JP2005187235A - Highly heat-conductive aluminum nitride sintered compact - Google Patents
Highly heat-conductive aluminum nitride sintered compact Download PDFInfo
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- JP2005187235A JP2005187235A JP2003428004A JP2003428004A JP2005187235A JP 2005187235 A JP2005187235 A JP 2005187235A JP 2003428004 A JP2003428004 A JP 2003428004A JP 2003428004 A JP2003428004 A JP 2003428004A JP 2005187235 A JP2005187235 A JP 2005187235A
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 7
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- 238000004519 manufacturing process Methods 0.000 description 7
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 6
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- 230000003247 decreasing effect Effects 0.000 description 6
- PIGFYZPCRLYGLF-UHFFFAOYSA-N Aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 description 5
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- CMIHHWBVHJVIGI-UHFFFAOYSA-N gadolinium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Gd+3].[Gd+3] CMIHHWBVHJVIGI-UHFFFAOYSA-N 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
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- DOIRQSBPFJWKBE-UHFFFAOYSA-N dibutyl phthalate Chemical compound CCCCOC(=O)C1=CC=CC=C1C(=O)OCCCC DOIRQSBPFJWKBE-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 229910003440 dysprosium oxide Inorganic materials 0.000 description 2
- NLQFUUYNQFMIJW-UHFFFAOYSA-N dysprosium(iii) oxide Chemical compound O=[Dy]O[Dy]=O NLQFUUYNQFMIJW-UHFFFAOYSA-N 0.000 description 2
- 229910001938 gadolinium oxide Inorganic materials 0.000 description 2
- 229940075613 gadolinium oxide Drugs 0.000 description 2
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- 230000000996 additive effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
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- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical group N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
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Abstract
Description
本発明は高熱伝導性窒化アルミニウム焼結体に係り、特に熱伝導率が高く放熱性および強度特性に優れた窒化アルミニウム焼結体に関する。 The present invention relates to a high thermal conductivity aluminum nitride sintered body, and more particularly to an aluminum nitride sintered body having high thermal conductivity and excellent heat dissipation and strength characteristics.
従来の金属材料と比較して強度、耐熱性、耐食性、耐摩耗性、軽量性などの諸特性に優れたセラミックス焼結体が、半導体、電子機器材料、エンジン用部材、高速切削工具用材料、ノズル、ベアリングなど、従来の金属材料では耐えられない過酷な温度、応力、摩耗条件下で使用される機械部品、構造材や装飾品材料として広く利用されている。 Compared to conventional metal materials, ceramic sintered bodies with excellent properties such as strength, heat resistance, corrosion resistance, wear resistance, and light weight are semiconductors, electronic equipment materials, engine parts, materials for high-speed cutting tools, It is widely used as mechanical parts, structural materials and decorative materials used under severe temperature, stress, and wear conditions that cannot be withstood by conventional metal materials such as nozzles and bearings.
特に窒化アルミニウム（ＡｌＮ）焼結体は高熱伝導性を有する絶縁体であり、シリコン（Ｓｉ）に近い熱膨張係数を有することから高集積化した半導体装置の放熱板や基板として、その用途を拡大している。 In particular, aluminum nitride (AlN) sintered body is an insulator with high thermal conductivity and has a thermal expansion coefficient close to that of silicon (Si), so its application is expanded as a heat sink and substrate for highly integrated semiconductor devices. doing.
従来、上記窒化アルミニウム焼結体は一般的に下記の製造方法によって量産されている。すなわち、セラミックス原料としての窒化アルミニウム粉末にＹ２Ｏ３などの焼結助剤と、有機バインダーと、必要に応じて各種添加剤や溶媒、分散剤とを添加して原料混合体を調製し、得られた原料混合体をロール成形法やドクターブレード法によって成形し、薄板状ないしシート状の成形体としたり、原料混合体をプレス成形して厚板状ないし大型の成形体を形成する。次に得られた成形体は、空気または窒素ガス雰囲気において４００〜５００℃に加熱され脱脂処理され、有機バインダーとして添加された炭化水素成分等が成形体から排除脱脂される。そして脱脂された成形体は窒素ガス雰囲気等で高温度に加熱され緻密化焼結されて窒化アルミニウム焼結体が形成される。 Conventionally, the aluminum nitride sintered body is generally mass-produced by the following manufacturing method. That is, a raw material mixture is prepared by adding a sintering aid such as Y 2 O 3 to an aluminum nitride powder as a ceramic raw material, an organic binder, and various additives, solvents, and dispersants as necessary, The obtained raw material mixture is molded by a roll molding method or a doctor blade method to form a thin plate or sheet-shaped molded body, or the raw material mixture is press-molded to form a thick plate or large-sized molded body. Next, the obtained molded body is heated and degreased at 400 to 500 ° C. in an air or nitrogen gas atmosphere, and hydrocarbon components and the like added as an organic binder are excluded from the molded body and degreased. The degreased molded body is heated to a high temperature in a nitrogen gas atmosphere or the like and densified and sintered to form an aluminum nitride sintered body.
窒化アルミニウム（ＡｌＮ）は難焼結性セラミックスであり、その緻密化を促進するため、およびＡｌＮ原料粉末中の不純物酸素がＡｌＮ結晶粒子内へ固溶して熱抵抗が増加することを防止するために焼結助剤として酸化イットリウム（Ｙ２Ｏ３）などの希土類酸化物を添加することが一般的に行われている。これらの焼結助剤はＡｌＮ原料粉末中に含まれる酸素と反応して、Ｙ２Ｏ３の場合は３Ｙ２Ｏ３・５Ａｌ２Ｏ３（ＹＡＧ），Ｙ２Ｏ３・Ａｌ２Ｏ３（ＹＡＬ）、２Ｙ２Ｏ３・Ａｌ２Ｏ３（ＹＡＭ）などから成る液相組成物を形成し、焼結体の緻密化を達成するとともに、上記熱抵抗となる不純物酸素を粒界相として固定し高熱伝導化を達成するものと考えられている。 Aluminum nitride (AlN) is a hard-to-sinter ceramic, in order to promote its densification and to prevent impurity oxygen in the AlN raw material powder from dissolving into AlN crystal particles and increasing thermal resistance. In general, a rare earth oxide such as yttrium oxide (Y 2 O 3 ) is added as a sintering aid. These sintering aid reacts with oxygen contained in the AlN raw material powder, Y 2 O For the 3 3Y 2 O 3 · 5Al 2 O 3 (YAG), Y 2 O 3 · Al 2 O 3 ( YAL) , 2Y 2 O 3 .Al 2 O 3 (YAM), etc. are formed to achieve a densified sintered body and to fix the impurity oxygen that becomes the thermal resistance as a grain boundary phase. However, it is thought to achieve high thermal conductivity.
このような従来の高熱伝導性窒化アルミニウム焼結体として、例えば窒化アルミニウムから成り、その結晶粒子の平均粒径が２〜１０μｍである主相と２Ｙ２Ｏ３・Ａｌ２Ｏ３或いはＹ２Ｏ３・Ａｌ２Ｏ３或いは３Ｙ２Ｏ３・５Ａｌ２Ｏ３のいずれかの単一成分からなり、Ｙ２Ｏ３含有量が１．０〜４．６重量％である副相から構成され、熱伝導率が２００Ｗ／ｍ・Ｋ以上で、且つ曲げ強度が４０Ｋｇ／ｍｍ２以上である窒化アルミニウム焼結体が提案されている（例えば、特許文献１参照。）。
しかしながら、従来の製造方法においては、原料粉末の平均粒径、不純物、焼結助剤の種類および添加量、脱脂、焼結条件などを厳正に管理した場合においても、前記不純物酸素を固定するのに必要な多量の希土類酸化物を添加しているため、熱抵抗となる酸化物量が多くなり２１５Ｗ／ｍ・Ｋ以上の高い熱伝導率が得られず、ＡｌＮ焼結体固有の最大特性である優れた放熱特性が損なわれる場合が多く、技術的改善が強く要請されている。 However, in the conventional manufacturing method, the impurity oxygen is fixed even when the average particle size of the raw material powder, impurities, the type and amount of the sintering aid, degreasing, and sintering conditions are strictly controlled. Since a large amount of rare earth oxide necessary for the addition is added, the amount of oxide that becomes thermal resistance increases, and a high thermal conductivity of 215 W / m · K or more cannot be obtained, which is a maximum characteristic unique to an AlN sintered body. In many cases, excellent heat dissipation characteristics are impaired, and technical improvement is strongly demanded.
本発明は上記問題点を解決するためになされたものであり、特に熱伝導率が高く放熱性や機械的特性が優れた高熱伝導性窒化アルミニウム焼結体を提供することを目的とする。 The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly heat-conductive aluminum nitride sintered body having particularly high heat conductivity and excellent heat dissipation and mechanical characteristics.
上記目的を達成するために、本発明者らは焼結助剤の添加量、熱伝導の阻害要因である酸素の低減法、脱脂状態が焼結体の緻密化や組織状態、熱伝導率に及ぼす影響を比較検討した。その結果、焼結助剤としてのＧｄ，Ｄｙ元素（Ｒｅ元素）の添加量および酸素量を適正範囲に調整して緻密化を促進し、熱伝導率の阻害要因である酸素を除去するために必要な適正量の炭素量を脱脂工程の条件制御により残存させ、次の焼結工程における緻密化焼結前に仮焼処理工程を導入し、焼結後の粒界相を熱抵抗が低いＲｅ４Ａｌ２Ｏ９、Ｒｅ２Ｏ３、およびＲｅＡｌ２Ｏ３（但し、ＲｅはＧｄおよびＤｙの少なくとも一方の元素）の少なくとも一方とから成るように限定することにより、焼結体中の不純物酸素量が減少し、２１５Ｗ／ｍ・Ｋ以上、好ましくは２３５Ｗ／ｍ・Ｋ以上の高熱伝導率および良好な機械的強度を有する窒化アルミニウム焼結体が量産性良く容易に得られるという知見を得た。 In order to achieve the above-mentioned object, the present inventors have added a sintering aid, a method for reducing oxygen, which is an impediment to heat conduction, and the degreasing state has become a densified and textured state of the sintered body, and thermal conductivity. The effects were compared. As a result, the amount of Gd and Dy elements (Re element) added as sintering aids and the amount of oxygen are adjusted to an appropriate range to promote densification, and to remove oxygen, which is an impediment to thermal conductivity. The necessary amount of carbon is left by controlling the conditions of the degreasing process, a calcining treatment process is introduced before densification sintering in the next sintering process, and the grain boundary phase after sintering has a low thermal resistance. Impurity oxygen in the sintered body by limiting to 4 Al 2 O 9 , Re 2 O 3 , and ReAl 2 O 3 (where Re is at least one element of Gd and Dy) The amount was reduced, and the knowledge that an aluminum nitride sintered body having a high thermal conductivity of 215 W / m · K or more, preferably 235 W / m · K or more and good mechanical strength can be easily obtained with high mass productivity was obtained. .
また、緻密化焼結後における焼結体の冷却速度を毎時１５０℃以下にして徐冷することにより、粗大な粒界相が発生せず微細で緻密な結晶組織を有するＡｌＮ焼結体が得られるという知見も得られた。本発明は上記知見に基づいて完成されたものである。 In addition, by cooling the sintered body after densification sintering at a cooling rate of 150 ° C. or less per hour, an AlN sintered body having a fine and dense crystal structure without a coarse grain boundary phase is obtained. The knowledge that it is possible was also obtained. The present invention has been completed based on the above findings.
すなわち、本願第１の発明に係る高熱伝導性窒化アルミニウム焼結体は、窒化アルミニウム（１０１面）のＸ線回折強度ＩＡｌＮに対するＡｌ２Ｇｄ４Ｏ９（３１０面）のＸ線回折強度ＩＡｌ２Ｇｄ４Ｏ９の比（ＩＡｌ２Ｇｄ４Ｏ９／ＩＡｌＮ）が０．０４以下であり、上記Ｘ線回折強度ＩＡｌＮに対するＡｌＧｄＯ３（１１２面）のＸ線回折強度ＩＡｌＧｄＯ３の比（ＩＡｌＧｄＯ３／ＩＡｌＮ）が０．０５以下であり、且つ上記Ｘ線回折強度ＩＡｌＮに対するＧｄ２Ｏ３（４０１面）のＸ線回折強度ＩＧｄ２Ｏ３の比（ＩＧｄ２Ｏ３／ＩＡｌＮ）が０．００２〜０．０６であり、熱伝導率が２１５Ｗ／ｍ・Ｋ以上、三点曲げ強度が２５０ＭＰａ以上であることを特徴とする。 That is, the present application first of the high thermal conductivity of aluminum nitride sintered body according to the invention, X-ray diffraction intensity IAL 2 Gd of Al 2 Gd 4 O 9 with respect to the X-ray diffraction intensity IAlN aluminum nitride (101 plane) (310 plane) The ratio of 4 O 9 (IAI 2 Gd 4 O 9 / IALN) is 0.04 or less, and the ratio of the X-ray diffraction intensity IAlGdO 3 of AlGdO 3 (112 plane) to the X-ray diffraction intensity IAlN (IALGdO 3 / IALN) ) Is 0.05 or less, and the ratio of the X-ray diffraction intensity IGd 2 O 3 of Gd 2 O 3 (401 plane) to the X-ray diffraction intensity IAlN (IGd 2 O 3 / IALN) is 0.002 to 0 0.06, a thermal conductivity of 215 W / m · K or more, and a three-point bending strength of 250 MPa or more.
また、本願第２の発明に係る高熱伝導性窒化アルミニウム焼結体は、窒化アルミニウム（１０１面）のＸ線回折強度ＩＡｌＮに対するＡｌ２Ｇｄ４Ｏ９（３１０面）のＸ線回折強度ＩＡｌ２Ｇｄ４Ｏ９の比（ＩＡｌ２Ｇｄ４Ｏ９／ＩＡｌＮ）が０．００４〜０．０４であり、上記Ｘ線回折強度ＩＡｌＮに対するＡｌＧｄＯ３（１１２面）のＸ線回折強度ＩＡｌＧｄＯ３の比（ＩＡｌＧｄＯ３／ＩＡｌＮ）が０．０３以下であり、且つ上記Ｘ線回折強度ＩＡｌＮに対するＧｄ２Ｏ３（４０１面）のＸ線回折強度ＩＧｄ２Ｏ３の比（ＩＧｄ２Ｏ３／ＩＡｌＮ）が０．００５〜０．０４であり、熱伝導率が２３５Ｗ／ｍ・Ｋ以上、三点曲げ強度が２００ＭＰａ以上であることを特徴とする。 Further, the second aspect of the high thermal conductivity of aluminum nitride sintered body according to the invention, X-ray diffraction intensity IAL 2 Gd of Al 2 Gd 4 O 9 with respect to the X-ray diffraction intensity IAlN aluminum nitride (101 plane) (310 plane) The ratio of 4 O 9 (IAI 2 Gd 4 O 9 / IALN) is 0.004 to 0.04, and the ratio of the X-ray diffraction intensity IAlGdO 3 of AlGdO 3 (112 plane) to the X-ray diffraction intensity IAlN (IAlGdO 3 ). 3 / IAIN) is 0.03 or less, and the ratio of X-ray diffraction intensity IGd 2 O 3 of Gd 2 O 3 (401 plane) to the X-ray diffraction intensity IAlN (IGd 2 O 3 / IAIN) is 0. The thermal conductivity is 235 W / m · K or more, and the three-point bending strength is 200 MPa or more.
さらに、本願第３の発明に係る高熱伝導性窒化アルミニウム焼結体は、窒化アルミニウム（１０１面）のＸ線回折強度ＩＡｌＮに対するＡｌ２Ｄｙ４Ｏ９（３２０面）のＸ線回折強度ＩＡｌ２Ｄｙ４Ｏ９の比（ＩＡｌ２Ｄｙ４Ｏ９／ＩＡｌＮ）が０．０４以下であり、上記Ｘ線回折強度ＩＡｌＮに対するＡｌＤｙＯ３（１２１面）のＸ線回折強度ＩＡｌＤｙＯ３の比（ＩＡｌＤｙＯ３／ＩＡｌＮ）が０．０５以下であり、且つ上記Ｘ線回折強度ＩＡｌＮに対するＤｙ２Ｏ３（２２２面）のＸ線回折強度ＩＤｙ２Ｏ３の比（ＩＤｙ２Ｏ３／ＩＡｌＮ）が０．００２〜０．０６であり、熱伝導率が２１５Ｗ／ｍ・Ｋ以上、三点曲げ強度が２５０ＭＰａ以上であることを特徴とする。 Further, the third aspect the high thermal conductivity of aluminum nitride sintered body according to the invention is, X-ray diffraction intensity IAL 2 Dy of Al 2 Dy 4 O 9 with respect to the X-ray diffraction intensity IAlN aluminum nitride (101 plane) (320 plane) The ratio of 4 O 9 (IAI 2 Dy 4 O 9 / IALN) is 0.04 or less, and the ratio of X-ray diffraction intensity IAlDyO 3 of AlDyO 3 (121 plane) to the X-ray diffraction intensity IAlN (IAlDyO 3 / IALN) ) is 0.05 or less, and the ratio of the X-ray diffraction intensity IDy 2 O 3 of Dy 2 O 3 with respect to the X-ray diffraction intensity IAlN (222 plane) (IDy 2 O 3 / IAlN ) is 0.002 to 0 0.06, a thermal conductivity of 215 W / m · K or more, and a three-point bending strength of 250 MPa or more.
また、本願第４の発明に係る高熱伝導性窒化アルミニウム焼結体は、窒化アルミニウム（１０１面）のＸ線回折強度ＩＡｌＮに対するＡｌ２Ｄｙ４Ｏ９（３２０面）のＸ線回折強度ＩＡｌ２Ｄｙ４Ｏ９の比（ＩＡｌ２Ｄｙ４Ｏ９／ＩＡｌＮ）が０．００４〜０．０４であり、上記Ｘ線回折強度ＩＡｌＮに対するＡｌＤｙＯ３（１２１面）のＸ線回折強度ＩＡｌＤｙＯ３の比（ＩＡｌＤｙＯ３／ＩＡｌＮ）が０．０３以下であり、且つ上記Ｘ線回折強度ＩＡｌＮに対するＤｙ２Ｏ３（２２２面）のＸ線回折強度ＩＤｙ２Ｏ３の比（ＩＤｙ２Ｏ３／ＩＡｌＮ）が０．００５〜０．０４であり、熱伝導率が２３５Ｗ／ｍ・Ｋ以上、三点曲げ強度が２００ＭＰａ以上であることを特徴とする。 Further, the present fourth high thermal conductivity aluminum nitride sintered body according to the invention is, X-ray diffraction intensity IAL 2 Dy of Al 2 Dy 4 O 9 with respect to the X-ray diffraction intensity IAlN aluminum nitride (101 plane) (320 plane) The ratio of 4 O 9 (IAI 2 Dy 4 O 9 / IALN) is 0.004 to 0.04, and the ratio of the X-ray diffraction intensity IAlDyO 3 of AlDyO 3 (121 plane) to the X-ray diffraction intensity IAlN (IADyO 3 ). 3 / IAIN) is 0.03 or less, and the ratio of Xy diffraction intensity IDy 2 O 3 of Dy 2 O 3 (222 plane) to X ray diffraction intensity IAlN (IDy 2 O 3 / IAIN) is 0. The thermal conductivity is 235 W / m · K or more, and the three-point bending strength is 200 MPa or more.
さらに、上記第１または第３の発明において、高熱伝導性窒化アルミニウム焼結体がＧｄ、Ｄｙ元素の少なくとも１種を０．３〜４．５質量％、酸素を０．１〜０．７５質量％含有し、酸素とＧｄ、Ｄｙ（Ｒｅ）元素との質量比率（Ｏ／Ｒｅ）が０．４以下であり、窒化アルミニウム結晶粒子の平均径が４μｍ以上であり、任意の結晶組織面積１００μｍ×１００μｍ当りに存在する結晶粒子数が４５０個以下であり、粒界相の最大径が０．７μｍ以下であることが好ましい。 Furthermore, in the first or third invention, the high thermal conductivity aluminum nitride sintered body is 0.3 to 4.5 mass% at least one of Gd and Dy elements, and 0.1 to 0.75 mass% of oxygen. %, The mass ratio (O / Re) of oxygen to Gd, Dy (Re) element is 0.4 or less, the average diameter of the aluminum nitride crystal particles is 4 μm or more, and an arbitrary crystal structure area of 100 μm × It is preferable that the number of crystal grains present per 100 μm is 450 or less and the maximum diameter of the grain boundary phase is 0.7 μm or less.
また上記第２または第４の発明において、高熱伝導性窒化アルミニウム焼結体がＧｄ、Ｄｙ元素の少なくとも１種を０．３〜３質量％、酸素を０．１〜０．６質量％含有し、酸素とＧｄ、Ｄｙ（Ｒｅ）元素との質量比率（Ｏ／Ｒｅ）が０．３以下であり、窒化アルミニウム結晶粒子の平均径が５μｍ以上であり、任意の結晶組織面積１００μｍ×１００μｍ当りに存在する結晶粒子数が３５０個以下であり、粒界相の最大径が０．６μｍ以下であることことが好ましい。 In the second or fourth invention, the high thermal conductivity aluminum nitride sintered body contains 0.3 to 3% by mass of at least one of Gd and Dy elements and 0.1 to 0.6% by mass of oxygen. , The mass ratio (O / Re) of oxygen to Gd, Dy (Re) element is 0.3 or less, the average diameter of aluminum nitride crystal particles is 5 μm or more, and per arbitrary crystal structure area of 100 μm × 100 μm It is preferable that the number of crystal grains present is 350 or less, and the maximum diameter of the grain boundary phase is 0.6 μm or less.
上記第１および第２の発明に係る高熱伝導性窒化アルミニウム焼結体において、焼結体を構成する主相は窒化アルミニウム（ＡｌＮ）である一方、副相となる粒界相は熱抵抗が低いＧｄ４Ａｌ２Ｏ９（ＧＡＭ）やＧｄＡｌＯ３（ＧＡＬ）やＧｄ２Ｏ３から成る相に限定される。上記ＧＡＭ相はＸ線回折分析においてＡｌ２Ｇｄ４Ｏ９（３１０面）の回折ピーク強度として同定・定量される一方、上記ＧＡＬ相はＸ線回折分析においてＧｄＡｌＯ３（１１２面）の回折ピーク強度として同定・定量される。同様にＧｄ２Ｏ３から成る相は、Ｘ線回折分析においてＧｄ２Ｏ３（４０１面）の回折ピーク強度として同定・定量される。粒界相にＧｄ３Ａｌ５Ｏ１２（ＧＡＧ）などの、熱抵抗が高い第３相を含む場合は、ＡｌＮ焼結体の熱伝導率が低下する。 In the high thermal conductivity aluminum nitride sintered body according to the first and second inventions, the main phase constituting the sintered body is aluminum nitride (AlN), while the grain boundary phase serving as the subphase has low thermal resistance. Gd 4 Al 2 O 9 is limited to the phase consisting of (GAM) or GdAlO 3 (GAL) or Gd 2 O 3. The GAM phase is identified and quantified as the diffraction peak intensity of Al 2 Gd 4 O 9 (310 plane) in X-ray diffraction analysis, while the GAL phase is the diffraction peak intensity of GdAlO 3 (112 plane) in X-ray diffraction analysis. As identified and quantified. Phase consisting Similarly Gd 2 O 3 are identified and quantified in the X-ray diffraction analysis as a diffraction peak intensity of Gd 2 O 3 (401 plane). When the grain boundary phase includes a third phase having a high thermal resistance such as Gd 3 Al 5 O 12 (GAG), the thermal conductivity of the AlN sintered body is lowered.
同様に上記第３および第４の発明に係る高熱伝導性窒化アルミニウム焼結体において、焼結体を構成する主相は窒化けい素（ＡｌＮ）である一方、副相となる粒界相は熱抵抗が低いＤｙ４Ａｌ２Ｏ９（ＤＡＭ）やＤｙＡｌＯ３（ＤＡＬ）やＤｙ２Ｏ３から成る相に限定される。上記ＤＡＭ相はＸ線回折分析においてＡｌ２Ｄｙ４Ｏ９（３２０面）の回折ピーク強度として同定・定量される一方、上記ＤＡＬ相はＸ線回折分析においてＤｙＡｌＯ３（１２１面）の回折ピーク強度として同定・定量される。同様にＤｙ２Ｏ３から成る相は、Ｘ線回折分析においてＤｙ２Ｏ３（２２２面）の回折ピーク強度として同定・定量される。粒界相にＤｙ３Ａｌ５Ｏ１２（ＤＡＧ）などの、熱抵抗が高い第３相を含む場合は、ＡｌＮ焼結体の熱伝導率が低下する。 Similarly, in the high thermal conductivity aluminum nitride sintered bodies according to the third and fourth inventions, the main phase constituting the sintered body is silicon nitride (AlN), while the grain boundary phase serving as the subphase is the heat. resistance is limited to the phase consisting of a lower Dy 4 Al 2 O 9 (DAM ) and DyAlO 3 (DAL) and Dy 2 O 3. The DAM phase is identified and quantified as the diffraction peak intensity of Al 2 Dy 4 O 9 (320 plane) in X-ray diffraction analysis, while the DAL phase is the diffraction peak intensity of DyAlO 3 (121 plane) in X-ray diffraction analysis. As identified and quantified. Phase consisting Similarly Dy 2 O 3 are identified and quantified in the X-ray diffraction analysis as a diffraction peak intensity of Dy 2 O 3 (222 plane). When the grain boundary phase includes a third phase having a high thermal resistance such as Dy 3 Al 5 O 12 (DAG), the thermal conductivity of the AlN sintered body is lowered.
上記第１から第４の発明に係る高熱伝導性窒化アルミニウム焼結体において、Ｘ線回折強度比（ＩＡｌ２Ｇｄ４Ｏ９／ＩＡｌＮ）または（ＩＡｌ２Ｄｙ４Ｏ９／ＩＡｌＮ）は上記ＧＡＭ相またはＤＡＭ相の生成割合を示すものであり、焼結体の熱伝導率および三点曲げ強度の要求特性に応じて０．０４以下の範囲または０．００４〜０．０４の範囲とされる。上記ＧＡＭ相またはＤＡＭ相のＸ線回折強度比が上記下限値未満になると、ＡｌＮ結晶粒子を相互に結合せしめる粒界相の機能が低下し焼結体の構造強度が低下する場合がある。一方、上記Ｘ線回折強度比が上限値を超えると熱抵抗が増加し、焼結体の熱伝導率が低下し易い。 In high thermal conductivity aluminum nitride sintered body according to the fourth aspect of the present invention from the first 1, X-ray diffraction intensity ratio (IAl 2 Gd 4 O 9 / IAlN) or (IAl 2 Dy 4 O 9 / IAlN) above GAM phase Or it shows the production | generation ratio of a DAM phase, It is set as the range of 0.04 or less or the range of 0.004-0.04 according to the thermal conductivity of a sintered compact, and the required characteristic of three-point bending strength. When the X-ray diffraction intensity ratio of the GAM phase or DAM phase is less than the lower limit, the function of the grain boundary phase for bonding the AlN crystal particles to each other may be lowered, and the structural strength of the sintered body may be lowered. On the other hand, when the X-ray diffraction intensity ratio exceeds the upper limit value, the thermal resistance increases and the thermal conductivity of the sintered body tends to decrease.
また窒化アルミニウム（１０１面）のＸ線回折強度ＩＡｌＮに対するＡｌＧｄＯ３の（１１２面）のＸ線回折強度ＩＡｌＧｄＯ３の比（ＩＡｌＧｄＯ３／ＩＡｌＮ）またはＡｌＤｙＯ３の（１２１面）のＸ線回折強度ＩＡｌＤｙＯ３の比（ＩＡｌＤｙＯ３／ＩＡｌＮ）は、焼結体の熱伝導率の要求特性に応じて０．０５以下の範囲または０．０３以下の範囲とされる。このＸ線回折強度比が上記上限値を超えると焼結体の熱伝導率が低下し易くなる。 The ratio of the X-ray diffraction intensity IAlGdO 3 of (112 plane) of AlGdO 3 to the X-ray diffraction intensity IAlN of aluminum nitride (101 plane) (IALGdO 3 / IALN) or the X-ray diffraction intensity IAlDyO of (121 plane) of AlDyO 3 The ratio of 3 (IA1DyO 3 / IA1N) is set to a range of 0.05 or less or 0.03 or less depending on the required characteristics of the thermal conductivity of the sintered body. If this X-ray diffraction intensity ratio exceeds the above upper limit, the thermal conductivity of the sintered body tends to decrease.
また、Ｇｄ２Ｏ３（４０１面）のＸ線回折強度ＩＧｄ２Ｏ３の窒化アルミニウム（１０１面）のＸ線回折強度ＩＡｌＮに対する比（ＩＧｄ２Ｏ３／ＩＡｌＮ）またはＤｙ２Ｏ３（２２２面）のＸ線回折強度ＩＤｙ２Ｏ３の窒化アルミニウム（１０１面）のＸ線回折強度ＩＡｌＮに対する比（ＩＤｙ２Ｏ３／ＩＡｌＮ）は、粒界相に析出したＧｄ２Ｏ３相またはＤｙ２Ｏ３相の生成割合を示すものであり、焼結体の熱伝導率および三点曲げ強度の要求特性に応じて０．００２〜０．０６の範囲または０．００５〜０．０４の範囲とされる。上記Ｇｄ２Ｏ３相またはＤｙ２Ｏ３相のＸ線回折強度比が上記下限値未満であると、焼結性の改善効果が不十分であり、焼結体の構造強度が低下したり、ＡｌＮ結晶中に酸素が固溶して熱伝導率が低下したりする。一方、上記Ｘ線回折強度比が上限値を超えると、焼結体中に気孔が残存して収縮率が減少し、熱伝導率が低下する。 Further, the ratio of X-ray diffraction intensity IGd 2 O 3 of Gd 2 O 3 (401 plane) to X-ray diffraction intensity IAlN of aluminum nitride (101 plane) (IGd 2 O 3 / IALN) or Dy 2 O 3 (222 plane) ) Of X-ray diffraction intensity IDy 2 O 3 of aluminum nitride (101 plane) to X-ray diffraction intensity IAlN (IDy 2 O 3 / IALN) is a Gd 2 O 3 phase or Dy 2 O precipitated in the grain boundary phase. It indicates the ratio of three- phase formation, and is in the range of 0.002 to 0.06 or 0.005 to 0.04 depending on the required properties of the thermal conductivity and three-point bending strength of the sintered body. The If the X-ray diffraction intensity ratio of the Gd 2 O 3 phase or the Dy 2 O 3 phase is less than the lower limit, the effect of improving the sinterability is insufficient, and the structural strength of the sintered body is reduced. Oxygen is dissolved in the AlN crystal and the thermal conductivity is lowered. On the other hand, when the X-ray diffraction intensity ratio exceeds the upper limit value, pores remain in the sintered body, the shrinkage rate decreases, and the thermal conductivity decreases.
上記Ｘ線回折強度比（ＩＡｌ２Ｇｄ４Ｏ９／ＩＡｌＮまたはＩＡｌ２Ｄｙ４Ｏ９／ＩＡｌＮ）を０．０４以下の範囲とし、Ｘ線回折強度比（ＩＡｌＧｄＯ３／ＩＡｌＮまたはＩＡｌＤｙＯ３／ＩＡｌＮ）を０．０５以下の範囲とし、且つＸ線回折強度比（ＩＧｄ２Ｏ３／ＩＡｌＮまたはＩＤｙ２Ｏ３／ＩＡｌＮ）を０．００２〜０．０６の範囲にした場合に、熱伝導率が２１５Ｗ／ｍ・Ｋ以上であり、三点曲げ強度が２５０ＭＰａ以上である窒化アルミニウム焼結体が得られ易い。 The X-ray diffraction intensity ratio (IAl 2 Gd 4 O 9 / IAlN or IAl 2 Dy 4 O 9 / IAlN ) was in the range of 0.04 or less, X-rays diffraction intensity ratio (IAlGdO 3 / IAlN or IAlDyO 3 / IAlN) When the X-ray diffraction intensity ratio (IGd 2 O 3 / IAIN or IDy 2 O 3 / IALN) is in the range of 0.002 to 0.06, the thermal conductivity is 215 W. / M · K or more, and an aluminum nitride sintered body having a three-point bending strength of 250 MPa or more is easily obtained.
また、上記Ｘ線回折強度比（ＩＡｌ２Ｇｄ４Ｏ９／ＩＡｌＮまたはＩＡｌ２Ｄｙ４Ｏ９／ＩＡｌＮ）を０．００４〜０．０４の範囲とし、Ｘ線回折強度比（ＩＡｌＧｄＯ３／ＩＡｌＮまたはＩＡｌＤｙＯ３／ＩＡｌＮ）を０．０３以下の範囲とし、且つＸ線回折強度比（ＩＧｄ２Ｏ３／ＩＡｌＮまたはＩＤｙ２Ｏ３／ＩＡｌＮ）を０．００５〜０．０４の範囲にした場合に、熱伝導率が２３５Ｗ／ｍ・Ｋ以上であり、三点曲げ強度が２００ＭＰａ以上である窒化アルミニウム焼結体が得られ易い。 Further, the X-ray diffraction intensity ratio (IAI 2 Gd 4 O 9 / IALN or IAl 2 Dy 4 O 9 / IALN) is in the range of 0.004 to 0.04, and the X-ray diffraction intensity ratio (IALGdO 3 / IALN or When IAlDyO 3 / IALN) is in the range of 0.03 or less and the X-ray diffraction intensity ratio (IGd 2 O 3 / IALN or IDy 2 O 3 / IAIN) is in the range of 0.005 to 0.04, An aluminum nitride sintered body having a thermal conductivity of 235 W / m · K or more and a three-point bending strength of 200 MPa or more is easily obtained.
Ｇｄ，Ｄｙ元素は、ＡｌＮ原料粉末に含まれる不純物酸素と反応して、Ｒｅ酸化物−アルミナ化合物（Ｒｅ４Ａｌ２Ｏ９）などから成る液相を形成し、焼結体の緻密化を達成する焼結助剤として作用するとともに、この不純物酸素を粒界相として固定し高熱伝導化も達成するために、第１，３の発明では０．３〜４．５質量％の範囲で含有され、第２，４の発明では０．３〜３質量％の範囲で含有される。 The Gd and Dy elements react with impurity oxygen contained in the AlN raw material powder to form a liquid phase composed of a Re oxide-alumina compound (Re 4 Al 2 O 9 ) and the like, thereby achieving densification of the sintered body. In order to act as a sintering aid and to fix this impurity oxygen as a grain boundary phase and to achieve high thermal conductivity, in the first and third inventions, it is contained in the range of 0.3 to 4.5 mass%. In the second and fourth inventions, it is contained in the range of 0.3 to 3% by mass.
特に、熱伝導率が２１５Ｗ／ｍ・Ｋ以上であり、三点曲げ強度が２５０ＭＰａ以上である高強度高熱伝導性窒化アルミニウム焼結体を得るためには、Ｇｄ、Ｄｙ元素の少なくとも１種を０．３〜４．５質量％、酸素を０．１〜０．７５質量％含有させることが必要である。 In particular, in order to obtain a high-strength, high-thermal-conductivity aluminum nitride sintered body having a thermal conductivity of 215 W / m · K or more and a three-point bending strength of 250 MPa or more, at least one of Gd and Dy elements is changed to 0. It is necessary to contain 0.3 to 4.5% by mass and 0.1 to 0.75% by mass of oxygen.
また、熱伝導率が２３５Ｗ／ｍ・Ｋ以上であり、三点曲げ強度が２００ＭＰａ以上である高熱伝導性窒化アルミニウム焼結体を得るためには、Ｇｄ、Ｄｙ元素の少なくとも１種を０．３〜３質量％、酸素を０．１〜０．６質量％含有させることが必要である。 Further, in order to obtain a highly thermally conductive aluminum nitride sintered body having a thermal conductivity of 235 W / m · K or more and a three-point bending strength of 200 MPa or more, at least one of Gd and Dy elements is changed to 0.3. It is necessary to contain ˜3 mass% and oxygen 0.1 to 0.6 mass%.
このＧｄ、Ｄｙ元素の含有量が上記下限値未満の場合は、焼結性の改善効果が充分に発揮されず、焼結体が緻密化されず低強度の焼結体が形成されたり、ＡｌＮ結晶中に酸素が固溶し、高い熱伝導率を有する焼結体が形成できない。一方、含有量が上記上限値を超える過量となると、過量の粒界相が焼結体中に残存したり、熱処理により除去される粒界相の体積が大きいため、焼結体中に空孔（気孔）が残ったりして収縮率が減少し、焼結体の熱伝導率が低下してしまう。 When the content of the Gd and Dy elements is less than the above lower limit value, the effect of improving the sinterability is not sufficiently exhibited, the sintered body is not densified and a low strength sintered body is formed, AlN Oxygen is dissolved in the crystal, and a sintered body having high thermal conductivity cannot be formed. On the other hand, if the content exceeds the above upper limit, excessive grain boundary phases remain in the sintered body or the volume of the grain boundary phase removed by heat treatment is large, so there are voids in the sintered body. (Porosity) remains, shrinkage rate decreases, and thermal conductivity of the sintered body decreases.
一方、酸素（Ｏ）は上記粒界相を形成する成分であり、上記熱伝導率および三点曲げ強度の要求度合いに応じてＡｌＮ焼結体中に０．１〜０．７５質量％の範囲で含有される。上記酸素含有量が上記下限値未満の場合には、粒界相の形成割合が少なくなり、粒界相のよるＡｌＮ結晶粒を相互に結合する効果が減少し、ＡｌＮ焼結体全体の構造強度が低下してしまう。すなわち、前記Ｒｅ成分および酸素からなる液相は焼結後においてＡｌＮ結晶粒の粒界部にガラス質または結晶質として凝固して粒界相を形成し、この粒界相がＡｌＮ結晶粒を相互に強固に結合せしめＡｌＮ焼結体全体の構造強度を高める。 On the other hand, oxygen (O) is a component that forms the grain boundary phase, and is in the range of 0.1 to 0.75% by mass in the AlN sintered body depending on the required degree of thermal conductivity and three-point bending strength. Contained. When the oxygen content is less than the lower limit, the formation ratio of the grain boundary phase is reduced, the effect of bonding AlN crystal grains due to the grain boundary phase is reduced, and the structural strength of the entire AlN sintered body is reduced. Will fall. That is, the liquid phase composed of the Re component and oxygen solidifies as a vitreous or crystalline material at the grain boundary portion of the AlN crystal grains after sintering to form a grain boundary phase. And the structural strength of the entire AlN sintered body is increased.
しかしながら、酸素含有量が上記上限値を超える過量になると、熱抵抗が高い粒界相の割合が相対的に増加するために、焼結体の熱伝導率が低下する。また、過量の粒界相が焼結体中に残存したり、熱処理により除去される粒界相の体積が大きいため、焼結体中に空孔（気孔）が残ったりして収縮率が増大し、変形を生じ易くなる。 However, when the oxygen content exceeds the upper limit, the ratio of the grain boundary phase having a high thermal resistance is relatively increased, so that the thermal conductivity of the sintered body is lowered. In addition, an excessive amount of grain boundary phase remains in the sintered body, or the volume of the grain boundary phase removed by heat treatment is large, so voids (pores) remain in the sintered body and the shrinkage rate increases. However, deformation is likely to occur.
また、本発明に係る高熱伝導性窒化アルミニウム焼結体において、酸素とＲｅ元素（Ｇｄ，Ｄｙ）との質量比率（Ｏ／Ｒｅ）は０．４以下とすることが好ましい。この質量比率（Ｏ／Ｒｅ）が０．４を超えるように過大になると、熱抵抗が高い酸素化合物が多くなり、焼結体の熱伝導率が低下する。この質量比率（Ｏ／Ｒｅ）は０．３以下であることがさらに好ましい。 In the high thermal conductivity aluminum nitride sintered body according to the present invention, the mass ratio (O / Re) of oxygen and Re element (Gd, Dy) is preferably 0.4 or less. If this mass ratio (O / Re) is excessively greater than 0.4, oxygen compounds having high thermal resistance increase, and the thermal conductivity of the sintered body decreases. The mass ratio (O / Re) is more preferably 0.3 or less.
さらに、本発明に係る高熱伝導性窒化アルミニウム焼結体において、ＡｌＮ結晶粒子の平均粒子径は、好ましくは４μｍ以上、さらに好ましくは５μｍ以上とすると良い。これはＡｌＮ結晶の粒成長によって結晶粒子が粗大化することによって、熱抵抗が大きい粒界相の数を相対的に減少させることが可能になり、焼結体の熱伝導率を向上させることができるからである。 Furthermore, in the high thermal conductivity aluminum nitride sintered body according to the present invention, the average particle diameter of the AlN crystal particles is preferably 4 μm or more, more preferably 5 μm or more. This is because the number of grain boundary phases having a large thermal resistance can be relatively reduced due to the coarsening of the crystal grains due to the grain growth of the AlN crystal, and the thermal conductivity of the sintered body can be improved. Because it can.
また、本発明に係る高熱伝導性窒化アルミニウム焼結体において、ＡｌＮ焼結体の粒界相の最大径は、熱伝導率の要求特性に応じて０．７μｍ以下、好ましくは０．６μｍ以下に規定される。上記粒界相の最大径が上記上限値を超えるようになると、熱抵抗となる粒界相の割合が相対的に増加することになり、焼結体の熱伝導率が低下してしまう。 In the high thermal conductivity aluminum nitride sintered body according to the present invention, the maximum diameter of the grain boundary phase of the AlN sintered body is 0.7 μm or less, preferably 0.6 μm or less, depending on the required characteristics of thermal conductivity. It is prescribed. When the maximum diameter of the grain boundary phase exceeds the upper limit, the ratio of the grain boundary phase that becomes thermal resistance is relatively increased, and the thermal conductivity of the sintered body is lowered.
特に、窒化アルミニウム結晶粒子の平均径を４μｍ以上、粒界相の最大径を０．７μｍ以下とし、任意の結晶組織面積１００μｍ×１００μｍ当りに存在する結晶粒子数を４５０個以下とすることにより、熱伝導率が２１５Ｗ／ｍ・Ｋ以上であり、三点曲げ強度が２５０ＭＰａ以上である高熱伝導性窒化アルミニウム焼結体が得られ易くなる。 In particular, the average diameter of the aluminum nitride crystal particles is 4 μm or more, the maximum diameter of the grain boundary phase is 0.7 μm or less, and the number of crystal grains existing per arbitrary crystal structure area 100 μm × 100 μm is 450 or less, A high thermal conductivity aluminum nitride sintered body having a thermal conductivity of 215 W / m · K or more and a three-point bending strength of 250 MPa or more is easily obtained.
一方、窒化アルミニウム結晶粒子の平均径を５μｍ以上、粒界相の最大径を０．６μｍ以下とし、任意の結晶組織面積１００μｍ×１００μｍ当りに存在する結晶粒子数を３５０個以下とすることにより、熱伝導率が２３５Ｗ／ｍ・Ｋ以上、三点曲げ強度が２００ＭＰａ以上である高熱伝導性窒化アルミニウム焼結体が得られ易くなる。 On the other hand, the average diameter of aluminum nitride crystal particles is 5 μm or more, the maximum diameter of the grain boundary phase is 0.6 μm or less, and the number of crystal grains existing per arbitrary crystal structure area 100 μm × 100 μm is 350 or less, A highly heat-conductive aluminum nitride sintered body having a thermal conductivity of 235 W / m · K or more and a three-point bending strength of 200 MPa or more is easily obtained.
上記窒化アルミニウム結晶粒子の単位結晶組織面積当たりに存在する粒子数が上記上限値を超えると、構造強度はやや増加するが、粒界相の存在数が増加するため、焼結体の熱伝導性が低下してしまう。 If the number of particles present per unit crystal structure area of the aluminum nitride crystal particles exceeds the upper limit, the structural strength slightly increases, but the number of grain boundary phases increases, so the thermal conductivity of the sintered body increases. Will fall.
ここで、上記窒化アルミニウム結晶粒子の平均径および粒界相の最大径は、以下のように測定できる。すなわち、各ＡｌＮ焼結体から切り出した５ｍｍ×１０ｍｍ×０．６ｍｍまたは４ｍｍ×４ｍｍ×１０ｍｍの試料片の断面組織から１００μｍ×１００μｍの領域を有する３箇所の測定領域を選定し、各領域を倍率が１０００〜４０００倍であるＳＥＭにて観察し、その組織影像から測定される。なお測定対象は各粒子全体が現れている粒子および３重点全体が現れている粒界相に限定する。 Here, the average diameter of the aluminum nitride crystal particles and the maximum diameter of the grain boundary phase can be measured as follows. That is, three measurement regions having a region of 100 μm × 100 μm are selected from a cross-sectional structure of a sample piece of 5 mm × 10 mm × 0.6 mm or 4 mm × 4 mm × 10 mm cut out from each AlN sintered body, and each region is magnified. Is observed with a SEM having a magnification of 1000 to 4000, and is measured from the tissue image. Note that the measurement target is limited to particles in which the entire particles appear and grain boundary phases in which the entire triple point appears.
具体的には、各窒化アルミニウム結晶粒子の直径は、ＡｌＮ結晶粒子に外接する最小円の直径で測定される一方、粒界相の直径は、ＡｌＮ焼結体の断面結晶組織に存在する粒界相の三重点等に内接する最大円の直径で測定される。そして、本発明における粒界相の最大径は、上記３領域に存在する粒界直径の最大値を示す。一方、窒化アルミニウム結晶粒子の平均径は、上記３領域に存在する全ＡｌＮ結晶粒の直径の平均値を示す。 Specifically, the diameter of each aluminum nitride crystal particle is measured by the diameter of the smallest circle circumscribing the AlN crystal particle, while the diameter of the grain boundary phase is the grain boundary existing in the cross-sectional crystal structure of the AlN sintered body. It is measured by the diameter of the largest circle inscribed in the triple point of the phase. And the maximum diameter of the grain boundary phase in this invention shows the maximum value of the grain boundary diameter which exists in said 3 area | region. On the other hand, the average diameter of the aluminum nitride crystal particles indicates the average value of the diameters of all AlN crystal grains present in the three regions.
上記粒界相の最大径が０．７μｍを超えるように液相の凝集偏析が著しくなると、ＡｌＮ結晶粒子相互の液相による結合作用が低下し焼結体全体としての強度が低下し易くなると同時に粗大な粒界相は熱伝導の妨げとなり、ＡｌＮ焼結体の熱伝導率を低下させる。 When the aggregation segregation of the liquid phase becomes significant so that the maximum diameter of the grain boundary phase exceeds 0.7 μm, the bonding action of the AlN crystal particles with each other in the liquid phase is lowered, and the strength as a whole of the sintered body is easily lowered. The coarse grain boundary phase hinders heat conduction and lowers the thermal conductivity of the AlN sintered body.
本発明に係る高熱伝導性窒化アルミニウム焼結体の製造方法は、例えば酸素量が１質量％以下、平均粒径１．５μｍ以下の窒化アルミニウム粉末にＲｅ元素（Ｇｄ，Ｄｙ）を０．３〜４．５質量％と酸素を０．１〜０．７５質量％と有機バインダーとを添加した原料混合体を成形して成形体を調製し、得られた成形体を脱脂して成形体中に残留する炭素量が０．３〜０．６質量％の範囲になるように制御した後に、非酸化性雰囲気中で仮焼処理を実施し、しかる後に本焼結する方法が採用できる。 In the method for producing a highly heat-conductive aluminum nitride sintered body according to the present invention, for example, the amount of oxygen is 1% by mass or less, and an aluminum nitride powder having an average particle size of 1.5 μm or less contains Re element (Gd, Dy) of 0.3 to A raw material mixture to which 4.5% by mass, oxygen of 0.1 to 0.75% by mass and an organic binder are added is molded to prepare a molded body, and the obtained molded body is degreased into the molded body. After controlling so that the amount of remaining carbon may be in the range of 0.3 to 0.6% by mass, a calcination treatment is performed in a non-oxidizing atmosphere, and then a main sintering method can be employed.
特に上記製法において、Ｒｅ元素の酸化物等により焼結時に形成された液相が凝固する温度までに至る焼結体の冷却速度を毎時１５０℃以下にして徐冷することにより、気孔を微細化できるとともに、窒化アルミニウムの結晶組織をより微細かつ均一に形成することができる。 In particular, in the above manufacturing method, the pores are refined by gradually cooling the sintered body to a temperature at which the liquid phase formed during sintering is solidified by oxides of Re element or the like to a temperature at which the liquid phase is solidified. In addition, the crystal structure of aluminum nitride can be formed more finely and uniformly.
本発明方法において使用され、焼結体の主成分となる窒化アルミニウム（ＡｌＮ）粉末としては、焼結性および熱伝導性を考慮して不純物酸素含有量が１質量％以下、好ましくは０．７質量％以下に抑制され、平均粒径が０．０５〜１．５μｍ程度、好ましくは１μｍ以下のものを使用する。使用する窒化アルミニウム（ＡｌＮ）粉末の平均粒径が１．５μｍを超える場合は、焼結性が劣るために長時間または高温度での焼結が必要となり、焼結体の機械的強度も低下するために好ましくない。 The aluminum nitride (AlN) powder used in the method of the present invention and serving as the main component of the sintered body has an impurity oxygen content of 1% by mass or less, preferably 0.7% in consideration of sinterability and thermal conductivity. A material having a mean particle size of about 0.05 to 1.5 μm, preferably 1 μm or less is used. If the average particle size of the aluminum nitride (AlN) powder used exceeds 1.5 μm, the sintering will be inferior, so it will be necessary to sinter for a long time or at a high temperature, and the mechanical strength of the sintered body will also decrease This is not preferable.
また、本発明で使用し得る有機バインダー（結合剤）としては、何ら限定されるものではなく、一般にセラミックス粉末の成形に使用されるポリビニルブチラール、ポリメチルメタクリレート等の有機高分子系結合材が好適に使用できる。 In addition, the organic binder (binder) that can be used in the present invention is not limited at all, and organic polymer binders such as polyvinyl butyral and polymethyl methacrylate generally used for forming ceramic powder are suitable. Can be used for
前記の通り、Ｇｄ，Ｄｙ元素は焼結助剤成分として０．３〜４．５質量％の割合で窒化アルミニウム原料粉末に添加される。焼結助剤の具体例としてはＧｄ，Ｄｙの酸化物、もしくは焼結操作によりこれらの化合物となる物質（炭酸塩等）が単独で、または２種以上混合して使用され、特に酸化ガドリニウム（Ｇｄ２Ｏ３）や酸化ジスプロシウム（Ｄｙ２Ｏ３）が好ましい。これらの焼結助剤は、窒化アルミニウムの原料粉末表面のアルミニウム酸化物相と反応してＲｅ４Ａｌ２Ｏ９、Ｒｅ２Ｏ３、およびＲｅＡｌＯ３などの複合酸化物の液相を形成し、この液相が焼結体の高密度化（緻密化）をもたらす。Ｇｄ２Ｏ３やＤｙ２Ｏ３を焼結助剤として用いた場合、アルミン酸ガドリニウムやアルミン酸ジスプロシウムが生成し液相焼結が進行すると考えられる。これらの焼結助剤を添加して常圧焼結すると、焼結性の向上（緻密化）のみではなく、熱伝導率も向上できる。すなわち焼結時にＡｌＮ中に固溶していた不純物酸素がＧｄ２Ｏ３やＤｙ２Ｏ３と反応して結晶粒界の酸化物相として偏析するため、格子欠陥の少ない焼結体が得られ、熱伝導率が向上する。 As described above, the Gd and Dy elements are added to the aluminum nitride raw material powder in a proportion of 0.3 to 4.5% by mass as a sintering aid component. Specific examples of the sintering aid include Gd and Dy oxides, or substances (such as carbonates) that become these compounds by a sintering operation, or a mixture of two or more, and particularly gadolinium oxide ( Gd 2 O 3 ) and dysprosium oxide (Dy 2 O 3 ) are preferred. These sintering aids react with the aluminum oxide phase on the surface of the aluminum nitride raw material powder to form a liquid phase of a composite oxide such as Re 4 Al 2 O 9 , Re 2 O 3 , and ReAlO 3 , This liquid phase leads to higher density (densification) of the sintered body. When Gd 2 O 3 or Dy 2 O 3 is used as a sintering aid, it is considered that gadolinium aluminate or dysprosium aluminate is generated and liquid phase sintering proceeds. When these sintering aids are added and atmospheric pressure sintering is performed, not only the sinterability is improved (densification) but also the thermal conductivity can be improved. In other words, impurity oxygen that was dissolved in AlN during sintering reacts with Gd 2 O 3 and Dy 2 O 3 to segregate as an oxide phase at the grain boundary, so that a sintered body with few lattice defects can be obtained. , The thermal conductivity is improved.
次に上記窒化アルミニウム焼結体を製造する場合の概略工程について説明する。すなわち酸素含有量を規定した所定粒径の窒化アルミニウム粉末に、所定量の焼結助剤としてのＧｄ，Ｄｙ化合物，酸素成分および有機バインダー、必要に応じて非晶質炭素等の必要な添加剤を加えて原料混合体を調製し、次に得られた原料混合体を成形して所定形状の成形体を得る。原料混合体の成形法としては、汎用の金型プレス法、冷間静水圧プレス（ＣＩＰ）法、あるいはドクターブレード法、ロール成形法のようなシート成形法などが適用できる。 Next, a schematic process for manufacturing the aluminum nitride sintered body will be described. In other words, a predetermined amount of Gd, Dy compound, oxygen component and organic binder as a sintering aid, and an optional additive such as amorphous carbon, if necessary, to an aluminum nitride powder having a predetermined particle size that defines the oxygen content Is added to prepare a raw material mixture, and then the obtained raw material mixture is molded to obtain a molded body having a predetermined shape. As a forming method of the raw material mixture, a general-purpose mold pressing method, a cold isostatic pressing (CIP) method, or a sheet forming method such as a doctor blade method or a roll forming method can be applied.
上記成形操作に引き続いて、成形体を非酸化性雰囲気中、例えば窒素ガス雰囲気中で温度５００〜８００℃で１〜４時間加熱して、予め添加していた大部分の有機バインダーの脱脂・除去を行い、成形体に残存する炭素量を厳密に調整する。 Following the above molding operation, the molded body is heated in a non-oxidizing atmosphere, for example, in a nitrogen gas atmosphere at a temperature of 500 to 800 ° C. for 1 to 4 hours to degrease and remove most of the organic binder added in advance. And the amount of carbon remaining in the molded body is strictly adjusted.
次に脱脂処理された成形体は、窒素ガス（Ｎ２）等の非酸化性雰囲気または減圧雰囲気中で温度１３００〜１５５０℃に加熱し１〜８時間保持する仮焼処理を実施する。この仮焼処理により、成形体に残留していた炭素と酸素成分とが効果的に結合して成形体外に蒸発飛散し、緻密化に必要な粒界相を形成するための最少量の酸素を残して酸素含有量が低減される。 Next, the degreased shaped body is subjected to a calcination treatment in which the temperature is maintained at 1300 to 1550 ° C. for 1 to 8 hours in a non-oxidizing atmosphere such as nitrogen gas (N 2 ) or a reduced pressure atmosphere. By this calcination treatment, carbon and oxygen components remaining in the molded body are effectively combined and evaporated and scattered outside the molded body, and a minimum amount of oxygen for forming a grain boundary phase necessary for densification is obtained. The oxygen content is reduced.
上記仮焼処理を実施しない場合には、脱酸に有効に働く残存炭素が酸素と結合して蒸発飛散しないため、添加したＲｅ２Ｏ３が還元窒化されＲｅＮを生成したり、炭素がそのまま残存して緻密化を阻害したりする。 In the case where the calcination treatment is not performed, the remaining carbon that effectively works for deoxidation is combined with oxygen and does not scatter and evaporate. Therefore, the added Re 2 O 3 is reduced and nitrided to generate ReN, or the carbon remains as it is. And inhibit densification.
上記脱脂処理後において、すなわち本焼結前の段階において、成形体に残留する炭素量が０．３〜０．６質量％の範囲になるように制御することが重要である。 It is important to control the amount of carbon remaining in the compact after the degreasing treatment, that is, before the main sintering, in a range of 0.3 to 0.6 mass%.
なお、上記脱脂処理した成形体に残存する炭素量は、炭素分析装置（ＥＭＩＡ−５２１、堀場製作所製）を用いて測定できる。 The amount of carbon remaining in the degreased molded body can be measured using a carbon analyzer (EMIA-521, manufactured by Horiba, Ltd.).
上記成形体に残留する炭素量が０．３質量％未満の場合には、後工程である焼結工程において、残留炭素が酸素と結合して蒸発飛散する炭素量が適正量より少ないため、焼結体中の酸素成分量が多くなり、熱伝導率が低下してしまう。一方、上記残留炭素量が０．６質量％を超えるように過大になると、焼結時においても炭素がそのまま残存して焼結体の緻密化が阻害される。 When the amount of carbon remaining in the molded body is less than 0.3% by mass, the amount of carbon that evaporates and scatters due to the residual carbon combined with oxygen in the subsequent sintering step is less than the appropriate amount. The amount of oxygen component in the bonded body increases and the thermal conductivity decreases. On the other hand, if the amount of residual carbon is excessive so as to exceed 0.6% by mass, carbon remains as it is even during sintering, and densification of the sintered body is hindered.
仮焼処理された成形体は、次に焼成容器内に収容され焼成炉内において多段に積層され、この配置状態で複数の成形体は一括して所定温度で焼結される。焼結操作は、窒素ガスなどの非酸化性雰囲気で成形体を温度１８００〜１９５０℃に８〜１８時間程度加熱して実施される。焼結雰囲気は、窒素ガス雰囲気、または窒素ガスを含む還元性雰囲気で行なう。還元性ガスとしてはＨ２ガス、ＣＯガスを使用してもよい。なお、焼結操作は真空（僅かな還元雰囲気を含む）、減圧、加圧および常圧を含む雰囲気中で実施してもよい。焼結温度が１８００℃未満と低温状態で焼成すると、原料粉末の粒径、含有酸素量によって異なるが、緻密な焼結体が得にくい一方、１９５０℃より高温度で焼成すると、焼成炉内におけるＡｌＮ自体の蒸気圧が高くなり緻密化が困難になるおそれがあるため、焼結温度は上記範囲に制御すべきである。 The calcined molded body is then accommodated in a firing container and stacked in multiple stages in a firing furnace, and in this arrangement, the plurality of molded bodies are collectively sintered at a predetermined temperature. The sintering operation is performed by heating the compact to a temperature of 1800 to 1950 ° C. for about 8 to 18 hours in a non-oxidizing atmosphere such as nitrogen gas. The sintering atmosphere is a nitrogen gas atmosphere or a reducing atmosphere containing nitrogen gas. As the reducing gas, H 2 gas or CO gas may be used. The sintering operation may be performed in an atmosphere including vacuum (including a slight reducing atmosphere), reduced pressure, increased pressure, and normal pressure. When sintered at a low temperature of less than 1800 ° C., it varies depending on the particle size of the raw material powder and the amount of oxygen contained, but it is difficult to obtain a dense sintered body, whereas when sintered at a temperature higher than 1950 ° C., Since the vapor pressure of AlN itself is high and densification may be difficult, the sintering temperature should be controlled within the above range.
なお、上記仮焼処理と焼結操作とは、それぞれ別の加熱炉を使用して非連続的に実施することも可能であるが、仮焼処理と焼結操作とを同一の焼成炉を使用して連続的に実施した方が工業規模での量産性に優れるため好ましい。 The calcination treatment and the sintering operation can be performed discontinuously using separate heating furnaces, but the calcination treatment and the sintering operation are performed using the same firing furnace. Therefore, it is preferable to carry it out continuously because it is excellent in mass productivity on an industrial scale.
上記焼結操作において緻密な焼結体を得るためにも、また焼結体の熱伝導率を向上させるためにも、ある程度の焼結助剤の添加は必要である。しかしながら、焼結助剤はＡｌＮや不純物酸素と反応して３Ｇｄ２Ｏ３・５Ａｌ２Ｏ３，Ｇｄ２Ｏ３・Ａｌ２Ｏ３や３Ｄｙ２Ｏ３・５Ａｌ２Ｏ３，Ｄｙ２Ｏ３・Ａｌ２Ｏ３などの酸化物を形成して粒界相に析出する。これら粒界相の酸化物は熱伝導を妨げる作用を有することが確認されている。したがって過剰量の粒界相が形成されないように焼結助剤の添加量は厳正に管理する必要がある。 In order to obtain a dense sintered body in the sintering operation and to improve the thermal conductivity of the sintered body, it is necessary to add a certain amount of sintering aid. However, the sintering aid 3Gd 2 O 3 · 5Al 2 O 3, Gd 2 O 3 · Al 2 O 3 and 3Dy 2 O 3 · 5Al 2 O 3 reacts with AlN and impurities oxygen, Dy 2 O 3 · An oxide such as Al 2 O 3 is formed and precipitated in the grain boundary phase. It has been confirmed that these grain boundary phase oxides have the effect of hindering heat conduction. Therefore, it is necessary to strictly control the addition amount of the sintering aid so that an excessive amount of grain boundary phase is not formed.
上記のように窒化アルミニウム結晶組織に形成される粒界相の最大径を０．７μｍ以下にしたり、またＡｌＮ結晶粒子を微細化したり、所定のアルミン酸ガドリニウムやアルミン酸ジスプロシウム等から成る粒界相を形成したり、焼結体の気孔を微細化するためには、焼結操作完了直後における焼結体の冷却速度を毎時１５０℃以下に制御して徐冷することが好ましい。上記冷却速度を毎時１５０℃を超えるように高速度に設定した場合には、焼結体に生成した液相が粒界部に凝集偏析し易く、粗大な粒界相および気孔が形成されたり、焼結体表面に粒界成分の滲み出しにより縞模様や亀の子状の模様が形成されて外観不良が発生し易い。 As described above, the maximum grain boundary phase formed in the aluminum nitride crystal structure is 0.7 μm or less, the AlN crystal grains are refined, or the grain boundary phase is made of predetermined gadolinium aluminate, dysprosium aluminate, etc. In order to form the pores and to make the pores of the sintered body finer, it is preferable that the cooling rate of the sintered body immediately after the completion of the sintering operation is controlled to 150 ° C./hour or less and gradually cooled. When the cooling rate is set to a high speed so as to exceed 150 ° C. per hour, the liquid phase generated in the sintered body is easily aggregated and segregated at the grain boundary part, and coarse grain boundary phases and pores are formed, Stripe patterns and turtle-like patterns are formed on the surface of the sintered body due to the exudation of grain boundary components, and appearance defects tend to occur.
特に焼結完了後に焼成炉の加熱用電源をＯＦＦして炉冷を実施した場合には、冷却速度は毎時４００〜５００℃となる。このように、焼結後に急冷した場合には焼結助剤により生成した液相の凝集偏析によるシマ模様などが発生し、焼結体の均質性が損なわれるだけでなく熱伝導率も低下する。そのため、焼結後に毎時１５０℃以下の降温速度で液相が凝固する温度まで冷却するが、毎時１２０℃以下の徐冷速度がより好ましい。 In particular, when the furnace is cooled by turning off the heating power source after the sintering is completed, the cooling rate is 400 to 500 ° C. per hour. In this way, when quenched after sintering, a striped pattern due to agglomeration and segregation of the liquid phase generated by the sintering aid occurs, which not only impairs the homogeneity of the sintered body but also reduces the thermal conductivity. . Therefore, although it cools to the temperature which a liquid phase solidifies with a temperature-fall rate of 150 degrees C or less after sintering, the slow cooling rate of 120 degrees C or less is more preferable.
上記冷却速度を調節する温度範囲は、所定の焼結温度（１８００〜１９５０℃）から、前記の焼結助剤の反応によって生じる液相が凝固するまでの温度（液相凝固点）までで充分である。前記のような焼結助剤を使用した場合の液相凝固点は概略１６５０〜１５００℃程度である。こうして少なくとも焼結温度から液相凝固点に至るまでの焼結体の冷却速度を毎時１５０℃以下に制御することにより、微細な粒界相がＡｌＮ結晶粒周囲に均一に分布し、気孔の形成が少ない焼結体が得られる。 The temperature range for adjusting the cooling rate is sufficient from a predetermined sintering temperature (1800 to 1950 ° C.) to a temperature (liquid phase freezing point) until the liquid phase generated by the reaction of the sintering aid is solidified. is there. The liquid phase freezing point when the above sintering aid is used is about 1650 to 1500 ° C. In this way, by controlling the cooling rate of the sintered body at least from the sintering temperature to the liquidus freezing point to 150 ° C. or less per hour, fine grain boundary phases are uniformly distributed around the AlN crystal grains, and pores are formed. A few sintered bodies can be obtained.
上記製法によって製造された窒化アルミニウム焼結体は、いずれも多結晶体として非常に高い２１５ｗ／ｍ・Ｋ（２５℃）以上、好ましくは２３５ｗ／ｍ・Ｋ以上の熱伝導率を有し、また三点曲げ強度も２００ＭＰａ以上、好ましくは２５０ＭＰａ以上であり機械的強度特性にも優れている。 Each of the aluminum nitride sintered bodies produced by the above-described production method has a very high thermal conductivity of 215 w / m · K (25 ° C.) or higher, preferably 235 w / m · K or higher, as a polycrystal. The three-point bending strength is also 200 MPa or more, preferably 250 MPa or more, and is excellent in mechanical strength characteristics.
上記構成に係る窒化アルミニウム焼結体によれば、焼結助剤としてのＧｄ，Ｄｙ元素添加量および酸素成分量を緻密化に必要な最少量に抑制し、熱伝導率の阻害要因である酸素を除去するために緻密化焼結前に脱酸熱処理工程を実施し、焼結後の粒界相を熱抵抗が低いＲｅ４Ａｌ２Ｏ９、Ｒｅ２Ｏ３、およびＲｅＡｌ２Ｏ３（但し、ＲｅはＧｄおよびＤｙの少なくとも一方の元素）の少なくとも１種に限定しているため、焼結体中の不純物酸素量が大幅に減少し、２１５Ｗ／ｍ・Ｋ以上の高熱伝導率を有する窒化アルミニウム焼結体が量産性良く得られる。 According to the aluminum nitride sintered body according to the above configuration, the amount of Gd and Dy elements added as a sintering aid and the amount of oxygen component are suppressed to the minimum amount necessary for densification, and oxygen is an impediment to thermal conductivity. In order to remove the heat treatment, a deoxidation heat treatment step is performed before densification sintering, and the grain boundary phase after sintering is subjected to Re 4 Al 2 O 9 , Re 2 O 3 , and ReAl 2 O 3 (provided that the thermal resistance is low). , Re is limited to at least one of Gd and Dy), the amount of impurity oxygen in the sintered body is greatly reduced, and nitriding has a high thermal conductivity of 215 W / m · K or more. An aluminum sintered body can be obtained with high productivity.
また、本発明の焼結体を製造する際に、特に焼結処理完了直後における焼結体の冷却速度を毎時１５０℃以下と小さく設定した場合には、炉冷のような急速冷却を実施した場合と異なり、焼結時に生成した液相の凝集偏析が少なく、微細な粒界相が均一に分布した結晶組織が得られる。また結晶組織に形成される気孔も微細化すると同時に減少させることができる。したがって、粗大な粒界相や気孔によって熱伝達や緻密化が阻害されることが少なく、高強度で高い熱伝導率を有する窒化アルミニウム焼結体が得られる。 Further, when the sintered body of the present invention was manufactured, rapid cooling such as furnace cooling was performed particularly when the cooling rate of the sintered body immediately after completion of the sintering treatment was set to 150 ° C. or less per hour. Unlike the case, there is little aggregation and segregation of the liquid phase produced during sintering, and a crystal structure in which fine grain boundary phases are uniformly distributed can be obtained. In addition, the pores formed in the crystal structure can be reduced at the same time as they are refined. Therefore, heat transfer and densification are hardly inhibited by coarse grain boundary phases and pores, and an aluminum nitride sintered body having high strength and high thermal conductivity can be obtained.
次に本発明の実施形態を以下に示す実施例を参照して具体的に説明する。 Next, the embodiments of the present invention will be specifically described with reference to the following examples.
［実施例１〜１５］
不純物として酸素を０．８質量％含有し、平均粒径１．０μｍの窒化アルミニウム粉末に対して、焼結助剤としての平均粒径０．８μｍのＧｄ２Ｏ３（酸化ガドリニウム）またはＤｙ２Ｏ３（酸化ジスプロシウム）とを表１に示すＧｄ，Ｄｙ元素量および酸素量となるように添加し、エチルアルコール中で３０時間湿式混合した後に乾燥して原料粉末混合体を調製した。さらにこの原料混合体１００重量部に対して有機バインダーとしてのブチルメタクリレートを１２重量部添加し、ボールミル混合を十分に実施した。
[Examples 1 to 15]
Gd 2 O 3 (gadolinium oxide) or Dy 2 having an average particle diameter of 0.8 μm as a sintering aid for 0.8% by mass oxygen as an impurity and an aluminum nitride powder having an average particle diameter of 1.0 μm O 3 (dysprosium oxide) was added so as to have the amounts of Gd and Dy elements and oxygen shown in Table 1, wet mixed in ethyl alcohol for 30 hours, and then dried to prepare a raw material powder mixture. Furthermore, 12 parts by weight of butyl methacrylate as an organic binder was added to 100 parts by weight of the raw material mixture, and ball mill mixing was sufficiently performed.
次に乾燥して得た原料粉末混合体をプレス成形機の成形用金型内に充填して１２００ｋｇ／ｃｍ２の加圧力にて圧縮成形して実施例１〜１５用の成形体を多数調製し、引き続き各成形体を表１に示す条件で加熱して脱脂処理した。 Next, the raw material powder mixture obtained by drying was filled into a molding die of a press molding machine, and compression molded at a pressure of 1200 kg / cm 2 to prepare a large number of molded products for Examples 1 to 15. Subsequently, each molded body was heated and degreased under the conditions shown in Table 1.
しかる後に、各成形体を表１に示す雰囲気、温度、時間条件で加熱する仮焼処理を実施した。引き続いて各成形体を、Ｎ２ガス雰囲気中にて表１に示す条件にて緻密化焼結を実施した後に、焼成炉に付設した加熱装置への通電量を減少させて焼成炉内温度が１５００℃まで降下するまでの間における焼結体の冷却速度がそれぞれ表１に示す値になるように調整して焼結体を徐冷した。その結果、寸法が４０ｍｍ×４０ｍｍ×４ｍｍである実施例１〜１５に係る各ＡｌＮ焼結体を調製した。 Thereafter, a calcining treatment was performed in which each molded body was heated under the atmosphere, temperature, and time conditions shown in Table 1. Subsequently, after each compact was subjected to densification and sintering under the conditions shown in Table 1 in an N 2 gas atmosphere, the amount of current supplied to the heating device attached to the firing furnace was reduced, and the temperature in the firing furnace was reduced. The sintered body was gradually cooled by adjusting the cooling rate of the sintered body until the temperature decreased to 1500 ° C. to the values shown in Table 1, respectively. As a result, each AlN sintered body according to Examples 1 to 15 having dimensions of 40 mm × 40 mm × 4 mm was prepared.
［実施例１６〜１９］
実施例１において使用した窒化アルミニウム粉末に対して、焼結助剤としてのＧｄ２Ｏ３（酸化ガドリニウム）を表１に示すＧｄ元素量となるように添加してボールミル混合を十分に実施した後に乾燥して各原料混合体を調製した。さらにこの原料混合体１００重量部に対して有機バインダーとしてのブチルメタクリレートを１２重量部と、可塑剤としてのジブチルフタレートを４重量部と、トルエンを１５重量部とを添加し、さらにボールミル混合を十分に実施してスラリー状の各原料混合体を調製した。
[Examples 16 to 19]
After fully performing ball mill mixing by adding Gd 2 O 3 (gadolinium oxide) as a sintering aid to the amount of Gd element shown in Table 1 to the aluminum nitride powder used in Example 1 Each raw material mixture was prepared by drying. Furthermore, 12 parts by weight of butyl methacrylate as an organic binder, 4 parts by weight of dibutyl phthalate as a plasticizer, and 15 parts by weight of toluene are added to 100 parts by weight of this raw material mixture, and ball mill mixing is sufficiently performed. In practice, slurry-like raw material mixtures were prepared.
次に各原料混合体スラリーから溶媒を除去して粘度を１５０００ｃｐｓに調整した後に、湿式シート成形法（ドクターブレード法）によりシート成形して乾燥し、さらに所定寸法に打ち抜いて実施例１６〜１９用の成形体（グリーンシート）を多数調製した。引き続き各成形体を表１に示す条件にて脱脂処理した。 Next, after removing the solvent from each raw material mixture slurry and adjusting the viscosity to 15000 cps, the sheet is molded by a wet sheet molding method (doctor blade method) and dried, and further punched to a predetermined size for Examples 16 to 19 Many molded articles (green sheets) were prepared. Subsequently, each molded body was degreased under the conditions shown in Table 1.
しかる後に、各成形体を表１に示す雰囲気、温度、時間条件で加熱する仮焼処理を実施した。引き続いて各成形体を、Ｎ２ガス雰囲気中にて表１に示す条件にて緻密化焼結を実施した後に、焼成炉に付設した加熱装置への通電量を減少させて焼成炉内温度が１５００℃まで降下するまでの間における焼結体の冷却速度がそれぞれ表１に示す値になるように調整して焼結体を徐冷した。その結果、寸法が７５ｍｍ×７５ｍｍ×０．６ｍｍである実施例１６〜１９に係る各ＡｌＮ焼結体を調製した。 Thereafter, a calcining treatment was performed in which each molded body was heated under the atmosphere, temperature, and time conditions shown in Table 1. Subsequently, after each compact was subjected to densification and sintering under the conditions shown in Table 1 in an N 2 gas atmosphere, the amount of current supplied to the heating device attached to the firing furnace was reduced, and the temperature in the firing furnace was reduced. The sintered body was gradually cooled by adjusting the cooling rate of the sintered body until the temperature decreased to 1500 ° C. to the values shown in Table 1, respectively. As a result, each AlN sintered body according to Examples 16 to 19 having dimensions of 75 mm × 75 mm × 0.6 mm was prepared.
［比較例１］
一方、仮焼処理を実施しない点以外は実施例１と同一条件で成形・脱脂・焼結処理して同一寸法を有する比較例１に係るＡｌＮ焼結体を調製した。
[Comparative Example 1]
On the other hand, an AlN sintered body according to Comparative Example 1 having the same dimensions was prepared by molding, degreasing and sintering under the same conditions as Example 1 except that the calcination treatment was not performed.
［比較例２］
また、緻密化焼結完了直後に、加熱装置電源をＯＦＦにし、従来の炉冷による冷却速度（約５００℃／ｈｒ）で焼結体を冷却した点以外は実施例１と同一条件で焼結処理して同一寸法を有する比較例２に係るＡｌＮ焼結体を調製した。
[Comparative Example 2]
In addition, immediately after completion of densification sintering, the heating device power was turned off and sintering was performed under the same conditions as in Example 1 except that the sintered body was cooled at a cooling rate by conventional furnace cooling (about 500 ° C./hr). An AlN sintered body according to Comparative Example 2 having the same dimensions was prepared by processing.
［比較例３］
また、緻密化焼結完了直後における焼結体の冷却速度を２５０℃／ｈｒと過大に設定した以外は実施例１と同一条件で焼結処理して同一寸法を有する比較例３に係るＡｌＮ焼結体を調製した。
[Comparative Example 3]
Further, the AlN sintering according to Comparative Example 3 having the same dimensions as that of Example 1 was performed under the same conditions as in Example 1 except that the cooling rate of the sintered body immediately after completion of densification sintering was set to 250 ° C./hr. A ligation was prepared.
［比較例４〜７］
また、空気中で脱脂処理を実施し成形体中の残留炭素量を過少にした比較例４、仮焼処理の温度を低温度側（１１００℃）に設定した比較例５、焼結体中のＧｄ量および酸素量を過少にした比較例６、Ｇｄ２Ｏ３の添加量を過大にした比較例７の各ＡｌＮ焼結体を表１に示す処理条件でそれぞれ調製した。
[Comparative Examples 4 to 7]
Further, Comparative Example 4 in which degreasing treatment was performed in air to reduce the amount of residual carbon in the molded body, Comparative Example 5 in which the temperature of the calcining treatment was set to the low temperature side (1100 ° C.), and the sintered body Each AlN sintered body of Comparative Example 6 in which the amount of Gd and oxygen was made small and Comparative Example 7 in which the amount of Gd 2 O 3 added was made excessive was prepared under the processing conditions shown in Table 1, respectively.
［比較例８］
一方、表１に示すように脱脂処理を低温度で実施し、脱脂処理後の成形体中の残留炭素量を０．８０質量％と過大にした点以外は実施例１と同一条件で成形・仮焼・焼結処理して同一寸法を有する比較例８に係るＡｌＮ焼結体を調製した。
[Comparative Example 8]
On the other hand, as shown in Table 1, the degreasing treatment was performed at a low temperature, and the molding / molding was performed under the same conditions as in Example 1 except that the residual carbon amount in the molded body after the degreasing treatment was excessively 0.80% by mass. An AlN sintered body according to Comparative Example 8 having the same dimensions was prepared by calcination and sintering.
各実施例および比較例に係る焼結体中のＧｄおよびＤｙの含有量は、原料粉末へのＧｄ２Ｏ３およびＤｙ２Ｏ３の添加量より若干減少することが確認された。 It was confirmed that the contents of Gd and Dy in the sintered bodies according to the respective examples and comparative examples slightly decreased from the amounts of Gd 2 O 3 and Dy 2 O 3 added to the raw material powder.
そして得られた実施例１〜１９および比較例１〜８に係る各窒化アルミニウム焼結体の特性を評価するため、各焼結体を粉砕して粉末にした後にＸ線解折法（ＸＲＤ）によって分析し、焼結体の主相および副相を同定しＸ線回折強度比で表した。さらに各焼結体の破面についての倍率３５００倍の走査型電子顕微鏡写真を観察計測することによって、ＡｌＮ結晶粒子の平均粒径、単位面積（１００μｍ×１００μｍ）当りの結晶粒子の存在数および粒界相の最大径を測定するとともに、窒化アルミニウム結晶組織における粒界相の凝集の有無および気孔の凝集の有無を観察した。さらに各焼結体の熱伝導率および三点曲げ強度の平均値を測定し、下記表１右欄に示す結果を得た。 And in order to evaluate the characteristic of each obtained aluminum nitride sintered compact which concerns on Examples 1-19 and Comparative Examples 1-8, after grind | pulverizing each sintered compact to a powder, X-ray-folding method (XRD) The main phase and subphase of the sintered body were identified and represented by the X-ray diffraction intensity ratio. Furthermore, by observing and measuring a scanning electron micrograph at a magnification of 3500 for the fracture surface of each sintered body, the average particle diameter of AlN crystal particles, the number of crystal particles present per unit area (100 μm × 100 μm), and the grains The maximum diameter of the boundary phase was measured, and the presence or absence of agglomeration of grain boundary phases and the presence or absence of pores in the aluminum nitride crystal structure were observed. Furthermore, the average values of the thermal conductivity and the three-point bending strength of each sintered body were measured, and the results shown in the right column of Table 1 below were obtained.
なお、各焼結体のＧｄ，Ｄｙ元素量および酸素量は、焼結体溶液のＩＣＰ発光分光分析によりＧｄ，Ｄｙ濃度および酸素濃度を定量した。また熱伝導率はレーザーフラッシュ法により測定する一方、曲げ強度はＪＩＳ Ｒ−１６０１に準じて、三点曲げ強度を測定した。
上記表１に示す結果から明らかなように、所定のＧｄ，Ｄｙ元素および酸素を含有する実施例１〜１９に係る窒化アルミニウム焼結体においては、比較例２〜３と比較して緻密化焼結完了直後における焼結体の冷却速度を従来法より低く設定しているため、結晶組織内において液相の凝集偏析が少なく、また気孔の凝集もなかった。また焼結体を顕微鏡観察したところ、結晶組織はいずれも粒界相の最大径が０．５μｍ以下と小さく、また気孔の最大径も０．８μｍ未満と微小であった。そして微細な粒界相が均一に分布した結晶組織であるため、高密度（高強度）で高熱伝導度を有する放熱性の高い焼結体が得られた。 As is clear from the results shown in Table 1 above, in the aluminum nitride sintered bodies according to Examples 1 to 19 containing the predetermined Gd, Dy element and oxygen, the densification firing was performed as compared with Comparative Examples 2 to 3. Since the cooling rate of the sintered body immediately after the completion of the setting was set lower than that of the conventional method, there was little aggregation of liquid phase in the crystal structure, and there was no pore aggregation. When the sintered body was observed with a microscope, the crystal structure was as small as a maximum grain boundary phase diameter of 0.5 μm or less and a maximum pore diameter of less than 0.8 μm. And since it was the crystal structure in which the fine grain boundary phase was uniformly distributed, a sintered body with high heat dissipation and high density (high strength) and high thermal conductivity was obtained.
一方、比較例１のように仮焼処理を実施しない場合には、添加したＧｄ２Ｏ３が還元窒化されＧｄＮを生成したり、炭素がそのまま残存して緻密化が阻害されており、十分に焼結が進行しなかった。 On the other hand, when the calcination treatment is not performed as in Comparative Example 1, the added Gd 2 O 3 is reduced and nitrided to form GdN, or the carbon remains as it is and densification is hindered. Sintering did not progress.
また、緻密化焼結完了直後に、従来の炉冷による冷却速度（約５００℃／ｈｒ）で焼結体を冷却した比較例２に係るＡｌＮ焼結体では、粒界相の最大径が１．２μｍとなるような粗大な粒界相が形成され、また最大径が４μｍと大きな気孔が各所に観察され、また副相として熱抵抗が大きいＧｄ３Ａｌ５Ｏ１２（ＧＡＧ）が形成されており、焼結性が低下して強度および熱伝導率も低下した。さらに、焼結体表面に縞状の模様も発生しており外観不良が発生した。 Moreover, in the AlN sintered body according to Comparative Example 2 in which the sintered body was cooled at a cooling rate by conventional furnace cooling (about 500 ° C./hr) immediately after completion of densification sintering, the maximum diameter of the grain boundary phase was 1 A coarse grain boundary phase of 2 μm is formed, large pores having a maximum diameter of 4 μm are observed in various places, and Gd 3 Al 5 O 12 (GAG) having a large thermal resistance is formed as a subphase. As a result, the sinterability decreased and the strength and thermal conductivity also decreased. Furthermore, striped patterns were also generated on the surface of the sintered body, resulting in poor appearance.
一方、緻密化焼結完了直後における焼結体の冷却速度を２５０℃／ｈｒと過大に設定した比較例３に係るＡｌＮ焼結体では、粒界相の最大径が０．８μｍとなるような粗大な粒界相が形成され、また大きな気孔が各所に観察され、焼結性が低下して強度および熱伝導率も低下した。さらに、焼結体表面に縞状の模様も発生しており外観不良が発生した。 On the other hand, in the AlN sintered body according to Comparative Example 3 in which the cooling rate of the sintered body immediately after completion of the densification sintering is set to be excessively 250 ° C./hr, the maximum diameter of the grain boundary phase is 0.8 μm. Coarse grain boundary phases were formed, and large pores were observed in various places, sinterability was reduced, and strength and thermal conductivity were also reduced. Furthermore, striped patterns were also generated on the surface of the sintered body, resulting in poor appearance.
また、空気中で脱脂処理を実施し成形体中の残留炭素量を過少にした比較例４に係るＡｌＮ焼結体では、強度は高いが、熱抵抗が低いＧｄ４Ａｌ２Ｏ９（ＧＡＭ）やＧｄＡｌＯ３（ＧＡＬ）やＧｄ２Ｏ３から成る相が殆ど形成されず、熱抵抗が高いＧｄ３Ａｌ５Ｏ１２（ＧＡＧ）のみが形成されているため、熱伝導値が大幅に低下した。 Further, in the AlN sintered body according to Comparative Example 4 in which the degreasing treatment is performed in the air and the residual carbon amount in the molded body is made small, the strength is high, but the thermal resistance is low Gd 4 Al 2 O 9 (GAM). As a result, almost no phase composed of GdAlO 3 (GAL) or Gd 2 O 3 was formed, and only Gd 3 Al 5 O 12 (GAG) having a high thermal resistance was formed.
さらに、仮焼処理の温度を低温度側（１１００℃）に設定した比較例５に係るＡｌＮ焼結体においても、熱抵抗が低いＧｄ４Ａｌ２Ｏ９（ＧＡＭ）やＧｄＡｌＯ３（ＧＡＬ）やＧｄ２Ｏ３から成る相が殆ど形成されず、熱抵抗が高いＧｄ３Ａｌ５Ｏ１２（ＧＡＧ）が形成されているため、熱伝導値が大幅に低下した。 Furthermore, even in the AlN sintered body according to Comparative Example 5 in which the temperature of the calcination treatment is set to the low temperature side (1100 ° C.), Gd 4 Al 2 O 9 (GAM), GdAlO 3 (GAL), A phase composed of Gd 2 O 3 was hardly formed, and Gd 3 Al 5 O 12 (GAG) having a high thermal resistance was formed, so that the thermal conductivity value was greatly reduced.
一方、焼結体中のＧｄ量および酸素量を過少にした比較例６に係るＡｌＮ焼結体においては、十分に緻密化が進行せず、焼結体の熱伝導率および曲げ強度が共に不十分であった。 On the other hand, in the AlN sintered body according to Comparative Example 6 in which the amount of Gd and oxygen in the sintered body is made too small, the densification does not proceed sufficiently, and both the thermal conductivity and bending strength of the sintered body are poor. It was enough.
さらに、Ｇｄ２Ｏ３の添加量を過大にした比較例７のＡｌＮ焼結体においては、結晶組織が微細化されるため曲げ強度特性は向上するが、熱抵抗が大きいＧＡＧの副相が形成されるため、熱伝導率は低下した。 Furthermore, in the AlN sintered body of Comparative Example 7 in which the amount of Gd 2 O 3 added is excessive, the crystal structure is refined, so that the bending strength characteristics are improved, but a GAG subphase with high thermal resistance is formed. As a result, the thermal conductivity decreased.
一方、脱脂処理を低温度で実施し、脱脂処理後の成形体中の残留炭素量を０．８０質量％と過大にした比較例８においては、ＡｌＮ成形体の緻密化が困難であり、焼結が不可能であり、未焼結状態であった。また焼結体組織においてＧｄ２Ｏ３が還元窒化されＧｄＮを生成したり、炭素がそのまま残存して緻密化が阻害されていた。 On the other hand, in Comparative Example 8 in which the degreasing treatment was performed at a low temperature and the residual carbon amount in the molded body after the degreasing treatment was excessively 0.80% by mass, it was difficult to densify the AlN molded body. It was impossible to synthesize, and it was in an unsintered state. Further, Gd 2 O 3 was reduced and nitrided in the sintered body structure to generate GdN, or carbon remained as it was and densification was inhibited.
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| JP2013119485A (en) * | 2011-12-06 | 2013-06-17 | Pilot Corporation | Ceramic calcined material for cutting and sintering and method for producing the same |
| CN110643859A (en) * | 2019-08-30 | 2020-01-03 | 厦门大学 | Aluminum-based composite material containing gadolinium-tungsten element and application thereof |
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