The powder of the Zm compositions were prepared by depositing a layer of unstabilized zirconia on the surface of the alumina platelets by the alkoxide process route . The alumina platelets were first dispersed in absolute ethanol. A zirconia precursor solution (Zirconium(IV) propoxide, 70% in 1-propanol, Sigma-Arldrich) is diluted in absolute ethanol (66.7 vol% solution, 33.3% absolute ethanol). The resulting solution was added dropwise to the solution under stirring and containing the platelets. Once all the propoxide has been added, the solution (still under stirring) is heated to 70°C in order to evaporate the ethanol for about 8 hours and finally in the oven at 100°C for one night to remove all traces of ethanol. A paste was obtained, which was de-agglomerated and filtered with mortar and filtered with a coarse sieve. Finally, the powder was heat-treated at 850°C for 2 hours.