Effect of crystallite size of boehmite on sinterability of alumina ceramics

Alumina ceramics were prepared by heating gamma-Al2O3 powders obtained from boehmites with a variety of crystallite sizes to elucidate effect of the crystallinity on the sinterability of alumina derived from boehmite. Boehmite powders were prepared both by precipitation and by hydrothermal treatment of a commercial boehmite powder. The crystallite sizes of these boehmites were ranged from 0 (in a gel) through 2.9 to 24.4 nm while those of the gamma-Al2O3 powders formed by heating the boehmites at 600 degreesC for 1 h were 4.0. 4.6 and 8.0 nm, respectively. The powders were ground in a planetary mill to 1.4-1.5 mum and their sinterability was examined by forming them into pellets and heating at 1400-1600 degreesC for 3 h. The sinterability increased in the gamma-Al2O3 from boehmite of larger crystallite size. The difference in sinterability is suggested to originate in the difference in agglomeration hardness of fine boehmite particles. (C) 2003 Elsevier Science Ltd and Techna S.r.l. All rights reserved.