JPH05345662A - Production of forsterite ceramic - Google Patents

Abstract

PURPOSE:To provide a process for producing a forsterite ceramic having low dielectric loss in microwave region by using a sintering temperature of 1300-1350 deg.C which is comparable to the sintering temperature of conventional process. CONSTITUTION:A raw material powder obtained 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 TiO2 powder and press-formed to obtain a formed product. A forsterite ceramic is produced by degreasing and sintering the formed product. In each step to produce the raw material powder and to produce the forsterite ceramic from the raw material powder, the impurities contained in the sintered forsterite ceramic are controlled to be <=0.10% Al2O3, <=0.5% CaO, <=0.05% Fe2O3, <=0.40% ZrO2 and <=0.01% other impurities, the average particle diameter of the forsterite powder is adjusted to <=3mum and the amount of TiO2 mixed to the forsterite powder is controlled to <=10%.

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 an improved 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. Further, although the conventional sintering temperature for obtaining a forsterite porcelain is about 1300 ° C., it is desired that the sintering temperature is not high even when obtaining a forsterite porcelain having a lower dielectric loss than the conventional one.

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. In addition, the present inventor has found in the study of forsterite that by adding TiO ₂ to the raw material of forsterite, it is possible to lower the sintering temperature without impairing the low dielectric loss and to adjust the dielectric constant. It was The present invention was made based on this finding.

That is, an object of the present invention is to provide a method for producing a forsterite porcelain which has a small dielectric loss in the microwave region of 10 ⁻⁴ or less and a dielectric constant of about 8. Another object of the present invention is to provide a method for producing a forsterite porcelain having a sintering temperature equivalent to that of the conventional one of 1300 ° C. and a dielectric loss of a small value of about 7.0 × 10 ^−5. Especially.

[0006]

In order to achieve the above object, the invention of claim 1 uses MgO and SiO ₂ in a ratio of 2: 1.
The raw material powders mixed in a molar ratio of calcination are calcined and crushed into forsterite powder, and the binder and Ti are added to the powder.
A method for producing a forsterite porcelain by mixing O ₂ powder and press-molding to form a molded article, and degreasing and sintering the molded article, comprising the raw material powder and the forsterite from the raw material powder. In each step of obtaining a porcelain, impurities contained in a porcelain sintered body of forsterite porcelain were Al ₂ O.
₃ 0.10% or less (meaning wt%, the following% s are also used in this sense), 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 controlling the particle size distribution of the forsterite powder to an average particle size of 3 μm or less, and TiO ₂ is mixed in an amount of 10% or less.

The invention of claim ₂ is characterized in that TiO ₂ is mixed in an amount of 5% or less in claim 1.

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 ° C do not synthesize forsterite well. The calcined forsterite can be pulverized by, for example, a ball mill using urethane balls. In the step of pulverization, TiO ₂ powder and binder are added, and pulverization and mixing of each powder are performed simultaneously. As the binder, an organic paste such as polyvinyl alcohol or methyl cellulose is used, and the amount necessary for molding is added. The amount of TiO ₂ powder added is in the range of 0.5 to 10% with respect to the forsterite powder. In this range, the sintering temperature can be set to 1300 ° C. while maintaining the dielectric loss at a value of around 7.0 × 10 ⁻⁵ . Further, when the amount of TiO ₂ added is 0.5 to about 5%, the dielectric constant can be adjusted to about 8 while the dielectric loss is suppressed to 10 ⁻⁴ or less. The crushing is mainly performed so that the particle size distribution of the forsterite powder and the TiO ₂ powder is set to an average particle size of 3 μm or less. Forsterite powder and Ti
If the particle size of the O ₂ powder is large, the sinterability of the molded product made of forsterite powder deteriorates, and a high-density sintered body cannot be obtained. In the crushing process, each powder is mixed.

[0009] The above-mentioned molded product is formed by an appropriate pressure molding means.
It has a predetermined shape according to the application. In the molded product, the organic compound such as the binder is sintered and removed in the degreasing process. The degreasing temperature is set to such a degree that the organic compound is burnt out for removal, and is, for example, 300 to 500 ° C. for 4 to 7 hours.
After degreasing, it is subsequently sintered. Sintered 1300 to 1400
1 to 3 hours at ℃, preferably 1300 ℃, 2 hours,
Therefore, if the sintering conditions are not satisfied, good electrical characteristics of the porcelain, particularly low dielectric loss with respect to microwaves, cannot be obtained. In addition, the microwave here is frequency several hundred MH _Z
To hundreds of GH _Z, it refers to the range of approximately 300MH _Z ~300GH _Z.

In the present invention, the raw material powder and TiO ₂
In each step of obtaining the powder and the forsterite porcelain from them, it is taken into consideration that impurities will not enter the porcelain sintered body of the forsterite porcelain as much as possible. In addition to adjusting the raw material powder, materials and means that do not mix impurities are used in each processing step such as mixing with the TiO ₂ powder and the binder, crushing, and molding.

[0011]

The raw material powder is synthesized into forsterite by calcination, and the synthesized forsterite is pulverized into powder. When producing forsterite porcelain, high-purity forsterite is synthesized by controlling the mixture of impurities from the raw material powder, TiO ₂ powder, etc., and the amount of impurities mixed in each step of obtaining forsterite porcelain is controlled. By controlling, a highly purified porcelain sinter can be obtained.

TiO ₂ mixed with the raw material powder has the function of lowering the sintering temperature of the molded product. Further, by making the forsterite powder into a powder having an average particle size of 3 μm or less, deterioration of sinterability due to elimination of the glass phase is prevented, and densification is performed at a sintering temperature equivalent to that of the prior art, and high density porcelain It can be made into a 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.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to FIGS.
Will be described. First, high-purity MgO powder and SiO ₂ powder for use as raw material powder, and Ti as an additive
Prepare O ₂ powder. It is desirable that the particle size of the MgO powder and the SiO ₂ powder is small, but in this example, the average particle size is 0.09.
μm, MgO powder having a (specific surface area of 26.03 m ² / g),
And average particle size 0.82, (specific surface area 1.78 m ² / g)
SiO ₂ powder was used. Incidentally, MgO powder and SiO
₂ The particle size of the powder may be such that it reacts sufficiently during calcination. I of MgO powder and SiO ₂ powder used in this example
Table 1 shows the analysis results of the contained impurities by CP emission spectroscopy. Although it is desirable that the TiO ₂ powder has a fine grain size, in this example, a rutile type crystal powder having an average grain size of 0.68 μm was used. The results of analysis of the impurities contained in the TiO ₂ powder 1CP analysis of this example are shown in Table 2.

[0014]

[Table 1]

[0015]

[Table 2]

In Tables 1 and 2, the numerical unit of the component amount is%, and the-mark indicates that the content is 0.001% or less.

Next, the forsterite porcelain of this example is manufactured according to the steps shown in FIG. MgO and SiO
MgO powder and SiO ₂ powder were weighed so that the molar ratio of ₂ was 2: 1, distilled water was added, and urethane balls were mixed for 20 hours in a ball mill to obtain a mixture. Mixture is about 10
Dry at 0 ° C. for 24 hours to obtain a raw material powder. Then, the raw material powder was calcined at 1200 ° C. for 3 hours to obtain a calcined product in which forsterite was synthesized. This calcined product was put into a ball meal together with TiO ₂ powder and a binder, and pulverized and mixed.

That is, the addition amount of polyvinyl alcohol (binder) was 1.0% with respect to the calcined product, and TiO 2 was added.
The samples of each section were prepared with no addition of the _two powders and an addition amount of 0.5 to 30.0%. Then, the ward no addition of TiO ₂ powder C, and TiO ₂ powder 0.5% addition group S
1, TiO ₂ powder 1.0% addition section is S2, TiO ₂ powder 2.0% addition section is S3, TiO ₂ powder 5.0% addition section is S4, TiO ₂ powder 10.0% addition section is S5, TiO ₂
Powder 30.0% addition group as S6, no addition group and addition group 6
Samples of a total of 7 zones were prepared. In addition, each sample of these 7 sections was similarly processed according to the process after "crushing and mixing" of FIG. Grinding and mixing is performed by using a ZrO ₂ ball for 24 hours, and then dried at 100 ° C. for 24 hours, and then T
Each forsterite powder (calcined powder) was prepared by mixing iO ₂ and a binder.

The particle size distribution of the TiO ₂ powder 2.0% addition area S3 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 the powder in the addition zone S3 had a particle size of 1 μm or less.

After the mixing treatment, the powders of each addition section C and S1 to S6 were formed into a cylindrical shape in each section. Molding is first 30
Uniaxial molding (temporary molding) of 0 kg / cm ² and then 300
CIP molding (main molding) was performed at 0 kg / cm ² to obtain a molded product. Next, each molded product is placed in a heating furnace, heated at 400 ° C. for 6 hours to degrease, then heated and baked at 1400 ° C. for 2 hours to give a cylindrical shape corresponding to each addition section C and S1 to S6. Each forsterite porcelain C and S1 to S6 were obtained. The sinterability of each of the forsterite porcelains C and S1 to S6 was good.

Each of the forsterite porcelains C and S1
Bulk density and dielectric properties of S6 (dielectric constant ε and dielectric loss t
an δ) is as shown in Table 3.

[0022]

[Table 3]

Conventional forsterite porcelain a, b and c are
In the manufacturing process, the particle size distribution of the forsterite powder is not taken into consideration, and the content of impurities in the porcelain sintered body is A
l ₂ O ₃ 0.10%, CaO 0.05%, Fe ₂ O
₃ 0.05%, ZrO ₂ 0.04%, at least one. Then, the dielectric constant ε and the dielectric loss tan δ in Table 3 are values measured by the both-end short-circuit type dielectric cylinder resonator method, and are the forsterite porcelain C _,
S1~S6 was measured at 15.8～18.7GH _Z, conventional forsterite porcelain Lee, b, c are 9.3~10.0G
This is when measured by H _Z. From Table 3, it was confirmed that the forsterite porcelains S1 to S6 of this example had a dielectric loss of one order smaller than the conventional a, b, and c. Further, it was confirmed that the forsterite porcelains S1 to S6 of this example had a bulk density higher than that of the forsterite porcelain C.

The resistivities of the forsterite porcelains S1 to S6 (measured by the three-terminal method), the coefficient of thermal expansion and the coefficient of expansion (temperature increase of 10 ° C./min, maximum temperature of 800 ° C., using standard sample alumina) are as follows. Both were almost equivalent to the conventional commercially available forsterite porcelain. Therefore, each of the forsterite porcelains S1 to S6 of this example is preferable as an insulating material for microwaves.

Next, a second embodiment of the present invention will be described.
In the first embodiment described above, a large number of samples of the addition sections C, S1 to S6 were prepared, and the molded articles were made into 1200, 1250, 1300, 1350, 140 according to the process procedure of FIG.
By firing for 2 hours at each temperature of 0,1450 and 1500 ° C., cylindrical forsterite porcelains C and S1 to S6 corresponding to the addition zones C and S1 to S6 were manufactured. Then, the bulk densities of the manufactured forsterite porcelains C and S1 to S6 were measured, and the relationship between each sintering temperature and the bulk density was investigated. The result was as shown in FIG. The graph T in FIG. 3 shows the case where forsterite porcelain is obtained from commercially available forsterite. In FIG. 3, S
The bulk density of the graphs of 1, S2 and S3 is that the sintering temperature is 130
Since it is almost the same at 0 ° C and 1400 ° C, T
It is recognized that the sintering temperature can be lowered to about 100 ° C. when the added amount of iO ₂ is 0.5 to 2.0%. Also, T
From about 5% addition of iO ₂ (see graph of S4), increase in density of dense body due to addition of TiO ₂ having higher density than forsterite (rutile type density ρ = 4.24 g / cm ³ ). Be done. However, when TiO ₂ is added in an amount of 5% or more (see graphs of S5 and S6), 130
The densification did not occur at 0 ° C, and the sintering temperature increased by about 50 ° C.

Next, the dielectric constant and dielectric loss of each of the forsterite porcelains C and S1 to S6 manufactured in this example were measured, and the relationship between the added amount of TiO ₂ and the dielectric constant and dielectric loss was investigated. As a result, the relationship between the added amount of TiO ₂ and the dielectric constant is as shown by the graph G in FIG. 4, and the relationship between the added amount of TiO ₂ and the dielectric loss is as shown by the triangle mark in FIG. In addition,
4 and 5, T represents the value of a commercially available forsterite porcelain, and C represents the value of a TiO ₂ -free forsterite porcelain. In FIG. 4, it was found that the addition of TiO ₂ having a higher dielectric constant than that of forsterite increases the dielectric constant of the forsterite porcelain in proportion to the addition amount of TiO ₂ . In FIG. 5, the dielectric loss gradually increased up to the addition amount of 10%, but a sharp increase was observed between 10% and 30%.

That is, according to this example, (a) TiO ₂ was added in an amount of 10% or less to adjust the dielectric constant to about 8 while suppressing the dielectric loss to 10 ^-4 or less. What you can do. (B) It was confirmed that the sintering temperature can be lowered by about 100 ° C. while maintaining the dielectric loss at a value of around 7.0 × 10 ⁻⁵ by adding 5.0% or less of TiO ₂ .

[0028]

According to the invention of claim 1, in each step of obtaining the raw material powder and 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 controlling the particle size distribution of forsterite powder to an average particle size of 3 μm or less, and mixing TiO ₂ in an amount of 10% or less. Therefore, 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 invention of claim 1, while obtaining a high-purity forsterite powder, it is possible to obtain a porcelain with a small amount of impurities because the mixing of impurities is controlled from each step of manufacturing a porcelain, and the forsterite powder is also obtained. Since the average particle size distribution of 3 is not more than 3 μm, it is possible to achieve a dense and high-density physical property and to mix TiO ₂ in an amount of 10% or less. The dielectric constant can be set to about 8 while being suppressed to 10 ⁻⁴ or less. In the invention of claim 2, since the amount of TiO ₂ added is 5% or less, the dielectric loss remains at a value of, for example, 7.0 × 10 ⁻⁵ , and the sintering temperature is about 1300 ° C. as in the conventional case. Can be obtained in degrees.

[Brief description of drawings]

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

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

FIG. 3 is a graph showing the sinterability of forsterite porcelain to which TiO ₂ is added.

FIG. 4 is a graph showing the dielectric constant of forsterite porcelain to which TiO ₂ is added.

FIG. 5 is a graph showing the dielectric loss of forsterite porcelain to which TiO ₂ is added.

Claims (2)

[Claims] 1. A raw material powder in which MgO and SiO ₂ are mixed at a molar ratio of 2: 1 is calcined and crushed into forsterite powder, and a binder and TiO ₂ powder are mixed and pressed. A method of forming a molded product into a molded product, degreasing and sintering the molded product to produce a forsterite porcelain, comprising the steps of obtaining the raw powder and the forsterite porcelain from the raw powder in each step. Impurity contained in porcelain porcelain sintered body was 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.
m or less, and mixing the TiO ₂ in an amount of 10% or less, a method for producing a forsterite porcelain. 2. A method for producing a forsterite porcelain according to claim 1, wherein TiO ₂ is mixed in an amount of 5% or less.