JP3034099B2 - Silicon nitride sintered body and method for producing the same - Google Patents
Silicon nitride sintered body and method for producing the sameInfo
- Publication number
- JP3034099B2 JP3034099B2 JP3306099A JP30609991A JP3034099B2 JP 3034099 B2 JP3034099 B2 JP 3034099B2 JP 3306099 A JP3306099 A JP 3306099A JP 30609991 A JP30609991 A JP 30609991A JP 3034099 B2 JP3034099 B2 JP 3034099B2
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- silicon nitride
- rare earth
- sintered body
- oxide
- earth element
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、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 relates to a silicon nitride sintered body having excellent strength characteristics from room temperature to a high temperature and particularly used for parts for automobiles and parts for gas turbine engines, and a method for producing the same.
【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-based sintered bodies have been applied to engineering ceramics, especially for heat engines such as tarbor heaters because of their excellent heat resistance, thermal shock resistance and oxidation resistance. 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。[0003] Since such silicon nitride itself is difficult to sinter, a rare earth oxide such as Y 2 O 3 is used as a sintering aid in order to produce a sintered body having higher density and higher strength than before. And Japanese Patent Publication No. 52-364.
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, the grain boundary component of the silicon nitride crystal is crystallized systematically, for example, Si 3 N 4 —RE 2 O 3 (R
A proposal has been made to increase the strength at high temperatures by forming a high melting point crystalline phase of E: rare earth element-SiO 2 system.
【０００５】[0005]
【発明が解決しようとする問題点】上記の焼結助剤にお
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、酸化アル
ミニウム等の低融点物質が存在すると焼結体の粒界が低
融点化されるために、１４００℃程度の高温における強
度が低下するという問題がある。It is known that when yttrium oxide and aluminum oxide are used in combination in the above sintering aid, the sinterability is greatly improved, and high density can be achieved by firing at a relatively low temperature. However, the presence of a low-melting substance such as aluminum oxide lowers the melting point of the grain boundary of the sintered body, which causes a problem that the strength at a high temperature of about 1400 ° C. decreases.
【０００６】また、Ａｌ2 Ｏ3 等の低融点酸化物を添加
せずに粒界にＳｉ3 Ｎ4 −ＲＥ2 Ｏ3 （ＲＥ：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、高温強度に対してはある程度優れた特性を示す
ことが知られているが、系全体の焼結性が悪いために１
９００℃を越える高温での焼成を必要とし、そのために
焼結体の主結晶相である窒化珪素結晶が粒成長しこれに
より室温強度が劣化するなどの問題があった。Further, a high melting point crystalline phase of Si 3 N 4 —RE 2 O 3 (RE: rare earth element) —SiO 2 system is precipitated at the grain boundaries without adding a low melting point oxide such as Al 2 O 3. According to this method, it is known that the material exhibits some excellent properties with respect to the high-temperature strength, but the sinterability of the entire system is poor.
Firing at a high temperature exceeding 900 ° C. is required, which causes a problem that silicon nitride crystals, which are the main crystal phase of the sintered body, grow and thereby deteriorate the strength at room temperature.
【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１４
００℃の高温までの抗折強度に優れるとともに、１８５
０℃以下の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。Accordingly, the present invention is intended to provide strength characteristics sufficient from room temperature to high temperature in a temperature range used for parts for automobiles, parts for gas turbine engines, etc.
Excellent flexural strength up to high temperature of 00 ° C and 185
It is an object of the present invention to provide a silicon nitride-based sintered body that can be fired at a low temperature of 0 ° C. or less 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、酸化珪素を添加した系に対してリチウム
化合物を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
ムおよび希土類元素を含む複合酸化物よりなる結晶相を
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。Means for Solving the Problems In order to enhance the strength characteristics of the sintered body, the present inventor has proposed that the composition of the sintered body, the shape of the silicon nitride crystal phase in the sintered body, the shape of the silicon nitride phase, and the like. As a result of repeated studies based on the view that it is important to control the subphase present at the grain boundaries, a lithium compound was added to a system in which silicon nitride was the main component and rare earth element oxides and silicon oxide were added. The addition improves the sinterability of the system and enables firing at low temperatures, and is excellent from room temperature to high temperatures by precipitating a crystal phase consisting of a composite oxide containing lithium and rare earth elements in the sintered body. The present inventors have found that a sintered body having improved strength characteristics can be obtained, and have reached the present invention.
【０００９】即ち、本発明は、窒化珪素を主成分とし、
希土類元素酸化物０．５〜１０モル％、酸化珪素２０モ
ル％以下、さらにリチウム化合物（Ｌｉ2 Ｏ換算）０．
５〜１０モル％の割合で添加し、且つＡｌ2 Ｏ3 および
ＭｇＯの低融点酸化物が０．５重量％以下の混合物を成
形後、１８５０℃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、さらに焼成終了後に
８００〜１４００℃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と
希土類元素を含む複合酸化物よりなる結晶相を生成させ
ることにより特性の改善を図ったものである。That is, the present invention comprises silicon nitride as a main component,
0.5 to 10 mol% of rare earth element oxide, 20 mol% or less of silicon oxide, and lithium compound (in terms of Li 2 O) 0.1.
After adding a mixture of 5 to 10 mol% and a low melting point oxide of Al 2 O 3 and MgO of 0.5% by weight or less, the mixture is sufficiently formed in a non-oxidizing atmosphere containing nitrogen at 1850 ° C. or less. It can be sintered, and is further subjected to a heat treatment in a non-oxidizing atmosphere at a temperature of 800 to 1400 ° C. after completion of the firing, so that a silicon nitride crystal phase and a crystal phase composed of a composite oxide containing at least lithium and a rare earth element are obtained. To improve the characteristics.
【００１０】以下、本発明を詳述する。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、リチウムおよび酸素より構成され
るものである。Hereinafter, the present invention will be described in detail. The silicon nitride sintered body of the present invention contains silicon nitride as a main component, and as an additional component, a rare earth element, lithium, and oxygen.
【００１１】ここで、焼結体中の酸素は、通常、希土類
元素、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、
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, oxygen in the sintered body is usually combined with rare earth elements and lithium, but excessive oxygen exists in the sintered body in addition to the oxygen. Such excess oxygen is calculated based on the total amount of oxygen in the sintered body, the rare earth element in the sintered body,
When the lithium element stoichiometrically forms an oxide, it is the remaining oxygen amount excluding oxygen bonded to each element, most of which is contained in the silicon nitride raw material, or
It is mixed as addition of SiO 2 or the like, and is considered as present as all SiO 2 in the present invention.
【００１２】本発明の焼結体は、窒化珪素結晶相を主相
とするものであり、そのほとんどはβ−Ｓｉ3 Ｎ4 から
なる。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 phase, and most of it is composed of β-Si 3 N 4 . This main phase generally has a columnar shape, but preferably has an average particle diameter (short diameter) of 1.5 μm or less and an aspect ratio of 2 to 15 from the viewpoint of improving strength and toughness.
【００１３】また、本発明によれば、上記の結晶相の他
に少なくともリチウムと希土類元素を含む結晶質の粒界
相が存在することが重要である。この結晶相は例えば、
ＬｉＲＥＳｉＯ4 で表される結晶相として存在する。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、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。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、さらに、熱処
理を施すことにより粒界相から析出し高温強度を高める
ことができる。According to the present invention, it is important that a crystalline grain boundary phase containing at least lithium and a rare earth element be present in addition to the above-mentioned crystal phase. This crystalline phase is, for example,
It exists as a crystal phase represented by LiRESiO 4 . This crystal phase exists as a liquid phase in the sintering process, enhances sinterability, enables low-temperature sintering, and suppresses abnormal grain growth of the silicon nitride crystal phase. If the glass phase remains as it is in the grain boundary phase, the high-temperature strength is reduced. Therefore, by performing heat treatment, the high-temperature strength can be increased by precipitation from the grain boundary phase.
【００１４】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。The rare earth element used in the present invention is Y
And lanthanoid elements such as Yb, Er, Dy, and Ho.
【００１５】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、Ｌｉ2 ＣＯ3 、ＬｉＹＯ4 、Ｌｉ2 ＳｉＯ3 、Ｌｉ
2 Ｓｉ2 Ｏ5 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Ｓｉや希
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-based sintered body of the present invention, silicon nitride powder, rare earth oxide powder, lithium compound powder, and, if necessary, silicon oxide powder are used as raw material powders. As the lithium compound, for example, Li 2 CO 3 , LiYO 4 , Li 2 SiO 3 , Li
Although 2 Si 2 O 5 and the like can be mentioned, Li 2 CO 3 is chemically unstable and has a low melting point, so it is desirable to use a composite oxide powder with other Si, a rare earth element, or the like.
【００１６】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 diameter of the silicon nitride powder is desirably 0.4 to 1.2 μm.
【００１７】これらは、希土類元素酸化物０．５〜１０
モル％、酸化珪素２０モル％以下およびリチウム化合物
をＬｉ2 Ｏ換算で０．５〜１０モル％の割合で窒化珪素
粉末に対して混合する。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Ｌ
ｉ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、希土類元素酸化物が
０．５モル％より少ないと焼結が不十分となり強度等の
特性が劣化し、１０モル％より多いと、粒界相自体の量
が増大することにより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％より少ないと焼結性が不
十分となり強度等の特性が劣化し、１０モル％より多い
と焼結体中の粒界相自体の量が増大し高温強度の劣化を
生じるためである。These are rare earth element oxides of 0.5 to 10
Mole%, mixed with respect to silicon nitride powder in a proportion of 0.5 to 10 mol% of silicon oxide 20 mol% or less and a lithium compound Li 2 O conversion. Here, silicon oxide is obtained by converting the amount of impurity oxygen contained in the silicon nitride raw material into SiO 2 and L
It includes the SiO 2 component in the i-compound. When these amounts are limited to the above ranges, if the amount of the rare earth element oxide is less than 0.5 mol%, sintering becomes insufficient and properties such as strength are deteriorated. The mechanical properties become insufficient due to the increase in the amount of itself. If the amount of the lithium compound is less than 0.5 mol%, the sinterability becomes insufficient and properties such as strength are deteriorated. If the amount is more than 10 mol%, the amount of the grain boundary phase itself in the sintered body increases, and the high temperature strength is increased. This is because of the deterioration.
【００１８】なお、本発明によれば、高温特性を高める
ためには、Ａｌ2 Ｏ3 、ＭｇＯ等の低融点酸化物を０．
５重量％以下に制御することが望ましく、０．５重量％
を越えると粒界相に低融点物質が生成されやすく成るた
めに１４００℃の強度が低下しやすくなる。According to the present invention, a low melting point oxide such as Al 2 O 3 or MgO is used in order to improve the high temperature characteristics.
It is desirable to control it to 5% by weight or less, and 0.5% by weight.
If the temperature exceeds the above range, a low melting point substance is easily generated in the grain boundary phase, so that the strength at 1400 ° C. tends to decrease.
【００１９】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 formed into a desired shape by a known molding method, for example, press molding, casting molding, extrusion molding, injection molding, cold isostatic pressing and the like.
【００２０】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１８０
０〜１６５０℃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。Next, the obtained molded body is fired by a known firing method,
For example, firing is performed by a hot pressing method, normal pressure firing, nitrogen gas pressure firing, HIP firing after firing, and glass seal HIP firing to obtain a dense sintered body. The firing temperature at this time is 1850 ° C. or less, particularly 180 ° C.
It can be fired at a low temperature of 0 to 1650 ° C. If the firing temperature at this time exceeds 1850 ° C., silicon nitride crystal grains grow and the strength decreases.
【００２１】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。The atmosphere at this time is a non-oxidizing atmosphere containing nitrogen gas.
【００２２】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する。この熱処理温度は
８００〜１４００℃がよい。この熱処理により珪素、希
土類元素、リチウム、酸素、窒素からなる粒界相から、
少なくともリチウムと希土類元素を含む結晶相、具体的
にはＬｉＲＥＳｉＯ4 （ＲＥ：希土類元素）で表される
結晶相を析出させることができる。これにより焼結体の
室温および１４００℃の高温強度を高めることができ
る。Next, after the completion of the sintering, a heat treatment is performed while maintaining the temperature at a predetermined temperature once in a cooling process, or the sintered body is heat-treated in a non-oxidizing atmosphere after cooling. This heat treatment temperature is preferably 800 to 1400 ° C. By this heat treatment, from the grain boundary phase consisting of silicon, rare earth element, lithium, oxygen and nitrogen,
A crystal phase containing at least lithium and a rare earth element, specifically, a crystal phase represented by LiRESiO 4 (RE: rare earth element) can be precipitated. Thereby, the strength of the sintered body at room temperature and at a high temperature of 1400 ° C. can be increased.
【００２３】[0023]
【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珪
素を添加した系では、焼成温度を高くする必要があるた
めに窒化珪素の粒成長を抑制することが困難である。し
かしながら、本発明に基づくと、これらの焼結助剤に加
え、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 an appropriate aspect ratio and an appropriate size, and in order to obtain high reliability, it is necessary that no abnormal grain growth particles exist. Therefore, in a conventional system in which a rare earth element oxide and silicon oxide are added, it is difficult to suppress the grain growth of silicon nitride because the firing temperature must be increased. However, according to the present invention, the addition of a lithium compound in addition to these sintering aids can reduce the melting point of the liquid phase generated during the sintering process, thereby suppressing the growth of silicon nitride grains. And a fine structure can be formed.
【００２４】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, since a crystal phase containing lithium is precipitated at the grain boundaries of the silicon nitride crystal, the coefficient of thermal expansion of the crystal itself is small, so that after cooling, residual stress based on the difference in thermal expansion is generated and the fracture toughness is reduced. At the same time, the remaining grain boundary phase is stabilized at a high temperature, and thereby the room temperature, particularly the high temperature strength of the sintered body can be increased.
【００２５】[0025]
【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重量％）と各
種の希土類酸化物粉末、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 ＳｉＯ3 粉末を
用いて、表１に示す組成になるように調合後、１ｔ／ｃ
ｍ2 で金型成形した。EXAMPLES As raw material powders, silicon nitride powder (BET specific surface area 8 m 2 / g, α rate 98%, oxygen content 1.2% by weight), various rare earth oxide powders, silicon oxide powder, lithium carbonate powder and silicon oxide After mixing with Li 2 SiO 3 powder synthesized from the powder to obtain the composition shown in Table 1, 1 t / c
Molding was performed with m 2 .
【００２６】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、窒素ガス気流中、表１に
示す条件で焼成した。また、試料Ｎo.２については焼成
後の冷却過程で表１の条件で熱処理を行った。その他の
試料については焼成後、一旦冷却した後に常圧にて窒素
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 compact was placed in a silicon carbide sagger and fired in a nitrogen gas stream under the conditions shown in Table 1 using a carbon heater. Sample No. 2 was heat-treated under the conditions shown in Table 1 during the cooling process after firing. The other samples were fired, cooled once, and then heat-treated at normal pressure in a nitrogen gas stream under the conditions shown in Table 1 to obtain a sintered body.
【００２７】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 polished to a shape specified by JIS-R1601, to prepare a sample. The specific gravity of this sample was measured based on the Archimedes method, the average particle diameter (short diameter) of the silicon nitride crystal and its average aspect ratio were measured with an electron microscope, and the four-point bending strength at room temperature and 1000 ° C. according to JIS-R1601. The test was performed. Further, crystals in the sintered body were identified by X-ray diffraction measurement. The results are shown in Table 2.
【００２８】[0028]
【表１】 [Table 1]
【００２９】[0029]
【表２】 [Table 2]
【００３０】表１および表２の結果によると、１７５０
℃での焼成ではＬｉ化合物を添加しなかったＮo.１は緻
密化不足で強度も低下していた。試料Ｎo.１において焼
成温度を１８５０℃まで上昇させた試料Ｎo.８では緻密
化したが、窒化珪素の粒成長が起こり、強度が低下して
いた。Ｌｉ化合物を添加しても、熱処理を施さなかった
試料Ｎo.７では窒化珪素以外に結晶相がなく、高温強度
が低下していた。According to the results of Tables 1 and 2, 1750
No. 1 to which the Li compound was not added at the sintering at ℃, the strength was lowered due to insufficient densification. Sample No. 8 in which the firing temperature was raised to 1850 ° C. in Sample No. 1 was densified, but the grain growth of silicon nitride occurred and the strength was reduced. Sample No. 7, which was not heat-treated even when the Li compound was added, had no crystal phase other than silicon nitride, and the high-temperature strength was low.
【００３１】また、希土類元素酸化物の量が０．５モル
％より低い試料Ｎo.１３では焼結不良が生じた。さら
に、Ｌｉ化合物の量が０．５モル％より少ない試料Ｎo.
１４では試料Ｎo.１と同様な結果でＬｉ化合物の添加効
果がなく、１０モル％を超える試料Ｎo.１５では緻密化
は達成されたが強度が低いものであった。Sample No. 13 in which the amount of the rare earth element oxide was lower than 0.5 mol% resulted in poor sintering. Further, the sample No. having an amount of the Li compound of less than 0.5 mol%.
In Sample No. 14, the same effect as in Sample No. 1 was obtained, and there was no effect of adding the Li compound. In Sample No. 15 exceeding 10 mol%, densification was achieved but the strength was low.
【００３２】これらの比較例に対し、本発明の焼結体は
いずれも１７５０℃において高い緻密性を有するととも
に窒化珪素の平均粒径が１μｍ以下の微細な針状粒子よ
りなるもので、室温および高温において優れた強度を示
した。In contrast to these comparative examples, the sintered bodies of the present invention all have high densities at 1750 ° C. and consist of fine needle-like particles having an average particle diameter of silicon nitride of 1 μm or less. Excellent strength at high temperature.
【００３３】[0033]
【発明の効果】以上詳述した通り、本発明によれば、低
温焼成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ことにより、室温
および高温における強度を向上することができる。As described in detail above, according to the present invention, the densification at low-temperature firing is possible, so that the grain growth of silicon nitride crystals can be suppressed, thereby improving the strength at room temperature and high temperature. be able to.
Claims (3)
を０．５〜１０モル％、酸化珪素を２０モル％以下、リ
チウム化合物をＬｉ2 Ｏ換算で０．５〜１０モル％の割
合で含み、Ａｌ2 Ｏ3 およびＭｇＯの低融点酸化物が
０．５重量％以下であり、窒化珪素結晶相からなる主相
の粒界に、少なくともリチウムと希土類元素を含む複合
酸化物よりなる結晶相が存在することを特徴とする窒化
珪素質焼結体。1. A composition containing silicon nitride as a main component, a rare earth element oxide of 0.5 to 10 mol%, a silicon oxide of 20 mol% or less, and a lithium compound of 0.5 to 10 mol% in terms of Li 2 O. Wherein the low-melting oxide of Al 2 O 3 and MgO is 0.5% by weight or less, and a crystal composed of a composite oxide containing at least lithium and a rare earth element is formed at a grain boundary of a main phase composed of a silicon nitride crystal phase. A silicon nitride based sintered body characterized in that a phase exists.
ｉＲＥＳｉＯ4 （ＲＥは希土類元素）であることを特徴
とする請求項１記載の窒化珪素質焼結体。2. A crystalline phase containing lithium and a rare earth element is L
2. The silicon nitride sintered body according to claim 1, wherein iRESiO 4 (RE is a rare earth element).
を０．５〜１０モル％、酸化珪素を２０モル％以下、リ
チウム化合物をＬｉ2 Ｏ換算で０．５〜１０モル％の割
合からなり、Ａｌ2 Ｏ3 およびＭｇＯの低融点酸化物が
０．５重量％以下の混合物を成形後、１８５０℃以下の
窒素を含む非酸化性雰囲気で焼結して焼成終了後、８０
０〜１４００℃の非酸化性雰囲気中で熱処理を施し、窒
化珪素結晶相を主相とし、該主相の粒界に少なくともリ
チウムと希土類元素を含む複合酸化物よりなる結晶相を
生成させたことを特徴とする窒化珪素質焼結体の製造方
法。3. A composition containing silicon nitride as a main component, a rare earth element oxide of 0.5 to 10 mol%, a silicon oxide of 20 mol% or less, and a lithium compound of 0.5 to 10 mol% in terms of Li 2 O. After shaping a mixture containing 0.5% by weight or less of low-melting oxides of Al 2 O 3 and MgO, sintering in a non-oxidizing atmosphere containing nitrogen at 1850 ° C. or less, and after sintering,
Heat-treating in a non-oxidizing atmosphere at 0 to 1400 ° C. to form a crystal phase composed of a composite oxide containing at least lithium and a rare earth element at a grain boundary of the silicon nitride crystal phase as a main phase. A method for producing a silicon nitride-based sintered body, characterized in that:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3306099A JP3034099B2 (en) | 1991-11-21 | 1991-11-21 | Silicon nitride sintered body and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3306099A JP3034099B2 (en) | 1991-11-21 | 1991-11-21 | Silicon nitride sintered body and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05139838A JPH05139838A (en) | 1993-06-08 |
| JP3034099B2 true JP3034099B2 (en) | 2000-04-17 |
Family
ID=17953029
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3306099A Expired - Fee Related JP3034099B2 (en) | 1991-11-21 | 1991-11-21 | Silicon nitride sintered body and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3034099B2 (en) |
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| CN110590377B (en) * | 2019-10-29 | 2020-11-13 | 中钢集团洛阳耐火材料研究院有限公司 | High beta-phase compact silicon nitride ceramic and low-temperature preparation method |
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1991
- 1991-11-21 JP JP3306099A patent/JP3034099B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05139838A (en) | 1993-06-08 |
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