JP2000178013A - Silicon nitride powder and its production - Google Patents
Silicon nitride powder and its productionInfo
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- JP2000178013A JP2000178013A JP10353684A JP35368498A JP2000178013A JP 2000178013 A JP2000178013 A JP 2000178013A JP 10353684 A JP10353684 A JP 10353684A JP 35368498 A JP35368498 A JP 35368498A JP 2000178013 A JP2000178013 A JP 2000178013A
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- nitride powder
- silicon
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、異方性の少ない高熱伝
導率の焼結体を得ることができる窒化ケイ素粉末及びそ
の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride powder capable of obtaining a sintered body having low anisotropy and high thermal conductivity, and a method for producing the same.
【０００２】[0002]
【従来の技術】高熱伝導性の窒化ケイ素焼結体を得るた
めの方法として、特開平９−３０８６６号、特開平９−
１８３６６６号、特開平９−２６８０６９号が開示され
ている。これらはいずれも特定の焼結助剤を用い、陽イ
オン不純物を制御し、粒界組成を制御することで、高熱
伝導を達成している。2. Description of the Related Art As a method for obtaining a silicon nitride sintered body having high thermal conductivity, Japanese Patent Application Laid-Open Nos.
183666 and JP-A-9-268069 are disclosed. All of these achieve high heat conduction by using a specific sintering aid, controlling cation impurities, and controlling the grain boundary composition.
【０００３】[0003]
【発明が解決しようとする課題】しかし、上記のような
方法では焼結体が高熱伝導で、熱伝導性に異方性の少な
い焼結体を得ることは困難であった。特に押出成形、テ
ープ成形、スリップキャスト成形法のように配向し易い
成形方法を用いた場合特に異方性が生じやすかった。熱
伝導率の異方性の少ない焼結体を得るため窒化ケイ素粉
末を得ることも困難であった。However, it has been difficult to obtain a sintered body having high thermal conductivity and low anisotropy in thermal conductivity by the above-mentioned method. In particular, when a molding method that is easily oriented such as extrusion molding, tape molding, or slip cast molding is used, anisotropy is particularly likely to occur. It was also difficult to obtain a silicon nitride powder in order to obtain a sintered body having low anisotropy in thermal conductivity.
【０００４】[0004]
【課題を解決するための手段】本発明者は、焼結時に１
方向に偏った粒成長を生じると得られた焼結体の熱伝導
性に偏りが生じるため、成形時に窒化ケイ素粒子が１方
向に偏った配向をしないこと、つまり窒化ケイ素粒子の
円形度が高いことが重要であることを見いだし、さらに
β化率が高くかつ円形度が高い窒化ケイ素粉末安定して
製造する方法を見いだし本発明を完成するに至った。Means for Solving the Problems The inventor of the present invention has proposed a method for sintering.
If the grain growth occurs in one direction, the thermal conductivity of the obtained sintered body becomes uneven, so that the silicon nitride particles do not have one-directional orientation during molding, that is, the circularity of the silicon nitride particles is high. It has been found that it is important, and furthermore, a method for stably producing silicon nitride powder having a high β conversion and a high circularity has been found, and the present invention has been completed.
【０００５】すなわち、本発明は、β化率５０％以上、
円形度０．８０以上であることを特徴とする窒化ケイ素
粉末である。また酸素量０．５〜１．８％、比表面積８
〜２２ｍ2/gであることを特徴とする前記の窒化ケイ素
粉末である。さらに蛍石（ＣａＦ2）を０．５〜５重量
％含有する金属シリコン粉を１３００℃より低い温度で
は窒素分圧を５００ｈＰａ以下で窒化反応をさせ、１３
００℃以上では５００ｈＰａ以上で窒化反応をさせるこ
とを特徴とする窒化ケイ素の製造方法である。That is, the present invention provides a β conversion rate of 50% or more,
A silicon nitride powder having a circularity of 0.80 or more. Further, the oxygen content is 0.5 to 1.8%, and the specific surface area is 8
ケ イ 素 22 m 2 / g is the silicon nitride powder described above. Further nitrogen partial pressure to the nitriding reaction below 500hPa fluorite metal silicon powder containing (CaF 2) 0.5 to 5 wt% at a temperature lower than 1300 ° C., 13
A method for producing silicon nitride, characterized in that a nitriding reaction is performed at 500 ° C. or more at a temperature of 00 ° C. or more.
【０００６】[0006]
【発明の実施形態】以下、更に詳しく本発明について説
明する。本発明に於いて高熱伝導率達成の為には原料と
なる窒化ケイ素粉末のβ化率は重要で、β化率５０％以
上が必要である。５０％より低いとすなわちα窒化ケイ
素が多くなると、窒化ケイ素粉末中の固溶酸素が多くな
り、焼結後の熱伝導性を阻害し、また焼結時の脱酸素に
時間がかかり、高温での処理が必要となるため好ましく
ない。β化率は好ましくは７０％以上であり、更に好ま
しくは９０％以上である。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, in order to achieve a high thermal conductivity, the β conversion rate of the silicon nitride powder as a raw material is important, and the β conversion rate is required to be 50% or more. If it is lower than 50%, that is, if the amount of α silicon nitride increases, the amount of dissolved oxygen in the silicon nitride powder increases, which impairs the thermal conductivity after sintering. This is not preferable because the above process is required. The β conversion is preferably 70% or more, and more preferably 90% or more.
【０００７】また、焼結時の粒成長方向をランダムにす
ることが重要であり、そのためには成形時の窒化ケイ素
粒子の偏った配向を抑制すること、すなわち平均円形度
が０．８０以上であることが必要である。０．８０より
小さいと、成形時に配向性を持つため、粒成長方向に偏
りが生じ、その結果熱伝導性にも偏りが起こるため好ま
しくない。窒化ケイ素粉末の円形度は好ましくは、０．
８５以上であり、更に好ましくは０．９０以上である。It is important that the direction of grain growth during sintering is random. For this purpose, it is necessary to suppress the unbalanced orientation of silicon nitride particles during molding, that is, when the average circularity is 0.80 or more. It is necessary to be. If it is less than 0.80, it has orientation during molding, so that a deviation occurs in the grain growth direction, and as a result, a deviation also occurs in the thermal conductivity. The circularity of the silicon nitride powder is preferably 0.
It is 85 or more, more preferably 0.90 or more.
【０００８】窒化ケイ素粉末中の酸素量は、０．５〜
１．８％であることが好ましい。０．５％より低いと焼
結性が阻害され、１．８％より高いと固溶酸素量が増加
するため、熱伝導性が阻害され好ましくない。より好ま
しくは、０．６〜１．２％であり、更に好ましくは、
０．７〜１．０％である。[0008] The amount of oxygen in the silicon nitride powder is 0.5 to
It is preferably 1.8%. If it is lower than 0.5%, the sinterability is impaired, and if it is higher than 1.8%, the amount of dissolved oxygen increases, so that thermal conductivity is impaired, which is not preferable. More preferably 0.6 to 1.2%, still more preferably,
0.7 to 1.0%.
【０００９】熱伝導を阻害するＡｌ量は少ないほどよ
い。３００ｐｐｍ以下が好ましく、３００ｐｐｍより多
いと、熱伝導率が低下するので好ましくない。より好ま
しくは２００ｐｐｍ以下であり、更に好ましくは１５０
ｐｐｍ以下である。The smaller the amount of Al that inhibits heat conduction, the better. The content is preferably 300 ppm or less, and if it is more than 300 ppm, thermal conductivity is undesirably reduced. It is more preferably at most 200 ppm, even more preferably 150 ppm
ppm or less.
【００１０】本発明においては、焼結性の面から、窒化
ケイ素粉末の比表面積が８〜２２ｍ 2/gとするのが好ま
しい。８ｍ2/gより小さいと、焼結性が阻害され、２２
ｍ2/gよりも大きいと窒化ケイ素粉末の嵩密度が小さく
なり、充填性が低く、スラリー化したときの粘度が上昇
し好ましくない。より好ましくは、１３〜１８ｍ2/gで
あり、更に好ましくは１５〜１７ｍ2/gである。[0010] In the present invention, from the viewpoint of sinterability, nitriding
Specific surface area of silicon powder is 8-22m Two/ g is preferred
New 8mTwoIf it is less than / g, sinterability is impaired and 22
mTwoIf it is larger than / g, the bulk density of the silicon nitride powder is small.
Low fillability and increased viscosity when slurried
But not preferred. More preferably, 13 to 18 mTwo/ g
Yes, more preferably 15-17mTwo/ g.
【００１１】窒化ケイ素粉末の平均粒子径は０．２〜
１．０μmとするのが好ましい。０．３μmより小さいと
嵩密度が小さくなり、充填性が低く、スラリー化したと
きの粘度が上昇し、１．０μmよりも大きいと焼結時に
粗大な粒子を形成し、焼結体強度が低下し好ましくな
い。より好ましくは０．３〜０．７μｍで、更に好まし
くは０．４〜０．６μmである。The average particle size of the silicon nitride powder is 0.2 to
Preferably it is 1.0 μm. If it is less than 0.3 μm, the bulk density becomes small, the filling property is low, the viscosity when slurried increases, and if it is more than 1.0 μm, coarse particles are formed at the time of sintering, and the strength of the sintered body decreases. But not preferred. It is more preferably 0.3 to 0.7 μm, and still more preferably 0.4 to 0.6 μm.
【００１２】次いで、本発明の窒化ケイ素粉末の製造方
法について説明する。金属シリコン窒化法を主体として
述べるが、本発明は下記以外の製造方法を許容するもの
である。Next, a method for producing the silicon nitride powder of the present invention will be described. Although the description will be made mainly on the metal silicon nitriding method, the present invention allows a manufacturing method other than the following.
【００１３】金属シリコン粉末は、平均粒子径５〜２０
μmである。特に平均粒子系が５〜１５μmで、粒度分布
がシャープな金属シリコン粉を用いると微細な窒化ケイ
素１次粒子を形成しやすく好ましい。平均粒子径が２０
μmより大きくなると、粗大な１次・２次粒子や柱状粒
子を形成しやすく、成形性および強度の面で不利であ
る。逆に５μmより小さいと微細な金属シリコン粉末が
増加し、酸素量が増加するため、固溶酸素量が多く、か
つ低β化率の微細なウィスカーを生成し、熱伝導性を阻
害する。また、金属シリコン粉末中のＡｌ量は５００ｐ
ｐｍ以下の高純度な金属シリコン粉末が好ましく、特に
２５０ｐｐｍ以下が好ましく、高熱伝導率化に有利であ
る。The metal silicon powder has an average particle size of 5 to 20.
μm. In particular, it is preferable to use metal silicon powder having an average particle size of 5 to 15 μm and a sharp particle size distribution since fine silicon nitride primary particles can be easily formed. Average particle size of 20
When it is larger than μm, coarse primary and secondary particles and columnar particles are easily formed, which is disadvantageous in terms of moldability and strength. Conversely, if it is less than 5 μm, the amount of fine metallic silicon powder increases and the amount of oxygen increases, so that fine whiskers with a large amount of dissolved oxygen and a low β ratio are generated, impeding the thermal conductivity. The amount of Al in the metal silicon powder is 500 p.
pm or less of high-purity metallic silicon powder is preferred, and particularly preferably 250 ppm or less, which is advantageous for increasing the thermal conductivity.
【００１４】また、金属シリコン粉末が窒化する際、窒
化した窒化ケイ素粒子同士の焼結を防ぐために、骨材と
して窒化ケイ素粉末を添加する。骨材となる窒化ケイ素
粉末は、低酸素、高比表面積、高純度であることが好ま
しく、添加量は金属シリコン粉末１００重量部に対して
５〜３０重量部が好ましい。骨材の添加量が５重量部よ
り少ないと、窒化ケイ素粒子同士の焼結が起こりやす
く、かつ粗大な柱状粒子を形成するため、粉砕性が悪
く、成形時の配向の原因となるため、熱伝導率が低下す
る。逆に３０重量部より多いと酸素量が増加し焼結体の
熱伝導率が低下する。When the metal silicon powder is nitrided, silicon nitride powder is added as an aggregate to prevent sintering of the nitrided silicon nitride particles. The silicon nitride powder used as the aggregate is preferably low in oxygen, high in specific surface area, and high in purity. The amount of addition is preferably 5 to 30 parts by weight based on 100 parts by weight of the metal silicon powder. If the added amount of the aggregate is less than 5 parts by weight, sintering of the silicon nitride particles is likely to occur, and coarse columnar particles are formed, so that the pulverizability is poor and the orientation during molding is caused. The conductivity decreases. Conversely, if it exceeds 30 parts by weight, the amount of oxygen increases and the thermal conductivity of the sintered body decreases.
【００１５】金属シリコン粉末と骨材との混合方法は、
両者を別々に粉砕してから混合してもよく、また粉砕と
混合を同時に行うこともできる。また、いずれの場合に
おいても、粉砕・混合時の不純物の混入、特にメディア
の摩耗による不純物の混入と金属シリコンの酸化には充
分留意すべきであり、特に高純度を必要とする場合に
は、窒化ケイ素製のメディアを使用し、非酸化性雰囲気
下で粉砕・混合を行うことが好ましい。The method of mixing the metallic silicon powder and the aggregate is as follows.
Both may be ground separately and then mixed, or the grinding and mixing may be performed simultaneously. In any case, sufficient attention should be paid to mixing of impurities during grinding and mixing, especially mixing of impurities due to abrasion of the media and oxidation of metallic silicon, especially when high purity is required. It is preferable to perform pulverization and mixing in a non-oxidizing atmosphere using a medium made of silicon nitride.
【００１６】また、窒化ケイ素粒子の円形度の向上およ
び低酸素化を促進するために蛍石（ＣａＦ2)を添加する
ことが必要である。ＣａＦ2は金属シリコン粉末の表面
にあるＳｉＯ2膜と反応して、ＳｉＯ2膜を除去するた
め、新生なＳｉ表面から発生するＳｉ（ｇ）が増加し、
このＳｉ（ｇ）とＮ2が気−気反応することで固溶酸素
量の少ない窒化ケイ素粉末が生成し、かつ窒化時の粒成
長を抑制することで柱状粒子を低減できる。添加量とし
ては、金属シリコン粉末１００重量部に対して０．５〜
５重量部である。好ましくは０．７〜４重量であり、更
に好ましくは０．８〜３重量部である。５重量部より多
いと、生成した窒化ケイ素中のＣａ分が増加するため、
後工程での精製が必要となるためコスト面で不利であ
る。０．５重量部以下では窒化反応が不安定となり、ま
た窒化ケイ素中の酸素が増加する。ＣａＦ2は金属シリ
コンと混合しても良いし、容器の底部に必要量のＣａＦ
2を置いても良い。Further, it is necessary to add fluorite (CaF 2) in order to improve the circularity of the silicon nitride particles and promote the reduction of oxygen. CaF 2 reacts with the SiO 2 film on the surface of the metal silicon powder to remove the SiO 2 film, so that Si (g) generated from the new Si surface increases,
A gas-gas reaction between Si (g) and N 2 produces a silicon nitride powder having a small amount of dissolved oxygen, and columnar particles can be reduced by suppressing grain growth during nitriding. The addition amount is 0.5 to 100 parts by weight of the metal silicon powder.
5 parts by weight. Preferably it is 0.7 to 4 parts by weight, more preferably 0.8 to 3 parts by weight. If it is more than 5 parts by weight, the Ca content in the generated silicon nitride increases,
This is disadvantageous in terms of cost because purification in a later step is required. If the amount is less than 0.5 part by weight, the nitridation reaction becomes unstable, and oxygen in silicon nitride increases. CaF 2 may be mixed with metallic silicon, or the required amount of CaF 2 may be added to the bottom of the container.
You may put 2 .
【００１７】更に、本発明においては、金属シリコン粉
末が気相反応により円滑に窒化反応をするのに必要な反
応空間を確保するために、金属シリコン粉末と骨材窒化
ケイ素粉末の集合体は、その緩め嵩密度を１．８ｇ／ｃ
ｍ3以下（気孔率で３５％以上）の集合体として、反応
炉に充填する。これ以外の集合体では、気−固反応が主
体となるため、反応が大きな発熱を伴い暴走的に進みや
すくなり、金属シリコン粉末原料が溶融したり、生成し
た窒化ケイ素粉末同士が焼結したりして、不純物の多
い、粉砕性のよくない、大きな塊状の窒化ケイ素インゴ
ットが生成し易いので好ましくない。従って、金属シリ
コン粉末と骨材窒化ケイ素粉末の集合体は、窒化ケイ素
または炭化ケイ素を主成分とする焼結体容器に自然充填
（成形なし）することが好ましい。Further, in the present invention, in order to secure a reaction space necessary for the metal silicon powder to smoothly undergo a nitriding reaction by a gas phase reaction, the aggregate of the metal silicon powder and the aggregate silicon nitride powder is Its loose bulk density is 1.8 g / c
as a set of m 3 or less (35% or more in porosity), to fill the reactor. In other aggregates, the gas-solid reaction is mainly performed, so that the reaction is likely to run out of control with large heat generation, the metal silicon powder raw material is melted, or the generated silicon nitride powder is sintered. As a result, a large lump of silicon nitride ingot containing many impurities and having poor pulverizability is easily generated, which is not preferable. Therefore, it is preferable that the aggregate of the metal silicon powder and the aggregate silicon nitride powder be naturally filled (without molding) in a sintered container mainly containing silicon nitride or silicon carbide.
【００１８】高β化率の窒化ケイ素粉末の製造において
は、通常窒素および／またはアンモニア雰囲気中、また
は不活性ガスや水素ガス等と併用した雰囲気中で、急速
昇温による窒化や高反応速度制御によるβ化の促進を行
うが、急速昇温では、低温での窒化を抑制仕切れず高β
化率を達成することができない。また、高反応速度で
は、シリコンの溶出や融着を誘発するとともに、粗大な
粒子や柱状粒子を生成しやすい。そこで本発明において
は、低温での窒化を抑制するため、１，３００℃より低
い温度領域では不活性ガスによる一部置換を行い、窒素
ガス分圧が５００ｈＰａ以下好ましくは、３００ｈＰａ
以下更に好ましくは１５０ｈＰａに制御するのが好まし
い。１，３００℃に達した時点で、反応ガスである窒素
ガス分圧を５００ｈＰａ以上にすることで、高β化率の
窒化ケイ素粉末が得られることを見いだした。１，３０
０℃より高い温度まで不活性ガス中で昇温すると、金属
シリコンの溶出や融着が顕著になり、１，３００℃より
低い温度から窒素ガス分圧を高くすると、生成した窒化
ケイ素粉末の１次粒子の円形度が低く、また結晶相は低
β化率となる。In the production of silicon nitride powder having a high β conversion rate, nitridation or high reaction rate control is usually carried out by rapidly raising the temperature in an atmosphere of nitrogen and / or ammonia, or an atmosphere used in combination with an inert gas or hydrogen gas. However, with rapid temperature rise, nitridation at low temperatures cannot be suppressed and high β
Conversion rate cannot be achieved. In addition, at a high reaction rate, elution and fusion of silicon are induced, and coarse particles and columnar particles are easily generated. Therefore, in the present invention, in order to suppress nitriding at a low temperature, partial replacement with an inert gas is performed in a temperature range lower than 1,300 ° C., and a partial pressure of nitrogen gas is 500 hPa or less, preferably 300 hPa.
Hereinafter, it is more preferable to control the pressure to 150 hPa. When the temperature reached 1,300 ° C., it was found that by setting the partial pressure of the nitrogen gas as the reaction gas to 500 hPa or more, a silicon nitride powder having a high β conversion rate was obtained. 1,30
When the temperature is raised to a temperature higher than 0 ° C. in an inert gas, the elution and fusion of metallic silicon become remarkable. When the partial pressure of nitrogen gas is increased from a temperature lower than 1,300 ° C., 1 The circularity of the secondary particles is low, and the crystal phase has a low β conversion rate.
【００１９】窒化に際しては、特に１３００℃以上で完
全窒化するまでの最大反応速度を７％／ｈｒ以下特に５
％／ｈｒ以下にして窒化させることが好ましい。これ以
上の反応速度になると、粗大な粒子や柱状粒子を形成し
やすくなる。そのため、１，３００℃からの窒素ガス分
圧の上昇に際しては、最大反応速度が７％／ｈｒ以下と
なるように窒素ガスの濃度を制御する必要がある。In the case of nitriding, the maximum reaction rate until complete nitriding at 1300 ° C. or more is 7% / hr or less, especially 5%.
% / Hr or less. When the reaction rate is higher than this, coarse particles and columnar particles are easily formed. Therefore, when increasing the partial pressure of nitrogen gas from 1,300 ° C., it is necessary to control the concentration of nitrogen gas so that the maximum reaction rate is 7% / hr or less.
【００２０】窒化反応終了後、窒素ガスを流しながら室
温まで冷却し、生成したインゴットを取り出す。インゴ
ットは、ジョークラッシャーやロールクラッシャーなど
により粗粉砕される。 本発明の窒化ケイ素粉末は、こ
のような粗粉砕窒化ケイ素粉末を更に微粉砕すること、
または微粉砕された粉末を分級することで得ることがで
きる。微粉砕機の様式については、大まかに乾式粉砕と
湿式粉砕とに分けられる。乾式粉砕では、ボールミル、
振動ミルまたは攪拌粉砕機等の媒体式粉砕機や、ジェッ
トミル等の衝撃式粉砕機で粉砕することが必要となる。
粉砕の際には、酸素量の増加に注意する必要があり、非
酸化雰囲気下で粉砕することが好ましい。またメディア
については、鉄系ボールを使用する場合、粉砕後脱鉄を
行い、また、セラミックス系のボールを使用する際は、
Ａｌ量の少ないメディアを使用することが好ましい。更
に分級においては乾式の気流分級機等を使用することが
できる。湿式粉砕では、窒化ケイ素粉末の粉砕が進みや
すく、その結果、２次粒子がほぼ１次粒子になるまで粉
砕されるため有利である。粉砕メディアとしては、セラ
ミック系のボールまたは鉄系のボールを使用することが
できるが、乾式の場合と同様に、セラミックス系ボール
では、Ａｌ量の少ないメディアを使用し、鉄系のボール
では脱鉄やＨＣｌによる酸処理が必要となる。さらに酸
素量を低減するため、ＨＦ処理を行うのが好ましい。After completion of the nitriding reaction, the mixture is cooled to room temperature while flowing nitrogen gas, and the produced ingot is taken out. The ingot is coarsely crushed by a jaw crusher, a roll crusher, or the like. The silicon nitride powder of the present invention is obtained by further finely pulverizing such coarsely pulverized silicon nitride powder,
Alternatively, it can be obtained by classifying finely pulverized powder. The type of the pulverizer is roughly divided into dry pulverization and wet pulverization. In dry grinding, ball mill,
It is necessary to pulverize with a media pulverizer such as a vibration mill or a stirring pulverizer or an impact pulverizer such as a jet mill.
At the time of pulverization, it is necessary to pay attention to an increase in the amount of oxygen, and pulverization is preferably performed in a non-oxidizing atmosphere. Also, for media, when using iron-based balls, perform de-ironing after grinding, and when using ceramic-based balls,
It is preferable to use a medium having a small amount of Al. Further, in classification, a dry-type airflow classifier or the like can be used. In wet pulverization, the pulverization of the silicon nitride powder is easy to proceed, and as a result, pulverization is performed until the secondary particles become substantially primary particles, which is advantageous. As the pulverizing media, ceramic balls or iron balls can be used. As in the case of the dry type, ceramic balls use a medium with a small amount of Al, and iron balls use deironing media. Or HCl acid treatment is required. In order to further reduce the amount of oxygen, HF treatment is preferably performed.
【００２１】[0021]
【実施例】実験例１〜６ Ａｌ量２００ｐｐｍの高純度金属シリコン粉末を窒化ケ
イ素製ボールを用いた振動ミルにより粉砕し、平均粒子
径を１３μmとした。得られた金属シリコン粉末１００
重量部に骨材（電気化学工業株式会社製窒化ケイ素粉
末：商品名「ＳＮ−Ｐ２１ＦＣ」）１０重量部、及び表
１に示す添加量でＣａＦ2を加え、振動ミルで粉砕・混
合し、窒化ケイ素を主成分とする焼結体容器に嵩密度が
０．８〜１．０ｇ／ｃｍ3となるように自然充填し、バ
ッチ式の反応炉に容器ごと充填し、窒化を行った。EXPERIMENTAL EXAMPLES 1-6 High-purity metallic silicon powder having an Al content of 200 ppm was pulverized by a vibration mill using silicon nitride balls to have an average particle diameter of 13 μm. Obtained metal silicon powder 100
10 parts by weight of aggregate (silicon nitride powder manufactured by Denki Kagaku Kogyo Co., Ltd .: trade name “SN-P21FC”) and CaF 2 in the amounts shown in Table 1 were added to the parts by weight, and the mixture was ground and mixed by a vibration mill, and nitrided The sintered container mainly containing silicon was naturally filled so as to have a bulk density of 0.8 to 1.0 g / cm 3, and the whole container was filled in a batch-type reaction furnace, followed by nitriding.
【００２２】炉内の酸素濃度が５００ｐｐｍ以下になる
ように窒素ガス置換した後、昇温を開始し、窒化反応が
開始しない５００℃から不活性ガスであるアルゴンガス
を導入し８００℃までの間に窒素ガス分圧を５００ｈＰ
ａとした。その後更に１，３００℃になるまでアルゴン
ガスを導入しながら昇温し、１，３００℃に達した時点
で反応ガスである窒素ガスとアルゴンガスの混合ガスを
導入し、窒素分圧が５００ｈＰａ以上を維持しながら
１，４５０℃まで昇温した。窒化の際には、最大反応速
度が５％／ｈｒ以下になるように、窒素ガスとアルゴン
ガスの混合比を制御しながら窒化反応を行った。After purging with nitrogen gas so that the oxygen concentration in the furnace becomes 500 ppm or less, the temperature is raised, and from 500 ° C. at which the nitridation reaction does not start up to 800 ° C. by introducing an inert gas such as argon gas. Nitrogen gas partial pressure 500hP
a. Thereafter, the temperature was further increased while introducing argon gas until the temperature reached 1,300 ° C., and when the temperature reached 1,300 ° C., a mixed gas of nitrogen gas and argon gas as a reaction gas was introduced, and the nitrogen partial pressure was 500 hPa or more. The temperature was raised to 1,450 ° C. while maintaining the temperature. At the time of nitriding, the nitriding reaction was performed while controlling the mixture ratio of nitrogen gas and argon gas so that the maximum reaction rate was 5% / hr or less.
【００２３】このようにして得られた窒化ケイ素インゴ
ットをジョークラッシャーおよびロールクラッシャーに
より粗砕した。The silicon nitride ingot thus obtained was crushed by a jaw crusher and a roll crusher.
【００２４】粗砕した窒化ケイ素粉末を鉄系ボールを粉
砕メディアとした湿式アトライターミル（容積５Ｌ）を
用いて、窒化ケイ素量１００重量部に対して水６００重
量部を添加し、粉砕ボール径３／１６インチを用いて、
２４時間粉砕を行ったのち、スラリーを抜き出した。Using a wet attritor mill (volume: 5 L) using the crushed silicon nitride powder and iron balls as grinding media, 600 parts by weight of water was added to 100 parts by weight of silicon nitride, and the diameter of the crushed ball was adjusted. Using 3/16 inch,
After crushing for 24 hours, the slurry was extracted.
【００２５】微粉砕を行ったスラリーに、３３０重量部
のＨＣｌを加え１時間拌した後、５０重量部のＨＦを加
え更に１時間攪拌した。この際スラリーの温度が５０〜
８０℃の範囲になるように、テフロンコーティングのヒ
ーターにて加温した。その後、スラリーｐＨが４〜５に
なるまで水によるデカンテーションを行い、その後更に
水による洗浄かつ吸引濾過を行った。To the pulverized slurry, 330 parts by weight of HCl was added, and the mixture was stirred for 1 hour. Then, 50 parts by weight of HF was added, and the mixture was further stirred for 1 hour. At this time, the temperature of the slurry is 50 ~
It was heated by a Teflon-coated heater so as to be in the range of 80 ° C. Thereafter, decantation with water was performed until the slurry pH reached 4 to 5, and then washing with water and suction filtration were further performed.
【００２６】次に、濾過した窒化ケイ素の集合体を１５
０℃の乾燥機にて５ｈの乾燥を行い、乾燥した集合体を
ウレタン製のロールクラッシャーで粗砕した後、窒化ケ
イ素製ボールを粉砕メディアとした乾式のボールミルを
用いて、解砕を行い、窒化ケイ素粉末を得た。Next, the aggregate of the filtered silicon nitride
After drying for 5 hours with a dryer at 0 ° C., the dried aggregate was roughly crushed by a urethane roll crusher, and then crushed using a dry ball mill using silicon nitride balls as a grinding media, A silicon nitride powder was obtained.
【００２７】実験例７〜９は、窒素／アルゴンの混合ガ
スを１１００℃から導入し、窒素ガス分圧を１１５０℃
から１０００ｈＰａ前後を維持して窒化反応させた以外
は、実験例１〜６と同様にして行った。実験例１０、１
１は粉砕時間をそれぞれ８時間、４８時間とした以外は
実験例４と同様にして調整した。In Experimental Examples 7 to 9, a nitrogen / argon mixed gas was introduced from 1100 ° C., and the nitrogen gas partial pressure was increased to 1150 ° C.
Approximately 1000 hPa, and the reaction was performed in the same manner as in Experimental Examples 1 to 6, except that the nitriding reaction was performed. Experimental Examples 10 and 1
Sample No. 1 was prepared in the same manner as in Experimental Example 4 except that the pulverizing times were 8 hours and 48 hours, respectively.
【００２８】次に、得られた窒化ケイ素粉末のβ化率を
測定した。β化率は、Ｘ線回折装置（理学電機社製Ｇｅ
ｉｇｅｒ Ｆｌｅｘ２０１３型）にて２θ＝３２゜〜３
８゜の範囲で測定し、Ｘ線回折チャートに記録した後、
チャート上の３５．２゜（α−窒化けい素［210］
面）、３４．５#（α−窒化けい素［102］面）、３６．
０゜（β−窒化けい素［210］面）及び、３３．５゜
（β−窒化けい素［101］面）の回折線から各々のピー
ク高さを測定し、次式により算出した。 β化率＝（Ｂ＋Ｂ'）／（Ａ＋Ａ'＋Ｂ＋Ｂ'）×１００ （％） Ａ…α−窒化けい素［210］面のピーク高さ(mm)→３
５．２゜ Ａ'…α−窒化けい素［102］面のピーク高さ(mm)→３
４．５゜ Ｂ…β−窒化けい素［210］面のピーク高さ(mm)→３
６．０゜ Ｂ'…β−窒化けい素［101］面のピーク高さ(mm)→３
３．５゜Next, the β conversion of the obtained silicon nitride powder was measured. The β conversion rate was measured using an X-ray diffractometer (Rigaku Denki
igger Flex2013) 2θ = 32 ゜ ～ 3
After measuring in the range of 8 ° and recording it on the X-ray diffraction chart,
35.2% on the chart (α-silicon nitride [210]
Surface), 34.5 # (α-silicon nitride [102] surface), 36.
Each peak height was measured from diffraction lines of 0 ° (β-silicon nitride [210] plane) and 33.5 ° (β-silicon nitride [101] plane), and calculated by the following formula. β conversion = (B + B ′) / (A + A ′ + B + B ′) × 100 (%) A: peak height of α-α-silicon nitride [210] plane (mm) → 3
5.2 ゜ A ': peak height (mm) of α-silicon nitride [102] plane → 3
4.5 ゜ B: peak height of β-silicon nitride [210] plane (mm) → 3
6.0 ゜ B '... peak height of β-silicon nitride [101] plane (mm) → 3
3.5 ゜
【００２９】酸素量は、窒化ケイ素粉末を助燃剤ととも
にグラファイトルツボに入れ、インパルス炉中で加熱
し、生成したＣＯガスを赤外線吸収法により定量しを算
出した。測定には酸素・窒素同時分析装置（ＨＯＲＩＢ
Ａ ＥＭＧＡ−２８００）を用い、標準試料に(社)日本
セラミックス協会の窒化けい素粉末ＪＣＲＭ Ｒ００４
を使用した。The oxygen content was calculated by placing the silicon nitride powder in a graphite crucible together with an auxiliary agent, heating the powder in an impulse furnace, and quantifying the generated CO gas by an infrared absorption method. Oxygen and nitrogen simultaneous analyzer (HORIB)
A EMGA-2800) and used as a standard sample a silicon nitride powder JCRM R004 of the Japan Ceramics Association.
It was used.
【００３０】Ａｌ量は、窒化ケイ素を加圧酸分解後、ふ
っ化水素酸によりけい酸を揮発し残留物を酸に溶解さ
せ、この溶液中のＡｌをＩＣＰ−ＡＥＳにより定量する
ことで測定した。The amount of Al was measured by subjecting silicon nitride to acid decomposition under pressure, volatilizing silicic acid with hydrofluoric acid to dissolve the residue in the acid, and quantifying Al in this solution by ICP-AES. .
【００３１】比表面積は、窒化ケイ素粉末の表面に吸着
ガスと不活性キャリアガスとの混合ガスを吸着させて測
定した。装置は湯浅アイオニクス社製カンターソーブを
用いた。The specific surface area was measured by adsorbing a mixed gas of an adsorbed gas and an inert carrier gas on the surface of a silicon nitride powder. The apparatus used was Cantersorb from Yuasa Ionics.
【００３２】平均粒子径は、レーザー散乱式粒度測定計
（ＬＥＤＳandＮＯＲＴＨＲＵＰ社製マイクロトラック
ＳＰＡ７９９７型）により測定し求めた。The average particle diameter was determined by measuring with a laser scattering particle size analyzer (Microtrack SPA7997 manufactured by LED Sandnorthrup).
【００３３】窒化ケイ素粒子の円形度は、フロー式粒子
像分析装置（東亞医用電子株式会社製ＦＰＩＡ−１００
０）にて測定した。また、測定に際しては、測定粒子数
が１０００個以上になるように、試料濃度を調整した。The circularity of the silicon nitride particles can be measured by a flow type particle image analyzer (FPIA-100 manufactured by Toa Medical Electronics Co., Ltd.).
0). At the time of measurement, the sample concentration was adjusted so that the number of particles to be measured was 1000 or more.
【００３４】焼結体は、窒化ケイ素粉末９２重量部、Ｙ
2Ｏ3粉末８重量部を混合し、得られた混合粉末６５重量
部に有機バインダー２０重量部および水１５重量部を加
え湿式混合することでスラリー化し、１２ｍｍφ丸棒を
押出成形した後乾燥し、窒素雰囲気下温度１９００℃で
８時間焼成することで得た。焼結体を押出方向と平行及
び垂直方向に厚さ１ｍｍの試片に切り出し熱伝導率測定
試片を得た。熱伝導率については、窒化ケイ素焼結体を
レーザーフラッシュ法にて測定した。表１に各実験によ
って得られた窒化ケイ素粉末の特性とそれぞれの粉末を
用いて得られた焼結体の熱伝導率を示す。表１において
平行とは、押し出し方向に垂直に切り出したサンプルを
用いて測定したもので、熱伝導の測定方向が押出し方向
に平行な方向を測定したことを意味する。The sintered body was composed of 92 parts by weight of silicon nitride powder, Y
8 parts by weight of 2 O 3 powder are mixed, and 20 parts by weight of an organic binder and 15 parts by weight of water are added to 65 parts by weight of the obtained mixed powder, and the mixture is wet-mixed to form a slurry. And calcined at 1900 ° C. for 8 hours in a nitrogen atmosphere. The sintered body was cut into a specimen having a thickness of 1 mm in a direction parallel and perpendicular to the extrusion direction to obtain a thermal conductivity measurement specimen. The thermal conductivity of the silicon nitride sintered body was measured by a laser flash method. Table 1 shows the characteristics of the silicon nitride powder obtained in each experiment and the thermal conductivity of the sintered body obtained using each powder. In Table 1, “parallel” is measured using a sample cut out perpendicular to the extrusion direction, and means that the direction of measurement of heat conduction is parallel to the extrusion direction.
【００３５】[0035]
【表１】 [Table 1]
【００３６】[0036]
【発明の効果】本発明の窒化ケイ素粉末を用いれば、高
熱伝導率で熱伝導性の異方性の少ない焼結体を得ること
ができる。また本発明の方法により該粉末を容易に得る
ことができる。By using the silicon nitride powder of the present invention, it is possible to obtain a sintered body having high thermal conductivity and low thermal conductivity anisotropy. Further, the powder can be easily obtained by the method of the present invention.
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 4G001 BA62 BA71 BA82 BB32 BB71 BB73 BC01 BC13 BC46 BC48 BC52 BC54 BE03 BE22 BE23 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G001 BA62 BA71 BA82 BB32 BB71 BB73 BC01 BC13 BC46 BC48 BC52 BC54 BE03 BE22 BE23
Claims (3)
あることを特徴とする窒化ケイ素粉末。1. A silicon nitride powder having a β conversion of 50% or more and a circularity of 0.80 or more.
２ｍ2/gであることを特徴とする請求項１記載の窒化ケ
イ素粉末。2. An oxygen content of 0.5 to 1.8% and a specific surface area of 8 to 2
The silicon nitride powder according to claim 1, wherein the powder is 2 m 2 / g.
する金属シリコン粉を１３００℃より低い温度では窒素
分圧を５００ｈＰａ以下で窒化反応をさせ、１３００℃
以上では５００ｈＰａ以上で窒化反応をさせることを特
徴とする窒化ケイ素の製造方法。Wherein fluorite (CaF 2) a nitrogen partial pressure by the nitriding reaction below 500hPa at temperatures below 1300 ° C. The metallic silicon powder containing 0.5 to 5% by weight, 1300 ° C.
In the above, a method for producing silicon nitride, wherein the nitriding reaction is performed at 500 hPa or more.
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