JPH06279101A - Production of cordierite ceramics - Google Patents

Abstract

PURPOSE:To provide a method for producing low-cost cordierite ceramics having a low relative dielectric constant and a homogeneous dense compsn. in atomic or molecular order by a sol-gel process at a relatively low temp. CONSTITUTION:Magnesium and aluminum compds. as inorg. or org. salts and org. silicon alkoxide are used as starting materials and added to an alcoholic solvent to prepare a sol and this sol is dried and fired at <=1,200 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordierite ceramics used as a substrate material such as a silicon wafer having a small relative permittivity and a coefficient of linear expansion close to that of silicon with the high integration of electronic devices. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, cordierite ceramics have a very small coefficient of linear expansion (1.5 × 10 ^-6 k ^-1 , 25 to 800).
Therefore, it has been used as a catalyst carrier for purifying exhaust gas of internal combustion engines such as automobiles.

Recently, however, the relative permittivity has become smaller and the alumina (9.7 at 1 MH) has become smaller due to the higher integration of electronic equipment.
z), which is smaller than (5.0 at 1 MHz) and has a coefficient of linear expansion close to that of silicon (3.5 × 10 ⁻⁶ k ⁻¹ , 25 to 100 ° C.). Therefore, alumina (8.1 × 10 ^-6 k) which has been used as a substrate material has been used.
^The above-mentioned cordierite ceramics have been attracting attention as a substrate material for silicon wafers, etc. as an alternative material.

However, as a method for producing cordierite ceramics, a method has been adopted in which raw materials for each oxide are melted, then rapidly cooled, glass is produced, and then crystals are precipitated. In this case, in order to produce a dense sintered body, a method of adding a sintering aid to widen the sintering temperature range is adopted.

However, the addition of this sintering aid causes the formation of crystals other than cordierite, which lowers the heat resistance and the coefficient of thermal expansion, thereby deteriorating the original characteristics.

On the other hand, when the sol-gel method is used, the hydrolysis rate of each metal alkoxide used as a starting material is generally different. For this reason, a partial hydrolysis method is used or an organic compound having a multidentate ability is used. By adding a solvent,
Attempts have been made to alleviate the difference in hydrolysis rate and improve the homogeneity on the atomic or molecular order. However, there are many problems such that the synthesis method becomes complicated, the metal alkoxide is very expensive, and the reactivity is high, which makes it difficult to handle.

[0007]

According to the present invention, as described above, the raw materials are melted and then rapidly cooled to precipitate crystals from the glass.
Since sintering is performed by adding a sintering aid, the heat resistance is lowered, the characteristics such as an increase in the coefficient of thermal expansion are deteriorated, while the sol-gel method using a metal alkoxide raw material is expensive,
There is a problem that it is difficult to handle because the hydrolysis rate and other factors are different, and the synthesis method is very complicated.

The inventors of the present invention have made extensive studies in order to solve such conventional problems. As a starting material, magnesium nitrate, magnesium acetate, aluminum chloride, aluminum nitrate, tetraethoxysilane are used as raw materials. Then, it is dissolved in an alcohol solvent to prepare a sol solution, which is dried and calcined, and there is no need to consider the difference in hydrolysis rate, and the synthesis method is very easy to obtain cordierite ceramics. I found that I could be.

The present invention has been made on the basis of the above findings, and is relatively inexpensive at a relatively low temperature by the sol-gel method, has a small relative dielectric constant, is homogeneous in the order of atoms or molecules, and has a dense composition at a low cost. , An object of the present invention is to provide a method for producing cordierite ceramics.

[0010]

The method for producing cordierite ceramics according to the present invention is to prepare a sol solution by using an inorganic or organic salt of magnesium, an aluminum compound and an organic silicon alkoxide as raw materials and using an alcohol solvent. This is characterized by being dried and then baked at a temperature of 1200 ° C. or lower.

The composition of the cordierite of the present invention is Mg
It is represented by ₂ Al ₄ Si ₅ O ₁₈ .

As the raw material of the magnesium compound, either magnesium nitrate or magnesium acetate is used. As the raw material of the aluminum compound, either aluminum chloride or aluminum nitrate is used, and as the organic tetraethohashisilane or trimethoxysilane raw material. , Silicon tetraethoxide, and silicon ethoxide are used.

As the alcohol solvent, methanol,
Ethanol, propanol, ethylene glycol, diethylene glycol, triethylene glycol, etc. are used. These raw materials become a sol solution and are gelled by the alcohol solvent.

The first method of producing cordierite ceramics from this sol solution is to slowly dry the sol solution (for example, after leaving it at room temperature) for gelation, and after drying the obtained gel compact, it is pulverized. Then, fine powder is prepared, and this is molded by hot pressing or the like and fired at a temperature of 1200 ° C or lower, preferably 1100 to 1200 ° C.

In the second method, the sol solution is sprayed by a thermal decomposition method such as a spraying method or an ultrasonic spraying method into a furnace at a high temperature to prepare fine powder, which is molded by a press or the like, and the temperature is 1200 ° C. Hereinafter, it is preferably fired at a temperature of 1100 to 1200 ° C.

The third method is to form a film on a substrate by a method such as a dip coating method, a spin coating method, an ultrasonic coating method, etc. The film is formed and then gelled. The sol solution is also sol-ized by drying. In this way, after forming a gel film on the substrate by various coating methods, dried and 1200 ℃ or less, preferably 1100 ~ 1200
Bake at a temperature of ° C.

As the substrate, quartz glass, alumina, stabilized zirconia or the like is used. This method can be used with any size and shape.

[0018]

[Function] Either magnesium nitrate, magnesium acetate, aluminum chloride, aluminum nitrate,
And tetraethoxysilane as a raw material, dissolved in an alcohol solvent to prepare a sol solution, which is dried,
By firing, a sintered body having a relatively low dielectric constant and a homogeneous and dense composition on the atomic or molecular order is obtained at a relatively low temperature.

[0019]

EXAMPLES Examples of the present invention will be described below.

Example 1 FIG. 1 is a flow sheet showing an example of the process for producing cordierite ceramics of the present invention.

11.42 g of aluminum nitrate nonahydrate and 3.25 g of magnesium acetate tetrahydrate were weighed and placed in a polybeaker, and then a mixed solvent of ethanol 42.07 ml and ethylene glycol 2.1 ml was added and stirred for 2 hours. After doing
Add 8.83 ml of tetraethoxysilane and stir for 2 hours to obtain a sol solution.

After drying this sol solution at about 100 ° C.,
After calcination at 700 ° C for 3 hours, pulverize to obtain powder. The obtained powder was compacted by hot pressing or the like, and the compact was fired at 1150 ° C. for 3 hours to obtain a cordierite ceramics sintered compact.

The obtained cordierite ceramics sintered body was evaluated, and the relative densities and the dependences of the densities on the calcination temperature and the main calcination temperature are shown in FIG. The heat treatment time was 3 hours. As a result, the calcination temperature is 700
When the temperature was ℃ and the main firing temperature was 1200 ℃, the relative density was about 95%, and the sintered body with the best sinterability was obtained. Under these firing conditions, no significant change was observed in the sinterability even when the main firing time was changed.

The measured values of the frequency dependence of the dielectric constant are shown in FIG. As a result, in the frequency range of 10 to 2000 KHz,
The relative permittivity was 5.0, which was almost constant. This value was about half the relative permittivity of 9.7 of the alumina substrate.

Example 2 A sol solution is obtained in the same manner as in Example 1.

This sol solution is sprayed by a spraying method in a furnace at a high temperature to prepare fine powder, which is calcined at 700 ° C. for 3 hours and then molded by hot pressing to obtain a compact. Was fired at 1200 ° C. for 3 hours to obtain cordierite ceramics.

When the same evaluation as in Example 1 was performed on the obtained cordierite ceramics sintered body, the same results as in Example 1 were obtained.

Example 3 A sol solution is obtained in the same manner as in Example 1.

After forming a film of this sol solution on a quartz glass substrate by a dip coating method, it is left at room temperature to dry, and this is calcined at about 700 ° C. for 3 hours, and then 11
Main firing was performed at a temperature of 00 ° C. for 3 hours to obtain a cordierite ceramic thin film.

When the same evaluation as in Example 1 was performed on the obtained cordierite ceramic thin film, the same results as in Example 1 were obtained.

[0031]

As described in detail above, according to the sol-gel method of the present invention, it is preferable to use a sintering aid or the like whose characteristics are deteriorated at a relatively low temperature of 1200 ° C. or lower, preferably 1100 to 1200 ° C. In addition, a sintered body or a thin film can be obtained, the characteristics are improved as compared with the conventional powder firing method, and the cost is low and the degree of freedom of the shape is large.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of a cordierite ceramics manufacturing process of the present invention.

FIG. 2 is a diagram showing the relative density of the sintered body obtained in Example 1 of the present invention, and the dependency of the density on the calcination temperature and the calcination temperature.

FIG. 3 is a diagram showing the frequency dependence of the dielectric constant of the sintered body obtained in Example 1 of the present invention.

Claims (1)

[Claims] 1. A sol solution is prepared from an inorganic or organic salt of magnesium, an aluminum compound and an organic silicon alkoxide as a raw material using an alcohol solvent, which is dried and then calcined at a temperature of 1200 ° C. or lower. A method for producing a characteristic cordierite ceramic.