Abstract: There is provided a treatment container which enables to prolong a period of time taken for reaction products, such as a halide generated through reaction with corrosive halide gas, to exfoliate and fall down as particles, and decreases the frequency of periodic maintenance operation, thereby implementing increase of operating time. The treatment container constituting a chamber or a bell jar has a portion of the inner surface to be exposed to corrosive halide gas plasma and is formed with a sintered body mainly composed of a compound of yttrium and aluminum with oxygen, and the portion has a roughened surface of a mean roughness Ra of 1.5 to 10 &mgr;m.

Abstract: A ceramic composite containing alkali-metal-beta- or beta″-alumina and an oxygen-ion conductor is fabricated by converting alpha-alumina to alkali-metal-beta- or beta″-alumina. A ceramic composite with continuous phases of alpha-alumina and the oxygen-ion conducting ceramic, such as zirconia, is exposed to a vapor containing an alkali-metal oxide, such as an oxide of sodium or potassium. Alkali metal ions diffuse through alkali-metal-beta- or beta″-alumina converted from &agr;-alumina and oxygen ions diffuse through the oxygen-ion conducting ceramic to a reaction front where alpha-alumina is converted to alkali-metal-beta- or beta″-alumina. A stabilizer for alkali-metal-beta″-alumina is preferably introduced into the &agr;-alumina/oxygen-ion conductor composite or introduced into the vapor used to convert the alpha-alumina to an alkali-metal-beta″-alumina.

Abstract: The invention provides a sintered, alumina ceramic product comprising about 90-97.5 w/w % Al2O3, about 0.5-1.0 w/w % MgO, about <0.05-1.0 w/w % SiO2, about 4.5-7.5 w/w % ZrO2 and about 0.07-0.13 w/w % HfO2.

Abstract: Abrasive particles and methods of making abrasive particles are disclosed. The abrasive particles may be incorporated into a variety of abrasive articles, including bonded abrasives, coated abrasives, nonwoven abrasives, and abrasive brushes.

Abstract: An electrostatic removing member includes a semiconductive zirconia sintered body having a volume specific resistance value from 105 to 109&OHgr;·cm. Preferably, the semiconductive zirconia sintered body includes 60 to 90 weight % of ZrO2, a stabilizing agent, and 10 to 40 weight % of one or more of oxides of Fe, Co, Ni and Cr. In one embodiment, the semiconductive zirconia sintering body at least partially forms a gripper.

Abstract: Fused, crystalline eutectic material comprising Al2O3-rare earth oxide-ZrO2 eutectic. Examples of useful articles comprising the fused eutectic material include fibers and abrasive particles.

Abstract: Rare-earth alloy is cast into a sheet (6) or the like by using a tundish (3, 13). The refractory material of the tundish used for casting does not necessitate preheating for improving the flowability of the melt (2). The refractory material used essentially consists of 70 wt % or more of Al2O3 and 30 wt % or less of SiO2, or 70 wt % or more of ZrO2 and 30 wt % or less of one or more of Y2O3, Ce2O3, CaO, MgO, Al2O3, TiO2 and SiO2. The refractory material has 1 g/cm3 or less of bulk density, has 0.5 kca/(mh° C.) or less of thermal conductivity in the temperature range of from 1200 to 1400° C., and has 0.5 wt % or less of ratio of ignition weight-loss under the heating condition of 1400° C. for 1 hour.

Abstract: Oxidized alumina-zirconia-silica (AZS) refractories containing 40 wt % to 55 wt % Al2O3, 32 wt % to 45 wt % ZrO2, 10 wt % to less than 16 wt % SiO2 and 1 wt % to 3 wt % of an alkali metal oxide selected from Na2O, K2O and mixtures thereof have a microstructure essentially comprising alpha-alumina crystals, free zirconia crystals, eutectic crystals and an intercrystalline vitreous phase. At least in an active area, more than 20% by number of the free zirconia crystals have a dendritic shape and are interleaved with each other and with eutectic crystals and at least 40% by number of the dendritic free zirconia crystals have a dimension greater than 300 &mgr;m.

Abstract: The electrolyte comprises up to about 80 wt % zirconia, up to about 30 wt % stabilizer, and up to about 40 wt % dopant-zirconia. Alternatively, the electrolyte can comprise zirconia having a phase chemistry, wherein the phase chemistry, at about 25° C., is about 15 wt % to about 35 wt % monoclinic, less than about 10 wt % tetragonal, balance cubic, based upon the weight of the zirconia in the electrolyte.

Abstract: A ceramic composite containing alkali-metal-&bgr;- or &bgr;″-alumina and an oxygen-ion conductor is fabricated by converting &agr;-alumina to alkali-metal-&bgr;- or &bgr;″-alumina. A ceramic composite with continuous phases of &agr;-alumina and the oxygen-ion conducting ceramic, such as zirconia, is exposed to a vapor containing an alkali-metal oxide, such as an oxide of sodium or potassium. Alkali metal ions diffuse through alkali-metal-&bgr;- or &bgr;″-alumina converted from &agr;-alumina and oxygen ions diffuse through the oxygen-ion conducting ceramic to a reaction front where &agr;-alumina is converted to alkali-metal-&bgr;- or &bgr;″-alumina. A stabilizer for alkali-metal-&bgr;″-alumina is preferably introduced into the &agr;-alumina/oxygen-ion conductor composite or introduced into the vapor used to convert the &agr;-alumina to an alkali-metal-&bgr;″-alumina.

Abstract: A powder of dicalcium silicate is made by spray drying calcia and silica with incorporation of sodium and phosphorus or stabilized zirconia. The spray dried powder is sintered to form a thermal spray powder. Sprayed coatings have a web of interconnected, randomly oriented microcracks substantially perpendicular to the coating surface. The coatings are stable in thermal cycling and a hot corrosive environment.

Abstract: Transparent solid, fused microspheres are provided. In one embodiment, the microspheres contain alumina, zirconia, and silica in a total content of at least about 70% by weight, based on the total weight of the solid, fused microspheres, wherein the total content of alumina and zirconia is greater than the content of silica, and further wherein the microspheres have an index of refraction of at least about 1.6 and are useful as lens elements.

Abstract: Fused cast AZS products that contain: Al2O3: 45-65 wt. %, ZrO2: 10.0-29.0 wt. %, SiO2: 20.0-24.0 wt. %, SiO2/(Na2O+K2O) weight ratio: 4.5-8, and other species: 0.5-4.0 wt. % These products may be produced from manufacturing waste or recycled spent materials.

Abstract: A re-usable alumina-magnesia graphite refractory suitably used for a refractory for continuous casting, such as a long nozzle used for pouring a molten metal from a ladle capable of re-use or intermittent use to a tundish, an immersion nozzle used for charging a molten metal from a tundish to a mold and a long stopper for controlling the flow rate of the molten steel; and produced by blending 3 to 60 wt % of magnesia having a particle size of 0.02 to 1.0 mm to a compound comprising mainly alumina and graphite, and kneading, molding, and baking the compound. The raw material compound comprising mainly alumina and graphite can contain spinel or zirconia.

Abstract: The invention relates to a sintered shaped body comprising a matrix material that contains an aluminum oxide/chromium oxide mixed crystal and an additional mixed crystal selected from at least one mixed crystal according to one of the general formulas La0.9Al11.76−xCrxO19, Me1Al11−xCrxO17, Me2Al12−xCrxO19, Me2′Al12−xCrxO19 and/or Me3Al11−xCrxO18, wherein Me1 stands for an alkali metal, Me2 represents an alkaline earth metal, Me2′ stands for cadmium, lead or mercury and Me3 represents a rare earth metal and x has a value ranging from 0.0007 to 0.045.

Abstract: The present invention relates to a porous aluminum oxide structure comprising Al2O3 and Zr, the structure having an open porosity greater than about 30% and an average pore size from about 20 nm to about 1000 nm, wherein the Zr, expressed as ZrO2, has a concentration less than about 5 weight % of the weight of the Al2O3.

Abstract: The present invention is to provide ceramic members for being used as members constituting a processing chamber for etching or cleaning semiconductor substrates or wafers by halogen plasma. A ceramic member includes at least 10% by volume of a compound of yttrium-aluminum-garnet (YAG) phase and not more than 90% by volume of at least an oxide phase selected from aluminum oxide, yttrium oxide and aluminum nitride. Particularly, the ceramic member contains yttrium within a range of 35 to 80 mole % in terms of yttrium oxide Y2O3 and aluminum within a range of 20 to 65 mole % in terms of aluminum oxide Al2O3 to form a mixture of YAG phase with yttria phase, producing ceramic material having high corrosion resistance to halogenous gas and its plasma. Such ceramic material may be well applicable to members to be exposed by the halogen plasma, for example, a chamber wall, a wafer stage, a clamp ring, a shower head, which are used in systems for etching and cleaning semiconductor wafers.

Abstract: The present invention relates to a porous aluminum oxide structure comprising Al2O3 and Zr, the structure having an open porosity greater than about 30% and an average pore size from about 20 nm to about 1000 nm, wherein the Zr, expressed as ZrO2, has a concentration less than about 5 weight % of the weight of the Al2O3.

Abstract: The present invention relates to a zirconia/alumina composite and a manufacturing method thereof which provide a zirconia ceramic powder having a composition in a triangle composition range formed of three composition points of 92 mol % ZrO2-4 mol % Y2O3-4 mol % Nb2O5 (or Ta2O5), 89 mol % ZrO2-7 mol % Y2O3-4 mol % Nb2O5 (or Ta2O5), 86 mol % ZrO2-7 mol % Y2O3-7 mol % Nb2O5 (or Ta2O5) in a ternary system of ZrO2—Y2O3—Nb2O5 or Ta2O3 for thereby manufacturing a zirconia/alumina composite having a high strength and high toughness in a state that a low temperature degradation does not occur.

Abstract: An optical connector member of the present invention is formed of a zirconia based ceramics which contain ZrO2 as a main component, 2-4 mol % of Y2O3, 0.05-1.0 wt % of A12O3, and 0.01 wt % or less each of siO2 and TiO2, then allowing the connector member to assure the durability even using in the high temperature and humidity circumstances. Also, An optical connector member is formed of a ceramic material having 0.1 wt % or less of a rate of change in weight while the material is held at a temperature of 85° C. and relative humidity of 85% for 2000 hours. For the ceramics, zirconia based ceramics are used to be partially stabilized with Y2O3 and with another stabilizer other than Y2O3. Further, the invention includes a ferrule having a through hole for holding an optical fiber therein, wherein the ferrule is provided, on its periphery, with a marker which indicates a direction of decentering the fiber on the top surface of the ferrule.

Abstract: The invention concerns a refractory material based on chromium corundum, a chromium corundum brick made of said material as well as the use thereof.

Abstract: Fused and cast AZS products, characterized in that they contain:

Abstract: A biomedical component comprising zirconia toughened alumina (ZTA), the ZTA comprising 1-69 wt % ZrO2, the ZrO2 being partially stabilized with >2.

Abstract: The invention provides a sintered, alumina ceramic product comprising about 90-97.5 w/w % Al2O3, about 0.5-1.0 w/w % MgO, about <0.05-1.0 w/w % SiO2, about 4.5-7.5 w/w % ZrO2 and about 0.07-0.13 w/w % HfO2.

Abstract: The present invention is milling media composed of ceramic particles having an average size of 0.1 to 20 mm. The ceramic particles contain a tetragonal zirconia core and a continuous shell on the core comprising cubic zirconia, monoclinic zirconia, spinel or zircon. The present invention is also a method of manufacturing the milling media which includes providing ceramic particles having an average size of 0.1 to 20 mm. The ceramic particles are tetragonal zirconia. The ceramic particles are coated with a clay material and sintered to form a shell of cubic zirconia, monoclinic zirconia, spinel or zircon over the tetragonal zirconia core.

Abstract: The composite oxide and the composite oxide carrier are manufactured by the precursor forming step and firing step. The composite oxide catalyst is obtained by preparing a composite of catalytic components simultaneously with the formation of the precursor of composite oxide in the step of forming the precursor of composite oxide. The composite oxide and the composite oxide carrier are composed of a composite oxide in which at least one of cerium and zirconium, and aluminium disperse with extremely high homogeneity. With this structure, the heat resistance of the carrier is improved and consequently, enlargement of particles of the composite oxide defining the carrier, and sintering of adjacent particles of the composite oxide can be restrained, whereby the catalyst using the composite oxide carrier in accordance with the present invention is excellent in heat resistance.

Abstract: Oxidized alumina-zirconia-silica (AZS) refractories containing 40 wt % to 55 wt % Al2O3, 32 wt % to 45 wt % ZrO2, 10 wt % to less than 16 wt % SiO2 and 1 wt % to 3 wt % of an alkali metal oxide selected from Na2O, K2O and mixtures thereof have a microstructure essentially comprising alpha-alumina crystals, free zirconia crystals, eutectic crystals and an intercrystalline vitreous phase. At least in an active area, more than 20% by number of the free zirconia crystals have a dendritic shape and are interleaved with each other and with eutectic crystals and at least 40% by number of the dendritic free zirconia crystals have a dimension greater than 300 &mgr;m.

Abstract: Disclosed is a taphole plugging composition for metal melting apparatus, the composition comprising (a) a refractory aggregate having a maximum particle size of 5 mm or less, (b) graphite and silicon nitride each having a maximum particle size of 0.2 mm or less, (c) a refractory clay, (d) a compatibilized binder mixture comprising a phenolic resin, a ketone compound and a pitch, and (e) an organic fine fiber.

Abstract: The invention provides a semiconductive zirconia sintering body able to be manufactured simply and cheaply and escape static electricity at suitable speed without greatly reducing mechanical characteristics of zirconia. 10 to 40 weight % of one kind or more of oxides of Fe, Co, Ni and Cr as conductivity giving agents is included with respect to 60 to 90 weight % of ZrO2 including a stabilizing agent so that a semiconductive zirconia sintering body having a volume specific resistance value from 105 to 109 &OHgr;·cm is formed.

Abstract: A high temperature cookware is made with material to render it heat more uniformly, at a lower temperature to avoid over-burning, more resistant to cracking due to sudden change in temperature, and less fragile. The material includes cordierite to possess small expansion coefficient, mullite to store more heat, talc to lower the firing temperature, and refractory clay for high heat conductivity. Other ingredients are added to enhance far-infrared radiation with certain kinds of metallic oxide. After the body is fired, the cookware is glazed to be impervious to water and coated with Teflon to make the cookware non-sticking.

Abstract: The present invention discloses novel magnesia-spinel refractory compositions and bricks formed thereof that exhibit longer lining life, greater hot strength and reduced tendency to spall under high thermal loading conditions. The invention is designed to slow or retard the reaction between spinel and lime through the addition of zirconia in the form of an alumina-zirconia grain to the refractory mix. Zirconia reacts more readily with the lime in the refractory composition and surrounding environment to form calcium zirconate.

Abstract: A composite mixture of spherical objects and lubricant useful for its cushioning properties is disclosed and claimed. The composite mixture may be composed of microspheres typically less than 2000 microns in diameter with inert atmospheres sealed within their interiors and any of a variety of lubricants facilitating sliding and rolling movement between microspheres. Typically the composite mixture includes lubricant in a quantity sufficient to substantially coat the exterior surface of essentially all of the spherical objects, but in a quantity less than would cause dispersion of the spherical objects in the lubricant sufficient to physically separate the spherical objects from each other and substantially reduce the sliding and rolling contact of the spherical objects with each other. The preferred lubricant is a visco-elastic fluid that has a principle molecule and a cross-linking agent.

Abstract: A powder of dicalcium silicate is made by spray drying calcia and silica with incorporation of sodium and phosphorus or stabilized zirconia. The spray dried powder is sintered to form a thermal spray powder. Sprayed coatings have a web of interconnected, randomly oriented microcracks substantially perpendicular to the coating surface. The coatings are stable in thermal cycling and a hot corrosive environment.

Abstract: Negative thermal expansion materials, methods of preparation and uses therefor are disclosed. The materials are useful for negative thermal expansion substrates, such as those used for optical fiber gratings.

Abstract: A fused-cast-alumina-zirconia-silica refractory consisting essentially of corundum crystals, baddeleyite crystals and a matrix glass phase and having a chemical composition comprising (a) from 30 to 70 wt % of Al.sub.2 O.sub.3, (b) from 20 to 59 wt % of ZrO.sub.2, (c) from 5 to 12 wt % of SiO.sub.2, (d) from 0.15 to 0.60 wt % of Na.sub.2 O, (e) from 0 to 0.50 wt % of K.sub.2 O, (f) from 0 to 0.40 wt % of Li.sub.2 O, (g) from 0.05 to 0.80 wt % of B.sub.2 O.sub.3, (h) from 0.05 to 0.80 wt % of P.sub.2 O.sub.5, and (i) from 0.05 to 0.50 wt % in total of at least one member selected from the group consisting of SnO.sub.2, ZnO, CuO and MnO.sub.2.

Abstract: Zirconia ceramic fibers, for catalytic applications, partially stabilized with yttria by means of a particular sol-gel process, are functionalized with a coating, containing zirconia and, optionally, alumina and/or oxides of Cu, Ni, Co, V, Mo, W, Ce, La, Nd and/or noble metals selected from Rh, Pt, Pd, Ru, Au, mainly obtained with a "dip coating" technique.

Abstract: The composite oxide and the composite oxide carrier are manufactured by the precursor forming step and firing step. The precursor forming step includes high speed mixing means. The composite oxide catalyst is obtained by preparing a composite of catalytic components simultaneously with the formation of the precursor of composite oxide in the step of forming the precursor of composite oxide. The composite oxide and the composite oxide carrier are composed of a composite oxide in which at least one of cerium and zirconium, and aluminium disperse with extremely high homogeneity. With this structure, the heat resistance of the carrier is improved and consequently, enlargement of particles of the composite oxide defining the carrier, and sintering of adjacent particles of the composite oxide can be restrained, whereby the catalyst using the composite oxide carrier in accordance with the present invention is excellent in heat resistance.

Abstract: The invention relates to a novel sintered material, characterized in that it is produced from a batch containing 5 to 40% zircon and in that it has the following chemical composition in % by weight:______________________________________ ZrO.sub.2 + HfO.sub.2 82-96 SiO.sub.2 1.7-14 TiO.sub.2 0.2-3 Y.sub.2 O.sub.3 0.4-5 Al.sub.2 O.sub.3 0.2-2.

Abstract: A ceramic composite containing alkali-metal-.beta.- or .beta."-alumina and an oxygen-ion conductor is fabricated by converting .alpha.-alumina to alkali-metal-.beta.- or .beta."-alumina. A ceramic composite with continuous phases of .alpha.-alumina and the oxygen-ion conducting ceramic, such as zirconia, is exposed to a vapor containing an alkali-metal oxide, such as an oxide of sodium or potassium. Alkali metal ions diffuse through alkali-metal-.beta.- or .beta."-alumina converted from .alpha.-alumina and oxygen ions diffuse through the oxygen-ion conducting ceramic to a reaction front where .alpha.-alumina is converted to alkali-metal-.beta.- or .beta."-alumina. A stabilizer for alkali-metal-.beta."-alumina is preferably introduced into the .alpha.-alumina/oxygen-ion conductor composite or introduced into the vapor used to convert the .alpha.-alumina to an alkali-metal-.beta."-alumina.

Abstract: An insulation material which is substantially free of fibers and which has a density of less than about 2.5 g/cc and a thermal conductivity of less than about 5 W/Km is formed from a composition comprising at least about 2%, by weight, carbon. The insulation material is resistant to thermal shock and is easily machined.

Abstract: The present invention provides a ceramic sintered body excellent in oxidation resistance under high temperatures and markedly superior to the conventional ceramic sintered body in the mechanical strength over a wide temperature range of between room temperature and 1,500.degree. C. The ceramic sintered body of the present invention comprises at least one ceramic crystal grain selected from the group consisting essentially of a monosilicate represented by the general formula RE.sub.2 SiO.sub.5, where RE denotes a IIIa group element including yttrium, and a disilicate represented by the general formula RE.sub.2 Si.sub.2 O.sub.7, where RE denotes a IIIa group element including yttrium, and at least one additional element selected from the group consisting of Al, Cr, Hf, Nb, Zr, Ti, V, Ta, Ca and Mg which is segregated in the boundaries of the ceramic crystal grains in an amount of 0.1 to 15% by weight of the sintered body in terms of the oxide thereof.

Abstract: A semiconductive ceramic composition having negative resistance-temperature characteristics, wherein the composition comprises lanthanum cobalt oxide as the primary component, and, as secondary components, at least one oxide of an element selected from B, Fe and Al and at least one oxide of an element selected from Si, Zr, Hf, Ta, Sn, Sb, W, Mo, Te, Ce, Nb, Mn, Th and P. A semiconductive ceramic composition having a resistivity of approximately 10 .OMEGA..multidot.cm to 100 .OMEGA..multidot.cm at room temperature is obtained by controlling the amount of additives. Since the resistivity at room temperature can be enhanced to several times or more that of the conventional compositions while characteristics of the conventional compositions are maintained, the composition may be widely applied to control heavy current.

Abstract: A novel zirconia sintered body is provided which contains Y.sub.2 O.sub.3 in a solid solution state, and has tetragonal crystal grains oriented at an orientation degree of not higher than 45%. A process for producing the zirconia sintered body is also provided. This zirconium sintered body deteriorates less, and excellent in stability of surface smoothness, and can be produced by a simple process.

Abstract: An improvement in a thermally insulating component for an engine part, made by sintering from ceramic materials, comprises, the thermally insulating component having a composition, consisting of a mixture of zirconium oxide in the range of about 5% to about 25% by volume and mullite in the range of about 75% to about 95% by volume. Further, the mixture of zirconium oxide and mullite is obtained by chemically mixing the zirconium oxide and mullite in their molecular states, rather than mechanically mixing them. Another feature of this invention includes, forming said thermally insulating component by slip casting and pressureless sintering the mixture of zirconium oxide and mullite at a temperature no greater than 1700.degree. C. This improvement in a thermally insulating component for an engine part, made from a mullite-zirconia ceramic composite, embodying the present invention, is particularly useful in making flame decks for cylinder heads, and insulating coverings for pistons and exhaust ports.

Abstract: A ceramic formed body containing a) 5 to 70 vol % of at least on intermetallic aluminide phase which additionally may contain aluminum or/and aluminum alloy, and b) 30 to 95 vol % of one or more ceramic phases which form a solid interconnecting skeleton and wherein the intermetallic phase or phases consist of predominantly interconnected areas with average sizes of 0.1 to 10 .mu.m, is obtained by sintering, in a non-oxidizing atmosphere, of a powder metallurgically green body which consists of a mixture of finely dispersed powder of aluminum, one or more ceramic substances and maybe further metals such that the mixture contains at least one oxide ceramic or/and metallic powder which, during sintering, reacts with aluminum thereby forming an aluminide and maybe Al.sub.2 O.sub.3.

Abstract: The present invention is ceramic article of stabilized zirconia wherein the stabilized zirconia has a molar ratio of rare earth oxide:zirconia of from 1:99 to 15:85, at a weight percent of from about 97 to 75. The ceramic article includes smectite clay from about 3 to 25 weight percent wherein the article is a mass of sintered particles having a continuous tetragonal phase having dispersed therein monoclinic phase particles having size of less than 100 nm.

Abstract: A ceramic composition is provided to insulate ceramic matrix composites under high temperature, high heat flux environments. The composite comprises a plurality of hollow oxide-based spheres of varios dimentions, a phosphate binder, and at least one oxide filler powder, whereby the phosphate binder partially fills gaps between the spheres and the filler powders. The spheres are situated in the phosphate binder and the filler powders such that each sphere is in contact with at least one other sphere. The spheres may be any combination of Mullite spheres, Alumina spheres, or stabilized Zirconia spheres. The filler powder may be any combination of Alumina, Mullite, Ceria, or Hafnia. Preferably, the phosphate binder is Aluminum Ortho-Phosphate. A method of manufacturing the ceramic insulating composition and its application to CMC substates are also provided.

Abstract: A zirconia diaphragm structure, and a method of producing such structure in which the zirconia diaphragm structure includes a zirconia substrate having at least one window, and a zirconia diaphragm plate formed integrally with the zirconia substrate so as to close each window, the zirconia substrate comprising a zirconia material as a major component, and containing 0.1-3.0% by weight of alumina, 0.1-3.0% by weight of silica, 0.1-5.0% by weight of alumina and silica, 0.1-5.0% by weight of alumina and magnesia, or 0.1-5.0% by weight of alumina, silica and magnesia.

Abstract: Disclosed are a ceramics sheet which has an area of 400 cm.sup.2 or more, thickness of 0.4 mm or less, maximum waviness height of 100 .mu.m or less, and warp of 0.1% or less and in which frequency of generated cracking and breakage is 10% or less when a load-applying test and a deflection-loading test each described in the text are carried out in succession, and a flat and large ceramics sheet having an area of 600 cm.sup.2 or more and thickness of 1 mm or less.

Abstract: A sintered ceramic body which can be worked by electrical discharge machining, has high mechanical strength, and can be worked into sintered ceramic tools which have long life is disclosed. Further, sintered ceramic tools which have long life and scarcely cause flaws in work pieces are provided. The sintered ceramic body comprises ceramic particles having specific particle diameter and particle distribution.