Plate-shaped alumina powder and its manufacturing method, as well as coatings or cosmetics

Abstract

This invention provides a plate-shaped alumina powder and its manufacturing method. Compared to conventional plate-shaped alumina powders, this powder can suppress a glossy appearance (sparkling effect) with a dotted distribution, even with the same particle size. The plate-shaped alumina powder is composed of a plurality of plate-shaped α-alumina particles. The average particle size, as determined by SEM observation, is 2 μm or more and 100 μm or less, and the average thickness, as determined by SEM observation, is 0.2 μm or more and 3.0 μm or less. Furthermore, the aforementioned plate-shaped α-alumina particles are polycrystalline, and the average value of the ratio (L2 / L1) of the total length (L2) of the grain boundaries of the aforementioned plate-shaped α-alumina particles to their perimeter is 0.30 or more and 2.00 or less.

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