Calcined alumina, its production method and fine alpha-alumina powder obtained by using the calcined alumina

摘要

A calcined alumina, its production method and fine a alumina powder obtained by using the calcined alumina are described. The calcined alumina has the SET specific surface area of 10 to 20 m²/g, the main crystal phase of &agr; phase, a &thgr; phase not substantially contained, and the average particle size of 0.5 &mgr;m or less. The method for producing the calcined alumina comprising calcining an aluminum-containing substance containing substantially no metal element other than aluminum in an atmosphere having a partial pressure of water vapor of 600 Pa or less. The fine &agr;-alumina powder having a purity of 99.99% or more and a BET specific surface area of 15 m²/g or more, containing substantially no transition alumina, and providing, when calcined at 1250° C. under normal pressure, a sintered body having a relative density of 95% or more.