Toughening of alumina through dispersion of zirconia particles is strongly dependent on the grain size of both species and the quality of the dispersion. Attempts to improve the dispersion have been made using different powder synthesis or precursor routes: commercial alumina mixed with powdered zirconia obtained by flame decomposition of zirconium oxychloride, or mixed with zirconium acetate, coprecipitation of chlorides or alcoholates (alkoxides) of aluminium and zirconium. The precipitation processes are followed by a subsequent calcination step. A semimanual method of digitalization of the microstructure using a digital tablet and scanning electron microscope photographs is described. Different kinds of characterization of the microstructures are shown: ZrO2D50 vs. Al2O3D50, topological function and distance between ZrO2 particles compared with Al2O3 grain size, and the shape of the distribution itself. A plot of the zirconia mean grain size vs. alumina mean grain size for different zirconia contents exhibits very different behaviour according to the synthesis route. This can be explained by the different chemical composition of trace elements, giving a different influence on the grain growth and the coalescence of the two phases, but also to chemical mechanisms in conjunction with grain growth mechanisms under load. The final zirconia grain size appears to be small compared with the critical transformation size.