JPH0859350A - Silicon nitride sintered compact and its production - Google Patents
Silicon nitride sintered compact and its productionInfo
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- JPH0859350A JPH0859350A JP6194158A JP19415894A JPH0859350A JP H0859350 A JPH0859350 A JP H0859350A JP 6194158 A JP6194158 A JP 6194158A JP 19415894 A JP19415894 A JP 19415894A JP H0859350 A JPH0859350 A JP H0859350A
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- silicon nitride
- powder
- ytterbium
- temperature
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は高温高強度、耐酸化性、
耐摩耗性等が要求される機械部品に用いる窒化珪素質焼
結体とその製造方法に関する。FIELD OF THE INVENTION The present invention relates to high temperature and high strength, oxidation resistance,
The present invention relates to a silicon nitride-based sintered body used for a machine part that requires wear resistance and the like, and a method for manufacturing the same.
【０００２】[0002]
【従来の技術】窒化珪素焼結体は難焼結体であるため、
焼結助剤として酸化アルミニウム、酸化イットリウム等
を添加して焼結する方法が用いられているが、これらの
助剤成分は焼結後にガラス相として粒界に残り、このガ
ラス相が高温で軟化することにより高温特性を低下させ
ることが知られている。高温強度向上のためには助剤の
絶対量を減少させ、ホットプレスあるいはＨＩＰ等の特
殊な方法で強制的に焼結することが行われているが、耐
酸化性等について効果的な対策はほとんど行われてな
い。2. Description of the Related Art Since a silicon nitride sintered body is a difficult sintered body,
A method of sintering by adding aluminum oxide, yttrium oxide, etc. as a sintering aid is used, but these auxiliary components remain at the grain boundaries as a glass phase after sintering, and this glass phase softens at high temperature. It is known that by doing so, the high temperature characteristics are degraded. In order to improve the high temperature strength, the absolute amount of the auxiliary agent is reduced, and forcible sintering is performed by a special method such as hot pressing or HIP, but effective measures for oxidation resistance are Hardly ever done.
【０００３】[0003]
【発明が解決しようとする課題】本発明は焼結助剤とし
て、酸化イッテルビウム、酸化アルミニウム及び／又は
酸化珪素の混合系を使用し、その量、組成比の適正化を
図り、かつ焼結後に適正な加熱処理を行うことによって
通常の常圧焼結であっても緻密に焼結し、かつ高温強
度、耐酸化性等の高温特性の低下の少ない窒化珪素焼結
体とその製造方法を提供しようとするものである。The present invention uses, as a sintering aid, a mixed system of ytterbium oxide, aluminum oxide and / or silicon oxide, and optimizes the amount and composition ratio thereof, and after sintering Provided is a silicon nitride sintered body, which can be densely sintered even by normal pressureless sintering by performing appropriate heat treatment, and has little deterioration in high temperature characteristics such as high temperature strength and oxidation resistance, and a manufacturing method thereof. Is what you are trying to do.
【０００４】[0004]
【課題を解決するための手段】本発明は （１）窒化珪素を７０〜９７重量％、酸化イッテルビウ
ムを２〜３０重量％、酸化アルミニウムを０．１〜５．
０重量％及び酸化アルミニウムに対する酸化イッテルビ
ウムの重量比が１０以上の組成で、かつ焼結体中の窒化
珪素粒子の間隙である粒界部が安定な結晶相であるイッ
テルビウムシリコンオキシナイトライドの微結晶で構成
されてなることを特徴とする窒化珪素質焼結体。 （２）窒化珪素粉末を７０〜９７重量％、酸化イッテル
ビウム粉末を２〜３０重量％、酸化アルミニウム粉末を
０．１〜５．０重量％及び酸化アルミニウム粉末に対す
る酸化イッテルビウム粉末の重量比が１０以上よりなる
混合粉体を成型し、窒素ガス雰囲気中で１７００〜２１
００℃で焼成した後、９００〜９４０℃の範囲まで２０
℃毎分以上で降温し、５分以上保持した後、再び１１５
０〜１３５０℃の範囲に昇温し、４〜８時間の範囲で保
持することを特徴とする窒化珪素質焼結体の製造方法。 （３）窒化珪素を７０〜９７重量％、酸化イッテルビウ
ムを２〜３０重量％及び酸化珪素を０．５〜９．５重量
％で、かつ焼結体中の窒化珪素粒子の間隙である粒界部
が安定な結晶相であるイッテルビウムシリコンオキサイ
ドの微結晶で構成されてなることを特徴とする窒化珪素
質焼結体。 （４）窒化珪素粉末を７０〜９７重量％、酸化イッテル
ビウム粉末を２〜３０重量％及び酸化珪素粉末を０．５
〜９．５重量％よりなる混合粉体を成型し、窒素ガス雰
囲気中で１７００〜２１００℃で焼成した後、９００〜
９４０℃の範囲まで２０℃毎分以上で降温し、５分以上
保持した後、再び１１５０〜１３５０℃の範囲に昇温
し、４〜８時間の範囲で保持することを特徴とする窒化
珪素質焼結体の製造方法。 （５）窒化珪素を７０〜９７重量％、酸化イッテルビウ
ムを２〜３０重量％、酸化アルミニウムを０．１〜５．
０重量％、酸化アルミニウムに対する酸化イッテルビウ
ムの重量比が１０以上及び酸化珪素を０．５〜９．５重
量％の組成で、かつ焼結体中の窒化珪素粒子の間隙であ
る粒界部が安定な結晶相であるイッテルビウムシリコン
オキシナイトライド及びイッテルビウムシリコンオキサ
イドの微結晶で構成されてなることを特徴とする窒化珪
素質焼結体。 （６）窒化珪素粉末を７０〜９７重量％、酸化イッテル
ビウム粉末を２〜３０重量％、酸化アルミニウム粉末を
０．１〜５．０重量％、酸化アルミニウム粉末に対する
酸化イッテルビウム粉末の重量比が１０以上及び酸化珪
素粉末を０．５〜９．５重量％よりなる混合粉体を成型
し、窒素ガス雰囲気中で１７００〜２１００℃で焼成し
た後、９００〜９４０℃の範囲まで２０℃毎分以上で降
温し、５分以上保持した後、再び１１５０〜１３５０℃
の範囲に昇温し、４〜８時間の範囲で保持することを特
徴とする窒化珪素質焼結体の製造方法。 である。According to the present invention, (1) 70 to 97% by weight of silicon nitride, 2 to 30% by weight of ytterbium oxide, and 0.1 to 5% of aluminum oxide.
Microcrystals of ytterbium silicon oxynitride having a composition of 0% by weight and a weight ratio of ytterbium oxide to aluminum oxide of 10 or more, and having a stable crystal phase in a grain boundary part which is a gap between silicon nitride particles in a sintered body. And a silicon nitride sintered body. (2) 70 to 97% by weight of silicon nitride powder, 2 to 30% by weight of ytterbium oxide powder, 0.1 to 5.0% by weight of aluminum oxide powder, and the weight ratio of ytterbium oxide powder to aluminum oxide powder is 10 or more. 1 to 21 in a nitrogen gas atmosphere
After firing at 00 ℃, 20 to 900 ~ 940 ℃ range
After lowering the temperature at ℃ per minute or more and holding it for 5 minutes or more, 115
A method for producing a silicon nitride-based sintered body, which comprises raising the temperature to a range of 0 to 1350 ° C. and holding the temperature for 4 to 8 hours. (3) 70 to 97% by weight of silicon nitride, 2 to 30% by weight of ytterbium oxide, 0.5 to 9.5% by weight of silicon oxide, and a grain boundary that is a gap between silicon nitride particles in a sintered body. A silicon nitride-based sintered body characterized in that a part thereof is composed of fine crystals of ytterbium silicon oxide, which is a stable crystal phase. (4) 70-97% by weight of silicon nitride powder, 2-30% by weight of ytterbium oxide powder, and 0.5% of silicon oxide powder.
~ 9.5 wt% mixed powder is molded and fired in a nitrogen gas atmosphere at 1700 ~ 2100 ° C, then 900 ~
A silicon nitride material characterized in that the temperature is lowered to a range of 940 ° C. at 20 ° C. per minute or more, and is held for 5 minutes or more, then is again raised to a range of 1150 to 1350 ° C. and is held for a range of 4 to 8 hours. Manufacturing method of sintered body. (5) 70 to 97% by weight of silicon nitride, 2 to 30% by weight of ytterbium oxide, and 0.1 to 5% by weight of aluminum oxide.
The composition is 0% by weight, the weight ratio of ytterbium oxide to aluminum oxide is 10 or more, and the composition of silicon oxide is 0.5 to 9.5% by weight, and the grain boundary portion which is the gap between the silicon nitride particles in the sintered body is stable. Sintered silicon nitride, characterized by being composed of microcrystals of ytterbium silicon oxynitride and ytterbium silicon oxide, which have different crystal phases. (6) 70 to 97% by weight of silicon nitride powder, 2 to 30% by weight of ytterbium oxide powder, 0.1 to 5.0% by weight of aluminum oxide powder, and the weight ratio of ytterbium oxide powder to aluminum oxide powder is 10 or more. And 0.5 to 9.5% by weight of silicon oxide powder are molded into a mixed powder, which is fired at 1700 to 2100 ° C. in a nitrogen gas atmosphere, and then heated to 900 to 940 ° C. at 20 ° C. per minute or more. After lowering the temperature and holding it for 5 minutes or more, again 1150 to 1350 ° C
The method for producing a silicon nitride-based sintered body, which is characterized in that the temperature is raised to the above range and the temperature is maintained for 4 to 8 hours. Is.
【０００５】[0005]
【作用】本発明によると、窒化珪素質焼結体の粒界部に
高温でも安定なイッテルビウムシリコンオキシナイトラ
イド及び／又はイッテルビウムシリコンオキサイドの微
結晶を設けたことにより、高温強度の低下が少なく、耐
酸化性にも優れた高い信頼性をもつ窒化珪素質焼結体
を、通常の常圧焼結法で製造することにより安価で提供
される。以下、更に本発明に係わる数値限定の理由を説
明する。According to the present invention, since the ytterbium silicon oxynitride and / or ytterbium silicon oxide microcrystals that are stable even at high temperature are provided in the grain boundary portion of the silicon nitride sintered body, the decrease in high temperature strength is small, A silicon nitride-based sintered body having excellent oxidation resistance and high reliability can be provided at low cost by manufacturing it by a normal atmospheric pressure sintering method. The reason for limiting the numerical values according to the present invention will be described below.
【０００６】（１）窒化珪素：７０〜９７重量％：窒化
珪素粉末は窒化珪素焼結体を作製する際の主剤となるも
ので、７０重量％未満であると相対的に助剤の量が多す
ぎて焼結の際に変形が著しくなり、室温、高温において
強度を発現することが不可能で、窒化珪素焼結体の一般
的な特徴である優れた機械的性質がすべて失われてしま
う。一方、９７重量％を越えると相対的に助剤の量が少
なくなり、難焼結性である窒化珪素をうまく焼結させる
ことができず、緻密化が難しくなり当然強度が落ちる。
より好ましくは７５〜９５重量％である。(1) Silicon Nitride: 70 to 97% by Weight: Silicon nitride powder is a main agent for producing a silicon nitride sintered body. If it is less than 70% by weight, the amount of the auxiliary agent is relatively large. If the amount is too large, the deformation becomes significant during sintering, strength cannot be exhibited at room temperature and high temperature, and all the excellent mechanical properties that are general features of silicon nitride sintered bodies are lost. . On the other hand, if it exceeds 97% by weight, the amount of the auxiliary agent becomes relatively small, and it is difficult to sinter the silicon nitride, which is difficult to sinter, so that it becomes difficult to densify and the strength naturally lowers.
It is more preferably 75 to 95% by weight.
【０００７】（２）酸化イッテルビウム：２〜３０重量
％：酸化イッテルビウムは酸化アルミニウム及び窒化珪
素粉末に酸化層として存在する酸化珪素並びに添加した
酸化珪素と共に焼結温度付近で反応、融解し、窒化珪素
焼結体作製時の助剤として作用し、緻密化に貢献すると
ともに、形成された焼結体の高温強度の低下を防ぐ作用
ももつ。また、酸化アルミニウムを使用しない場合であ
っても、高度に制御された条件下では酸化イッテルビウ
ムと酸化珪素のみで助剤としての作用をはたせる。この
場合には金属元素がひとつ少なくなるので、より共晶温
度が上昇し、高温強度の低下を防ぐ効果が高い。しかし
２重量％未満であると、焼結性が悪化し十分緻密化する
ことが困難で高温強度の低下が著しい。また、３０重量
％を越えると、相対的に酸化アルミニウムの量が少なく
なり、焼結性が低下して強度が低下する。より好ましく
は５〜２３重量％である。(2) Ytterbium oxide: 2 to 30% by weight: Ytterbium oxide reacts and melts with aluminum oxide and silicon oxide existing as an oxide layer in silicon nitride powder and added silicon oxide in the vicinity of the sintering temperature to form silicon nitride. It acts as an auxiliary agent at the time of producing a sintered body, contributes to densification, and also has an action of preventing a decrease in high temperature strength of the formed sintered body. Even when aluminum oxide is not used, only ytterbium oxide and silicon oxide act as an auxiliary agent under highly controlled conditions. In this case, since the amount of the metal element is reduced by one, the eutectic temperature is further increased, and the effect of preventing the decrease in high temperature strength is high. However, if it is less than 2% by weight, the sinterability is deteriorated, it is difficult to sufficiently densify, and the high temperature strength is remarkably reduced. On the other hand, if it exceeds 30% by weight, the amount of aluminum oxide is relatively small, the sinterability is lowered and the strength is lowered. It is more preferably 5 to 23% by weight.
【０００８】（３）酸化アルミニウム：０．１〜５．０
重量％：酸化アルミニウムは酸化イッテルビウム及び窒
化珪素粉末に酸化層として存在する酸化珪素並びに添加
した酸化珪素と共に焼結温度付近で反応、融解し、窒化
珪素焼結体作製時の助剤として作用し緻密化に貢献する
が、高温強度を低下させる作用ももつ。よって高温強度
を低下させないためには酸化アルミニウムの量を少なく
すること、すなわち添加しないことが好ましいが、添加
しないと焼結が不十分になるため、強度の絶対値が低く
なる。また、焼結後の熱処理によって結晶化するイッテ
ルビウムシリコンオキシナイトライドの主構成成分では
ないもののアルミニウムはこの結晶化を容易にし、結晶
中に固溶することにより、結晶の高温安定性を増大す
る。しかし、０．１重量％未満であると結晶化がしにく
くなることがあり、結晶の高温安定性が不安定となるた
め、焼結体の高温強度が低下する。また、５．０重量％
を越えると焼結性は良好で十分緻密化するが、結晶中へ
の固溶量を越えてしまうため高温強度の低下が著しい。
より好ましくは０．１〜２．０重量％である。(3) Aluminum oxide: 0.1 to 5.0
% By weight: Aluminum oxide reacts and melts with ytterbium oxide, silicon oxide existing as an oxide layer in silicon nitride powder, and added silicon oxide at a temperature around the sintering temperature, and acts as an auxiliary agent during the production of a silicon nitride sintered body to be dense. However, it also has the effect of lowering the high temperature strength. Therefore, in order not to reduce the high temperature strength, it is preferable to reduce the amount of aluminum oxide, that is, it is preferable not to add it. However, if it is not added, the sintering becomes insufficient and the absolute value of the strength becomes low. Aluminum, which is not the main constituent of ytterbium silicon oxynitride that crystallizes by heat treatment after sintering, facilitates this crystallization and forms a solid solution in the crystal, thereby increasing the high temperature stability of the crystal. However, if it is less than 0.1% by weight, crystallization may be difficult and the high temperature stability of the crystal becomes unstable, so that the high temperature strength of the sintered body decreases. Also, 5.0% by weight
If it exceeds, the sinterability will be good and the densification will be sufficient.
It is more preferably 0.1 to 2.0% by weight.
【０００９】（４）酸化珪素：０．５〜９．５重量％：
酸化珪素は酸化イッテルビウム等と共に焼結温度付近で
反応、融解し、窒化珪素焼結体作製時の助剤として作用
し緻密化に貢献する。焼結後は粒界中に形成されるガラ
ス相の骨格をなし、高温特性を支配する。酸化珪素を助
剤として添加する場合、一般に量が多い方が焼結性が向
上するものの焼結体の高温特性は低下する。しかし０．
５重量％未満であると焼結性が低下し緻密化せず、９．
５重量％を越えると焼結後のガラス相も多量となり、結
果的に高温強度を低下させる。より好ましくは０．７〜
９．０重量％である。酸化珪素を積極的に添加しない場
合であっても、窒化珪素粉末に酸化層として存在する酸
化珪素が同様の作用をするが、この場合微量となり焼結
性の低下が避けられないため、酸化アルミニウムの添加
が不可欠となる。なお、上記いずれの原料も平均粒径２
μｍ以下とするのが望ましい。(4) Silicon oxide: 0.5 to 9.5% by weight:
Silicon oxide reacts and melts near the sintering temperature together with ytterbium oxide and the like, and acts as an auxiliary agent when producing a silicon nitride sintered body, thus contributing to densification. After sintering, it forms the skeleton of the glass phase formed in the grain boundaries and controls the high temperature characteristics. When silicon oxide is added as an auxiliary agent, generally, the higher the amount, the better the sinterability, but the high temperature characteristics of the sintered body deteriorate. But 0.
If it is less than 5% by weight, the sinterability is deteriorated and densification does not occur.
If it exceeds 5% by weight, a large amount of glass phase will be obtained after sintering, resulting in a decrease in high temperature strength. More preferably 0.7-
It is 9.0% by weight. Even if silicon oxide is not positively added, silicon oxide existing in the silicon nitride powder as an oxide layer has the same function, but in this case, a small amount of silicon oxide is unavoidable, and therefore, a decrease in sinterability cannot be avoided. Is essential. In addition, all of the above raw materials have an average particle size of
It is desirable that the thickness is not more than μm.
【００１０】（５）酸化アルミニウム粉末に対する酸化
イッテルビウム粉末の重量比：１０以上：酸化イッテル
ビウムと酸化アルミニウムは窒化珪素粉末に酸化層とし
て存在する酸化珪素並びに添加した酸化珪素と共に焼結
温度付近で反応、融解し、窒化珪素焼結体作製時の助剤
として作用する。これらの成分は焼結後、主として粒界
中にガラス相として存在し、高温特性を支配する。この
比が１０未満であると形成されるガラス相の粘性が低下
するためと考えられるが、高温強度が低下する。またこ
の比があまり大きすぎると、焼結性が低下するので、よ
り好ましくは２０〜５０である。(5) Weight ratio of ytterbium oxide powder to aluminum oxide powder: 10 or more: Ytterbium oxide and aluminum oxide react with silicon oxide existing as an oxide layer in silicon nitride powder and added silicon oxide in the vicinity of the sintering temperature, It melts and acts as an auxiliary agent when producing a silicon nitride sintered body. After sintering, these components mainly exist as a glass phase in grain boundaries and dominate high temperature characteristics. It is considered that when this ratio is less than 10, the viscosity of the glass phase formed is lowered, but the high temperature strength is lowered. Further, if the ratio is too large, the sinterability is lowered, so that it is more preferably 20 to 50.
【００１１】（６）不純物はいずれの元素にせよ１００
ｐｐｍ以下が望ましい。(6) Any element may be used as an impurity.
ppm or less is desirable.
【００１２】（７）窒素ガス雰囲気：窒素ガス加圧雰囲
気は窒化珪素が高温で昇華するのを防ぐために行うもの
である。なお、１０ｋｇ／ｃｍ2 を超えると高圧ガス取
締法による適用を受け、ガスの製造、容器の取扱等に厳
しい規制を受けるため、実際の製品の製造に不利であり
コストにもひびくので、できれば１０ｋｇ／ｃｍ2 以下
が望ましい。より好ましくは６〜９．９ｋｇ／ｃｍ2 で
ある。(7) Nitrogen gas atmosphere: The nitrogen gas pressurized atmosphere is used to prevent silicon nitride from sublimating at high temperature. If it exceeds 10 kg / cm 2, it will be applied under the High Pressure Gas Control Law and will be subject to strict restrictions on gas production, container handling, etc., which is disadvantageous in the actual production of the product and costly. / Cm 2 or less is desirable. More preferably, it is 6 to 9.9 kg / cm 2 .
【００１３】（８）１７００〜２１００℃で焼成：セラ
ミックス材料は粉体を焼き固めて焼結して作製する。焼
結させる時に焼成が必要となるが、窒化珪素の場合は助
剤を添加して焼結させ易くしているものの基本的に難焼
結性であって焼結には高い焼成温度が必要となる。１７
００℃未満の温度では助剤の反応、融解があまり起こら
ずに焼結が進まず、緻密化しない。また２１００℃を越
える温度であると窒化珪素が昇華、分解してしまい同じ
く緻密化しない。より好ましくは１７５０〜２０５０℃
である。(8) Firing at 1700 to 2100 ° C .: The ceramic material is produced by baking and sintering powder. Although firing is required at the time of sintering, in the case of silicon nitride, although an auxiliary agent is added to facilitate sintering, it is basically difficult to sinter and a high firing temperature is required for sintering. Become. 17
If the temperature is less than 00 ° C., the reaction and melting of the auxiliary agent do not occur so much, the sintering does not proceed, and the densification does not occur. Further, if the temperature exceeds 2100 ° C., silicon nitride is sublimated and decomposed, and similarly, densification does not occur. More preferably 1750 to 2050 ° C
Is.
【００１４】（９）焼成時間：焼成時間は特に限定はな
いが、セラミックス材料を焼成する際、ごく通常の外部
加熱炉を用いると試料の表面と内部で熱伝導の差により
温度差が少なからず生じてしまうので、目的温度まで昇
温後、ある程度の時間の保持は必要である。なお、１０
時間以上の保持しても、もはや焼結はそれほど進まず、
コストの点からも意味がなくなるので、できればそれ以
下がよい。より好ましくは９時間以下である。(9) Firing time: The firing time is not particularly limited, but when firing a ceramic material, a temperature difference is not small due to a difference in heat conduction between the surface and the inside of the sample when an ordinary external heating furnace is used. Therefore, it is necessary to maintain the temperature for some time after the temperature is raised to the target temperature. 10
Even if it holds for more than a time, sintering will not progress so much,
There is no point in terms of cost, so it is better if it is less than that. It is more preferably 9 hours or less.
【００１５】（１０）９００〜９４０℃の範囲まで降
温：粒界ガラス相は加熱処理によって結晶化することが
可能であるが、適正な処理を行わないと安定な結晶相の
析出に膨大な時間がかかったりする等、非効率的なプロ
セスとなりうる。よって一般的な結晶成長理論に基づ
き、適当な結晶核を析出させた後、その核を成長させる
といった２段階の熱処理が効率的となる。ここでは結晶
核析出温度の決定に際し、助剤組成成分を主成分とした
模擬粒界ガラス試料を作製し、これに示差熱分析、Ｘ線
回折法等の方法を用いてガラス転移点の温度を調査した
結果、９１８℃であることが判明した。一般にこの付近
の温度で結晶核の生成速度が最大となることが知られて
おり、この温度より低い９００℃未満であるとガラス構
造が安定な温度領域となり、核の析出はもとより結晶化
がしにくく、９４０℃を越えると融液の状態が安定で、
核の析出がしにくい。より好ましくは９１０〜９３０℃
である。(10) Decreasing temperature in the range of 900 to 940 ° C .: The grain boundary glass phase can be crystallized by heat treatment, but if proper treatment is not carried out, it takes a huge amount of time for stable precipitation of the crystal phase. It can be an inefficient process such as taking a long time. Therefore, based on a general crystal growth theory, a two-step heat treatment of precipitating an appropriate crystal nucleus and then growing the nucleus becomes efficient. Here, in determining the crystal nucleus deposition temperature, a simulated grain boundary glass sample containing an auxiliary composition component as a main component was prepared, and the temperature of the glass transition point was measured by a method such as differential thermal analysis or X-ray diffraction. As a result of investigation, it was found to be 918 ° C. It is generally known that the rate of crystal nucleus generation is maximized at temperatures around this temperature. If the temperature is lower than 900 ° C, which is lower than this temperature, the glass structure is in a stable temperature region, and crystallization as well as nuclei precipitation occurs. It is difficult, and the temperature of the melt is stable above 940 ° C.
Difficult to deposit nuclei. More preferably 910 to 930 ° C
Is.
【００１６】（１１）２０℃毎分以上で降温：粒界ガラ
ス相中に目的とする結晶核を有効に析出させるために
は、なるべく早く降温する必要がある。２０℃毎分未満
であると望まない相が析出したり、後の熱処理が有効に
作用しない可能性がある。より好ましくは４０℃毎分で
ある。(11) Temperature drop at 20 ° C./min or more: In order to effectively precipitate a target crystal nucleus in the grain boundary glass phase, it is necessary to lower the temperature as soon as possible. If it is less than 20 ° C./min, an undesired phase may be precipitated or the subsequent heat treatment may not work effectively. More preferably, it is 40 ° C. per minute.
【００１７】（１２）５分以上で保持：粒界ガラス相中
に目的とする結晶核を有効に析出させるために、ガラス
転移点の温度付近で保持をする必要があるが、５分未満
であると核が十分析出しない可能性がある。より好まし
くは１０分以上である。(12) Hold for 5 minutes or more: In order to effectively precipitate the desired crystal nuclei in the grain boundary glass phase, it is necessary to hold the glass nucleus near the glass transition temperature, but in less than 5 minutes If so, the nuclei may not be sufficiently deposited. It is more preferably 10 minutes or more.
【００１８】（１３）１１５０℃〜１３５０℃の範囲に
昇温：粒界ガラス相は加熱処理によって結晶化すること
が可能であるが、適正な処理を行わないと安定な結晶相
の析出に膨大な時間がかかったりする等、非効率的なプ
ロセスとなりうる。よって一般的な結晶成長理論に基づ
き、適当な結晶核を析出させた後、その核を成長させる
といった２段階の熱処理が効率的となる。ここでは結晶
核成長温度の決定に際し、助剤組成成分を主成分とした
模擬粒界ガラス試料を作製し、これに示差熱分析、Ｘ線
回折法等の方法を用いて結晶化開始温度を調査した結
果、１２０９℃であることが判明した。一般にこの付近
の温度で結晶の成長速度が最大となることが知られてお
り、この温度より低い１１５０℃未満であると結晶化の
速度が遅く、別の不安定相が析出する可能性があり、１
３５０℃を越えてもまた速度が遅くなる。より好ましく
は１２００〜１３００℃である。(13) Temperature rise in the range of 1150 ° C. to 1350 ° C .: The grain boundary glass phase can be crystallized by heat treatment, but if proper treatment is not carried out, stable precipitation of crystal phase will occur. It can be an inefficient process such as taking a long time. Therefore, based on a general crystal growth theory, a two-step heat treatment of precipitating an appropriate crystal nucleus and then growing the nucleus becomes efficient. Here, when determining the crystal nucleus growth temperature, a simulated grain boundary glass sample containing the auxiliary composition component as the main component was prepared, and the crystallization start temperature was investigated using methods such as differential thermal analysis and X-ray diffraction. As a result, it was found to be 1209 ° C. It is generally known that the crystal growth rate becomes maximum at a temperature in the vicinity of this temperature. If the temperature is lower than 1150 ° C., which is lower than this temperature, the crystallization rate is slow and another unstable phase may be precipitated. 1
Even if the temperature exceeds 350 ° C, the speed becomes slow again. More preferably, it is 1200 to 1300 ° C.
【００１９】（１４）４〜８時間の範囲で保持：粒界ガ
ラス相中に目的とする結晶を効率的に成長させるため
に、結晶化開始温度付近で保持をする必要があるが、４
時間未満であると成長が十分行われない可能性があり、
８時間を越えてもほとんど変化がない。より好ましくは
４〜６時間である。(14) Hold for 4 to 8 hours: In order to efficiently grow a target crystal in the grain boundary glass phase, it is necessary to hold near the crystallization start temperature.
If it is less than time, it may not grow sufficiently,
There is almost no change over 8 hours. More preferably, it is 4 to 6 hours.
【００２０】[0020]
【実施例】試験に供した原料粉末は窒化珪素原料粉末が
平均粒径０．５μｍ（結晶子径は０．２μｍ以下）の高
純度粉末を、焼結助剤の酸化イッテルビウムは平均粒径
が１．２μｍの粉末を、酸化アルミニウムは平均粒径が
０．８μｍの粉末を、酸化珪素は平均粒径が０．３μｍ
の粉末を用いた。各粉末の配合比としては表１に示した
とおりであり、試料番号は窒化珪素粉末が７５．９５
重量％、酸化イッテルビウム粉末が２２．９０重量％及
び酸化アルミニウム粉末が１．１５重量％、試料番号
は窒化珪素粉末が９４．４１重量％、酸化イッテルビウ
ム粉末が５．３２重量％及び酸化アルミニウム粉末が
０．２７重量％、試料番号は窒化珪素粉末が９０．０
０重量％、酸化イッテルビウム粉末が７．６６重量％及
び酸化珪素粉末が２．３４重量％、試料番号は窒化珪
素粉末が７０．００重量％、酸化イッテルビウム粉末が
２２．９９重量％及び酸化珪素粉末が７．０１重量％、
試料番号は窒化珪素粉末が７０．００重量％、酸化イ
ッテルビウム粉末が２２．９０重量％、酸化アルミニウ
ム粉末が１．１５重量％及び酸化珪素粉末が５．９５重
量％の５つの試料について検討した。なお、これらの例
のすべての試験について、分散剤としてはポリエチレン
イミン系のものを、溶媒としては１−ブチルアルコール
を用いた湿式混合、粉砕法によった。EXAMPLE The raw material powder used in the test was a high-purity powder of silicon nitride raw material powder having an average particle diameter of 0.5 μm (crystallite diameter of 0.2 μm or less), and the sintering aid ytterbium oxide had an average particle diameter of 0.5 μm. 1.2 μm powder, aluminum oxide has a mean particle size of 0.8 μm, and silicon oxide has a mean particle size of 0.3 μm.
The powder of was used. The compounding ratio of each powder is as shown in Table 1, and the sample number is 75.95 for silicon nitride powder.
% By weight, ytterbium oxide powder by 22.90% by weight and aluminum oxide powder by 1.15% by weight, sample number is silicon nitride powder 94.41% by weight, ytterbium oxide powder by 5.32% by weight and aluminum oxide powder by 0.27% by weight, sample number 90.0 for silicon nitride powder
0 wt%, ytterbium oxide powder 7.66 wt% and silicon oxide powder 2.34 wt%, sample number is silicon nitride powder 70.00 wt%, ytterbium oxide powder 22.99 wt% and silicon oxide powder 7.01% by weight,
Regarding the sample numbers, five samples of silicon nitride powder of 70.00% by weight, ytterbium oxide powder of 22.90% by weight, aluminum oxide powder of 1.15% by weight and silicon oxide powder of 5.95% by weight were examined. In all of the tests in these examples, a polyethyleneimine-based dispersant and a 1-butyl alcohol solvent were used for wet mixing and pulverization.
【００２１】窒化珪素質焼結体の作製に際し、まず混合
には原料粉末１００重量％に対し、ポリエチレンイミン
系分散剤３重量％、１−ブチルアルコール溶媒１２０重
量％を加え、ジルコニアボールを用いて均一に混合した
後、乾燥しプレスで直径６０ｍｍφ、約６ｍｍの円盤状
に成型し、４ｔ／ｃｍ2 の圧力で静水圧プレスして成型
体を得た。この成型体を真空中で５００℃まで加熱し、
１時間保持して脱脂した後、窒素ガス６ｋｇ毎平方セン
チメートルの加圧下、１℃／ｍｉｎで１８００℃まで昇
温し、４時間焼結した。その後９２０℃まで４０℃毎分
で降温し、１０分保持した後、再び１３００℃に昇温
し、４時間保持して結晶化させた試料と、結晶化させな
かった試料とで高温曲げ強さ、酸化増量等の高温特性を
比較した結果を表２に示す。これによると結晶化によ
り、高温における強度低下が抑えられるばかりでなく、
耐酸化性も増大することとなった。In producing a silicon nitride sintered body, first, 3% by weight of a polyethyleneimine-based dispersant and 120% by weight of a 1-butyl alcohol solvent were added to 100% by weight of raw material powder, and zirconia balls were used. After being uniformly mixed, the mixture was dried and molded into a disk shape having a diameter of 60 mmφ and a diameter of about 6 mm by a press, and was hydrostatically pressed at a pressure of 4 t / cm 2 to obtain a molded body. This molded body is heated to 500 ° C in vacuum,
After holding for 1 hour to degrease, it was heated to 1800 ° C. at 1 ° C./min under a pressure of 6 kg of nitrogen gas per square centimeter, and sintered for 4 hours. After that, the temperature was lowered to 920 ° C. at 40 ° C. per minute, held for 10 minutes, then raised again to 1300 ° C., held for 4 hours to crystallize, and the sample not crystallized had a high bending strength. Table 2 shows the results of comparison of high temperature characteristics such as increase in oxidation. According to this, not only the decrease in strength at high temperature is suppressed by crystallization, but also
Oxidation resistance is also increased.
【００２２】[0022]
【表１】 [Table 1]
【００２３】[0023]
【表２】 [Table 2]
【００２４】[0024]
【発明の効果】本発明により、高温強度の低下が大幅に
抑えられ、高温強度の高い窒化珪素質焼結体を極一般的
な製造方法によって安価に提供することができ、産業上
の利用価値が大きい。EFFECTS OF THE INVENTION According to the present invention, a decrease in high temperature strength can be significantly suppressed, and a silicon nitride sintered body having high high temperature strength can be provided at a low cost by a very general manufacturing method. Is big.
Claims (6)
テルビウムを２〜３０重量％、酸化アルミニウムを０．
１〜５．０重量％及び酸化アルミニウムに対する酸化イ
ッテルビウムの重量比が１０以上の組成で、かつ焼結体
中の窒化珪素粒子の間隙である粒界部が安定な結晶相で
あるイッテルビウムシリコンオキシナイトライドの微結
晶で構成されてなることを特徴とする窒化珪素質焼結
体。1. 70 to 97% by weight of silicon nitride, 2 to 30% by weight of ytterbium oxide, and 0.
Ytterbium silicon oxynite having a composition of 1 to 5.0% by weight and a weight ratio of ytterbium oxide to aluminum oxide of 10 or more, and having a stable crystal phase in a grain boundary part which is a gap between silicon nitride particles in a sintered body. A silicon nitride-based sintered body, characterized by being composed of microcrystals of ride.
イッテルビウム粉末を２〜３０重量％、酸化アルミニウ
ム粉末を０．１〜５．０重量％及び酸化アルミニウム粉
末に対する酸化イッテルビウム粉末の重量比が１０以上
よりなる混合粉体を成型し、窒素ガス雰囲気中で１７０
０〜２１００℃で焼成した後、９００〜９４０℃の範囲
まで２０℃毎分以上で降温し、５分以上保持した後、再
び１１５０〜１３５０℃の範囲に昇温し、４〜８時間の
範囲で保持す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 powder of 70 to 97% by weight, a ytterbium oxide powder of 2 to 30% by weight, an aluminum oxide powder of 0.1 to 5.0% by weight, and a weight ratio of the ytterbium oxide powder to the aluminum oxide powder. A mixed powder consisting of 10 or more is molded and then 170 in a nitrogen gas atmosphere.
After firing at 0 to 2100 ° C., the temperature is lowered to 900 to 940 ° C. at 20 ° C. per minute or more, and after being held for 5 minutes or more, the temperature is raised again to the range of 1150 to 1350 ° C. and the range of 4 to 8 hours. A method for manufacturing a silicon nitride sintered body, characterized in that:
テルビウムを２〜３０重量％及び酸化珪素を０．５〜
９．５重量％で、かつ焼結体中の窒化珪素粒子の間隙で
ある粒界部が安定な結晶相であるイッテルビウムシリコ
ンオキサイドの微結晶で構成されてなることを特徴とす
る窒化珪素質焼結体。3. 70 to 97% by weight of silicon nitride, 2 to 30% by weight of ytterbium oxide, and 0.5 to 0.5% of silicon oxide.
9.5% by weight, and the grain boundary portion, which is a gap between the silicon nitride particles in the sintered body, is composed of ytterbium silicon oxide microcrystals that is a stable crystal phase. Union.
イッテルビウム粉末を２〜３０重量％及び酸化珪素粉末
を０．５〜９．５重量％よりなる混合粉体を成型し、窒
素ガス雰囲気中で１７００〜２１００℃で焼成した後、
９００〜９４０℃の範囲まで２０℃毎分以上で降温し、
５分以上保持した後、再び１１５０〜１３５０℃の範囲
に昇温し、４〜８時間の範囲で保持することを特徴とす
る窒化珪素質焼結体の製造方法。4. A mixed powder comprising 70 to 97% by weight of silicon nitride powder, 2 to 30% by weight of ytterbium oxide powder, and 0.5 to 9.5% by weight of silicon oxide powder is molded, and a nitrogen gas atmosphere is formed. After firing at 1700-2100 ° C in
Decrease the temperature in the range of 900-940 ℃ at 20 ℃ or more per minute,
A method for producing a silicon nitride sintered body, which is characterized by holding for 5 minutes or more and then again raising the temperature to a range of 1150 to 1350 ° C. and holding for 4 to 8 hours.
テルビウムを２〜３０重量％、酸化アルミニウムを０．
１〜５．０重量％、酸化アルミニウムに対する酸化イッ
テルビウムの重量比が１０以上及び酸化珪素を０．５〜
９．５重量％の組成で、かつ焼結体中の窒化珪素粒子の
間隙である粒界部が安定な結晶相であるイッテルビウム
シリコンオキシナイトライド及びイッテルビウムシリコ
ンオキサイドの微結晶で構成されてなることを特徴とす
る窒化珪素質焼結体。5. 70 to 97% by weight of silicon nitride, 2 to 30% by weight of ytterbium oxide, and 0.
1 to 5.0% by weight, the weight ratio of ytterbium oxide to aluminum oxide is 10 or more, and silicon oxide is 0.5 to
The composition has a composition of 9.5% by weight, and a grain boundary part which is a gap between silicon nitride particles in the sintered body is composed of ytterbium silicon oxynitride and ytterbium silicon oxide microcrystals which are stable crystal phases. A silicon nitride-based sintered body characterized by:
イッテルビウム粉末を２〜３０重量％、酸化アルミニウ
ム粉末を０．１〜５．０重量％、酸化アルミニウム粉末
に対する酸化イッテルビウム粉末の重量比が１０以上及
び酸化珪素粉末を０．５〜９．５重量％よりなる混合粉
体を成型し、窒素ガス雰囲気中で１７００〜２１００℃
で焼成した後、９００〜９４０℃の範囲まで２０℃毎分
以上で降温し、５分以上保持した後、再び１１５０〜１
３５０℃の範囲に昇温し、４〜８時間の範囲で保持する
ことを特徴とする窒化珪素質焼結体の製造方法。6. The silicon nitride powder is 70 to 97% by weight, the ytterbium oxide powder is 2 to 30% by weight, the aluminum oxide powder is 0.1 to 5.0% by weight, and the weight ratio of the ytterbium oxide powder to the aluminum oxide powder is 10 or more and 0.5 to 9.5 wt% of silicon oxide powder are molded into a mixed powder, and the temperature is 1700 to 2100 ° C. in a nitrogen gas atmosphere.
After firing at 20 ° C. per minute or more, the temperature is lowered to 900 to 940 ° C., and the temperature is held for 5 minutes or more.
A method for producing a silicon nitride sintered body, which comprises raising the temperature to a range of 350 ° C. and holding the temperature for a period of 4 to 8 hours.
Priority Applications (1)
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|---|---|---|---|
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|---|---|---|---|
| JP6194158A JP3035163B2 (en) | 1994-08-18 | 1994-08-18 | Silicon nitride sintered body and method for producing the same |
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1994
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