JPH0474301B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel aluminum nitride composition and method for producing the same. Sintered aluminum nitride is a substance that is attracting attention as a variety of high-temperature materials because it has special characteristics such as high thermal conductivity, corrosion resistance, and high strength. However, aluminum nitride powder, which is the raw material for the sintered body, has not yet been developed with sufficient purity and particle size, and there are also difficulties in sinterability.
It has drawbacks such as the need to add various additives and to sinter at high temperature and high pressure. Further, the sintered body sintered in this manner also had low purity and did not sufficiently reflect the original properties of aluminum nitride. Conventionally, the following two typical methods are known as methods for synthesizing aluminum nitride powder. Specifically, there are two methods: nitriding metal aluminum powder in nitrogen or ammonia gas, and firing a powder mixture of alumina and carbon in nitrogen or ammonia gas. In the former method, the raw material aluminum metal is crushed to increase the nitriding rate, and the resulting AlN is used as the raw material for sintering to an optimal number of μm.
Because it is difficult to avoid contaminating impurities in both steps of pulverizing to a particle size of m or less, or because unreacted metallic aluminum inevitably remains,
Usually, those containing several weight percent of cationic impurities were obtained. Furthermore, since the powder undergoes surface oxidation during pulverization, it generally contains 2% by weight or more of oxygen. In addition, although the latter method allows the synthesis of aluminum nitride with relatively fine grain size, it is difficult to carry out the nitriding reaction completely.
Usually several weight percent of unreacted alumina remained. Furthermore, even with this method, pulverization is required in many cases to obtain fine powder of several μm or less, and contamination of cationic impurities and oxygen cannot be avoided at this time. Other methods for synthesizing aluminum nitride powder include the plasma jet method and the arc discharge method using metallic aluminum as a raw material, but with either method it is difficult to obtain a homogeneous fine powder and it is difficult to avoid free aluminum impurities. Therefore, in the past, only aluminum nitride powder with high content of these cationic impurities or oxygen could be obtained, and the aluminum nitride sintered body produced using these aluminum nitrides was not able to exhibit sufficient properties as described above. I wasn't quite there yet. In addition, as mentioned above, in order to improve sinterability,
This requires the use of aluminum nitride, which has a high oxygen content, the addition of additives, and high-temperature, high-pressure sintering conditions. For this reason, this method could not necessarily be said to be industrially satisfactory. The present inventors have been conducting extensive research on industrial methods for producing aluminum nitride powder. As a result, we developed a high-purity powder that is ultra-fine and has a relatively low oxygen content, which was previously considered impossible.As a result of examining the sinterability of this powder, we found that it has a relatively low oxygen content. Nevertheless, it has been found that it has excellent sinterability that cannot be obtained with conventional aluminum nitride powder, and that it can also be made into a sintered body that has translucency depending on the sintering conditions, and has already been proposed. The present invention further provides an aluminum nitride composition containing specific additives to improve the sinterability or translucency of the aluminum nitride sintered body, and a method for producing the same. That is, the present invention provides () at least 90% by weight of aluminum nitride, () at least one metal selected from the group consisting of alkaline earth metals, lanthanum group metals, and yttrium, or the metal compound, converted into an oxide. 0.02 to 5.0% by weight () 4.5% by weight or less of bonded oxygen atoms () 0.5% by weight or less of unavoidably mixed cationic impurities calculated as oxide Consisting of the above () to (), the average particle size is 2μ
The aluminum nitride composition contains 70% by volume or more of particles having a particle size of 3 μm or less and a particle size of 3 μm or less. In particular, for compositions intended to obtain a translucent sintered body, aluminum nitride must be at least 93% by weight, bonded oxygen atoms must be at most 3.0% by weight, and unavoidably mixed cationic impurities must be converted into oxides. less than 0.3% by weight,
In particular, the total content of iron, chromium, nickel, cobalt, copper and titanium is preferably 0.1% by weight or less. A more preferred embodiment is, as will be understood from the examples described later, that (a) the aluminum nitride component is 96.9% by weight or more, the oxygen component is 1.3% by weight or less, and the unavoidably mixed cation impurities are calculated in terms of oxides. Average particle size of 2μm consisting of 0.5% by weight or less
In the following, 99.98 to 95% by weight of aluminum nitride powder containing 70% by volume or more of particles of 3 μm or less and at least one metal or metal compound selected from the group consisting of alkaline earth metals, lanthanum group metals, and yttrium are used. It is a homogeneously mixed aluminum nitride composition consisting of 0.02 to 5.0% by weight in terms of oxide. The present invention also provides (a) alumina with a purity of 99.0% by weight or more and an average particle size of 2 μm or less, (b) carbon with an ash content of 0.2% by weight or less and an average particle size of 1 μm or less, and (c)
Each component consisting of at least one metal or metal compound selected from the group consisting of alkaline earth metals, yttrium, and lanthanum group metals is alumina (a) and carbon (b) in a weight ratio of 1: 0.36 to 1:1, and the metal or metal compound (c) is present in the resulting aluminum nitride composition in terms of oxide.
The mixed composition is mixed in a liquid dispersion medium so that it is contained in the range of 0.02 to 5.0% by weight, and the mixed composition is dried if necessary, and then heated at 1400 °C under a nitrogen or ammonia atmosphere.
Also provided is a method for producing an aluminum nitride composition, characterized in that it is fired at a temperature of ~1700°C. Furthermore, the present invention provides (a) a purity of 99.0% by weight or more,
Alumina with an average particle diameter of 2 μm or less and carbon with an ash content of 0.2% by weight or less and an average particle diameter of 1 μm or less are mixed in a liquid dispersion medium at a weight ratio of 1:0.36 to 1:1. , After drying the mixed composition if necessary, it is heated to 1400 to
Calcinate at a temperature of 1700°C to obtain aluminum nitride, and add (iii) an alkaline earth metal to the aluminum nitride.
At least one metal or metal compound selected from the group consisting of yttrium and lanthanum group metals is added in an amount of 0.02% in terms of oxide in the aluminum nitride composition.
Also provided is a method for producing an aluminum nitride composition, characterized in that the aluminum nitride composition is added in an amount of 5.0% by weight. The aluminum nitride composition provided by the present invention is
It is a powder with an average particle size of 2 μm or less. If the average particle size of the aluminum nitride composition becomes a powder larger than the above range, the sinterability of the aluminum nitride composition will deteriorate, which is not preferable. Further, in order to obtain sufficient light transmittance of the sintered body, it is preferable that the number of coarse particles is small. For example, 3μm
It is preferable that the following particles account for 70% by volume or more. Further, the oxygen content in the aluminum nitride composition and the amount of unavoidably mixed cationic impurities have a great influence on the sinterability and translucency of the aluminum nitride composition. That is, the oxygen content in the aluminum nitride composition needs to be 4.5% by weight or less, preferably 3.0% by weight or less. In particular, when obtaining an aluminum nitride sintered body with good translucency, the oxygen content should be
It is best to control the content to 3.0% by weight or less. Furthermore, various types of cationic impurities can be considered as unavoidable contamination. Examples include unreacted raw materials, ie, alumina and carbon remaining in aluminum nitride, and impurity components mixed in with solvents, mixers, piping, etc. during the manufacturing process. Therefore, the above-mentioned unavoidably mixed cationic impurities referred to in the present invention may be considered to be cations of compounds other than those caused by aluminum nitride and actively added additives in the resulting aluminum nitride composition. I can do it. The aluminum nitride content in the aluminum nitride composition obtained by the present invention is generally 90% by weight or more based on the oxygen content in the aluminum nitride composition, and the sintered body produced using the aluminum nitride has a content of 90% by weight or more. In particular, when translucency is required, the content is preferably 93% by weight or more. Furthermore, as shown in the examples, it is preferable that the AlN content is 96.9% by weight or more. Typical examples of cationic impurities that are unavoidably mixed include those that are mixed due to raw materials such as iron, chromium, nickel, cobalt, copper, titanium, silicon, manufacturing equipment, and unreacted impurities. Some are contained as alumina and carbon. Among these cationic impurities that are inevitably mixed in, unreacted alumina, carbon, or those in which the surface of aluminum nitride is oxidized and changed to aluminum oxide, etc., extremely deteriorate the properties of the aluminum nitride of the present invention. For example, cationic impurities such as alumina, carbon, and silica
Even if it is mixed in an amount of about 0.3 to 0.5% by weight, it does not have a bad effect on the sinterability. However, if the sintered body is required to have translucency, it is necessary to control the content of the cationic impurities such as alumina, carbon, silica, etc. to 0.5% by weight or less. Also, especially iron, chromium,
Since each component of nickel, cobalt, copper, and titanium has an adverse effect on the translucency of the sintered body of aluminum nitride, it is preferable to reduce the amount of these components mixed in as much as possible. Therefore, in the present invention, the amount of the unavoidably mixed cationic impurities is preferably controlled to 0.5% by weight or less, preferably 0.3% by weight or less. In addition, in order to provide sufficient translucency to the aluminum nitride sintered body, the total content of iron, chromium, nickel, cobalt, copper, and titanium must be 0.1% by weight among the unavoidably mixed cationic impurities mentioned above.
It is preferable to control the temperature so that it does not exceed . The additive used in the present invention is an additive made of at least one metal or metal compound selected from the group consisting of alkaline earth metals, yttrium, and lanthanum group metals. The alkaline earth metal is not particularly limited, and beryllium, magnesium, calcium, strontium, and barium can be used. Among the above-mentioned metal components, beryllium and magnesium may have inferior performance for imparting translucency to a sintered body compared to the other alkaline earth metal components mentioned above. Therefore, for the purpose of imparting translucency, calcium, strontium and barium are preferably used industrially. Further, the above-mentioned lanthanum group metals can be used without particular limitation. For example, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy) , holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu) can be suitably used. In particular, lanthanum, cerium, neodymium, etc. are preferably used industrially. The amount of the additive used varies depending on the oxygen content in the aluminum nitride composition, the content of cationic impurities, the particle size of aluminum nitride, etc., and cannot be absolutely limited, but it is generally 0.02 in terms of oxide. ~
It is sufficient to choose from a range of 5.0% by weight, preferably from 0.05 to 3.0% by weight. The method for controlling the cationic impurities in the aluminum nitride composition to below the content is not particularly limited and may be any method, but generally high purity raw materials are used and aluminum nitride or nitride is Except for the step of pulverizing the aluminum composition, the resulting aluminum nitride composition may have a small average particle size. The following two methods can be exemplified as particularly preferably adopted methods for producing an aluminum nitride composition. First, the first manufacturing method consists of (a) alumina with a purity of 99.0% by weight or more and an average particle size of 2 μm or less, (b) carbon and (halogen) with an ash content of 0.2% by weight or less and an average particle size of 1 μm or less. ) Each component consists of at least one metal or metal compound selected from the group consisting of alkaline earth metals, yttrium, and lanthanum group metals, and the weight ratio of (a) alumina to (b) carbon is 1 : within the range of 0.36 to 1:1 and
The metal or metal compound (c) is mixed in a liquid dispersion medium so that the resulting aluminum nitride composition contains 0.02 to 5.0% by weight in terms of oxide, and the mixed composition is mixed as required. This is a method for producing an aluminum nitride composition, which is characterized in that the aluminum nitride composition is dried at a temperature of 1,400 to 1,700°C in a nitrogen or ammonia atmosphere. Next, the second manufacturing method uses (a) alumina with a purity of 99.0% by weight or more and an average particle size of 2 μm or less, and (b) carbon with an ash content of 0.2% by weight or less and an average particle size of 1 μm or less. The weight ratio is 1:
Mixing in a liquid dispersion medium at a ratio of 0.36 to 1:1, drying the mixed composition if necessary, and baking at a temperature of 1400 to 1700 ° C. in a nitrogen or ammonia atmosphere to obtain aluminum nitride, (c) At least one metal or metal compound selected from the group consisting of alkaline earth metals, yttrium, and lanthanum group metals is added to the aluminum nitride by weight of 0.02 to 5.0% in terms of oxide. % of the aluminum nitride composition. The above method does not require the step of pulverizing aluminum nitride or aluminum nitride composition obtained by firing raw materials. Therefore, impurity components mixed in during the grinding process can be ignored, and the surface of the aluminum nitride or aluminum nitride composition can be prevented from being oxidized during the grinding and increasing the oxygen content. As described above, there is a great advantage in omitting the step of pulverizing aluminum nitride or an aluminum nitride composition. In order to omit the above-mentioned pulverization process and obtain an aluminum nitride composition with good properties, the raw materials in the above-mentioned manufacturing process are mixed using a device made of a specific material.
It is important to carry out so-called wet mixing in a solvent. This wet mixing method not only allows the raw materials to be mixed uniformly, but also surprisingly prevents the raw material particles from agglomerating and becoming coarse, resulting in fine and uniform aluminum nitride particles. Become.
Moreover, as mentioned above, it is possible to completely prevent impurity components mixed in during the grinding process, etc., and it is also possible to prevent oxidation of the aluminum nitride surface, so it has superior sinterability compared to conventional methods, and the sintered body is also transparent. This results in an aluminum nitride composition with excellent properties. The solvent used in the wet mixing is not particularly limited, and any known wet mixed solvent can be used. Generally, water, alcohol, etc. are preferably used industrially. Further, the conditions and equipment for the wet mixing are not particularly limited, and any one can be used as long as it can suppress impurity components that inevitably mix into the aluminum nitride composition. Generally, the wet mixing conditions may be carried out at normal temperature and normal pressure, and are not affected by temperature and pressure. Further, as the mixing device, any known device or means may be used as long as the material is selected so that it does not become an unavoidable impurity component. For example, it is common to use a mill with built-in balls or rods. However, in order to avoid increasing the impurity components that inevitably mix into the resulting aluminum nitride composition, the material of the mixing device, such as the inner wall of the mill, spheres, rods, etc., must be made of aluminum nitride itself or 99.9% by weight. % or higher purity alumina is preferably used. It is also possible to use plastic material. In other words, the entire surface that comes into contact with the raw material is made of plastic or coated with plastic. The plastic is not particularly limited, and for example, polyethylene, polypropylene, nylon, polyester, polyurethane, etc. can be used, but generally, plastics may contain various metal components as stabilizers, so check in advance and avoid unavoidable It is best to prevent it from becoming an impurity component mixed in. In addition, the aluminum nitride composition obtained by the present invention can be used to omit the pulverization step in the manufacturing process and to form fine particles with an average particle size of 2 μm or less with good sinterability, or with a high-purity aluminum nitride composition. Therefore, it is preferable to use alumina and carbon with specific properties. In other words, the raw material alumina should have a purity of 99.0% by weight or more, preferably 99.0% by weight or more, in order to suppress the unavoidable impurity components.
It is necessary to use 99.9% by weight or more. Further, in order to control the particle size of the resulting aluminum nitride composition, it is necessary to use alumina having an average particle size of 2 μm or less. Carbon, which is another raw material component of the aluminum nitride composition, has an ash content of 0.2% by weight or less, preferably 0.1% by weight or less in order to suppress impurity components that inevitably enter the aluminum nitride composition. It is necessary to use Furthermore, since the average particle size of the carbon affects the particle size of the aluminum nitride composition obtained, it is necessary to use carbon with an average particle size of 1 μm or less. Carbon black, graphitized carbon black, etc. can be used as the carbon, but carbon black is generally preferred. The raw material usage ratio of alumina and carbon varies depending on the properties of the alumina and carbon, such as their purity and particle size, so it is best to perform a preliminary test to determine the ratio, but normally the weight ratio of alumina and carbon is 1:0.36. Wet mixing may be carried out in a ratio of 1:1 to 1:1. The wet mixed raw materials are dried if necessary and then fired at a temperature of 1400 to 1700°C under a nitrogen atmosphere. If the firing temperature is lower than the above temperature, the reduction and nitrogenation reaction will not proceed industrially sufficiently, which is not preferable. In addition, if the firing temperature is higher than the above temperature, a part of the aluminum nitride composition obtained will sinter and agglomeration between particles will occur, making it difficult to obtain an aluminum nitride composition with the desired particle size, which is preferable. do not have. The method of mixing the additive used in the present invention with aluminum nitride or an aluminum nitride composition is not particularly limited, and an aluminum nitride composition containing the additive may be obtained by mixing with raw materials for producing aluminum nitride and firing. Either of the following methods is adopted: alumina and carbon are fired by the method described above to obtain aluminum nitride, and then additives are added. In the former method, that is, mixing additives into raw materials along with alumina and carbon, the firing temperature of the raw materials is high, so the additives sublimate or scatter, and it is often thought that the effect cannot be achieved. However, it is also an effective mixing method in the present invention. When an aluminum nitride composition is obtained by mixing the alumina and carbon with additives as raw materials, it is currently not clear how the additives are combined or mixed.
The inventors assume that aluminum nitride is present in the aluminum nitride composition in the form of an oxide or nitride. The additive used in the present invention is generally contained in an aluminum nitride composition consisting of aluminum nitride and the additive in an amount of 0.02 to 5% by weight in terms of oxide, preferably in order to fully exhibit its effects.
What is necessary is just to mix so that it may be contained in the range of 0.05-3.0 weight%. That is, most of the aluminum component of the alumina used in the present invention is aluminum nitride, and the mixing ratio of additives is almost the same as the ratio of additives contained in the aluminum nitride composition. What is necessary is to calculate the aluminum nitride composition obtained from the added mixing amount. Since the aluminum nitride composition obtained by the above method has excellent sinterability, not only hot press sintering but also atmospheric pressure sintering is possible. The apparatus used for hot press sintering and pressureless sintering may be any known apparatus without particular limitation. Sintering conditions vary depending on the properties of the aluminum nitride composition, sintering method, etc., but generally it is sufficient to select the following conditions under a non-oxidizing atmosphere, such as a nitrogen atmosphere, or under vacuum. . For example, in pressureless sintering, if no additives are mixed, it is necessary to select a temperature of 1850° C. or higher under atmospheric pressure in order to obtain a sintered body with a theoretical density of 90% or higher. However, when the aluminum nitride composition of the present invention mixed with additives is sintered under normal pressure, the additives can also act as auxiliary agents during sintering, so sintering can be performed at lower temperatures than the above. be. For example, when about 3% by weight of additives are mixed, a sintered body with a theoretical density of 90% or more can be obtained at 1700°C or higher. Further, in hot press sintering, the strength of the pressure mold becomes the critical pressure, and a pressure of 350 kg/cm ² or less is usually selected. Industrially generally 50 to 300
A pressure of Kg/cm ² is most preferably employed. Regarding the hot press temperature, a sintered body with a theoretical density of 90% or more can be obtained at a temperature of 1600°C or higher. The sintered body obtained above has an aluminum nitride composition with an oxygen content of 3.0% by weight or less and unavoidably mixed cationic impurities of 0.3% by weight or less, especially iron,
When using a material with a total content of chromium, nickel, cobalt, copper and titanium of 0.1% by weight or less,
The sintered body has excellent translucency. Translucency can be imparted to the sintered body when the oxygen content of the aluminum nitride composition is 3% by weight or up to about 0.5% by weight of unavoidably mixed cationic impurities, excluding special cases. The aluminum nitride composition of the present invention is not only used as the above-mentioned sintered body, but is also excellent as a raw material for Sialon. When the aluminum nitride composition that imparts translucency to the sintered body is used as a raw material for producing sialon, it is possible to produce sialon having translucency. Furthermore, since the aluminum nitride composition of the present invention is a fine powder, it can be used as an auxiliary agent for various ceramics. The various analytical methods and analytical devices used in the following Examples and Comparative Examples are as follows. Cation analysis: Plasma emission spectrometer (Daini Seiko ICP-AES) Carbon analysis: Carbon in metal analyzer (Horiba, Ltd.)
EMIA-3200) Oxygen analysis: Metal oxygen analyzer (Horiba, Ltd.)
EMGA-1300) Nitrogen analysis: Melting separation neutralization titration method
1000 Rapid surface area measuring device) Average particle size and particle size distribution measuring device: Horiba, Ltd.
CAPA-500 Thermal conductivity measuring device: Rigaku Laser method thermal constant measuring device PS-7 Light transmittance measuring device: Hitachi self-recording spectrophotometer 330 type infrared spectrophotometer 260-30 type The light transmittance was calculated using the following formula. I/I _p = (1-R) ² e ^- 〓 ^t ...(1) Here, I _p is the intensity of the incident light, I is the intensity of the transmitted light,
R is the reflectance, t is the thickness of the sintered body, and μ is the absorption coefficient. R is determined by the refractive index of the sintered body, and if the refractive index is n, R is expressed by the following equation when measured in air. R=(1-n) ² /(1+n) ² ...(2) μ in formula (1) is an index representing the translucency of the sintered body, and μ shown in the examples below. The value of was calculated according to equation (1). Example 1 The purity is 99.99% (impurity analysis values are shown in Table 1), the average particle diameter is 0.52 μm, and the proportion of particles is 3 μm or less.
20g of alumina of 95vol% and 10g of carbon black with an ash content of 0.08wt% and an average particle size of 0.45μm,
Using a nylon pot and a nylon-coated pole, the mixture was uniformly mixed in a ball mill using ethanol as a dispersion medium. After drying the resulting mixture,
It was placed in a flat plate made of high-purity graphite and heated at 1600° C. for 6 hours while continuously supplying nitrogen gas at 3/min into an electric furnace. The resulting reaction mixture was heated in air at a temperature of 750° C. for 4 hours to oxidize and remove unreacted carbon. As a result of X-ray diffraction analysis, the obtained white powder was found to be single-phase AlN, with no Al ₂ O ₃ diffraction peak. Also, the average particle size of the powder is
The diameter was 1.31 μm, and 90% of the volume was 3 μm or less.
When observed using a scanning electron microscope, this powder has an average
They were uniform particles of about 0.7 μm. Further, the measured value of the specific surface area was 4.0 m ² /g. The analytical values of this powder are shown in Table 2.

【table】

[Table] Example 2 Ca was added to 10 g of aluminum nitride powder obtained in the same manner as in Example 1 to give a concentration of 0.2 wt% as CaO.
(NO ₃ ) ₂ ·4H ₂ O and ethanol were added as a liquid medium and mixed using a polyethylene pestle in a polyethylene mortar. After drying this mixture, 1.0
g was placed in a graphite die coated with BN (boron nitride) with a diameter of 20 mm, and heated under a pressure of 100 kg/cm ³ in 1 atm nitrogen gas using a high frequency induction heating furnace.
Hot press at 2000℃ for 2 hours to create a diameter of 20mm.
A sintered body was obtained. The density of this sintered body is 3.28g/cm ³
According to X-ray diffraction analysis, it was single-phase AlN. This sintered body had an AlN content of 97.8 wt%, an oxygen content of 0.7 wt%, and a thermal conductivity of 79 W/m·K. Furthermore, the light transmittance of this sintered body processed and polished to a thickness of 0.5 mm is 33 for light with a wavelength of 6 μm.
% (absorption coefficient 19 cm ^-1 ). In addition, as a result of measuring the above three-point bending strength, the average was 45.1Kg/mm ³ at 1200℃.
It was hot. Example 3 Various additives shown in Table 3 were added to aluminum nitride (10 g) obtained in the same manner as in Example 1 and hot pressed to obtain a sintered body. The results are shown in Table 3.

[Table] Example 4 Ca was added to aluminum nitride powder (10 g) obtained in the same manner as in Example 1 to give a concentration of 3.0 wt% as CaO.
(NO ₃ ) ₂ ·4H ₂ O was added to ethanol as a solvent and mixed uniformly. After drying this mixture, it was uniaxially pressed in a mold with a diameter of 20 mm, and then this molded body was
Isostatically pressed at a pressure of Kg/ ^cm3 , the density is 1.56g/ ^cm3.
It was made into a molded body. This compact was placed in a boron nitride crucible, and heated using a graphite heating element in a high-frequency induction heating furnace with 1 atm of N _{2 .}
Heated at 1900°C in gas for 3 hours. The density of the compact before sintering was 1.73 g/cm ³ . The sintered body was a yellowish translucent body with a density of 3.23 g/cm ³ . The AlN content of this sintered body is 96.0wt%, and the oxygen content is
It was 1.5wt%. Also, the thermal conductivity of this sintered body is
64W/m・K, and the transmittance of 6μm light is 28% (μ=
23cm ^-1 ). Example 5 Various additives shown in Table 4 were added to aluminum nitride powder (10 g) obtained in the same manner as in Example 1, in the same manner as in Example 4. The mixed powder was sintered under normal pressure using the same equipment and sintering conditions as used in Example 4. The results are shown in Table 4.

[Table] Example 6 20 g of the same alumina used in Example 1 and 8 g of carbon were uniformly mixed using a nylon pot and ball with water as a dispersion medium. After drying the resulting mixture, it was placed in a high-purity graphite flat plate and heated at 1550°C while continuously supplying nitrogen gas at 3/min into the furnace.
The mixture was heated at a temperature of 6 hours. The resulting reaction mixture was heated in air at a temperature of 800° C. for 4 hours to remove unreacted carbon. The AlN content of the obtained powder was 95.8 wt% and the oxygen content was 2.1 wt%. In addition, the amount of cation impurities in the AlN powder was determined in Example 1.
It was at almost the same level as shown in Table 2. The average particle size of this powder is 1.22μ, and 3μm or less is
It accounted for 92% capacity. Y(NO ₃ ) ₃ .6H ₂ O was added to the AlN powder (10 g) obtained above to give a concentration of 0.5 wt% as Y ₂ O ₃ in ethanol as a liquid medium and mixed uniformly. After drying this mixture (1 g), it was hot pressed in vacuum using the apparatus used in Example 2 at a pressure of 200 kg/cm ² and a temperature of 1900° C. for 2 hours. The obtained sintered body was a translucent body with a density of 3.27 g/cm ³ and an AlN content of
96.5wt%, and the oxygen content was 1.5wt%. The thermal conductivity of the sintered body is 56W/m・K, and the sintered body has a thermal conductivity of 0.5
Although processed and polished to a thickness of mm, the transmittance for light of 6 μm was 20% (μ = 29 cm ⁻¹ ). Example 7 Ca was added to AlN powder (10 g) obtained in the same manner as Example 6 to give a concentration of 4.0% as CaO.
(NO ₃ ) ₂ ·4H ₂ O and ethanol were added as a liquid medium and mixed uniformly. After drying this mixed powder (1 g), it was sintered under normal pressure using the same apparatus and sintering conditions as used in Example 3. The obtained sintered body is a yellowish semi-transparent body with a density of 3.20 g/cm ³ and an AlN content.
The oxygen content was 94.2wt%, and the oxygen content was 2.5wt%. Also,
The thermal conductivity of this sintered body is 42W/m・K,
Although processed and polished to a thickness of 0.5 mm, the transmittance of light at 6 μm was 10% (μ = 43 cm ⁻¹ ). Example 8 Alumina with a purity of 99.3% and an average particle size of 0.58 μm
20 g and 16 g of carbon black having an ash content of 0.15 wt% and an average particle diameter of 0.44 μm were uniformly mixed using a nylon pot and ball using hexane as a dispersion medium. After drying the resulting mixture, it was placed in a flat plate made of high-purity graphite and heated at a temperature of 1650° C. for 4 hours while continuously supplying ammonia gas at 1/min into the furnace. The resulting reactant was heated in air at a temperature of 750°C for 6 hours.
The mixture was heated for a period of time to oxidize and remove unreacted carbon.
The average particle size of the powder is 1.42 μm, and 3 μm or less is
It accounted for 84% capacity. The analysis results of the powder are shown in Table 5.

[Table] Ba(NO ₃ ) ₂ was added to the AlN powder (10 g) obtained above and ethanol was added as a liquid medium to give a concentration of 0.2 wt% as BaO and mixed uniformly. After drying, this mixed powder (1 g) was hot pressed using the same equipment and sintering conditions as used in Example 2. The obtained sintered body was a grayish semi-transparent body with a density of 3.27g/
^cm3 , AlN content 97.9wt%, oxygen content 0.9wt
It was %. The thermal conductivity of this sintered body is 55W/
m・K, polished to a thickness of 0.5mm, but 6μ
The transmittance of m light was 8% (μ=48 cm ⁻¹ ). Example 9 130 g of alumina with a purity of 99.99 wt% and carbon black with an ash content of 0.08 wt% as used in Example 1
Calcium carbonate 1.0 with 65g and average particle size 3μm
Using a pot and ball coated with polyurethane resin, the mixture was uniformly mixed in a ball mill using ethanol as a dispersion medium. After drying the mixture, it was reacted and nitrided under the same conditions as in Example 1 to obtain AlN powder. The average particle size of the obtained powder was 1.44 μm,
3μm or less accounted for 86% of the capacity. Table 6 shows the analytical values of this powder.

[Table] The AlN powder (1 g) obtained above was used in Example 2.
Hot pressing was carried out using the same equipment and conditions as used in . The obtained sintered body is a dense semi-transparent body with a density of
3.26g/cm ³ , AlN content is 98.1%, oxygen content is
It was 0.7%. Also, the thermal conductivity of the sintered body is
60W/mK, 6μm polished to 0.5mm thickness
The transmittance for light was 28% (μ=23cm ^-1 ). Example 10 A pot and a ball made of polyurethane resin coated with 130 g of alumina with a purity of 99.99 wt%, the same as used in Example 1, 65 g of carbon black with an ash content of 0.08 wt%, and 0.52 g of Y ₂ O ₃ with an average particle size of 1 μm. The mixture was uniformly mixed in a ball mill using ethanol as a dispersion medium. After drying this mixture, it was reacted and nitrided under the same conditions as in Example 1 to obtain AlN powder.
The average particle size of the obtained powder was 1.50μm, and 3μm
m or less accounted for 83% of the capacity. Table 7 shows the analytical values of this powder.

[Table] The AlN powder (1 g) obtained above was used in Example 2.
Hot pressing was carried out using the same equipment and conditions as used in . The obtained sintered body had a density of 3.28 g/cm ³ , an AlN content of 98.1 wt%, and an oxygen content of 0.8 wt%. The thermal conductivity of the sintered body is 63 W/m・K, and the transmittance for light at 6 μm is 30% even though it is polished to 0.5 mm.
(μ=21cm ^-1 ). Example 11 The same procedure as in Example 10 was carried out except that the additives shown in Table 8 were used instead of Y ₂ O ₃ in Example 10. The results were as shown in Table 8.

【table】

Claims (1)

[Scope of Claims] 1 () 93% by weight or more of aluminum nitride, () at least one metal selected from the group consisting of alkaline earth metals, lanthanum group metals, and yttrium, or a compound of the metal, converted into an oxide. 0.02 to 5.0% by weight () 4.5% by weight or less of bonded oxygen atoms () 0.5% by weight or less of unavoidably mixed cationic impurities calculated as oxides, especially iron, chromium, nickel, cobalt, and copper. The total amount of titanium and titanium is 0.1% by weight or less, consisting of () to () above, and the average particle size is 2μ
An aluminum nitride composition containing 70% by volume or more of particles with a particle diameter of 3 μm or less. 2 (a) Purity of 99.0% by weight or more and average particle size of 2 μm
The following alumina, (b) carbon with an ash content of 0.2% by weight or less and an average particle size of 1 μm or less, and (c) at least one metal selected from the group consisting of alkaline earth metals, yttrium, and lanthanum group metals, or An aluminum nitride composition in which each component consisting of a metal compound contains (a) alumina and (b) carbon in a weight ratio of 1:0.36 to 1:1, and the metal or metal compound (c) is obtained. After mixing in a liquid dispersion medium so that the composition is contained in the range of 0.02 to 5.0% by weight in terms of oxide, and drying the mixed composition if necessary,
A method for producing an aluminum nitride composition, which comprises firing at a temperature of 1400 to 1700°C in a nitrogen or ammonia atmosphere. 3 (a) Purity of 99.0% by weight or more and average particle size of 2 μm
The following alumina and (b) carbon with an ash content of 0.2% by weight or less and an average particle diameter of 1 μm or less are mixed in a liquid dispersion medium at a weight ratio of 1:0.36 to 1:1, and the mixed composition is After drying the product as necessary, it is fired at a temperature of 1,400 to 1,700°C in a nitrogen or ammonia atmosphere to obtain aluminum nitride, and (c) a group consisting of alkaline earth metals, yttrium, and lanthanum group metals is added to the aluminum nitride. An aluminum nitride composition characterized in that at least one metal or metal compound selected from the following is added to the aluminum nitride composition in an amount of 0.02 to 5.0% by weight in terms of oxide. Production method.