Polycrystalline, sintered abrasive granules based on amp;agr;-Al.sub. 2 O. sub.

摘要

The invention relates to polycrystalline, sintered abrasive granules based on &agr;-Al.sub.2 O.sub.3 with a density of 98% of the theoretical density of corundum, a Vickers hardness of 21 GPa and greater and a crystallite size of 0.05 to 1.3 micron, as well as abrasives made from these abrasive granules and the use of these abrasive granules for the production of ceramic, refractory products.P PThe polycrystalline, sintered abrasive granules based on &agr;-Al. sub.2 O. sub.3 are produced by &agr;-Al.sub.2 O.sub.3 crystal nuclei being added to a boehmite dispersion, the mixture of the boehmite dispersion and the crystal nuclei being acidified and gelled and the gel being dried, crushed, and sintered. In doing so, 0.5 to 35% by weight of &agr;-Al. sub.2 O.sub.3 crystal nuclei, relative to the sintered abrasive granules, is added and the mixture of the boehmite dispersion and of the crystal nuclei is refluxed, while the pH of the mixture is kept in a range of 2.5 to 3.5 by adding acid.