Abstract: A phosphorus-containing coated magnesium oxide powdered material comprising a coated magnesium oxide powdered material having a surface coating layer comprised of a double oxide, wherein the phosphorus-containing coated magnesium oxide powdered material has a coating layer comprised of a magnesium phosphate compound in at least part of a surface of the coated magnesium oxide powdered material, wherein the content of the magnesium phosphate compound in the coated magnesium oxide powdered material is 0.1 to 10% by mass, in terms of phosphorus; a method for producing a phosphorus-containing coated magnesium oxide powdered material, wherein the method comprises treating a coated magnesium oxide powdered material having a surface coating layer comprised of a double oxide with a phosphorus compound, and then calcining the resultant powdered material at 300° C.

Abstract: A phosphorus-containing coated magnesium oxide powdered material comprising a coated magnesium oxide powdered material having a surface coating layer comprised of a double oxide, wherein the phosphorus-containing coated magnesium oxide powdered material has a coating layer comprised of a magnesium phosphate compound in at least part of a surface of the coated magnesium oxide powdered material, wherein the content of the magnesium phosphate compound in the coated magnesium oxide powdered material is 0.1 to 10% by mass, in terms of phosphorus; a method for producing a phosphorus-containing coated magnesium oxide powdered material, wherein the method comprises treating a coated magnesium oxide powdered material having a surface coating layer comprised of a double oxide with a phosphorus compound, and then calcining the resultant powdered material at 300° C.

Abstract: Provided is a sphere-shaped coated magnesium oxide powder having a surface coated with a double oxide and having an average shape factor of 1.25 or less, wherein the powder is advantageous not only in that it has excellent humidity resistance, but also in that it has excellent filling property and excellent flowability when being used as filler for a resin. In addition, provided is a method for producing a sphere-shaped coated magnesium oxide powder, wherein the method comprises allowing a compound of an element forming a double oxide to be present on the surface of magnesium oxide powder, and then fusing the resultant magnesium oxide powder at a high temperature so that the surface of the magnesium oxide powder is coated with the double oxide and the magnesium oxide powder is shaped into sphere. Further, provided are a resin composition comprising the sphere-shaped coated magnesium oxide powder and an electronic device using the resin composition.

Abstract: An object of the present invention is to provide a magnesium oxide particle aggregate having a controlled particle aggregation structure so that the solid phase-solid phase reaction between magnesium oxide and the SiO2 film on the surface can be appropriately controlled. The object can be achieved by a magnesium oxide particle aggregate characterized in that a first inflection point diameter is 0.30×10−6 m or less, an interparticle void volume is 1.40×10−3 to 2.20×10−3 m3/kg and a particle void volume is 0.55×10−3 to 0.80×10−3 m3/kg in a cumulative intrusion volume curve of the particle aggregate.

Abstract: An object of the present invention is to provide a magnesium oxide particle aggregate having a controlled particle aggregation structure so that the solid phase-solid phase reaction between magnesium oxide and the SiO2 film on the surface can be appropriately controlled. The object can be achieved by a magnesium oxide particle aggregate characterized in that a first inflection point diameter is 0.30×10−6 m or less, an interparticle void volume is 1.40×10−3 to 2.20×10−3 m3/kg and a particle void volume is 0.55×10−3 to 0.80×10−3 m3/kg in a cumulative intrusion volume curve of the particle aggregate.