Abstract: An object of the present invention is to provide a compound with high catalytic activity that can be used as a catalyst for oxygen evolution reaction. Tungsten oxide represented by NixFe1-xWO4 (wherein 0<x<1). A catalyst for oxygen evolution reaction for use in an anodic electrode or a positive electrode, comprising the tungsten oxide. An electrolyzer comprising an anodic electrode chamber and a cathodic electrode chamber divided by an ion-permeable separating membrane, wherein an anodic electrode is arranged in the anodic electrode chamber and a cathodic electrode is arranged in the cathodic electrode chamber, and wherein the tungsten oxide represented by NixFe1-xWO4 (wherein 0<x<1) is supported on the anodic electrode as a catalyst.

Abstract: An aluminum nitride single crystal in the form of polygonal columns, the polygonal columns having the following properties [a] to [c]: [a] the content of a metal impurity is below a detection limit, [b] the average bottom area is from 5×103 to 2×105 ?m2, and [c] the average height is 50 ?m to 5 mm. The above aluminum nitride single crystal is preferably obtainable in a method including the steps of sublimating an aluminum nitride starting material (A) containing 0.1 to 30% by mass of a rare earth oxide by heating the starting material at a temperature of not lower than 2000° C., depositing aluminum nitride on a hexagonal single crystal substrate and thereby growing aluminum nitride single crystal in the shape of polygonal columns.

Abstract: [Problems] To provide a method of producing, easily and in a high yield, a reformed aluminum nitride sintered body having very excellent light transmission property which can be favorably used as a light-transmitting cover particularly for light sources having high luminous efficiencies. [Means for Solution] An aluminum nitride sintered body having a concentration of metal impurities excluding aluminum of not more than 150 ppm, an oxygen concentration of not more than 0.5% by weight and a relative density of not less than 95% is used as a starting material. The aluminum nitride sintered body is heat-treated in an oxidizing atmosphere in a temperature region of 1400 to 2000° C. to increase the oxygen concentration by not less than 0.03% by weight.

Abstract: Provided is an aluminum nitride sintered body with high optical transmissivity and which has a smooth surface in the unpolished condition after firing. The aluminum nitride sintered body has an oxygen concentration of 450 ppm or less, a concentration of impurity elements excluding oxygen, nitrogen, and aluminum of 350 ppm or less, and an average crystal grain diameter of between 2 ?m and 20 ?m, and also has an arithmetic mean surface height Ra of 1 ?m or less and a maximum height Rz of 10 ?m or less in the unpolished condition after firing.

Abstract: A GaN crystal multi-layer substrate having surfaces with various crystal orientations formed on a sapphire base substrate, such as a substrate whose principal surface is a <11-20> plane which is the a-plane, a <1-100> plane which is the m-plane, or a <11-22> plane having a low threading dislocation density and high crystal quality of a GaN crystal, and a production process therefor.

Abstract: Provided are a silicon melt contact member which is markedly improved in liquid repellency to a silicon melt, which can retain the liquid repellency permanently, and which is suitable for production of crystalline silicon; and a process for efficient production of crystalline silicon, particularly, spherical crystalline silicon having high crystallinity, by use of the silicon melt contact member. A silicon melt contact member having a porous sintered body layer present on its surface, preferably the sintered body layer being present on a substrate of a ceramic material such as aluminum nitride, wherein the porous sintered body layer consists essentially of silicon nitride, has a thickness of 10 to 500 ?m, and has, dispersed therein, many pores preferably having an average equivalent circle diameter of 1 to 25 ?m at a pore-occupying area ratio of 30 to 80%, the pores connecting to each other to form communicating holes having a depth of 5 ?m or more.

Abstract: Disclosed is a novel method wherein an aluminum nitride single crystal having good crystallinity is efficiently and easily manufactured. The method for produsing an aluminum nitride single crystal wherein nitrogen gas is circulated in the presence of a raw material gas generation source, which generates an aluminum gas or an aluminum oxide gas, and a carbon body, and then the aluminum nitride single crystal is grown under a heating condition; characterized in that, at least a part of the carbon body does not directly contact with the raw material gas generation source, at least a part of the raw material gas generation source does not directly contact with the carbon body, the raw material gas generation source and the carbon body are positioned to make a space in which a clearance between the raw material gas generation source, which does not contact with the carbon body, and the carbon body, which does not contact with the raw material gas generation source, is 0.

Abstract: A high-purity aluminum nitride sintered body is provided by efficiently removing oxides contained in a raw material powder in producing an aluminum nitride sintered body and preventing composite oxide produced by reaction of oxides contained in the raw material powder with a sintering aid from remaining in the aluminum nitride sintered body. The above sintered body is achieved by an aluminum nitride sintered body having a concentration of residual oxygen excluding attached oxygen of 350 ppm or less.

Abstract: A cement for bonding an arc tube body made of an aluminum nitride sintered body and an electrode support made of molybdenum achieves high gas tightness in the obtainable arc tube without impairing the excellent translucency of the aluminum nitride sintered body. The cement contains a molybdenum powder and an aluminum nitride powder, and the total amount of metalloid elements, rare-earth elements and metal elements (except the rare-earth elements and aluminum element) corresponding to the following conditions (1) and (2) is 300 ppm or less: (1) metal elements having a melting point of 2000° C. or lower, and (2) metal elements having an ion radius smaller than that of aluminum.

Abstract: The present invention provides an aluminum nitride single crystal forming polygonal columns, the polygonal columns having the following properties [a] to [c]: [a] the content of a metal impurity is below the detection limit, [b] the average bottom area is from 5×103 to 2×105 ?m2, and [c] the average height is 50 ?m to 5 mm. The above aluminum nitride single crystal forming polygonal columns is preferably obtainable by sublimating an aluminum nitride starting material (A) containing 0.1 to 30% by mass of a rare earth oxide by heating the starting material at a temperature of not lower than 2000° C., depositing aluminum nitride on a hexagonal single crystal substrate and thereby growing aluminum nitride single crystal in the shape of polygonal columns.

Abstract: A process for producing an aluminum nitride sintered body having improved light transmission properties includes the step of subjecting an ordinary aluminum nitride sintered body to thermal treatment in an inert atmosphere at a temperature of from 1300 to 1400° C. for at least 1 hr. A cover for light sources is produced by the process and includes a hollow aluminum nitride sintered body having a light transmittance in the visible light region of at least 87%, which body is obtainable by thermally treating a hollow aluminum nitride sintered body in an inert atmosphere at a temperature of 1300 to 1400° C. for at least 1 hr.

Abstract: [Problems] To provide a method of producing, easily and in a high yield, a reformed aluminum nitride sintered body having very excellent light transmission property which can be favorably used as a light-transmitting cover particularly for light sources having high luminous efficiencies. [Means for Solution] An aluminum nitride sintered body having a concentration of metal impurities excluding aluminum of not more than 150 ppm, an oxygen concentration of not more than 0.5% by weight and a relative density of not less than 95% is used as a starting material. The aluminum nitride sintered body is heat-treated in an oxidizing atmosphere in a temperature region of 1400 to 2000° C. to increase the oxygen concentration by not less than 0.03% by weight.

Abstract: A high-purity aluminum nitride sintered body is provided by efficiently removing oxides contained in a raw material powder in producing an aluminum nitride sintered body and preventing composite oxide produced by reaction of oxides contained in the raw material powder with a sintering aid from remaining in the aluminum nitride sintered body. The above sintered body is achieved by an aluminum nitride sintered body having a concentration of residual oxygen excluding attached oxygen of 350 ppm or less.

Abstract: A process for producing integrated bodies from an aluminum nitride sintered body and a high-melting point metal member includes the steps of: (I) forming an aluminum nitride porous layer on a planned joint surface of the aluminum nitride sintered body; and (II) causing a mixture paste including aluminum nitride and a high-melting point metal to be present between the aluminum nitride porous layer and a planned joint surface of the high-melting point metal member while impregnating the porous layer with the mixture paste, and sintering the aluminum nitride and high-melting point metal in the mixture paste.

Abstract: [Problem] It is an object to provide a joining method, whereby even ceramics having an extremely small dielectric loss factor such as aluminum nitride can be joined efficiently and tightly. [Means for Resolution] A method of joining ceramics of the present invention is a method of heating ceramics of the same kind or different kinds by inducing self-heating of the ceramics by electromagnetic wave irradiation and thereby joining the ceramics together, and includes preheating a surface to be joined of the ceramic by a heating means that includes an auxiliary heating means other than the self-heating.

Abstract: A cement for bonding an arc tube body made of an aluminum nitride sintered body and an electrode support made of molybdenum achieves high gas tightness in the obtainable arc tube without impairing the excellent translucency of the aluminum nitride sintered body. The cement contains a molybdenum powder and an aluminum nitride powder, and the total amount of metalloid elements, rare-earth elements and metal elements (except the rare-earth elements and aluminum element) corresponding to the following conditions (1) and (2) is 300 ppm or less: (1) metal elements having a melting point of 2000° C. or lower, and (2) metal elements having an ion radius smaller than that of aluminum.

Abstract: An aluminum nitride sintered body having resistance to plasma gas and high thermal conduction and having excellent optical properties. The aluminum nitride sintered body of the present invention is characterized in that the proportion of positrons which are annihilated within a period of 180 ps (picoseconds) in the aluminum nitride crystal, as determined in the defect analysis using a positron annihilation method, is not less than 90%, and the sintered body preferably has a thermal conductivity of not less than 200 W/mK.

Abstract: [Problem] It is an object to provide a joining method that enables to join aluminum nitride sinters together efficiently and tightly. [Means for solution] A method of joining an aluminum nitride sinter includes placing an inclusion including a sintering aid between a surface to be joined of one aluminum nitride sinter and a surface to be joined of the other aluminum nitride sinter, and heating the inclusion by electromagnetic wave irradiation, thereby joining the aluminum nitride sinters together.

Abstract: An aluminum nitride sinter includes aluminum nitride crystal grains and a grain boundary phase derived from a sintering aid. In any cross section in a surface region extending up to 100 ?m from the surface of the sinter, the proportion of the area of a grain boundary phase having a circumscribed circle diameter of 1 ?m or less to the total area of the grain boundary phase is at least 50%, and the average grain diameter of the aluminum nitride crystal grains is in the range of 3.0 to 7.0 ?m. This aluminum nitride sinter can be produced from an aluminum nitride slurry having a specific grain size distribution, an aluminum nitride green object having a specific submerged density, or an aluminum nitride degreased object having a specific pore diameter.

Abstract: Provided is an aluminum nitride sintered body with high optical transmissivity and which has a smooth surface in the unpolished condition after firing. The aluminum nitride sintered body has an oxygen concentration of 450 ppm or less, a concentration of impurity elements excluding oxygen, nitrogen, and aluminum of 350 ppm or less, and an average crystal grain diameter of between 2 ?m and 20 ?m, and also has an arithmetic mean surface height Ra of 1 ?m or less and a maximum height Rz of 10 ?m or less in the unpolished condition after firing.