JPH02233552A - Production of transparent sintered compact of aluminum nitride oxide - 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] C. Industrial Application Field] This invention relates to a method for producing a transparent aluminum oxynitride sintered body. [Prior art] Aluminum oxynitride not only has excellent high-temperature strength and thermal shock resistance, but also has no optical anisotropy because it belongs to the cubic crystal system, and even in sintered polycrystalline materials, it can be used as a transparent body without light scattering. Obtainable. Therefore, in recent years, expectations have increased for it as a heat-resistant window material in the visible and infrared regions.

Conventionally, transparent aluminum oxynitride sintered bodies have been manufactured using aluminum oxide powder and aluminum nitride powder as starting materials through processes such as calcination, crushing, and firing. However, when applied to window materials, the transmittance could not be said to be sufficient. This is due to the difficulty of sintering of aluminum oxynitride, and it was difficult to make it sufficiently dense to impart translucency.

Therefore, JP-A-58-74577 and JP-A-60-1
As described in No. 27268, a method has been used to promote sinterability by adding a sintering aid when sintering aluminum oxynitride. Although this method is extremely effective in densifying difficult-to-sinter materials, in transparent materials, as the amount of sintering aid added increases, the second phase that causes light scattering becomes negligible. As the light disappears, the transmittance deteriorates. Therefore, it is necessary to suppress the amount of additives added as much as possible without sacrificing the densification of the sintered body, but even with the optimal conditions of this manufacturing method, the transmittance is sufficient for an optical material. However, it has not reached the point where it has.

[Problem to be solved by the invention]

In the conventional manufacturing method of transparent aluminum oxynitride sintered bodies, sinterability is improved by adding a sintering aid as described above.
Although densification is promoted, as the amount of the sintering aid added increases, a second phase is generated that causes light scattering, so there is a problem that the transmittance does not necessarily increase.

This invention was made to solve the above-mentioned problems, and it is a transparent aluminum oxynitride sintered body that can produce a high transmittance aluminum oxynitride sintered body even if no or only a small amount of sintering aid is added. The purpose of the present invention is to obtain a method for manufacturing a sintered aluminum oxynitride body.

[Means to solve the problem]

The present invention is a method for manufacturing a transparent aluminum oxynitride sintered body as follows: (1) 9 to 17.5% by weight of aluminum nitride powder is mixed with aluminum oxide powder and the mixture is fired at 1500 to 1750°C. An aluminum oxynitride sintered body containing reactive aluminum oxide and aluminum nitride, or only aluminum oxide is produced, and then this sintered body is ground into powder with an average particle size of 3.5 μm or less, and this powder is further heated with nitrogen. Medium 1750-1900℃ for 1-5 hours, LOO
A method for producing a transparent aluminum oxynitride sintered body by hot press sintering under a pressure of kgf/a or more. ...(1
(2) 9 to 17.5% by weight of aluminum nitride powder is mixed with aluminum oxide powder and fired at 1,500 to 1,750°C to eliminate unreacted aluminum oxide and aluminum nitride, or only aluminum oxide. An aluminum oxide nitride sintered body is produced, and then this sintered body is ground into a powder with an average grain size of 3.5 μm or less, and a compound containing yttrium is added to this powder in terms of yttrium oxide of 0.02~ Add 3% by weight and mix at 175% by weight in nitrogen.
A method for producing a transparent aluminum oxynitride sintered body by hot press sintering at 0-1900°C for 1-5 hours under a pressure of 100 kgf/aJ or more. (Manufacturing method ■) This invention will be specifically explained below. First, add 99% of aluminum nitride powder to high-purity aluminum oxide powder.
．． 0-17.5% by weight, preferably 11.5-16.0
Add % by weight and mix. This is γ-1 type aluminum oxynitride AI22.02. Compared to the molar ratio of 9:5 between AI2,0 and AI2N, aluminum oxide powder is mixed in excess. As a result of the reaction between aluminum oxide and aluminum nitride, aluminum oxynitride generates cation defects, resulting in improved sinterability.

The above mixed powder is calcined at 1500 to 1750°C in nitrogen. If the temperature is lower than this, aluminum oxide and aluminum nitride hardly react, and calcination is meaningless.

In addition, if the temperature is higher than 1750℃, the reaction will proceed completely and the activity as a raw material powder will be lost even if pulverized. Aluminum oxide and aluminum nitride, or only aluminum oxide, becomes aluminum oxynitride, and by crushing this sintered body, a highly active raw material powder can be produced. In order to accelerate the sintering rate, the average particle size of the particles is 3.5 μm or less, preferably 2.5 μm or less. In addition, in order to suppress abnormal grain growth, the proportion of particles with a grain size of 57j+++ or more is preferably 10% or less. In production method I, this pulverized powder is used as a raw material for hot press sintering, but in production method 2, a compound containing yttrium is added as a sintering aid to this pulverized powder in an amount of 0.02 to 3% by weight in terms of yttrium oxide. , preferably 0.
A trace amount of 02 to 1% by weight is added and mixed to form a hot press sintering raw material.

The raw material powder produced by this method was placed in a carbon die for hot press, and heated at 1750 to 1900°C in nitrogen.
Hot press sintering is carried out for 1 to 5 hours. The hot press is applied at a pressure of 100 kgf/cm 2 or more, preferably 200 kgf/aJ or more, which is necessary to remove and reduce pores and promote densification of the sintered body. The sintering temperature is 1
If the temperature is below 750°C, the sintering required for transparency will not take place sufficiently, and if it is above 1900°C, the reaction between the sintered body and the carbon die will be intense, resulting in a blackish sintered body, which is not preferable. ．． The sintered body manufactured by the above method becomes transparent and colorless by polishing the surface.

[For production]

Therefore, in the present invention, unreacted aluminum oxide and aluminum nitride or An aluminum oxynitride sintered body containing only aluminum is produced, and then this sintered body is ground into a powder with an average particle size of 3.5 μm or less. A raw material powder is prepared by adding 0.02 to 3% by weight of a compound containing yttrium in terms of yttrium oxide.
A transparent aluminum oxynitride sintered body can be produced by hot I-press sintering at ~1900° C. for 1 to 5 hours under pressure of 100 kgf/cm 2 or more.

〔Example〕

Examples of the present invention will be described below.

Example 1 85% by weight of aluminum oxide powder with a purity of 99.9% or higher
and 15% by weight of aluminum nitride powder with a purity of 97% or higher.
were placed in a polyethylene pot and mixed in ethanol using a ball mill using alumina balls with a purity of 99.5% or higher. After drying the mixed powder, the powder is molded using a mold press method and sintered at 1700°C in nitrogen for 2 hours. X-ray diffraction reveals that the sintered compact consists of aluminum oxynitride and aluminum oxide. The above sintered body is roughly pulverized using a stamp mill, and further pulverized for 48 hours or more using an alumina pole mill pot. The average particle size of the powder after pulverization is 2.5 μ- when measured using a centrifugal sedimentation type particle size distribution analyzer manufactured by Shimadzu Corporation. The powder is granulated, molded using a mold press method, and set in a carbon die for hot press. The molded body is made using an induction heating type hot press device. 18 in nitrogen under a pressure of 200 kgf/aJ
Hot press sintering was performed at 50°C for 3 hours.

Example 2 1% by weight of yttrium oxide powder was added to aluminum oxynitride powder containing unreacted aluminum oxide produced in the same manner as in Example 1, mixed in a ball mill, granulated and molded, and prepared for hot pressing. Set it on the carbon die. The molded body is heated using an induction heating type hot press device,
3 at 1850℃ in nitrogen under a pressure of 200kgf/1
Hot press sintering was performed for an hour.

Comparative Example 1 81.7% by weight of aluminum oxide powder with a purity of 99.9% or more and 18% by weight of aluminum nitride powder with a purity of 97% or more.
3% by weight was mixed in the same manner as in Examples 1 and 2. The mixed powder was molded using a mold press method and heated at 1800 °C in nitrogen.
Sinter at ℃ for 2 hours. X-ray diffraction reveals that the sintered compact is a single-phase aluminum oxynitride.

The above sintered body was pulverized and molded in the same manner as in Examples 1 and 2, and 185
Hot press sintering was performed at 0° C. for 3 hours.

Next, the sintered bodies obtained in Examples 1 and 2 and Comparative Example 1 were processed to a thickness of 21 liters, and both sides were polished with a 1 μm diamond paste. The transmittance was also measured using an infrared spectrophotometer manufactured by JASCO Corporation.

As a result, as shown in Fig. 1, the sample manufactured using the single-phase aluminum oxide powder of Comparative Example 1 has a maximum transmittance of about 40% at a wavelength of 4 μm, whereas that of Example 1 has a maximum transmittance of about 40%. As shown, in the sample using activated aluminum oxynitride powder containing unreacted aluminum oxide, the wavelength is 0.3 to 5.
More than 50% across the μ-wavelength range, and 80% at wavelengths of 3 to 4 μm.
% or more. Further, as in Example 2, the sample was manufactured using activated aluminum oxynitride powder containing unreacted aluminum oxide and a trace amount of yttrium oxide powder added as a sintering aid as a raw material powder. 3
Transmittance was 70-80% over ~4μ range, and there was little variation in transmittance depending on wavelength.

〔Effect of the invention〕

As described above, according to the present invention, unreacted aluminum oxide and aluminum nitride or An aluminum oxynitride sintered body containing only aluminum oxide is produced, and this sintered body is further ground into powder with an average particle size of 3.5 μm or less, and this is used as it is or with a compound containing yttrium as a sintering aid. A raw material powder is obtained by adding 0.02 to 3% by weight in terms of yttrium oxide, and this powder is hot press sintered in nitrogen at 1750 to 1900°C for 1 to 5 hours under a pressure of 100 kgf/cm2 or more. A transparent aluminum oxynitride sintered body can be manufactured by this method.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the straight transmittance of light in Examples and Comparative Examples.

Claims (2)

[Claims] (1) By mixing 9 to 17.5% by weight of aluminum nitride powder to aluminum oxide powder and firing at 1500 to 1750°C, aluminum oxynitride containing unreacted aluminum oxide and aluminum nitride or only aluminum oxide can be baked. A compact is produced, and then this sintered compact is ground into powder with an average particle size of 3.5 μm or less, and this powder is further heated for 1 to 5 hours at 1750 to 1900°C in nitrogen.
A method for producing a transparent aluminum oxynitride sintered body, characterized by hot press sintering under pressure of kgf/cm^2 or more. (2) By mixing 9 to 17.5% by weight of aluminum nitride powder to aluminum oxide powder and firing at 1500 to 1750°C, aluminum oxynitride containing unreacted aluminum oxide and aluminum nitride or only aluminum oxide can be baked. A compact is produced, and then this sintered compact is ground into a powder with an average particle size of 3.5 μm or less, and a compound containing yttrium is added to this powder in an amount of 0.02 to 3% by weight in terms of yttrium oxide. Mix and 175 ml under nitrogen
1 to 5 hours at 0 to 1900℃, 100kgf/cm^2
A method for producing a transparent aluminum oxynitride sintered body, characterized by hot press sintering under the above pressure.