JP2883234B2 - Silicon nitride sintered body - Google Patents

Silicon nitride sintered body

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Publication number
JP2883234B2
JP2883234B2 JP3312150A JP31215091A JP2883234B2 JP 2883234 B2 JP2883234 B2 JP 2883234B2 JP 3312150 A JP3312150 A JP 3312150A JP 31215091 A JP31215091 A JP 31215091A JP 2883234 B2 JP2883234 B2 JP 2883234B2
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JP
Japan
Prior art keywords
sintered body
silicon nitride
present
amount
weight
Prior art date
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Expired - Lifetime
Application number
JP3312150A
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Japanese (ja)
Other versions
JPH05148031A (en
Inventor
武廣 織田
祥二 高坂
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Kyocera Corp
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Kyocera Corp
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Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【産業上の利用分野】本発明は、高強度の窒化珪素質焼
結体に関するものであり、特に特性のばらつきを低減す
るための改良に関するものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength silicon nitride sintered body, and more particularly to an improvement for reducing variation in characteristics.

【0002】[0002]

【従来技術】窒化珪素質焼結体は、従来より高温強度に
優れた材料として各種のエンジニアリングセラミックス
として高温用材料等への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 various engineering ceramics as materials having excellent high-temperature strength as high-temperature materials.

【0003】かかる窒化珪素は、それ自体難焼結性であ
ることから、従来よりY2 3 などの周期律表第3a族
元素の酸化物やAl23 等の各種の金属酸化物を添加
し焼成することが行われている。
[0003] Since such silicon nitride itself is difficult to be sintered, oxides of Group 3a elements of the periodic table such as Y 2 O 3 and various metal oxides such as Al 2 O 3 have been conventionally used. Addition and firing are performed.

【0004】最近に至り、窒化珪素質焼結体の使用温度
が1400℃以上の高温域まで広がりつつあり、これに
伴い焼結体の高温特性の改善が望まれている。そこで、
高温特性が窒化珪素質焼結体の粒界の組成等やそれによ
る粒界の融点等により大きく変化するという観点から、
Al2 3 等の低融点物質の添加を抑制し、Y2 3
希土類元素の酸化物、あるいはこれに酸化珪素等を添加
した系の焼結体が提案され、さらに粒界相を結晶化させ
ることにより粒界の高融点化を図ることが提案されてい
る。
[0004] Recently, the operating temperature of a silicon nitride based sintered body has been expanding to a high temperature range of 1400 ° C or higher, and accordingly, improvement of the high temperature characteristics of the sintered body has been desired. Therefore,
From the viewpoint that the high-temperature characteristics greatly change due to the composition of the grain boundaries of the silicon nitride based sintered body and the melting point of the grain boundaries due to the composition,
A sintered body in which the addition of a low-melting substance such as Al 2 O 3 is suppressed and Y 2 O 3 or an oxide of a rare earth element or silicon oxide or the like is added thereto has been proposed. It has been proposed to increase the melting point of the grain boundary by changing the melting point.

【0005】[0005]

【発明は解決しようとする問題点】しかしながら、上記
の焼結体は、従来品に比較して抗折強度、耐酸化性につ
いては優れた特性を有するが、特性のばらつきがいまだ
解決されず、生産性において特性の安定した焼結体を得
ることが困難であるという欠点を有していた。
However, the above-mentioned sintered body has excellent characteristics in terms of bending strength and oxidation resistance as compared with conventional products, but the variation in characteristics has not been solved yet. There is a disadvantage that it is difficult to obtain a sintered body having stable characteristics in productivity.

【0006】そこで、このばらつきの原因について調査
を行ったところ、そのほとんどの破壊源の組織内に異常
組織が存在することがわかった。さらに、この異常組織
部分について分析したところ、鉄(Fe)が存在し、こ
れがケイ素(Si)と共晶反応を生じ、その周囲に添加
した希土類元素が過剰に集まったものであることを突き
止めた。
[0006] Then, when the cause of this variation was investigated, it was found that an abnormal tissue was present in most of the fracture sources. Further analysis of the abnormal structure revealed that iron (Fe) was present, which caused a eutectic reaction with silicon (Si), and that the rare earth elements added around the iron (Fe) were excessively collected. .

【0007】[0007]

【問題点を解決するための手段】本発明者等は、かかる
問題点に対して不純物としてのFeの悪影響を低減する
方法について詳細に検討したところ、かかる系に対して
Wを所定の割合で添加含有させることにより前記異常組
織の生成を顕著に低減できることにより、特性のばらつ
きが改善されることを見出し本発明に至った。
Means for Solving the Problems The present inventors have studied in detail a method for reducing the adverse effect of Fe as an impurity with respect to such problems, and found that W is contained at a predetermined ratio in such a system. The present inventors have found out that the addition and addition of the additive can significantly reduce the generation of the abnormal tissue, thereby improving the variation in characteristics, thereby leading to the present invention.

【0008】即ち、本発明の窒化珪素質焼結体は、窒化
珪素を主成分とし、Er、Y、Sc、Ce、Yb、D
y、Tb、Hoのうちの少なくとも1種の希土類元素酸
化物を0.5mol%〜10mol%、Feを重量比で
5ppm〜1000ppm、さらにWを酸化物換算で
0.01重量%〜2重量%の割合で含有することを特徴
とするものである。
That is, the silicon nitride sintered body of the present invention contains silicon nitride as a main component, and contains Er, Y, Sc, Ce, Yb, and D.
0.5 mol% to 10 mol% of at least one rare earth element oxide of y, Tb and Ho, 5 ppm to 1000 ppm of Fe by weight, and 0.01 wt% to 2 wt% of W in terms of oxide Is contained at a ratio of

【0009】以下、本発明を詳述する。本発明の焼結体
は、組成上、窒化珪素を主成分とし、さらに焼結助剤と
して少なくともYまたは希土類元素を0.5〜10mo
l%の含有するものであるが、純度の低い原料を用いた
り、あるいは製造過程において混合工程において系中に
Feが混入する場合がある。このFeは、その量が5p
pm以下と非常に少ない場合には、格別に焼結体の特性
に影響を及ぼすことはないが、その量が5ppm以上の
割合で混入すると、前述したように焼結体中に破壊源と
なる異常組織を形成し、これにより焼結体の特性を低下
させ、特性にばらつきを発生させる。
Hereinafter, the present invention will be described in detail. The sintered body of the present invention contains silicon nitride as a main component in composition, and further contains at least Y or a rare earth element as a sintering aid in an amount of 0.5 to 10 mol.
Although it contains 1%, there is a case where a raw material having low purity is used, or Fe is mixed in the system in the mixing step in the production process. This Fe has an amount of 5p
pm or less, it does not particularly affect the characteristics of the sintered body, but if the amount is mixed at a rate of 5 ppm or more, it becomes a source of destruction in the sintered body as described above. An abnormal structure is formed, thereby deteriorating the characteristics of the sintered body and causing variations in the characteristics.

【0010】本発明は、このようなFeを含有するよう
な系に対して、Wを金属換算で0.01〜2重量%、特
に0.05〜2重量%の割合で存在させることが重要で
ある。このWの存在により、Feの焼結体中での挙動を
固定化することができるものである。よってWの量が
0.01重量%より少ないと、異常組織の発生を抑制す
ることができず、特性のばらつきが大きくなり、Wの量
が2重量%を超えるとW自体が凝集し、これが破壊源と
なり、焼結体の強度を低下させる要因となる。
In the present invention, it is important that W is present in a system containing 0.01 to 2% by weight, particularly 0.05 to 2% by weight, in terms of metal, in such a system containing Fe. It is. Due to the presence of W, the behavior of Fe in the sintered body can be fixed. Therefore, if the amount of W is less than 0.01% by weight, the generation of an abnormal structure cannot be suppressed, and the variation in characteristics increases. If the amount of W exceeds 2% by weight, W itself aggregates, It becomes a source of destruction and causes a reduction in the strength of the sintered body.

【0011】このWの添加効果は、Fe量が多く成り過
ぎるとその効果が充分に発揮されず、Fe量が重量比で
1000ppmが上限値である。
The effect of adding W is not sufficiently exhibited when the amount of Fe is too large, and the upper limit of the amount of Fe is 1000 ppm by weight.

【0012】また、本発明の焼結体を製造する方法とし
ては、出発原料として窒化珪素粉末および焼結助剤とし
て少なくともYまたは希土類元素の例えば酸化物粉末を
用いる。また、本発明によれば、かかる系に対してWの
化合物をW金属換算で0.01〜2重量%の割合で添加
することが重要である。用いられるW化合物としては、
Wの酸化物、炭化物、珪化物等が挙げられる。
In the method for producing the sintered body of the present invention, a silicon nitride powder is used as a starting material, and at least a powder of an oxide of at least Y or a rare earth element is used as a sintering aid. According to the present invention, it is important to add a compound of W to such a system at a ratio of 0.01 to 2% by weight in terms of W metal. As the W compound used,
W oxides, carbides, silicides, and the like.

【0013】これらの出発原料は上記所定の割合で混合
した後、公知の方法で成形するが、Feは出発原料中に
含有される以外に、成形工程までの工程間で混入するこ
とも考えられる。本発明によれば、これらの混入量も考
慮し、最終成形体中でのFe量を金属換算で5〜200
0ppmに制御することが必要である。なお、成形手段
としてはプレス成形、押出成形、射出成形、鋳込み成
形、冷間静水圧成形等が挙げられる。
These starting materials are mixed at the above-mentioned predetermined ratio and then molded by a known method. In addition to being contained in the starting materials, Fe may be mixed during the steps up to the molding step. . According to the present invention, the amount of Fe in the final compact is 5 to 200 in terms of metal in consideration of the amount of these contaminants.
It is necessary to control to 0 ppm. As the molding means, press molding, extrusion molding, injection molding, casting molding, cold isostatic molding and the like can be mentioned.

【0014】次に成形体を常圧焼成、窒素ガス圧力焼
成、ホットプレス焼成等の焼成手段により、窒素等の非
酸化性雰囲気中で1600〜2000℃で焼成する。ま
た、特殊な焼成方法として熱間静水圧焼成法では、上記
の方法にて対理論密度比95%以上に緻密化した後、1
000〜2000気圧の窒素を含有する雰囲気中で16
00〜2000℃で焼成する方法、また前記成形体の表
面にBNを塗布した後、ガラス粉末をその表面に塗布し
たり、ガラス製カプセル内に封入するか、または内部に
ガラス粉末が充填された耐熱容器内に埋めた後、高温下
でガラスを溶融しガラスシールを形成した後、1000
〜2000気圧下で1600〜2000℃で焼成する方
法等が採用される。
Next, the molded body is fired at 1600 to 2000 ° C. in a non-oxidizing atmosphere such as nitrogen by firing means such as normal pressure firing, nitrogen gas pressure firing, and hot press firing. In the case of the hot isostatic firing method as a special firing method, after densification to a theoretical density ratio of 95% or more by the above method,
In an atmosphere containing 2,000 to 2,000 atmospheres of nitrogen.
A method of baking at 00 to 2000 ° C., or applying BN to the surface of the molded body, and then applying glass powder to the surface, enclosing the glass powder in a capsule, or filling the inside with glass powder. After filling in a heat-resistant container, the glass was melted at a high temperature to form a glass seal.
A method of baking at 1600 to 2000 ° C. under 20002000 atm is adopted.

【0015】なお、本発明において、上記Yまたは希土
類元素の酸化物換算量を0.5〜10mol%に限定し
たのは、0.5mol%より少ないと充分な緻密体が得
られず、10mol%を超えると高温強度等の機械的特
性が低下するためである。Yまたは希土類元素として
は、Y、Er、Sc、Ce、Yb、Dy、Tb、Hoの
うちの少なくとも1種を含む。
In the present invention, the amount of the Y or rare earth element in terms of oxide is limited to 0.5 to 10 mol%. If the amount is less than 0.5 mol%, a sufficient dense body cannot be obtained, This is because, if it exceeds 300, mechanical properties such as high-temperature strength deteriorate. Y or the rare earth element includes at least one of Y, Er, Sc, Ce, Yb, Dy, Tb, and Ho.

【0016】さらに、本発明によれば、上記系に対して
Al2 3 、MgO、CaO、AlN、ZrO2 、Si
2 等を10重量%以下の割合で添加しても何ら本発明
の効果に影響ないものであるが、これらのうち、Al2
3 、MgO、CaO等の低融点物質が存在するとFe
の存在による特性の劣化は顕著でないことから、本発明
の構成は、特にこれらの低融点物質が1重量%以下、特
に0.5重量%以下の組成系において効果的である。
Further, according to the present invention, Al 2 O 3 , MgO, CaO, AlN, ZrO 2 , Si
Be such as O 2 was added at a rate of 10 wt% or less but those not any effect to the effect of the present invention, among these, Al 2
When low-melting substances such as O 3 , MgO and CaO are present, Fe
The characteristics of the present invention are not significantly deteriorated, so that the constitution of the present invention is effective particularly in a composition system in which these low melting point substances are 1% by weight or less, particularly 0.5% by weight or less.

【0017】[0017]

【作用】本発明によれば、Feが系内に存在すると、焼
結過程において窒化珪素を分解し、発生したSiとの共
晶反応が生じる。このFe−Si共晶反応生成物の周囲
には、希土類元素が過剰に集まり、通常とは異なる異常
組織を形成する。
According to the present invention, when Fe is present in a system, silicon nitride is decomposed in a sintering process, and a eutectic reaction with generated Si occurs. Rare earth elements are excessively collected around the Fe-Si eutectic reaction product to form an unusual abnormal structure.

【0018】これらの挙動に対して、Wが存在すると、
Feの上記挙動が低減される。この理由は、定かではな
いが、Wが焼結過程において珪化物等の化合物を生成
し、この化合物内にFeが積極的に固溶されることによ
り、Fe元素が不活性状態となり、窒化珪素の分解が抑
制され、結果としてFe−Si共晶反応生成物の生成が
抑制されるためと考えられる。
For these behaviors, if W exists,
The above behavior of Fe is reduced. The reason for this is not clear, but W forms a compound such as silicide in the sintering process, and Fe is positively dissolved in this compound, so that the Fe element becomes inactive and silicon nitride is formed. It is considered that the decomposition of is suppressed, and as a result, the production of the Fe-Si eutectic reaction product is suppressed.

【0019】それにより、焼結体の破壊起点がFeの存
在による異常組織によるものから、常に焼結体表面とな
るために焼結体の特性が向上するとともにばらつきが低
減され、安定した特性を有する窒化珪素質焼結体を作製
することができる。
Thus, since the fracture starting point of the sintered body is caused by an abnormal structure due to the presence of Fe, the surface of the sintered body is always on the surface of the sintered body, so that the characteristics of the sintered body are improved, and the variation is reduced. A silicon nitride-based sintered body can be produced.

【0020】また、Wによる上記添加効果により比較的
低純度の安価な窒化珪素原料を用いた場合においても焼
結体特性の安定化を図ることができるために、焼結体の
コストの低減を図ることもできる。
Further, the characteristics of the sintered body can be stabilized even when an inexpensive silicon nitride raw material having relatively low purity is used due to the above-described addition effect of W, so that the cost of the sintered body can be reduced. You can also plan.

【0021】[0021]

【実施例】窒化珪素原料(酸素量1.0%、BET比表
面積10m2 /g、α率98%、Fe含有量30pp
m)と焼結助剤としてY2 3 、Yb2 3 、Sc2
3、Er2 3 、Ho2 3 、Dy2 3 、CeO2
Tb2 3 の各粉末を用いて、これらを表1に示す割合
で秤量後、ポリポットに入れ、メタノールを溶媒として
用い窒化珪素ボールにより72時間混合した。得られた
混合物を乾燥後、造粒し、80mm×45mm×5mm
にプレス成形した。得られた成形体に対して、Fe量を
ICP発光分光分析により測定した。そして、各成形体
を窒素ガス圧力10気圧の雰囲気中で表1の温度で焼成
した。なお、表中、試料No.16については表1の組成
からなる成形体の表面にBNを塗布しガラス浴中にて1
600℃の2000atmの圧力下で焼成した。
EXAMPLES Silicon nitride raw material (oxygen content 1.0%, BET specific surface area 10 m 2 / g, α rate 98%, Fe content 30 pp)
m) and Y 2 O 3 , Yb 2 O 3 , Sc 2 O as sintering aids
3, Er 2 O 3, Ho 2 O 3, Dy 2 O 3, CeO 2,
Each of the powders of Tb 2 O 3 was weighed at the ratios shown in Table 1 and then placed in a polypot and mixed with silicon nitride balls for 72 hours using methanol as a solvent. After drying the obtained mixture, it is granulated, and 80 mm × 45 mm × 5 mm
And press molded. The Fe amount of the obtained molded body was measured by ICP emission spectroscopy. Then, each compact was fired at a temperature shown in Table 1 in an atmosphere of a nitrogen gas pressure of 10 atm. In the table, for sample No. 16, BN was applied to the surface of a molded body having the composition shown in Table 1, and the sample was placed in a glass bath.
Firing was performed at 600 ° C. under a pressure of 2000 atm.

【0022】得られた焼結体に対して、元素分析したと
ころ、焼結後の組成は成形体の組成と実質的に変わらな
いことを確認した。また、この焼結体より試験片を20
個切り出し、JISR1601により室温における抗折
強度を測定しその平均値を調べた。さらにその抗折片の
破断面より、破壊源を調べ、破壊源が鉄による異常粒成
長であるものの個数を調べた。結果は表1に示した。
Elemental analysis of the obtained sintered body confirmed that the composition after sintering was not substantially different from the composition of the molded body. In addition, a test piece of 20
Each piece was cut out, the bending strength at room temperature was measured by JISR1601, and the average value was examined. Furthermore, the fracture source was examined from the fracture surface of the bent piece, and the number of fracture sources whose abnormal grain growth was caused by iron was examined. The results are shown in Table 1.

【0023】[0023]

【表1】 [Table 1]

【0024】表1から明らかなように、前記条件での製
造で、Fe含有量が数十ppmのレベルの不純物の混入
に対してWを全く添加しなかった試料No,1では、破壊
源の多くがFe−Siの異常組織によるもので、中には
強度が460MPaと非常に低いものもあった。
As is clear from Table 1, in the sample No. 1 in which W was not added at all under the above-mentioned conditions and the content of impurities of several tens of ppm was mixed in the production under the above conditions, the source of the destruction was Many are due to the abnormal structure of Fe-Si, and some of them have very low strength of 460 MPa.

【0025】これに対してW化合物を添加すると、0.
01重量%の添加により、試料No,2に示すように異常
組織により破壊する焼結体の割合が減少し、しかもWの
量を増加するに従い、その平均強度が回復し、特性のば
らつきが改善されることが理解できる。しかしながら、
Wの量が2重量%を越える試料No,10ではWによる凝
集が観察され、これにより強度が劣化した。
On the other hand, when a W compound is added, 0.1% is obtained.
With the addition of 01% by weight, as shown in Sample No. 2, the ratio of the sintered body broken by the abnormal structure decreases, and as the amount of W increases, the average strength recovers and the dispersion of characteristics improves. It can be understood that it is done. However,
In Sample No. 10 in which the amount of W exceeds 2% by weight, agglomeration due to W was observed, thereby deteriorating the strength.

【0026】また、Wの添加効果を確認するために系中
にFeを添加してFe量を増加させた系に対して評価し
たところ、Fe量が1000ppmを超える試料No.7
〜9ではW添加効果が小さくなり、試料No.9では強度
の低下も見られた。
In order to confirm the effect of adding W, an evaluation was made on a system in which Fe was added to the system to increase the amount of Fe.
In samples No. 9 to 9, the effect of adding W was reduced, and in Sample No. 9, a decrease in strength was also observed.

【0027】さらに、焼結体中のY2 3 の添加量を変
化させたところ、添加量が0.5モル%より少ない試料
No,11では十分に緻密化が達成されず、10モル%を
越えると強度の劣化が認められた。
Further, when the addition amount of Y 2 O 3 in the sintered body was changed, the densification was not sufficiently achieved in the sample No. 11 in which the addition amount was less than 0.5 mol%, and 10 mol% was not achieved. When the ratio exceeded, deterioration in strength was observed.

【0028】なお、焼成条件を熱間静水圧焼成法にて行
っても本発明の効果が認められ、さらにW化合物として
WO3 以外のWSi2 やWCを用いても、さらにはその
他の希土類元素においても同様な効果が認められた。
The effect of the present invention can be obtained even when the firing conditions are hot isostatic pressing. Even when WSi 2 or WC other than WO 3 is used as the W compound, other rare earth elements can be used. A similar effect was also observed.

【0029】[0029]

【発明の効果】以上詳述した通り、本発明によれば、F
eを含む系に対してWを添加することによりFeによる
異常組織の生成を抑制することにより異常組織による破
壊を低減し、高強度で特性のばらつきのない焼結体を作
製することができる。
As described above in detail, according to the present invention, F
By adding W to the system containing e, the generation of an abnormal structure due to Fe is suppressed to reduce the destruction due to the abnormal structure, and a sintered body having high strength and no variation in characteristics can be manufactured.

Claims (1)

(57)【特許請求の範囲】(57) [Claims] 【請求項1】窒化珪素を主成分とし、Er、Y、Sc、
Ce、Yb、Dy、Tb、Hoのうちの少なくとも1種
の希土類元素酸化物を0.5mol%〜10mol%、
Feを重量比で5ppm〜1000ppm、さらにWを
酸化物換算で0.01重量%〜2重量%の割合で含有す
ることを特徴とする窒化珪素質焼結体。
1. A method according to claim 1, wherein the main component is silicon nitride, and Er, Y, Sc,
0.5 mol% to 10 mol% of at least one rare earth element oxide of Ce, Yb, Dy, Tb and Ho;
A silicon nitride-based sintered body containing Fe in a weight ratio of 5 ppm to 1000 ppm and W in an amount of 0.01% by weight to 2% by weight in terms of oxide.
JP3312150A 1991-11-27 1991-11-27 Silicon nitride sintered body Expired - Lifetime JP2883234B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP3312150A JP2883234B2 (en) 1991-11-27 1991-11-27 Silicon nitride sintered body

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP3312150A JP2883234B2 (en) 1991-11-27 1991-11-27 Silicon nitride sintered body

Publications (2)

Publication Number Publication Date
JPH05148031A JPH05148031A (en) 1993-06-15
JP2883234B2 true JP2883234B2 (en) 1999-04-19

Family

ID=18025852

Family Applications (1)

Application Number Title Priority Date Filing Date
JP3312150A Expired - Lifetime JP2883234B2 (en) 1991-11-27 1991-11-27 Silicon nitride sintered body

Country Status (1)

Country Link
JP (1) JP2883234B2 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4717635B2 (en) * 2003-08-26 2011-07-06 京セラ株式会社 Silicon nitride-based sintered body, method for producing the same, member for molten metal using the same, and member for wear resistance

Also Published As

Publication number Publication date
JPH05148031A (en) 1993-06-15

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