JPS62100405A - Aluminium nitride powder and production thereof - Google Patents

Abstract

PURPOSE:To produce AlN powder having a specified compsn., specified characteristics, and superior sinterability by gelling a mixture of pseudoboehmite having specified characteristics with carbon powder in an appropriate proportion, then calcining the gelled product at a specified temp. in N2-contg. atmosphere. CONSTITUTION:Pseudoboehmite contg. >=99.98wt% Al2O3 and <=16ppm (basing on the amt. of Al2O3) Si, and having 150-450m<2>/g specific surface area is mixed with carbon contg. <=0.03wt% ash and <=40ppm Si and having >=50m<2>/g specific surface area and <=1.0mum mean particle size in a proportion by weight of 1:0.36-0.70 Al2O3/C in the presence of water. Then, the above-described pseudoboehmite is gelled and calcined at 1,350-1,650 deg.C in N2-contg. atmosphere. By this method, AlN powder having <=3.0mum mean particle size, <=2.5% O content and <=0.05% metallic impurities other than Al, <=20ppm Si, and >=32.3% N is obtd., which has at least two peaks of heat generation due to oxidation at 1,170-1,200 deg.C and 1,190-1,225 deg.C in the differential thermal analysis in the atmospheric air.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a novel nitrogen hyaluminum powder and a method for producing the same.

(Prior Art) There are two representative methods of synthesizing aluminum nitride (HTP) powder known in the art.

0) A method of nitriding metallic aluminum (Al) with nitrogen or ammonia gas.

('!-) rIR ratio aluminum l, 0. ) and carbon powder mixture in nitrogen or ammonia gas.

AlN is theoretically so W7m. It has a high thermal conductivity comparable to that of beryllium (BeO) and has excellent electrical properties such as insulation and dielectricity, so it is a semiconductor that is becoming more and more powerful and highly integrated. It is attracting a lot of attention as an insulating heat dissipation board material.2)

However, the AJ! The thermal conductivity of N sintered bodies has been tested in practical use and is at most 2 of the theoretical value.
Currently, it is about O4. This is due to the fact that this L Fi & sintered body contains pores and impurities that impede heat conduction.Therefore, the development of an AlN powder raw material with excellent purity and sinterability is awaited. bl.

In method (2), the purity of Al directly influences the purity of AIN. In reality, Al contains many impurities in the sound range, and as a result, there are many impurities in the AlN powder. - Also, in method ■, to increase the bet rate of 1 hit, %
Also, contamination of impurities is unavoidable in both the step of pulverizing the raw material Al and the step of pulverizing the produced AlN raw material into powder for the total sintering. Since the reaction is carried out above the melting point of Al, AlN is produced only on the 5th surface, and unreacted Al tends to remain very easily.

According to method (2), fcAl with relatively fine grain size
Although it is possible to synthesize N powder gold, it is difficult to perform a complete nitrogen reaction, and it has the disadvantage that unreacted Al particles tend to remain.This is because the Al particles used as raw materials are large. Even some bVi fine grains of AmO1 are very difficult to mix uniformly with carbon.

In addition, the purity of the AlN powder obtained by the method (■) is as follows:
0. % also depends on the purity of both carbon and carbon. AlN
The particle size of the powder is also 0. Depends on. Therefore, if you want to obtain high-purity, fine-grained AlN powder using method (2), use AA0. and carbon must be of high purity and fine particles, and their mixture must be
A high degree of uniformity is required and is extremely difficult in practice.

(Problems to be Solved by the Invention) One of the reasons for the low thermal conductivity and large volume of currently obtained htN@ bodies is in the AlN@ powder used for sintering. be. 11th Ha A1. The second problem is that the oxygen content in the N powder is high, the second problem is that the sinterability of the Ti powder is poor, and the fifth problem is that the amount of impurities in the AlN powder is high. Therefore.

These are the points that the present invention seeks to solve.

(Means for solving the problems) The present inventors have conducted intensive research on these problems and found that the Al, N sintered t4 tank has dramatically improved thermal conductivity compared to the conventional method. The resulting AlN powder was produced. That is, the AlN powder of the present invention has an average particle diameter of 6.0 μm.
Hereinafter, the oxygen-containing lid is 2.5 μm or less, the metal impurity content excluding Al is 0.05 μm or less, the St-containing lid is 20 μm or less, and the nitrogen-containing sound is 32 μm or less. In the differential thermal analysis of AlN powder, the Si is 1% or more, and the wave f
The exothermic peak due to VC is at least 1170-1241
This is an AlN powder characterized by its presence at two locations: 01:l' and 1190-1225C.

In addition, the method for producing AlN powder of the present invention has A60. is 99.9fl Illustrated or above, A40
．． Pseudo-boehmite with an Sj content of 16 p% or less and a specific surface area of 150 to 450 nt/l"c, an ash content of 0.05 nt/l"c or less, a Si content of 40 m or less, and a specific surface area of 50 nt/l"c. After mixing carbon kb Al40m and carbon with a heavy violet ratio of i:o, s6 to 1:0.70 in the presence of water, with an average particle size of 1.0 μm or less, pseudo-boehmite It consists of firing at 1,650 to 1,650 C in an atmosphere containing nitrogen, compared to gold gel.

Ethylene chlorohydrin, globin chlorohydrin, dichlorohydrin, trimethylene chlorohydrin, carbon dioxide in alkaline aluminate solution.

61. Pseudo-boehmite obtained by adding a mixture of one or more citrons selected from the group of formic acid, ammonium sulfate, ammonium nitrate, and ammonium chloride, or S
Pseudo-boehmite obtained by hydrolyzing aluminum alkoxide with a low content of i is suitable. The carbon to be used is 4OL1-1000 in an atmosphere containing chlorine, hydrogen chloride, or a mixture thereof.
Carbon heated with U is suitable.

Generally, AlN powder contains oxygen and metal impurities, which are said to completely reduce the thermal conductivity of the AlN sintered body. S taken up by the inventors
As for i, general AlN powder contains less than double cap, and even pure AlN powder contains slightly more than 100μ. Conventionally, regarding the action of Si in AAN, according to Japanese Patent Application Laid-Open No. 57-56384, A1. Si in N acts as ktNK during sintering, and KAlN-8i0. A1. N polytype phase (hereinafter referred to as “ALsIO
This AL8ION is said to form a 100% NJ sound and reduce the thermal conductivity of the sintered body.

A large amount of copper is produced by the Si component of Company 1a, for example.

o, 13% Si-containing male t14m, 5~I E
The formation of l-iiji*(1) ALSION results in the formation of a foreign phase 50 to 100 times the Si content.

For this reason, in the past, the thermal conductivity of AlN sintered bodies?
I: ^^ As disclosed in Japanese Patent Application Laid-Open No. 56-65878 and Japanese Patent Application Laid-Open No. 57-56584, &C, 8i.

Oxygen, @ specific magnesium added to total AlH and ALSIO
By suppressing the generation of N and obtaining a dense sintered body]
In an attempt to improve the thermal conductivity of the sintered body, the thermal conductivity of the sintered body obtained by these methods is compared to the theoretical thermal conductivity of AlN. It was still quite low.

The inventors of the present invention have discovered the following: Si-containing lid in AlN powder.

As a result of examining the relationship between the thermal conductivity of the obtained sintered body, it was found that Al
9. The Si content in the N powder must be 20 ppm or less. It has been found that the thermal conductivity of the AlN sintered body is rapidly improved. At this time, the AlN sintered body must be in a very dense state, and no matter how small the amount of Si it contains, unless a dense sintered body is obtained, high thermal conductivity cannot be obtained. In order to obtain a dense sintered body, the raw material AlN
The powder must have excellent fc sintering properties, and therefore, it was found that controlling the average particle size of the AlN powder is very important, and furthermore, it was found that controlling the average particle size of the AlN powder was very important. It is clear that the characteristics of the oxidation behavior at the time of fc are very closely related to the sinterability of the AlN powder.

91 A7 of the present invention. The N powder has an average particle diameter of 3.0 μm or less, preferably 1.0 to 2.5 μm, and an oxygen content of 2.5 μm or less, with a good casing and 0 weight 1 μm or less. Yes, the lid containing metal impurities excluding Al and gold is 0.03 weight or less, the good case structure is 0.03 or less, and the S
The content of t is 20 or less, preferably 15 or less, and the nitrogen-containing tri S 2,3 [1! t is 1 or more, preferably Fi is 33.0 wt. or more, and in differential thermal analysis of the A/N powder in the air, the exothermic peak due to oxidation is at least 1170 to 12 υOC and 1190 υOC.
~1225C Al characterized by being present in two places
It is N powder.

A1. having an average particle diameter of more than 3.0 μm. -1 for N powder,
The sinterability deteriorates, and a sufficiently dense sintered body cannot be obtained using the pressureless sintering method, and sintering is quite difficult even with sintering methods such as hot press, and the high pressure and high temperature It becomes necessary. First, regarding metal impurities, metal impurities excluding Al @
When 1k exceeds 0.05 violet, the content of Si, which is preferable to reduce the thermal conductivity of the A4N sintered body, must be 20 F or more, and this content value is If it exceeds this value, the thermal conductivity of the AlN sintered body decreases rapidly. The cause of this is thought to be related to the amount of ALSION generated as described above.

The nitrogen content value is related to the purity of AlN, and is 32.5 fold j! If it is less than tLs, the purity of AlN will be low, and the thermal conductivity of the AlN sintered body will be low.

Furthermore, the AlN powder of the present invention is characterized by: A remarkable exothermic peak due to oxidation observed in differential thermal analysis of AlN powder in the atmosphere.

In the differential thermal analysis of the AlN powder of the present invention in the air, the exothermic peak due to the oxidation of the powder consists of at least two peaks, as shown in Figures 5 and 6, and one exothermic peak. is present at 1170-1zooc, and another exothermic peak is present at 1190-1225G. In addition, the temperature of the exothermic peak according to the present invention is as follows.

These values were measured using a differential thermal balance manufactured by Shinku Riko Co., Ltd., Model TGD-5000, at a heating rate of 10 C/m while flowing dry fi air at 50 α/m.

For A4N powder whose exothermic peak due to oxidation is outside the above-mentioned temperature range, the sinterability of the powder is poor and a dense AlN sintered body cannot be obtained, and the temperature of this exothermic peak and the AlN powder are For more details on the relationship between sinterability and sinterability, please refer to the following.

It seems that h is related to the size of the primary particles of the AlN powder. In other words, the average particle diameter measured with a particle size distribution needle is 1. In the normal case, the size of the aggregated particles is measured by iF! This value is larger than the size of primary particles observed with a submicroscope. - When AlN powder is oxidized, its oxidation behavior is considered to be more closely related to the size of the primary particles and the particle size distribution of the primary particles than to the agglomeration state of the powder.

In addition, the size of the -order particles and the particle size distribution of the primary particles are
This seems to be related to the sinterability of the powder, so the result is A1. It seems that the oxidation behavior of N powder is deeply related to its sinterability. The AlN powder of the present invention is an AlN powder that has two or more sharp exothermic peaks 1 that have not been seen in the past in differential thermal analysis, and has very good sinterability.

Next, a method for producing AlN powder according to the present invention will be described. #'i as raw material, AJ in terms of oxide! , Os is 99
．． 98 heavy lids or more, and A40. The content of Si relative to K is 16 pIm or less, and the specific surface area is 150 to 450 Go/
Pseudo-boehmite which is l, ash content, 03 weight - or less,
A carbon sound having a Si content of 4 Qpps or less, a specific surface area of 50 weight or more, and an average particle diameter of 1.0 μm or less is used. A part of 8i in pseudoboehmite and carbon evaporates in the form of SiO during AlN powder synthesis, but
The residue is mixed into the AlN powder. Regarding 8i K, as mentioned above, during sintering of AlN, an A4N polytype phase consisting of a MuAN 810-based compound is formed in the sintered body by acting on MutN, and the thermal conductivity of the AlN sintered body is This causes a decrease in Therefore.

In the present invention, pseudo-boehmite and carbon with a low Si content must be used.

The solidified boehmite used in the present invention has an A^0.
is 99.98 weight or more and A40. The content of Si must be 16 or less, and if it falls outside this range, the amount of impurities in the AlN powder will increase, which is undesirable.
50-450 d/1! For books that fall outside of this range, it is difficult to gel after mixing with carbon and when performing a gel ratio, which is undesirable. must be 1.0 μm or less, and the specific surface area is 50 ≠ the primary particle size is large, and the 16 N-forming membranes are completed and the average particle size is 1.0 μm'ft. If it exceeds the range, it will not be possible to mix sufficiently uniformly, and the ruminability of the mu, O, and carbon will deteriorate.

Since the pseudo-boehmite used in the present invention is mixed with carbon and gelled, it is preferable to use one that is easily gelled. (from the group of pyrene chlorohydrin, dichlorohydrin, trimethylene chlorohydrin, carbon dioxide, acetic acid, formic acid, ammonium sulfate, ammonium nitrate, ammonium chloride) S is included - 14 = total addition of 1 or more mixtures How to get it.

A method of obtaining the solution by hydrolyzing aluminum alkoxide with a low Sl content is preferable. Pseudo-boehmite obtained by these methods has few impurities, especially Si, and
It is a pseudo-boehmite that easily gels and is suitable for the synthesis of the AlN powder of the present invention.

As for carbon, Si with a-acicularity of 40 to 1 or less is also used. 2 In the case where a carbon source with St of 40- or less is not available, in the present invention, carbon t-#
Heating is performed at 400 to 1000 C in an atmosphere containing an X-ray or a mixed gas of hydrogen chloride or 7N. By this, the content of Si in carbon can be reduced, and carbon suitable for the present invention can be obtained.

Pseudo-boehmite and carbon may be mixed by either dry mixing or wet mixing, but water and gold must coexist before performing the gelling operation.

Pseudo-boehmite, carbon, and water are all mixed to form a slurry, and an acid such as nitric acid or hydrochloric acid is added thereto to gel the pseudo-boehmite.

The effect of gelation is that the aggregation of pseudo-boehmite is broken.

It is to be dispersed in the primary particles before and after tooX, come into microscopic contact with carbon, and not be separated from carbon during subsequent drying. Sura I of a mixture of counterfeit boehmite and carbon
J-fL:W1. While stirring, acid is gradually added, and the gel ratio of the pseudo-boehmite increases gradually, and carbon is uniformly dispersed in the gelled pseudo-boehmite.

The present invention is based on the conventional synthesis method of AlN powder, namely h
*2t0. compared to the method of firing a mixture of ATOs particles and carbon particles. Since the mixture of carbon and carbon is extremely pressure-equalized, 7t is produced from pseudo-boehmite, AJ! ,0
#i, hl, The mixing amount of O and carbon is 1:0.56 to 1:0.7 in terms of weight ratio.

□If too much carbon is added, a large amount of unwarped carbon will remain during the AlN synthesis process, and aluminum particles will also be produced, which is not desirable.

Furthermore, if there are few carbon particles, Alom remains, and AlN single-phase powder cannot be obtained.

Mixture of pseudoboehmite and carbon at AlN synthesis temperature i*
10 m in an atmosphere where carbon is not oxidized.
The water in the mixture and the moisture generated from the pseudo-boehmite are volatilized at a temperature of 0.000C or less.

Thereafter, the temperature is raised to the MutN synthesis temperature. The temperature for AlN powder synthesis is 1650-1650C, and the temperature is 1650-1650C.
l 40 (1 to 1550 UT. At temperatures below 1350 C, the AlN production reaction does not proceed sufficiently, and the mum O
There are 8 remaining. At temperatures exceeding 1,650 Ut, the AlN production reaction proceeds satisfactorily.

Sintering between the generated AlN particles progresses, and as a result, the average particle diameter increases and sinterability deteriorates. The synthetic heavy atmosphere is a nitrogen-containing atmosphere5.Usually, pure nitrogen gas or a gas containing ammonia gas, etc. is suitable. It is recommended to supply it in a suitable manner.

(Example) The oxygen and nitrogen contents of the AlN powder in the present invention are #
Metal oxygen and nitrogen simultaneous analyzer EMGA-
2200, and the analysis of metal impurities other than Si in the AlN powder was carried out using a sequential multi-high frequency plasma emission spectrometer IC manufactured by Jarrell Ash Co., Ltd.
This was done with AP-57SMARKII. Analysis of Si in AlN powder was performed using MIB after melting AlN powder with alkali.
For 8iK in Aotomo, pseudo-boehmite and carbon, the pseudo-boehmite and carbon are extracted with IQOOC and the obtained O is extracted with nine Al.
,0. The ash content was analyzed in the same manner as the AlN powder.

The average particle diameter of the AlN powder and carbon was determined by particle size distribution micron Photozyder 8KA-50 manufactured by Seishin Enterprise Co., Ltd.
00 and isobutyl alcohol as a solvent by centrifugal sedimentation, and the average particle diameter was determined to be 501 diameter. The bulk density Fi of the AlN sintered body was determined by the Archimedes method using kerosene as a solvent. Thermal conduction vehicle Fi of AlN sintered body, fc, AlN
Identification of crystal phases of powder and pseudo-boehmite was carried out by Rigaku Denki (
The test was carried out using Geigerflex model D-90 manufactured by Co., Ltd.

Specific surface area of AlN powder, pseudoboehmite and carbon'
db It was determined by the BET method using Nl adsorption. AlN
Differential thermal analysis of powder is carried out using Shinku Rikosha's Separate Differential Thermal Scale Model TG.
The test was carried out using D-5000 at a heating rate of 10 C/m while flowing dry air at 500 c/m.

Example 1 Synthesized by reaction of sodium aluminium and ethylene chlorohydrin. Specific surface area is 220g/th A40. 9? , with 99 heavy lids.

And the content of the 8th ward is A40. Pseudo-boehmite l55f (moisture content 25-) with 7ppa against the average particle diameter of 0.7B+, naturalness of 0.01 heavy lid*, and Si-containing lid of 2
Carbon black 40f having a concentration of 0 Ppm and a specific surface area of 120 g/f was lightly mixed in the presence of water using a nylon pot and ball. after that.

While the mixed slurry was not being stirred, Johto #1 was slowly added to form a pseudo-Boehmey gel. Next, the gelled mixture was dried with 150U of fr:, transferred to a high-purity graphite flat plate, and heated at 800C while flowing 1 gt/ml of charcoal gas.
After holding at 150° C. for 2 hours, the mixture was heated and held at 150° C. for 6 hours. The above fired product was heated in air at 700G for 5 hours to remove all unreacted carbon.

The X-ray diffraction pattern of this powder shows only AlN.

No diffraction peak was observed for AIto. FIG. 1 shows the X-ray diffraction pattern of the pseudo-boehmite used, and FIG. 2 shows the X-ray diffraction pattern of the AlN powder synthesized according to the present invention.

[-Figure 5 shows the results of differential thermal analysis of 11 CAlN powder 1-
Ta. The average particle size of the obtained fcAlN powder was 1.55 μm.
The specific surface area was 3.7g/l. Table 1 shows the analytical values of impurities.
BN) and then fill it in a carbon mold with an inner diameter of 2011 m.
Hot press sintering was performed for 2 hours at cI/i. The bulk density of the sintered body is 3.26 fI(1), and the thermal conductivity at room temperature is 165 W/fn.

Example 2 As pseudo-boehmite, the specific surface area is 400 m''/f.

A40 in terms of oxide. is 99.99% by weight, and Si
The content of is 0. Use something that is 5 blue.

As carbon, the average particle size is 0.46 μm and the ash content is 0.
．． Except for using carbon black with a weight of 01, a Si content of 10-, and a specific surface area of 70 g/l, all
The same as in Example 1 was used. The results are shown in Table 11.

Example 5 Except that the synthesis temperature of AlN powder was 16ooc.

All <same as Example 1. The results are shown in Table 1.

Figure 6! The results of differential thermal analysis of IcAlN powder are shown below.
0 Example 4 Specific surface area as pseudo-boehmite is 5007711/t
In terms of b oxide, A Muro 1 is 99,98 weight -, and S
The content of t is Al40. Use one that has 8P.

As carbon, the average particle size is 0.41 μm% and the ash content is 0.
．． 02% by weight, and the Si content is 50% by weight.

All procedures were the same as in Example 1 except that carbon black having a specific surface area of 105/2 was used. Table 1 shows the results.
It was shown to.

Comparative example 1 As pseudo-boehmite, the specific surface area is 10 logos/f.

A60 in terms of oxide. is 99.93 weight attack and Si
The procedure was the same as in Example 1 except that a 20-containing lid was used. The results are shown in Table IK.

Comparative example 2 except that the synthesis temperature of AlN powder was 1700U.

All <same as Example 1. The results are shown in Table 1.

FIG. 7 shows the results of differential thermal analysis of AlN powder.

Comparative Example 5 Purity 99.99 heavy ji'1bcBk (D content 31 is 30
A60. with a 1FT average particle diameter of 0.32 μm. 20 tons of powder (crystalline phase is α phase only) and ash content of 0. Carbon black 10R having an average particle diameter of 0.55 μm was wet-mixed using a nylon ELL bottle and ethanol as a dispersion medium using an O8 lid. Transfer the mixture to a graphite flat plate.

N! 150 while supplying gas 6 t/raiyr
The mixture was heated at port C for 6 hours. The mixture in air at 700T:
: Heated for 5 hours to remove uncured carbon black. The X-ray diffraction pattern of this powder is as shown in Figure 4. In addition to the Al-N peak, there is also an unreflected peak of 1! A strong peak of 40° was observed. FIG. 5 shows the X-ray diffraction pattern of Al used at 0°.

(Effects of the Invention) The present invention provides an AlN powder with less impurities, especially less oxygen and 81-containing layers, and excellent sinterability.

It can be manufactured by a reductive nitriding method using pseudoboehmite and carbon. As a result, the aluminum tN sintered body obtained by sintering the AlN powder obtained in the present invention is
1.This book shows an extremely high thermal conductivity that has never been seen before. This has made it a material that can be used in future applications such as large-scale integrated circuits that require high thermal properties.

[Brief explanation of drawings]

Figure 1 shows the X-ray diffraction pattern of pseudo-boehmite 7 used in Example 1, and Figure 2 shows the X1iii! of Al and N powders synthesized in Example 1. Diffraction pattern, Figure 5 used in Comparative Example 5
'j A/! The X-ray diffraction pattern of 40s powder, FIG. 4, shows the uncurved Al synthesized in Comparative Example 3, 0. A containing
FIG. 5 shows the X-ray diffraction pattern of A1.l, N powder synthesized in Example 1. A graph showing differential thermal analysis results of N powder,
FIG. 6 is a graph showing the differential thermal analysis results of A& powder synthesized in Example 5, and FIG. 7 is a graph showing the results of differential thermal analysis of A& powder synthesized in Example 5, and FIG.
It is a graph showing the differential thermal analysis results of N powder. = 24- 1 & (@C) Figure 6 Figure 7 1 and (・C) Tekan & (@C)

Claims (4)

[Claims] (1) The average particle diameter is 3.0 μm or less, and the oxygen content is 2.0 μm or less.
5% by weight or less, content of metal impurities excluding Al is 0.0
5% by weight or less, and the Si content is 20ppm or less,
The nitrogen content is 32.3% by weight or more, and in differential thermal analysis of aluminum nitride powder in the air, exothermic peaks due to oxidation exist at at least two locations, 1170 to 1200°C and 1190 to 1225°C. Characteristic aluminum nitride powder. (2) The average particle diameter is 3.0 μm or less, and the oxygen content is 2.0 μm or less.
5% by weight or less, content of metal impurities excluding Al is 0.0
5% by weight or less, and the Si content is 20ppm or less,
Aluminum nitride having a nitrogen content of 32.3% by weight or more and exhibiting exothermic peaks due to oxidation at at least two locations, 1170 to 1200°C and 1190 to 1225°C, in differential thermal analysis of aluminum nitride powder in the air. In the powder manufacturing method, aluminum oxide is 99.98% by weight or more in terms of oxide, the Si content is 16 ppm or less relative to aluminum oxide, and the specific surface area is 15%.
Pseudo-boehmite with a density of 0 to 450m^2/g and an ash content of 0
．． 03% by weight or less, Si content is 40ppm or less, specific surface area is 50m^2/g or more, and average particle diameter is 1.0μ
After mixing carbon with a weight ratio of aluminum oxide and carbon of 1:0.36 to 1:0.70 in the presence of water, the pseudo-boehmite is gelled and mixed in an atmosphere containing nitrogen. A method for producing aluminum nitride powder, which comprises firing at a temperature of 1350 to 1650°C. (3) Pseudo-boehmite is added to an alkaline aluminate solution with ethylene chlorohydrin, propylene chlorohydrin, dichlorohydrin, trimethylene chlorohydrin, carbon dioxide, acetic acid, formic acid, ammonium sulfate, ammonium nitrate,
The claims are pseudo-boehmite obtained by adding one type or a mixture of two or more selected from the group of ammonium chlorides, or pseudo-boehmite obtained by hydrolyzing aluminum alkoxide with a low Si content. 2. The method for producing aluminum nitride powder according to item 2. (4) The method for producing aluminum nitride powder according to claim 2, wherein the carbon is carbon heated at 400 to 1000°C in an atmosphere containing chlorine, hydrogen chloride, or a mixed gas thereof.