JPH05139840A - Siliceous nitride sintered compact and its production - Google Patents
Siliceous nitride sintered compact and its productionInfo
- Publication number
- JPH05139840A JPH05139840A JP3306100A JP30610091A JPH05139840A JP H05139840 A JPH05139840 A JP H05139840A JP 3306100 A JP3306100 A JP 3306100A JP 30610091 A JP30610091 A JP 30610091A JP H05139840 A JPH05139840 A JP H05139840A
- Authority
- JP
- Japan
- Prior art keywords
- silicon nitride
- oxide
- rare earth
- earth element
- crystal phase
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、低温焼成が可能である
とともに室温から高温までの強度特性に優れ、特に、自
動車用部品やガスタ−ビンエンジン用部品等に使用され
る窒化珪素質焼結体およびその製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of low temperature firing and has excellent strength characteristics from room temperature to high temperature, and in particular, it is a silicon nitride sintered material used for automobile parts, gas turbine engine parts and the like. The present invention relates to a body and a method for manufacturing the body.
【０００２】[0002]
【従来の技術】従来から、窒化珪素質焼結体は、耐熱
性、耐熱衝撃性および耐酸化性に優れることからエンジ
ニアリングセラミックス、特にタ−ボロ−タ−等の熱機
関用として応用が進められている。2. Description of the Related Art Conventionally, silicon nitride sintered bodies are excellent in heat resistance, thermal shock resistance and oxidation resistance, and therefore, their application has been promoted for engineering ceramics, especially for heat engines such as turbochargers. ing.
【０００３】かかる窒化珪素は、それ自体が難焼結性で
あることから、従来より高密度で高強度の焼結体を作製
するために焼結助剤としてＹ2 Ｏ3 等の希土類酸化物や
酸化アルミニウムを添加することが特公昭５２−３６４
９号、特公昭５８−５１９０号にて提案されている。Since such silicon nitride itself is difficult to sinter, rare earth oxides such as Y 2 O 3 are used as a sintering aid in order to produce a sintered body having a higher density and higher strength than conventional ones. And the addition of aluminum oxide
No. 9 and Japanese Patent Publication No. 58-5190.
【０００４】また、組織的には窒化珪素結晶の粒界成分
を結晶化させ、例えば、Ｓｉ3 Ｎ4 −ＲＥ2 Ｏ3 （Ｒ
Ｅ：希土類元素）−ＳｉＯ2 系の高融点の結晶相を形成
することにより高温における強度を高めようとする提案
がなされている。Further, structurally, the grain boundary component of the silicon nitride crystal is crystallized and, for example, Si 3 N 4 —RE 2 O 3 (R
E: A proposal has been made to increase the strength at high temperature by forming a high melting point crystal phase of a rare earth element) -SiO 2 system.
【０００５】[0005]
【発明が解決しようとする問題点】従来より提案されて
いる焼結助剤において、酸化イットリウムと酸化アルミ
ニウムを併用するとその焼結性が非常に向上し比較的低
温での焼成により高密度化が達成できることが知られて
いるが、室温、高温における強度が実用的なレベルには
達しておらず、機械的特性の改良が望まれている。DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the conventionally proposed sintering aid, when yttrium oxide and aluminum oxide are used together, the sinterability is greatly improved and the densification is improved by firing at a relatively low temperature. It is known that this can be achieved, but the strength at room temperature and high temperature has not reached a practical level, and improvement in mechanical properties is desired.
【０００６】また、粒界にＳｉ3 Ｎ4 −ＲＥ2 Ｏ3 （Ｒ
Ｅ：希土類元素）−ＳｉＯ2 系の高融点の結晶相を析出
させる方法によれば、系全体の焼結性はＡｌ2 Ｏ3 添加
系に比較して劣るために高温での焼結を必要とするなど
の問題があり、特性的にも靱性が低いという問題もあっ
た。Further, Si 3 N 4 --RE 2 O 3 (R
E: According to the method for precipitating the rare earth element) -SiO 2 based high melting point of the crystalline phase of the sintering of the entire system requires sintering at high temperatures is inferior as compared to the Al 2 O 3 addition system There is also a problem that the toughness is low in terms of characteristics.
【０００７】よって、本発明は、室温から高温まで自動
車用部品やガスタ−ビンエンジン用部品等で使用される
温度域においてに充分な強度特性、特に、室温から１０
００℃の高温までの抗折強度に優れるとともに、低温で
の焼成が可能な窒化珪素質焼結体およびその製造方法を
提供することを目的とするものである。Therefore, the present invention has sufficient strength characteristics in the temperature range used in automobile parts, gas turbine engine parts and the like from room temperature to high temperature, and particularly from room temperature to 10
It is an object of the present invention to provide a silicon nitride sintered body which is excellent in bending strength up to a high temperature of 00 ° C. and can be sintered at a low temperature, and a method for producing the same.
【０００８】[0008]
【問題点を解決するための手段】本発明者等は、焼結体
の強度特性を高めるためには、焼結体の組成および焼結
体中の窒化珪素結晶相の形状や、窒化珪素相の粒界に存
在する副相を制御することが重要であるという見地に基
づき検討を重ねた結果、窒化珪素を主体とし、これに希
土類元素酸化物、酸化アルミニウム、酸化珪素を添加す
るとともにリチウム化合物を所定の割合で添加すること
により系の焼結性が向上し、低温での焼成が可能となる
とともに焼結体中においてリチウムを含む酸化物の結晶
相を析出させることにより室温から高温まで優れた強度
特性を有する焼結体が得られることを知見し、本発明に
至った。The inventors of the present invention have found that in order to enhance the strength characteristics of a sintered body, the composition of the sintered body, the shape of the silicon nitride crystal phase in the sintered body, the silicon nitride phase, and the like. As a result of repeated studies based on the viewpoint that it is important to control the sub-phase existing at the grain boundaries of Al2O3, silicon nitride is the main component, and rare-earth element oxides, aluminum oxide, and silicon oxide are added to this, and lithium compounds are added. Sinterability of the system is improved by adding at a predetermined ratio, making it possible to perform firing at low temperature, and by precipitating a crystalline phase of an oxide containing lithium in the sintered body, it is excellent from room temperature to high temperature. The present invention has been accomplished by finding that a sintered body having excellent strength characteristics can be obtained.
【０００９】即ち、本発明は、窒化珪素を主成分とし、
これに希土類元素酸化物、酸化アルミニウム、酸化珪素
を合計で６〜４０モル％、リチウム化合物をＬｉ2 Ｏ換
算で０．５〜１０モル％の割合で添加することにより、
１８００℃以下の窒素を含む非酸化性雰囲気で十分に焼
結することができるもので、さらに、焼結後に６００〜
１５００℃の非酸化性雰囲気中で熱処理を施すことによ
り、窒化珪素結晶相と、少なくともリチウムを含む酸化
物の結晶相、および少なくともアルミニウムと希土類元
素を含む粒界相を生成させることを特徴とするものであ
る。That is, the present invention is mainly composed of silicon nitride,
By adding a rare earth element oxide, aluminum oxide, and silicon oxide to this in an amount of 6 to 40 mol% in total and a lithium compound in a ratio of 0.5 to 10 mol% in terms of Li 2 O,
It can be sufficiently sintered in a non-oxidizing atmosphere containing nitrogen at 1800 ° C. or lower, and further, after sintering, 600 to
A heat treatment is performed in a non-oxidizing atmosphere at 1500 ° C. to generate a silicon nitride crystal phase, an oxide crystal phase containing at least lithium, and a grain boundary phase containing at least aluminum and a rare earth element. It is a thing.
【００１０】以下、本発明を詳述する。The present invention will be described in detail below.
【００１１】本発明の窒化珪素質焼結体は、窒化珪素を
主成分とし、これに添加成分として、希土類元素、リチ
ウム、アルミニウムおよび酸素を含むものである。The silicon nitride sintered material of the present invention contains silicon nitride as a main component, and contains a rare earth element, lithium, aluminum and oxygen as additional components.
【００１２】ここで、焼結体中の酸素は通常、希土類元
素、アルミニウム、リチウムと結合しているが、焼結体
中にはそれらの酸素以外に過剰に酸素が存在する。この
ような過剰酸素は、焼結体中の全酸素量から焼結体中の
希土類元素、アルミニウム元素、リチウム元素が化学量
論的に酸化物を形成した場合に各元素に結合している酸
素を除く残りの酸素量であり、そのほとんどは窒化珪素
原料に含まれる酸素、あるいは、ＳｉＯ2 等の添加とし
て混入するものであり、本発明では全てＳｉＯ2 として
存在するものとして考慮する。Here, the oxygen in the sintered body is usually bound to the rare earth element, aluminum and lithium, but excess oxygen exists in addition to the oxygen in the sintered body. Such excess oxygen is oxygen bound to each element when the rare earth element, aluminum element, and lithium element in the sintered body form an oxide stoichiometrically from the total amount of oxygen in the sintered body. Is the amount of oxygen remaining, except for oxygen that is contained in the silicon nitride raw material, or that is mixed in as addition of SiO 2 or the like, and in the present invention, it is considered that all is present as SiO 2 .
【００１３】本発明の焼結体は、組織上、窒化珪素結晶
相を主結晶相とするものであり、そのほとんどはβ−Ｓ
ｉ3 Ｎ4 からなるが、場合によっては少量の酸化アルミ
ニウム（Ａｌ2 Ｏ3 ）が固溶し、Ｓｉ−Ａｌ−Ｏ−Ｎ
（サイアロン）を形成することもある。また、この主相
は一般に柱状形状をなすがその平均粒径（短径）が１．
５μｍ以下、アスペクト比２〜１５であることが強度、
靱性向上の点から好ましい。The sintered body of the present invention has a silicon nitride crystal phase as a main crystal phase because of its structure, and most of them are β-S.
i 3 N 4 , but in some cases a small amount of aluminum oxide (Al 2 O 3 ) forms a solid solution to form Si-Al-O-N.
(Sialon) may be formed. Further, this main phase generally has a columnar shape, but its average particle size (minor axis) is 1.
The strength is 5 μm or less and the aspect ratio is 2 to 15,
It is preferable from the viewpoint of improving toughness.
【００１４】また、本発明によれば、上記の結晶相の粒
界に、少なくともリチウムを含む結晶相が存在すること
が重要である。この結晶相は例えば、ＬｉＡｌＳｉ
Ｏ4 、ＬｉＡｌＳｉ2 Ｏ6 、ＬｉＲＥＳｉＯ4 （ＲＥ：
希土類元素）で表される結晶相で、単独または複数が混
在して存在する。この結晶相は、焼結過程では液相とし
て存在し、焼結性を高めて低温焼成が可能となり窒化珪
素結晶相の異常粒成長を抑制する。しかし、そのままガ
ラス相として粒界相に残存すると高温強度を低下させて
しまうので、結晶相として粒界相から析出させることに
より、熱膨張差に基づく残留応力が発生し焼結体の破壊
靱性を高めるとともに高温強度を高めることができる。Further, according to the present invention, it is important that a crystal phase containing at least lithium is present at the grain boundary of the crystal phase. This crystal phase is, for example, LiAlSi
O 4 , LiAlSi 2 O 6 , LiRESiO 4 (RE:
It is a crystal phase represented by (rare earth element) and exists alone or in a mixture of two or more. This crystal phase exists as a liquid phase in the sintering process, enhances sinterability, enables low temperature firing, and suppresses abnormal grain growth of the silicon nitride crystal phase. However, if the glass phase remains as it is in the grain boundary phase, the high temperature strength will decrease. Therefore, by precipitating from the grain boundary phase as a crystal phase, residual stress due to the difference in thermal expansion occurs and the fracture toughness of the sintered body is improved. It is possible to increase the high temperature strength as well as the high temperature.
【００１５】本発明の焼結体中に少なくとも上記２種の
結晶相が生成されるが、これらの結晶相の粒界には珪
素、アルミニウム、希土類元素、酸素、窒素からなる粒
界相が形成される。この粒界相はそれ自体非晶質、結晶
質のいずれであっても差支えない。At least the above-mentioned two types of crystal phases are generated in the sintered body of the present invention, and a grain boundary phase composed of silicon, aluminum, a rare earth element, oxygen and nitrogen is formed at the grain boundaries of these crystal phases. To be done. This grain boundary phase may be amorphous or crystalline in itself.
【００１６】なお、本発明に用いられる希土類元素とし
てはＹやＹｂ、Ｅｒ、Ｄｙ、Ｈｏ等のランタノイド元素
が挙げられる。Examples of rare earth elements used in the present invention include lanthanoid elements such as Y, Yb, Er, Dy and Ho.
【００１７】次に、本発明の窒化珪素質焼結体の製造方
法によれば、原料粉末として窒化珪素粉末、希土類酸化
物粉末、酸化アルミニウム粉末およびリチウム化合物粉
末、さらに必要により酸化珪素粉末を用いる。リチウム
化合物としては、例えば、例えばＬｉ2 ＣＯ3 、ＬｉＡ
ｌＯ2 、ＬｉＹＯ4 、Ｌｉ2 ＳｉＯ3 、Ｌｉ2 Ｓｉ2 Ｏ
5 等が挙げられるが、Ｌｉ2 ＣＯ3 は化学的に不安定で
あり、融点が低いことからその他のＡｌ、Ｓｉあるいは
希土類元素等との複合酸化物粉末を用いることが望まし
い。Next, according to the method for producing a silicon nitride sintered material of the present invention, silicon nitride powder, rare earth oxide powder, aluminum oxide powder and lithium compound powder, and if necessary, silicon oxide powder are used as raw material powders. .. Examples of the lithium compound include, for example, Li 2 CO 3 and LiA.
lO 2 , LiYO 4 , Li 2 SiO 3 , Li 2 Si 2 O
5 and the like, Li 2 CO 3 is chemically unstable and has a low melting point, so that it is desirable to use a complex oxide powder with other Al, Si, a rare earth element or the like.
【００１８】窒化珪素粉末はそれ自体α−Ｓｉ3 Ｎ4 、
β−Ｓｉ3 Ｎ4 のいずれでも用いることができ、窒化珪
素粉末の平均粒径は０．４〜１．２μｍであることが望
ましい。The silicon nitride powder itself is α-Si 3 N 4 ,
Any of β-Si 3 N 4 can be used, and the average particle size of the silicon nitride powder is preferably 0.4 to 1.2 μm.
【００１９】これらは、窒化珪素を主成分とし、希土類
元素酸化物、酸化アルミニウム、酸化珪素が合計で６〜
４０モル％、リチウム化合物がＬｉ2 Ｏ換算で０．５〜
１０モル％となる割合で混合する。ここで酸化珪素は窒
化珪素原料中に含まれる不純物酸素をＳｉＯ2 換算した
量およびＬｉ化合物中のＳｉＯ2 成分も含めたものであ
る。これらの量を上記の範囲に限定したのは、希土類元
素酸化物、酸化アルミニウム、酸化珪素の合計量が６モ
ル％より少ないと低温での緻密化が達成されず、４０モ
ル％より多いと、機械的特性が不十分となる。リチウム
化合物の量が０．５モル％より少ないと低温での緻密化
が達成されず、１０モル％より多いと高温での機械的特
性が不十分となるからである。These are mainly composed of silicon nitride, and the total amount of rare earth element oxide, aluminum oxide and silicon oxide is 6 to 6.
40 mol%, 0.5 lithium compound with Li 2 O in terms
Mix at a ratio of 10 mol%. Here, silicon oxide includes the amount of impurity oxygen contained in the silicon nitride raw material converted into SiO 2 and the SiO 2 component in the Li compound. The amount of these elements is limited to the above range because if the total amount of the rare earth element oxide, aluminum oxide and silicon oxide is less than 6 mol%, densification at low temperature cannot be achieved, and if it is more than 40 mol%, Inadequate mechanical properties. This is because if the amount of the lithium compound is less than 0.5 mol%, densification at low temperature cannot be achieved, and if it is more than 10 mol%, the mechanical properties at high temperature become insufficient.
【００２０】なお、望ましくは、希土類元素酸化物０．
５〜１０モル％、酸化アルミニウムが０．５〜１０モル
％、酸化珪素が２０モル％以下で添加する。Desirably, rare earth element oxides of 0.
5 to 10 mol%, aluminum oxide is 0.5 to 10 mol%, and silicon oxide is 20 mol% or less.
【００２１】このようにして得られた混合粉末を公知の
成形方法、例えば、プレス成形、鋳込み成形、押出し成
形、射出成形、冷間静水圧成形などにより所望の形状に
成形する。The mixed powder thus obtained is molded into a desired shape by a known molding method such as press molding, cast molding, extrusion molding, injection molding or cold isostatic pressing.
【００２２】次に、得られた成形体を公知の焼成方法、
例えば、ホットプレス方法、常圧焼成、窒素ガス圧力焼
成、さらには、これらの焼成後のＨＩＰ焼成、および、
ガラスシ−ルＨＩＰ焼成等で焼成し、緻密な焼結体を得
る。この時の焼成温度は、１８５０℃以下、特に１６５
０〜１８００℃の低温にて焼成することができる。この
時の焼成温度が１８５０℃を越えると窒化珪素結晶が粒
成長し強度が低下する。なお、この時の雰囲気は、窒素
ガス含有非酸化性雰囲気である。Next, the obtained molded body is baked by a known method.
For example, hot pressing method, atmospheric pressure firing, nitrogen gas pressure firing, and further, HIP firing after these firing, and
It is fired by glass seal HIP firing or the like to obtain a dense sintered body. The firing temperature at this time is 1850 ° C. or less, particularly 165
It can be fired at a low temperature of 0 to 1800 ° C. If the firing temperature at this time exceeds 1850 ° C., the silicon nitride crystal grains grow and the strength decreases. The atmosphere at this time is a nitrogen gas-containing non-oxidizing atmosphere.
【００２３】次に、上記焼成終了後、冷却過程で一旦所
定の温度で保持して熱処理を施すか、または冷却後、焼
結体を非酸化性雰囲気で熱処理をする。この熱処理温度
は６００〜１５００℃、特に、８００〜１４００℃が望
ましい。この熱処理により珪素、希土類元素、アルミニ
ウム、リチウム、酸素、窒素からなる粒界相から、例え
ばＬｉＡｌＳｉＯ4 、ＬｉＡｌＳｉ2 Ｏ6 、ＬｉＲＥＳ
ｉＯ4 （ＲＥ：希土類元素）で表されるリチウムを含む
酸化物の結晶相を単独、または混在して析出させること
ができる。Next, after completion of the above-mentioned firing, heat treatment is performed by holding at a predetermined temperature once in the cooling process, or after cooling, the sintered body is heat treated in a non-oxidizing atmosphere. The heat treatment temperature is preferably 600 to 1500 ° C, particularly 800 to 1400 ° C. By this heat treatment, for example, LiAlSiO 4 , LiAlSi 2 O 6 , LiRES from the grain boundary phase composed of silicon, rare earth elements, aluminum, lithium, oxygen, and nitrogen.
A crystal phase of an oxide containing lithium represented by i0 4 (RE: rare earth element) can be precipitated alone or in combination.
【００２４】[0024]
【作用】窒化珪素質焼結体における窒化珪素結晶粒子
は、適当なアスペクト比と適当な大きさをもち、高信頼
性を得るためには異常粒成長粒子が存在しないことが必
要である。そのため、従来の希土類元素酸化物と酸化ア
ルミニウムのみの添加だけでは十分な異常粒成長の生成
の抑制ができないが、本発明に基づくと、これらの焼結
助剤に加え、酸化珪素およびリチウム化合物を添加する
ことにより、焼結過程で生成する液相の融点を低下させ
ることができるために窒化珪素粒の成長を抑制すること
ができ、微細な組織を形成することができる。The silicon nitride crystal grains in the silicon nitride sintered body have a proper aspect ratio and a proper size, and it is necessary that no abnormal grain growth grains exist in order to obtain high reliability. Therefore, it is not possible to sufficiently suppress the generation of abnormal grain growth only by adding the conventional rare earth element oxide and aluminum oxide, but according to the present invention, in addition to these sintering aids, silicon oxide and a lithium compound are added. By adding, the melting point of the liquid phase generated in the sintering process can be lowered, so that the growth of silicon nitride grains can be suppressed and a fine structure can be formed.
【００２５】また、窒化珪素結晶の粒界にリチウムを含
む結晶相を析出させることにより、それ自体の熱膨張率
が小さいことにより、冷却後、熱膨張差に基づく残留応
力が発生し破壊靱性を高めるとともに、残部の粒界相の
高温安定化が図られ、これにより焼結体の室温、特に高
温強度を高めることができる。Further, by precipitating a crystal phase containing lithium at the grain boundaries of the silicon nitride crystal, the coefficient of thermal expansion of itself is small, so that after cooling, residual stress is generated due to the difference in thermal expansion, and fracture toughness is improved. At the same time, the rest of the grain boundary phase is stabilized at high temperature, whereby the room temperature, especially the high temperature strength of the sintered body can be increased.
【００２６】[0026]
【実施例】原料粉末として窒化珪素粉末（ＢＥＴ比表面
積８ｍ2 ／ｇ、α率９８％、酸素量１．２モル％）と各
種の希土類酸化物粉末、酸化アルミニウム粉末、酸化珪
素粉末、炭酸リチウム粉末と酸化珪素粉末とから合成し
たＬｉ2 Ｓｉ2 Ｏ5 粉末を用いて、表１に示す組成にな
るように調合後、１ｔ／ｃｍ2 で金型成形した。EXAMPLES Silicon nitride powder (BET specific surface area 8 m 2 / g, α ratio 98%, oxygen amount 1.2 mol%) as raw material powder and various rare earth oxide powder, aluminum oxide powder, silicon oxide powder, lithium carbonate Li 2 Si 2 O 5 powder synthesized from the powder and the silicon oxide powder was used to prepare the composition shown in Table 1 and then mold-molded at 1 t / cm 2 .
【００２７】得られた成形体を炭化珪素質の匣鉢に入れ
て、カ−ボンヒ−タ−を用い、常圧にて窒素ガス気流
中、表１に示す条件で焼成し、一部の試料は表１に示す
条件で冷却中に熱処理を実施した。さらに一部の試料に
ついては常圧にて窒素ガス気流中表１に示す条件で熱処
理を実施し焼結体を得た。The obtained molded body was placed in a silicon carbide sagger and fired under a nitrogen gas stream at atmospheric pressure under the conditions shown in Table 1 using a carbon heater, and a part of the sample Was heat-treated during cooling under the conditions shown in Table 1. Further, some of the samples were heat-treated under normal pressure in a nitrogen gas stream under the conditions shown in Table 1 to obtain sintered bodies.
【００２８】得られた焼結体をＪＩＳ−Ｒ１６０１にて
指定されている形状まで研磨し試料を作製した。この試
料についてアルキメデス法に基づく比重測定、窒化珪素
結晶の平均粒子径（短径）およびその平均アスペクト比
を電子顕微鏡から測定し、ＪＩＳ−Ｒ１６０１に基づく
室温および１０００℃での４点曲げ抗折強度試験を実施
し、さらに破壊靱性の測定を行った。またＸ線回折測定
により焼結体中の結晶を同定した。結果は表２に示し
た。The obtained sintered body was ground to a shape specified in JIS-R1601 to prepare a sample. The specific gravity of this sample was measured by the Archimedes method, the average particle size (minor axis) of the silicon nitride crystal and its average aspect ratio were measured by an electron microscope, and the four-point bending bending strength at room temperature and 1000 ° C. according to JIS-R1601. The test was conducted and the fracture toughness was further measured. The crystal in the sintered body was identified by X-ray diffraction measurement. The results are shown in Table 2.
【００２９】[0029]
【表１】 [Table 1]
【００３０】[0030]
【表２】 [Table 2]
【００３１】表１および表２の結果によると、Ｌｉ化合
物を全く添加しなかった試料Ｎo.１２では１７００℃の
焼成温度では充分に緻密化せず、試料Ｎo.１と同様の組
成で焼成温度を１８００℃まで高めた試料Ｎo.３では、
緻密化は可能であるが窒化珪素の結晶の粒成長が生じ、
強度の劣化が生じた。According to the results shown in Tables 1 and 2, the sample No. 12 to which no Li compound was added did not sufficiently densify at the baking temperature of 1700 ° C., and the baking temperature was the same as that of the sample No. 1. In sample No. 3 in which the temperature was raised to 1800 ° C,
Although densification is possible, grain growth of silicon nitride crystals occurs,
The strength deteriorated.
【００３２】また、Ｌｉ化合物を添加してもＬｉを結晶
化しなかった試料Ｎo.２では高温強度が劣化した。Ｌｉ
化合物を添加し且つ結晶化を図ってもＬｉ化合物量（Ｌ
ｉ2 Ｏ換算量）が０．５モル％より少ない試料Ｎo.６で
は、強度向上の効果が不十分で、１０モル％を越える試
料Ｎo.９でも高温強度の劣化があった。Further, in sample No. 2 in which Li was not crystallized even when the Li compound was added, the high temperature strength deteriorated. Li
The amount of Li compound (L
Sample No. 6 having an i 2 O conversion amount) of less than 0.5 mol% had an insufficient effect of improving the strength, and sample No. 9 having more than 10 mol% also deteriorated the high temperature strength.
【００３３】さらに、窒化珪素を除く希土類元素酸化
物、酸化アルミニウム、Ｌｉ化合物の量の合計が４０モ
ル％を越える試料Ｎo.１３では高温強度の劣化が大き
く、６モル％より少ない試料Ｎo.１４では緻密化が達成
されなかった。Further, in sample No. 13 in which the total amount of rare earth element oxides other than silicon nitride, aluminum oxide, and Li compound exceeds 40 mol%, deterioration of high temperature strength is large, and in sample No. 14 less than 6 mol%. Then, densification was not achieved.
【００３４】これらの比較例に対し、本発明の焼結体
は、１７００℃における低温で充分に緻密化しており、
それにより平均粒径（短径）８μｍ以下の微細な組織を
呈し、特性的にもいずれも優れた抗折強度、破壊靱性を
示し、室温強度１１００ｋｇ／ｍｍ2 以上、１０００℃
強度８５０ｋｇ／ｍｍ2以上および靱性６ＭＰａ・ｍ1/
2 以上が達成された。In contrast to these comparative examples, the sintered body of the present invention is sufficiently densified at a low temperature of 1700 ° C.,
As a result, it exhibits a fine structure with an average grain size (minor axis) of 8 μm or less, and exhibits excellent bending strength and fracture toughness in terms of both characteristics, and room temperature strength of 1100 kg / mm 2 or more, 1000 ° C.
Strength 850 kg / mm 2 or more and toughness 6 MPa · m 1 /
2 or more was achieved.
【００３５】[0035]
【発明の効果】以上詳述した通り、本発明によれば、低
温における緻密化が可能であることにより窒化珪素結晶
の粒成長を抑制することができるとともに、室温および
高温における強度、靱性を向上することができる。As described in detail above, according to the present invention, since it is possible to densify at low temperature, grain growth of silicon nitride crystals can be suppressed, and strength and toughness at room temperature and high temperature are improved. can do.
Claims (2)
もリチウムを含む酸化物の結晶相と、少なくとも希土類
元素とアルミニウムを含む粒界相から構成されることを
特徴とする窒化珪素質焼結体。1. A silicon nitride sintered material comprising a main phase consisting of a silicon nitride crystal phase, an oxide crystal phase containing at least lithium, and a grain boundary phase containing at least a rare earth element and aluminum. body.
物、酸化アルミニウム、酸化珪素を合計で６〜４０モル
％、リチウム化合物をＬｉ2 Ｏ換算で０．５〜１０モル
％の割合で含有する混合物を成形後、１８００℃以下の
窒素を含む非酸化性雰囲気で焼結し、さらに６００〜１
５００℃の非酸化性雰囲気中で熱処理を施し、窒化珪素
結晶相と、少なくともリチウムを含む酸化物の結晶相お
よび少なくとも希土類元素とアルミニウムを含む粒界相
を生成させることを特徴とする窒化珪素質焼結体の製造
方法。2. A silicon nitride as a main component, a rare earth element oxide, aluminum oxide, and silicon oxide in a total amount of 6 to 40 mol%, and a lithium compound in a ratio of 0.5 to 10 mol% in terms of Li 2 O. After molding the mixture, the mixture is sintered in a non-oxidizing atmosphere containing nitrogen at 1800 ° C. or lower, and further 600 to 1
A silicon nitride material characterized by being subjected to heat treatment in a non-oxidizing atmosphere at 500 ° C. to produce a silicon nitride crystal phase, an oxide crystal phase containing at least lithium and a grain boundary phase containing at least a rare earth element and aluminum. Manufacturing method of sintered body.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3306100A JP3034100B2 (en) | 1991-11-21 | 1991-11-21 | Silicon nitride sintered body and method for producing the same |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3306100A JP3034100B2 (en) | 1991-11-21 | 1991-11-21 | Silicon nitride sintered body and method for producing the same |
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| Publication Number | Publication Date |
|---|---|
| JPH05139840A true JPH05139840A (en) | 1993-06-08 |
| JP3034100B2 JP3034100B2 (en) | 2000-04-17 |
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ID=17953042
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|---|---|---|---|
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Cited By (3)
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|---|---|---|---|---|
| JP2007321797A (en) * | 2006-05-30 | 2007-12-13 | Kyocera Corp | Sliding member and mechanical seal ring using the same |
| CN104894648A (en) * | 2015-05-19 | 2015-09-09 | 西安交通大学 | Preparation method of rod-like lithium disilicate crystal |
| CN115073186A (en) * | 2022-07-22 | 2022-09-20 | 中国科学院兰州化学物理研究所 | Silicon nitride ceramic sintered body and preparation method thereof |
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| JP6043232B2 (en) * | 2013-04-12 | 2016-12-14 | ダイコク電機株式会社 | Game system |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007321797A (en) * | 2006-05-30 | 2007-12-13 | Kyocera Corp | Sliding member and mechanical seal ring using the same |
| CN104894648A (en) * | 2015-05-19 | 2015-09-09 | 西安交通大学 | Preparation method of rod-like lithium disilicate crystal |
| CN104894648B (en) * | 2015-05-19 | 2017-09-12 | 西安交通大学 | A kind of preparation method of bar-shaped lithium bisilicate crystal |
| CN115073186A (en) * | 2022-07-22 | 2022-09-20 | 中国科学院兰州化学物理研究所 | Silicon nitride ceramic sintered body and preparation method thereof |
| US11807582B1 (en) | 2022-07-22 | 2023-11-07 | Lanzhou Institute Of Chemical Physics, Cas | Silicon nitride ceramic sintered body and preparation method thereof |
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| Publication number | Publication date |
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| JP3034100B2 (en) | 2000-04-17 |
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