Abstract: Amorphous silica-titania composite oxide powder is powder untreated with a surface treatment agent and consisting of amorphous silica-titania composite oxide particles, wherein: a refractive index at a measurement wavelength of 589 nm is not less than 1.46; a volume-based cumulative 50% diameter is 0.1 ?m to 2.0 ?m; and a content of particles having a particle size of not less than 5.0 ?m is not more than 10 ppm, and wherein, in a case where the powder is dried in an atmospheric air at 110° C. for 12 hours, and powder thus dried is stored for 24 hours at a temperature of 25° C. and a relative humidity of 85% so as to absorb moisture, a water absorption rate is not more than 0.8% by mass as calculated from a mass X before moisture absorption and a mass Y after the moisture absorption in accordance with the formula: (Y?X)/X×100.

Abstract: A method for effectively removing minute impurities of 1 ?m or less in size that are present on a surface of an aluminum nitride single-crystal substrate without etching the surface includes scrubbing a surface of an aluminum nitride single-crystal substrate using a polymer compound material having lower hardness than an aluminum nitride single crystal, and an alkali aqueous solution having 0.01-1 mass % concentration of potassium hydroxide or sodium hydroxide, the alkali aqueous solution being absorbed in the polymer compound material.

Abstract: Amorphous silica-titania composite oxide powder is powder untreated with a surface treatment agent and consisting of amorphous silica-titania composite oxide particles, wherein: a refractive index at a measurement wavelength of 589 nm is not less than 1.46; a volume-based cumulative 50% diameter is 0.1 ?m to 2.0 ?m; and a content of particles having a particle size of not less than 5.0 ?m is not more than 10 ppm, and wherein, in a case where the powder is dried in an atmospheric air at 110° C. for 12 hours, and powder thus dried is stored for 24 hours at a temperature of 25° C. and a relative humidity of 85% so as to absorb moisture, a water absorption rate is not more than 0.8% by mass as calculated from a mass X before moisture absorption and a mass Y after the moisture absorption in accordance with the formula: (Y?X)/X×100.

Abstract: Provided are silicon fine particles that are effectively prevented from being oxidized and have a crystallite diameter close to that of an amorphous substance. The silicon fine particles of the present invention have an average diameter of primary particles of 30 to 900 nm, a crystallite diameter of less than 10 nm, a chlorine concentration of 1 to 10% by mass, and a ratio (Co/S) of an oxygen concentration (Co: % by mass) to a specific surface area (S: m2/g) of less than 0.05. The method for producing silicon fine particles of the present invention includes: heating a gas containing trichlorosilane to a temperature of 600 to 950° C. in a reactor and thermally decomposing the trichlorosilane to produce a silicon fine particle precursor containing chlorine, then collecting the silicon fine particle precursor, and then heating and dechlorinating the collected silicon fine particle precursor at a temperature of 750 to 900° C. under supply of an inert gas or under reduced pressure.

Abstract: A method for effectively removing minute impurities of 1 ?m or less in size that are present on a surface of an aluminum nitride single-crystal substrate without etching the surface includes scrubbing a surface of an aluminum nitride single-crystal substrate using a polymer compound material having lower hardness than an aluminum nitride single crystal, and an alkali aqueous solution having 0.01-1 mass % concentration of potassium hydroxide or sodium hydroxide, the alkali aqueous solution being absorbed in the polymer compound material.

Abstract: A method for effectively removing minute impurities of 1 ?m or less in size that are present on a surface of an aluminum nitride single-crystal substrate without etching the surface includes scrubbing a surface of an aluminum nitride single-crystal substrate using a polymer compound material having lower hardness than an aluminum nitride single crystal, and an alkali aqueous solution having 0.01-1 mass % concentration of potassium hydroxide or sodium hydroxide, the alkali aqueous solution being absorbed in the polymer compound material.

Abstract: A method for effectively removing minute impurities of 1 ?m or less in size that are present on a surface of an aluminum nitride single-crystal substrate without etching the surface includes scrubbing a surface of an aluminum nitride single-crystal substrate using a polymer compound material having lower hardness than an aluminum nitride single crystal, and an alkali aqueous solution having 0.01-1 mass % concentration of potassium hydroxide or sodium hydroxide, the alkali aqueous solution being absorbed in the polymer compound material.

Abstract: A single crystal of magnesium fluoride having a large diameter and excellent optical properties such as internal transmittance and long term laser durability, and suited for use as optical elements for exposing apparatus. The single crystal of magnesium fluoride is of a cylindrical shape having a straight body portion of a diameter of not smaller than 10 cm, has an internal transmittance of at least 85%/cm at 120 nm and at least 98%/cm at 193 nm and has, desirably, an induced absorption of not larger than 0.0030 absorption/cm at 255 nm and, particularly desirably, not larger than 0.0010 absorption/cm. at 255 nm immediately after the irradiation with 2 million shorts of an ArF excimer laser of an energy density of 30 mJ/cm2 and 2000 Hz. The invention further provides an optical element for optical lithography comprising the single crystal and an optical member for vacuum ultraviolet ray transmission comprising the single crystal.

Abstract: There is provided particulate silica which can be suitably used as a viscoelasticity modifier such as a thickener which is added to liquid such as water, a liquid resin or paint to adjust its viscoelastic properties such as viscosity and thixotropic nature, a reinforcer or filler for silicone rubber or sealants, a polishing agent for CMP (Chemical Mechanical Polishing) or a surface coating agent for ink-jet printing paper. The particulate silica has a BET specific surface area S of 130 to 380 m2/g, and its fractal shape parameter ?1 in an ?-value analysis target range of 20 to 30 nm satisfies the following equation (1) and its fractal shape parameter ?2 in an ?-value analysis target range of 30 to 50 nm satisfies the following equation (2). ?1+0.00175S<2.518??(1) ?2+0.00174S<2.

Abstract: There is provided particulate silica which can be suitably used as a viscoelasticity modifier such as a thickener which is added to liquid such as water, a liquid resin or paint to adjust its viscoelastic properties such as viscosity and thixotropic nature, a reinforcer or filler for silicone rubber or sealants, a polishing agent for CMP (Chemical Mechanical Polishing) or a surface coating agent for ink-jet printing paper. The particulate silica has a BET specific surface area S of 130 to 380 m2/g, and its fractal shape parameter ?1 in an ?-value analysis target range of 20 to 30 nm satisfies the following equation (1) and its fractal shape parameter ?2 in an ?-value analysis target range of 30 to 50 nm satisfies the following equation (2). ?1+0.00175S<2.518??(1) ?2+0.00174S<2.

Abstract: A sintered ceramics for mounting a light-emitting element, which is capable of realizing high optical reflectance over the entire region from ultraviolet radiation to visible light. The sintered ceramics has a light-reflective face of which reflectance to light in each wavelength in the range of 250 nm˜750 nm is 70% or more. The light-reflective face satisfies following reaction: |RA?RB|?20 when reflectance to light of 750 nm is defined as RA%, and reflectance to light of 300 nm is defined as RB. The sintered ceramics has not layer to be peeled from the light-reflective face when a Tape Peeling Test is carried out to the light-reflective face in accordance with the method described in JIS H8504 (1990).

Abstract: A non-oxide ceramics having improved performances and functions by forming a high-quality oxide film on the surface of a non-oxide ceramics such as aluminum nitride. The method for the formation of the non-oxide ceramics comprises the steps of: (1) providing a non-oxide ceramics; (2) introducing the non-oxide ceramics into a furnace and then regulating the atmosphere within the furnace so as to have an oxidizing gas content of not more than 0.5 mmol in terms of total number of moles of the oxidizing gas per m3 of the inside of the furnace; (3) heating the non-oxide ceramics to a temperature at or above a temperature, which is 300° C.