JPH0461833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a translucent β-sialon sintered body and a method for producing the same. (Prior art and its problems) β-Sialon is a substance in which the Si and N positions of β-type silicon nitride are partially replaced with Al and O, respectively, and has the general formula Si _6-Z Al _Z O _Z N _8-Z (However, z is a number that satisfies 0<z≦4.2)
It is expressed as Compared to silicon nitride sintered bodies, β-SiAlON sintered bodies have excellent oxidation resistance, corrosion resistance to molten metal, and mechanical properties at high temperatures.They also exhibit translucency and have high-temperature functions. It is attracting attention as a material. Several proposals have been made for producing a translucent β-sialon sintered body. JP-A-58-9881 discloses a method of heating and incinerating a mixture of high purity silicon nitride, aluminum nitride and aluminum oxide. Furthermore, Japanese Patent Application Laid-Open No. 191064/1983 describes a method using aluminum nitride of 2 μm or less in the above method. In these methods, heating and sintering is performed by hot pressing, and a translucent β-sialon sintered body has not yet been obtained by pressureless sintering. Regarding the method for producing a β-sialon sintered body by pressureless sintering, Patent No. 1274349 describes that the first component of a mixed powder of silicon nitride, aluminum nitride, and alumina that forms a β-sialon phase is yttrium and scandium. A method has been proposed in which a mixture of an oxide of an element selected from cerium, lanthanum, and lanthanide elements and a second component is heated and sintered. However, the above specification does not mention anything about the translucency of the obtained sintered body. As will be described later, it is extremely difficult to obtain a translucent sintered body using this method. In order to obtain translucency with a polycrystal, the following two points are extremely important. That is, (1) it is sufficiently densified and has no pores, and (2) there is little glass phase in the grain boundary phase. Therefore, in order to obtain a translucent β-SiAlON sintered body using the pressureless sintering method, the amount of low-volatility liquid phase required for densification is generated during sintering, and the glass phase after sintering is reduced as much as possible. Less is more. β-Sialon particles do not become densified due to a lack of liquid phase (glass phase) in their theoretical composition. Therefore, in order to obtain the liquid phase necessary for densification, (1) 1 to 5% by weight
(2) Adding an oxide such as yttrium oxide, etc. have been considered.
In the case of (1) above, the O' or Therefore, in order to achieve complete densification, only the hot press method can be used.
In the pressureless sintering method, no matter how the atmosphere is controlled, pores remain inside the sintered body, which impedes translucency. On the other hand, regarding (2) above, in the case of sintering from a silicon nitride, aluminum nitride, alumina, and yttrium oxide mixed powder disclosed in Patent No. 1274349, SiO ₂ −Al ₂ O ₃ −Y ₂ O ₃ system A liquid phase of 5% or more consisting of is generated, and since there are few volatile components, atmospheric pressure sintering is possible. However, the formation and densification of the β-sialon phase proceed simultaneously through the liquid phase, and a large amount of glass phase ultimately remains in the sintered body, so that the sintered body is not imparted with translucency. (Object of the Invention) An object of the present invention is to provide a β-sialon sintered body that has light transmittance in addition to its excellent physical properties, and a method for producing the same. (Summary of the Invention) According to the present invention, general formula Si _6-Z Al _Z O _Z N _8-Z ...[] (However, z is a number satisfying 0<z≦4.2)
The main phase is the β-sialon phase represented by
A translucent β-sialon sintered body containing 0.1 to 5% by weight of a 15R-sialon phase and 0.1 to 5% by weight of a glass phase containing an oxide of a metal selected from yttrium and lanthanum metal elements is provided. Furthermore, according to the present invention, β represented by the above formula
- A mixed powder of β-sialon powder containing at least 90% by weight of a sialon phase and an oxide powder of a metal selected from yttrium and lanthanum metal elements in an amount of 0.1 to 2% by weight based on the β-sialon powder. Sintering at temperatures ranging from ~1850℃,
A method for manufacturing a translucent β-sialon sintered body is provided. (Specific Description of the Invention) The manufacturing method of the present invention will first be explained. The β-sialon powder used in the present invention may be any powder as long as it has β-sialon as a main phase represented by the above formula []. The powder according to the invention of No. 21267 is most suitable. This powder is prepared by mixing (a) an amorphous silicon nitride powder, (b) an oxygen-containing compound of silicon or aluminum, and (c) metallic aluminum, aluminum nitride, or silicon to a desired β-sialon composition. , the mixed powder was heated to 1300~ under nitrogen-containing atmosphere.
It can be obtained by heating to a temperature in the range of 1800°C. The β-sialon powder obtained by the above method is a fine and uniform powder with a primary particle size of 0.2 to 2 μm, and contains almost no free carbon or metal impurities, so it can be sintered without pores or abnormal grain growth. I can give my body. Metal oxides in the present invention also include oxides themselves and compounds that can be converted into metal oxides by thermal decomposition. In the following, both may be collectively referred to as metal compounds. Examples of compounds that can be converted into metal oxides by thermal decomposition include metal carbonates and metal hydroxides. The amount of the metal compound powder to be used is 0.1 to 2% by weight, preferably 0.5 to 2% by weight based on the metal oxide based on the β-sialon powder.
It is 1% by weight. If the amount of the metal compound used is less than 0.1% by weight, the sintered body will not be sufficiently densified, and conversely, if the amount used is more than 2% by weight, a large amount of glass phase will remain at the grain boundaries of the sintered body, which will prevent light from entering the sintered body. Because light is scattered,
The translucency of the sintered body becomes poor. There are no particular restrictions on the method of mixing β-Sialon powder and metal compound powder, and methods known per se may be used, such as dry mixing the two, wet mixing the two in an inert liquid, and then removing the inert liquid. The method of doing so can be adopted as appropriate. As a mixing device, a V-type mixer, a ball mill, etc. are conveniently used. The mixed powder can be heated and sintered according to a method known per se. For example, raw material powder is directly shaped into a predetermined shape using a dry or wet process, and if the wet process is used, it is dried and then sintered in a nitrogen-containing gas atmosphere under normal or pressurized pressure. A method such as filling soybeans in a predetermined shape and hot pressing may be adopted.
Further, by further hot isostatic pressing the sintered body obtained by the above method, the physical properties and translucency of the sintered body can be further improved. Molding of the raw material powder prior to normal pressure or pressure sintering is carried out by a known method, such as a rubber press method, a uniaxial molding method,
This can be carried out by a casting method, an injection molding method, an explosive compression molding method, or the like. The sintering temperature is usually 1650-1850°C, and the sintering time is usually 0.5-10 hours. If the sintering temperature is too low, sintering will not proceed and a white sintered body with remaining pores will be obtained. Furthermore, if the sintering temperature is excessively high, the sintered body undergoes a compositional change due to thermal decomposition, resulting in a loss of translucency. In the obtained translucent β-SiAlON sintered body,
It is thought to be produced by the reaction between β-sialon and metal compounds, such as yttrium oxide.
15R - Sialon and glass phases are present. As mentioned above, if the amount of metal compound used is too large, the glass phase necessary for sintering is present, so the glass phase that is thought to be caused by the above reaction is not generated, and the 15R-SiAlON phase is not formed during sintering. It will no longer be recognized. The β-sialon sintered body of the present invention has the β-sialon phase represented by the formula [] as the main phase, has almost no pores, and has little glass phase in the grain boundary phase, so it has excellent light transmittance. ing. (Example) Examples are shown below. Example 1 910.3 g of amorphous silicon nitride powder, 254.4 g of γ-alumina powder, and 119.3 g of metallic aluminum powder were mixed for 1 hour in a vibrating mill under a nitrogen gas atmosphere. Fill a carbon crucible with the mixed powder, set it in a resistance heating high temperature furnace, and heat it from room temperature under a nitrogen gas atmosphere.
1 hour up to 1200℃, 4 hours from 1200℃ to 1400℃
The mixture was crystallized by heating from 1400° C. to 1600° C. for 2 hours to obtain β-sialon powder. The properties of the obtained β-sialon powder are shown below. Specific surface area 5.4m ² /g Grain shape Equiaxed crystal formation phase β phase 95% or more Product composition (wt%) Si Al O N 39.9 19.3 11.5 29.3 Yttrium oxide is added to this β-sialon powder
After adding 0.8% by weight and wet milling for 48 hours using ethanol as a medium, vacuum drying was performed at 80°C. 15g of the obtained powder was uniaxially pressed at a pressure of 150Kg/ ^cm2 using a mold with an inner diameter of 40mm, and then
A molded product was obtained by rubber pressing at Kg/cm ² . This molded body was placed in a graphite mold, set in a high frequency induction furnace,
It was held at 1750° C. for 4 hours under a nitrogen gas atmosphere. When the obtained sintered body was examined by X-ray diffraction, it was found that β
- It was confirmed that the phase consisted of a sialon phase and a 15R-sialon phase. Furthermore, when the grain boundaries of the sintered body were analyzed using an electron microscope, it was found that yttrium atoms existed as a glass phase. When the above sintered body was ground to a thickness of 0.8 mm and its light transmittance was measured, the relationship between wavelength and transmittance was as shown in FIG. It showed a maximum transmittance of 68% for light with a wavelength of approximately 4.4 μm. Examples 2 to 7 and Comparative Examples 1 to 3 β-sialon sintering was carried out by repeating the same method as in Example 1, except that the type of metal oxide powder, the amount used, and the sintering conditions were changed as shown in Table 1. A body was produced. Table 1 shows the properties of the obtained sintered body. In Comparative Example 1, the sintering temperature was as low as 1600° C., so the material was not sufficiently densified, and the porosity was 2% or more, resulting in a white sintered body. Further, in Comparative Example 2, since the sintering temperature was as high as 1900°C, many different phases were generated, resulting in a black sintered body. Furthermore, in Comparative Example 3, since the amount of Y ₂ O ₃ added was too large, 15R-sialon was not generated, a large amount of glass phase was generated, and Y ₂ O ₃ remained, resulting in a black sintered body. It became. 【table】

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between wavelength and transmittance of the β-sialon sintered body obtained in Example 1.

Claims (1)

[Claims] 1 General formula Si _6-Z Al _Z O _Z N _8-Z (where z is a number satisfying 0<z≦4.2)
The main phase is the β-sialon phase represented by
A translucent β-sialon sintered body characterized by containing 0.1 to 5% by weight of a 15R-sialon phase and 0.1 to 5% by weight of a glass phase containing an oxide of a metal selected from yttrium and lanthanum metal elements. . 2 General formula Si _6-Z Al _Z O _Z N _8-Z (However, z is a number that satisfies 0<z≦4.2)
β-sialon powder containing at least 90% by weight of the β-sialon phase represented by; and 0.1 to 2% by weight of a metal oxide powder selected from yttrium and lanthanum metal elements based on the β-sialon powder. A method for producing a translucent β-sialon sintered body, which comprises heating and sintering a mixed powder of the above at a temperature in the range of 1650 to 1850°C.