JPH04923B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for producing easily sinterable aluminum nitride powder, which makes it possible to obtain a dense sintered body. [Technical background of the invention and its problems] Aluminum nitride (AlN) has high strength from room temperature to high temperature and excellent chemical resistance, so it is used as a heat-resistant material. Due to its insulating properties, it is also seen as a promising material for heat sinks in semiconductor devices. These
AlN usually does not have a melting point and decomposes at high temperatures of 2200°C or higher, so it is used as a sintered body except for applications such as thin films. Such AlN sintered bodies are usually made by molding AlN powder,
Although it is manufactured by sintering, it is common to add a sintering aid to the AlN powder for the purpose of increasing the density of the sintered body. Further, it is known that the properties of the obtained AlN sintered body are greatly influenced by the properties of the AlN powder as a starting material and the sintering aid added. In other words, the average particle size of the AlN powder is small, there is little variation in particle size and particle shape, and the sintering aid is uniformly dispersed in the AlN powder.
This is desirable for obtaining a dense AlN sintered body. AlN powder has conventionally been manufactured by applying the direct nitriding method of aluminum or the carbon reduction method of alumina, etc., but with such methods, it is necessary to reduce the particle size and reduce the variation in particle size and particle shape. I can't. Moreover, when adding and mixing a sintering aid to such AlN powder, no matter what method is applied, it is difficult to achieve an ideal dispersion state of the sintering aid because it is a mixture of powders. be. [Object of the Invention] The present invention solves the conventional problems, and has a small average particle size, less variation in particle size and particle shape, and
Moreover, it is an object of the present invention to provide a method for producing easily sinterable aluminum nitride powder in which a sintering aid can be uniformly dispersed. [Summary of the invention] In the manufacturing process of AlN powder, the present inventors
Conventionally, aluminum hydroxide powder is used as a starting material, and at the stage of producing this AlN powder,
If the sintering aid that was added after AlN powder production is added and then fired, the obtained fired powder will be AlN powder that already contains the sintering aid, so the above purpose can be achieved. After confirming this, we have completed the present invention. That is, the method for producing easily sinterable aluminum nitride powder of the present invention includes aluminum hydroxide powder,
It is characterized in that at least one powder of a rare earth element compound is added to carbon powder or a mixture with a substance that produces carbon powder at high temperatures, and then fired in a non-oxidizing atmosphere containing nitrogen. Examples of the carbon powder used in the method of the present invention include carbon black and graphite, and examples of substances that produce carbon powder at high temperatures include various resinous substances such as paraffin compounds, novolac, and styrene. In the method of the present invention, at least one powder of a compound functioning as a sintering aid, that is, a rare earth element compound, is added to and mixed with the aluminum hydroxide powder and the carbon powder. Rare earth elements include Y, La, Ce, Sm, Dy, Nd,
Examples include Gd, Pr, Ho, Er, Yb, etc., and Y, Sm, La, and Ce are particularly suitable. Moreover, as compounds of these elements, carbonates, oxides, borides, or halides are preferable. In the method of the present invention, when adding these compound powders, it is preferable to use an alkaline earth element compound powder in addition to the rare earth element compound. Such alkaline earth elements include Mg,
Examples include Ca, Sr, Ba, etc., especially Ca, Sr,
Ba is preferred. When both are added together, as will be described later, the particle size and shape of the obtained AlN powder and the relative density ratio of the sintered body are further improved compared to when both are used alone. The purity of each of the above-mentioned powders, that is, the aluminum hydroxide powder, the carbon powder, and the additive compound powder, is preferably 99% or more, and these can be easily produced industrially.
Further, the particle size of each powder is preferably as small as possible, and it is particularly preferable that the average particle size of the carbon powder and additive compound powder is 1.0 μm or less. The blending amount of these powders is preferably carbon powder per 1 part by weight of aluminum hydroxide powder.
0.2 to 2.0 parts by weight, more preferably 0.35 to 1.0 parts by weight, and the total amount of additive compound powder is preferably 0.005 to 0.005 parts by weight.
The amount is set to 1.0 part by weight, more preferably 0.005 to 0.1 part by weight. The blending amount of carbon powder is 1 part by weight of aluminum hydroxide powder.
If it is less than 0.2 parts by weight, a large amount of alumina powder will remain unreacted, and if it exceeds 2.0 parts by weight,
Although it is possible to produce AlN powder, it is not preferable because the yield decreases. On the other hand, if the amount of additive compound powder blended is less than 0.005 parts by weight per 1 part by weight of aluminum hydroxide powder, it will hardly be effective as a sintering aid during powder sintering, and if it exceeds 1.0 parts by weight, aluminum nitride This is not preferable because the properties of the powder itself change. In the method of the present invention, a predetermined amount of each powder is mixed using a conventional method such as a ball mill, and then fired. The firing step is performed in a non-oxidizing atmosphere containing nitrogen. Specifically, the firing atmosphere may be nitrogen gas or ammonia gas alone, or a mixed gas system of these gases and an inert gas. The firing temperature is preferably 1300-1850℃,
More preferably it is 1400-1550°C. If this firing temperature is less than 1300℃, it is difficult to generate AlN powder,
If the temperature exceeds 1850°C, grain growth etc. will occur and grains will form, which is not preferable. In this firing process, first, the aluminum hydroxide powder is decomposed to produce fine activated alumina powder. Subsequently, when the reaction initiation temperature is reached, aluminum nitride produced by the reductive nitriding reaction grows using the additive compound functioning as the sintering aid as a nucleus. As a result, it contains a sintering aid,
Moreover, aluminum nitride powder having a small particle size and small variations in particle shape and particle size can be obtained. The average particle size of the aluminum nitride powder thus obtained is 2.0 μm or less, further 1.0 μm or less,
The variation is also extremely small, less than ±0.3 μm. Note that when a large amount of carbon powder is added, some unreacted carbon may remain, but this can be oxidized and removed by heating at 600 to 850° C. in an oxidizing atmosphere. In addition, although the additive compound powder may be partially reduced and nitrided in the above reaction process, its function as a core when synthesizing aluminum nitride powder and its function as a sintering aid is never impaired. . As described above, in the method of the present invention, there is an additive compound powder that functions as a sintering aid in the reaction system even before aluminum nitride is produced, and this is used as a core to form fine aluminum nitride powder. As a result, aluminum nitride powder in which the sintering aid is uniformly dispersed is obtained. This aluminum nitride powder has the advantage that it can be molded and sintered as it is, depending on the situation, and the resulting sintered body will be extremely dense. [Examples of the Invention] Examples 1 to 13 100 g of mixed powder obtained by mixing aluminum hydroxide powder, carbon powder, and powder of the indicated additive compound in the indicated parts by weight was placed in a carbon tray and placed in the indicated atmosphere. , temperature and time. The resulting product was treated in air at 700° C. for 3 hours to remove residual carbon. The constituent phases of each powder obtained above were examined by X-ray diffraction. Furthermore, after lightly pulverizing these powders, they were molded into a shape of 30 x 30 x 5 mm, and then sintered in a nitrogen atmosphere at the indicated temperature for 2 hours to obtain an aluminum nitride sintered body. Ta. The relative density ratio of each obtained sintered body was measured.
The above results are shown in the table. Incidentally, the average particle size of the additive compounds used in the above examples was 1.2 to 1.8 μm for the a group compound and 0.8 to 1.2 μm for the a group compound. Furthermore, the average particle size of the obtained AlN powders was 0.9 to 1.2 μm, and the particle size distribution was
It was 0.6 to 1.6 μm.

[Table] ＋＋＋＋＋＞＋＋＋＋＞＋＋＋＞＋＋＞＋＞ ＜＋
[Effects of the Invention] As is clear from the above description, by applying the method of the present invention, easily sinterable aluminum nitride powder having a small particle size and small variations in particle shape and particle size can be obtained. Moreover, the resulting aluminum nitride powder has an additive compound that functions as a sintering aid during sintering that is uniformly dispersed, making it possible to produce a very dense sintered body. Its industrial value is great.

Claims (1)

[Claims] 1. Adding at least one powder of rare earth element compound to a mixture of aluminum hydroxide powder and carbon powder or a substance that produces carbon powder at high temperature,
Next, a method for producing easily sinterable aluminum nitride powder, which comprises firing in a non-oxidizing atmosphere containing nitrogen. 2. The method for producing easily sinterable aluminum nitride powder according to claim 1, wherein an alkaline earth element compound is further added in addition to the rare earth element compound. 3. Claim 1, wherein the compound is a carbonate, oxide, nitride, boride, or halide
A method for producing easily sinterable aluminum nitride powder as described in 1. 4 For 1 part by weight of aluminum hydroxide powder,
Claim 1, wherein the carbon powder is 0.2 to 2.0 parts by weight and the additive compound powder is 0.005 to 1.0 parts by weight.
A method for producing easily sinterable aluminum nitride powder as described in 1. 5. The method for producing easily sinterable aluminum nitride powder according to claim 1, wherein the firing temperature is 1300 to 1850°C. 6. The method for producing easily sinterable aluminum nitride powder according to claim 1, wherein the carbon powder and the additive compound powder both have an average particle size of 1.0 μm or less.