JPS6272554A - Manufacture of fine polycrystal al2o3 sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] Book 3? iSJ relates to a method for producing dense polycrystalline Al2O3 sintered bodies, and in detail, it is a method for producing dense polycrystalline Al2O3 sintered bodies, which are suitable as base materials for high-temperature viewing windows, infrared transmission windows, chemical engineering viewing windows, high-pressure sodium discharge lamps, etc. The present invention relates to a method for producing a polycrystalline Al2O3 sintered body.

[Prior Art] In recent years, attempts have been made to make various high-melting point oxide sintered bodies transparent as heat-resistant transparent materials, and A n 2O3 sintered bodies have been developed as a type of such translucent ceramics. There is. This light-transmitting AR2O3 sintered body is a hexagonal sintered body, and its in-line transmittance is about 60%.

By the way, in order to make ceramics into a translucent body, it is necessary to heat the ceramics with l+ kIII and two-tsubaki zeta, so methods for manufacturing translucent ceramics include high-temperature sintering and sintering aids (hereinafter referred to as sintering aids). For example, as a method for producing translucent Al 2O3, a method using a super-pressure sintering method (sometimes simply referred to as an auxiliary agent) or a superpressure sintering method uses Sinter at high temperature or
Alternatively, as shown in Fig. 1, 0.2 to 0.6% by weight of auxiliary powder such as MgO is added and mixed to the raw material powder, calcined, crushed, molded, processed as necessary, and then heated in an H2 furnace. Alternatively, it is produced by calcination in a vacuum furnace, followed by main firing at 1700 to 1900°C for 5 to 20 hours.

[Problems to be solved by the invention] In this way, wk having translucency can be produced without using a sintering aid.
When producing a sintered body of A fL2O3, firing at a high temperature was required, which was industrially disadvantageous.

Further, by using a sintering aid, the firing temperature can be lowered, but in this case, there is a problem in mixing the raw material powder and the aid powder. That is, these powders are
Usually, it has a fine particle size of about 0.5 to Ig, m,
Moreover, since the amount of the auxiliary powder added is very small, it is extremely difficult to uniformly mix the raw material powder and the auxiliary powder. Moreover, since the contact area with each other is extremely small, the effect of adding the auxiliary agent may not be fully exhibited.

Note that under super-pressure of about 1000-1100 Kg/crn', it is possible to obtain a dense sintered body by firing at a low temperature of about 1300°C.
In this case, superpressurizing equipment is required, which causes problems such as increased equipment size and complicated maintenance management, and has the disadvantage of increasing manufacturing costs.

[Means for Solving the Problems] As a result of various studies in order to solve the problems of the above-mentioned conventional methods, the present inventors focused on ultrafine particles produced by the alkoxide method, and applied the alkoxide method to high-purity Al2O3. It was discovered that a dense polycrystalline Al 2O3 sintered body could be easily produced at low temperature and in a short time by adding and mixing Al 2O3 and MgO produced in ultrafine powder particles as an auxiliary agent. Completed the invention.

That is, the present invention.

Obtained by alkoxide method using high purity Al2Oz raw material. 1 [Method for producing a dense polycrystalline Al2O3 sintered body, which comprises mixing particles Al2Oz and MgO, molding the mixture, and then firing it in a vacuum or C±hydrogen atmosphere. This is a summary.

A detailed description of the invention will be given below.

In the present invention, as the Al2O3 raw material, high purity Al
2O3 is used. As the high-purity Al2Ox raw material, a high-purity product with a purity of 99.996 or higher is preferable.

As one of such high-purity Al 2O3 raw materials, Al
For example, 2Oz is the product obtained by hydrolyzing a solution of the main fluorine as a raw material and calcining the resulting precipitate at, for example, about 400 to 800'CF.

In the present invention, the Al 2 O 3 Ll material is preferably a powder having an average particle size of about 0.2 to 1.0 gm, particularly about 0.5 pm.

In addition, in the present invention, the ultrafine particles Al2O3 and MgO obtained by the alkoxide method used as sintering aids are obtained by crushing and calcining powders obtained by hydrolyzing An and Mg alkoxides as necessary. things are used. In this case, as the raw material An and Mg alkoxide, An and Mg methoxide, ethoxide, impropoxide, butoxide, etc. are used. The alkoxide used preferably has a low impurity content. These alkoxides may be dissolved and mixed in an organic solvent such as benzene, toluene, xylene or alcohol and subjected to hydrolysis.

The ultrafine particles A l 2O :I and MgO have a particle size l
Ultrafine particles of 0 to 100 OA are preferable, and Al2O
The weight ratio of 3 and MgO is Al2O3:Mg0=9
: It is preferable to set it as 1-4:6.

In the present invention, first, A! ; Add A to L2O-4 raw material
An auxiliary agent consisting of iL 2 O 3 and MgO is added and mixed in a wet or dry manner. The amounts of Al2O3 and MgO added are A
The amount is preferably 0.15 to 10% by weight based on the fL2O3 raw material.

The obtained mixture is molded by a molding method such as pressure molding, but in the case of pressure molding, the molding pressure is 700 to 1500 kg.
/crn' is preferable.

This molded body is then fired in a vacuum or hydrogen atmosphere. This firing is preferably carried out at 1,600 to 1,800 °C for about 3 to 10 hours, especially at 1,600 to 1,700 °C for about 5 to 10 hours. It is also preferable to perform calcination prior to this firing. 1 at 12O0℃
It is preferable to carry out the treatment for about 3 hours. This calcination is also preferably carried out in vacuum or in a hydrogen atmosphere, but other atmospheres may be used.

Polycrystalline Al obtained by such a method of the present invention
The 2O3 sintered body is extremely dense and has excellent translucency.

[Function] Generally, the powder obtained by the alkoxide method or the alkoxide coprecipitation method has a small particle size, an active surface, and high purity.

Therefore, according to the present invention, high-purity 1, for example, a raw material A l 2O obtained by calcining a precipitate obtained by an alkoxide method.
y, ultrafine particles Al2 obtained by the alkoxide method
By adding and mixing O3 and MgO, Al2O
Since the ultrafine powder A 1 2 O 3 and MgO are uniformly distributed between the particles of the three raw material powders, it is possible to obtain a uniform and dense sintered body at a low firing temperature.

Further, the process of the method of the present invention is as shown in route A in FIG. 1, and various operations in the middle of the conventional method can be omitted, making it easy to implement.

[Examples] The present invention will be explained in more detail by examples below.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 High purity Al2O3 (purity 99
．． 9% or more) and 95 parts by weight of Al2O3 and MgO fine powder particles (particle size lO~l) produced by the alkoxide method.
5 parts by weight of OOA, AlI303:Mg0=9:l (weight ratio)) were dry mixed in a pot mill. The obtained mixed powder was press-molded at 1000 Kg/Crrf, and this compact was calcined in a hydrogen furnace at 1000°C for 1 hour, and further heated for 16 hours.
Main firing was performed at 50° C. for 3 hours to obtain a sintered body.

When various physical property values of this sintered body were measured, they were as follows.

Density: 4.00Kg/c Bending strength
: 40. OKg/mrn'heat'#1 Impact: 26
0° C. quenching light transmittance: 96% From these results, it is clear that according to the present invention, an extremely dense Al2O3 sintered body having high translucency and excellent mechanical properties can be easily obtained in a short time.

[Effects of the Invention] The method for producing a sintered body includes adding Al 2O3 and M obtained by an alkoxide method to a high-purity A fL2O:l raw material.
Ultrafine particles of gO are added and mixed, and the resulting mixture is molded and fired.Since the Al2O3 and Mg0M fine particles act well as sintering aids, very dense sintering can be achieved in a short time at low temperature. You can get a solid body. Therefore, the polycrystalline Al2O3 sintered body produced by the present invention has high translucency, mechanical properties such as strength and thermal shock resistance, and
It also has excellent chemical stability and is extremely useful industrially as a base material for high-temperature viewing windows, infrared transmission windows, chemical engineering viewing windows, high-pressure sodium discharge lamps, etc.

[Brief explanation of drawings]

51 is an explanatory diagram of the conventional manufacturing process of translucent ceramics.

Claims (4)

[Claims] (1) A dense polycrystalline Al_2O_3 sintered body characterized by mixing ultrafine particles of Al_2O_3 and MgO obtained by an alkoxide method with a high-purity Al_2O_3 raw material, molding this mixture, and then firing it in a vacuum or hydrogen atmosphere. manufacturing method. (2) Ultrafine particles Al_2O for Al_2O_3 raw material
2. The method for producing a dense polycrystalline Al_2O_3 sintered body according to claim 1, wherein the amount of addition of _3 and MgO is 0.15 to 10% by weight. (3) Dense polycrystalline Al_2O_ according to claim 1 or 2, characterized in that the average particle size of the ultrafine particles Al_2O_3 and MgO is 10 to 1000 Å.
3. Method for manufacturing sintered body. (4) Ultrafine particles Al_2O_3 and MgO Al_2O
Dense polycrystalline Al_2O_3 sintered according to any one of claims 1 to 3, wherein the ratio of _3 and MgO is 9:1 to 4:6 (weight ratio). How the body is manufactured.