JPH0127023B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a method for solid-phase bonding Si ₃ N ₄ ceramics and Al ₂ O ₃ ceramics with high bonding strength.

(b) Problems with conventional technology Conventional technology Ceramics whose main component is Si ₃ N ₄ and
When joining ceramics containing Al ₂ O ₃ as the main component, after bringing the interfaces of the objects into contact, the solid state is maintained at a temperature of around 1700°C under pressure in a non-oxidizing atmosphere. A method of diffusion bonding has been used. However, since Al ₂ O ₃ forms a solid solution in Si ₃ N ₄ ceramics at around 1500°C, when Si ₃ N ₄ ceramics and Al ₂ O ₃ ceramics are brought into direct contact and solid phase bonded, Al ₂ O ₃ Unilateral diffusion of Al and O from the Si ₃ N ₄ ceramics occurred. For this reason, coarse pores were formed near the bonding interface inside the Al ₂ O ₃ based ceramics due to the Kirkendall effect, reducing the strength of the bonded body.

FIG. 1 shows a photograph of the structure near the bonding interface inside the Al ₂ O ₃ ceramics of a bonded body of Si ₃ N ₄ ceramics and Al ₂ O ₃ ceramics produced by the conventional bonding method described above. As is clear from the photo, coarse pores are generated near the bonding interface inside the Al ₂ O ₃ ceramics. These pores are generated by the Kirkendall effect when Al and O diffuse into the Si ₃ N ₄ ceramics during solid phase diffusion bonding and form a solid solution. At this time, almost no diffusion occurs from the Si ₃ N ₄ ceramic to the Al ₂ O ₃ ceramic.

As mentioned above, Si ₃ N ₄ ceramics and
When joining Al ₂ O ₃ ceramics, conventional
The method of solid-phase diffusion bonding by bringing Si ₃ N ₄ ceramics and Al ₂ O ₃ ceramics into direct contact has the problem that coarse pores are generated in the Al ₂ O ₃ ceramics due to the Kirkendall effect. Therefore, it was impossible to obtain a Si ₃ N ₄ -Al ₂ O ₃ bonded body with high bonding strength. In view of this point, the present inventors suppressed the Kirkendall effect to suppress the generation of pores,
With the aim of obtaining a Si ₃ N ₄ -Al ₂ O ₃ bonded body with high bonding strength, the present invention was achieved as a result of efforts to pursue phenomena and improve bonding methods.

(c) Disclosure of the invention The Si ₃ N ₄ ceramics referred to in the present invention are those containing 50% by weight or more of Si ₃ N ₄ in a sintered body, with the remainder being
Refers to ceramics containing glass and crystalline phases of oxides added as auxiliaries during sintering, such as Al ₂ O ₃ and/or MgO and/or rare earth oxides, and sialon. In addition, the Al ₂ O ₃ ceramics of the present invention include 50% by weight or more of Al ₂ O ₃ in the sintered body,
Refers to ceramics in which the remainder consists of oxides such as SiO ₂ and/or ZrO ₂ .

When the above Si ₃ N ₄ ceramics and Al ₂ O ₃ ceramics are brought into direct contact and solid-phase diffusion bonded,
One-sided diffusion of Al and O from Al ₂ O ₃ ceramics into Si ₃ N ₄ ceramics causes large pores near the bonding interface inside the Al ₂ O ₃ ceramics, which is a problem with the conventional technology. As stated in the section. The present inventors investigated this phenomenon using EPMA (Electron
As a result of further detailed analysis using analysis methods such as Probe Micro Analysis and X-ray diffraction, it was found that Si ₃ N ₄
It was found that a sialon layer was formed in the area adjacent to the bonding interface inside the system ceramics. This Sialon is made from Al ₂ O ₃ ceramics.
Al and O diffused into Si ₃ N ₄ ceramics
It is thought that the product was formed by the reaction between Si 3 N 4 and Si ₃ N ₄ .

Based on this result, we interposed a Sialon sintered body between Si ₃ N ₄ ceramics and Al ₂ O ₃ ceramics, and heated them for 1800 min under pressure in a non-oxidizing atmosphere.
When solid-phase diffusion bonding was performed while holding at ℃,
A good Si ₃ N ₄ -Al _{2 O} 3 bonded body was obtained without generating large pores inside the _{Al 2} O ₃ based ceramics. From this, Si ₃ N ₄ ceramics and
By sandwiching the Sialon sintered body between Al ₂ O ₃ ceramics, it can be made from Al ₂ O ₃ ceramics.
It has been found that one-sided diffusion of Al and O into Si ₃ N ₄ ceramics can be suppressed. Although the reason for this is currently being investigated in detail, it is thought that it is highly likely that the diffusion rate of Al and O is lower in the Sialon sintered body than in Si ₃ N ₄ ceramics.

Sialon as referred to in the present invention is a Si ₃ N ₄ structure in which Al is substituted in the Si position and O is substituted in the N position, and has a crystal structure similar to the Si ₃ N ₄ ceramics that are the materials to be joined. At the same time, it causes diffusion of Al and O with Al ₂ O ₃ ceramics.
Suitable as an intervening layer when bonding Si ₃ N ₄ ceramics and Al ₂ O ₃ ceramics. as mentioned above
The Si ₃ N ₄ structure in which Al is substituted in the Si position and O is substituted in the N position is collectively called sialon.
There are several types of Sialon, each with a different composition and structure. Particularly preferred as the intervening layer of the present invention is a type of sialon called β-sialon. β-Sialon is a general formula
denoted by Si _6- zAlzOzN _8- z (where z = 0 to 4.2),
The number of Al and O to be replaced is the same, and Si+Al/O+N
are always in a molar ratio of 3/4. Si ₃ N ₄ particles contained in a sintered body of Si ₃ N ₄ ceramics generally have a β-type crystal structure, and considering the similarity of the crystal structures, β-sialon is likely to be the intervening layer. most suitable. It is generally known that the diffusion coefficient of O in β-sialon is small, and in the present invention, by interposing sialon between the objects to be bonded, Al ₂ O ₃ ceramics can be
This shows good agreement with the fact that the unilateral diffusion of O was suppressed.

However, the intervening layer is not limited to β-SiAlON, but Mx (Si, Al) ₁₂ (O, N) ₁₆ (M
Even if α-Sialon is a metal with a composition such as Li, Mg, Ca, Y, etc. x≦2), it is difficult to prevent Al and O from unilaterally diffusing from Al ₂ O ₃ ceramics to Si ₃ N ₄ ceramics. It is possible to obtain a good bonded body without forming voids.

The present invention will be explained below with reference to Examples.

Example 1 A Si ₃ N ₄ sintered body with a density of 99.2%, which was sintered by adding 5% by weight of MgO as a sintering aid, and a sintered body with a density of 99.7%, which was obtained by sintering α-Al ₂ O ₃ with a purity of 99.5%. Each Al ₂ O ₃ sintered body was processed into a cylindrical shape with a diameter of ₅ mm and a height of ₃ mm.
A disc made of Sialon sintered body processed into a diameter of 5 mm and a thickness of 1 mm was sandwiched between the two and heated at 1800°C under a pressure of 30000 kg/mm ^2.
It was held for 30 minutes and solid-phase diffusion bonding was performed.

FIG. 2 shows the structure of the Al ₂ O ₃ phase near the bonding interface of this bonded body.

Figure 1 shows the structure without using Sialon as an intervening layer.
When Si ₃ N ₄ sintered body and Al ₂ O ₃ sintered body are directly joined
This is the structure near the bonding interface of the Al ₂ O ₃ phase.

Comparing FIG. 1 and FIG. 2, it is clearly seen that by using SiAlON as the intervening layer, it is possible to suppress the generation of large pores in the Al ₂ O ₃ sintered body during bonding. The tensile strength of this joint is 16
It was Kg/ ^mm2 .

Example 2 A Si ₃ N ₄ sintered body with a density of 98.7% was sintered by adding 10% by weight of Al ₂ O ₃ as a sintering aid, and a sintered body with a density of 99.3% by adding 8% by weight of SiO ₂ Each _of the Al ₂ O ₃ sintered bodies was processed into a cylindrical shape with a diameter of 10 _mm and a height _{of 10 mm} .
7
% α-sialon sintered body with a diameter of 10 mm and a thickness of 1 mm.
Under a pressure of 200Kg/cm ² ,
It was held at 1700°C for 30 minutes and solid-phase diffusion bonding was performed.

At this time, no coarse pores were generated in the Al ₂ O ₃ sintered body, and a good joined body was obtained. The joint strength of this joined body was 14 Kg/mm ² in terms of tensile strength.

[Brief explanation of drawings]

Figure 1 shows the magnification of the structure near the _{bonding interface of Al 2 O 3 when Si 3 N 4 and Al 2 O 3 are directly bonded using} conventional methods.
FIG. 2 is a micrograph (magnification: 360 times) of the structure near the Al ₂ O ₃ bonding interface of the bonded body made by the bonding method of the present invention.

Claims (1)

[Claims] 1 Ceramics containing Si ₃ N ₄ as a main component and Al ₂ O ₃
1. A method for joining ceramics, which is characterized in that when joining ceramics containing as a main component, solid phase joining is performed with Sialon interposed between the two. 2 The intervening sialon is Si _6- zAlzOzN _8- z (z
2. The method for joining ceramics according to claim 1, wherein the ceramic is β-sialon having a composition of 0.1 to 4.2). 3 The intervening sialon is Mx (Si, Al) ₁₂ (O,
N) ₁₆ (M is a metal such as Li, Mg, Ca, Y, etc. x≦
2) The method for joining ceramics according to claim 1, wherein the ceramic is α-sialon having the composition.