JPS6036376A - Silicon carbide-based resistance material and its manufacturing method - 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 Application of the Invention] The present invention relates to a novel silicon carbide-based resistance material that can be used in a wide range of resistance vehicles, and a method for manufacturing the same.

[Background of the invention]

Silicon carbide (hereinafter abbreviated as SiC) has a high heat resistance, and its application to high-temperature structural materials due to its high-temperature strength and oxidation resistance is being considered.

On the other hand, since SiC electrically belongs to a semiconductor, it has been conventionally used in heating elements, varistors, resistors, etc. by utilizing its resistance characteristics. Recently, consideration has been given to using high-density SiC sintered bodies, which have been developed for high-temperature structural materials and have many unique characteristics, as resistor materials for electronic components or high-power power transmission and transformation equipment. In order to use the above-mentioned SIC sintered body for many purposes, SiC resistance materials having various resistivities are required. However, even if the same composition is subjected to force, only the resistivity will be reduced to 1 without reducing properties such as heat resistance and mechanical strength.
There is no known material or technology that can freely change the resistance over a wide range of 02 to 1010 ohms.

Conventionally, in order to vary the resistivity of a SiC sintered body over a wide range, a method has been known in which a specific component serving as a sintering aid is added to SiC, which is the main component. For example, Tokuko Sho 58-31755
As seen in (SiC with approximately 2% beryllium oxide (BED) or boron nitride (BN) added, the resistivity at room temperature is more than 10I0Ωm, but the change in resistivity with respect to the amount of addition is very steep. It is virtually impossible to obtain the desired resistivity using an auxiliary additive needle.On the other hand,
When boron (B) or aluminum (At) is added alone or as a compound, a resistivity of a value specified depending on the component can be obtained, but in this case, it is difficult to vary the resistivity over a wide range. Another method is to combine SiC powder and insulating powder and adjust the amount of insulating powder to obtain high resistivity75, but this is not preferred because it impairs the excellent properties of SiC.

[Purpose of the invention]

The present invention was made to solve the above-mentioned conventional problems, and it is possible to vary the resistivity over a wide range.
The present invention provides an iC-based resistance material and a method for manufacturing the same.

[Summary of the invention]

The characteristics of the present invention are that SIC and aluminum oxide (A/ao
By hot-press sintering the composition consisting of the two components a) in a pressurized inert gas, a resistivity of any value of 102 Ωα or more can be obtained at room temperature. That is, in the present invention, by appropriately combining the composition ratio of StC and A403 and the pressure of the inert gas that is the atmosphere during hot pressing, S having a resistivity of 102 to 1010 Ω at room temperature is produced.
An iC-based resistance material is obtained.

The reason why the amount of At added to SiC is limited to 20 g in the present invention is as follows. A403 plays a role as a sintering aid for KSiC other than resistivity control (However, if the amount is less than 0.2% by weight, it will not be sufficiently densified (relative density 90% or less), and it will also affect the resistivity p-value. If the amount exceeds 10% by weight, it reduces the properties of SiC, which are high strength at high temperatures and low thermal expansion.
), The reason for using an inert gas such as nitrogen (Nz) or helium (He) is that in an oxidizing atmosphere, the surface strength of SiC powder is increased to form silicon oxide (Si02), which is preferable because it does not become dense and aggregate. No. In addition, the pressure of inert gas 31
The reason for limiting the atmospheric pressure to 50 atm is that if it is lower than 1 atm, the effect of increasing resistivity will be small2.At 50 atm or higher, the increase in resistivity will be saturated, in addition to pressure vessels, etc. This is because the equipment costs are extremely high.

[Embodiments of the invention]

The present invention will now be explained in detail by way of examples.

(Example 1) A commercially available SiC powder with a purity of 98% and an average particle size of 3 μm was used, and an A40g powder with a purity of 99.9% or more and an average particle size of 0.5 μm was used. SiC powder 1 powder 92
After mixing a composition consisting of % by weight and 8% by weight of At203 powder, it was preformed into a disk with a diameter of 60 mm.

Next, the temporary formed body was placed in a graphite mold, and hot press sintered in pressurized Ar gas using a high-pressure in-air hot press device under the conditions of a load of 300 K/C1r12, a temperature of 2000 C, and a time of 1 h. Table 1 shows the relationship between the specificity of the sintered body thus obtained and the Ar gas pressure. Omoteya middle school,
Bending strength and resistivity values [ ・ 1 1 Page 1 ・ 1 [ 5°) I − As is clear from the results in Table 1, the resistivity of the sintered body increases as the Ar gas pressure increases.

Therefore, by changing the Ar gas pressure from 1 to 50 atm, the resistivity can be reduced from 103 to 10'. It can be seen that it is possible to control (goods) over a wide area of 9 meters. However, when the gas pressure exceeds 40 atmospheres, the increase in resistivity tends to reach saturation. Further, at 0.5 atm, the increase in resistivity is small compared to the comparative example described later, and no effect of sintering in pressurized gas is observed. From the above results, the preferred pressure of Ar gas is 1~
The pressure is 50 atm. The relative density and bending strength remain approximately constant even when the gas pressure changes, and no influence of gas pressure on both properties is observed.

(Example 2) The same SiC powder and A403 powder as in Example 1 were tasted,
5iC92 weight %, which is the same proportion as Example 1, A720
After mixing to 8't t% and preforming to a diameter of 60, this was heated in pressurized N2 gas under a load of 300Kq/c7n2.
Hot press sintering was carried out under the following conditions: 2000 T: ), 1 h 7). Table 2 shows the relationship between the characteristics of the obtained sintered body and the N2 gas pressure.

From the results in Table 2, it is clear that in the case of N2 gas as well, resistivity can be controlled over a wide range of 102 to 10109 m by changing the N2 gas pressure to 1 to 50 atm, similar to the case of sintering in gas. However, the resistivity value is Ar
Overall, it is about one order of magnitude smaller than in the case of gas. The relative density and bending strength are approximately constant values regardless of gas pressure.

(Comparative Example) Regarding molded bodies having the same composition as Examples 1 and 2, the atmosphere was changed from Ar or N2 gas to vacuum (io-''porr).
Instead, the load -300Kg/ as in Examples 1 and 2.
cm'', temperature 20001Z'% for 1 hour.The obtained sintered body had a relative density of 98% and a resistivity at room temperature of about 80Ω. is less than 1/4 (1 atm) to about 1/10' (50 atm) compared to the resistivity of the pressurized Ar gas shown in Table 1 and the pressurized N2 gas annealed crystal shown in Table 2. Met.

(Example 3) Using the same SiC and kkos powder as in Example 1, A
k 03 different compositions at 1 atm and 50 atm A
In r gas, 300 to 9/cm", 2000C, 1
Pot press sintering was carried out under the conditions of h. Table 3 shows the relative H degree and resistivity at room temperature of the obtained sintered body.

From the results in Table 3, it can be seen that the resistivity increases as the amount of A and Lz 03it increases and the gas pressure increases.

However, if klz Oa is less than 0.5% by weight, the relative density will be less than 90% and sufficient densification will not occur, and if it is more than 10% by weight, the resistivity will increase but the bending strength will decrease (the 3), which is not desirable.

〔Effect of the invention〕

As described above, according to the present invention, a composition made of SiC and A403 is hot-press sintered in a pressurized inert gas, so that it is dense and has a resistivity of 102 to 1010.
A SiC-based material in the Ω-saw range is obtained. In addition, this material has characteristics such as higher heat resistance, lower thermal expansion, greater mechanical strength, and thermal shock resistance than that of conventional ceramic resistance materials. Various resistors, such as temperature-sensitive resistors for high part thermistors, high-resistance elements for voltage measuring devices in special high-voltage transmission and substation systems, non-inductive resistors for thyristor protection, resistors for circuit breakers, or discharge electrodes for automatic distributors. Expected to be applied to materials, etc.Continued from page 1 @ Inventor Tetsuo Kosugi 3-1-1 Saiwaimachi, Hitachi City Hitachi Research Laboratory, Hitachi, Ltd.

Claims (1)

[Scope of Claims] 1. A sintered body obtained by hot press sintering a composition consisting of 0.5 to 10% by weight of aluminum oxide and the remainder silicon carbide in an inert gas; is a carbonized tie yarn resistance material characterized by having a relative density of 90% or more and a resistivity of 102 Ωm or more at room temperature. 2. When hot press sintering a composition consisting of 0.5 to 10% aluminum oxide and the balance silicon carbide in an inert gas, the room temperature resistivity of the sintered body is increased to 102 Ωm or more by inert gas pressure. 1. A method for producing a silicon carbide-based resistance material, characterized by controlling the amount of the silicon carbide-based resistance material. 3. The method for manufacturing a silicon carbide-based resistance material according to claim 2, wherein the inert raw gas is at least one of argon, nitrogen, and helium. 4. The method for manufacturing a silicon carbide-based resistance material according to claim 2 or 3, wherein the inert gas pressure is 1 atm or more and 50 atm or less.