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Alpha-Sialon Powder and Process for Producing The (19) TZZ_¥Z_T (11) EP 1 783 096 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C01B 21/082 (2006.01) C09K 11/08 (2006.01) 20.08.2014 Bulletin 2014/34 C09K 11/80 (2006.01) H01L 33/00 (2010.01) C09K 11/77 (2006.01) (21) Application number: 05751143.8 (86) International application number: (22) Date of filing: 14.06.2005 PCT/JP2005/011198 (87) International publication number: WO 2006/011317 (02.02.2006 Gazette 2006/05) (54) ALPHA-SIALON POWDER AND PROCESS FOR PRODUCING THE SAME ALPHA-SIALON-PULVER UND HERSTELLUNGSVERFAHREN DAFÜR POUDRE DE ALPHA-SIALON ET PROCÉDÉ SERVANT À PRODUIRE CELLE- CI (84) Designated Contracting States: (74) Representative: Marshall, John Grahame et al DE FR GB SERJEANTS 25 The Crescent (30) Priority: 30.07.2004 JP 2004224812 King Street Leicester LE1 6RX (GB) (43) Date of publication of application: 09.05.2007 Bulletin 2007/19 (56) References cited: EP-A2- 1 278 250 EP-A2- 1 555 307 (73) Proprietors: JP-A- 2002 363 554 JP-A- 2003 336 059 • National Institute for Materials Science JP-A- 2004 186 278 Ibaraki 3050047 (JP) • DENKI KAGAKU KOGYO KABUSHIKI KAISHA • XIE R-J ET AL: "PREPARATION AND Chiyoda-ku, LUMINESCENCE SPECTRA OF CALCIUM- AND Tokyo 100-8455 (JP) RARE-EARTH (R = EU, TB, AND PR)-CODOPED ALPHA-SIALON CERAMICS", JOURNAL OF THE (72) Inventors: AMERICAN CERAMIC SOCIETY, BLACKWELL • MITOMO, Mamoru PUBLISHING, MALDEN, MA, US, vol. 85, no. 5, 1 Tsukuba-shi, October 2000 (2000-10-01), pages 1229-1234, Ibaraki 3050047 (JP) XP001151981, ISSN: 0002-7820 • HIROSAKI, Naoto • NAKAYAMA S ET AL: "OXIDATION BEHAVIOR Tsukuba-shi, OF RE-ALPHA,SIALON CERAMICS (RE = ND, SM, Ibaraki 3050047 (JP) GD, DY, Y, HO, ER, YB)", JOURNAL OF THE • EMOTO, Hideyuki CERAMICSOCIETY OF JAPAN, INTERNATIONAL CENTRAL RESEARCH INSTITUTE EDITION, FUJI TECHNOLOGY PRESS, TOKYO, Machida-shi, JP, vol. 101, no. 10, 1 January 1993 (1993-01-01), Tokyo 1948560 (JP) pages 1184-1186, XP008052851, ISSN: 0912-9200 • IBUKIYAMA, Masahiro • NAKAYAMA S. ET AL: ’Oxidation Behavior of RE- CENTRAL RESEARCH INSTITUTE a-Sialon Ceramics(RE=Nd,Sm,Gd,Dy,Y,Ho,Er, Machida-shi, Yb).’ JOURNAL OF THE CERAMIC SOCIETY OF Tokyo 1948560 (JP) JAPAN. vol. 101, no. 10, 1993, pages 1184 - 1186, XP008052851 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 783 096 B1 Printed by Jouve, 75001 PARIS (FR) 1 EP 1 783 096 B1 2 Description size are dispersed in a molding material such as epoxy resin, it is the present situation that for the reason stated Technical Field above, any α-sialon powder has never been marketed. [0007] As a typical process of synthesizing an α-sialon [0001] The present invention relates to a method of 5 powder, the reduction nitriding method can be cited in producing an α -sialon powder that can be utilized, which a mass of mixed powders of aluminum oxide among others, as a phosphor for a white light emitting (Al2O3), silicon oxide (SiO2) and an oxide of a metal diode which uses a blue or ultraviolet light emitting diode whose atoms are to be solid-solved in the lattice is heat- as its light source. treated in the presence of carbon in a nitrogen atmos- 10 phere (see References 7 to 9 below). Background Art [0008] Reference 1: Japanese Patent Laid Open Ap- plication JP 2002-363554 A [0002] Being a solid solution of α type silicon nitride, Reference 2: Japanese Patent Laid Open Application JP an α-sialon (Si-Al-O-N) because of its high hardness and 2003-336059 A excellent wear resistance, high-temperature strength15 Reference 3: Japanese Patent Laid Open Application JP and oxidation resistance is finding its uses in such as 2003-124527 A slide members and high-temperature resistant structural Reference 4: Japanese Patent Laid Open Application JP components. 2003-206418 A [0003] The α-sialon has a structure in which atoms of Reference 5: Japanese Patent Laid Open Application JP a specific element (such as Ca, Li, Mg, Y or one or more 20 2004-67837 A lanthanoid except La and Ce) are entered into the crystal Reference 6: J. W. H. van Krebel, "On new rare-earth lattice to form a solid solution while maintaining their elec- doped M-Si-Al-O-N materials", TU Eindhoven, The Neth- trical neutrality so that the Si-N bond is in part substituted erlands, pp.145 - 161 (1998) with the Al-N bond (in part also with Al-O bond). In recent Reference 7: M. Mitomo et al., "Preparation of α-SiAlON years, after the discovery that by suitably selecting the 25 Powders by Carbothermal Reduction and Nitridation", element for this entry and solid solving, fluorescence Ceram. Int., Vol. 14, pp.43 - 48 (1988) properties which are useful for a white light emitting diode Reference 8: J. W. T. van Rutten et al., "Carbothermal (hereinafter referred to as "white LED") can be revealed, Preparation of Ca - α - SiAlON", J. Eur. Ceram. Soc., its putting to practical use has been under investigation Vol.15, pp.599 - 604 (1995) (See References 1 to 6 below). 30 Reference 9: K. Komeya et al., "Hollow Beads Composed [0004] An α-sialonfor use as a slide member, structural of Nanosize Ca α -sialon Grains", J. Am. Ceram. Soc., component or the like has conventionally been made in Vol.83, pp.995 - 997 (2000) the form of a dense sintered body. In this case, a mass [0009] Although the method described above has the of mixed powders of silicon nitride (Si 3N4), aluminum ni- feature that the α-sialon powder can be synthesized at tride (AlN) and an oxide of a solid-solving element is sin- 35 a relatively low temperature around 1500°C from the tered in a nitrogen atmosphere under normal or gas pres- source powders which are inexpensive, not only must a sure or by hot pressing or the like to form a solid solution plurality of intermediate products be had in way stages while densifying the mass simultaneously. This is to en- of the synthesis process, but also the production of gas sure that a liquid phase formed of a surface oxide layer components such as SiO and CO has made it difficult to of silicon nitride and aluminum nitride and the oxide of 40 yield a product which is of single phase and to control the solid-solving element midway of the sintering process the composition and granular size strictly. allows the mass densification to proceed and that later [0010] An α-sialon powder can also be obtained by in the sintering process the liquid phase is solid-solved firing at a high temperature a mixture of silicon nitride, within the powder grains so as not to leave a glass phase aluminum nitride and an oxide of an element whose at- at the grain boundaries. 45 oms are to be solid-solved in the lattice and then pulver- [0005] In the case where a mass of α-sialon powder is izing the resultant sintered body of α-sialon. used as the starting material, sintering even at a temper- [0011] The conventional methods of making anα- ature close to its decomposition temperature does not sialon powder require a pulverization treatment under allow the mass to be densified well and does necessitate severe conditions in order to ensure that intergranular an assistant in order to form the liquid phase with the 50 bonds by liquid phase sintering in the firing process re- result that the glass phase is then left at the grain bound- main firm and to obtain the powder of a desired particle aries. For reasons such as that such a grain boundary size. As the pulverizing conditions become severer, the glass phase is undesirable in mechanical properties, the problem arises that the chances of entry of impurities are α-sialon powder has little been used as the starting ma- increased and also of entry of defects onto individual par- terial for uses of α-sialon in slide members, structural 55 ticle surfaces. components and the like. [0012] The use as a phosphor of an α-sialon powder [0006] On the other hand, while a phosphor for white as made by the conventional methods poses the problem LED is used in which particles of submicron to micron that inasmuch as it is the particle surface area which 2 3 EP 1 783 096 B1 4 mainly is responsive to excitation light, the defects intro- under a specified condition and pulverized into a speci- duced by the pulverization treatment into such surface fied particle size and that the phosphor by α-sialon pow- areas largely affect its fluorescent properties and cause der is even more easily obtained if its making is performed its light emitting characteristic to deteriorate. in a crucible of a specified material. We have arrived at The preamble of claim 1 is derivable from EP 1555307 5 the present invention. A2 which is an earlier patent document published after [0017] While the density as a product of the weight of the present filing date and which accordingly forms part a source mixed powder material divided by the volume of the state of the art only under Article 54(3) EPC.
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