Patent ID: 8163266

Claim:
α-Alumina powder having a purity of at least 99.99% by weight, a specific surface area of from 0.1 to 2.0 m 2 /g, a relative density of from 55 to 90%, and a closed porosity of 4% or less, wherein in a weight-based particle size distribution obtained by a dry sieving test according to JIS K0069 (1992), an amount of particles having a particle size of less than 75 μm is 5% by weight or less; an amount of particles having a particle size exceeding 2.8 mm is 15% by weight or less; and at least one frequency maximum peak appears in a particle size range of 100 μm or more and to less than 850 μm, provided that a particle size is the largest mesh size of a standard sieve through which α-alumina powder particle cannot pass among the standard sieves according to JIS Z8801 (1987).