WO2022202621A1 - Silicon nitride powder and method for producing same, and silicon nitride sintered body and method for producing same - Google Patents

Silicon nitride powder and method for producing same, and silicon nitride sintered body and method for producing same Download PDF

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WO2022202621A1
WO2022202621A1 PCT/JP2022/012341 JP2022012341W WO2022202621A1 WO 2022202621 A1 WO2022202621 A1 WO 2022202621A1 JP 2022012341 W JP2022012341 W JP 2022012341W WO 2022202621 A1 WO2022202621 A1 WO 2022202621A1
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silicon nitride
powder
mass
raw material
nitride powder
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PCT/JP2022/012341
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French (fr)
Japanese (ja)
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直嗣 野上
稔男 田中
豪 竹田
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デンカ株式会社
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Priority to JP2022545936A priority Critical patent/JP7239787B2/en
Priority to CN202280021892.6A priority patent/CN117120397A/en
Publication of WO2022202621A1 publication Critical patent/WO2022202621A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/068—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with silicon
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
    • C04B35/587—Fine ceramics

Definitions

  • the present disclosure relates to a silicon nitride powder and its manufacturing method, and a silicon nitride sintered body and its manufacturing method.
  • Silicon nitride is a material with excellent strength, hardness, toughness, heat resistance, corrosion resistance, thermal shock resistance, etc., so it is used for various industrial parts such as die casting machines and melting furnaces, and automobile parts. .
  • the use of silicon nitride substrates as insulating substrates for power modules of automobiles, machine tools, etc. is also under study. For such applications, high heat dissipation is required. Therefore, Patent Document 1 proposes the use of silicon nitride powder with reduced impurities in order to obtain a silicon nitride sintered body having high thermal conductivity.
  • the present disclosure provides a silicon nitride powder with sufficiently reduced impurities and capable of producing a sintered body having excellent mechanical properties, and a method for producing the same. Also provided are a silicon nitride sintered body in which impurities are sufficiently reduced and which has excellent mechanical properties, and a method for producing the same.
  • the present disclosure provides a silicon nitride powder having a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and a ⁇ conversion rate of 80% or more.
  • This silicon nitride powder has sufficiently low fluorine and carbon contents and a high alpha conversion rate.
  • This silicon nitride powder has sufficiently reduced impurities and can be used for various purposes. For example, if this silicon nitride powder is used for a sintered body, a sintered body having excellent mechanical properties can be obtained.
  • the ⁇ conversion rate of the silicon nitride powder may be 90% or more. By using this silicon nitride powder as a raw material for sintering, a sintered body having high fracture toughness can be obtained.
  • the silicon nitride powder may have a ⁇ conversion rate of 98% or less. This can reduce the manufacturing cost of the silicon nitride powder.
  • the present disclosure includes a raw material powder containing a silicon powder and having a fluoride content of 1 part by mass or less with respect to 100 parts by mass of the silicon powder, having a bulk density of 0.7 g/cm 3 or more and a filling height of the raw material powder of A filling step of filling the container so as to have a thickness of 15 to 80 mm, a firing step of firing the raw material powder filled in the container in an atmosphere containing nitrogen gas to obtain a fired product containing silicon nitride, and a firing step of obtaining a fired product. and a pulverizing step of pulverizing.
  • raw material powder having a fluoride content of 1 part by mass or less is filled into a container to a predetermined bulk density and filling height, and fired in an atmosphere containing nitrogen gas. Therefore, the nitriding reaction proceeds appropriately, and a silicon nitride powder having a high alpha conversion rate and a reduced fluorine content can be obtained.
  • This silicon nitride powder has sufficiently reduced impurities and can be used for various purposes. For example, if it is used for a sintered body, a sintered body having excellent mechanical properties can be produced at low cost.
  • the firing process may be performed in an atmosphere containing nitrogen gas and hydrogen gas. This promotes the formation of silicon nitride, and a silicon nitride powder having high purity can be obtained in a short firing time. Therefore, the manufacturing cost of silicon nitride powder can be reduced.
  • the carbon content in the raw material powder may be 0.1% by mass or less. This makes it possible to obtain a silicon nitride powder having a low carbon content and a high alpha conversion rate. By using such a silicon nitride powder as a raw material for sintering, a sintered body having excellent mechanical properties can be obtained.
  • the silicon nitride powder may have a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and an ⁇ conversion rate of 80% or more.
  • the present disclosure provides a method for producing a silicon nitride sintered body, which has a sintering step of molding and firing a sintering raw material containing the silicon nitride powder produced by any of the above production methods. According to this manufacturing method, a silicon nitride sintered body having excellent mechanical properties can be manufactured at low cost.
  • the present disclosure provides a silicon nitride sintered body having a fluorine content of 600 mass ppm or less and a carbon content of 0.1 mass% or less.
  • This silicon nitride sintered body has sufficiently reduced impurities and has excellent mechanical properties.
  • the silicon nitride powder (Si 3 N 4 powder) according to one embodiment has a fluorine content of 600 mass ppm or less and a carbon content of 0.1 mass ppm or less.
  • a sintered body obtained by using such a silicon nitride powder as a sintering raw material has sufficiently high bending strength at room temperature (20° C.) and high temperature (1300° C.). Moreover, since the contents of fluorine and carbon are sufficiently low, it can be suitably used for various applications without being limited to sintered bodies.
  • the fluorine content of the silicon nitride powder may be 300 mass ppm or less, 100 mass ppm or less, or even 60 mass ppm or less. good. From the viewpoint of ease of production, the fluorine content may be 5 mass ppm or more, 10 mass ppm or more, or 30 mass ppm or more. An example of the fluorine content of silicon nitride powder is 5 to 600 mass ppm.
  • the carbon content of the silicon nitride powder is 0.1% by mass or less.
  • a sintered body obtained by using such a silicon nitride powder as a sintering raw material has sufficiently high bending strength at room temperature (20° C.) and high temperature (1300° C.).
  • the carbon content of the silicon nitride powder may be 0.08% by mass or less, may be 0.07% by mass or less, and may be 0.06% by mass. % or less.
  • the carbon content of the silicon nitride powder may be 0.01% by mass or more, or may be 0.02% by mass or more.
  • An example of the carbon content of silicon nitride powder is 0.01 to 0.1% by mass.
  • the carbon contained in the silicon nitride powder is derived from the organic binder and the material of the container when molding the raw material powder. Normally, even if the raw material powder is fired as it is, the nitriding does not progress sufficiently, so it may be fired as a compact. At this time, a binder such as polyvinyl alcohol is used to ensure moldability. By changing the amount of the binder used, the carbon content of the silicon nitride powder can be adjusted. The carbon content of the silicon nitride powder can be determined by the "combustion (high-frequency heating) - infrared absorption method" in "11 carbon determination method" of JIS R 1603:2007. In addition, when manufacturing the silicon nitride powder of this embodiment, it is not necessary to use an organic binder.
  • the purity of the silicon nitride powder may be 99% by mass or higher, 99.5% by mass or higher, or 99.8% by mass or higher.
  • the ⁇ conversion rate of the silicon nitride powder (the phase ratio of ⁇ -Si 3 N 4 to the whole Si 3 N 4 ) is 80% or more.
  • a sintered body obtained by using such a silicon nitride powder as a sintering raw material has excellent mechanical properties. From the viewpoint of further improving the fracture toughness, the alpha conversion rate of the silicon nitride powder may be 85% or more, 88% or more, or 90% or more.
  • the ⁇ conversion rate of the silicon nitride powder may be 98% or less, 97% or less, or 96% or less.
  • An example of the ⁇ conversion rate of silicon nitride powder is 80 to 98%.
  • the ⁇ conversion rate of the silicon nitride powder (the phase ratio of ⁇ -Si 3 N 4 to the entire Si 3 N 4 ) may be 20% or less, preferably 15% or less, from the viewpoint of sufficiently increasing the alpha conversion rate. may be 12% or less, or may be 10% or less.
  • the ⁇ conversion rate of the silicon nitride powder may be 2% or more, or may be 4% or more, from the viewpoint of ease of production.
  • the alpha conversion rate of silicon nitride powder depends on the firing conditions. If the nitriding reaction of the raw material powder proceeds appropriately, it is possible to obtain a silicon nitride powder having a high degree of alpha conversion. On the other hand, if the nitriding reaction of the raw material powder progresses rapidly or the contact between the raw material powders is insufficient, the ⁇ conversion rate tends to decrease.
  • the ⁇ conversion rate of the silicon nitride powder can be obtained from the diffraction line intensity of X-ray diffraction.
  • a method for producing a silicon nitride powder includes a raw material powder containing silicon powder and having a fluoride content of 1 part by mass or less with respect to 100 parts by mass of the silicon powder, and having a bulk density of 0.7 g/cm 3 or more. , and a filling step of filling the container so that the filling height of the raw material powder is 15 to 80 mm, and firing the raw material powder filled in the container in an atmosphere containing nitrogen gas, and firing containing silicon nitride It has a sintering step of obtaining a product and a pulverizing step of pulverizing the sintered product.
  • the raw material powder may contain a fluoride containing Li, Na, K, Mg, Ca, Sr or Ba as a constituent element in order to promote nitridation.
  • the content of fluoride with respect to 100 parts by mass of the silicon powder may be 0.5 parts by mass or less, or 0.3 parts by mass or less. good.
  • the raw material powder may not contain fluoride. If necessary, the silicon powder may be pretreated with an acid to reduce impurities in the silicon powder.
  • the silicon nitride powder can be produced without using an organic binder. Therefore, a silicon nitride powder with a sufficiently low carbon content can be produced.
  • the carbon content of the raw material powder may be 0.1% by mass or less.
  • the carbon content in the raw material powder can be determined by the "combustion (high-frequency heating) - infrared absorption method" in "11 carbon determination method" of JIS R 1603:2007.
  • the container filled with the raw material powder can be made of a material that does not change in quality up to a temperature of 1500°C under an inert atmosphere.
  • the container can be made of alumina, boron nitride, or carbon.
  • the structure of the container is not particularly limited, and for example, a container capable of forming an accommodation space for accommodating the raw material powder can be used.
  • the container body may include a container body having a recess and a lid covering the recess of the body.
  • a container is filled with the raw material powder so that the bulk density of the raw material powder is 0.7 g/cm 3 or more.
  • the nitridation of the silicon powder proceeds appropriately, and a silicon nitride powder having a high alpha conversion rate can be obtained.
  • the bulk density of the raw material powder in the container may be 0.8 g/cm 3 or more, or 0.9 g/cm 3 or more.
  • the bulk density of the raw material powder in the container may be 1.6 g/cm 3 or less, 1.2 g/cm 3 or less, or 1.0 g/cm 3 or less.
  • the calorific value tends to increase and the amount of ⁇ -Si 3 N 4 phase produced tends to increase. In addition, it may become difficult to fill the container.
  • An example of the bulk density of the raw material powder in the container is 0.7-1.6 g/cm 3 .
  • the filling height (thickness in the vertical direction) of the raw material powder in the container is 15 to 80 mm, and may be 20 to 60 mm. With such a filling height, the nitriding reaction proceeds smoothly.
  • the filling height of the raw material powder can be measured as the height along the vertical direction from the bottom of the container.
  • the raw material powder filled in the container is fired in an atmosphere containing nitrogen gas to nitride the silicon powder contained in the raw material powder.
  • concentration of nitrogen gas in the atmosphere during firing may be 90% by volume or more, 95% by volume or more, or 97% by volume or more.
  • the atmosphere during firing may contain nitrogen gas and other gases different from nitrogen gas.
  • gases include argon gas and hydrogen gas.
  • argon gas By adding argon gas, the reaction rate of the nitriding reaction can be adjusted.
  • hydrogen gas By adding hydrogen gas, oxides such as SiO 2 contained in the raw material powder can be reduced, and silicon nitride powder having high purity can be produced.
  • the content of hydrogen gas in the atmosphere during firing may be 1% by volume or more, or may be 2% by volume or more.
  • the content of hydrogen gas in the atmosphere during firing may be 5% by volume or less.
  • An example of the content of hydrogen gas in the atmosphere during firing is 1 to 5% by volume.
  • Gas content (% by volume) in this specification is a value under standard conditions (0° C., 1 atm).
  • the firing process may include multiple stages with different firing temperature ranges.
  • the multiple stages may include the following first stage and second stage.
  • the temperature is raised to the temperature range (1) of 1100 to 1200° C. and maintained. If the holding temperature in the first stage is too low, the nitriding reaction tends to be difficult to proceed. On the other hand, if the holding temperature in the first stage is too high, the nitriding reaction proceeds rapidly, increasing the amount of ⁇ -Si 3 N 4 ( ⁇ phase) produced.
  • the holding time in temperature range (1) may be from 2 to 12 hours. If the holding time is too short, the nitriding reaction may not proceed sufficiently. If the holding time is too long, the productivity of the silicon nitride powder will decrease.
  • the temperature is raised to the temperature range (2) of 1400-1500°C and maintained.
  • the temperature range (2) of 1400-1500°C and maintained.
  • unreacted Si can be sufficiently reduced. If the holding temperature in this second stage is too low, the residual amount of unreacted Si tends to increase. On the other hand, if the holding temperature in this second stage is too high, the resulting silicon nitride tends to undergo a transition from the ⁇ -phase to the ⁇ -phase.
  • the holding time in temperature range (2) may be from 1 to 8 hours. If the holding time is too short, unreacted Si tends to remain. If the holding time is too long, the productivity of the silicon nitride powder will decrease.
  • a pulverizing step of pulverizing the fired product obtained in the firing step is performed. Pulverization may be performed in multiple steps of coarse pulverization and fine pulverization. Grinding may be performed wet, for example using a ball mill. The fired product may be pulverized until the specific surface area reaches 8.0 to 15.0 m 2 /g.
  • a silicon nitride powder having a low fluorine content and a low carbon content and a high alpha conversion rate For example, a silicon nitride powder having a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass % or less, and a ⁇ conversion rate of 80% or more can be obtained. Since such silicon nitride powder has a low impurity concentration, it can be suitably used for various purposes. For example, by using it as a raw material for sintering, a sintered body having excellent mechanical properties can be obtained.
  • the ⁇ conversion rate may be 85% or more, 88% or more, or 90% or more.
  • the ⁇ conversion rate may be 98% or less, 97% or less, or 96% or less.
  • An example of the ⁇ conversion rate range is 80 to 98%.
  • a treatment process may be performed as necessary.
  • the pulverized fired product and hydrofluoric acid having a hydrogen fluoride concentration of 10 to 40% by mass may be blended to reduce impurities.
  • the pulverized fired product may be dispersed in hydrofluoric acid for treatment.
  • the concentration of hydrogen fluoride in hydrofluoric acid may be 15-30% by mass.
  • the temperature of hydrofluoric acid in the treatment step is, for example, 40-80.degree.
  • the time for immersing the silicon nitride powder in hydrofluoric acid is, for example, 1 to 10 hours.
  • the sintering raw material is pressed with a molding pressure of, for example, 3.0 to 30 MPa to obtain a compact.
  • the compact may be produced by uniaxial pressing or may be produced by CIP. Moreover, you may bake while shape
  • the firing temperature may be 1860-2100°C, or 1880-2000°C.
  • the firing time at the firing temperature may be 6 to 20 hours, or 8 to 16 hours.
  • the heating rate to the firing temperature may be, for example, 1.0 to 10.0° C./hour.
  • the silicon nitride sintered body produced in this way has a low production cost and excellent mechanical properties. In addition, since impurities are reduced, it can be used for various purposes.
  • the silicon nitride sintered body has a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and a alpha conversion rate of 80% or more.
  • the fluorine content of the silicon nitride sintered body may be 300 mass ppm or less, 100 mass ppm or less, or 60 mass ppm or less. There may be. From the viewpoint of ease of manufacture, the fluorine content of the silicon nitride sintered body may be 5 mass ppm or more, 10 mass ppm or more, or 30 mass ppm or more. An example of the fluorine content of the silicon nitride sintered body is 5 to 600 mass ppm.
  • Such a silicon nitride sintered body can be produced using a sintering raw material having a fluorine content within the above range.
  • the carbon content of the silicon nitride sintered body is 0.1% by mass or less.
  • Such a silicon nitride sintered body has sufficiently high bending strength at room temperature (20° C.) and high temperature (1300° C.). From the viewpoint of obtaining a silicon nitride sintered body having higher bending strength, the carbon content of the silicon nitride sintered body may be 0.08% by mass or less, or 0.07% by mass or less, It may be 0.06% by mass or less. From the viewpoint of ease of manufacture, the carbon content of the silicon nitride sintered body may be 0.01% by mass or more, or may be 0.02% by mass or more.
  • Such a silicon nitride sintered body can be produced using a sintering raw material having a carbon content within the above range.
  • the fluorine and carbon contents of the silicon nitride sintered body can be measured in the same manner as the silicon nitride powder using a sample obtained by pulverizing the silicon nitride sintered body into powder.
  • silicon nitride powder may be used as a raw material for sintering composite sintered bodies of silicon nitride and other substances. Moreover, you may use for uses other than a sintering raw material.
  • a raw material powder was prepared by blending 1 part by mass of fluorite with 100 parts by mass of silicon powder. That is, the raw material powder contained 1 part by mass of fluoride (fluorite) with respect to 100 parts by mass of silicon powder.
  • the carbon content in the raw material powder was 0.1% by mass or less.
  • An alumina container having a main body with a recess and a lid was prepared. The recess was filled with raw material powder.
  • the bulk density of the raw material powder after filling was 1 g/cm 3 .
  • the filling shape of the raw material powder was a rectangular parallelepiped, and the filling height was 45 mm.
  • the concave portion of the main body was covered with a lid, and the raw material powder was placed in an alumina container.
  • the raw material powder accommodated in the container was sintered in the following procedure.
  • Example 1 The obtained ingot was coarsely pulverized and then wet-pulverized with a ball mill. After that, it was dried under a nitrogen atmosphere. Thus, the silicon nitride powder of Example 1 was prepared.
  • the fluorine content of the silicon nitride powder was measured in the following manner.
  • the silicon nitride powder was heated using an automatic sample combustion apparatus (manufactured by Mitsubishi Chemical Corporation, device name: AQF-2100H type), and the generated gas was dissolved in water. Fluorine dissolved in water was measured using an ion chromatograph (manufactured by Thermo Fisher Scientific, device name: ICS-2100). Based on this measured value, the fluorine content of the silicon nitride powder was calculated.
  • the carbon content of the silicon nitride powder was measured by the "combustion (high-frequency heating) - infrared absorption method" in "11 carbon determination method” of JIS R 1603:2007.
  • CS-444LS trade name manufactured by LECO was used for the measurement.
  • the sample (silicon nitride powder) was combusted together with the combustion aid by high-frequency heating.
  • the carbon content in the sample was measured by quantifying the generated carbon dioxide by an infrared absorption method.
  • the bending strength is a three-point bending bending strength, and was measured using a commercially available bending strength meter (manufactured by Shimadzu Corporation, device name: AG-2000) in accordance with JIS R 1601:2008. Measurements were taken at room temperature (20°C) and 1300°C. The results (relative values) were as shown in Table 1.
  • the fracture toughness (K IC ) is a value measured by the SEPB method, and was measured using a commercially available measuring device (manufactured by Instron, device name: universal testing machine 5582) in accordance with JIS R1607:2015. The results (relative values) were as shown in Table 1.
  • Example 3 Example 1 except that fluoride (fluorite) was not blended during the preparation of the raw material powder, and the atmosphere during firing was the same mixed gas of nitrogen gas and hydrogen gas as in Example 2.
  • a silicon nitride powder was prepared in the same manner. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 1. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 1.
  • Example 5 The temperature conditions for firing the raw material powder were as follows. The temperature was raised to 1150°C at a temperature elevation rate of 5°C/min. After holding the temperature at 1150° C. for 12 hours, the temperature was raised to 1450° C. at a rate of 0.018° C./min. After being held at a temperature of 1450° C. for 4 hours, it was naturally cooled to room temperature. A silicon nitride powder was prepared in the same manner as in Example 1, except that the temperature conditions during firing were set as described above. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 1. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 1.
  • Example 1 A silicon nitride powder was prepared in the same manner as in Example 1, except that the amount of fluoride (fluorite) mixed with 100 parts by mass of the silicon powder was 2 parts by mass during the preparation of the raw material powder.
  • the silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2.
  • a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
  • Example 2 A raw material powder was prepared in the same manner as in Example 1, except that the amount of fluoride (fluorite) mixed with 100 parts by mass of the silicon powder was 0.2 parts by mass. 5 parts by mass of polyvinyl alcohol was blended with 100 parts by mass of this raw material powder to obtain a kneaded material. This kneaded material was molded using a high-temperature press to obtain a molded body. Firing was carried out in the same manner as in Example 2, except that a compact was used instead of the container, and that the rate of temperature increase from 1150°C to 1450°C was changed to 0.035°C/min. to prepare silicon nitride powder. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
  • Example 3 A raw material powder was prepared in the same manner as in Example 1, except that the amount of fluoride (fluorite) mixed with 100 parts by mass of silicon powder was 1 part by mass. 5 parts by mass of polyvinyl alcohol was blended with 100 parts by mass of this raw material powder to obtain a kneaded material. This kneaded material was molded using a high-temperature press to obtain a molded body. Silicon nitride powder was prepared in the same manner as in Comparative Example 2, except that this compact was used and the atmosphere during firing was changed to nitrogen gas only.
  • fluoride fluorite
  • the silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
  • Silicon nitride powder was prepared in the same manner as in Example 1, except that the filling height and filling density of the raw material powder in the container were changed as shown in Table 2.
  • the silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2.
  • a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
  • the bending strength and fracture toughness in Tables 1 and 2 are relative values based on Comparative Example 3. It was confirmed that the silicon nitride sintered bodies of Examples 1-5 had better mechanical properties than the silicon nitride sintered bodies of Comparative Examples 1-4. It is considered that the carbon contained in the silicon nitride powder of each example was unavoidably mixed from raw materials and manufacturing equipment.
  • a silicon nitride powder and a method for producing the same which have sufficiently reduced impurities and are capable of producing a sintered body having excellent mechanical properties. It is possible to provide a method for producing a silicon nitride sintered body that can produce a silicon nitride sintered body having excellent mechanical properties.

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Abstract

Provided is a silicon nitride powder which contains fluorine in an amount of not more than 600 mass ppm and carbon in an amount of not more than 0.1 mass% and which has an α-conversion rate of not less than 80%. Also provided is a method for producing a silicon nitride powder, said method comprising: a filling step for filling a container with a raw material powder so that bulk density is not less than 0.7 g/cm3 and the filling height of the raw material powder is 15-80 mm, the raw material powder containing a silicon powder and containing fluoride in an amount of not more than 1 part by mass with respect to 100 parts by mass of the silicon powder; a firing step for firing the raw material powder with which the container is filled in an atmosphere containing nitrogen gas to obtain a fired product containing silicon nitride; and a crushing step for crushing the fired product.

Description

窒化ケイ素粉末及びその製造方法、並びに、窒化ケイ素焼結体及びその製造方法Silicon nitride powder and method for producing the same, and sintered silicon nitride and method for producing the same
　本開示は、窒化ケイ素粉末及びその製造方法、並びに、窒化ケイ素焼結体及びその製造方法に関する。 The present disclosure relates to a silicon nitride powder and its manufacturing method, and a silicon nitride sintered body and its manufacturing method.
　窒化ケイ素は、強度、硬度、靭性、耐熱性、耐食性、耐熱衝撃性等に優れた材料であることから、ダイカストマシン及び溶解炉等の各種産業用の部品、及び自動車部品等に利用されている。窒化ケイ素基板は、自動車及び工作機械等のパワーモジュール等の絶縁基板としての利用も検討されている。このような用途では、高い放熱性を有することが求められる。そこで、特許文献１では、高い熱伝導率を有する窒化ケイ素焼結体を得るために、不純物が低減された窒化ケイ素粉末を用いることが提案されている。 Silicon nitride is a material with excellent strength, hardness, toughness, heat resistance, corrosion resistance, thermal shock resistance, etc., so it is used for various industrial parts such as die casting machines and melting furnaces, and automobile parts. . The use of silicon nitride substrates as insulating substrates for power modules of automobiles, machine tools, etc. is also under study. For such applications, high heat dissipation is required. Therefore, Patent Document 1 proposes the use of silicon nitride powder with reduced impurities in order to obtain a silicon nitride sintered body having high thermal conductivity.
国際公開第２０２０／２０３６９７号WO2020/203697
　本開示では、不純物が十分に低減されており、優れた機械的特性を有する焼結体を製造することが可能な窒化ケイ素粉末及びその製造方法を提供する。また、不純物が十分に低減されており、優れた機械的特性を有する窒化ケイ素焼結体及びその製造方法を提供する。 The present disclosure provides a silicon nitride powder with sufficiently reduced impurities and capable of producing a sintered body having excellent mechanical properties, and a method for producing the same. Also provided are a silicon nitride sintered body in which impurities are sufficiently reduced and which has excellent mechanical properties, and a method for producing the same.
　本開示は、フッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下であり、α化率が８０％以上である窒化ケイ素粉末を提供する。この窒化ケイ素粉末は、フッ素及び炭素の含有量が十分に低く、α化率が高い。この窒化ケイ素粉末は、不純物が十分に低減されているため、種々の用途に用いることができる。例えば、この窒化ケイ素粉末を焼結体用にすれば、優れた機械的特性を有する焼結体を得ることができる。 The present disclosure provides a silicon nitride powder having a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and a α conversion rate of 80% or more. This silicon nitride powder has sufficiently low fluorine and carbon contents and a high alpha conversion rate. This silicon nitride powder has sufficiently reduced impurities and can be used for various purposes. For example, if this silicon nitride powder is used for a sintered body, a sintered body having excellent mechanical properties can be obtained.
　窒化ケイ素粉末のα化率は９０％以上であってよい。焼結原料として、この窒化ケイ素粉末を用いることによって、高い破壊靭性を有する焼結体を得ることができる。窒化ケイ素粉末のα化率は９８％以下であってよい。これによって、窒化ケイ素粉末の製造コストを低減することができる。 The α conversion rate of the silicon nitride powder may be 90% or more. By using this silicon nitride powder as a raw material for sintering, a sintered body having high fracture toughness can be obtained. The silicon nitride powder may have a α conversion rate of 98% or less. This can reduce the manufacturing cost of the silicon nitride powder.
　本開示は、ケイ素粉末を含み、ケイ素粉末１００質量部に対するフッ化物の含有量が１質量部以下である原料粉末を、かさ密度が０．７ｇ／ｃｍ３以上、且つ原料粉末の充填高さが１５～８０ｍｍになるように容器に充填する充填工程と、容器に充填された原料粉末を、窒素ガスを含む雰囲気中で焼成して、窒化ケイ素を含む焼成物を得る焼成工程と、焼成物を粉砕する粉砕工程と、を有する、窒化ケイ素粉末の製造方法を提供する。 The present disclosure includes a raw material powder containing a silicon powder and having a fluoride content of 1 part by mass or less with respect to 100 parts by mass of the silicon powder, having a bulk density of 0.7 g/cm 3 or more and a filling height of the raw material powder of A filling step of filling the container so as to have a thickness of 15 to 80 mm, a firing step of firing the raw material powder filled in the container in an atmosphere containing nitrogen gas to obtain a fired product containing silicon nitride, and a firing step of obtaining a fired product. and a pulverizing step of pulverizing.
　この製造方法では、フッ化物の含有量が１質量部以下である原料粉末を、容器に所定のかさ密度且つ充填高さとなるように充填し、窒素ガスを含む雰囲気中で焼成を行う。このため、適度に窒化反応が進行し、高いα化率を有するとともにフッ素の含有量が低減された窒化ケイ素粉末を得ることができる。この窒化ケイ素粉末は、不純物が十分に低減されているため、種々の用途に用いることができる。例えば、焼結体用にすれば、優れた機械的特性を有する焼結体を低コストで製造することができる。 In this manufacturing method, raw material powder having a fluoride content of 1 part by mass or less is filled into a container to a predetermined bulk density and filling height, and fired in an atmosphere containing nitrogen gas. Therefore, the nitriding reaction proceeds appropriately, and a silicon nitride powder having a high alpha conversion rate and a reduced fluorine content can be obtained. This silicon nitride powder has sufficiently reduced impurities and can be used for various purposes. For example, if it is used for a sintered body, a sintered body having excellent mechanical properties can be produced at low cost.
　上記焼成工程は、窒素ガスと水素ガスとを含む雰囲気中で行ってもよい。これによって、窒化ケイ素の生成を促進し、短い焼成時間で高い純度を有する窒化ケイ素粉末を得ることができる。したがって、窒化ケイ素粉末の製造コストを低減することができる。 The firing process may be performed in an atmosphere containing nitrogen gas and hydrogen gas. This promotes the formation of silicon nitride, and a silicon nitride powder having high purity can be obtained in a short firing time. Therefore, the manufacturing cost of silicon nitride powder can be reduced.
　上記原料粉末における炭素の含有量が０．１質量％以下であってよい。これによって、炭素の含有量が低く、高いα化率を有する窒化ケイ素粉末を得ることができる。このような窒化ケイ素粉末を焼結原料として用いることによって、優れた機械的特性を有する焼結体を得ることができる。 The carbon content in the raw material powder may be 0.1% by mass or less. This makes it possible to obtain a silicon nitride powder having a low carbon content and a high alpha conversion rate. By using such a silicon nitride powder as a raw material for sintering, a sintered body having excellent mechanical properties can be obtained.
　上記窒化ケイ素粉末のフッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下であり、α化率が８０％以上であってよい。 The silicon nitride powder may have a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and an α conversion rate of 80% or more.
　本開示は、上述のいずれかの製造方法で製造される窒化ケイ素粉末を含む焼結原料を成形して焼成する焼結工程を有する、窒化ケイ素焼結体の製造方法を提供する。この製造方法によれば、優れた機械的特性を有する窒化ケイ素焼結体を低コストで製造することができる。 The present disclosure provides a method for producing a silicon nitride sintered body, which has a sintering step of molding and firing a sintering raw material containing the silicon nitride powder produced by any of the above production methods. According to this manufacturing method, a silicon nitride sintered body having excellent mechanical properties can be manufactured at low cost.
　本開示は、フッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下である、窒化ケイ素焼結体を提供する。この窒化ケイ素焼結体は、不純物が十分に低減されており、優れた機械的特性を有する。 The present disclosure provides a silicon nitride sintered body having a fluorine content of 600 mass ppm or less and a carbon content of 0.1 mass% or less. This silicon nitride sintered body has sufficiently reduced impurities and has excellent mechanical properties.
　不純物が十分に低減されており、優れた機械的特性を有する焼結体を製造することが可能な窒化ケイ素粉末及びその製造方法を提供することができる。また、不純物が十分に低減されており、優れた機械的特性を有する窒化ケイ素焼結体及びその製造方法を提供することができる。 It is possible to provide a silicon nitride powder and a method for producing the same, which have sufficiently reduced impurities and are capable of producing a sintered body having excellent mechanical properties. In addition, it is possible to provide a silicon nitride sintered body with sufficiently reduced impurities and excellent mechanical properties, and a method for producing the same.
　本開示の実施形態を以下に説明する。ただし、以下の実施形態は、本開示を説明するための例示であり、本開示を以下の内容に限定する趣旨ではない。 An embodiment of the present disclosure will be described below. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.
　一実施形態に係る窒化ケイ素粉末（Ｓｉ３Ｎ４粉末）のフッ素の含有量は６００質量ｐｐｍ以下であり、炭素の含有量は０．１質量ｐｐｍ以下である。このような窒化ケイ素粉末を焼結原料として得られる焼結体は、室温（２０℃）及び高温（１３００℃）において、十分に高い曲げ強度を有する。また、フッ素及び炭素の含有量が十分に低いため、焼結体用に限定されず、種々の用途に好適に用いることができる。 The silicon nitride powder (Si 3 N 4 powder) according to one embodiment has a fluorine content of 600 mass ppm or less and a carbon content of 0.1 mass ppm or less. A sintered body obtained by using such a silicon nitride powder as a sintering raw material has sufficiently high bending strength at room temperature (20° C.) and high temperature (1300° C.). Moreover, since the contents of fluorine and carbon are sufficiently low, it can be suitably used for various applications without being limited to sintered bodies.
　一層高い曲げ強度を有する焼結体を得る観点から、窒化ケイ素粉末のフッ素の含有量は、３００質量ｐｐｍ以下であってよく、１００質量ｐｐｍ以下であってよく、６０質量ｐｐｍ以下であってもよい。製造の容易性の観点から、フッ素の含有量は、５質量ｐｐｍ以上であってよく、１０質量ｐｐｍ以上であってよく、３０質量ｐｐｍ以上であってもよい。窒化ケイ素粉末のフッ素の含有量の一例は、５～６００質量ｐｐｍである。 From the viewpoint of obtaining a sintered body having a higher bending strength, the fluorine content of the silicon nitride powder may be 300 mass ppm or less, 100 mass ppm or less, or even 60 mass ppm or less. good. From the viewpoint of ease of production, the fluorine content may be 5 mass ppm or more, 10 mass ppm or more, or 30 mass ppm or more. An example of the fluorine content of silicon nitride powder is 5 to 600 mass ppm.
　窒化ケイ素粉末に含まれるフッ素は、原料として用いられる蛍石（ＣａＦ２）等のフッ化物、及び弗酸を用いる酸処理等に由来する。したがって、例えば、蛍石等のフッ化物の使用量を変更すること、又は、酸処理の条件を変更することによって、窒化ケイ素粉末のフッ素の含有量を調整することができる。窒化ケイ素粉末のフッ素の含有量は、窒化ケイ素粉末を燃焼して脱離するフッ素の量を、イオンクロマトグラフを用いて定量することによって求めることができる。 Fluorine contained in the silicon nitride powder is derived from fluoride such as fluorite (CaF 2 ) used as a raw material, acid treatment using hydrofluoric acid, and the like. Therefore, for example, the fluorine content of the silicon nitride powder can be adjusted by changing the amount of fluoride such as fluorite used or by changing the acid treatment conditions. The fluorine content of the silicon nitride powder can be obtained by quantifying the amount of fluorine desorbed by burning the silicon nitride powder using an ion chromatograph.
　窒化ケイ素粉末の炭素の含有量は０．１質量％以下である。このような窒化ケイ素粉末を焼結原料として得られる焼結体は、室温（２０℃）及び高温（１３００℃）において、十分に高い曲げ強度を有する。一層高い曲げ強度を有する焼結体を得る観点から、窒化ケイ素粉末の炭素の含有量は、０．０８質量％以下であってよく、０．０７質量％以下であってよく、０．０６質量％以下であってもよい。製造の容易性の観点から、窒化ケイ素粉末の炭素の含有量は、０．０１質量％以上であってよく、０．０２質量％以上であってもよい。窒化ケイ素粉末の炭素の含有量の一例は、０．０１～０．１質量％である。 The carbon content of the silicon nitride powder is 0.1% by mass or less. A sintered body obtained by using such a silicon nitride powder as a sintering raw material has sufficiently high bending strength at room temperature (20° C.) and high temperature (1300° C.). From the viewpoint of obtaining a sintered body having higher bending strength, the carbon content of the silicon nitride powder may be 0.08% by mass or less, may be 0.07% by mass or less, and may be 0.06% by mass. % or less. From the viewpoint of ease of manufacture, the carbon content of the silicon nitride powder may be 0.01% by mass or more, or may be 0.02% by mass or more. An example of the carbon content of silicon nitride powder is 0.01 to 0.1% by mass.
　窒化ケイ素粉末に含まれる炭素は、原料粉末を成形する際の有機バインダ及び容器の材質等に由来する。通常は、原料粉末をそのまま焼成しても、十分に窒化が進行しないため、成形体として焼成される場合がある。このとき、成形性を確保するため、ポリビニルアルコール等のバインダが用いられる。このようなバインダの使用量を変えることで、窒化ケイ素粉末の炭素の含有量を調整することができる。窒化ケイ素粉末の炭素の含有量は、ＪＩＳ　Ｒ　１６０３：２００７の「１１　炭素の定量方法」における「燃焼（高周波加熱）－赤外線吸収法」によって求めることができる。なお、本実施形態の窒化ケイ素粉末を製造する際には、有機バインダは用いなくてもよい。 The carbon contained in the silicon nitride powder is derived from the organic binder and the material of the container when molding the raw material powder. Normally, even if the raw material powder is fired as it is, the nitriding does not progress sufficiently, so it may be fired as a compact. At this time, a binder such as polyvinyl alcohol is used to ensure moldability. By changing the amount of the binder used, the carbon content of the silicon nitride powder can be adjusted. The carbon content of the silicon nitride powder can be determined by the "combustion (high-frequency heating) - infrared absorption method" in "11 carbon determination method" of JIS R 1603:2007. In addition, when manufacturing the silicon nitride powder of this embodiment, it is not necessary to use an organic binder.
　窒化ケイ素粉末の純度は、９９質量％以上であってよく、９９．５質量％以上であってもよく、９９．８質量％以上であってもよい。窒化ケイ素粉末のα化率（Ｓｉ３Ｎ４全体に対するα－Ｓｉ３Ｎ４の相比率）は８０％以上である。このような窒化ケイ素粉末を焼結原料として得られる焼結体は、優れた機械的特性を有する。破壊靭性を一層向上する観点から、窒化ケイ素粉末のα化率は、８５％以上であってよく、８８％以上であってよく、９０％以上であってもよい。窒化ケイ素粉末の製造コストを低減する観点から、窒化ケイ素粉末のα化率は、９８％以下であってよく、９７％以下であってよく、９６％以下であってもよい。窒化ケイ素粉末のα化率の一例は、８０～９８％である。 The purity of the silicon nitride powder may be 99% by mass or higher, 99.5% by mass or higher, or 99.8% by mass or higher. The α conversion rate of the silicon nitride powder (the phase ratio of α-Si 3 N 4 to the whole Si 3 N 4 ) is 80% or more. A sintered body obtained by using such a silicon nitride powder as a sintering raw material has excellent mechanical properties. From the viewpoint of further improving the fracture toughness, the alpha conversion rate of the silicon nitride powder may be 85% or more, 88% or more, or 90% or more. From the viewpoint of reducing the manufacturing cost of the silicon nitride powder, the α conversion rate of the silicon nitride powder may be 98% or less, 97% or less, or 96% or less. An example of the α conversion rate of silicon nitride powder is 80 to 98%.
　窒化ケイ素粉末のβ化率（Ｓｉ３Ｎ４全体に対するβ－Ｓｉ３Ｎ４の相比率）は、α化率を十分に高くする観点から、２０％以下であってよく、１５％以下であってよく、１２％以下であってよく、１０％以下であってもよい。窒化ケイ素粉末のβ化率は、製造の容易性の観点から、２％以上であってよく、４％以上であってもよい。 The β conversion rate of the silicon nitride powder (the phase ratio of β-Si 3 N 4 to the entire Si 3 N 4 ) may be 20% or less, preferably 15% or less, from the viewpoint of sufficiently increasing the alpha conversion rate. may be 12% or less, or may be 10% or less. The β conversion rate of the silicon nitride powder may be 2% or more, or may be 4% or more, from the viewpoint of ease of production.
　窒化ケイ素粉末のα化率は焼成条件に依存する。原料粉末の窒化反応が適度に進行すれば、高いα化率を有する窒化ケイ素粉末を得ることができる。一方、原料粉末の窒化反応が急激に進行したり、原料粉末同士の接触が十分ではなかったりすると、α化率が低くなる傾向にある。窒化ケイ素粉末のα化率は、Ｘ線回折の回折線強度によって求めることができる。 The alpha conversion rate of silicon nitride powder depends on the firing conditions. If the nitriding reaction of the raw material powder proceeds appropriately, it is possible to obtain a silicon nitride powder having a high degree of alpha conversion. On the other hand, if the nitriding reaction of the raw material powder progresses rapidly or the contact between the raw material powders is insufficient, the α conversion rate tends to decrease. The α conversion rate of the silicon nitride powder can be obtained from the diffraction line intensity of X-ray diffraction.
　一実施形態に係る窒化ケイ素粉末の製造方法は、ケイ素粉末を含み、ケイ素粉末１００質量部に対するフッ化物の含有量が１質量部以下である原料粉末を、かさ密度が０．７ｇ／ｃｍ３以上、且つ前記原料粉末の充填高さが１５～８０ｍｍになるように容器に充填する充填工程と、容器に充填された原料粉末を、窒素ガスを含む雰囲気中で焼成して、窒化ケイ素を含む焼成物を得る焼成工程と、焼成物を粉砕する粉砕工程と、を有する。 A method for producing a silicon nitride powder according to one embodiment includes a raw material powder containing silicon powder and having a fluoride content of 1 part by mass or less with respect to 100 parts by mass of the silicon powder, and having a bulk density of 0.7 g/cm 3 or more. , and a filling step of filling the container so that the filling height of the raw material powder is 15 to 80 mm, and firing the raw material powder filled in the container in an atmosphere containing nitrogen gas, and firing containing silicon nitride It has a sintering step of obtaining a product and a pulverizing step of pulverizing the sintered product.
　原料粉末は、ケイ素粉末の他に、窒化を促進するために、Ｌｉ、Ｎａ、Ｋ、Ｍｇ、Ｃａ、Ｓｒ又はＢａ元素を構成元素とするフッ化物を含んでもよい。ただし、窒化ケイ素粉末のフッ素の含有量を低減する観点から、ケイ素粉末１００質量部に対するフッ化物の含有量は、０．５質量部以下であってよく、０．３質量部以下であってもよい。窒化ケイ素粉末のフッ素の含有量を十分に低減する観点から、原料粉末はフッ化物を含んでいなくてもよい。必要に応じ、酸を用いてケイ素粉末の前処理を行い、ケイ素粉末の不純物を低減してもよい。 In addition to the silicon powder, the raw material powder may contain a fluoride containing Li, Na, K, Mg, Ca, Sr or Ba as a constituent element in order to promote nitridation. However, from the viewpoint of reducing the fluorine content of the silicon nitride powder, the content of fluoride with respect to 100 parts by mass of the silicon powder may be 0.5 parts by mass or less, or 0.3 parts by mass or less. good. From the viewpoint of sufficiently reducing the fluorine content of the silicon nitride powder, the raw material powder may not contain fluoride. If necessary, the silicon powder may be pretreated with an acid to reduce impurities in the silicon powder.
　本実施形態では、成形体を作製せずに粉末の状態で焼成工程を行うことが可能である。このように、成形体を作製しないため、有機バインダを用いずに窒化ケイ素粉末を製造することができる。したがって、炭素の含有量が十分に低い窒化ケイ素粉末を製造することができる。原料粉末の炭素の含有量は、０．１質量％以下であってよい。原料粉末における炭素の含有量は、ＪＩＳ　Ｒ　１６０３：２００７の「１１　炭素の定量方法」における「燃焼（高周波加熱）－赤外線吸収法」によって求めることができる。 In this embodiment, it is possible to carry out the firing process in a powder state without producing a compact. In this way, since no compact is produced, the silicon nitride powder can be produced without using an organic binder. Therefore, a silicon nitride powder with a sufficiently low carbon content can be produced. The carbon content of the raw material powder may be 0.1% by mass or less. The carbon content in the raw material powder can be determined by the "combustion (high-frequency heating) - infrared absorption method" in "11 carbon determination method" of JIS R 1603:2007.
　原料粉末を充填する容器は、不活性雰囲気下で１５００℃の温度まで変質しない材質のものを用いることができる。容器は例えばアルミナ製、窒化ホウ素製、及び、カーボン製のものを用いることができる。容器の構造は特に制限されず、例えば、原料粉末を収容する収容空間を形成できるものを用いることができる。ハンドリング性の観点から、凹部を有する容器本体と、この本体部の凹部を覆う蓋体とを備えるものであってよい。 The container filled with the raw material powder can be made of a material that does not change in quality up to a temperature of 1500°C under an inert atmosphere. For example, the container can be made of alumina, boron nitride, or carbon. The structure of the container is not particularly limited, and for example, a container capable of forming an accommodation space for accommodating the raw material powder can be used. From the viewpoint of ease of handling, the container body may include a container body having a recess and a lid covering the recess of the body.
　原料粉末のかさ密度が０．７ｇ／ｃｍ３以上になるように、容器に原料粉末を充填する。これによって、ケイ素粉末の窒化が適度に進行し、高いα化率を有する窒化ケイ素粉末を得ることができる。α化率を一層高くする観点から、容器における原料粉末のかさ密度は、０．８ｇ／ｃｍ３以上であってよく、０．９ｇ／ｃｍ３以上であってもよい。容器における原料粉末のかさ密度は、１．６ｇ／ｃｍ３以下であってよく、１．２ｇ／ｃｍ３以下であってよく、１．０ｇ／ｃｍ３以下であってもよい。かさ密度が大きくなると、発熱量が増加し、β－Ｓｉ３Ｎ４相の生成量が増加する傾向にある。また、容器への充填が困難になる場合がある。容器における原料粉末のかさ密度の一例は、０．７～１．６ｇ／ｃｍ３である。 A container is filled with the raw material powder so that the bulk density of the raw material powder is 0.7 g/cm 3 or more. As a result, the nitridation of the silicon powder proceeds appropriately, and a silicon nitride powder having a high alpha conversion rate can be obtained. From the viewpoint of further increasing the α conversion rate, the bulk density of the raw material powder in the container may be 0.8 g/cm 3 or more, or 0.9 g/cm 3 or more. The bulk density of the raw material powder in the container may be 1.6 g/cm 3 or less, 1.2 g/cm 3 or less, or 1.0 g/cm 3 or less. As the bulk density increases, the calorific value tends to increase and the amount of β-Si 3 N 4 phase produced tends to increase. In addition, it may become difficult to fill the container. An example of the bulk density of the raw material powder in the container is 0.7-1.6 g/cm 3 .
　容器内における、原料粉末の充填高さ（鉛直方向の厚み）は、１５～８０ｍｍであり、２０～６０ｍｍであってよい。このような充填高さにすることによって、窒化反応が円滑に進行する。原料粉末の充填高さは、容器の底面から鉛直方向に沿う高さとして測定することができる。 The filling height (thickness in the vertical direction) of the raw material powder in the container is 15 to 80 mm, and may be 20 to 60 mm. With such a filling height, the nitriding reaction proceeds smoothly. The filling height of the raw material powder can be measured as the height along the vertical direction from the bottom of the container.
　焼成工程では、容器に充填された原料粉末を、窒素ガスを含む雰囲気中で焼成し、原料粉末に含まれるケイ素粉末を窒化する。焼成時の雰囲気中における窒素ガスの濃度は、９０体積％以上であってよく、９５体積％以上であってよく、９７体積％以上であってもよい。 In the firing process, the raw material powder filled in the container is fired in an atmosphere containing nitrogen gas to nitride the silicon powder contained in the raw material powder. The concentration of nitrogen gas in the atmosphere during firing may be 90% by volume or more, 95% by volume or more, or 97% by volume or more.
　焼成時の雰囲気は、窒素ガスと窒素ガスとは異なる他のガスを含んでいてもよい。他のガスとしては、アルゴンガス及び水素ガスが挙げられる。アルゴンガスを加えることによって、窒化反応の反応速度を調整することができる。水素ガスを加えることによって、原料粉末に含まれるＳｉＯ２等の酸化物を還元し、高い純度を有する窒化ケイ素粉末を製造することができる。このような観点から、焼成時の雰囲気における水素ガスの含有量は、１体積％以上であってよく、２体積％以上であってもよい。一方、ケイ素粉末の窒化を促進する観点から、焼成時の雰囲気における水素ガスの含有量は５体積％以下であってよい。焼成時の雰囲気における水素ガスの含有量の一例は、１～５体積％である。本明細書におけるガスの含有量（体積％）は、標準状態（０℃、１ａｔｍ）における値である。 The atmosphere during firing may contain nitrogen gas and other gases different from nitrogen gas. Other gases include argon gas and hydrogen gas. By adding argon gas, the reaction rate of the nitriding reaction can be adjusted. By adding hydrogen gas, oxides such as SiO 2 contained in the raw material powder can be reduced, and silicon nitride powder having high purity can be produced. From this point of view, the content of hydrogen gas in the atmosphere during firing may be 1% by volume or more, or may be 2% by volume or more. On the other hand, from the viewpoint of promoting nitridation of the silicon powder, the content of hydrogen gas in the atmosphere during firing may be 5% by volume or less. An example of the content of hydrogen gas in the atmosphere during firing is 1 to 5% by volume. Gas content (% by volume) in this specification is a value under standard conditions (0° C., 1 atm).
　焼成工程は、焼成温度の範囲が互いに異なる複数の段階を含んでいてもよい。複数の段階は、以下の第１段階と第２段階を含んでいてもよい。例えば、第１段階では、１１００～１２００℃の温度範囲（１）まで昇温して保持する。この第１段階の保持温度が低過ぎると窒化反応が進行し難くなる傾向にある。一方、この第１段階の保持温度が高過ぎると、窒化反応が急激に進行して、β－Ｓｉ３Ｎ４（β相）の生成量が増加する。温度範囲（１）における保持時間は、２～１２時間であってよい。保持時間が短過ぎると窒化反応が十分に進行しない場合がある。保持時間が長過ぎると窒化ケイ素粉末の生産性が低下する。 The firing process may include multiple stages with different firing temperature ranges. The multiple stages may include the following first stage and second stage. For example, in the first stage, the temperature is raised to the temperature range (1) of 1100 to 1200° C. and maintained. If the holding temperature in the first stage is too low, the nitriding reaction tends to be difficult to proceed. On the other hand, if the holding temperature in the first stage is too high, the nitriding reaction proceeds rapidly, increasing the amount of β-Si 3 N 4 (β phase) produced. The holding time in temperature range (1) may be from 2 to 12 hours. If the holding time is too short, the nitriding reaction may not proceed sufficiently. If the holding time is too long, the productivity of the silicon nitride powder will decrease.
　第１段階の後に行う第２段階では、１４００～１５００℃の温度範囲（２）まで昇温して保持する。このような第２段階を行うことによって、未反応のＳｉを十分に低減することができる。この第２段階の保持温度が低過ぎると未反応のＳｉの残存量が増加する傾向にある。一方、この第２段階の保持温度が高過ぎると、生成した窒化ケイ素のα相からβ相への転移が生じる傾向にある。温度範囲（２）における保持時間は、１～８時間であってよい。保持時間が短過ぎると未反応のＳｉが残存する傾向にある。保持時間が長過ぎると窒化ケイ素粉末の生産性が低下する。 In the second stage after the first stage, the temperature is raised to the temperature range (2) of 1400-1500°C and maintained. By performing such a second step, unreacted Si can be sufficiently reduced. If the holding temperature in this second stage is too low, the residual amount of unreacted Si tends to increase. On the other hand, if the holding temperature in this second stage is too high, the resulting silicon nitride tends to undergo a transition from the α-phase to the β-phase. The holding time in temperature range (2) may be from 1 to 8 hours. If the holding time is too short, unreacted Si tends to remain. If the holding time is too long, the productivity of the silicon nitride powder will decrease.
　温度範囲（１）以上の温度における合計の保持時間は、２４～１６０時間であってよい。これによって、適度な速度でケイ素粉末の窒化反応が進行し、不純物が少なく高いα化率を有する窒化ケイ素粉末を高い生産性で製造することができる。第１段階から第２段階への移行は、所定範囲内の昇温速度で昇温してもよいし、温度範囲（１）と温度範囲（２）の間の温度で、所定時間保持してもよい。 The total holding time at temperatures in the temperature range (1) or higher may be 24 to 160 hours. As a result, the nitriding reaction of the silicon powder proceeds at an appropriate rate, and a silicon nitride powder containing few impurities and having a high alpha conversion rate can be produced with high productivity. In the transition from the first stage to the second stage, the temperature may be increased at a temperature increase rate within a predetermined range, or a temperature between the temperature range (1) and the temperature range (2) may be maintained for a predetermined time. good too.
　粉砕工程では、焼成工程で得られる焼成物を粉砕する粉砕工程を行う。粉砕は、粗粉砕と微粉砕の複数段階に分けて行ってもよい。粉砕は、例えばボールミルを用いて湿式で行ってもよい。焼成物は、比表面積が８．０～１５．０ｍ２／ｇになるまで粉砕してもよい。 In the pulverizing step, a pulverizing step of pulverizing the fired product obtained in the firing step is performed. Pulverization may be performed in multiple steps of coarse pulverization and fine pulverization. Grinding may be performed wet, for example using a ball mill. The fired product may be pulverized until the specific surface area reaches 8.0 to 15.0 m 2 /g.
　このような製造方法によって、フッ素の含有量及び炭素の含有量が低く、高いα化率を有する窒化ケイ素粉末を得ることができる。例えば、フッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下であり、α化率が８０％以上である、窒化ケイ素粉末が得られる。このような窒化ケイ素粉末は、不純物濃度が低いことから、種々の用途に好適に用いることができる。例えば、焼結原料として用いることによって、優れた機械的特性を有する焼結体を得ることができる。α化率は、８５％以上であってよく、８８％以上であってよく、９０％以上であってよい。また、α化率は、９８％以下であってよく、９７％以下であってよく、９６％以下であってよい。α化率の範囲の一例は、８０～９８％である。 By such a production method, it is possible to obtain a silicon nitride powder having a low fluorine content and a low carbon content and a high alpha conversion rate. For example, a silicon nitride powder having a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass % or less, and a α conversion rate of 80% or more can be obtained. Since such silicon nitride powder has a low impurity concentration, it can be suitably used for various purposes. For example, by using it as a raw material for sintering, a sintered body having excellent mechanical properties can be obtained. The α conversion rate may be 85% or more, 88% or more, or 90% or more. In addition, the α conversion rate may be 98% or less, 97% or less, or 96% or less. An example of the α conversion rate range is 80 to 98%.
　粉砕工程の前又は後に、必要に応じて、処理工程を行ってもよい。例えば、粉砕した焼成物と弗化水素濃度が１０～４０質量％である弗酸とを配合し、不純物を低減してもよい。例えば、弗酸中に粉砕した焼成物を分散させて処理してもよい。弗酸における弗化水素濃度は１５～３０質量％であってよい。処理工程における弗酸の温度は、例えば４０～８０℃である。また、窒化ケイ素粉末を弗酸に浸漬する時間は、例えば１～１０時間である。 Before or after the pulverization process, a treatment process may be performed as necessary. For example, the pulverized fired product and hydrofluoric acid having a hydrogen fluoride concentration of 10 to 40% by mass may be blended to reduce impurities. For example, the pulverized fired product may be dispersed in hydrofluoric acid for treatment. The concentration of hydrogen fluoride in hydrofluoric acid may be 15-30% by mass. The temperature of hydrofluoric acid in the treatment step is, for example, 40-80.degree. The time for immersing the silicon nitride powder in hydrofluoric acid is, for example, 1 to 10 hours.
　一実施形態に係る窒化ケイ素焼結体の製造方法は、上述の窒化ケイ素粉末を主成分として含む焼結原料を成形して焼成する焼結工程を有する。焼結原料は、窒化ケイ素粉末の他に、酸化物系焼結助剤を含んでいてもよい。酸化物系焼結助剤としてはＹ２Ｏ３、ＭｇＯ及びＡｌ２Ｏ３等が挙げられる。焼結原料における酸化物系焼結助剤の含有量は、例えば３～１０質量％であってよい。 A method for manufacturing a silicon nitride sintered body according to one embodiment includes a sintering step of molding and firing a sintering raw material containing the above silicon nitride powder as a main component. The raw material for sintering may contain an oxide-based sintering aid in addition to the silicon nitride powder. Y 2 O 3 , MgO, Al 2 O 3 and the like are examples of oxide-based sintering aids. The content of the oxide-based sintering aid in the raw material for sintering may be, for example, 3 to 10% by mass.
　上記焼結工程では、上述の焼結原料を例えば３．０～３０ＭＰａの成形圧力で加圧して成形体を得る。成形体は一軸加圧して作製してもよいし、ＣＩＰによって作製してもよい。また、ホットプレスによって成形しながら焼成してもよい。成形体の焼成は、窒素ガス又はアルゴンガス等の不活性ガス雰囲気中で行ってよい。焼成時の圧力は、０．７～１ＭＰａであってよい。焼成温度は１８６０～２１００℃であってよく、１８８０～２０００℃であってもよい。当該焼成温度における焼成時間は６～２０時間であってよく、８～１６時間であってよい。焼成温度までの昇温速度は、例えば１．０～１０．０℃／時間であってよい。 In the sintering step, the sintering raw material is pressed with a molding pressure of, for example, 3.0 to 30 MPa to obtain a compact. The compact may be produced by uniaxial pressing or may be produced by CIP. Moreover, you may bake while shape|molding by a hot press. Firing of the compact may be performed in an inert gas atmosphere such as nitrogen gas or argon gas. The pressure during firing may be 0.7 to 1 MPa. The firing temperature may be 1860-2100°C, or 1880-2000°C. The firing time at the firing temperature may be 6 to 20 hours, or 8 to 16 hours. The heating rate to the firing temperature may be, for example, 1.0 to 10.0° C./hour.
　このようにして製造される窒化ケイ素焼結体は、製造コストが低く、且つ、優れた機械的特性を有する。また、不純物が低減されていることから、種々の用途に用いることができる。 The silicon nitride sintered body produced in this way has a low production cost and excellent mechanical properties. In addition, since impurities are reduced, it can be used for various purposes.
　一実施形態に係る窒化ケイ素焼結体は、フッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下であり、α化率が８０％以上である。 The silicon nitride sintered body according to one embodiment has a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and a alpha conversion rate of 80% or more.
　窒化ケイ素焼結体の曲げ強度を一層高くする観点から、窒化ケイ素焼結体のフッ素の含有量は、３００質量ｐｐｍ以下であってよく、１００質量ｐｐｍ以下であってよく、６０質量ｐｐｍ以下であってもよい。製造の容易性の観点から、窒化ケイ素焼結体のフッ素の含有量は、５質量ｐｐｍ以上であってよく、１０質量ｐｐｍ以上であってよく、３０質量ｐｐｍ以上であってもよい。窒化ケイ素焼結体のフッ素の含有量の一例は、５～６００質量ｐｐｍである。このような窒化ケイ素焼結体は、フッ素の含有量が上述の範囲内にある焼結原料を用いて製造することができる。 From the viewpoint of further increasing the bending strength of the silicon nitride sintered body, the fluorine content of the silicon nitride sintered body may be 300 mass ppm or less, 100 mass ppm or less, or 60 mass ppm or less. There may be. From the viewpoint of ease of manufacture, the fluorine content of the silicon nitride sintered body may be 5 mass ppm or more, 10 mass ppm or more, or 30 mass ppm or more. An example of the fluorine content of the silicon nitride sintered body is 5 to 600 mass ppm. Such a silicon nitride sintered body can be produced using a sintering raw material having a fluorine content within the above range.
　窒化ケイ素焼結体の炭素の含有量は０．１質量％以下である。このような窒化ケイ素焼結体は、室温（２０℃）及び高温（１３００℃）において、十分に高い曲げ強度を有する。一層高い曲げ強度を有する窒化ケイ素焼結体を得る観点から、窒化ケイ素焼結体の炭素の含有量は、０．０８質量％以下であってよく、０．０７質量％以下であってよく、０．０６質量％以下であってもよい。製造の容易性の観点から、窒化ケイ素焼結体の炭素の含有量は、０．０１質量％以上であってよく、０．０２質量％以上であってもよい。このような窒化ケイ素焼結体は、炭素の含有量が上述の範囲内にある焼結原料を用いて製造することができる。 The carbon content of the silicon nitride sintered body is 0.1% by mass or less. Such a silicon nitride sintered body has sufficiently high bending strength at room temperature (20° C.) and high temperature (1300° C.). From the viewpoint of obtaining a silicon nitride sintered body having higher bending strength, the carbon content of the silicon nitride sintered body may be 0.08% by mass or less, or 0.07% by mass or less, It may be 0.06% by mass or less. From the viewpoint of ease of manufacture, the carbon content of the silicon nitride sintered body may be 0.01% by mass or more, or may be 0.02% by mass or more. Such a silicon nitride sintered body can be produced using a sintering raw material having a carbon content within the above range.
　窒化ケイ素焼結体のフッ素及び炭素の含有量は、窒化ケイ素焼結体を粉末状に粉砕して得られた試料を用いて、窒化ケイ素粉末と同様にして測定することができる。 The fluorine and carbon contents of the silicon nitride sintered body can be measured in the same manner as the silicon nitride powder using a sample obtained by pulverizing the silicon nitride sintered body into powder.
　以上、幾つかの実施形態について説明したが、本開示は上記実施形態に何ら限定されるものではない。例えば、窒化ケイ素粉末は、窒化ケイ素と他の物質との複合焼結体の焼結原料として用いてもよい。また、焼結原料以外の用途に用いてもよい。 Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. For example, silicon nitride powder may be used as a raw material for sintering composite sintered bodies of silicon nitride and other substances. Moreover, you may use for uses other than a sintering raw material.
　実施例及び比較例を参照して本開示の内容をより詳細に説明するが、本開示は下記の実施例に限定されるものではない。 The contents of the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.
（実施例１）
＜窒化ケイ素粉末の調製＞
　ケイ素粉末１００質量部に対して蛍石を１質量部配合して原料粉末を調製した。すなわち、原料粉末は、ケイ素粉末１００質量部に対して、フッ化物（蛍石）を１質量部含有していた。原料粉末における炭素の含有量は０．１質量％以下であった。凹部を有する本体と蓋体とを有するアルミナ製の容器を準備した。凹部に原料粉末を充填した。充填後の原料粉末のかさ密度は、１ｇ／ｃｍ３であった。原料粉末の充填形状は直方体形状であり、充填高さは４５ｍｍであった。本体の凹部を蓋体で覆い、原料粉末をアルミナ製の容器内に収容した。容器内に収容された原料粉末を以下の手順で焼成した。 (Example 1)
<Preparation of Silicon Nitride Powder>
A raw material powder was prepared by blending 1 part by mass of fluorite with 100 parts by mass of silicon powder. That is, the raw material powder contained 1 part by mass of fluoride (fluorite) with respect to 100 parts by mass of silicon powder. The carbon content in the raw material powder was 0.1% by mass or less. An alumina container having a main body with a recess and a lid was prepared. The recess was filled with raw material powder. The bulk density of the raw material powder after filling was 1 g/cm 3 . The filling shape of the raw material powder was a rectangular parallelepiped, and the filling height was 45 mm. The concave portion of the main body was covered with a lid, and the raw material powder was placed in an alumina container. The raw material powder accommodated in the container was sintered in the following procedure.
　原料粉末を収容した容器を電気炉に入れて、以下の温度条件で焼成した。５℃／分の昇温速度で２０℃から１１５０℃まで昇温した。１１５０℃の温度で８時間保持した後、０．１５℃／分の昇温速度で１４５０℃まで昇温した。１４５０℃の温度で４時間保持した後、室温まで自然放冷した。電気炉中の雰囲気は、窒素ガスとした。１１５０℃で保持を開始してから、１４５０℃の保持が終了するまでの時間は、表１に示すとおり、４５時間であった。 The container containing the raw material powder was placed in an electric furnace and fired under the following temperature conditions. The temperature was raised from 20°C to 1150°C at a temperature elevation rate of 5°C/min. After holding the temperature at 1150° C. for 8 hours, the temperature was raised to 1450° C. at a rate of temperature rise of 0.15° C./min. After being held at a temperature of 1450° C. for 4 hours, it was naturally cooled to room temperature. The atmosphere in the electric furnace was nitrogen gas. As shown in Table 1, the time from the start of holding at 1150° C. to the end of holding at 1450° C. was 45 hours.
　得られたインゴットを粗粉砕した後、ボールミルで湿式粉砕した。その後、窒素雰囲気下で乾燥した。このようにして、実施例１の窒化ケイ素粉末を調製した。 The obtained ingot was coarsely pulverized and then wet-pulverized with a ball mill. After that, it was dried under a nitrogen atmosphere. Thus, the silicon nitride powder of Example 1 was prepared.
＜窒化ケイ素粉末の評価＞
　窒化ケイ素粉末のフッ素の含有量を、以下の要領で測定した。自動試料燃焼装置（三菱化学株式会社製、装置名：ＡＱＦ－２１００Ｈ型）を用いて窒化ケイ素粉末を加熱し、発生したガスを水に溶解させた。イオンクロマトグラフ（サーモフィッシャーサイエンティフィック社製、装置名：ＩＣＳ－２１００）を用いて、水中に溶解したフッ素を測定した。この測定値に基づいて、窒化ケイ素粉末のフッ素の含有量を算出した。 <Evaluation of Silicon Nitride Powder>
The fluorine content of the silicon nitride powder was measured in the following manner. The silicon nitride powder was heated using an automatic sample combustion apparatus (manufactured by Mitsubishi Chemical Corporation, device name: AQF-2100H type), and the generated gas was dissolved in water. Fluorine dissolved in water was measured using an ion chromatograph (manufactured by Thermo Fisher Scientific, device name: ICS-2100). Based on this measured value, the fluorine content of the silicon nitride powder was calculated.
　窒化ケイ素粉末の炭素の含有量は、ＪＩＳ　Ｒ　１６０３：２００７の「１１　炭素の定量方法」における「燃焼（高周波加熱）－赤外線吸収法」によって測定した。測定には、ＬＥＣＯ社製のＣＳ－４４４ＬＳ（商品名）を用いた。高周波加熱によって、助燃材とともに試料（窒化ケイ素粉末）を燃焼させた。発生した二酸化炭素を赤外線吸収法により定量することによって、試料中の炭素含有量を測定した。 The carbon content of the silicon nitride powder was measured by the "combustion (high-frequency heating) - infrared absorption method" in "11 carbon determination method" of JIS R 1603:2007. CS-444LS (trade name) manufactured by LECO was used for the measurement. The sample (silicon nitride powder) was combusted together with the combustion aid by high-frequency heating. The carbon content in the sample was measured by quantifying the generated carbon dioxide by an infrared absorption method.
　窒化ケイ素粉末のα化率は、以下の要領で測定した。Ｘ線回折装置（リガク製、装置名：Ｕｌｔｉｍａ　ＩＶ）を用い、ＣｕＫα線で窒化ケイ素粉末のＸ線回折を行った。α相は、（１０２）面の回折線強度Ｉａ１０２と、（２１０）面の回折線強度Ｉａ２１０で代表した。β相は、（１０１）面の回折線強度Ｉｂ１０１と、（２１０）面の回折線強度Ｉｂ２１０で代表した。これらの回折線強度を用いて、以下の式によってα化率を算出した。結果は表１に示すとおりであった。
　　α化率（質量％）=
　　　（Ｉａ１０２＋Ｉａ２１０）／（Ｉａ１０２＋Ｉａ２１０＋Ｉｂ１０１＋Ｉｂ２１０）×１００ The alpha conversion rate of the silicon nitride powder was measured in the following manner. Using an X-ray diffractometer (manufactured by Rigaku, device name: Ultima IV), X-ray diffraction of the silicon nitride powder was performed with CuKα rays. The α phase was represented by the diffraction line intensity Ia102 of the (102) plane and the diffraction line intensity Ia210 of the (210) plane. The β phase was represented by the diffraction line intensity Ib101 of the (101) plane and the diffraction line intensity Ib210 of the (210) plane. Using these diffraction line intensities, the α conversion rate was calculated according to the following formula. The results were as shown in Table 1.
α conversion rate (% by mass) =
(I a102 +I a210 )/(I a102 +I a210 +I b101 +I b210 )×100
＜窒化ケイ素焼結体の作製＞
　調製した窒化ケイ素粉末９０質量部、平均粒径１．５μｍのＹ２Ｏ３粉末５質量部、及び、平均粒径１．２μｍのＹｂ２Ｏ３粉末５質量部を配合し、メタノール中で４時間湿式混合した。その後、乾燥して得た混合粉末を１０ＭＰａの圧力で金型成形し、その後更に２５ＭＰａの圧力でＣＩＰ成形した。得られた成形体を、窒化ケイ素粉末及びＢＮ粉末の混合粉末からなる詰め粉とともにカーボン製坩堝にセットし、１ＭＰａの窒素加圧雰囲気下、温度１９００℃で１２時間焼成して窒化ケイ素焼結体を製造した。 <Preparation of Silicon Nitride Sintered Body>
90 parts by mass of the prepared silicon nitride powder, 5 parts by mass of Y 2 O 3 powder with an average particle size of 1.5 μm, and 5 parts by mass of Yb 2 O 3 powder with an average particle size of 1.2 μm were blended and dissolved in methanol. Wet mixed for hours. After that, the mixed powder obtained by drying was mold-molded at a pressure of 10 MPa, and then CIP-molded at a pressure of 25 MPa. The resulting molded body is set in a carbon crucible together with a powder mixture of silicon nitride powder and BN powder, and fired at a temperature of 1900° C. for 12 hours in a nitrogen pressurized atmosphere of 1 MPa to obtain a silicon nitride sintered body. manufactured.
＜窒化ケイ素焼結体の評価＞
　抗折強度は、３点曲げ抗折強度であり、ＪＩＳ　Ｒ　１６０１：２００８に準拠して市販の抗折強度計（島津製作所製、装置名：ＡＧ－２０００）を用いて測定した。測定は、室温（２０℃）及び１３００℃のそれぞれにおいて測定した。その結果（相対値）は表１に示すとおりであった。破壊靭性（ＫＩＣ）は、ＳＥＰＢ法によって測定される値であり、ＪＩＳ　Ｒ１６０７：２０１５に準拠し、市販の測定装置（インストロン製、装置名：万能試験機５５８２型）を用いて測定した。その結果（相対値）は表１に示すとおりであった。 <Evaluation of Silicon Nitride Sintered Body>
The bending strength is a three-point bending bending strength, and was measured using a commercially available bending strength meter (manufactured by Shimadzu Corporation, device name: AG-2000) in accordance with JIS R 1601:2008. Measurements were taken at room temperature (20°C) and 1300°C. The results (relative values) were as shown in Table 1. The fracture toughness (K IC ) is a value measured by the SEPB method, and was measured using a commercially available measuring device (manufactured by Instron, device name: universal testing machine 5582) in accordance with JIS R1607:2015. The results (relative values) were as shown in Table 1.
（実施例２）
　原料粉末の調製の際にフッ化物（蛍石）を配合しなかったこと、焼成の際の雰囲気を窒素ガスと水素ガスの混合ガスとしたこと、及び、容器への原料粉末の充填高さを表１のとおりに変更したこと以外は、実施例１と同様にして窒化ケイ素粉末を調製した。混合ガスにおける水素ガスの濃度は、表１に示すとおり３体積％であり、残部は窒素ガスとした。このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表１に示すとおりであった。 (Example 2)
Fluoride (fluorite) was not mixed in the preparation of the raw material powder, the atmosphere during firing was a mixed gas of nitrogen gas and hydrogen gas, and the filling height of the raw material powder in the container was adjusted. A silicon nitride powder was prepared in the same manner as in Example 1, except for the changes shown in Table 1. The concentration of hydrogen gas in the mixed gas was 3% by volume as shown in Table 1, and the balance was nitrogen gas. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 1.
　このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体を作製し評価を行った。結果は表１に示すとおりであった。 Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 1.
（実施例３）
　原料粉末の調製の際にフッ化物（蛍石）を配合しなかったこと、及び、焼成の際の雰囲気を実施例２と同じ窒素ガスと水素ガスの混合ガスとしたこと以外は、実施例１と同様にして窒化ケイ素粉末を調製した。このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表１に示すとおりであった。このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体を作製し評価を行った。結果は表１に示すとおりであった。 (Example 3)
Example 1 except that fluoride (fluorite) was not blended during the preparation of the raw material powder, and the atmosphere during firing was the same mixed gas of nitrogen gas and hydrogen gas as in Example 2. A silicon nitride powder was prepared in the same manner. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 1. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 1.
（実施例４）
　原料粉末の調製の際、ケイ素粉末１００質量部に対するフッ化物（蛍石）の配合量を０．２質量部としたこと以外は、実施例３と同様にして窒化ケイ素粉末を調製した。このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表１に示すとおりであった。このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体を作製し評価を行った。結果は表１に示すとおりであった。 (Example 4)
A silicon nitride powder was prepared in the same manner as in Example 3, except that the amount of fluoride (fluorite) added to 100 parts by mass of the silicon powder was 0.2 parts by mass during the preparation of the raw material powder. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 1. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 1.
（実施例５）
　原料粉末を焼成する温度条件を次のとおりとした。５℃／分の昇温速度で１１５０℃まで昇温した。１１５０℃の温度で１２時間保持した後、０．０１８℃／分の昇温速度で１４５０℃まで昇温した。１４５０℃の温度で４時間保持した後、室温まで自然放冷した。焼成時の温度条件を上述のとおりにしたこと以外は、実施例１と同様にして窒化ケイ素粉末を調製した。このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表１に示すとおりであった。このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体の作製及び評価を行った。結果は表１に示すとおりであった。 (Example 5)
The temperature conditions for firing the raw material powder were as follows. The temperature was raised to 1150°C at a temperature elevation rate of 5°C/min. After holding the temperature at 1150° C. for 12 hours, the temperature was raised to 1450° C. at a rate of 0.018° C./min. After being held at a temperature of 1450° C. for 4 hours, it was naturally cooled to room temperature. A silicon nitride powder was prepared in the same manner as in Example 1, except that the temperature conditions during firing were set as described above. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 1. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 1.
（比較例１）
　原料粉末の調製の際、ケイ素粉末１００質量部に対するフッ化物（蛍石）の配合量を２質量部としたこと以外は、実施例１と同様にして窒化ケイ素粉末を調製した。このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表２に示すとおりであった。このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体を作製し評価を行った。結果は表２に示すとおりであった。 (Comparative example 1)
A silicon nitride powder was prepared in the same manner as in Example 1, except that the amount of fluoride (fluorite) mixed with 100 parts by mass of the silicon powder was 2 parts by mass during the preparation of the raw material powder. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
（比較例２）
　ケイ素粉末１００質量部に対するフッ化物（蛍石）の配合量を０．２質量部としたこと以外は、実施例１と同様にして原料粉末を調製した。この原料粉末１００質量部に対し、ポリビニルアルコールを５質量部配合して混錬物を得た。この混錬物を、高温プレス機を用いて成形し、成形体を得た。容器の代わりに成形体を用いたこと、及び、１１５０℃から１４５０℃に昇温する時の昇温速度を０．０３５℃／ｍｉｎに変更したこと以外は、実施例２と同様にして焼成を行って窒化ケイ素粉末を調製した。このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表２に示すとおりであった。このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体の作製及び評価を行った。結果は表２に示すとおりであった。 (Comparative example 2)
A raw material powder was prepared in the same manner as in Example 1, except that the amount of fluoride (fluorite) mixed with 100 parts by mass of the silicon powder was 0.2 parts by mass. 5 parts by mass of polyvinyl alcohol was blended with 100 parts by mass of this raw material powder to obtain a kneaded material. This kneaded material was molded using a high-temperature press to obtain a molded body. Firing was carried out in the same manner as in Example 2, except that a compact was used instead of the container, and that the rate of temperature increase from 1150°C to 1450°C was changed to 0.035°C/min. to prepare silicon nitride powder. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
（比較例３）
　ケイ素粉末１００質量部に対するフッ化物（蛍石）の配合量を１質量部としたこと以外は、実施例１と同様にして原料粉末を調製した。この原料粉末１００質量部に対し、ポリビニルアルコールを５質量部配合して混錬物を得た。この混錬物を、高温プレス機を用いて成形し、成形体を得た。この成形体を用いたこと、及び、焼成時の雰囲気を窒素ガスのみにしたこと以外は比較例２と同様にして窒化ケイ素粉末を調製した。 (Comparative Example 3)
A raw material powder was prepared in the same manner as in Example 1, except that the amount of fluoride (fluorite) mixed with 100 parts by mass of silicon powder was 1 part by mass. 5 parts by mass of polyvinyl alcohol was blended with 100 parts by mass of this raw material powder to obtain a kneaded material. This kneaded material was molded using a high-temperature press to obtain a molded body. Silicon nitride powder was prepared in the same manner as in Comparative Example 2, except that this compact was used and the atmosphere during firing was changed to nitrogen gas only.
　このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表２に示すとおりであった。このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体の作製及び評価を行った。結果は表２に示すとおりであった。 The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
（比較例４）
　容器への原料粉末の充填高さ及び充填密度を表２のとおりに変更したこと以外は、実施例１と同様にして窒化ケイ素粉末を調製した。このようにして調製した窒化ケイ素粉末の評価を実施例１と同様にして行った。結果は表２に示すとおりであった。このようにして調製した窒化ケイ素粉末を用いて、実施例１と同様にして窒化ケイ素焼結体を作製し評価を行った。結果は表２に示すとおりであった。 (Comparative Example 4)
Silicon nitride powder was prepared in the same manner as in Example 1, except that the filling height and filling density of the raw material powder in the container were changed as shown in Table 2. The silicon nitride powder thus prepared was evaluated in the same manner as in Example 1. The results were as shown in Table 2. Using the silicon nitride powder thus prepared, a silicon nitride sintered body was produced and evaluated in the same manner as in Example 1. The results were as shown in Table 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表１及び表２における曲げ強度及び破壊靭性は、比較例３を基準とする相対値である。実施例１～５の窒化ケイ素焼結体は、比較例１～４の窒化ケイ素焼結体よりも優れた機械的特性を有することが確認された。なお、各実施例の窒化ケイ素粉末に含まれる炭素は、原料及び製造設備から不可避的に混入したものであると考えられる。 The bending strength and fracture toughness in Tables 1 and 2 are relative values based on Comparative Example 3. It was confirmed that the silicon nitride sintered bodies of Examples 1-5 had better mechanical properties than the silicon nitride sintered bodies of Comparative Examples 1-4. It is considered that the carbon contained in the silicon nitride powder of each example was unavoidably mixed from raw materials and manufacturing equipment.
　不純物が十分に低減されており、優れた機械的特性を有する焼結体を製造することが可能な窒化ケイ素粉末及びその製造方法を提供することができる。優れた機械的特性を有する窒化ケイ素焼結体を製造することが可能な窒化ケイ素焼結体の製造方法を提供することができる。 It is possible to provide a silicon nitride powder and a method for producing the same, which have sufficiently reduced impurities and are capable of producing a sintered body having excellent mechanical properties. It is possible to provide a method for producing a silicon nitride sintered body that can produce a silicon nitride sintered body having excellent mechanical properties.

Claims (9)

  1. 　フッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下であり、α化率が８０％以上である、窒化ケイ素粉末。 A silicon nitride powder having a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and a α conversion rate of 80% or more.
  2. 　α化率が９０％以上である、請求項１に記載の窒化ケイ素粉末。 The silicon nitride powder according to claim 1, wherein the α conversion rate is 90% or more.
  3. 　α化率が９８％以下である、請求項１又は２に記載の窒化ケイ素粉末。 The silicon nitride powder according to claim 1 or 2, wherein the alpha conversion rate is 98% or less.
  4. 　ケイ素粉末を含み、ケイ素粉末１００質量部に対するフッ化物の含有量が１質量部以下である原料粉末を、かさ密度が０．７ｇ／ｃｍ３以上、且つ前記原料粉末の充填高さが１５～８０ｍｍになるように容器に充填する充填工程と、
    　前記容器に充填された前記原料粉末を、窒素ガスを含む雰囲気中で焼成して、窒化ケイ素を含む焼成物を得る焼成工程と、
    　前記焼成物を粉砕する粉砕工程と、を有する、窒化ケイ素粉末の製造方法。     A raw material powder containing a silicon powder and having a fluoride content of 1 part by mass or less with respect to 100 parts by mass of the silicon powder has a bulk density of 0.7 g/cm 3 or more and a filling height of the raw material powder of 15 to 80 mm. A filling step of filling the container so that
    a firing step of firing the raw material powder filled in the container in an atmosphere containing nitrogen gas to obtain a fired product containing silicon nitride;
    and a pulverizing step of pulverizing the fired product.
  5. 　前記焼成工程を前記窒素ガスと水素ガスとを含む雰囲気中で行う、請求項４に記載の窒化ケイ素粉末の製造方法。 The method for producing silicon nitride powder according to claim 4, wherein the firing step is performed in an atmosphere containing the nitrogen gas and the hydrogen gas.
  6. 　前記原料粉末における炭素の含有量が０．１質量％以下である、請求項４又は５に記載の窒化ケイ素粉末の製造方法。 The method for producing silicon nitride powder according to claim 4 or 5, wherein the carbon content in the raw material powder is 0.1% by mass or less.
  7. 　前記窒化ケイ素粉末のフッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下であり、α化率が８０％以上である、請求項４～６のいずれか一項に記載の窒化ケイ素粉末の製造方法。 7. The silicon nitride powder according to any one of claims 4 to 6, wherein the silicon nitride powder has a fluorine content of 600 mass ppm or less, a carbon content of 0.1 mass% or less, and an α conversion rate of 80% or more. A method for producing the silicon nitride powder according to the item.
  8. 　請求項４～７のいずれか一項に記載の製造方法で製造される窒化ケイ素粉末を含む焼結原料を成形して焼成する焼結工程を有する、窒化ケイ素焼結体の製造方法。 A method for producing a silicon nitride sintered body, comprising a sintering step of molding and firing a sintering raw material containing the silicon nitride powder produced by the production method according to any one of claims 4 to 7.
  9. 　フッ素の含有量が６００質量ｐｐｍ以下、且つ、炭素の含有量が０．１質量％以下である、窒化ケイ素焼結体。 A silicon nitride sintered body having a fluorine content of 600 mass ppm or less and a carbon content of 0.1 mass% or less.
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