A process for producing plate-like alumina particles with a high aspect
ratio is described. Nano-sized particles of an aluminium precursor
compound, optionally formed by milling, are mixed with a sufficient
volume fraction of a diluent and heat treated to form substantially
discrete plate-like alpha alumina particles dispersed in the diluent. A
mineraliser may be added to lower the effective melting point of the
system. Substantially discrete plate-like particles may be formed without
agitation when the heat treatment is conducted below the melting point of
the diluent.