Alumina-based thermally conductive rounded-disc-shaped particles, production method for same, thermally conductive composition, article, liquid composition, thermally conductive thin film, and electronic device member

Alumina-based thermally conductive rounded disc-shaped particles being particles of an alumina-based thermally conductive oxide obtained by firing a raw material mixture comprising an aluminum raw material and a glass frit, the raw material mixture containing no boron compound,

• the aluminum raw material being at least one selected from the group consisting of boehmite and aluminum hydroxide,
• a deformation point of the glass frit being in a range from 300 degrees C. to 800 degrees C.,
• a content of the glass frit in the raw material mixture being in a range from 0.5 parts by mass to 5 parts by mass, to 100 parts by mass of the aluminum raw material, and
• primary particles of the alumina-based thermally conductive oxide having an average particle size in a range from 1 μm to 50 μm, having an average thickness in a range from 0.1 μm to 5 μm, having an aspect ratio of more than 1 and 50 or less, and having a rounded disc shape.