JPH0316903A - Production of crystalline silicon nitride powder - 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 (Industrial Application Field) The present invention relates to a method for producing crystalline silicon nitride powder suitable as a raw material for producing a silicon nitride sintered body useful as a material for high-temperature structures.

(Prior art and its problems) A method for producing crystalline silicon nitride powder by burning amorphous silicon nitride powder and/or nitrogen-containing silane compound in an inert gas atmosphere or a reducing gas atmosphere is as follows: Already known. By the way, in this method, a large number of acicular or columnar crystals are produced during sintering, so the resulting crystalline silicon nitride powder has a low packing density, and when it is used as a raw material for sintering, it is bulky. The disadvantage is that only a molded body with low density can be obtained.

Therefore, as a method for producing crystalline silicon nitride powder consisting of fine granular particles, JP-A-59-21506 discloses a method of grinding an amorphous silicon nitride powder and/or a nitrogen-containing silane compound before firing. , and a method has been proposed in which the object to be burned is held at a temperature in the range of 1250 to 1430"C for one hour or more during the temperature raising process δ.

According to this method, it is possible to produce crystalline silicon nitride powder consisting of fine granular particles, but it is difficult to control the grinding conditions, and the heating schedule is complicated and firing takes a long time, resulting in low productivity. There was a problem of low

(Objective of the Invention) An object of the present invention is to solve the above-mentioned problems and to provide a new manufacturing method capable of producing high-quality crystalline silicon nitride powder with a constant particle shape and size at a low cost.

(Means for Solving the Problems) The present invention provides crystalline silicon nitride powder by burning amorphous silicon nitride powder and/or nitrogen-containing silane compound in an inert gas atmosphere or a reducing gas atmosphere. When manufacturing,
The present invention relates to a method for producing crystalline silicon nitride powder, which is characterized by subjecting an amorphous silicon nitride powder and/or a nitrogen-containing silane compound to surface treatment by plasma nitriding before firing.

As the nitrogen-containing silane compound in the present invention, silicon dihydride, silicon tetraamide, silicon nitrogen imide, silicon chlorimide, etc. are used. These can be prepared using known methods such as silicon tetrachloride, silicon tetrabromide,
It is produced by a method in which a silicon halide such as silicon tetraiodide and ammonia are reacted in a gas phase, a method in which a liquid silicon halide is reacted with liquid ammonia, and the like.

In addition, amorphous silicon nitride powder can be produced by a known method, for example, a method of thermally decomposing the nitrogen-containing silane compound at a temperature in the range of 600 to 1200"C in a nitrogen or ammonia gas atmosphere, silicon tetrachloride, tetrabromide, etc. Those manufactured by a method of reacting a silicon halide such as silicon or silicon tetraiodide with ammonia at high temperature are used.The average particle diameter of the amorphous silicon nitride powder and the nitrogen-containing silane compound is as follows:
Usually O. O O 5-0. It is 0.5 um.

In the present invention, the amorphous silicon nitride powder and/or the nitrogen-containing silane compound are surface-treated by plasma nitriding before firing.

Plasma is an electrically neutral conductive gas population in which positively and negatively charged particles coexist. There are low-temperature plasmas that are in a thermally non-equilibrium state in which only the temperature rises to tens of thousands of degrees Celsius and the ions and atoms are at room temperature, and both are used in the present invention.

Various plasma generation methods are used, such as DC arc plasma, high frequency induction plasma, hybrid plasma combining these, ECR magnetron discharge, and ion plating.

As the reactive gas in the plasma nitriding method, nitrogen or a nitrogen-containing compound gas such as ammonia or hydrazine is used. According to this method, the oxide that inevitably exists on the particle surface of the amorphous silicon nitride and/or nitrogen-containing silane compound is nitrided by extracting oxygen atoms.

Plasma treatment conditions vary depending on the plasma generator, the type of reactive gas, and the amount of amorphous silicon nitride powder and/or nitrogen-containing silane compound, and cannot be uniformly specified, but the It is sufficient to select conditions that will result in 1 to 50 people.

By plasma-treating the amorphous silicon nitride powder and/or the nitrogen-containing silane compound, the particle surface is significantly activated, and the crystallization rate of silicon nitride during annealing is increased.
Moreover, fine granular particles can be obtained efficiently. Although the reason for this is not yet clear, it is thought that plasma treatment increases the number of defects on the particle surface and changes the electronic state of surface atoms.

In the present invention, the plasma-treated amorphous silicon nitride powder and/or the nitrogen-containing silane compound are fired under an inert gas atmosphere or a reducing gas atmosphere.

Examples of the inert gas include nitrogen, argon, helium, and the like. Further, examples of the reducing gas include hydrogen, ammonia, carbon monoxide, and the like.

The firing temperature is preferably in the range of 1350 to 1700''C.

If the sintering temperature is lower than 1350°C, crystallization of silicon nitride will not proceed sufficiently. Further, if the sintering temperature exceeds 1700°C, it is not preferable because the raw silicon nitride powder starts to decompose. Moreover, rapid temperature rise is not preferable in terms of making the particle shape uniform, and it is desirable to slowly raise the temperature in the range of 1150 to 1350°C over one hour or more.

(Example) Examples and comparative examples are shown below to further specifically explain the present invention. In the Examples and Comparative Examples, the crystallinity of the crystalline silicon nitride powder was determined according to the Ceramic Industry Association Journal, Vol. 93, p. 394-3.
According to the hydrolysis test described in 97 (1985), the α-type crystal content was determined as follows:
-780 (1977), and the specific surface area was measured by the BET method using nitrogen gas adsorption method.

Example I Amorphous silicon nitride powder 5 with a specific surface area of 390 ffl/g obtained by thermally decomposing silicon diimide at 1000°C
0 g was filled into a container in a capacitively coupled cylindrical plasma device, and the container was rotated to fluidize the powder. 'Next, the inside of the bell jar is 0. After vacuum degassing to below 0.5 Torr, nitrogen gas was introduced to reduce the pressure in the system to l. Q To
I kept it at rr. A high frequency wave with an output of 100 W was applied to the discharge coil from a high frequency oscillator with a frequency of 13.56 MHz to generate nitrogen plasma, and plasma treatment was performed for 20 minutes.

The treated powder was filled into a graphite crucible, heated to 1500° C. under a nitrogen atmosphere, and held for 1 hour.

Table 1 shows the properties of the obtained silicon nitride powder.

Examples 2 to 3 Silicon nitride powder was produced in the same manner as in Example 1, except that the plasma treatment was performed under the conditions shown in Table 1.

Table 1 shows the properties of the obtained silicon nitride powder.

Example 4 50 g of a mixed powder of amorphous silicon nitride with a specific surface area of 480 rrf/g obtained by thermally decomposing silicon diimide at 700° C. and an undecomposed nitrogen-containing silane compound was placed in a container in a microwave plasma device. Fill and fluidize the powder.

After evacuating the inside of the bell jar to a high vacuum of 2X10-'Torr or less, nitrogen gas was introduced to reduce the pressure inside the system to O. O ■T
I kept it at orr. Next, 2.45 GHz microwaves (output 180 W) generated by a magnetron were introduced into the discharge chamber through the waveguide to generate nitrogen plasma.
Plasma treatment was performed for 15 minutes.

The treated powder was filled into a graphite crucible, heated to 1550° C. under a nitrogen atmosphere, and held for 30 minutes.

Table 1 shows the properties of the obtained silicon nitride powder.

Example 5 Silicon nitride powder was produced in the same manner as in Example 4, except that the plasma treatment was performed under the conditions shown in Table 1.

Table I shows the properties of the silicon nitride powder obtained.

Comparative Examples 1-2 Silicon nitride powder was produced in the same manner as in Example 1 and Example 4, except that the plasma treatment was not performed.

Table 1 shows the properties of the obtained silicon nitride powder.

(Effects of the Invention) According to the present invention, crystalline silicon nitride powder that is made of equiaxed granular particles, has a large tap density, and has good filling properties can be manufactured with high productivity, and costs can be reduced. Become.

Claims (1)

[Claims] When producing crystalline silicon nitride powder by firing amorphous silicon nitride powder and/or nitrogen-containing silane compound under an inert gas atmosphere or a reducing gas atmosphere, the amorphous silicon nitride powder and/or nitrogen-containing silane compound are fired before firing. A method for producing crystalline silicon nitride powder, which comprises surface-treating/or a nitrogen-containing silane compound by plasma nitriding.