JPH0840775A - Silicon nitride sintered product and method for producing the same - Google Patents

Abstract

PURPOSE:To obtain a silicon nitride sintered product high in mechanical strength and not containing pores and residual silicon which are the defects of a silicon nitride sintered product using silicon as a raw material. CONSTITUTION:The silicon nitride sintered product contains >=0.02wt.% of Fe. Fe compound particles having particle diameters of >=0.5mum and contained in the silicon nitride sintered product occupies an area of >=0.1% in a two-dimensional range of 200X200mum, and also occupies an area of <=15% in a cell obtained by dividing the two-dimensional area of 200X200mum into longitudinal and lateral 20 equal divisions (10mumX10mum unit, 400 cells).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride sintered body (ceramics) utilizing reaction sintering, particularly to a silicon nitride sintered body having high mechanical strength and a method for producing the same.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Laid-Open No. 56-14635, as a method for producing a high-density silicon nitride sintered body, Fe, Co, Ni, Mh, W, Mo, Ti, Al is added to silicon powder. , M
g, at least one powder of a metal or oxide selected from Zr is added, and the temperature is 1300 to 1550.
There is a method in which a calcined body sintered in a nitrogen gas atmosphere at 0 ° C. is immersed in a solution containing the above metal and then sintered again at a temperature of 1350 to 1550 ° C. while supplying silicon-containing vapor.

When the molded body is sintered by the above-mentioned manufacturing method, the added metal or the oxide of the added metal becomes a liquid phase and / or a gas phase during the sintering, and pores and swelling are generated inside the obtained sintered body. Since it causes cracks, it is not suitable for high temperature sintering of thick products.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, the object of the present invention is to eliminate the pores and residual silicon, which are the drawbacks of silicon nitride sintered bodies made from silicon as a raw material. An object is to provide an excellent silicon nitride sintered body and a method for manufacturing the same.

[0005]

In order to achieve the above object, the constitution of the present invention is a silicon nitride sintered body containing 0.02 wt% or more of Fe, which is included in the silicon nitride sintered body. Fe compound particles having a particle size of 0.5 μm or more are 200 × 20
The area occupied by a two-dimensional range of 0 μm is 0.1% or more, and the area occupied by a cell (400 units of 10 μm × 10 μm unit) divided into 20 horizontal and 200 μm ranges is 15% or less. It is characterized by

[0006]

Function: Silicon is added to silicon nitride (Si ₃
N ₄ ) and by adding raw materials effective in forming α-phase silicon nitride during conversion, for the following reasons:
It is possible to obtain a high-strength silicon nitride sintered body in which there are no problems such as pores and residual silicon which are defects of the silicon nitride sintered body using silicon as a raw material, that is, there is no residual silicon and Fe content is uniformly dispersed.

(A) The inner diameter of the pores in the compact becomes smaller, and the inner diameter of the pores in the silicon nitride sintered body also becomes smaller.

(B) Nitriding of silicon is smooth, and residual silicon is small.

(C) The particle size of the Fe compound particles is reduced, and the Fe compound particles are uniformly dispersed in the silicon nitride sintered body.

(D) ZnO added to the raw material of the molded body
However, it increases the amount of α-phase silicon nitride produced when silicon is converted to silicon nitride, and increases the strength of the silicon nitride sintered body.

[0011]

EXAMPLE A silicon nitride sintered body according to the present invention has a content of 0.02 wt.
It is characterized in that a silicon raw material containing at least Fe is used. The silicon nitride sintered body is made of Si, Al, Y, O, N, Z.
Each element of n and Fe is contained, and each element is Si, Si ₃ N ₄ ,
When the weights existing as oxides of Al ₂ O ₃ , Y ₂ O ₃ and Zn are a, b, c, d and e, respectively, and the weights existing as Fe are f, the following equations 6 ≦ (c + d + e ) 100 / (1.67a + b + c + d + e +
f) ≦ 12.0 1 ≦ (c + d) / e 0.02 ≦ 100f / (1.67a + b + c + d + e + f) ≦ 7.5 0.001 ≦ 100e / (1.67a + b + c + d + e + f) ≦ 7.
The composition satisfies 5. The above equations are approximately obtained from the materials shown in FIG. 3 (excluding the material B0).

In the above composition of the silicon nitride sintered body,
Instead of Zn, Ca, Ni, Cu, Cr, Co, Mg,
One or more elements selected from Mn, Sn, Ho, Cd and Pb may be added.

Most of the Fe compound particles contained in the silicon nitride sintered body have a particle size of 0.5 μm or less. Specifically, the F contained in the silicon nitride sintered body has a particle size of 0.5 μm or more.
The area of the e compound particles in a two-dimensional area of 200 × 200 μm is 0.1% or more, and the area of 200 × 200 μm
The cell (10μm x 10)
The area occupied by 400 μm units is 15% or less.

The silicon nitride sintered body according to the present invention has a very dense structure. The porosity of the silicon nitride sintered body is 0.5.
%, And the average inner diameter of the pores is 2 μm or less. The silicon nitride contained in the silicon nitride sintered body exists as columnar particles, and as shown in FIG. 4, 80% or more of the total number of columnar particles has a diameter of 0.2 to 1.2 μm and a length of 7 according to the analysis result. .5
μm or less. In other words, as shown in FIG. 5, the columnar particles have a length / diameter value of 1 to 20, and 50% or more of the total number of columnar particles have a length / diameter value of 4.5 to 20. Specifically, about 50% of the total number of columnar particles has a length / diameter value of 4.5 to 10.

In order to manufacture the silicon nitride sintered body according to the present invention, a compact is compacted from a powder containing each element of Si, Al, Y, O, N, Zn and Fe and having a predetermined composition ratio. The molded body is heated in a gas atmosphere containing nitrogen at a temperature of 1700 ° C. or lower to convert Si into Si ₃ N ₄ , and then a temperature of 1700 to 1700.
Obtained by firing at 2000 ° C.

Each element Si, Al, Y, O, N, Zn, F
The composition ratio of e is such that each element is Si, Si ₃ N ₄ , Al
_When the weights existing as oxides of ₂ O ₃ , Y ₂ O ₃ and Zn are respectively a, b, c, d and e and the weights existing as Fe are f, the following respective equations 6 ≦ (c + d + e) 100 / (1.67a + b + c + d + e +
f) ≦ 12.0 20 ≦ a / (a + b) ≦ 90 1 ≦ (c + d) / e 0.5 ≦ 100e / (a + b + c + d + e) ≦ 7.5 1 ≦ (c + d) / e 0.02 ≦ 100f / (1.67a + b + c + d + e + f) ≦ 7.5 Is determined in advance.

Instead of Zn, Ca, Ni, Cu, Cr,
One or more elements selected from Co, Mg, Mn, Sn, Ho, Cd, and Pb can be used. As the Si powder used for producing the molded body, one having an Fe content of 0.07 wt% or more as an impurity and an average particle size of 1 μm (by a laser diffraction method) or less is used. Further, as the powder of each composition used for producing the molded body, one having an average particle size of 1 μm or less is used.

Next, a concrete example will be described.

Example 1 59.2 parts (about 60 wt.%) Of silicon powder containing 0.28 wt.% Fe and having an average particle size of 0.3 .mu.m.
%) And α-phase silicon nitride powder having an average particle size of 0.3 μm.
9 parts and 6.49 parts of Y ₂ O ₃ powder having an average particle size of 1 μm,
3.89 parts of Al ₂ O ₃ powder having an average particle size of 0.7 μm and 1.29 parts of ZnO powder having an average particle size of 1 μm were put in a resin pot together with methanol, a dispersant, and resin balls. Ball milling was performed for 28 hours to obtain an average particle size of 0.
A 5 μm slurry was prepared.

Next, the slurry is dried and pulverized, and then formed into a plate-like body having a length of 10 mm, a width of 80 mm and a thickness of 5 mm by an axial press, and the plate-like body is subjected to CI at a pressure of 2000 kgf / cm ² .
P treatment was performed to produce a molded body. Then, the compact is fired in a nitrogen gas atmosphere at a pressure of 9.5 kgf / cm ² at a temperature of 1400 ° C. for 10 hours and then at a temperature of 1900 ° C.
And sintered for 5 hours to obtain a silicon nitride sintered body A1 (shown as an example of a typical composition ratio in FIG. 3).

Further, as a comparative example, using a raw material having different amounts of impurities contained in the silicon raw material, the same compact as in Example 1 was sintered in the same manner to obtain a large number of sintered compacts B1 (see FIG. 3). Is shown as a representative example).

As shown in FIG. 3, with respect to the silicon nitride sintered body A1 of the present invention and the sintered body B1 of the comparative example, the bending strength (JISR1601) by four-point bending was measured. It was found that the bending strength of the united body A1 was extremely superior to that of the sintered body B1 of the comparative example. As shown in FIG. 1, when the amount of Fe contained in the raw material of the silicon nitride sintered body is about 0.08 wt% or less, the bending strength of the silicon nitride sintered body is halved, and it is contained in the raw material of the silicon nitride sintered body. When the amount of Fe contained is more than about 0.08 wt%, preferably more than 0.1 wt%, the bending strength of the silicon nitride sintered body becomes excellent at about 1000 MPa.

Next, using raw materials having different average particle sizes of silicon powder containing 0.28 (± 0.02) wt% of Fe, the same as in Example 1 (same composition ratio as the silicon nitride sintered body A1). A large number of silicon nitride sintered bodies C0 were manufactured from the molded body of 1. As shown in FIG. 2, the bending strength of each of the obtained silicon nitride sintered bodies C0 was measured to find that Fe0.28 (±
0.02) The average particle size of the silicon powder containing wt% is about 1μ.
High bending strength at m or less, but Fe0.28 (±
0.02) The average particle size of the silicon powder containing wt% is about 1μ.
It has been found that when it exceeds m, it is the same as the conventionally known one.

Further, the mixing ratio of silicon and silicon nitride, Y ₂ O
Using raw materials with different addition amounts of ₃ , Al ₂ O ₃ , and ZnO,
Silicon nitride sintered bodies D1 to D6 and E1 to E3 were produced from the molded body having the same composition as in Example 1 by the same method. As shown in FIG. 3, the bending strength of each of the silicon nitride sintered bodies D1 to D6 and E1 to E3 is Zn.
It was found that the amount of O added had a great influence, and that the amount of ZnO added was 0.01 wt% or less or 0.06 wt% or more was not satisfactory.

[0025]

As described above, the present invention provides a silicon nitride sintered body containing 0.02 wt% or more of Fe, the Fe compound having a grain size of 0.5 μm or more contained in the silicon nitride sintered body. The particles occupy an area of 0.1% or more in a two-dimensional range of 200 × 200 μm, and a cell (10 μm × 10 μm unit;
The area occupied by 400) is 15% or less, and Fe is generally considered to be an impurity.
It is possible to obtain a high-strength silicon nitride sintered body by using inexpensive silicon powder containing a large amount of as a main raw material.

Since the silicon nitride sintered body according to the present invention utilizes reaction sintering, the shrinkage amount of the silicon nitride sintered body due to firing is
Compared to 1/3 to 1/4 of the sintered body using silicon nitride as the main raw material, there is little deformation in the finish of the silicon nitride sintered body, and the near netting property (the mechanical properties are sensitively changed due to the minute difference in the composition ratio). No) and the manufacturing cost can be reduced.

According to the manufacturing method of the present invention, a silicon nitride sintered body excellent in dimensional stability and mechanical strength can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the amount of Fe contained in the raw material of a silicon nitride sintered body according to the present invention and the bending strength of the silicon nitride sintered body.

FIG. 2 is a diagram showing a relationship between a grain size of Si powder as a raw material of the silicon nitride sintered body and a bending strength of the silicon nitride sintered body.

FIG. 3 is a table showing the composition ratio of the raw material powder of the silicon nitride sintered body and the bending strength of the silicon nitride sintered body.

FIG. 4 is a diagram showing a physical composition of silicon nitride contained in the same silicon nitride sintered body.

FIG. 5 is a diagram showing a physical composition of silicon nitride contained in the same silicon nitride sintered body.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C04B 35/58 102 V 35/65

Claims (9)

[Claims] 1. A silicon nitride sintered body containing 0.02 wt% or more of Fe, wherein the Fe compound particles having a particle size of 0.5 μm or more contained in the silicon nitride sintered body are 200 × 200 μm.
The area occupied by the two-dimensional range of m is 0.1% or more,
A silicon nitride sintered body characterized by having an area of 15% or less in a cell (400 units of 10 μm × 10 μm) in which a range of 200 × 200 μm is divided into 20 equal parts vertically and horizontally. 2. The silicon nitride sintered body according to claim 1, wherein the silicon nitride sintered body has a porosity of 0.5% or less and an average inner diameter of the pores of 2 μm or less. 3. The columnar particles of silicon nitride contained in the silicon nitride sintered body have a diameter of 0.2 to 80% of all columnar particles.
1.2 μm, 7.5 μm or less in length, the length / diameter value of each columnar particle is 1 to 20, and the total number of columnar particles is 50.
% Or more has a length / diameter value of 4.5 to 20. The silicon nitride sintered body according to claim 1. 4. The silicon nitride sintered body is made of Si, Al, Y,
Each element of O, N, Zn, Fe is included, and each element is Si, S
The weights existing as oxides of i ₃ N ₄ , Al ₂ O ₃ , Y ₂ O ₃ , and Zn are a, b, c, d, and e, respectively, and Fe
Assuming that the existing weight is f, the following equations 6 ≦ (c + d + e) 100 / (1.67a + b + c + d + e +)
f) ≦ 12.0 1 ≦ (c + d) / e 0.02 ≦ 100f / (1.67a + b + c + d + e + f) ≦ 7.5 0.001 ≦ 100e / (1.67a + b + c + d + e + f) ≦ 7.
The silicon nitride sintered body according to claim 1, which has a composition satisfying 5. 5. Ca, Ni, C instead of the Zn element
u, Cr, Co, Mg, Mn, Sn, Ho, Cd, Pb
The silicon nitride sintered body according to claim 4, which contains at least one element selected from the group consisting of: 6. An element containing Si, Al, Y, O, N, Zn and Fe, each element being Si, Si ₃ N ₄ , Al ₂ O ₃ ,
Weights existing as oxides of Y ₂ O ₃ and Zn are a, b, c, d, and e, respectively, and weights existing as Fe are f.
Then, the following equations 6.0 ≤ (c + d + e) 100 / (1.67a + b + c + d + e)
+ F) ≦ 12.0 20 ≦ a / (a + b) ≦ 90 1 ≦ (c + d) / e 0.5 ≦ 100e / (a + b + c + d + e) ≦ 7.5 0.02 ≦ 100f / (1.67a + b + c + d + e + f) ≦ 7.5 Then, the molded body is heated at a temperature of 1700 ° C. or lower in a gas atmosphere containing nitrogen to convert Si into Si ₃ N ₄ , and then at a temperature of 1700 to 2
A method for producing a silicon nitride sintered body, which comprises firing at 000 ° C. 7. Instead of Zn, Ca, Ni, Cu, C
The method for producing a silicon nitride sintered body according to claim 6, which contains at least one element selected from r, Co, Mg, Mn, Sn, Ho, Cd, and Pb. 8. The Si powder used for producing the molded body has an average particle size of 1 μm or less, and contains 0.0% as an impurity.
7. The method for producing a silicon nitride sintered body according to claim 6, which contains 7 wt% or more of Fe. 9. The method for producing a silicon nitride sintered body according to claim 6, wherein the average particle size of the powder of each element used for producing the molded body is 1 μm or less.