| 摘要 |
PURPOSE:To obtain alpha-alumina powder for a sintered compact having specified characteristics by adding seed crystals to transition alumina or an Al compd. forming transition alumina by firing and then firing them in atmospheric gas contg. >=1vol.% gaseous hydrogen halide. CONSTITUTION:Seed crystals are added to transition alumina or an Al compd. forming transition alumina by firing by 0.01-10wt.% and they are fired at 500-1,500 deg.C for >=1min in atmospheric gas contg. >=1vol.% gaseous hydrogen halide to obtain the objective alpha-alumina powder for a sintered compact having 0.1-5mum primary particle diameter. This alumina powder is made of particles having a polyhedral shape larger than an octahedral shape and such a particle size distribution that the ratio of the particle diameter D90 of cumulative 90% of the distribution from the fine particle side to the particle diameter D10 of cumulative 10% is <=10. The alumina powder has >=99.90wt.% purity of alumina, <=40wt.ppm iron content, <=40wt.ppm Ca content, slight flocculation and satisfactory crystallizability and it is uniform in particle shape and suitable for use as starting material for a sintered compact. |
