The present invention relates to a light-transmitting ceramic sintered body which contains air voids having pore diameters of 1 μm or more but less than 5 μm at a density within the range of from 10 voids/mm.sup.3 to 4,000 voids/mm.sup.3 (inclusive), while having a closed porosity of from 0.01% by volume to 1.05% by volume (inclusive). With respect to this light-transmitting ceramic sintered body, a test piece having a thickness of 1.90 mm has an average transmittance of 70% or more in the visible spectrum wavelength range of 500-900 nm, and the test piece having a thickness of 1.90 mm has a sharpness of 60% or more at a comb width of 0.5 mm.

A cBN sintered material cutting tool includes a cutting tool body that is made of a sintered material including cubic boron nitride particles and a binder phase, in which: an average particle size of the cBN particles is 0.5 μm or less and a content ratio of the cBN particles in the sintered material is 35 vol % to 80 vol %; and the binder phase includes 1.0 vol % to 20 vol % of an Al compound, an average particle size of the Al compound present in the binder phase is 300 nm or less, and a value of a ratio (a value of S.sub.N/S.sub.O; area ratio) of a content S.sub.N of nitrogen (N) included in the Al compound to a content S.sub.O of oxygen (O) included in the Al compound is 1.1 to 5.

The sintered material includes a powder-derived material containing one or both of a nitride and an oxynitride, each of which contains at least one first metal element selected from the group consisting of group 4 elements, group 5 elements and group 6 elements in the periodic table, the rate y1/x1 of the atomic ratio y1 of non-metal element atoms in the powder-derived material to the atomic ratio x1 of metal element atoms therein is greater than 1, and the powder-derived material has a cubic structure.

A stacked structure includes a first structure formed of a composite sintered body that contains AlN and MgAl.sub.2O.sub.4 as main phases, and a second structure formed of a ceramic sintered body and stacked on and bonded to the first structure. A difference in linear thermal expansion coefficient between the first structure and the second structure is less than or equal to 0.3 ppm/K.

A nitride phosphor particle dispersion-type sialon ceramic of the present invention includes a matrix formed of a sialon-based compound; and at least one nitride phosphor which is dispersed in the matrix and contains a luminescence center element.

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.

A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.

A cBN sintered material cutting tool includes a cutting tool body that is made of a sintered material including cubic boron nitride particles and a binder phase, in which: an average particle size of the cBN particles is 0.5 m or less and a content ratio of the cBN particles in the sintered material is 35 vol % to 80 vol %; and the binder phase includes 1.0 vol % to 20 vol % of an Al compound, an average particle size of the Al compound present in the binder phase is 300 nm or less, and a value of a ratio (a value of S.sub.N/S.sub.O; area ratio) of a content S.sub.N of nitrogen (N) included in the Al compound to a content S.sub.O of oxygen (O) included in the Al compound is 1.1 to 5.

A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.

A tire stud according to the present invention is manufactured from ceramic, and thus has characteristics of causing the strength of ceramics to recover through crack healing while lowering residual stress by improving a sintering process. In addition, abrasion resistance is improved by further adding a sintering aid and an organic oxide during sintering, and thus friction with a road surface can always be maintained to be constant and life span can be greatly increased.