JP6681693B2 - Method for producing aluminum nitride powder - Google Patents

Description

  The present invention relates to a method for producing aluminum nitride powder, which directly synthesizes high-purity aluminum nitride (AlN) from boehmite (AlOOH) powder.

  Aluminum nitride powder is used as a raw material for sintered bodies such as insulating substrates and as a filler for semiconductor encapsulation materials. As a method for synthesizing aluminum nitride powder, a method of heat-treating boehmite (AlOOH) or pseudo-boehmite (aluminum oxyhydroxide having low crystallinity) in a nitrogen-containing atmosphere in the presence of a carbon-containing substance is known (Patent Document 1-3). Further, a method of synthesizing aluminum nitride by reducing γ-alumina in a mixed gas of hydrocarbon and ammonia is known (Patent Document 4).

International Publication No. 2003/097527 JP-A-62-140505 JP-A-63-139008 JP-A-2000-44211

In the above-mentioned conventional method of synthesizing aluminum nitride by heat-treating powder of boehmite, pseudo-boehmite, γ-alumina, etc. in a nitrogen-containing gas, a carbon-containing substance is used to obtain a sufficient reducing power. In this case, a step of removing carbon is required to obtain a high-purity aluminum nitride powder product, which is troublesome. On the other hand, if aluminum nitride is synthesized using ammonia gas or the like without utilizing the reducing power of the carbon-containing substance, a powder containing a large amount of aluminum oxide (for example, α-Al ₂ O ₃ ) will be produced. There is a problem.

  An object of the present invention is to obtain an aluminum nitride single phase powder directly from a raw material powder containing Al without using a carbon-containing substance.

  As a result of various studies, the inventors have found that when a boehmite powder having a large specific surface area is used as a raw material, it becomes possible to obtain a powder composed of an aluminum nitride single phase in a non-oxidizing atmosphere containing ammonia gas. I found out.

The above-mentioned object has a BET specific surface area of 150 m ² / g or more, and in X-ray diffraction by Cu-Kα ray, in a region of a diffraction angle 2θ of 10 to 40 °, from the low angle side (A) 14.5 °. There are diffraction peaks in the vicinity, (B) around 28.2 °, and (C) around 38.3 °, and among the above A to C diffraction peaks, the peak height of A is the highest and the peak height of C is powder boehmite (AlOOH) exhibiting the lowest X-ray diffraction pattern, ammonia (NH ₃₎ content was heated held at 1200 to 1600 ° C. in a non-oxidizing atmosphere from 70 to 100% by volume, the whole of the boehmite This is achieved by the method for producing aluminum nitride powder, which is changed to aluminum nitride (AlN).
In particular, by converting all of boehmite (AlOOH) into aluminum nitride (AlN) by the above method, an aluminum nitride single phase powder can be obtained. Further, a powder of aluminum nitride single phase having a carbon content of 0 to 0.10 mass% can be obtained.
The ammonia (NH ₃ ) -containing non-oxidizing atmosphere is, for example, an atmosphere of 100 volume% ammonia (NH ₃ ) gas, or an ammonia (NH ₃ ) content rate of 70 volume% or more and less than 100 volume% ammonia (NH ₃ ) +. A nitrogen (N ₂ ) mixed gas atmosphere can be used.

According to the present invention, aluminum nitride powder can be directly obtained from boehmite powder without using a carbon-containing substance. Since the obtained aluminum nitride powder is carbon-less, a high-purity aluminum nitride powder product suitable for sintering can be obtained without going through a decarbonization process. Further, the aluminum nitride powder obtained by the present invention has a large specific surface area of, for example, 3 to 30 m ² / g, and has a higher sinterability than the conventional general aluminum nitride powder which is widely used for sintering.

3 is an SEM photograph of the raw material powder used in Example 1. The X-ray-diffraction pattern of the raw material powder used in Example 1. The X-ray-diffraction pattern of the powder after baking obtained in Example 1. 5 is an SEM photograph of the powder after firing obtained in Example 2. The X-ray-diffraction pattern of the powder after baking obtained in Example 2. 5 is an SEM photograph of the raw material powder used in Example 3. The X-ray-diffraction pattern of the raw material powder used in Example 3. 5 is an SEM photograph of the powder after firing obtained in Example 3. The X-ray-diffraction pattern of the powder after baking obtained in Example 3. The X-ray-diffraction pattern of the powder after baking obtained in Comparative Example 1. The X-ray-diffraction pattern of the powder after baking obtained in Comparative Example 2. The X-ray-diffraction pattern of the powder after baking obtained in Comparative Example 3. The X-ray-diffraction pattern of the raw material powder used in the comparative example 4. The X-ray-diffraction pattern of the powder after baking obtained in Comparative Example 4. The X-ray-diffraction pattern of the powder after baking obtained in Example 4. The X-ray-diffraction pattern of the powder after baking obtained in Comparative Example 5.

[Boehmite powder raw material]
In the present invention, a boehmite (AlOOH) powder having a BET specific surface area of 150 m ² / g or more is used. According to the study by the inventors, such a fine boehmite powder having a large specific surface area is obtained by heat treatment in a non-oxidizing atmosphere gas using ammonia gas without using a carbon-containing substance. Can be changed to powder. The BET specific surface area is more preferably 180 m ² / g or more, and more preferably 250 m ² / g or more. However, the boehmite powder having an excessively large specific surface area causes an increase in manufacturing cost and a decrease in storage and handleability. The raw material applied to the present invention may have a BET specific surface area of 500 m ² / g or less, for example.

  The boehmite powder used in the present invention needs to have good crystallinity. Specifically, in an X-ray diffraction pattern at room temperature measured using Cu-Kα rays, in the region where the diffraction angle 2θ is 10 to 40 °, (A) around 14.5 °, (B) in order from the low angle side. ) 28.2 ° and (C) 38.3 ° have diffraction peaks, and the peak heights of A to C are highest in the order of A> B> C, and C is the highest. The powder having the lowest X-ray diffraction pattern peculiar to the boehmite crystal is applied.

  Such boehmite powder can be synthesized by a wet neutralization reaction step in which a water-soluble aluminum salt that exhibits acidity when dissolved in water is added to a basic aqueous solution to form and grow nuclei of aluminum oxyhydroxide. it can. At that time, the addition of the aluminum salt to the basic aqueous solution is divided into a first addition step performed under conditions suitable for nucleation and a second addition step for advancing nucleus growth (crystal growth), By applying the method of performing sequentially, the above-mentioned boehmite powder having good crystallinity and a large specific surface area can be stably produced. As in the conventional method, a method of producing a neutralized precipitate by mixing a water-soluble aluminum salt that shows acidity when dissolved in water and a basic substance that is a neutralizing agent at one time Of aluminum oxyhydroxide (pseudoboehmite) having a low specificity is easily generated, and it is difficult to industrially stably obtain a boehmite powder having a large specific surface area.

  In the wet process of obtaining boehmite powder, ammonia water, sodium hydroxide aqueous solution, sodium carbonate aqueous solution or the like can be applied as the basic aqueous solution which is a neutralizing agent. Of these, the use of ammonia water containing no alkali metal has the advantage that the alkali metal does not adhere to the boehmite that is precipitated by neutralization.

  As the aluminum salt that is the source of Al, a water-soluble aluminum salt that exhibits acidity when dissolved in water, such as aluminum sulfate (sulfuric acid band) and aluminum nitrate, can be used. It is desirable to add these substances as an aqueous solution. The Al concentration in the aqueous solution can be, for example, in the range of 0.01 to 1.00 mol / L, and more preferably in the range of 0.05 to 0.50 mol / L.

  The liquid temperature during the wet reaction step is preferably lower than 100 ° C, more preferably 60 ° C or higher and 95 ° C or lower.

The procedure for producing boehmite powder will be illustrated below.
A basic aqueous solution, which is a neutralizing agent, is prepared in the reaction vessel, and the liquid temperature is maintained at the above reaction temperature.
In the first addition step of the aluminum salt, an amount of the aluminum salt which maintains the OH / Al ratio in the liquid in the range of, for example, 3 to 600, preferably 5 to 500 is added to the basic aqueous solution with stirring. The time from the start of addition to the end of addition can be, for example, 1 to 60 seconds, preferably 1 to 30 seconds. After the addition is completed, the stirring state is continued. This first addition step is a process in which a small amount of aluminum salt is added under stirring to generate as many nuclei as neutralized precipitates (aluminum oxyhydroxide). When the addition amount of the aluminum salt in the first addition step is too large, the added aluminum salt is consumed for the growth of the already formed nuclei, and it becomes difficult to obtain fine boehmite powder having a large specific surface area. Further, it is important to perform sufficient stirring from the viewpoint of forming as many nuclei as possible.

  In the second addition step of the aluminum salt, the addition of the aluminum salt is started when, for example, 5 minutes or more has elapsed from the end of the addition in the first addition step, and the OH / Al ratio in the liquid is the first addition step. The aluminum salt is added in an agitated state in an amount of, for example, in the range of 3 to 6 in terms of accumulation. The time from the start of addition to the end of addition in the second addition step can be, for example, 10 to 180 minutes. This second addition step is a process of growing the nuclei of the neutralized precipitate (aluminum oxyhydroxide) that has already been generated, and synthesizing particles composed of boehmite crystals. It is extremely important to obtain a powder composed of fine boehmite particles by waiting until the reaction for nucleation has sufficiently progressed and then starting the addition of the aluminum salt in the second addition step. This waiting time (the time from the end of the addition in the first addition step to the disclosure of the addition in the second addition step) is referred to herein as an "interval". If the interval is too short, the particles tend to become coarse. It is also desirable to continue stirring the liquid during the interval.

  After the second addition step of the aluminum salt is completed, it is desirable to maintain the stirring state while keeping the liquid temperature in the above range. This process is effective in homogenizing the particle size distribution due to the phenomenon that small particles dissolve and re-precipitate on the surface of large particles (Ostwald ripening). This process is referred to herein as the "ripening process". The time required for the aging process, specifically, the time required from the end of the addition of the aluminum salt in the second addition step to the end of the stirring before the first solid-liquid separation is preferably 60 to 180 minutes, for example.

After that, solid-liquid separation is performed by a technique such as filtration to recover the solid content, and washing and drying steps are performed to obtain a boehmite (AlOOH) powder having a specific surface area of 150 m ² / g or more by the BET one-point method. Obtainable.

[Production of aluminum nitride powder]
In the present invention, the aluminum nitride (AlN) powder is obtained by heat-treating the above boehmite powder having a large specific surface area in a non-oxidizing atmosphere containing ammonia (NH ₃ ). At that time, the reaction is allowed to proceed without using the carbon-containing substance.

The ammonia (NH ₃ ) -containing non-oxidizing atmosphere is, for example, an ammonia (NH ₃ ) gas atmosphere, or the ammonia (NH ₃ ) content is 70% by volume or more and less than 100% by volume, and the balance is nitrogen (N ₂ ). A mixed gas of ammonia (NH ₃ ) and nitrogen (N ₂ ) can be exemplified. In the case of an ammonia (NH ₃ ) + nitrogen (N ₂ ) mixed gas, the ammonia (NH ₃ ) content is more preferably 75 to 95% by volume. The heat treatment temperature at which the AlN formation reaction proceeds can be 1200 to 1600 ° C, and more preferably 1300 to 1550 ° C. This heat treatment is called "baking" in this specification.

  The firing is performed by accommodating the raw material powder in a furnace having a structure in which the atmosphere does not enter, maintaining the furnace atmosphere in a predetermined non-oxidizing atmosphere containing ammonia, and raising the powder temperature in the furnace to the above predetermined range. You can The pressure in the furnace may be atmospheric pressure. During the heat treatment, in order to maintain the atmospheric gas composition in the furnace within a certain range, it is desirable to ventilate an ammonia-containing gas supplied from the outside into the furnace and expose the powder to the gas stream of the vent gas. It is desirable that the powder be contained in the furnace in a state of being deposited as thinly as possible so that individual particles can easily come into contact with the atmospheric gas component. For example, when the powder is deposited on the tray and the tray is placed in the furnace, the thickness of the powder deposited on the tray is preferably 5 mm or less.

As for the firing time, a time sufficient for all of the raw material boehmite powder contained in the furnace to change into aluminum nitride (AlN) is secured. The specific surface area of the raw material powder, the firing temperature, ambient gas composition, the time required for firing by deposition state of a powder to be accommodated in the furnace are different, for example, a BET specific surface area of the boehmite powder of about 180~300m ² / g ammonia (NH ₃ ) When heating to 1200 to 1600 ° C. in a non-oxidizing atmosphere having a content of 70 to 100% by volume, it is usually within a range of 2 to 10 hours, and more preferably within a range of 4 to 8 hours. You can set the time.

In this way, an AlN single-phase aluminum nitride powder product can be obtained. The AlN single-phase aluminum nitride powder referred to here is an Al-containing compound phase other than AlN in which an X-ray diffraction pattern peculiar to AlN is observed in X-ray diffraction (XRD) at room temperature using Cu-Kα rays. (For example, AlOOH, γ-Al ₂ O ₃ , α-Al ₂ O ₃ , AlON) means that the peak of the diffraction pattern is not observed.
This aluminum nitride powder is composed of extremely fine particles having a BET specific surface area of, for example, about 3 to 30 m ² / g and is excellent in sinterability. Further, since the powder is calcined without using a carbon-containing substance, the carbon content in the powder is extremely small, for example, 0.1% by mass or less, and it can be applied to various uses without being subjected to decarbonization treatment. .

<< Example 1 >>
[Production of raw material powder]
Ammonia water having a concentration of 26 mass% was prepared. This is solution A.
Pure water was added to an aqueous solution of aluminum sulfate (manufactured by Asada Chemical Industry Co., Ltd.) to prepare a solution having an aluminum sulfate concentration of 4 mass%. This is referred to as solution B.

3223.3 g of pure water was placed in a reaction vessel having a stirring mechanism, 196.5 g of solution A as a neutralizing agent was added thereto, and the liquid temperature was raised to 90 ° C. While maintaining the liquid in the reaction vessel under stirring and maintaining the liquid temperature at 90 ° C., the solution B in an amount such that the OH / Al molar ratio in the liquid is 16.7 is added to the liquid in the reaction vessel for about 7 seconds. Added (first addition step). Here, the value of OH in the above OH / Al molar ratio means a value (equivalent value) equal to the number of moles of ammonia (NH ₃ ) dissolved in the liquid, and is actually ionized according to chemical equilibrium. It does not mean the number of moles of hydroxide ion OH ⁻ (the same in each of the following examples).

  After the completion of the addition of the solution B in the first addition step, 10 minutes after the stirring and the liquid temperature were maintained at 90 ° C, the cumulative OH in the liquid in the reaction vessel was maintained while the stirring and the liquid temperature were maintained at 90 ° C. Solution B in an amount such that the / Al molar ratio was 5.0 was added to the liquid in the reaction vessel over 18 minutes (second addition step). That is, the OH / Al molar ratio in the liquid after the completion of the second addition step was adjusted to 5.0. The time from the end of the addition of solution B in the first addition step to the start of addition of solution B in the second addition step is called "interval time". The interval time in this example is 10 minutes as described above.

  After the completion of the addition of the solution B in the second addition step, the stirring and the state of maintaining the liquid temperature of 90 ° C. are maintained for 60 minutes, then cooling is started, and the stirring is performed when the temperature is lowered to about 65 ° C. over 60 minutes. After that, solid-liquid separation was performed by filtration using a Buchner funnel and an aspirator, and the solid content was collected. The time required from the end of the addition of the liquid B in the second addition step to the end of the stirring before the solid-liquid separation is referred to as "aging time". The aging time in this example is 120 minutes, which is 60 minutes of holding at 90 ° C. and 60 minutes from the start of cooling to the end of stirring. The recovered solid content was washed with water and dried to obtain a raw material powder.

FIG. 1 illustrates an SEM photograph of the obtained raw material powder. The specific surface area of this raw material powder was measured by the BET one-point method using Macsorb manufactured by MOUNTECH. As a result, the BET specific surface area of the powder was 286 m ² / g.

  With respect to this raw material powder, an X-ray diffraction pattern by Cu-Kα ray was measured under the conditions of a tube voltage of 40 kV and a tube current of 15 mA using XtabLABmin manufactured by Rigaku. The X-ray diffraction pattern is shown in FIG. In the region where the diffraction angle 2θ is 10 to 40 °, there are diffraction peaks in the order of (A) 14.5 °, (B) 28.2 °, and (C) 38.3 ° from the low angle side. The peak heights of these peaks are higher in the order of (A)> (B)> (C), which is an X-ray diffraction pattern peculiar to boehmite crystals. That is, it is understood that the raw material powder obtained in this example is a boehmite powder having good crystallinity.

[Firing]
The raw material powder was placed on an alumina tray, and the tray was placed in a tubular furnace made of alumina with the tray in a substantially horizontal state. The maximum deposition thickness of the raw material powder placed on the tray is about 5 mm. The tubular furnace has a gas inlet at one end and a gas outlet at the other end, and has a structure capable of shielding the atmosphere from the atmosphere. In addition, a heating element is provided on the outer peripheral portion of the alumina tube to heat the inside of the tube. The ammonia-containing non-oxidizing gas is continuously introduced into the furnace through the gas inlet, and the gas in the furnace is discharged through the gas outlet, so that the ammonia-containing non-oxidizing gas flows inside the tubular furnace. Was prepared, and the surface of the raw material powder placed on the tray was exposed to the air flow. The pressure in the furnace is almost atmospheric pressure. The composition of the ammonia-containing non-oxidizing gas introduced into the furnace, ammonia (NH ₃₎ 80 vol%, and nitrogen (N ₂₎ ammonia consisting of 20 vol% (NH ₃₎ + nitrogen (N ₂₎ gas mixture. The firing was carried out under the condition that the powder was kept at 1235 ° C. for 8 hours while flowing the non-oxidizing gas.

The X-ray diffraction pattern by Cu-Kα ray was measured for the powder after firing.
The X-ray diffraction pattern of the powder after firing shown in this specification was measured under any of the following conditions.
A condition of a tube voltage of 40 kV and a tube current of 15 mA according to XtabLABmin manufactured by Rigaku (hereinafter referred to as condition A).
A condition of a tube voltage of 40 kV and a tube current of 30 mA according to RINT2000 manufactured by Rigaku (hereinafter, referred to as condition B).
In this example, the X-ray diffraction pattern measured under the condition A is illustrated in FIG. It was confirmed that the powder after firing was composed of an aluminum nitride (AlN) single phase.
The BET specific surface area of this powder was 29 m ² / g.

<< Example 2 >>
An experiment was conducted under the same conditions as in Example 1 except that the firing conditions in Example 1 were such that the firing conditions were held at 1335 ° C. for 4 hours.
FIG. 4 illustrates an SEM photograph of the powder after firing.
FIG. 5 illustrates an X-ray diffraction pattern (according to condition B) of the powder after firing. It was confirmed that this powder was composed of an aluminum nitride (AlN) single phase.
The BET specific surface area of the powder after firing was 23 m ² / g. Moreover, when the carbon content of this powder was measured by the high frequency furnace combustion-infrared absorption method, the carbon content was 0.08 mass%.

<< Example 3 >>
[Production of raw material powder]
In the first addition step, solution B in an amount such that the OH / Al molar ratio in the liquid in the reaction vessel is 133.3 is added to the liquid in the reaction vessel over about 5 seconds, and In the addition step of Example 1, except that the solution B in an amount such that the cumulative OH / Al molar ratio in the liquid in the reaction vessel was 5.0 was added to the liquid in the reaction vessel over 60 minutes. Raw material powders were produced under the same conditions, and the same method as in Example 1 was investigated.

FIG. 6 illustrates an SEM photograph of the obtained raw material powder. The BET specific surface area of this powder was 198 m ² / g.
FIG. 7 shows an X-ray diffraction pattern of this raw material powder. As in Example 1, it can be seen that the raw material powder obtained in this example is a boehmite powder having good crystallinity.

[Firing]
Firing was performed under the same conditions as in Example 1 except that the condition was maintained at 1550 ° C. for 4 hours. The obtained powder was investigated in the same manner as in Example 1.
FIG. 8 illustrates an SEM photograph of the powder after firing.
FIG. 9 illustrates an X-ray diffraction pattern (according to condition A) of this powder. It was confirmed that this powder was composed of an aluminum nitride (AlN) single phase.
The BET specific surface area of the powder after firing was 6 m ² / g.

<< Example 4 >>
Composition ammonia (NH ₃₎ 95 volume% of the ammonia-containing non-oxidizing gas introduced into the furnace in the first embodiment, nitrogen (N ₂₎ ammonia consisting of 5 vol% (NH ₃₎ + nitrogen (N ₂₎ gas mixture Then, the experiment was conducted under the same conditions as in Example 1 except that the firing conditions were such that the firing conditions were held at 1335 ° C. for 4 hours.
FIG. 15 illustrates an X-ray diffraction pattern (under condition A) of the powder after firing. It was confirmed that this powder was composed of an aluminum nitride (AlN) single phase.

<< Comparative Example 1 >>
An experiment was conducted under the same conditions as in Example 1 except that the firing conditions in Example 1 were such that the firing conditions were held at 1135 ° C. for 4 hours.
FIG. 10 illustrates an X-ray diffraction pattern (according to the condition B) of the powder after firing. This powder is mainly composed of aluminum nitride (AlN), but an increase in strength due to a phase different from that of the AlN crystal is observed at the location indicated by the arrow in the figure. This increase in strength suggests the presence of γ-Al ₂ O ₃ . That is, in this example, since the firing temperature was low, the powder consisting of the aluminum nitride (AlN) single phase could not be obtained by firing for 4 hours.

<< Comparative example 2 >>
An experiment was conducted under the same conditions as in Example 1 except that the firing time in Example 1 was shortened from 8 hours to 4 hours. That is, the firing condition of this example is 1235 ° C. × 4 hours.
FIG. 11 illustrates an X-ray diffraction pattern (according to condition B) of the powder after firing. A peak due to α-Al ₂ O ₃ is seen at the location indicated by the arrow in the figure. The firing temperature was the same as in Example 1, but the firing time was insufficient, and thus a powder consisting of an aluminum nitride (AlN) single phase could not be obtained.

<< Comparative Example 3 >>
An experiment was conducted under the same conditions as in Example 2 except that the firing time in Example 2 was shortened from 4 hours to 2 hours. That is, the firing condition of this example is 1335 ° C. × 2 hours.
FIG. 12 illustrates an X-ray diffraction pattern (according to condition B) of the powder after firing. A peak due to α-Al ₂ O ₃ is seen at the location indicated by the arrow in the figure. The firing temperature was the same as in Example 2, but the firing time was insufficient, and thus a powder consisting of an aluminum nitride (AlN) single phase could not be obtained.

<< Comparative Example 4 >>
[Production of raw material powder]
Solution A (ammonia water) and solution B (aluminum sulfate aqueous solution) similar to those in Example 1 were prepared.
2585.3 g of pure water was put into a reaction vessel having a stirring mechanism, 162.4 g of solution A as a neutralizing agent was added thereto, and the liquid temperature was raised to 60 ° C. While stirring the liquid in the reaction container and maintaining the liquid temperature at 60 ° C., the solution B in an amount such that the OH / Al molar ratio in the liquid is 3.1 is added to the liquid in the reaction container for about 30 seconds. Added. Then, after securing the above-mentioned aging time for 15 minutes, solid-liquid separation, water washing and drying were carried out in the same manner as in Example 1 to obtain a raw material powder. That is, in this example, the addition of the solution B was performed in one step without being divided into two addition steps.
FIG. 13 shows the X-ray diffraction pattern of this raw material powder. Since no diffraction peak is seen at a diffraction angle 2θ of around 14.5 °, this raw material powder is not identified as a boehmite powder having good crystallinity. The BET specific surface area of this powder was 0.98 m ² / g.

[Firing]
The raw material powder obtained by the above method was fired under the same conditions as in Example 1 except that the condition was maintained at 1550 ° C. for 8 hours.
FIG. 14 illustrates an X-ray diffraction pattern (according to condition A) of the powder after firing. A peak due to α-Al ₂ O ₃ is seen at the location indicated by the arrow in the figure. In this example, which did not use a high specific surface area boehmite powder having good crystallinity as a raw material, a powder consisting of an aluminum nitride (AlN) single phase was obtained only by firing in a non-oxidizing atmosphere containing ammonia. I couldn't do it.

<< Comparative Example 5 >>
The composition of the ammonia-containing non-oxidizing gas to be introduced into the furnace in Example 1 is ammonia (NH ₃ ) 50% by volume and nitrogen (N ₂ ) 50% by volume ammonia (NH ₃ ) + nitrogen (N ₂ ) mixed gas. Then, the experiment was conducted under the same conditions as in Example 1 except that the firing conditions were such that the firing conditions were held at 1335 ° C. for 4 hours.
FIG. 16 illustrates an X-ray diffraction pattern (under condition A) of the powder after firing. In the X-ray diffraction pattern of the powder after firing, a peak attributed to α-Al ₂ O ₃ was found at the location indicated by the arrow in the figure. In this example, since the atmosphere gas having a low ammonia content rate was used at the time of firing, the powder consisting of the aluminum nitride (AlN) single phase could not be obtained.

Claims (4)

The BET specific surface area is 150 m ² / g or more, and in the X-ray diffraction by Cu-Kα ray, in the region of the diffraction angle 2θ of 10 to 40 °, in order from the low angle side, (A) around 14.5 °, (B) ) X-rays having diffraction peaks near 28.2 ° and (C) 38.3 ° and having the highest peak height of A and the lowest peak height of C among the diffraction peaks of A to C above. Boehmite (AlOOH) powder exhibiting a diffraction pattern is heated and held at 1200 to 1600 ° C. in a non-oxidizing atmosphere having an ammonia (NH ₃ ) content of 70 to 100% by volume , without using a carbon-containing substance , A method for producing an aluminum nitride powder, wherein all of the boehmite is changed to aluminum nitride (AlN). The BET specific surface area is 150 m ² / g or more, and in the X-ray diffraction by Cu-Kα ray, in the region of the diffraction angle 2θ of 10 to 40 °, in order from the low angle side, (A) around 14.5 °, (B) ) X-rays having diffraction peaks near 28.2 ° and (C) 38.3 ° and having the highest peak height of A and the lowest peak height of C among the diffraction peaks of A to C above. Boehmite (AlOOH) powder exhibiting a diffraction pattern is heated and held at 1200 to 1600 ° C. in a non-oxidizing atmosphere having an ammonia (NH ₃ ) content of 70 to 100% by volume , without using a carbon-containing substance , A method for producing an aluminum nitride powder, wherein an aluminum nitride single-phase powder is obtained by converting all of the boehmite into aluminum nitride (AlN). The BET specific surface area is 150 m ² / g or more, and in the X-ray diffraction by Cu-Kα ray, in the region of the diffraction angle 2θ of 10 to 40 °, in order from the low angle side, (A) around 14.5 °, (B) ) X-rays having diffraction peaks near 28.2 ° and (C) 38.3 ° and having the highest peak height of A and the lowest peak height of C among the diffraction peaks of A to C above. Boehmite (AlOOH) powder exhibiting a diffraction pattern is heated and held at 1200 to 1600 ° C. in a non-oxidizing atmosphere having an ammonia (NH ₃ ) content of 70 to 100% by volume , without using a carbon-containing substance , A method for producing an aluminum nitride powder, wherein an aluminum nitride single-phase powder having a carbon content of 0.10 mass% or less is obtained by changing all of the boehmite into aluminum nitride (AlN). The non-oxidizing atmosphere, ammonia (NH ₃₎ content of 70 vol% or more and 100% by volume less than ammonia (NH ₃₎ + nitrogen (N ₂₎ mixture is a gas atmosphere in any one of claims 1 to 3 A method for producing the aluminum nitride powder described.