps of obtaining the forsterite porcelain from the raw powder are
l ₂ O ₃ 0.10% or less, CaO 0.05% or less,
Fe ₂ O ₃ 0.05% or less, ZrO ₂ 0.40% or less, and other 0.01% or less, and
Since the particle size distribution of the powder of forsterite is set to have an average particle size of 3 μm or less, the dielectric loss in the microwave region is small, and a forsterite porcelain preferable as an insulating material for microwaves can be obtained. That is, according to the present invention, while highly pure forsterite powder is obtained,
Since the mixing of impurities is controlled from each step of manufacturing porcelain, it is possible to obtain porcelain with few impurities, and because the particle size distribution of forsterite powder is set to an average particle size of 3 μm or less, densified and high-density physical properties are obtained. It is possible to obtain a forsterite porcelain with a low dielectric loss.

[Brief description of drawings]

FIG. 1 is a process diagram for obtaining a forsterite porcelain according to an embodiment of the present invention.

FIG. 2 is a graph showing the particle size distribution of the forsterite powder of this example.

Claims (1)

[Claims] 1. A molded product obtained by calcining a raw material powder in which MgO and SiO ₂ are mixed at a molar ratio of 2: 1 and pulverizing the powder into forsterite powder, mixing the powder with a binder and pressurizing the powder. A method for producing a forsterite porcelain by degreasing and sintering the molded product, comprising the step of obtaining the raw material powder and the step of obtaining the forsterite porcelain from the raw material powder. Impurity contained in the body is Al ₂ O ₃ 0.10%
Below, CaO 0.05% or less, Fe ₂ O ₃ 0.05
% Or less, ZrO ₂ 0.40% or less, other 0.01
% Or less, and the particle size distribution of the forsterite powder is 3 μm in average particle size.
A method for producing a forsterite porcelain, characterized by: