JPS62153167A - Sic sintered body with high electric resistivity - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a SiC sintered body used for electrically insulating substrates, electrical resistors, etc., and more specifically to a SiC sintered body with high density and high electrical resistivity. Regarding.

Prior Art SiC is generally conductive, and its normal sintered body is also conductive, making it unsuitable for electrically insulating substrates. Furthermore, it is difficult to make a heating element with a large electrical resistivity.

In particular, since SiC is difficult to sinter, a sintered body with a low density has low strength and is not practical, so it is necessary to increase the density, but this will further increase the electrical resistance.

An improved version of this is one in which a small amount of Be or BeO is added to SiC and sintered (JP-A-57-If3G3
6i5, 513-69473, 57-15637
3, 57-166365, 59-6134
No. 73).

Problem to be solved by invention □Be or BeO
It is true that the electrical resistance of SiC sintered bodies added with B increases, but
It is difficult to handle because e has tfl.

Also, simply adding Be or BeO to SiC does not increase the density, so hot pressing is necessary, so rli
It has drawbacks such as it can only be made in a pure form and is expensive.

SiC is difficult to sinter, so it is not easy to obtain a high-density sintered body under normal pressure.
It is known that by adding such substances, high density can be obtained even under normal pressure. SiC has different crystal forms called α and β, but both can be made to have higher densities by adding two types of additives.

Generally, these sintered bodies are made by crushing SiC into fine powder.
The above-mentioned additives are added to this, and after molding, it is heated to a high temperature with or without pressure. When the electrical specific resistance of this sintered body is measured, it is usually 103ΩC1n or less, which is quite low.

It is known that adding Be or BeO to SiC increases the electrical resistance, but because of the drawbacks mentioned above,
The present inventor conducted various studies to increase the electrical resistance without adding Be or BeO, and arrived at the present invention.

That is, one object of the present invention is to obtain a SiC sintered body with high density and high electrical resistance without adding Be or BeO.

Means for Solving the Problems According to research conducted by the present inventors, it has been found that the electrical resistance of a SiC sintered body is greatly influenced by the N component contained therein. Therefore, the present invention aims to increase the electrical resistance by suppressing the N component in the sintered body to 200 ppm or less, and to increase the density of SiC by containing specific amounts of C and B.

That is, the present invention uses G O, 5 to 3.0% by weight, B O, 1
~1.5% by weight, N 200ppm or less, the remainder substantially consists of Sic, and the bulk density is 3-Og/c
It is a SiC sintered body with a high electrical resistivity of 90 m or more. SiC may be α, β, or a mixture thereof. In the above, C may be free or bonded carbon such as 84C other than C as SiC. B is also free or bonded. N is thought to exist in the form of solid solution, etc. However, the electrical resistance does not increase unless it is below 200 ppm.The reason why the electrical resistance decreases when there is a large amount of N is because N dissolves in SiC and acts as a donor (moves), increasing free carriers (?l! children). It is thought that the

The reason why C is set in the above range is to increase the density of the SiC sintered body and because if C exceeds 3.0% by weight, the electrical resistance decreases. Also, for B, the range of o, t-t, s weight % is preferable in order to increase the density of SIG, and from the viewpoint of increasing the electrical resistance, it must be 0.1 weight % or more, and 0.
．． Particularly preferred is IO to 0.14% by weight. When a SiC sintered body is used as an electrically insulating substrate, it is required to have high thermal conductivity, which requires increasing the density, and for other uses, the higher the density is, the better. Therefore, in the present invention, the density is set to 3.0.
g/cm' or more.

Next, a method for manufacturing the sintered body of the present invention will be described.

SiC produced by a silica carbon reduction method, the so-called Acheson method, is industrially advantageous. This SiC is pulverized. In ordinary SiC sintered bodies, the N content j, 1 is not a problem, so they are pulverized in air using a ball mill or the like. However, it was found that a considerable amount of N was adsorbed on SiC when pulverized in air. This N hardly escapes during sintering.

Therefore, in order to make a SiC sintered body with low N content, N of powdered SiC is
content must be lowered. Most of the N in conventional SiC powder enters the grinding process, so in the present invention, S
The iC is ground under a non-nitrogen atmosphere, for example under an argon atmosphere. Grinding should be as fine as possible, preferably less than 5 squares. It is below the ppm that enters during pulverization. Either α or β crystal form can be used.

The C added to the SiC powder can be used by dispersing carbon powder such as carbon black with a dispersion medium, but it is preferable to add a liquid phenol resin or the like and carbonize it to C during sintering of the SiC. In this case, consider the carbonization rate of the resin, and also consider that C is S+02'J of 61 n in SiC.
In the case where the resin gasifies and escapes due to the reduction of the resin, it is necessary to take into consideration the amount thereof and determine the amount of the resin added so that the above-mentioned Q'E of C remains in the sintered body.

B is a powder of suspended boron, B4C, etc.

? Even if it is added in the form of i-boron, it is 84% in the SiC sintered body.
It is thought that many of them are in the shape of a G.

A C1B source is added to the SiC powder containing as little N as possible as described above, a primary binder such as PVA is added, and the powder is molded into a desired shape. The molded body is heated and sintered. Sintering may be performed with or without pressure, but if the molded object has a complicated shape, non-pressure is suitable. Sintering temperature is suitably in the range of 1800 to 2200°C. Sintering is performed under an inert atmosphere such as Ar, but a N atmosphere is avoided.

EXAMPLE α-3iC grains with a purity of 96% produced by the Acheson method were ground to obtain a powder of 2.5 gm or less. The pulverization was carried out as follows to prevent N from entering. Several meters inside the ball mill
Put SiC powder of size m, degas it with a vacuum pump,
The temperature was set to 0.04 Torr and Ar was injected. This was repeated twice, and then crushed for one day. Take this thing out and F with hydrochloric acid.
e was removed and classified by the sedimentation method.

The resulting SiC powder had an N content of 190 ppm. 84G O,1 to 100 parts by weight of this SiC powder
53 overlapped parts and 1.0 parts by weight of carbon black were mixed well, and then 300 cc of water and 2 parts by weight of PVA were added.
After mixing for 0 hours, the mixture was granulated using a spray dryer. The granules were pressure-molded to a diameter of 50mff1 and a thickness of 8mm,
It was sintered by heating at 2100° C. for 60 minutes in an Ar atmosphere without pressure. Its characteristics are shown in No. 1 in Table 1.

The sintering process was repeated in the same manner, but the amounts of B and C were changed, and the results are shown in Table 1, No. 2 and below. No. of comparative example in the table,
5 or less means that SiC pulverization was performed in air.

(The following is a blank space) As shown in the results described in Effects of the Invention, the sintered body of the present invention has a high density;
Since it has a high 1E specific resistance, it can be used for electrical insulation, plates, heating elements, etc.

Claims (1)

[Claims] C0.5-3.0% by weight, B0.1-1.5% by weight,
N200ppm or less, the remainder substantially consisting of SiC,
Bulk density is 3.0g/cm^3 or more, electrical resistivity is 10^
A SiC sintered body with a high electrical specific resistance of 4 Ωcm or more.