Abstract: Provided is a method for producing a wavelength conversion sintered body that emits light under irradiation of excitation light. The method for producing a wavelength conversion sintered body includes: preparing a molded body obtained by molding a mixture containing an ?-SiAlON fluorescent material and aluminum oxide particles and having a content of Ga of 15 ppm by mass or less; and primary calcining the molded body at a temperature in a range of 1,370° C. or more and 1,600° C. or less to obtain a first sintered body.

Abstract: Provided are a transparent fluorescent sialon ceramic having fluorescence and optical transparency; and a method of producing the same. Such a transparent fluorescent sialon ceramic includes a sialon phosphor which contains a matrix formed of a silicon nitride compound represented by the formula Mx(Si,Al)y(N,O)z (here, M represents at least one selected from the group consisting of Li, alkaline earth metals, and rare earth metals, 0?x/z<3, and 0<y/z<1) and a luminescent center element.

Abstract: Provided are a transparent fluorescent sialon ceramic having fluorescence and optical transparency; and a method of producing the same. Such a transparent fluorescent sialon ceramic includes a sialon phosphor which contains a matrix formed of a silicon nitride compound represented by the formula Mx(Si,Al)y(N,O)z (here, M represents at least one selected from the group consisting of Li, alkaline earth metals, and rare earth metals, 0?x/z<3, and 0<y/z<1) and a luminescent center element.

Abstract: In order to provide a sintered, hexagonal boron nitride body (2a, 2b), same is produced by at least one pressing process and subsequent sintering process from a powder (P) made of a hexagonal boron nitride, its density being deliberately set to a value of <1.6 g/cm3. Studies have shown that, due to the selection of this lower density, the boron nitride body (2a, 2b) exhibits very high isotropy, when compared with conventional hexagonal boron nitride bodies. This relates in particular to thermal conductivity and the coefficient of thermal expansion, which are also largely temperature-independent.

Abstract: A manufacturing method with which a high thermal conductivity silicon nitride substrate having excellent sintering performance can be manufactured without the occurrence of a molding crack or degreasing crack, as well as to provide a silicon nitride substrate, and a silicon nitride circuit board and a semiconductor module using the silicon nitride substrate. In the manufacturing method, in which a slurry is produced by mixing a silicon nitride powder, a sintering additive powder, and a binder in an organic solvent which is a dispersion medium, and the slurry is formed into a sheet, followed by degreasing and sintering, the oxygen content of the silicon nitride powder is 2.0 mass % or less and the specific surface area of the same is 3 to 11 m2/g, the additive ratio of the sintering additive powder is 4 to 15 mol %, and the water content ratio of the organic solvent is 0.03 to 3 mass %.

Abstract: Disclosed is a porous sintered reaction-bonded silicon nitride ceramic, which includes an array of sintered granules having fine pore channels in the sintered granules and coarse pore channels formed between the sintered granules, and in which the pore channel size is controlled so that both coarse pores and fine pores are formed together in the ceramic, thus simultaneously enhancing air permeability and capturing efficiency. A method of manufacturing the porous sintered reaction-bonded silicon nitride ceramic is also provided.

Abstract: The invention concerns a method for manufacturing a ceramic material with pseudo-isotropic microstructure. The method for tailoring the microstructure for manufacturing of sintered ceramic components involves a spark plasma sintering (SPS) process. By performing the SPS process in at least two steps it is possible to separate densification from grain growth. An initial sintering step at a first temperature and a first pressure, followed by a controlled grain growth step at a higher temperature and lower pressure makes it possible to manufacture ceramic components with controlled microstructure and improved mechanical properties.

Abstract: A silicon nitride sintered body, wherein in a silicon nitride substrate consisting of crystal grains of ?-type silicon nitride and a grain boundary phase containing at least one type of rare earth element (RE), magnesium (Mg) and silicon (Si), the grain boundary phase consists of an amorphous phase and a MgSiN2 crystal phase. The X-ray diffraction peak intensity of any crystal plane of a crystal phase containing the rare earth element (RE) is less than 0.0005 times the sum of the diffraction peak intensities of (110), (200), (101), (210), (201), (310), (320) and (002) of the crystal grains of the ?-type silicon nitride; and the X-ray diffraction peak intensity of (121) of the MgSiN2 crystal phase is 0.0005 to 0.003 times the sum of the X-ray diffraction peak intensities of (110), (200), (101), (210), (201), (310), (320) and (002) of the crystal grains of the ?-type silicon nitride.

Abstract: A mold forming and molding technology operable to produce a silicon ingot suitable for obtaining a solar cell substrate is disclosed. A slurry is prepared comprising particles with surface oxide layers operable to bond the particles to each other. An external force is applied to the slurry to eliminate cohesion of the particles to form a de-cohesive slurry, and an inner surface of a mold base is coated with the de-cohesive slurry to form a releasing layer that reduces defects in the silicon ingot.

Abstract: The present invention relates to extrudable ceramic masses and other masses which set as a result of baking or sintering, which masses comprise specific additives based on water-soluble cellulose ethers, an extrusion process, the extrudates and their use.

Abstract: A catalyst with large surface area structure, in particular for steam-reforming catalysts, which is characterized in that the large surface area structure is formed of a large number of round or parallel penetrating holes of polygonal cross-section, wherein the catalyst carrier is prepared in the injection molding process, coated with a washcoat and then impregnated with the active component. The catalyst carrier includes at least one sinterable material and has a lateral pressure resistance of at least 700 N. Also, a process for the preparation of such catalysts and the use thereof in a reactor.

Abstract: An outer ring, an inner ring and a ball that are a rolling contact member formed of sintered ? sialon inexpensive and capable of reliably ensuring sufficient durability, is constituted of a sintered body containing ? sialon as a main component and having a remainder formed of an impurity, and the outer ring, the inner ring and the ball have raceway/rolling contact surfaces, i.e., an outer ring raceway surface, an inner ring raceway surface and a ball rolling contact surface included in a portion having an outer ring high density layer, an inner ring high density layer and a ball high density layer higher in density than an inner portion.

Abstract: Provided is a manufacturing method with which a high thermal conductivity silicon nitride substrate having excellent sintering performance can be manufactured without the occurrence of a molding crack or degreasing crack, as well as to provide a silicon nitride substrate, and a silicon nitride circuit board and a semiconductor module using said silicon nitride substrate. In this silicon nitride substrate manufacturing method, in which a slurry is produced by mixing a silicon nitride powder, a sintering additive powder, and a binder in an organic solvent which is a dispersion medium, and the slurry is formed into a sheet, followed by degreasing and sintering, the oxygen content of the silicon nitride powder is 2.0 mass % or less and the specific surface area of the same is 3 to 11 m2/g, the additive ratio of the sintering additive powder is 4 to 15 mol %, and the water content ratio of the organic solvent is 0.03 to 3 mass %.

Abstract: Isopipes (13) for making a glass or a glass-ceramic using a fusion process are provided. The isopipes are made from a silicon nitride refractory material that is: (a) produced in block form in an atmosphere having a pO2 of less than 0.1 using less than 10 weight percent of one or more sintering aids, (b) machined into an isopipe configuration, and (c) exposed to a partial pressure of oxygen equal to or greater than 0.1 for a period of time and at a temperature sufficient to form a SiO2 layer (31) which exhibits substantially only a passive oxidation mechanism. The SiO2 layer (31) serves as a protective barrier for further oxidation of the silicon nitride during use of the isopipe (13). The isopipes (13) exhibit less sag during use than isopipes composed of zircon.

Abstract: A new type of composite with wooden quality, which contains a plastic inner layer and an outer envelope is described. The plastic inner layer is crosslinked with the outer envelope, the latter of which is made up from a plastic material containing a 5-20 wt. % of wood flour.

Abstract: A high-strength, fracture-resistant silicon nitride ceramic material that includes about 5 to about 75 wt-% of elongated reinforcing grains of beta-silicon nitride, about 20 to about 95 wt-% of fine grains of beta-silicon nitride, wherein the fine grains have a major axis of less than about 1 micron; and about 1 to about 15 wt-% of an amorphous intergranular phase comprising Si, N, O, a rare earth element and a secondary densification element. The elongated reinforcing grains have an aspect ratio of 2:1 or greater and a major axis measuring about 1 micron or greater. The elongated reinforcing grains are essentially isotropically oriented within the ceramic microstructure. The silicon nitride ceramic exhibits a room temperature flexure strength of 1,000 MPa or greater and a fracture toughness of 9 MPa-m(1/2) or greater. The silicon nitride ceramic exhibits a peak strength of 800 MPa or greater at 1200 degrees C.

Abstract: A method of forming a metal deposit on an ultra-hard material. In an embodiment, the method includes providing a plurality of ultra-hard particles, mixing the ultra-hard particles in a solution with a metal salt, drying the solution to create a mixture of metal salt particles adhered to surfaces of the ultra-hard particles, heating the mixture to convert the metal salt particles into metal deposits on the surfaces of the ultra-hard particles, and HTHP sintering the mixture of ultra-hard particles with the metal deposits to form a polycrystalline ultra-hard material.

Abstract: A cermet and method of forming the cermet, the cermet including a Sialon and an alloy comprising nickel aluminide and boron, wherein the Sialon includes silicon aluminum oxynitride, and wherein at least a portion of the Sialon is bonded with at least a portion of the alloy. In one example, the cermet is about 70 weight percent to about 90 weight percent of the Sialon, and about 10 weight percent to about 30 weight percent of the alloy.

Abstract: An outer ring, an inner ring and a ball that are a rolling contact member formed of sintered ? sialon inexpensive and capable of reliably ensuring sufficient durability, is constituted of a sintered body containing ? sialon as a main component and having a remainder formed of an impurity, and the outer ring, the inner ring and the ball have raceway/rolling contact surfaces, i.e., an outer ring raceway surface, an inner ring raceway surface and a ball rolling contact surface included in a portion having an outer ring high density layer, an inner ring high density layer and a ball high density layer higher in density than an inner portion.

Abstract: Method of fabricating RBSN parts in which the processing of compacts of silicon to produce reaction bonded silicon nitride products is accomplished in a continuous style furnace. The furnace of the preferred embodiment is arranged as a contiguous series of furnace sections or zones configured to have a part conveyor traveling slowly from one end to another to sequentially expose the parts to each zone. Each zone may for example be one foot long. The conveyor then travels at a rate of one foot per hour. Parts to be nitrided are settered onto kiln furniture plates while providing a minimum one-quarter inch clearance to all other parts. The parts on the plates are conveyed through the sequential temperature zones in a continuous fashion while under ambient pressure flowing nitrogen gas. The parts travel through the contiguous temperature zones at a constant rate of conveyance allowing the nitriding reaction to progress to completion.

Abstract: A silicon nitride sintered material includes a silicon nitride crystal and a grain boundary layer that contains at least two of a first metal silicide (a metal silicide having, as a first metal element, at least one selected from the group consisting of Fe, Cr, Mn and Cu), a second metal silicide (a metal silicide having, as a second metal element, at least one of W or Mo) and a third metal silicide (a metal silicide having a plurality of metal elements including the first metal element and the second metal element), wherein the grain boundary layer has neighboring phase where at least two of the first through third metal silicides exist in contact with each other.

Abstract: A composition and method for fabricating high-density Ta—Al—O, Ta—Si—N, and W—Si—N sputtering targets, having particular usefulness for the sputtering of heater layers for ink jet printers. Compositions in accordance with the invention comprise a metal component, Si3N4, and a sintering aid so that the targets will successfully sputter without cracking, etc. The components are combined in powder form and pressure consolidated under heated conditions for a time sufficient to form a consolidated blend having an actual density of greater that about 95% of the theoretical density. The consolidated blend may then be machined so as to provide the final desired target shape.

Abstract: The invention relates to a light emitting device, especially a LED comprising a SiAION material with a transparency of ?10% to ?85% for light in the wavelength range from ?550 nm to ?1000 nm.

Abstract: A densified silicon nitride body can be formed using a lanthana-based sintering aid. The composition may exhibit properties that provide a material useful in a variety of applications that can benefit from improved wear characteristics. The composition may be densified by sintering and hot isostatic pressing.

Abstract: A method for producing a silicon nitride filter, which comprises heat-treating in nitrogen a green body comprising from 60 to 95 mass % of metal silicon particles having an average particle diameter of from 10 to 75 ?m, wherein particles having particle diameters of from 5 to 100 ?m are at least 70 mass % in the entire metal silicon particles, and from 5 to 40 mass % of a pore-forming agent, to convert metal silicon substantially to silicon nitride. More preferably, the green body contains at least one member selected from the group consisting of an inorganic acid salt, an organic acid salt and a hydroxide containing at least one metal element selected from the group consisting of Mg, Ca, Fe and Cu.

Abstract: A firing container for silicon nitride ceramics, which is a hermetically sealed container having a gas inlet and a gas outlet, characterized in that the interior of the hermetically sealed container is partitioned by a gas supply chamber partition plate into a gas supply chamber communicating with the gas inlet, and a firing chamber to accommodate an object to be heat-treated and communicating with the gas outlet, and the gas supply chamber partition plate has vent holes selectively formed in the vicinity of its periphery.

Abstract: The present invention relates to a method of making a sintered body comprising one or more hard constituents in a binder phase by injection molding or extrusion. According to the invention, the granulating agent during drying is an ethylene oxide polymer and the binder system is not miscible with that compound. The extraction step is performed in an alcohol based solvent at a temperature of 50-78° C., preferably 60-78° C.

Abstract: A method of manufacturing an electrical-resistance heating element includes forming sintered ceramics or calcined ceramics, forming an electrode on the sintered ceramics or the calcined ceramics, and forming a ceramic base material having mainly a high melting point metal on the electrode embedded therein, thereby forming a heating element with built-in electrode.

Abstract: A silicon nitride wear resistant member is composed of a ceramic sintered body containing 55 to 75 mass % of silicon nitride, 12 to 28 mass % of silicon carbide, 3 to 15 mass % of at least one element selected from the group consisting of Mo, W, Ta, and Nb in terms of silicide thereof, and 5 to 15 mass % of grain boundary phase composed of a rare earth element-Si—Al—O—N, the wear resistant member having an electrical resistance of 107 to 104 ?·cm, a porosity of 1% or less, and a three point bending strength of 900 MPa or more. The wear resistant member has a predetermined electric resistance (electro-conductivity) in addition to the high strength and toughness inherent in silicon nitride per se, especially has a high sliding characteristic. Also, a method of manufacturing the wear resistant member is provided.

Abstract: A method for producing a silicon nitride honeycomb filter, which comprises heat-treating in a nitrogen atmosphere a green body comprising from 50 to 85 mass % of metal silicon particles having an average particle diameter of from 5 to 50 ?m, from 5 to 30 mass % of glass hollow particles having a softening temperature of from 400 to 1000° C. and from 10 to 20 mass % of an organic binder to convert metal silicon substantially to silicon nitride.

Abstract: Composite materials containing silicon, titanium, carbon, and nitrogen, formed by spark plasma sintering of ceramic starting materials to a high relative density, demonstrate unusually high electrical conductivity as well as high-performance mechanical and chemical properties including hardness, fracture toughness, and corrosion resistance. This combination of electrical, mechanical, and chemical properties makes these composites useful as electrical conductors in applications where high-performance materials are needed due to exposure to extreme conditions such as high temperatures, mechanical stresses, and corrosive environments.

Abstract: The present invention provides a process for the manufacture of dense neodymium stabilized ?-Si3N4-?-SiAlON composite, wherein a synergistic composition essentially consisting of Si3N4, Al2O3, AlN, SiO2 and Nd2O3 as starting materials is mixed in proportion to make a total of 100 mole in the mixed batch, passing the powder through 100 mesh, pressing the powder to form green compacts, sintering the green compacts at a temperature in the range of 1700° to 1900° C. in nitrogen atmosphere. The process of the present invention provides neodymium stabilized ?-Si3N4-?-SiAlON composites by processing a composition from the system Si3N4—Al2O3.AlN—Nd2O3.9AlN—SiO2 resulting into dense product of the order of >98% theoretical density with the advantages such as cost effectiveness, high hardness and high fracture toughness.

Abstract: A method for making a crystallized ceramic body containing a two phase composite comprising an alpha prime SiAlON phase that contains ytterbium and a beta prime SiAlON phase, the process includes the steps of: blending together a starting powder mixture that upon densification forms the SiAlON ceramic, the starting powder includes at least about 70 weight percent silicon nitride powder wherein the silicon nitride powder contains beta silicon nitride in an amount less than or equal to about 1.

Abstract: Densified composites of silicon nitride, silicon carbide, and boron nitride that exhibit high creep resistance are obtained by sintering a mixture of amorphous powders of silicon nitride, silicon carbide, and boron nitride in the presence of an electric field under high pressure. The grain size in the resulting composite is less than 100 nanometers for all components of the composite, and the composite exhibits high creep resistance.

Abstract: The invention provides porous silicon nitride ceramics that having uniform, fine closed pores and a manufacturing method thereof. Metal Si powder is mixed with a sintering additive, followed by thermal treatment, which is a pre-process for forming a specific grain boundary phase. Two-stage thermal treatment is thereafter performed by microwave heating at a temperature of 1000° C. or more. The metal Si powder is thereafter subjected to a nitriding reaction from its surface, the metal Si is thereafter diffused to nitride formed on the outer shell thereof such that porous silicon nitride ceramics having uniform, fine closed pores can be produced. Having a high ratio of closed pores and being superior in electrical/mechanical characteristics, the porous silicon nitride ceramics can display excellent characteristics if used, for example, for an electronic circuit board that requires an anti-hygroscopicity, a low dielectric constant, a low dielectric loss, and mechanical strength.

Abstract: Densified composites of silicon nitride and silicon carbide that exhibit high creep resistance are obtained by mechanically activating a mixture of amorphous powders of silicon nitride and silicon carbide and sintering the mechanically activated mixture in the presence of an electric field under high pressure. The grain size in the resulting composite is less than 100 nanometers for all components of the composite, and the composite exhibits high creep resistance.

Abstract: Sintered silicon nitride products comprising predominantly ?-silicon nitride grains in combination with from about 0.1 to 30 mole % silicon carbide, and grain boundary secondary phases of scandium oxide and scandium disilicate. Such products have high fracture toughness, resistance to recession, and resistance to oxidation at temperatures of at least 1500° C. Methods for preparing sintered silicon nitride products are also disclosed.

Abstract: A SiAlON-based ceramic particularly suited for use as a cutting tool in the high speed chip forming machining of metals composed of a SiAlON matrix including a) a phase of alpha′ SiAlON represented by the general formula of Mx (Si,Al)12(O,N)16, wherein 0<x<2 and M is at least two cationic elements, a first cationic element being 0.2 to 4 weight percent Mg and optionally between 0.5 and 15 weight percent of one or more of Ca, Sr, and Ba calculated as oxide, based on the SiAlON matrix, and a second cationic element being one or more of Y, Sc, La and the rare earth (RE) elements; b) a phase consisting of beta′ SiAlON represented by the general formula Si6−zAl2OzN8−z wherein 0<z<4.2; and c) a component containing glass, and at least one additional intergranular crystal phase that is detectable using X-ray diffraction techniques is provided.

Abstract: The core/jacket catalyst molding with a core made from an inorganic support material and with a jacket made from a catalytically active material can be prepared by coextruding an aqueous molding composition which comprises the support material or a precursor thereof, with an aqueous molding composition which comprises the catalytically active material or a precursor thereof, then drying the coextrudate, and then calcining the dried coextrudate.

Abstract: A ceramic material suitable for use in production of paving tiles, construction tiles, flooring in offices, flooring in machinery plants and so forth is obtained by a method comprising steps of mixing defatted bran derived from rice bran with a thermosetting resin before kneading, subjecting a kneaded mixture thus obtained to a primary firing in an inert gas at a temperature in a range of 700 to 1000° C., pulverizing the kneaded mixture after the primary firing into carbonized powders, kneading the carbonized powders with which ceramic powders, a solvent, and a binder as desired are mixed into a plastic workpiece (kneaded mass), pressure-forming the plastic workpiece at pressure in a range of 10 to 100 MPa, and subjecting a formed plastic workpiece thus obtained again to firing in an inert gas atmosphere at a temperature in a range of 100 to 1400° C.

Abstract: A silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase, wherein the grain boundary phase consists essentially of a single phase of a Lu4Si2O7N2 crystal phase, and the composition of the silicon nitride sintered product is a composition in or around a triangle ABC having point A: Si3N4, point B: 28 mol % SiO2-72 mol % Lu2O3 and point C: 16 mol % SiO2-84 mol % Lu2O3, as three apexes, in a ternary system phase diagram of a Si3N4—SiO2—Lu2O3 system. Also disclosed is a silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase of an oxynitride, wherein the composition of the sintered product is a composition in a triangle having point A: Si3N4, point B: 40 mol % SiO2-60 mol % Lu2O3 and point C: 60 mol % SiO2-40 mol % Lu2O3, as three apexes, in a ternary system phase diagram of a Si3N4—SiO2—Lu2O3 system.

Abstract: An oxidation resistant carbon composite material comprises nanocrystalline silicon carbide regions distributed throughout a carbon matrix. The composite is prepared by intermixing in a solvent a silicon carbide precursor and a carbon precursor and forming a solution that is free of solids. After removing the solvent from the mixture, the remaining material is pyrolyzed and forms the characteristic nanocrystalline silicon carbide in a carbon matrix. A composite made by the subject method and a part made from the composite are also provided.

Abstract: 12A high temperature gas turbine component includes an inner core made of a monolithic ceramic material embedded within an outer CMC shell. The inner core may be formed with a through hole, blind hole, wear pads and the like. A method of making the bushing includes the steps of a) forming an inner core of silicon nitride or silicon carbide; and b) applying a ceramic matrix composite material over substantially all of the inner core.

Abstract: A silicon nitride sintered material includes a polycrystal material having silicon nitride crystal grains and a grain boundary phase. The sintered material contains a Yb element in an amount of 2 to 30% by weight in terms of its oxide and an Al element in an amount of 1 to 20% by weight in terms of its oxide and has a thermal conductivity of 40 W/mK or less at room temperature, a resistivity of 1×105to 1×1012 &OHgr;·cm at room temperature, and a porosity of 0.5% or less.

Abstract: Wear resistant member for electronic equipment comprises a silicon nitride sintered body that contains conductivity enhancing particles, and has electrical resistivity in the range from 1 to 105 &OHgr;·m. In silicon nitride sintered body, agglomeration of conductivity enhancing particles in which distance between conductivity enhancing particles is less than 1 &mgr;m exists by 30% or less by area ratio per unit area. Wear resistant member is used for a bearing ball or the like, being applied in a rotation actuator of electronic equipment such as a magnetic recorder and optical disk drive. Malfunction of electronic equipment due to static electricity may be cancelled due to electrical resistivity that silicon nitride sintered body has.

Abstract: The present invention provides a carbon heating element having an arbitrary specific resistance and an arbitrary shape which are arbitrary necessary as a heating element, and a method of producing the same. The carbon heating element is obtained by uniformly dispersing one or at least two metal or metalloid compounds into a composition having shapability and showing a high yield of a carbon residue after firing, shaping the dispersed material-containing mixture thus obtained, and firing the shaped material under a nonoxidizing atmosphere.

Abstract: The invention concerns a new and improved method for the production of porous and formed bodies with polycrystalline structure that meets the high quality requirements of the usually excellent material characteristics of porous and formed bodies based on silicon nitride and, at the same time, at least considerably reduces known disadvantages of other state-of-the-art techniques. In this, it is provided to first precompress the silicon nitride powder mix with a modal particle distribution of coarse and fine particles to form a green body, and to subsequently bake it using a temperature-based sintering process.

Abstract: A silicon nitride sintered material includes a polycrystal material having silicon nitride crystal grains and a grain boundary phase. The sintered material contains a Yb element in an amount of 2 to 30% by weight in terms of its oxide and an Al element in an amount of 1 to 20% by weight in terms of its oxide and has a thermal conductivity of 40 W/mK or less at room temperature, a resistivity of 1×105 to 1×1012 &OHgr;·cm at room temperature, and a porosity of 0.5% or less.

Abstract: A silicon nitride porous body which is a body having a generally columnar outer shape and at least two through-holes mutually parallel to one another and which has generally perpendicularly oriented columnar crystals on the surface of the through-holes.

Abstract: A silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase, wherein the grain boundary phase consists essentially of a single phase of a Lu4Si2O7N2 crystal phase, and the composition of the silicon nitride sintered product is a composition in or around a triangle ABC having point A: Si3N4, point B: 28 mol % SiO2-72 mol % Lu2O3 and point C: 16 mol % SiO2-84 mol % Lu2O3, as three apexes, in a ternary system phase diagram of a Si3N4—SiO2—Lu2O3 system. Also disclosed is a silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase of an oxynitride, wherein the composition of the sintered product is a composition in a triangle having point A: Si3N4, point B: 40 mol % SiO2-60 mol % Lu2O3 and point C: 60 mol % SiO2-40 mol % Lu2O3, as three apexes, in a ternary system phase diagram of a Si3N4—SiO2—Lu2O3 system.