JPS63277572A - Production of sintered aluminum nitride - Google Patents

Abstract

PURPOSE:To produce a sintered AlN article having high density and strength, by calcining a specific molded article in a non-oxidizing atmosphere in a vessel generating an (Al-O) gas atmosphere. CONSTITUTION:A molded article is produced by mixing AlN powder having an impurity oxygen content of <=5wt.% and an average particle diameter of 0.05-10mum with 0.01-15wt.% (in terms of element) of a compound of group IIa element (e.g. Ca or Sr), group IIIa element (e.g. Y, La) and/or rare earth element, granulating and grading the mixture and molding the obtained composition. The molded article is heated in a non-oxidizing atmosphere to remove the binder, put into a vessel made of Al2O3, sintered Al2O3 or powdery Al2O3 and capable of generating (Al-O) gas atmosphere in calcination and calcined at 1,550-2,050 deg.C for >=30min to obtain sintered AlN article having a relative density of >=85% and a bending strength of >=20kg/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for producing an aluminum nitride sintered body.

(Prior art) Aluminum nitride (AiN) has little strength loss even at high temperatures and has excellent chemical resistance, so it is used as a heat-resistant material. It is also seen as a promising material for heat sinks and insulators for circuit boards.

Such aluminum nitride does not have a melting point under normal pressure,
Since it decomposes at high temperatures above zsoo°C, it is used as a sintered body except for applications such as thin films.

Such an aluminum nitride sintered body is usually obtained by molding and sintering aluminum nitride powder.

However, when AiN powder with a grain size of 0.5- or more is used alone, the sinterability is not good, so it is difficult to obtain a dense sintered body without additives other than by hot pressing. .

For this reason, when sintering at normal pressure.

Usually, for the purpose of increasing the density of the sintered body, rare earth oxides, alkaline earth metal oxides, etc. are added as sintering aids, and carbon containers or BN-coated carbon containers or 7
Sintering in a 4N powder filler is commonly practiced. In order to achieve high thermal conductivity, it is necessary that the amount of oxygen in the raw material powder is small. However, coarse-grained powder
Since pulverization increases the amount of oxygen, if the material is fired as is without pulverization, it will not become densified in the container.

Firing conditions are required that provide densification even when using coarse raw material powder with a small amount of oxygen and a single grain size. In addition, the sintered body added rare earth oxide and fired in a carbon container has Affi on the surface.
A compound that is not N is produced. Moreover, the sintered body added with an alkaline earth metal oxide and fired in a carbon container is not in a good condition after being fired, such as deformation.

(Problem that the invention seeks to solve) However, when firing in a carbon container, a carbon container coated with BN, or a filling of AQN powder, high strength cannot be obtained because Hl is difficult to densify.

The present invention has been made in consideration of the above points.

The purpose of the present invention is to provide an aluminum nitride sintered body that is dense and has a good baked condition.

[Structure of the invention]

(Means and effects for solving the problem) In order to achieve the above object, the present inventors have investigated the sintering aid added to the aluminum nitride powder, the sintering conditions, and the density and bending resistance of the obtained sintered body. As a result of conducting experiments and studies regarding the relationship with strength, we discovered the following new matter and completed the present invention.

That is, using yttrium compound as a sintering aid
We have discovered that when added to iN powder and fired in a container that creates a (1-0) gas atmosphere, a sintered aluminum nitride body with good firing quality, high density, and high strength can be obtained. .

This effect is similar to other group IIa compounds (Sr, Y), IIa
The same phenomenon was observed in Group IIa compounds (a, Ba, Sr, etc.) and rare earth elements (La, Ce, Dy, Co, etc.).

The present invention is the result of various studies on optimal conditions for achieving high density based on this fact.

a) The amount of impurity oxygen is 5% by weight or less, and the average particle size is 0.
．． 05~io, and aluminum nitride powder.

0.01 to 15% by weight of group IIa elements such as Ca and Sr, group IIa elements such as Y and La, and rare earth elements;
IIa Group IIa compound I
) AII! ,0. An aluminum nitride characterized by creating a (A+1!-0) gas atmosphere in a container or during firing with an Al2O3 sintered body or 1.03 powder, and C) firing at a temperature of 1550 to 2050°C in a non-oxidizing gas atmosphere. This is a method for manufacturing a sintered body.

The aluminum nitride sintered body obtained by this method does not have a rough surface and does not deform.

It has a relative density of 85% or more and a bending strength of 20 kgcsg-'' or more.

The main points of the production method of the present invention are the purity and average particle size of the aluminum nitride raw material powder, sintering aid, sintering container, firing time, and firing atmosphere.

In consideration of sinterability, the aluminum nitride raw material powder, which is the main component, contains 5% by weight or less of oxygen. Average particle size is 0.0
Use one with a weight of 5 to 10.

Additives include Ca, IIa group compounds such as SF, Y,
Group IIa compounds such as La and rare earth element compounds (yttrium compounds are particularly preferred) are used.

The above-mentioned compounds are optimally oxides, nitrides, fluorides, oxyfluorides, oxynitrides, or substances that become these compounds upon firing. For example, substances that become oxides when fired are carbonates, nitrates,
Examples include oxalates and hydroxides.

The rare earth element compound and the like are added in an amount of 0.01 to 15% by weight in terms of the weight of the element such as the rare earth element.

Regarding the phosphoric acid container, a container that creates an (i-0) gas atmosphere during firing is used. As such a firing container,
It is possible to use a container in which the entire container is made of A or Ol, or a container in which the entire container is made of AQ or O□ and where the sample is placed is lined with an AgN plate, BN plate, W plate, etc.

Regarding the sintering time, if a sintering container in which the (1-0) gas atmosphere as described above cannot be obtained is used.

Even after firing for a short time of 30 minutes to 2 hours, the surface condition remains rough. Furthermore, an aluminum nitride sintered body that is deformable can be obtained when fired in a firing vessel that provides an (Al-0) gas atmosphere as described above.

Although it depends on the sintering temperature, it is possible to densify the aluminum nitride sintered body even if the temperature is raised to the target temperature and immediately cooled. More preferably, it is 30 minutes or more.

Regarding the firing temperature, 1550 to 2050°C is preferable.

When fired at a temperature lower than 1550°C, the particle size of the raw material powder.

Depending on the amount of oxygen, a dense sintered body cannot be obtained;
When fired at a temperature higher than 50° C., the vapor pressure of AXN itself increases, making densification difficult. The firing temperature is more preferably 1600 to 1950°C.

The sintering atmosphere is preferably one or more non-oxidizing atmospheres selected from the group of nitrogen gas, hydrogen gas, -carbon oxide, argon and the like.

It is carried out under atmospheric pressure including reduced pressure, increased pressure and normal pressure.

Next, an example of the method for manufacturing the aluminum nitride sintered body of the present invention will be described below.

First, a predetermined amount of a rare earth element compound as a sintering additive is added to the A and IN powders, and then mixed using a ball mill or the like. The pressureless sintering method is used for sintering.

In this case, a binder is added to the mixed powder, kneaded, granulated,
After grading, it is molded. As a molding method, a mold press, isostatic press, sheet molding, etc. can be applied. Subsequently, the molded body is heated in a non-oxidizing atmosphere, for example, in a nitrogen gas stream to remove the binder, and then sintered under normal pressure. The sintering temperature is set at 1550-2050°C.

(Example) An additive containing 1.3% by weight of oxygen as an impurity and having an average particle size of 2.1% was added as an additive.
4 was added in an amount of 72.5% by weight in terms of the weight of yttrium element, and mixed using a ball mill to prepare a raw material. Next, 4% by weight of an organic binder was added to this raw material and granulated, followed by press molding at a pressure of 500 kg/d (7) to obtain a green compact with a size of 44 x 34 x 5.2 mm. The compact was heated to 700° C. in a nitrogen gas atmosphere to remove the binder.

Further, the degreased body was housed in an alumina container (firing container A) made of an A and IN plate coated with BN powder and made with a hollow bottom.

Using this container in a nitrogen gas atmosphere (1 atm) at 1850℃
It was sintered under atmospheric pressure for 2 hours. The density of the obtained AYN sintered body was measured. From a sintered body, the total length is 36 or more, 1 width is 4
．． A square pillar with a thickness of 3.0 ± 0.1 mm and a thickness of 3.0 ± 0.1 mm is ground, and the roughness of the upper and lower surfaces is 0, as specified in JIS B 0601.
8S or less, and use this as a test piece, JIS R-16
01. Three-point bending strength was measured.

Furthermore, impurity oxygen in this sintered body was analyzed by fast neutron activation analysis (using Toshiba @NAT-ZOO-IC).The above sintering conditions and the characteristics of the obtained sintered body were
Shown in the table.

AuN sintered bodies were produced in the same manner as in Example 1 with various addition amounts of the second sintering additive, and each was evaluated in the same manner.

AdanN sintered bodies were produced in the same manner as in Example 1 above by varying the amount of additives added and the sintering temperature, and each was evaluated in the same manner.

Af
LN sintered bodies were manufactured and the same evaluations were performed on each of them.

Loss of directness A! 1. AfiN sintered bodies were produced in the same manner as in Example 1, except that the particle size of the N raw material powder, the amount of impurity oxygen, and the sintering temperature were changed, and the same evaluations were performed.

A was carried out in the same manner as in Example 1 by varying the amount of sintering additives, sintering temperature, sintering atmosphere, and atmospheric pressure.
! ;LN sintered bodies were manufactured and the same evaluation was performed on each of them.

ALN sintered bodies were produced in the same manner as in Example 1, except that the amount of the sintering additive added, the sintering temperature, and the sintering time were changed, and the same evaluation was performed.

Au
N sintered bodies were manufactured and the same evaluations were performed on each.

11 Contains 3% by weight of oxygen as an impurity, and has an average particle size of 1.
8- AsLN powder with an average particle size of 0.9- as an additive.
Y2O2 was added in an amount of 2% by weight in terms of the weight of yttrium element. The steps from molding to degreasing and the firing container were the same as in the above example. 180 during pressurization of nitriding gas at 10 atmospheres
Sintering was carried out at 0°C for 2 hours. The obtained sintered body was evaluated in the same manner as in Example 1 above.

S11 1 A, dN sintered body was produced in the same manner as in Example 17 above, except that the sintering time was changed, and the same evaluation was performed.

It contains 0.5% by weight of oxygen as an impurity and has an average particle size of 2.9. AiN powder with an average particle size of 0.9 as an additive.
- Y2O, 4% by weight in terms of the weight of yttrium element
Added. The steps from molding to degreasing and the firing container were the same as in Example 1 above. In a nitriding gas reduced pressure atmosphere (0,
1 atm)) Sintered at 1900° C. for 2 hours and evaluated in the same way.

A! A! ;LN sintered bodies were manufactured and the same evaluation was performed on each of them.

Additives to ALN powder containing 0.48% by weight of oxygen as an impurity and having an average particle size of 2.9% are added as additives.
9-YII02 was added in an amount of 4% by weight in terms of the weight of yttrium element. By changing the firing container.

ON sintered bodies were manufactured in the same manner as in Example 1 above, and the same evaluations were performed on each.

AiN powder containing 0.26% by weight of oxygen as an impurity and having an average particle size of 5.8p was added as an additive with an average particle size of 0.26% by weight.
9. Y, 0. is 2.5 in terms of weight of yttrium element.
% by weight was added. iN sintered bodies were produced in the same manner as in Example 1, using various firing containers, and the same evaluations were conducted for each.

An additive having an average particle size of 0.5% is added to the AiN powder containing 0.59% by weight of oxygen as an impurity and having an average particle size of 2.0.
9p of Y2O, converted to the weight of yttrium element, is 2.5
% by weight was added. AQN sintered bodies were produced in the same manner as in Example 1, using various firing containers, and the same evaluations were conducted for each.

In Comparative Example 1, a degreased body obtained by the same method as in Example 1 was placed in a container whose entire inside was made of carbon (sintered container A).
, Comparative Example 2 uses a container whose inside is entirely made of iNg, and Comparative Example 3 uses a container whose inside is entirely made of tungsten.
C. for 2 hours under atmospheric pressure in a N air stream to obtain a sintered body.

The properties of these sintered bodies are shown in Table 2, and the surfaces of the obtained sintered bodies were rough and deformed. From this result,
At least when a sintered container whose interior is partially made of alumina is not used, it has high strength. i with good surface condition
No N sintered body was obtained, demonstrating the effectiveness of an alumina atmosphere.

(Left below) [Effects of the Invention] As described above, the method for producing an aluminum nitride sintered body of the present invention produces an excellent aluminum nitride sintered body that is Jl dense, has a good firing state, and has high strength. and its industrial value is extremely large.

Agent: Patent Attorney Noriyuki Chika Same as Mitsuyuki Matsuyama

Claims (2)

[Claims] (1) a) Aluminum nitride powder with an impurity oxygen content of 5% by weight or less and an average particle size of 0.05 to 10 μm, and group IIa, group IIIa, and group IIa compounds such as Ca and Sr, Y, and La. b) A container made of Al_2O_3, which is formed by mixing a group IIIa compound such as a group IIIa compound and a rare earth element containing 0.01 to 15% by weight of a rare earth element, a group IIIa compound, and/or a rare earth element compound. Medium or Al_2O_
3 sintered body or Al_2O_3 powder during firing (Al-
O) A method for producing an aluminum nitride sintered body, characterized by firing in a container that creates a gas atmosphere, c) in a non-oxidizing gas atmosphere, at a temperature of 1550 to 2050°C. (2) Relative density 85% or more, bending strength 20kgcm^-
The method for producing an aluminum nitride sintered body according to claim 1, wherein the aluminum nitride sintered body is ^2 or more.